A comparison of torque characteristics produced by the knee flexors and extensors during continuous concentric and eccentric loading in power athletes and aerobically trained runners

• Main Author: Perkins, Christopher David
• Language: English
• Published: 2008
• Online Access: http://hdl.handle.net/2429/3046

It was the purpose of this investigation to evaluate continuous concentric and eccentric isokinetic loading of the knee extensors (KE) and flexors (KF) at 90, 135, and 180 deg/sec-1 in power athletes (PA), aerobically trained runners (ATR), and a control group of moderately active individuals (MA). A total of sixty healthy subjects (N= 20/group), aged 18-35 years, were assigned to one of the three groups after physiological assessment consisting of vertical jump and maximal oxygen consumption (VO2 max) was performed. Gravity corrected concentric and eccentric average isokinetic torque was measured from 75-30° of knee flexion and knee flexion-extension ratios (KF-E ratios) were calculated. A three-way ANOVA with two repeated measures (angular velocity and muscle group) was calculated for each measured contraction type (concentric and eccentric). A third three-way ANOVA with two repeated measures (angular velocity and contraction type) was computed for the analysis of KF-E ratios . Significant findings were further analyzed using Scheffé's post hoc comparisons. Finally correlations between the ability to produce concentric and eccentric torque for the KE and KF and VO2 max, vertical jumping ability , and skeletal muscle mass (SMM) were examined using Person Product Moment Correlations. It was found that the power group produced significantly greater average concentric and eccentric isokinetic torque than either the endurance (concentric and eccentric at p< 0.01) or sedentary (concentric at p< 0.05 and eccentric at p< 0.01) groups for both the KE and KF while the last two groups did not significantly d i f f e r (p> 0.05). For all groups isokinetic torque produced both eccentrically and concentrically by the KE was significantly greater at p< 0.001 than that produced by the KF at each angular velocity examined. As well, eccentric KF-E ratios were significantly greater (p< 0.001) than those produced concentrically for each of the three groups for a l l angular velocities . The power groups had significantly greater concentric and eccentric KF-E ratios (p< 0.01) than either the endurance or sedentary groups of subjects who did not d i f f e r significantly. Concentric KF-E ratios significantly increased with increasing angular velocities for both the endurance and sedentary groups (p< 0.02) while eccentric ratios did not significantly change with increasing angular velocity in any of the three groups of subjects. Finally, there were significant correlations between the ability to generate torque both concentrically and eccentrically by the knee extensors and knee flexors and vertical jumping ability while VO2 max nor SMM significantly correlated with vertical jumping ability . These findings are important when designing individualized conditioning and rehabilitation programs for athletes who are training for activities which require different velocities of muscular contraction.