contro la cellulite [¿soprattutto per lulo¿ ]

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Citazione:Messaggio inserito da listanozze
Caro crack molto probabilmente il caldo di ha messo un pò di nervosismo addosso, inoltre vorrei sapere se fai palestra o se parli tanto per parlare in quanto un certo listanozze fa bodybuilding in modo costante e intenso da diversi anni e un pò le conosce certe cose.
Secondo te perchè tutti i bodybuilder concludono la fase di massa con una di definizione?
Comunque penso che qui molti ragazzi / ragazze vadano in palestra e possano chiedere al loro istruttore se nella fase di massa si ha anche un aumento, più o meno consistente di grasso corporeo.
Se tu non metti su nemmeno un etto di grasso significa che sei il tipico bodybuilder della domenica.



Questo è un discorso diverso da quello che ho fatto io. E' una cosa scontata che nelle fasi di massa pura si aumenti un po' anche il grasso.
Questo però non necessariamente significa diventare dei ciccioni,ma forse tu sei abituato a diventare un ciccione per poi scendere di peso...
Su un soggetto che pesa troppo poco è inevitabile che vi siano degli accumuli di grasso testardo,per questo è molto saggio aumentare un po' la massa muscolare e poi magari quel grassetto testardo sarà meno restio ad andare via.


Citazione:Messaggio inserito da listanozze
E' naturale che se si aumenta la massa magra aumenti anche il metabolismo basale e quindi in condizioni di riposo l'organismo necessiti di più calorie ma che cacchio centra con il dimagrimento?
Se una persona fa massa e poi ingurgita meno calorie la massa grassa cala ma anche la massa magra e si ha una diminuizione del metabolismo basale ed alla fine ci si ritrova con meno grasso e meno muscolo e allora che tiri su dei pesi da fare? Solo per fare della fatica inutile?




Questa è mentalità da bodybuilder della Domenica! E' inevitabile che nel perdere grasso vada via anche un po' di muscolo,la bravura sta nel minimizzare la perdita del tessuto magro e massimizzare quella del tessuto adiposo.
Capisco che per un incompetente come te sia una cosa impegnativa...


Citazione:Messaggio inserito da listanozze
Allora vai a correre con una giusta frequenza cardiaca che consumi praticamente solo grassi!

Non esiste alcun tipo di corsa che bruci soltanto grassi. Se vuoi ti posto le percentuali in cui si bruciano grassi e zuccheri a seconda dell'intensità...

Messaggio inserito da listanozze
il tuo è un circolo vizioso pazzesco ahaha!!
Ma poi una persona che vuole dimagrire come cacchi fa ad aumentare di massa!?!?!
Si sei proprio il bodybuilder della domenica!!!

Si può cercare di mantenerla la massa muscolare,ed il bodybuilding lo fa in buona misura. Sui novellini poi è molto più facile...

Messaggio inserito da listanozze
Cerca di fare palestra e poi parla invece di leggere stronzate chissà da quali fonti.

Le mie fonti sono medline e la mia esperienza,non so le tue...

Messaggio inserito da listanozze
Poi ti faccio un altro esempio:
Tu dici che l' attività anaerobica aumenta la massa magra. Stronzata.
Un certo tipo di attività anaerobica aumenta la massa magra in quanto se tu fai i 100 metri da velocista non aumenti un bel niente eppure è attività anaerobica.

In effetti i centometristi sono magri per antomasia.ma fammi il piacere!
Chiaro che poi se fai attività anaerobica seguendo certi criteri la massa possa aumentare in misura maggiore rispetto a sforzi che prevedano meno secondi sotto tensione.

Messaggio inserito da listanozze
Questa è una rapida spiegazione tra la differenza tra attività aerobica/anaerobica
IN PRESENZA DI OSSIGENO
(metabolismo aerobico)
Nei muscoli sono presenti gli zuccheri, possono arrivare i grassi attraverso la circolazione sanguigna. Quando zuccheri e grassi vengono a contatto con l'ossigeno trasportato dal sangue, bruciano producendo l'energia utile al metabolismo cellulare: l'effetto della combustione produce acqua ed anidride carbonica. Il metabolismo aerobico, ideale per consumare i grassi, è possibile alla sola condizione che il movimento delle fibre muscolari non sia intenso. E' il caso di attività di durata a bassa intensità come la camminata, la corsa lenta, la bicicletta, ecc. Attività nelle quali la frequenza cardiaca (n° di battiti per minuto) non sia superiore a: (220 meno l'età, moltiplicato per il 60/75 %). Dopo poco tempo d'attività sono utilizzati i grassi di deposito, transitati nei muscoli attraverso la circolazione del sangue.

Questa è l'attività fisica che provoca il DIMAGRIMENTO

Quando il lavoro muscolare è intenso o veloce, lo sfruttamento di ATP è maggiore e l'ossigeno non riesce a provocare la ricarica così velocemente.
Entra in funzione il secondo sistema metabolico per ottenere energia:

IN ASSENZA DI OSSIGENO
(metabolismo anaerobico)
In questa condizione il sangue non può penetrare nei tessuti muscolari in particolare perché la pressione occlude il transito arterioso. Il muscolo è isolato ed i grassi non possono essere bruciati.
Gli zuccheri presenti all'interno del muscolo si scindono ma senza la presenza dell'ossigeno non possono essere ossidati, solo ridotti ad Acido Lattico dopo avere ceduto una parte della loro energia.Questo è il metabolismo anaerobico lattacido.



Grazie della speigazione maestro del copia ed incolla.
Ti ho già spiegato come l'attività anaerobica diminuisca l'adipe,se sei di coccio non ne ho colpa.

 

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Metabolism 1994 Jul;43(7):814-8

Impact of exercise intensity on body fatness and skeletal muscle metabolism.

Tremblay A, Simoneau JA, Bouchard C

Physical Activity Sciences Laboratory, Laval University, Ste-Foy, Quebec, Canada.

The impact of two different modes of training on body fatness and skeletal muscle metabolism was investigated in young adults who were subjected to either a 20-week endurance-training (ET) program (eight men and nine women) or a 15-week high-intensity intermittent-training (HIIT) program (five men and five women). The mean estimated total energy cost of the ET program was 120.4 MJ, whereas the corresponding value for the HIIT program was 57.9 MJ. Despite its lower energy cost, the HIIT program induced a more pronounced reduction in subcutaneous adiposity compared with the ET program. When corrected for the energy cost of training, the decrease in the sum of six subcutaneous skinfolds induced by the HIIT program was ninefold greater than by the ET program. Muscle biopsies obtained in the vastus lateralis before and after training showed that both training programs increased similarly the level of the citric acid cycle enzymatic marker. On the other hand, the activity of muscle glycolytic enzymes was increased by the HIIT program, whereas a decrease was observed following the ET program. The enhancing effect of training on muscle 3-hydroxyacyl coenzyme A dehydrogenase (HADH) enzyme activity, a marker of the activity of beta-oxidation, was significantly greater after the HIIT program. In conclusion, these results reinforce the notion that for a given level of energy expenditure, vigorous exercise favors negative energy and lipid balance to a greater extent than exercise of low to moderate intensity. Moreover, the metabolic adaptations taking place in the skeletal muscle in response to the HIIT program appear to favor the process of lipid oxidation

 

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SCHEMINO DELLO STUDIO PRECEDENTE, RIEPILOGATIVO DEI I RISULTATI OTTENUTI CON UN PROTOCOLLO DI ESERCIZIO AD ALTA INTENSITA':

http://www.exrx.net/FatLoss/HIITvsET.html

 

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Eur J Appl Physiol Occup Physiol. 1987;56(5):516-21. Related Articles, Links


Effects of two high-intensity intermittent training programs interspaced by detraining on human skeletal muscle and performance.

Simoneau JA, Lortie G, Boulay MR, Marcotte M, Thibault MC, Bouchard C.

Physical Activity Sciences Laboratory, Laval University, Ste-Foy, Quebec, Canada.

The purpose of this study was to investigate the effects of repeated high-intensity intermittent training programs interspaced by detraining on human skeletal muscle and performances. First, nineteen subjects were submitted to a 15-week cycle ergometer training program which involved both continuous and high-intensity interval work patterns. Among these 19 subjects, six participated in a second 15-week training program after 7 weeks of detraining. Subjects were tested before and after each training program for maximal aerobic power and maximal short-term ergocycle performances of 10 and 90s. Muscle biopsy from the vastus lateralis before and after both training programs served for the determination of creatine kinase (CK), hexokinase, phosphofructokinase (PFK), lactate dehydrogenase (LDH), malate dehydrogenase, 3-hydroxyacyl-CoA dehydrogenase (HADH) and oxoglutarate dehydrogenase (OGDH) activities. The first training program induced significant increases in all performances and enzyme activities but not in CK. Seven weeks of detraining provoked significant decreases in maximal aerobic power and maximal 90s ergocycle performance. While the interruption of training had no effect on glycolytic enzyme markers (PFK and LDH), oxidative enzyme activities (HADH and OGDH) declined. These results suggest that a fairly long interruption in training has negligeable effects on glycolytic enzymes while a persistent training stimulus is required to maintain high oxidative enzyme levels in human skeletal muscle. The degree of adaptation observed after the second training program confirms that the magnitude of the adaptive response to exercise-training is limited.

