ISSN:
1600-0838
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
,
Sports Science
Notes:
Study I – The effect of fast (3.66 rad/s, FAST) or slow (0.35 rad/s, SLOW) isokinetic high-resistance muscle lengthening contractions on muscle fiber and whole muscle cross-sectional area (CSA) of the elbow flexors was investigated in young men. Twelve subjects (23.8±2.4 years, mean±SD) performed maximal resistive lengthening isokinetic exercise with both arms for 8 weeks (3 days/week), during which they trained one arm at a FAST velocity while the contralateral arm performed an equivalent number of contractions at a SLOW velocity. Before (PRE) and after (POST) the training, percutaneous muscle biopsies were taken from the mid-belly of the biceps brachii and analyzed for fiber type and CSA. Type I muscle fiber size increased PRE to POST (P〈0.05) in both FAST and SLOW arms. Type IIa and IIx muscle fiber CSA increased in both arms, but the increases were greater in the FAST vs the SLOW trained arm (P〈0.05). Elbow flexor CSA increased in FAST and SLOW arms, with the increase in the FAST arm showing a trend toward being greater (P=0.06). Maximum torque generating capacity also increased to a greater degree (P〈0.05) in the FAST arm, regardless of testing velocity. Study II – In a separate study, we attempted to provide some explanation of the greater hypertrophy observed in study I by examining an indicator of protein remodeling (Z-line streaming), which we hypothesized would be greater in the FAST condition. Nine men (21.7±2.4 years) performed an acute bout (N=30, 3 sets × 10 repetitions/set) of maximal lengthening contractions at FAST and SLOW velocities used in the training study. Biopsies revealed that FAST lengthening contractions resulted in more (185±17%; P〈0.01) Z-band streaming/mm(2) muscle, vs the SLOW arm. In conclusion, training using FAST (3.66 rad/s) lengthening contractions leads to greater hypertrophy and strength gains than SLOW (0.35 rad/s) lengthening contractions. The greater hypertrophy seen in the FAST trained arm (study I) may be related to a greater amount of protein remodeling (Z-band streaming; study II).
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1600-0838.2005.453_1.x
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