Reliability of mechanical properties of the plantar flexor muscle tendon unit with consideration to joint angle and sex
The reliability of mechanical measures can be impacted by the protocol used, including factors such as joint angle and the sex of participants. This study aimed to determine the interday reliability of plantar flexor mechanical measures across ankle joint angles and contraction types and consider potential sex-specific effects. 14 physically-active individuals participated in two identical measurement sessions involving involuntary and voluntary plantar flexor contractions, at three ankle angles (10˚ plantarflexion (PF), 0˚ (anatomical zero (AZ)), and 10˚ dorsiflexion (DF)), while torque and surface EMG were recorded. The reliability of mechanical parameters of maximal voluntary torque (MVT), rate of torque development (RTD), electromechanical delay, and tendon stiffness were assessed using absolute and relative reliability measures. MVT measures were reliable across ankle angles. RTD measures showed good group level reliability and moderate reliability for an individual during the early phase of contraction across ankle angles. Explosive voluntary torque measures tended to be less reliable from 50 ms onward, with varied reliability across angles for late-phase RTD. Tendon stiffness demonstrated the best reliability at the DF angle. Sex-based differences in the reliability of tendon measures found that females had significantly different initial tendon length between testing sessions. Despite this, tendon excursion, force, and stiffness measures demonstrated similar reliability compared to males. Ankle angle changes influence the reliability of plantar flexor mechanical measurements across contraction types, particularly for voluntary contractions. These results highlight the importance of establishing potential protocol effects on measurement reliability prior to quantifying plantar flexor mechanical measures.
History
Publication
PLOS ONE, 2023, 18 (6): e0287431Publisher
Public Library of ScienceOther Funding information
EC was supported by the Irish Research Council under Project number GOIPG/2017/378. URL of funder website: https://research.ie/ The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.External identifier
Department or School
- Physical Education and Sports Science