PMID: 3653091 [PubMed - indexed for MEDLINE]

 

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Impact of high-intensity exercise on energy expenditure, lipid oxidation and body fatness

M Yoshioka1, E Doucet1,3, S St-Pierre1, N Alméras1, D Richard2, A Labrie2, J P Després3, C Bouchard4 and A Tremblay1

1Division of Kinesiology, Laval University, Ste-Foy, Québec, Canada

2Department of Physiology and Anatomy, Laval University, Ste-Foy, Québec, Canada

3Department of Food Science and Nutrition, Laval University, Ste-Foy, Québec, Canada

4Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, Louisiana, USA


Correspondence to: A Tremblay, Division of Kinesiology, Physical Activity Sciences Laboratory, Laval University, Ste-Foy, Québec, Canada G1K 7P4. E-mail: angelo.tremblay@kin.msp.ulaval.ca


Abstract

OBJECTIVE: Two studies were conducted to assess the potential of an increase in exercise intensity to alter energy and lipid metabolism and body fatness under conditions mimicking real life.

METHODS: Study 1 was based on the comparison of adiposity markers obtained in 352 male healthy adults who participated in the Québec Family Study who either regularly participated in high-intensity physical activities or did not. Study 2 was designed to determine the effects of high-intensity exercise on post-exercise post-prandial energy and lipid metabolism as well as the contribution of -adrenergic stimulation to such differences under a real-life setting.

RESULTS: Results from Study 1 showed that men who regularly take part in intense physical activities display lower fat percentage and subcutaneous adiposity than men who never perform such activities, and this was true even if the latter group reported a lower energy intake (917 kJ/day, P<0.05). In Study 2, the high-intensity exercise stimulus produced a greater post-exercise post-prandial oxygen consumption as well as fat oxidation than the resting session, an effect which disappeared with the addition of propranolol. In addition, the increase in post-prandial oxygen consumption observed after the high-intensity exercise session was also significantly greater than that promoted by the low-intensity exercise session.

CONCLUSION: These results suggest that high-intensity exercise favors a lesser body fat deposition which might be related to an increase in post-exercise energy metabolism that is mediated by -adrenergic stimulation.

International Journal of Obesity (2001) 25, 332-339

 

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Ma l'attività ad alta intensità (alias anaerobica) non faceva ingrassare, o al più non faceva scendere di un solo etto? []

 

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Effect of exercise intensity on skeletal muscle AMPK signaling in humans - Metabolism
Diabetes, Sept, 2003 by Zhi-Ping Chen, Terry J. Stephens, Sid Murthy, Benedict J. Canny, Mark Hargreaves, Lee A. Witters, Bruce E. Kemp, Glenn K. McConell

Save a personal copy of this article and quickly find it again with Furl.net. It's free! Save it.
AMP-activated protein kinase (AMPK) appears to be an important regulator of energy metabolism during skeletal muscle exercise (1,2). The AMPK isoforms [alpha]1 and [alpha]2 are expressed in skeletal muscle and are activated allosterically by increases in free AMP and by phosphorylation by an upstream kinase, AMPK kinase (1,3). Skeletal muscle AMPK kinase phosphorylation of the AMPK at Thr-172 is low at rest and increases during contraction (4-6), but the level of skeletal muscle AMPK kinase activity at rest and during exercise is not known.

Much of the support for AMPK's role in metabolic control has come from studies using the nucleoside intermediate 5-aminoimidazole-4-carboxyamide-ribonucleoside (AICAR), which is phosphorylated to form ZMP (AICA-ribotide) and activates AMPK (7). When AICAR is administered to rats in vivo or in vitro in pharmacological doses, it activates AMPK in skeletal muscle and increases glucose uptake and fat oxidation (8-10). However, during exercise, skeletal muscle glucose uptake and fat oxidation do not always change in parallel. For example, during exercise at the same absolute workload, prior exercise training reduces glucose uptake but increases fat oxidation (11). In addition, skeletal muscle glucose uptake increases with increasing exercise intensity (12,13), whereas fat oxidation increases with increasing exercise intensity up to ~65-70% V[O.sub.2] peak, but then decreases at higher exercise intensities (12,13). A number of human studies now suggest that the regulation of skeletal muscle AMPK [alpha]1 and [alpha]2 differs depending on the exercise intensity. AMPK [alpha]2 is activated during exercise at or above ~60% V[O.sub.2] peak (14-16), whereas AMPK [alpha]1 is only activated during intense sprint type exercise in humans (14-17) or during intense electrical stimulation in vitro in rat muscle (18).

Skeletal muscle fat oxidation depends on fatty acids being transported into the mitochondria via carnitine palmitoyltransferase 1 (CPT1), which is inhibited allosterically by malonyl-CoA (19). AMPK phosphorylates and inhibits acetyl-CoA carboxylase (ACC)-[beta] (5,20), the enzyme responsible for malonyl-CoA production. Treadmill exercise increases skeletal muscle AMPK activity and ACC[beta] phosphorylation and reduces ACCU[beta] activity and malonyl-CoA content in rats (5,21). In addition, activation of AMPK, by AICAR treatment, decreases ACC[beta] activity and malonyl-CoA levels as well as increases fat oxidation in the perfused rat hindlimb (9). ACC[beta] activity decreases during exercise in humans at and above 60% V[O.sub.2] peak (22), and decreases in malonyl-CoA are detected at intensities between 85 and 100% V[O.sub.2] peak but not at 60% V[O.sub.2] peak (22,23). We found that ACC[beta] phosphorylation by AMPK at Ser-221 (MRPSMS (221) GLHLVKR) was increased greatly during prolonged exercise at ~60% V[O.sub.2] peak in human skeletal muscle (16), consistent with the reduction in ACC[beta] activity observed at this intensity (22). Increased AMPK activity is not detected until ~60% V[O.sub.2] peak (14-16), making it uncertain whether AMPK is responsible for ACC[beta] phosphorylation and the increased fat oxidation accompanying low-intensity exercise (e.g., 40% V[O.sub.2] peak) (13). At high exercise intensities (80-100% V[O.sub.2] peak) (12,13), fat oxidation decreases despite both ACC[beta] activity (22) and malonyl-CoA levels decreasing (22,23), which otherwise would be expected to drive fat oxidation. The drugs metformin and rosiglitazone, which are widely used to treat type 2 diabetes, have recently been found to activate AMPK in skeletal muscle of rats (24,25), and metformin activates AMPK in people with type 2 diabetes (26). Because diet and exercise can reduce the risk of developing type 2 diabetes, considerable attention has been focused on the possible role of AMPK in these events. For these reasons, it was of interest to systematically examine the effect of low-, moderate-, and high-intensity exercise on AMPK signaling, including AMPK kinase activity and AMPK activity, ACC[beta] phosphorylation, and fat oxidation.

There is conflicting evidence on the role of nitric oxide (NO) in regulating glucose uptake into skeletal muscle during exercise (27-32). Nevertheless, AMPK is associated with neuronal NO synthase (nNOS) and phosphorylates it during exercise in human skeletal muscle (16,17). Furthermore, AMPK is reported to activate skeletal muscle glucose uptake via a NO synthase--dependent pathway (33). In this study, we examined nNOS[mu] phosphorylation in parallel with glucose uptake at varying exercise intensities.

RESEARCH DESIGN AND METHODS

Subjects. Eight healthy nonsmoking men provided informed written consent to participate in this study, which was approved by the Monash University Standing Committee for Research on Humans. The subjects' age, weight, and height were 28 [+ or -] 2 years, 63.9 [+ or-] 3.3 kg, and 179 [+ or -] 3 cm, respectively (means [+ or -] SE).

Experimental procedures

Preliminary testing. Peak pulmonary oxygen consumption during cycling (V[O.sub.2] peak) was determined using a graded exercise test to volitional exhaustion on a ergometer (Lode, Gronignen, the Netherlands) and averaged 3.08 [+ or -] 0.35 * l/min (47.9 [+ or -] 4.5 ml * [kg.sup.-1] * [min.sup.-1]). On a separate day, subjects completed a familiarization trial in which they cycled for 1 h, spending 20 min at each of three sequential workloads, calculated from the V[O.sub.2] peak test, to be equivalent to 40% (low intensity), 60% (medium intensity), and 80% (high intensity) of their V[O.sub.2] peak, respectively. At least 5 days later, the subjects undertook their experimental trial.

