Inter-limb strength asymmetry in adolescent distance runners: Test-retest reliability and relationships with performance and running economy
Richard C. Blagrove, Chris Bishop, Glyn Howatson, Philip R. Hayes
Abstract
The purpose of this investigation was, firstly, to quantify the test-retest reliability of strength measures in adolescent distance runners; and secondly, to explore the relationships between inter-limb strength asymmetry and performance and running economy (RE) in a similar cohort of young runners. For the reliability study, twelve (n = 6 female) post-pubertal adolescent distance runners performed an isometric quarter-squat on a dual force plate and unilateral isometric hip extension and hip abduction tests on two occasions. For the correlation study, participants (n = 31) performed the strength tests plus a submaximal incremental running assessment and a maximal running test. Running economy was expressed as the average energy cost of running for all speeds below lactate turnpoint and was scaled for body mass using a previously calculated power exponent. Allometrically scaled peak force during the quarter-squat and peak torque in the hip strength tasks showed acceptable levels of reproducibility (typical error ≤6.3%). Relationships between strength asymmetry and performance and RE were low or negligible (r < 0.47, p > 0.05), except for hip abduction strength asymmetry and RE in the female participants (r = 0.85, p < 0.001, n = 16). Practitioners should consider inter-limb hip abduction strength asymmetry on an individual level, and attempting to reduce this asymmetry in females may positively impact RE.