Effect of leucine supplementation on indices of muscle damage following drop jumps and resistance exercise |
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Authors: | Tyler J Kirby N Travis Triplett Tracie L Haines Jared W Skinner Kimberly R Fairbrother Jeffrey M McBride |
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Institution: | (1) Neuromuscular Laboratory, Department of Health, Leisure and Exercise Science, Appalachian State University, Boone, NC, USA |
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Abstract: | The purpose of this study was to determine the effect of leucine supplementation on indices of muscle damage following eccentric-based
resistance exercise. In vitro, the amino acid leucine has been shown to reduce proteolysis and stimulate protein synthesis.
Twenty-seven untrained males (height 178.6 ± 5.5 cm; body mass 77.7 ± 13.5 kg; age 21.3 ± 1.6 years) were randomly divided
into three groups; leucine (L) (n = 10), placebo (P) (n = 9) and control (C) (n = 8). The two experimental groups (L and P) performed 100 depth jumps from 60 cm and six sets of ten repetitions of eccentric-only
leg presses. Either leucine (250 mg/kg bm) or placebo was ingested 30 min before, during and immediately post-exercise and
the morning of each recovery day following exercise. Muscle function was determined by peak force during an isometric squat
and by jump height during a static jump at pre-exercise (PRE) and 24, 48, 72, and 96 h post-exercise (24, 48, 72, 96 h). Additionally,
at these time points each group’s serum levels of creatine kinase (CK) and myoglobin (Mb) along with perceived feelings of
muscle soreness were determined. None of the C group dependent variables was altered by the recurring testing procedures.
Peak force was significantly decreased across all time points for both experimental groups. The L group experienced an attenuated
drop in mean peak force across all post-exercise time points compared to the P group. Jump height significantly decreased
from PRE for both the L and P group at 24 h and 48 h. CK and Mb was significantly elevated from PRE for both experimental
groups at 24 h. Muscle soreness increased across all time points for the both the L and P group, and the L group experienced
a significantly higher increase in mean muscle soreness post-exercise. Following exercise-induced muscle damage, high-dose
leucine supplementation may help maintain force output during isometric contractions, however, not force output required for
complex physical tasks thereby possibly limiting its ergogenic effectiveness. |
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