Experimental trial. Subjects (overnight fasted) reported to the laboratory in the morning having abstained from exercise, alcohol, and caffeine for 24 h. One catheter was inserted into an antecubital forearm vein for infusion of a glucose stable isotope tracer ([16,6-[sup.2]H]glucose; Cambridge Isotope Laboratories, Cambridge, MA) and another into the contralateral forearm for blood sampling. A blood sample was obtained; then a bolus of 41.2 [+ or -] 0.5 [micro]mol/kg of the tracer was administered before a 2-h pre-exercise constant infusion (0.58 [+ or -] 0.04 [micro]mol * [kg.sup.-1] * [min.sup.-1]), which was continued throughout exercise. The exercise protocol consisted of cycling for 1 h, spending 20 min at each of three sequential workloads: low intensity: 40 [+ or -] 2% V[O.sub.2] peak (75 [+ or -] 12 W); medium intensity: 59 [+ or -] 1% V[O.sub.2] peak (132 [+ or -] 19 W); high intensity: 79 [+ or -] 1% V[O.sub.2] peak (182 [+ or -] 25 W). All subjects completed the protocol. Expired air was sampled into Douglas bags for ~15 min at rest, and then the last 3 min of each 20-min workload. Heart rate was monitored throughout exercise using a heart rate monitor (Polar Favor, Oulu, Finland). Muscle was sampled from the vastus lateralis muscle under local anesthetic using the percutaneous needle biopsy technique, with suction, at rest, and immediately at the completion of each 20-min period of exercise at four separate sites (resting and low-intensity samples were obtained from one leg, and medium- and high-intensity samples were obtained from the other leg). The resting muscle sample was frozen in liquid nitrogen within 4 [+ or -] 0 s of inserting the needle, with the exercise samples frozen within 13 [+ or -] 2 s of the subject stopping exercise. A standard 60-s period was allowed for completion of the biopsy and taping of the area before resuming exercise.

Analyti

 

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Blood analysis. Plasma glucose and lactate were determined using an automated glucose oxidase and L-lactate oxidase method, respectively (YSI 2300 Stat; Yellow Springs Instruments, Yellow Springs, OH), plasma nonesterified fatty acids (NEFAs) by an enzymatic colorimetric procedure (NEFA-C test; Wako, Osaka, Japan), and plasma insulin using a human insulin--specific radioimmunoassay kit (Linco Research, St. Charles, MO). Glucose kinetics at rest and during exercise were estimated using a modified one-pool non-steady-state model, as proposed by Steele et al. (35), which has been validated by Radziuk et al. (36). We assumed 0.65 as the rapidly mixing portion of the glucose pool and estimated the apparent glucose space as 25% of body weight. Rates of plasma glucose appearance ([R.sub.a]) and disappearance ([R.sub.d]) were determined from the changes in percent enrichment of [6,[6-.sup.2]H]glucose and plasma glucose concentration. The muscles of the legs account for 80-85% of tracer-determined whole-body glucose uptake during exercise at 55-60% [Vo.sub.2max] and probably a greater proportion during more intense exercise (37). During exercise at 50% of [Vo.sub.2max] workload, >95% of tracer-determine glucose uptake is oxidized (37).

Muscle analysis. A portion (~20 mg) of each muscle sample was freeze-dried and then crushed to a powder with any visible connective tissue removed. Muscle glycogen was extracted by incubating the sample in HCl then NaOH and then analyzed for glucose units using an enzymatic fluorometric method (38). Muscle metabolites (ATP, creatine phosphate, creatine, and lactate) were extracted using the procedure of Harris et. al. (39) and analyzed using enzymatic fluorometric techniques (40). Free ADP and free AMP were calculated as outlined previously (17).

Approximately 70 mg of each frozen muscle biopsy sample (non-freeze-dried) was homogenized in buffer A (50 mmol/l Tris-HCl, pH 7.5, 1 mmol/l EDTA, 1 mmol/l EGTA, 1 mmol/l dithiothreitol, 50 mmol/l NaF, 5 mmol/l Na pyrophosphate, 10% glycerol, 1% Triton X-100, 10 [micro]g/ml trypsin inhibitor, 2 [micro]g/ml aprotinin, 1 mmol/l benzamidine, and 1 mmol/l phenylmethylsulfonyl fluoride). The homogenates were incubated with the AMPK [alpha]l or [alpha]2 antibody--bound protein A beads for 2 hat 4[degrees]C. Immunocomplexes were washed with PBS and suspended in 50 mmol/l Tris-HCl buffer (pH 7.5) for AMPK activity assay (41). The AMPK activities in the immune complexes were measured in either the presence or absence of 200 [micro]mol/l AMP. Activities were calculated as picomoles of phosphate incorporated into the SAMS peptide [ACC[alpha] (73-87)A (77)] per minute per milligram total protein subjected to immunoprecipitate.

AMPK kinase assays were performed using a two-step reaction with a maltose binding protein (MBP)-AMPK (1-312) fusion construct as substrate (42). The construct consists of the AMPK catalytic core, which is activated after phosphorylation on the activation loop Thr-172. First, the AMPK kimase buffer contained 20 mmol/l Tris-HCl, pH 7.5, 0.1% Tween-20, 10 mmol/l dithiothreitol, 8 mmol/l Mg[Cl.sub.2] with 0.4 mmol/l ATP, and 0.12 mmol/l AMP, and MBP-AMPK (1-312)(5 [micro]mol/l) in 19 [micro]l was incubated with 11 [micro]l of the muscle homogenate at 30[degrees]C for 30 min. Second, the MBP-AMPK (1-312) activity was determined using the AMPK SAMS peptide assay, and a 10-[micro]l aliquot of the AMPK kinase reaction was added to the peptide phosphorylation reaction to give a final volume of 40 [micro]l comprising 50 mmol/l HEPES, pH 7.5, 12 mmol/l Mg[Cl.sub.2], 5% glycerol, 0.05% Triton X-100 with 1 mmol/l dithiothreitol, 0.25 mmol/l [[[gamma]-.sup.32]P]ATP (500 cpm/pmol), 100 [micro]mol/l SAMS peptide, and 0.18 mmol/l AMP. After incubation for 10 min at 30[degrees]C, 30-[micro]l aliquots were applied to P81 papers as previously described (43) and activities (picomoles of phosphate transferred to the SAMS peptide per minute per milligram protein) were calculated. The AMPK kinase assay was characterized using crude extracts of rat muscle over the same activity range and was linear with time over 30 min. The background activity due to phosphorylation of the SAMS peptide in the absence of added MBP-AMPK (1-312) is subtracted from the activity because of the presence of the substrate (42). Using recombinant CaM kinase I kinase as a surrogate AMPK kinase, we have shown that recombinant MBP-AMPK (1-312) requires phosphorylation on Thr-172 for activity. The activity of MBP-AMP (1-312) is independent of AMP, and its phosphorylation by AMPK is independent of AMP (S.M. and B.E.K., unpublished data).

ACC[beta] and nNOS[mu] were affinity purified from muscle homogenates using monomeric Avidin agarose beads and 2',5'-ADP Sepharose beads, respectively. The ACC[beta] fraction was subjected to SDS-PAGE,and ACC[beta] was detected by immunoblotting with anti-phospho-ACC[alpha]-Ser-221 polyclonal antibody (17) and horseradish peroxidase--conjugated streptavidin (Amersham Biosciences U.K., Little Chalfont, U.K.). A monoclonal anti-phospho-ACC antibody (05-673) with the similar properties is now available from Upstate Biotechnology (Lake Placid, NY). The nNOS[mu] fraction was subjected to SDS PAGE, and nNOS[mu] was detected by immunoblotting with anti-phospho-nNOS-Ser-1451 polyclonal antibody (17) and human nNOS[mu] antibody (N31020; Transduction Laboratory, Lexington, KY). All data are expressed in quantitative densitometric arbitrary units.

Statistical analysis. Results were analyzed using one-way repeated-measures ANOVA using the SPSS statistical package. Specific differences were located using the least significant difference test. A significance level of P < 0.05 was set.

RESULTS

Oxygen consumption progressively increased (P < 0.05) with each workload (Table 1). Respiratory exchange ratio also increased (P < 0.05) progressively; however, respiratory exchange ratio was not significantly different between medium and high intensity. Carbohydrate oxidation progressively increased (P < 0.05) from resting through to high intensity. Fat oxidation increased (P < 0.05) from resting to low intensity, plateaued from low to medium intensity (P > 0.05), and decreased (P < 0.05) back to approximately resting levels during high intensity (Table 1).

