Maximum isometric torque at individually-adjusted joint angles exceeds eccentric and concentric torque in lower extremity joint actions

Andreas Stotz,Joel Mason,Ebrahem Maghames,Andreas Groll,Astrid Zech

doi:10.1186/s13102-022-00401-9

Abstract

BackgroundPrevious research indicates the high relevance of optimal joint angles for individual isometric strength assessment. The objective was to compare lower limb peak isometric muscle strength abilities at the strongest joint angles with those of dynamic contractions in healthy young adults.MethodsEighteen young male adults performed maximum concentric, isometric, and eccentric contractions of the ankle, knee, and hip flexors and extensors, and hip adductors and abductors in a randomized sequence on an isokinetic dynamometer (ISOMED 2000). Angular velocity was set at 60°/s. The peak of concentric contraction torque curves was used to define optimal joint angles best suited to generate maximum torque during isometric contractions. Maximum voluntary contraction torque of all contraction conditions was adjusted for limb weight and analyzed via a generalized linear mixed gamma regression model (GLMM).ResultsThe gamma GLMM revealed strongly significant effects for all three categorical covariates (contraction types, muscle group, and test order) (p < 2 times 10^{ - 16}). Eccentric contraction increases the muscle torque (hat{beta }_{k} = 0.147) compared to concentric contraction, and isometric contraction even more (hat{beta }_{k} = 0.258). A moderate individual-specific variation was found (random effects standard deviation sigma_{b} = 0.093).ConclusionThe results support the importance of optimal joint angles for isometric maximum strength assessment. When such conditions are given, isometric contractions can produce higher muscle torques than eccentric contractions in the lower body.

Highlights

Previous research indicates the high relevance of optimal joint angles for individual isometric strength assessment
Other explanations such as the lack of familiarization of the participants with eccentric contractions inducing a deficit of muscle activation [26] that is not found in trained individuals [24] might be responsible for the lack of difference between eccentric and isometric peak torque
The gamma generalized linear mixed model (GLMM) revealed strongly significant effects for all three categorical covariates ( p < 2 × 10−16 ), see Table 2, where concentric contraction, plantar flexion and test order group 1 where chosen as reference categories for the categorical covariates

Summary

Introduction

Previous research indicates the high relevance of optimal joint angles for individual isometric strength assessment. A closer proximity to the optimal joint angle for maximal expression of isometric torque may explain why some studies report no difference in maximal torque production between eccentric and isometric contractions of the knee extensors [24] and plantar flexors [25]. Other explanations such as the lack of familiarization of the participants with eccentric contractions inducing a deficit of muscle activation [26] (compared with isometric contractions) that is not found in trained individuals [24] might be responsible for the lack of difference between eccentric and isometric peak torque

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Conclusion