Isokinetic Total Work and Mitochondrial Oxidative Capacity Are Correlated in Appraising Hamstrings Endurance Performance of Young, Healthy, and Highly Active Adults.

Purpose: To assess the association between skeletal-muscle endurance performance and mitochondrial oxidative capacity of the hamstrings as respectively measured by biomechanical and physiological standards.

Methods: Nineteen (12 men and 7 women) healthy, young, recreationally active participants enrolled in our study. Participant characteristics comprised a mean and SD age of 21.3 (3.4) years, body mass index of 22 (3.3) kg/m2, hamstrings adipose tissue thickness of 13.1 (4.2) mm, and International Physical Activity Questionnaire score of 3692 (1528) metabolic equivalent-min/wk. Isokinetic dynamometry quantified total work, normalized to body mass (in joules per kilogram), performed by the hamstrings through a maximal number of dynamic contractions at 240°/s produced over 45 seconds. Near-infrared spectroscopy calculated the recovery of oxygen consumption rate, yielding the k (per minute) constant. The means of bilateral measures were analyzed. The Pearson product-moment correlation coefficient assessed the relation between normalized total work and k. Statistical significance was denoted as P < .05.

Results: Data displayed a normal distribution and randomness. The mean and SD were 69.2 (22.4) J/kg for muscle endurance and 1.78 (0.26)/min for mitochondrial oxidative capacity. There was a significant positive linear association (r = .68, P = .001) between isokinetic-dynamometry-derived normalized total work and near-infrared spectroscopy k values for the hamstrings, which can be regarded as moderately strong.

Conclusions: The isokinetic dynamometry protocol described is applicable to infer mitochondrial oxidative capacity underpinning hamstrings endurance performance in young, healthy, highly active adults. Muscle oximetry is useful for inferring total work propensity of the hamstrings in these individuals.