NEFA concentration remained essentially unchanged from resting to low intensity, then decreased (P < 0.05) from low to medium/high intensity (Table 2). Plasma insulin concentration decreased (P < 0.05) from resting to low intensity and remained relatively constant between low and medium intensity, before decreasing further during high intensity (Table 2). Plasma lactate remained essentially unchanged from resting to low intensity but increased (P < 0.05) from low to medium to high intensity (Table 2). Plasma glucose concentration remained essentially constant throughout the exercise trial (Table 2). Glucose [R.sub.a], was not significantly increased during low intensity, but then increased (P < 0.05) during medium intensity and increased further during high intensity (Table 2). Glucose [R.sub.d] followed the same general trend as glucose [R.sub.a]--not increasing significantly during low intensity, but then increasing during medium intensity (P < 0.05) and increasing further during high intensity (P < 0.05) (Table 2).

The muscle metabolite results, summarized in Table 3, show no significant change (P > 0.05) in any measured muscle metabolite during exercise at low intensity compared with resting, but exercise resulted in a significant (P < 0.05) muscle energy imbalance at medium and high intensity. Exorcise during medium intensity resulted in significant reductions (P < 0.05) in muscle glycogen and creatine phosphate and increases in muscle lactate, free AMP, free ADP, free AMP/ATP ratio, and creatine compared with both resting and low intensity. Exercise duri

 

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There was substantial constitutive AMPK kinase activity at test (Fig. 1). AMPK kinase activity did not increase significantly from resting to low intensity and increased (P < 0.05) modestly (~1.5-fold) during medium intensity, plateauing during high intensity (Fig. 1). There was no significant increase in AMPK [alpha]l or [alpha]2 activities from resting to low intensity. AMPK [alpha]1 activity increased ~1.5-fold during exercise at medium intensity (P < 0.05) but remained relatively unchanged during high intensity (Fig. 2A). AMPK [alpha]2 activity increased (P < 0.05) by approximately fivefold during medium intensity and by approximately eightfold during high intensity compared with resting (Fig. 2B). A large progressive increase (P < 0.05) in phosphorylation of ACC[beta] at Ser-221 occurred as exercise intensity increased (Fig. 3). The fold increase (P < 0.05) in phosphorylation of ACC[beta] was ~3-, ~8-, and ~10-fold during exercise at low, medium, and high intensity, respectively, compared with resting. nNOS[mu] phosphorylation tended to increase from resting to low intensity, then increased significantly during medium intensity, and then increased (P < 0.05) further during high intensity. The significant increase in ACC[beta] phosphorylation from resting to low intensity accompanied the trend for an increase in calculated free AMP from 0.6 to 1.0 ([micro]mol/kg dry wt, Table 3), indicating that ACC[beta] phosphorylation was particularly sensitive to the energy demands of exercise.

[FIGURES 1-3 OMITTED]

DISCUSSION

Activation of AMPK depends on phosphorylation at the activation loop Thr-172 by an upstream AMPK kinase(s), and AMPK activity can be further stimulated allosterically by AMP. AMPK kinase activity has not previously been investigated directly in skeletal muscle, although phosphorylation of AMPK Thr-172 by AMPK kinase has been demonstrated in skeletal muscle during exercise (4-6). The results obtained in the present study indicate that there is substantial AMPK kinase activity at rest, in marked contrast to the low resting levels of AMPK activity in skeletal muscle. There was only a modest but significant increase in skeletal muscle AMPK kinase activity during exercise. The high level of AMPK kinase activity indicates that other factors are likely to be important at rest to maintain the AMPK in the inactive dephosphorylated state. Because AMPK kinase activity was measured in crude extracts, we cannot rule out the possibility that important allosteric regulators may have been diluted out.

It has been reported that AMP binding to AMPK makes it a better substrate for AMPK kinase, and this may explain the low level of AMPK activity in resting muscle despite the presence of high AMPK kinase constitutive activity (44). AMPK [alpha]1 activity mirrored the change in AMPK kinase activity at each workload, but, unlike AMPK kinase activity, AMPK [alpha]2 activity increased greatly during moderate exercise and then increased further during high-intensity exercise. The apparent increase in AMPK [alpha]2 activity from 60 to 80% V[O.sub.2] peak may reflect the fivefold increase in free AMP/ATP ratio from 60 to 80% V[O.sub.2] peak. Further, because there was only a small increase in AMPK kinase activity during exercise compared with AMPK [alpha]2 activity, it appears that the major regulation of AMPK [alpha]2 activity during exercise is at the level of AMPK [alpha]2 rather than AMPK kinase. It is not known whether the apparent increase in AMPK kinase activity during exercise was due to posttranslational modification. Allosteric control of AMPK kinase due to accumulation of AMP in the biopsy extract was considered a possibility based on the report that AMP directly activated partially purified AMPK kinase (45). However, we have tested AMP activation of partially purified AMPK kinase from skeletal muscle, heart muscle, kidney, and liver, and in no case was the AMPK kinase activity stimulated by AMP when MBP-AMP [alpha] (1-312) was used as a substrate (S.M. and B.E.K., unpublished data). It has recently been shown that AMPK phosphorylation at Thr-172 increases during in situ stimulations in rat gastrocnemius muscle (5). A correlation between AMPK activity and Thr-172 phosphorylation was also observed (5). Insufficient muscle biopsy material in the present study was available to correlate Thf-172 phosphorylation with AMPK activity; however, our results suggest that Thr-172 phosphorylation measurements are not a surrogate for direct AMPK kinase activity measurements.

The responsiveness of AMPK activity correlates inversely with the concentration of muscle glycogen (46). Contraction at a low or moderately reduced muscle glycogen content results in a greater level of activation of AMPK during contractions than when starting with a very high muscle glycogen in both rats (46) and humans (47). The progressive decrease in muscle glycogen content during exercise in the present study paralleled the progressive increase in AMPK [alpha]2 activity with increasing workload. The mechanism underlying the inverse relationship between muscle glycogen content and AMPK activation is not known. Addition of glycogen to purified rat liver AMPK does not alter its activity (S.M. and B.E.K., unpublished data) so that suppression of AMPK activation in the presence of high muscle glycogen is not a direct effect of glycogen but rather a consequence of other factors.

Importantly, ACC[beta] phosphorylation increased during exercise at 40% V[O.sub.2] peak (Fig. 3), despite no detectable in vitro increase in AMPK activity at this low intensity of exercise (Fig. 2). Previously we have shown that AMPK is associated with ACC[beta] in skeletal muscle (16). This suggests that ACC[beta] phosphorylation is an especially sensitive measure of in vivo AMPK signaling. Although the trend increase in the free AMP level from rest to 40% V[O.sub.2] peak was not statistically significant, the downstream ACC[beta] phosphorylation was. Similarly, low frequency stimulation in situ and low-intensity running in rats increases skeletal muscle ACC[beta] phosphorylation and decreases ACC[beta] activity without a detectable increase in stable AMPK activity (5). We interpret this as indicating that AMPK is very tightly coupled to the metabolic needs of contracting skeletal muscle.

There is evidence that factors other than malonyl-CoA are important in regulating the transport of fatty acids into the mitochondria during exercise in humans (13,22,23,48). The decrease in malonyl-CoA observed by others during exercise at [greater than or equal to] 85% V[O.sub.2] peak (22) would be expected to increase fat oxidation, but fat oxidation decreases during this intensity of exercise compared with lower intensities (12,13) (Table 1). The reduction in calculated fat oxidation during high-intensity exercise in the present study involving relatively untrained individuals was more exaggerated than previous studies using endurance-trained subjects (12,13). Free carnitine decreases with increases in exercise intensity in human skeletal muscle, and it has been suggested that the reduced free carnitine would impair CPT1 activity (13). In addition, there is evidence in humans that the reduction in muscle pH observed during intense exercise may inhibit CPT1 (49). It is also possible that there is a reduction in oxygen in some fibers as the exercise intensity increases resulting in reduced reliance on fat oxidation (50) and that the increased reliance on fast-twitch muscle fibers at high intensities of exercise reduces fat oxidation.

The pattern of response of skeletal muscle AMPK [alpha]2 activity and whole-body glucose uptake to increases in exercise intensity were more similar than that of AMPK [alpha]1 activity and glucose uptake, suggesting that AMPK [alpha]2 may be more directly coupled to glucose uptake than AMPK [alpha]1. It should be noted, however, that the d

 

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We have shown that nNOS[mu] is a target for phosphorylation by AMPK in human skeletal muscle (17). We found a significant increase in phosphorylation of nNOS[mu] at Ser-1451 immediately after maximal sprint exercise (17) but only modest effects during lower-intensity exercise at ~60% V[O.sub.2] peak (16). In the current study, nNOS[mu] phosphorylation was also quite variable between subjects and only achieved statistically significant increases at the highest levels of exercise intensity (Fig. 4). The pattern of response of nNOS[mu] phosphorylation and glucose uptake during exercise of increasing intensity was quite similar.

