JOINT-, CONTRACTION-TYPE, AND CONTRACTION-VELOCITY SPECIFIC DIFFERENCES IN MUSCLE STRENGTH OF LOWER EXTREMITY IN CHILDREN

Abstract

PURPOSE: Concentric and eccentric muscle contractions produce dynamic movements requisite for activities of daily living (e.g. walking, running, and jumping). The purpose of this study is to examine joint-, contraction-type, and contraction-velocity specific differences as a function of lower extremity muscle strength in children. METHODS: Thirteen children (male = 5, female = 8; age = 11.2 ± 1.1 years) participated in our cross-sectional study. After a familiarization session, participants performed randomized unilateral isometric (ISO), concentric (CON) and eccentric (ECC) muscle strength testing of the non-dominant knee extensors and ankle plantarflexors in a seated position at 120°/s and 180°/s on Biodex. Obtained peak torques were normalized to body mass. Differential muscle strengths were also calculated [D1 = (ECC120-CON120)knee; D2 = (ECC120-CON120)ankle; D3 = (ECC180-CON180)knee; D4 = (ECC180-CON180)ankle]. We used separate within repeated measures ANOVA to calculate muscle strength differences. Paired t-tests were used to compare the differential muscle strength (D1vs D2; D3 vs D4). RESULTS: No difference was noted between ISO and CON. However, ISO and CON were lower than ECC muscle strength at 120°/s and 180°/s ( P < 0.01) at the knee and ankle. No difference was noted between D1 and D2 but D4 was significantly lower than D3 (P = 0.009). CONCLUSION: Irrespective of contraction velocity and the body sites, children display greatest muscle strength for ECC relative to CON or ISO which is site-dependent. Whether this is dictated by maturation associated site-specific neuromuscular inhibition remains to be investigated.