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Short-term high- vs low-velocity isokinetic lengthening training results in greater hypertrophy of the elbow flexors in young men (2005)

Shepstone, T. N. ; Tang, J. E. ; Dallaire, S. E. ; [et al.]

Oxford, UK : Munksgaard International Publishers

Scandinavian journal of medicine & science in sports 15 (2005), S. 0

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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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Effects of acute expansion of plasma volume on cardiovascular and thermal function during prolonged exercise (1997)

Grant, S. M. ; Green, H. J. ; Phillips, S. M. ; [et al.]

Springer

European journal of applied physiology 76 (1997), S. 356-362

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ISSN: 1439-6327

Keywords: Key words Cardiovascular ; Exercise ; Prolonged ; Acute hypervolaemia ; Thermoregulation

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Abstract To investigate the hypothesis that an increase in plasma volume (PV) is obligatory in reducing the cardiovascular drift that is associated with prolonged exercise following training, a plasma expander (Macrodex) was used to acutely elevate PV. Eight untrained volunteers [maximal oxygen consumption; V˙O2 max 45.2 (2.2) ml · kg−1 · min−1, mean (SE)] cycled for 2 h [at 46 (4)% V˙O2 max ] in ambient conditions either with no PV expansion (CON) or following PV expansions of either 14% (LOW) or 21% (HIGH). During CON, heart rate (HR) increased (P〈0.05) from 147 (2.4) beats · min−1 to 173 (3.6) beats · min−1 from 15 to 120 min of exercise. Both LOW and HIGH conditions depressed (P〈0.05) HR, an effect that was manifested following 15 min of exercise. In contrast, stroke volume (SV) was elevated following PV expansion, with values (ml) of 89.6 (6.8), 97.8 (5.9) and 104 (4.6) noted by 15 min of exercise for CON, LOW and HIGH conditions, respectively. Acute PV expansion, regardless of magnitude, also resulted in elevations in cardiac output (Q˙ c). These differences between conditions persisted throughout the exercise, as did the elevation in Q˙ c that was noted with LOW and HIGH conditions. No difference between Q˙ c, HR or SV was found between LOW and HIGH. In addition, neither LOW nor HIGH conditions altered the change in rectal temperature that was observed during exercise. These results demonstrate that, at least for moderate exercise performed in ambient conditions, PV expansion serves only to alter cardiac function (Q˙ c, HR, SV) early in exercise, and not to attenuate the drift that occurs as the exercise is prolonged.