[FIGURE 4 OMITTED]

It is possible that some of the observed effects in the present study may have been due in part to the sequential nature of the protocol. However, the increases in glucose disposal (53) and AMPK [alpha]2 activity (54) during exercise were much greater than would be expected from the exercise duration alone, so they must have mainly been an effect of exercise intensity.

In summary, we have round that AMPK kinase is substantially active in resting human skeletal muscle and only modestly increased with exercise. Because AMPK [alpha]1 and [alpha]2 are essentially inactive at rest, these results are consistent with the idea that the increase in AMP during exercise acts allosterically on AMPK to make it more susceptible to phosphorylation at Thr-172 by AMPK kinase. The modest increase in AMPK kinase activity mirrored that of AMPK [alpha]1 activity in that they were both unchanged during exercise at 40% V[O.sub.2] peak and then increased to a similar extent during exercise at 60% V[O.sub.2] peak, with no further increase at 80% V[O.sub.2] peak. AMPK [alpha]2 activity exhibited a similar pattern to whole-body glucose use during exercise, with no changes during low-intensity exercise but progressive increases at the higher exercise intensities. Although not measured, it is likely that contracting skeletal muscle glucose uptake increased during low-intensity exercise. ACC[beta] phosphorylation increased during low-intensity exercise without a measurable increase in AMPK activity and progressively increased with increases in exercise intensity. We interpret these results as indicating that the increase in ACC[beta] phosphorylation during low-intensity exercise results from allosteric activation of AMPK by AMP.

TABLE 1
Whole-body fuel oxidation during rest and exercise at low, medium,
or high intensity
Resting

V[O.sub.2] (l/min) 0.32 [+ or -] 0.06
Respiratory exchange ratio 0.84 [+ or -] 0.02
Fat oxidation ([micro]mol *
[kg.sup.-1] * [min.sup.-1]) 4.9 [+ or -] 0.5
Carbohydrate oxidation ([micro]mol
* [kg.sup.-1] * [min.sup.-1]) 15.1 [+ or -] 3.5

Low intensity

V[O.sub.2] (l/min) 1.21 [+ or -] 0.13 *
Respiratory exchange ratio 0.92 [+ or -] 0.01 *
Fat oxidation ([micro]mol *
[kg.sup.-1] * [min.sup.-1]) 10.8 [+ or -] 2.1 *
Carbohydrate oxidation ([micro]mol
* [kg.sup.-1] * [min.sup.-1]) 88.9 [+ or -] 7.0 *

Medium intensity

V[O.sub.2] (l/min) 1.81 [+ or -] 0.21 * ([dagger])
Respiratory exchange ratio 0.95 [+ or -] 0.01 * ([dagger])
Fat oxidation ([micro]mol *
[kg.sup.-1] * [min.sup.-1]) 9.8 [+ or -] 2.6 *
Carbohydrate oxidation ([micro]mol
* [kg.sup.-1] * [min.sup.-1]) 155.4 [+ or -] 12.8 * ([dagger])

High intensity

V[O.sub.2] (l/min) 2.41 [+ or -] * ([dagger])
([double dagger])
Respiratory exchange ratio 0.99 [+ or -] * ([dagger])
Fat oxidation ([micro]mol * 3.2 [+ or -] 0.8 ([dagger])
[kg.sup.-1] * [min.sup.-1]) ([double dagger])
Carbohydrate oxidation ([micro]mol 243.1 [+ or -] 24.3 * ([dagger])
* [kg.sup.-1] * [min.sup.-1]) ([double dagger])

Data are means [+ or -] SE. * Different, from resting (P < 0.05),
0.05), ([dagger]) different from low intensity (P < 0.05),
and ([double dagger]) different from medium intensity (P <
0.05). n = 8.

TABLE 2
Plasma hormones, metabolites, and glucose kinetics during
rest, and exercise at low, medium, or high intensity

Resting

NEFAs (mmol/l) 0.55 [+ or -] 0.06
Insulin (pmol/l) 56.7 [+ or -] 4.2
Lactate (mmol/l) 1.1 [+ or -] 0.1
Glucose (mmol/l) 4.9 [+ or -] 0.1
Glucose [R.sub.a] ([micro]mol
* [kg.sup.-1] * [min.sup.-1]) 7.9 [+ or -] 0-8
Glucose [R.sub.d] ([micro]mol
* [kg.sup.-1] * [min.sup.-1]) 7.7 [+ or -] 0.7

Low intensity

NEFAs (mmol/l) 0.49 [+ or -] 0.06
Insulin (pmol/l) 49.3 [+ or -] 3.1 *
Lactate (mmol/l) 1.6 [+ or -] 0.2
Glucose (mmol/l) 5.0 [+ or -] 0.1
Glucose [R.sub.a] ([micro]mol
* [kg.sup.-1] * [min.sup.-1]) 12.1 [+ or -] 1.1
Glucose [R.sub.d] ([micro]mol
* [kg.sup.-1] * [min.sup.-1]) 9.9 [+ or -] 1.2

Medium intensity

NEFAs (mmol/l) 0.37 [+ or -] 0.04 * ([dagger])
Insulin (pmol/l) 47.1 [+ or -] 4.5 *
Lactate (mmol/l) 2.8 [+ or -] 0.5 *
Glucose (mmol/l) 5.1 [+ or -] 0.2
Glucose [R.sub.a] ([micro]mol
* [kg.sup.-1] * [min.sup.-1]) 19.5 [+ or -] 1.7 * ([dagger])
Glucose [R.sub.d] ([micro]mol
* [kg.sup.-1] * [min.sup.-1]) 18.9 [+ or -] 2.2 * ([dagger])

High intensity

NEFAs (mmol/l) 0.34 [+ or -] 0.04 ([dagger])
Insulin (pmol/l) 37.7 [+ or -] 3.9 * ([dagger])
([double dagger])
Lactate (mmol/l) 7.2 [+ or -] 0.9 ([dagger])
([double dagger])
Glucose (mmol/l) 5.5 [+ or -] 0.5
Glucose [R.sub.a] ([micro]mol 29.8 [+ or -] 4.9 * ([dagger])
* [kg.sup.-1] * [min.sup.-1]) ([double dagger])
Glucose [R.sub.d] ([micro]mol 26.5 [+ or -] 4.2 * ([dagger])
* [kg.sup.-1] * [min.sup.-1]) ([double dagger])

Data are means [+ or -] SE. * Different from resting (P < 0.05),
([dagger]) different from low intensity (P < 0.05), and ([double
dagger]) different fro medium intensity (P < 0.05). n = 8.

TABLE 3
Muscle metabolites during rest and exercise at low, medium,
or high intensity

Resting Low intensity

Glycogen (mmol/kg dry wt) 381.1 [+ or -] 57.0 339.3 [+ or -] 43.5
Lactate (mmol/kg dry wt) 2.9 [+ or -] 0.4 5.1 [+ or -] 0.9
ATP (mmol/kg dry wt) 22.4 [+ or -] 1.3 22.5 [+ or -] 1.5
Free ADP ([micro]mol/kg
dry wt) 108.9 [+ or -] 7.3 143.6 [+ or -] 16.0
Free AMP ([micro]mol/kg
dry wt) 0.6 [+ or -] 0.1 1.0 [+ or -] 0.2
Free AMP/ATP ratio 0.03 [+ or -] 0.00 0.04 [+ or -] 0.01
Creatine (mmol/kg dry wt) 36.9 [+ or -] 3.7 43.8 [+ or -] 4.9
Creatine phosphate
(mmol/kg dry wt) 77.6 [+ or -] 4.9 70.7 [+ or -] 4.2

Medium intensity

Glycogen (mmol/kg dry wt) 263.8 [+ or -] 52.5 * ([dagger])
Lactate (mmol/kg dry wt) 13.4 [+ or -] 4.4 * ([dagger])
ATP (mmol/kg dry wt) 22.4 [+ or -] 1.4
Free ADP ([micro]mol/kg
dry wt) 298.3 [+ or -] 84.1 * ([dagger])
Free AMP ([micro]mol/kg
dry wt) 5.8 [+ or -] 3.2 * ([dagger])
Free AMP/ATP ratio 0.22 [+ or -] 0.11 * ([dagger])
Creatine (mmol/kg dry wt) 66.5 [+ or

 

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This work was supported by grants from the National Health and Medical Research Council of Australia (NHMRC) (to G.K.M. and B.E.K.), the National Heart Foundation of Australia (to B.E.K.), Diabetes Australia (to G.K.M. and B.E.K.), and the National Institutes of Health (grant DK35712 to L.A.W.). B.E.K. is an NHMRC Fellow, and G.K.M. was an NHMRC Senior Research Officer during data collection.

