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Updated: Feb 3, 2026
In vivo Measurement of Knee Extensor Muscle Function in Mice
Published on: March 4, 2021
Multilevel modelling of longitudinal changes in isokinetic knee extensor and flexor strength in adolescent soccer
João P Duarte1,2,3, João Valente-Dos-Santos1,4,5, Daniela Costa1
1a Research Unity for Sport and Physical Activity (CIDAF, UID/DTP/04213/2016) , University of Coimbra , Coimbra , Portugal.
Abstract:
The purpose of the study was to model the longitudinal development of knee extension (KE) and flexion (KF) strength in adolescent soccer players. A mixed-longitudinal sample composed of 67 soccer players aged 11.0-13.9 years at baseline was followed on three-to-five occasions over 5 years. Stature, body mass and several skinfold thicknesses were measured. Fat mass was estimated from skinfolds and fat-free mass (FFM) derived. Skeletal age was estimated with the TW2-RUS protocol. An isokinetic dynamometer was used to obtain peak torque of KE and KF from concentric assessments at an angular velocity of 180°/s. Multilevel random effects regression analyses were performed. Among youth soccer players aged 11-16 years, isokinetic strength of the knee muscle groups was reasonably predicted from chronological age (CA), stature and FFM: KE = -66.170 + 5.353 × (CA) + 0.594 × (CA2) + 0.552 × (stature) + 1.414 × (FFM), and KF = -9.356 + 2.708 × (CA) + 1.552 × (FFM). In conclusion, CA per se accounted for annual increments of 5.4 Nm in KE and 2.7 Nm in KF.
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