Effects of Hip Flexion on Knee Extension and Flexion Isokinetic Angle-Specific Torques and HQ-Ratios

Christian Baumgart,Jürgen Freiwald,Matthias Wilhelm Hoppe,Eduard Kurz

doi:10.1186/s40798-021-00330-w

Christian Baumgart, Jürgen Freiwald + Show 2 more

Open Access

https://doi.org/10.1186/s40798-021-00330-w

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Abstract

Background and MethodsDuring isokinetic knee strength testing, the knee flexion angles that correspond to the measured torque values are rarely considered. Additionally, the hip flexion angle during seated testing diverges from that in the majority of daily life and sporting activities. Limited information concerning the influence of hip angle, muscle contraction mode, and velocity on the isokinetic knee strength over the entire range of motion (ROM) is available.Twenty recreational athletes (10 females, 10 males; 23.3 ± 3.2 years; 72.1 ± 16.5 kg; 1.78 ± 0.07 m) were tested for isokinetic knee flexion and extension at 10° and 90° hip flexion with the following conditions: (i) concentric at 60°/s, (ii) concentric at 180°/s, and (iii) eccentric at 60°/s. The effects of hip angle, contraction mode, and velocity on angle-specific torques and HQ-ratios as well as conventional parameters (peak torques, angles at peak torque, and HQ-ratios) were analyzed using statistical parametric mapping and parametric ANOVAs, respectively.ResultsGenerally, the angle-specific and conventional torques and HQ-ratios were lower in the extended hip compared to a flexed hip joint. Thereby, in comparison to the knee extension, the torque values decreased to a greater extent during knee flexion but not consistent over the entire ROM. The torque values were greater at the lower velocity and eccentric mode, but the influence of the velocity and contraction mode were lower at shorter and greater muscle lengths, respectively.ConclusionsIsokinetic knee strength is influenced by the hip flexion angle. Therefore, a seated position during testing and training is questionable, because the hip joint is rarely flexed at 90° during daily life and sporting activities. Maximum knee strength is lower in supine position, which should be considered for training and testing. The angle-specific effects cannot be mirrored by the conventional parameters. Therefore, angle-specific analyses are recommended to obtain supplemental information and consequently to improve knee strength testing.

Highlights

Background and MethodsDuring isokinetic knee strength testing, the knee flexion angles that correspond to the measured torque values are rarely considered
Thereby, in comparison to the knee extension, the torque values decreased to a greater extent during knee flexion but not consistent over the entire range of motion (ROM)
The torque values were greater at the lower velocity and eccentric mode, but the influence of the velocity and contraction mode were lower at shorter and greater muscle lengths, respectively

Summary

Introduction

Background and MethodsDuring isokinetic knee strength testing, the knee flexion angles that correspond to the measured torque values are rarely considered. After return-to-sport, strength deficits and imbalances may persist and potentially cause further injuries [4,5,6,7] Within these topics, the interaction between quadriceps and hamstring muscles and the contribution of monoand bi-articular muscles remain complex and are not fully understood [8]. Quadriceps and hamstring strength is measured during concentric and/or eccentric muscle contractions in a sitting position at different velocities (e.g., 60°/s and 180°/s) [9, 10]. Knee extension and flexion peak torques during isokinetic eccentric and concentric testing at different velocities increased, while the HQ-ratio did not change [10, 13]. The findings indicate that more research is needed

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