The authors thank the subjects for taking part in this study and Dr. Rodney Snow for technical assistance.

REFERENCES

(1.) Winder WW: Energy-sensing and signaling by AMP-activated protein kinase in skeletal muscle. J Appl Physiol 91:1017-1028, 200l

(2.) Kemp BE, Mitchelhill KI, Stapleton D, Michell BJ, Chen ZP, Witters LA: Dealing with energy demand: the AMP-activated protein kinase. Trends Biochem Sci 24:22-25, 1999

(3.) Hawley SA, Davison M, Woods A, Davies SP, Beri RK, Carling D, Hardie DG: Characterization of the AMP-activated protein kinase kinase from rat liver and identification of threonine 172 as the major site at which it phosphorylates AMP-activated protein kinase. J Biol Chem 271:27879-27887, 1996

(4.) Nielsen JN, Mustard KJ, Graham DA, Yu H, MacDonald CS, Pilegaard H, Goodyear LJ, Hardie DG, Richter EA, Wojtaszewski JF: 5'-AMP-activated protein kinase activity and subunit expression in exercise-trained human skeletal muscle. J Appl Physiol 94:631 641, 2003

(5.) Park SH, Gammon SR, Knippers JD, Paulsen SR, Rubink DS, Winder WW: Phosphorylation-activity relationships of AMPK and acetyl-CoA carboxylase in muscle. J Appl Physiol 92:2475-2482, 2002

(6.) Wojtaszewski JF, Mourtzakis M, Hillig T, Saltin B, Pilegaard H: Dissociation of AMPK activity and ACCbeta phosphorylation in human muscle during prolonged exercise. Biochem Biophys Res Commun 298:309-316, 2002

(7.) Corton JM, Gillespie JG, Hawley SA, Hardie DG: 5-Aminoimidazole-4-carboxamide ribonucleoside: a specific method for activating AMP-activated protein kinase in intact cells? Eur J Biochem 229:558-565, 1995

(8.) Bergeron R, Russell RR 3rd, Young LH, Ren JM, Marcucci M, Lee A, Shulman GI: Effect of AMPK activation on muscle glucose metabolism in conscious rats. Am J Physiol 276:E938-1944, 1999

(9.) Merrill GF, Kurth EJ, Hardie DG, Winder WW: AICA riboside increases AMP-activated protein kinase, fatty acid oxidation, and glucose uptake in rat muscle. Am J Physiol 273:E1107-E1112, 1997

(10.) Hayashi T, Hirshman MF, Kurth EJ, Winder WW, Goodyear LJ: Evidence for 5' AMP-activated protein kinase mediation of the effect of muscle contraction on glucose transport. Diabetes 47:1369-1373, 1998

(11.) Mendenhall LA, Swanson SC, Habash DL, Coggan AR: Ten days of exercise training reduces glucose production and utilization during moderate-intensity exercise. Am J Physiol 266:E136-E143, 1994

(12.) Romijn JA, Coyle EF, Sidossis LS, Gastaldelli A, Horowitz JF, Endert E, Wolfe RR: Regulation of endogenous fat and carbohydrate metabolism in relation to exercise intensity and duration. Am J Physiol 265:E380-E391, 1993

(13.) van Loon LJ, Greenhaff PL, Constantin-Teodosiu D, Saris WH, Wagenmakers AJ: The effects of increasing exercise intensity on muscle fuel utilisation in humans. J Physiol 536:295-304, 2001

(14.) Fujii N, Hayashi T, Hirshman MF, Smith JT, Habinowski SA, Kaijser L, Mu J, Ljungqvist O, Birnbaum MJ, Witters LA, Thorell A, Goodyear LJ: Exercise induces isoform-specific increase in 5'AMP-activated protein kinase activity in human skeletal muscle. Biochem Biophys Res Commun 273: 1150-1155, 2000

(15.) Wojtaszewski JF, Nielsen P, Hansen BF, Richter EA, Kiens B: Isoform-specific and exercise intensity-dependent activation of 5'-AMP-activated protein kinase in human skeletal muscle. J Physiol 528:221-226, 2000

(16.) Stephens TJ, Chen ZP, Canny BJ, Michell BJ, Kemp BE, McConell GK: Progressive increase in human skeletal muscle AMPK[alpha]2 activity and ACC phosphorylation during exercise. Am J Physiol Endocrinol Metab 282:E688-E694, 2002

(17.) Chen ZP, McConell GK, Michell BJ, Snow RJ, Canny BJ, Kemp BE: AMPK signaling in contracting human skeletal muscle: acetyl-CoA carboxylase and NO synthase phosphorylation. Am J Physiol Endocrinol Metab 279:E1202 E1206, 2000

(18.) Hayashi T, Hirshman MF, Fujii N, Habinowski SA, Witters LA, Goodyear LJ: Metabolic stress and altered glucose transport: activation of AMP-activated protein kinase as a unifying coupling mechanism. Diabetes 49:527-531, 2000

(19.) Ruderman NB, Saha AK, Vavvas D, Witters LA: Malonyl-CoA, fuel sensing, and insulin resistance. Am J Physiol 276:E1-E18, 1999

(20.) Vavvas D, Apazidis A, Saha AK, Gamble J, Patel A, Kemp BE, Witters LA, Ruderman NB: Contraction induced changes in acetyl-CoA carboxylase and 5'-AMP-activated kinase in skeletal muscle. J Biol Chem 272:13255-13261, 1997

(21.) Winder WW, Hardie DG: Inactivation of acetyl-CoA carboxylase and activation of AMP-activated protein kinase in muscle during exercise. Am J Physiol 270:E299-E304, 1996

(22.) Dean D, Daugaard JR, Young ME, Saha A, Vavvas D, Asp S, Kiens B, Kim KH, Witters L, Richter EA, Ruderman N: Exercise diminishes the activity of acetyl-CoA carboxylase in human muscle. Diabetes 49:1295-1300, 2000

(23.) Odland LM, Howlett RA, Heigenhauser GJ, Hultman E, Spriet LL: Skeletal muscle malonyl-CoA content at the onset of exercise at varying power outputs in humans. Am J Physiol 274:E1080-E1085, 1998

(24.) Fryer LG, Parbu-Patel A, Carling D: The anti-diabetic drugs rosiglitazone and metformin stimulate AMP-activated protein kinase through distinct signaling pathways. J Biol Chem 277:25226-25232, 2002

(25.) Zhou G, Myers R, Li Y, Chen Y, Shen X, Fenyk-Melody J, Wu M, Ventre J, Doebber T, Fujii N, Musi N, Hirshman MF, Goodyear LJ, Moller DE: Role of AMP-activated protein kinase in mechanism of metformin action. J Clin Invest 108:1167-1174, 2001

(26.) Musi N, Hirshman MF, Nygren J, Svanfeldt M, Bavenholm P, Rooyackers O, Zhou G, Williamson JM, Ljunqvist O, Efendic S, Moller DE, Thorell A, Goodyear LJ: Metformin increases AMP-activated protein kinase activity in skeletal muscle of subjects with type 2 diabetes. Diabetes 51:2074-2081, 2002

(27.) Kingwell B, Formosa M, Muhlmann M, Bradley S, McConell G: Nitric oxide synthase inhibition reduces glucose uptake during exercise in individuals with type 2 diabetes more than in control subjects. Diabetes 51:2572-2580, 2002

(28.) Bradley SJ, Kingwell BA, McConell GK: Nitric oxide synthase inhibition reduces leg glucose uptake but not blood flow during dynamic exercise in humans. Diabetes 48:1815-1821, 1999

(29.) Balon TW, Nadler JL: Evidence that nitric oxide increases glucose transport in skeletal muscle. J Appl Physiol 82:359-363, 1997

(30.) Higaki Y, Hirshman MF, Fujii N, Goodyear LJ: Nitric oxide increases glucose uptake through a mechanism that is distinct from the insulin and contraction pathways in rat skeletal muscle. Diabetes 50:241-247, 2001

(31.) Etgen GJ Jr, Fryburg DA, Gibbs EM: Nitric oxide stimulates skeletal muscle glucose transport through a calcium/contraction- and phosphatidylinositol-3-kinase-independent pathway. Diabetes 46:1915-1919, 1997

(32.) Rottman J, Bracy D, Malabanan C, Yue Z, Clanton J, Wasserman D: Contrasting effects of exercise and NOS inhibition on tissue-specific fatty acid and glucose uptake in mice. Am J Physiol Endocrinol Metab 283:E116-E123, 2002

(33.) Fryer LG, Hajduch E, Rencurel F, Salt IP, Hundal HS, Hardie DG, Carling D: Activation of glucose transport by AMP activated protein kinase via stimulation of nitric oxide synthase. Diabetes 49:1978-1985, 2000

(34.) Peronnet F, Massicotte D: Table of nonprotein respiratory quotient: an update. Can J Sport Sci 16:23-29, 1991

(35.) Steele R, Wall JS, DeBodo RC, Altszuler N: Measurement of the size and turnover rate of body glucose pool by the isotope dilution method. Am J Physiol 187:15-24, 1956

(36.) Radzink J, Norwich KH, Vranic M

 

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Continued from page 5.

