ORIGINAL RESEARCH article
Front. Physiol.
Sec. Exercise Physiology
Mechanical Loading and Fatigue-Induced Changes in Triceps Surae Muscle-Tendon Unit: Sex-Specific Responses and Recovery Dynamics
Provisionally accepted
- Lithuanian Sports University, Kaunas, Lithuania
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This study investigates the effects of a repetitive plantar flexion fatigue protocol performed to volitional exhaustion on the contractility, structure, and passive mechanical properties of the triceps surae muscle-tendon unit (MTU) in young, physically active males and females. Twenty-two participants (10 females, 12 males) underwent a fatigue protocol consisting of repetitive bilateral standing calf raises, followed by assessments conducted pre-, post-, and 24 hours after exercise. The study measured muscle contractility through peak torque, muscle and tendon structure using ultrasound echo intensity (EI), and mechanical properties via passive stiffness and hysteresis efficiency. Findings indicated a significant reduction in peak torque immediately after the fatigue protocol, alongside altered neuromuscular activation, with the gastrocnemius lateralis (GL) showing reduced EMG activity and the soleus (SOL) demonstrating compensatory recruitment. Muscle contractility exhibited partial recovery after 24 hours, while tendon EI decreased progressively, suggesting prolonged structural changes. MTU passive stiffness increased immediately post-fatigue but decreased after 24 hours, implying transient alterations in mechanical properties. Sex-related differences in MTU responses are present but limited, and recovery following fatigue occurs at different time scales across MTU tissues.
Keywords: Achilles Tendon, Calf muscles, gender differences, Mechanical Properties, Mechanical Stress
Received: 07 Nov 2025; Accepted: 16 Feb 2026.
Copyright: © 2026 Salatkaite Urbone. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Saule Salatkaite Urbone
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