Abstract
Background: Previous research demonstrates hamstring muscle-tendon stiffness (HMTS) influences isometric strength, landing biomechanics and architectural tissue properties. However, the influence on kinetics & kinematics during other modes of strength testing (isotonic dynamometry) has yet to be established. Purpose: Investigate how HMTS influences kinetics and kinematics during a novel isotonic muscle performance test which has never been done for the hamstrings. Previous work using dynamometry has been limited to isometric or isokinetic contractions, so the novelty arises from our custom isotonic protocol which allows quantitative assessment of the stretch-shortening cycle. Methods: Twenty-six recreationally active individuals (15 males, 11 females, 23.8 ± 2.5 years) completed baseline testing for anthropometry and maximum isometric hamstring strength (MVIC). At least 48 h later, subjects completed a measure of HMTS (damped oscillation technique) followed by an isotonic knee flexion test (eccentric velocity 180°/s; concentric torque 25% of MVIC). Separate linear regression models with examination of residuals were conducted between HMTS and each muscle performance variable. Standardized coefficients determined the magnitude of the relationships. Results: Significance was found for all outcome variables tested. HMTS and rate of torque development demonstrated the strongest relationship followed by isotonic concentric peak torque. The weakest relationship observed was with isometric peak torque. Conclusions: These findings build off previous work quantifying HMTS by showing HMTS more strongly relates to dynamic versus static muscle testing and identifies the potential clinical utility of isotonic dynamometry.
Highlights
Introduction iationsMuscle and tendon collectively make up a unique functional unit at every joint, which is a biological development that has implications tailored towards bipedal locomotion [1]
The regression diagnostics support the validity of each model Isotonic rate of torque development demonstrated the strongest relationship (Figure 4A) with active hamstring stiffness followed by isotonic peak torque (Figure 4B), rate of velocity development (Figure 4C), and rebound time (Figure 4D)
The use of isotonic dynamometry is largely underutilized and there is limited work The use of isotonic dynamometry is largely underutilized and there is limited work that have examined the effects of isotonic protocols, but it has been shown to be safe and that have examined the effects of isotonic protocols, but it has been shown to be safe reliable [25,26]
Summary
Introduction iationsMuscle and tendon collectively make up a unique functional unit at every joint, which is a biological development that has implications tailored towards bipedal locomotion [1]. Muscle-tendon stiffness (MTS) is an aspect of musculoskeletal function that is relevant to both athletic performance and injury risk. Tendon attaches to both bone and muscle, creating an impedance mismatch. Previous research demonstrates hamstring muscle-tendon stiffness (HMTS). The influence on kinetics & kinematics during other modes of strength testing (isotonic dynamometry) has yet to be established. Purpose: Investigate how HMTS influences kinetics and kinematics during a novel isotonic muscle performance test which has never been done for the hamstrings. At least 48 h later, subjects completed a measure of HMTS (damped oscillation technique) followed by an isotonic knee flexion test (eccentric velocity 180◦ /s; concentric torque 25% of MVIC). HMTS and rate of torque development demonstrated the strongest relationship followed by isotonic concentric peak torque
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