(42.) Hamilton SR, O'Donnell JB Jr, Hammet A, Stapleton D, Habinowski SA, Means AR, Kemp BE, Witters LA: AMP-activated protein kinase kinase: detection with recombinant AMPK alpha1 subunit. Biochem Biophys Res Commun 293:892-898, 2002

(43.) Pearson RBM, Mitchelhill KI, Kemp BE: Studies on protein kinase/ phosphatase specificity using synthetic peptides. In Protein Phosphorylation: A Practical Approach. Hardie GD, Ed. Oxford, U.K., Oxford University Press, 1993, p. 265-291

(44.) Davies SP, Helps NR, Cohen PT, Hardie DG: 5'-AMP inhibits dephosphorylation, as well as promoting phosphorylation, of the AMP-activated protein kinase: studies using bacterially expressed human protein phosphatase-2C alpha and native bovine protein phosphatase-2AC. FEBS Lett 377:421-425, 1995

(45.) Hawley SA, Selbert MA, Goldstein EG, Edelman AM, Carling D, Hardie DG: 5'-AMP activates the AMP-activated protein kinase cascade, and Ca2+/ calmodulin activates the calmodulin-dependent protein kinase I cascade, via three independent mechanisms. J Biol Chem 270:27186-27191, 1995

(46.) Derave W, Ai H, Ihlemann J, Witters LA, Kristiansen S, Richter EA, Ploug T: Dissociation of AMP-activated protein kinase activation and glucose transport in contracting slow-twitch muscle. Diabetes 49:1281-1287, 2000

(47.) Richter EA, MacDonald C, Kiens B, Hardie G, Wojtaszewski JFP: Dissociation of 5' AMP-activated protein kinase activity and glucose clearance in human skeletal muscle during exercise (Abstract). Diabetes 50 (Suppl. 2): A62, 2001

(48.) Odland LM, Heigenhauser GJ, Lopaschuk GD, Spriet LL: Human skeletal muscle malonyl-CoA at rest and during prolonged submaximal exercise. Am J Physiol 270:E541-E544, 1996

(49.) Starritt EC, Howlett RA, Heigenhauser GJ, Spriet LL: Sensitivity of CPT I to malonyl-CoA in trained and untrained human skeletal muscle. Am J Physiol Endocrinol Metab 278:E462-E468, 2000

(50.) Richardson RS, Newcomer SC, Noyszewski EA: Skeletal muscle intracellular PO(2) assessed by myoglobin desaturation: response to graded exercise. J Appl Physiol 91:2679-2685, 2001

(51.) Wahren J, Felig P, Ahlborg G, Jorfeldt L: Glucose metabolism during leg exercise in man. J Clin Invest 50:2715-2725, 1971

(52.) Ahlborg G, Felig P, Hagenfeldt L, Hendler R, Wahren J: Substrate turnover during prolonged exercise in man: splanchnic and leg metabolism of glucose, free fatty acids, and amino acids. J Clin Invest 53:1080-1090, 1974

(53.) Howlett K, Febbraio M, Hargreaves M: Glucose production during strenuous exercise in humans: role of epinephrine. Am J Physiol 276:E1130-E1135, 1999

(54.) Musi N, Fujii N, Hirshman MF, Ekberg I, Froberg S, Ljungqvist O, Thorell A, Goodyear LJ: AMP-activated protein kinase (AMPK) is activated in muscle of subjects with type 2 diabetes during exercise. Diabetes 50:921-927, 2001

Zhi-Ping Chen, (1) Terry J. Stephens, (2) Sid Murthy, (1) Benedict J. Canny, (2) Mark Hargreaves, (3) Lee A. Witters, (4) Bruce E. Kemp, (1) and Glenn K. McConell (2,5)

From the (1) St. Vincent's Institute of Medical Research, University of Melbourne, Fitzroy, Victoria, Australia; the (2) Department of Physiology, Monash University, Clayton, Victoria, Australia; the (3) School of Health Sciences, Deakin University, Burwood, Victoria, Australia; the (4) Department of Medicine and the Department of Biochemistry and Biological Sciences, Dartmouth Medical School and Dartmouth College, Hanover, New Hampshire; and the (5) Department of Physiology, University of Melbourne, Parkville, Victoria, Australia.

Address correspondence and reprint requests to Dr. Glenn McConell, Department of Physiology, The University of Melbourne, Parkville, Victoria, 3010, Australia. E-mail: mcconell(@unimelb.edu.au.

Received for publication 9 September 2002 and accepted in revised form 4 June 2003.

Z.-P.C. and T.J.S. contributed equally to this work.

L.A.W. holds stock in and serves on the scientific advisory board of Mercury Therapeutics.

ACC, acetyl-CoA carboxylase; AICAR, 5-aminoimidazole-4-carboxyamide-ribonucleoside; AMPK, AMP-activated protein kinase; CPTl, carnitine palmitoyltransferase 1; MBP, maltose binding protein; NEFA, nonesterified fatty acid; nNOS, neuronal nitric oxide synthase.

COPYRIGHT 2003 American Diabetes Association
COPYRIGHT 2003 Gale Group

 

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HIGH-INTENSITY INTERVAL TRAINING:

THE OPTIMAL PROTOCOL FOR FAT LOSS?

James Krieger

As exercise intensity increases, the proportion of fat utilized as an energy substrate decreases, while the proportion of carbohydrates utilized increases (5). The rate of fatty acid mobilization from adipose tissue also declines with increasing exercise intensity (5). This had led to the common recommendation that low- to moderate-intensity, long duration endurance exercise is the most beneficial for fat loss (15). However, this belief does not take into consideration what happens during the post-exercise recovery period; total daily energy expenditure is more important for fat loss than the predominant fuel utilized during exercise (5). This is supported by research showing no significant difference in body fat loss between high-intensity and low-intensity submaximal, continuous exercise when total energy expenditure per exercise session is equated (2,7,9). Research by Hickson et al (11) further supports the notion that the predominant fuel substrate used during exercise does not play a role in fat loss; rats engaged in a high-intensity sprint training protocol achieved significant reductions in body fat, despite the fact that sprint training relies almost completely on carbohydrates as a fuel source.

Some research suggests that high-intensity exercise is more beneficial for fat loss than low- and moderate-intensity exercise (3,18,23,24). Pacheco-Sanchez et al (18) found a more pronounced fat loss in rats that exercised at a high intensity as compared to rats that exercised at a low intensity, despite both groups performing an equivalent amount of work. Bryner et al (3) found a significant loss in body fat in a group that exercised at a high intensity of 80-90% of maximum heart rate, while no significant change in body fat was found in the lower intensity group which exercised at 60-70% of maximum heart rate; no significant difference in total work existed between groups. An epidemiological study (24) found that individuals who regularly engaged in high-intensity exercise had lower skinfold thicknesses and waist-to-hip ratios (WHRs) than individuals who participated in exercise of lower intensities. After a covariance analysis was performed to remove the effect of total energy expenditure on skinfolds and WHRs, a significant difference remained between people who performed high-intensity exercise and people who performed lower-intensity exercise.

Tremblay et al (23) performed the most notable study which demonstrates that high-intensity exercise, specifically intermittent, supramaximal exercise, is the most optimal for fat loss. Subjects engaged in either an endurance training (ET) program for 20 weeks or a high-intensity intermittent-training (HIIT) program for 15 weeks. The mean estimated energy cost of the ET protocol was 120.4 MJ, while the mean estimated energy cost of the HIIT protocol was 57.9 MJ. The decrease in six subcutaneous skinfolds tended to be greater in the HIIT group than the ET group, despite the dramatically lower energy cost of training. When expressed on a per MJ basis, the HIIT group's reduction in skinfolds was nine times greater than the ET group.

