Effects of exercise intervention on cortical excitability and motor performance in healthy populations: a meta-analysis based on transcranial magnetic stimulation measurements

Abstract

OBJECTIVE: Multiple studies have confirmed that exercise interventions can induce changes in cortical excitability detectable by transcranial magnetic stimulation; however, the neural regulatory effects among different training types remain inconsistent, with no unified conclusions. Based on this, this study aims to systematically evaluate the effects of exercise interventions on cortical excitability and motor performance in healthy populations, exploring the underlying mechanisms at neurophysiological and motor functional levels. METHODS: A systematic search was conducted in PubMed, Web of Science, Embase, Cochrane Library, and Chinese databases including CNKI, VIP, and WanFang. Randomized controlled trials and crossover trials involving healthy adults undergoing exercise interventions were included, where the trial group underwent any form of exercise intervention, while the control group received sham intervention or no exercise intervention. Outcome measures included cortical excitability indexes and motor performance assessed via transcranial magnetic stimulation. Meta-analysis was performed using RevMan 5.4 software, with subgroup and sensitivity analyses conducted to explore sources of heterogeneity. RESULTS: A total of 15 studies involving 380 participants were included. Meta-analysis showed that exercise intervention had significant positive effects on both cortical excitability and motor performance. Exercise intervention significantly enhanced cortical excitability [SMD=0.38, 95%CI(0.05, 0.72), P=0.03], with a small-to-moderate effect size; and significantly improved motor performance [SMD=0.42, 95%CI(0.07, 0.76), P=0.02], with a moderate effect size. Subgroup analysis revealed that strength training significantly enhanced cortical excitability [SMD=0.53, 95%CI(0.12, 0.94), P=0.01], while motor skill training, high-intensity interval training, and balance training did not significantly enhance cortical excitability [SMD=-0.29, 95%CI(-1.13, 0.55), P=0.50; SMD=0.04, 95%CI(-0.44, 0.53), P=0.86; SMD=0.45, 95%CI(-0.37, 1.26), P=0.28]. Heterogeneity among studies was high, possibly due to differences in exercise intervention types, training duration, or measurement indicators. Sensitivity analysis confirmed the robustness of the results, and funnel plot analysis suggested low risk of publication bias. CONCLUSION: Exercise intervention can effectively enhance cortical excitability and motor performance in healthy populations, with strength training showing particularly significant effects. Future research should explore the mechanisms of different training types and optimize training program designs to further improve neuroplasticity and motor performance.

1. Introduction

In 1985, BAKER et al. first introduced transcranial magnetic stimulation (TMS) technology, which can be used not only to assess motor cortical fatigue but also to measure motor cortical excitability. Cortical excitability refers to the ability of cortical neurons to respond to stimuli, and is a key factor in the nervous system's adaptation to motor training, reflecting the ease with which neurons generate action potentials. It is regulated by the dynamic balance between excitatory neurotransmitters (such as glutamate) and inhibitory neurotransmitters (such as gamma-aminobutyric acid). Cortical excitability includes multiple outcome measures such as motor evoked potential amplitude, resting motor threshold, and short-interval intracortical inhibition, which can reflect the neural adaptations induced by exercise interventions and their potential impact on motor performance. TMS can alter cortical excitability by stimulating the primary motor cortex and evoking motor potentials in contralateral limb muscles. TMS is non-invasive, painless, functionally unique, and easy to operate, making it one of the most promising clinical treatment tools, often applied to anxiety, depression, obsessive-compulsive disorder, Parkinson's disease, and Alzheimer's disease. Therefore, research on exercise interventions based on TMS has become an important direction in the interdisciplinary field of exercise science and neuroscience.

Exercise interventions can improve motor performance through various physiological mechanisms, and their adaptations at the peripheral level have been well validated. Studies have shown that strength training is the most direct and well-evidenced way to improve motor performance; systematic resistance training can significantly increase one-repetition maximum and maximal voluntary isometric contraction, optimize motor unit recruitment patterns and firing rates, thereby enhancing neural drive and muscle contraction efficiency. In contrast, motor skill training can improve movement coordination and precision. High-intensity interval training, as an efficient training modality dominated by aerobic metabolism with significant anaerobic involvement, can simultaneously enhance aerobic endurance and cardiorespiratory function, and improve the nervous system's reaction speed and fatigue resistance. Additionally, balance training can improve postural control and body stability.

Exercise interventions not only improve cardiorespiratory function and muscle strength, but also have profound effects on the function and plasticity of the nervous system.