Heterologous contralateral repeated bout effect: eccentric knee extensor conditioning enhances neuromuscular fatigue resistance and attenuates muscle stiffness in contralateral elbow flexors in young women.
- 1Department of Exercise and Health Sciences, College of Kinesiology, University of Taipei, Taipei City, Taiwan.
- 2Department of Martial Arts, College of Kinesiology, University of Taipei, Taipei City, Taiwan.
- 3Department of Facility Planning, Ministry of Sports, Taipei City, Taiwan.
Abstract
Background
The repeated bout effect (RBE) protects skeletal muscles from exercise-induced muscle damage (EIMD). While homologous contralateral RBE is well-documented, the existence of heterologous RBE-specifically whether lower limb conditioning can protect upper limb muscles-remains debated.Purpose
This study investigated whether high-intensity eccentric exercise of the knee extensors attenuates eccentric exercise-induced neuromuscular fatigue and muscle stiffness and preserves neuromuscular control in the contralateral elbow flexors.Methods
Twenty-four sedentary young women were randomized into a Knee Extensor-Contralateral Elbow Flexor (KE-CEF) group and a Control Elbow Flexor (CEF) group. The KE-CEF group performed 60 maximal eccentric contractions (MaxEc) of the non-dominant knee extensors, followed 14 days later by 30 MaxEc of the dominant elbow flexors. The CEF group performed only the elbow flexor MaxEc. Outcome measures, including maximal voluntary isometric contraction (MVC), Acoustic Radiation Force Impulse (ARFI) imaging, and the Joint Release Angle (JRA) test, were assessed up to 120 h post-exercise.Results
The KE-CEF group demonstrated significantly less MVC loss immediately post-exercise compared to the CEF group (70.00 ± 19.85% vs. 57.67 ± 8.28%; p = 0.029). Furthermore, prior lower limb conditioning significantly attenuated peak muscle stiffness at 48 h (ARFI: 108.25 ± 4.73% vs. 125.63 ± 6.99% in CEF) and entirely preserved JRA proprioceptive stability during peak fatigue (26.58 ± 0.78° vs. 24.75 ± 1.55°; between-group p = 0.001).Conclusion
These findings provide novel evidence that a single bout of lower limb eccentric exercise confers a robust heterologous protective effect on upper limb muscles, highlighting the role of global systemic and neural adaptations in cross-limb rehabilitation strategies.
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BibTeX
@article{hsieh2026heterologous,
title = {{Heterologous contralateral repeated bout effect: eccentric knee extensor conditioning enhances neuromuscular fatigue resistance and attenuates muscle stiffness in contralateral elbow flexors in young women.}},
author = {Chung-Chan Hsieh and Szu-Kai Fu and Yu-Lin Ning and Chin-Fang Wang and Che-Ming Liu and Chia-Hsien Yu},
journal = {Frontiers in physiology},
year = {2026},
month = oct,
doi = {10.3389/fphys.2026.1823848},
url = {https://europepmc.org/article/MED/42898315},
note = {CC BY},
}
RIS
TY - JOUR
TI - Heterologous contralateral repeated bout effect: eccentric knee extensor conditioning enhances neuromuscular fatigue resistance and attenuates muscle stiffness in contralateral elbow flexors in young women.
AU - Chung-Chan Hsieh
AU - Szu-Kai Fu
AU - Yu-Lin Ning
AU - Chin-Fang Wang
AU - Che-Ming Liu
AU - Chia-Hsien Yu
PY - 2026
DA - 2026/10/05
JO - Frontiers in physiology
DO - 10.3389/fphys.2026.1823848
UR - https://europepmc.org/article/MED/42898315
AB - Background The repeated bout effect (RBE) protects skeletal muscles from exercise-induced muscle damage (EIMD). While homologous contralateral RBE is well-documented, the existence of heterologous RBE-specifically whether lower limb conditioning can protect upper limb muscles-remains debated.Purpose This study investigated whether high-intensity eccentric exercise of the knee extensors attenuates eccentric exercise-induced neuromuscular fatigue and muscle stiffness and preserves neuromuscular control in the contralateral elbow flexors.Methods Twenty-four sedentary young women were randomized into a Knee Extensor-Contralateral Elbow Flexor (KE-CEF) group and a Control Elbow Flexor (CEF) group. The KE-CEF group performed 60 maximal eccentric contractions (MaxEc) of the non-dominant knee extensors, followed 14 days later by 30 MaxEc of the dominant elbow flexors. The CEF group performed only the elbow flexor MaxEc. Outcome measures, including maximal voluntary isometric contraction (MVC), Acoustic Radiation Force Impulse (ARFI) imaging, and the Joint Release Angle (JRA) test, were assessed up to 120 h post-exercise.Results The KE-CEF group demonstrated significantly less MVC loss immediately post-exercise compared to the CEF group (70.00 ± 19.85% vs. 57.67 ± 8.28%; p = 0.029). Furthermore, prior lower limb conditioning significantly attenuated peak muscle stiffness at 48 h (ARFI: 108.25 ± 4.73% vs. 125.63 ± 6.99% in CEF) and entirely preserved JRA proprioceptive stability during peak fatigue (26.58 ± 0.78° vs. 24.75 ± 1.55°; between-group p = 0.001).Conclusion These findings provide novel evidence that a single bout of lower limb eccentric exercise confers a robust heterologous protective effect on upper limb muscles, highlighting the role of global systemic and neural adaptations in cross-limb rehabilitation strategies.
SN - 1664-042X
ER -