A number of explanations exist for the greater amounts of fat loss achieved by HIIT. First, a large body of evidence shows that high-intensity protocols, notably intermittent protocols, result in significantly greater post-exercise energy expenditure and fat utilization than low- or moderate-intensity protocols (1,4,8,14,19,21,25). Other research has found significantly elevated blood free-fatty-acid (FFA) concentrations or increased utilization of fat during recovery from resistance training (which is a form of HIIT) (16,17). Rasmussen et al (20) found higher exercise intensity resulted in greater acetyl-CoA carboxylase (ACC) inactivation, which would result in greater FFA oxidation after exercise since ACC is an inhibitor of FFA oxidation. Tremblay et al (23) found HIIT to significantly increase muscle 3-hydroxyacyl coenzyme A dehydrogenase activity (a marker of the activity of b oxidation) over ET. Finally, a number of studies have found high-intensity exercise to suppress appetite more than lower intensities (6,12,13,22) and reduce saturated fat intake (3).

Overall, the evidence suggests that HIIT is the most efficient method for achieving fat loss. However, HIIT carries a greater risk of injury and is physically and psychologically demanding (10), making low- and moderate-intensity, continuous exercise the best choice for individuals that are unmotivated or contraindicated for high-intensity exercise.

1. Bahr, R., and O.M. Sejersted. Effect of intensity of exercise on excess postexercise O2 consumption. Metabolism. 40:836-841, 1991.

2. Ballor, D.L., J.P. McCarthy, and E.J. Wilterdink. Exercise intensity does not affect the composition of diet- and exercise-induced body mass loss. Am. J. Clin. Nutr. 51:142-146, 1990.

3. Bryner, R.W., R.C. Toffle, I.H. Ullrish, and R.A. Yeater. The effects of exercise intensity on body composition, weight loss, and dietary composition in women. J. Am. Col. Nutr. 16:68-73, 1997.

4. Burleson, Jr, M.A., H.S. O'Bryant, M.H. Stone, M.A. Collins, and T. Triplett-McBride. Effect of weight training exercise and treadmill exercise on post-exercise oxygen consumption. Med. Sci. Sports Exerc. 30:518-522, 1998.

5. Coyle, E.H. Fat Metabolism During Exercise. [Online] Gatorade Sports Science Institute. http://www.gssiweb.com/references/s...020000006d.html [1999, Mar 25]

6. Dickson-Parnell, B.E., and A. Zeichner. Effects of a short-term exercise program on caloric consumption. Health Psychol. 4:437-448, 1985.

7. Gaesser, G.A., and R.G. Rich. Effects of high- and low-intensity exercise training on aerobic capacity and blood lipids. Med. Sci. Sports Exerc. 16:269-274, 1984.

8. Gillette, C.A., R.C. Bullough, and C.L. Melby. Postexercise energy expenditure in response to acute aerobic or resistive exercise. Int. J. Sports Nutr. 4:347-360, 1994.

9. Grediagin, M.A., M. Cody, J. Rupp, D. Benardot, and R. Shern. Exercise intensity does not effect body composition change in untrained, moderately overfat women. J. Am. Diet Assoc. 95:661-665, 1995.

10. Grubbs, L. The critical role of exercise in weight control. Nurse Pract. 18(4):20,22,25-26,29, 1993.

11. Hickson, R.C., W.W. Heusner, W.D. Van Huss, D.E. Jackson, D.A. Anderson, D.A. Jones, and A.T. Psaledas. Effects of Dianabol and high-intensity sprint training on body composition of rats. Med. Sci. Sports. 8:191-195, 1976.

12. Imbeault, P., S. Saint-Pierre, N. Alméras, and A. Tremblay. Acute effects of exercise on energy intake and feeding behaviour. Br. J. Nutr. 77:511-521, 1997.

13. Katch, F.I., R. Martin, and J. Martin. Effects of exercise intensity on food consumption in the male rat. Am J. Clin. Nutr. 32:1401-1407, 1979.

14. Laforgia, J. R.T. Withers, N.J. Shipp, and C.J. Gore. Comparison of energy expenditure elevations after submaximal and supramaximal running. J. Appl. Physiol. 82:661-666, 1997.

15. Mahler, D.A., V.F. Froelicher, N.H. Miller, and T.D. York. ACSM's Guidelines for Exercise Testing and Prescription, edited by W.L. Kenney, R.H. Humphrey, and C.X. Bryant. Media, PA: Williams and Wilkins, 1995, chapt. 10, p. 218-219.

16. McMillan, J.L., M.H. Stone, J. Sartin, R. Keith, D. Marple, Lt. C. Brown, and R.D. Lewis. 20-hour physiological responses to a single weight-training session. J. Strength Cond. Res. 7(3):9-21, 1993.

17. Melby, C., C. Scholl, G. Edwards, and R. Bullough. Effect of acute resistance exercise on postexercise energy expenditure and resting metabolic rate. J. Appl. Physiol. 75:1847-1853, 1993.

18. Pacheco-Sanchez, M., and K.K Grunewald. Body fat deposition: effects of dietary fat and two exercise protocols. J. Am. Col. Nutr. 13:601-607, 1994.

19. Phelain, J.F., E. Reinke, M.A. Harris, and C.L. Melby. Poste

 

[harlequin]

crack poi proprio te parli di maestria nel copia-incolla???
hai inquinato il mio 3d sulla cellulite !!!
uffa

 

[crack]

Secondo me non capisci l'italiano liste nozze...
Io non ho inquinato nulla,questi sono studi in cui viene mostrata l'idoneità dell'attività ad alta intensità per perdere grasso,perdedone persino di più che con l'attività a bassa intensità.
Se le cose si vogliono leggere ci sono,altrimenti si può continuare a leggere Topolino e a dare del bodybuilder della Domenica agli altri...
L'aumentare o meno il grasso dipende dalla quantità di calorie superiore a quella necessaria.
Se la dieta è ipocalorica si dimagrisce,e l'attività ad alta intensità è idonea allo scopo,proprio quel tipo di attività che seondo te non lo sarebbe...
Comunque lascia il Topolino e leggi di più la bibliografia scientifica,invece che attaccare quattro cose che hai letto magari su una rivistuccia per donne sul metabolismo aerobico...
Parli di stronzate,pensa alle fesserie che dici tu chè io dalla mia parte o gli studi scientifici,non Donna Moderna come te...

 

[harlequin]

ma qui si parla di lotta contro la cellulite !!!!

 

[crack]

Citazione:Messaggio inserito da harlequin
ma qui si parla di lotta contro la cellulite !!!!


E secondo te la cellulite non diminuisce se si riesce a diminuire l'adipe?...

 

[giu]

Crack...che papiro!! già in italiano nn lo avrei mai letto...figurarsi in inglese!

cmq qui si esula dalla cellulite...che è un'edema e nn c'entra con grasso e muscoli (o cmq nn direttamente)

X listanozze e crack: ma la vostra è semplice cultura personale?

X listanozze: buona in che senso?
cruda so di carne cruda, cotta so di carne cotta.. Ah ah che battuta!

 

[crack]

Io in palestra vado,sei tu che dovresti leggere maggiormente forse...
Posto questo saremo d'accordo,penso,che è il deficit calorico che fa dimagrire.
Qualunque attività fisica può andare bene,purchè si abbia appunto un deficit calorico.
Quello che attestano gli studi è che si può perdere più grasso ancora se si associa ad una dieta una attività ad alta intensità.
Questo non significa che io sia contro l'attività a bassa intensità,che può essere certamente utile.
Solo che l'attività aerobica è molto catabolica anche per il tessuto proteico,quindi il rischio è di bruciare troppa massa muscolare rispetto all'adipe,e quindi di non riuscire ad intaccare quei depositi testardi sui fianchi o sul sedere.
Se fai bodybuilding ad un certo livello,non penso che in definizione abbandoni i pesi e ti dedichi solo a delle interminabili maratone aerobiche...
Perchè? Perchè l'aerobica è molto catabolica,e quindi si rischia di avere quell'aspetto da ebreo deportato che sembra tanto in voga nelle piste di atletica. Sfido chiunque a dire che quell'aspetto emaciato sia bello a vedersi...

 

[crack]

La cellulite non è solo edema.
L'edema è sia causa che effetto, ovvero si manifesta con l'edema ma lo stesso edema, e quindi la stasi di liquidi, la alimenta e fornisce i substrati(grasso, calcio e rame) che poi la sclerotizzano e alterano anche la struttura del grasso che si presenta molto poco vascolarizzato e metabolicamente inibito.
Chiaramente esistono anche soggetti magri con la cellulite,non è la scoperta dell'uovo di colombo.
Tuttavia combinando dieta e allenamento si può comunque migliorare la cosa,ed ho visto io stesso sulla mia ragazza che facendo pesi insieme ad una dieta ipocalorica la sua cellulite è parecchio migliorata.
Ora la sto facendo dedicare ad un allenamento di interval training,e devo dire che il suo aspetto sta continuando a migliorare notevolmente.
Certo anche l'attività a bassa intensità ha una valenza,ma dire che solo questa fa diminuire l'adipe è una cosa errata.