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Heterologous contralateral repeated bout effect: eccentric knee extensor conditioning enhances neuromuscular fatigue resistance and attenuates muscle stiffness in contralateral elbow flexors in young women.
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Hsieh Chung-Chan, Fu Szu-Kai, Ning Yu-Lin, Wang Chin-Fang, Liu Che-Ming, Yu Chia-Hsien
Аннотация
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.
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.