The Validity of Isokinetic Knee Extensor Endurance Measurements with Reference to Treadmill Running Capacities

The validity of isokinetic knee extensor endurance measurements with reference to treadmill running capacities was investigated. Nine male elite middle-distance runners completed a test consisting of 100 repetitive maximal eccentric and 100 concentric knee extensor actions where peak torque (Nm) and work (J) were measured. On a different day, submaximal and maximal treadmill tests were performed. Stepwise regression analysis was applied to determine the isokinetic variables with the greatest influence on the selected treadmill running capacities, including submaximal oxygen uptake (VO₂) and maximal blood lactate. Eccentric total work was significantly and negatively related to submaximal VO₂ at all three running velocities investigated (12, 14, and 15 km h^-1). The R2 values ranged from 0.48-0.59 for VO₂ ml kg^-075 min^-1, indicating that 48 - 59 % of the variability in VO₂ ml kg^-0,75 · min^-1 could be accounted for by eccentric total work. The corresponding R² values for VO in ml kg^-1 · min^-1 were 0.50-0.58. Concentric relative endurance was significantly and negatively related to maximal blood lactate (R2 = 0.73). This study has shown that isokinetic knee extensor endurance measurements of eccentric total work and concentric relative endurance are substantially related to measures of treadmill running capacity, as expressed by submaximal VO₂ and maximal blood lactate. It is suggested that these isokinetic measures may be used to evaluate specified running capacities in male elite middle-distance runners.

Keywords

Concentric - eccentric - isokinetic - methods - muscle contraction - physical endurance - validity of results