Contractile Parameters Of The Knee Extensors In Young, Middle-aged, And Older Males


Exercise Science and Sport Management

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Peak power (PP) is decreased in older adults; however, less is clear regarding the determinants of PP, contractile torque and velocity. Furthermore, it is unknown if these measures are affected differently in middle and old age. PURPOSE: To compare PP and its determinants for the knee extensors in young, middle-aged, and older males. METHODS: As part of a larger ongoing investigation, contractile properties of the knee extensors were assessed in healthy, untrained young (YM: n = 8, age = 20.5 ± 1.6 yrs),middle-aged (MM: n = 6, age = 46.0 ± 2.9 yrs) and older (OM: n= 6, age = 69.0 ± 3.10 yrs) males using a Biodex System 4 dynamometer. Upon completing a familiarization visit, a testing visit involving three maximal voluntary isotonic knee extensions, performed at 40% of isometric peak torque, was completed. Participants were instructed to “kick out as hard and fast as possible” prior to each contraction. Power was calculated as the product of torque and velocity for the isotonic contractions using custom written software and PP was recorded. In addition, velocity (VEL) and torque (TQ), at the moment in time PP occurred, were recorded. One-way analyses of variance and Games-Howell post hoc tests were used to compare groups. RESULTS: PP was lower in OM compared to YM (50%; p = 0.021), but was similar in MM compared to YM and OM (p > 0.05). VELwas decreased in OM compared to YM (36%; p = 0.007) and MM (24%; p = 0.044), however, no difference was noted between MM and YM. TQ was similar between groups (p = 0.147). CONCLUSION: Our preliminary data indicate that reductions in VEL for the knee extensors occur between middle and old age prior to a decrease in PP, while TQ is maintained in old age. Thus, VEL appears to be more dramatically affected by age, and the age-related decrease in PP may be primarily mediated by impaired velocity capacity.

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Medicine & Science in Sports & Exercise

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