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La tension, plus que le temps sous tension déclenche l’anabolisme

23/05/2015 | Etudes Musculation

 

High force development augments skeletal muscle signalling in resistance exercise modes equalized for time under tension
Sebastian Gehlert     Pflügers Archiv - European Journal of Physiology June 2015, Volume 467, Issue 6, pp 1343-1356

How force development and time under tension (TUT) during resistance exercise (RE) influence anabolic signalling of skeletal muscle is incompletely understood. We hypothesized that high force development during RE is more important for post-exercise-induced signalling than submaximal and fatiguing RE with lower force development but similar TUT.

Twenty-two male subjects (24 ± 6 years, 181 ± 9 cm, 79 ± 2 kg) performed three distinct RE modes in the fed state with equal TUT but distinct force output:
(i) maximal eccentric RE (ECC, n = 7) three sets, eight reps, 100 % eccentric dynamic force;
(ii) standard RE (STD, n = 7), three sets, 10 reps, 75 % dynamic force; and
(iii) high fatiguing single-set RE (HIT, n = 8), 20 reps, 100 % eccentric-concentric force;

vastus lateralis biopsies were collected at baseline, 15, 30, 60, 240 min and 24 h after RE, and the signalling of mechanosensitive and mammalian target of rapamycin (mTOR)-related proteins was determined.

The phosphorylation levels of pFAKTyr397, pJNKThr183/Tyr185, pAKTThr308/Ser473, pmTORSer2448, p4E-BP1Thr37/46, p70s6kThr389/Ser421/Thr424 and pS6Ser235/236 were significantly higher in ECC than those in STD and HIT at several time points (P 

< 0.01). pJNKThr183/Tyr185 and pS6Ser235/236 levels were significantly higher in type II myofibres in ECC compared with STD and HIT.

HIT exerted throughout the weakest signalling response.

We conclude that high force development during acute RE is superior for anabolic skeletal muscle signalling than fatiguing RE with lower force output but similar TUT. Our results suggest that this response is substantially driven by the higher activation of type II myofibres during RE.

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