Fatigue is a common physiological phenomenon observed in athletes. The mechanisms of fatigue in sports have been described through various theories, such as energy exhaustion theory, protective inhibition theory, blockage theory, internal environment stability disorder theory, and free radical theory1. According to the Pavlov school, exercise conducts nerve impulses to the cerebral cortex, which leads to long-term excitation and increased energy consumption. Additionally, the body inhibits the cerebral cortex for self-protection, which leads to exercise-induced fatigue2. The application of external intervention is conducive to fatigue recovery, though exercise-induced fatigue can restore normal physical functions after a period of rest and adjustment3.
Heart rate (HR) variability reflects the variation in the heartbeat cycle and can be used to analyze the successive heart cycle time difference. HR is regulated by the autonomic nervous system (ANS). Consequently, HR variability is a noninvasive index that quantitatively reflects the dynamic balance of cardiovascular regulation by the ANS4. The ANS, a part of the peripheral efferent nervous system, can regulate the activity of visceral and vascular smooth muscles, myocardium, and glands. The autonomic nerve can be divided into sympathetic and parasympathetic nerves, which innervate the common internal organs. However, the signals from these nerves are antagonistic. For most organs such as the heart, the sympathetic nerves excite the organs, whereas the parasympathetic nerves excite and suppress the organs5.
According to studies, music and exercise affect the ANS activity5. Sympathetic activity and stimulation increase during sports, which increases the HR, stroke volume output, and systemic vasoconstriction5, whereas exercise decreases the parasympathetic activity, which increases the HR. However, the HR decreases rapidly after exercise6. Rapid HR recovery plays a crucial role in preventing cardiac overwork after exercise. The decrease in the HR after exercise is mediated by the increased parasympathetic activity and decreased sympathetic activity. Several studies have revealed that delayed activation of the parasympathetic nerve after exercise may increase the risk of sudden cardiac death. Therefore, parasympathetic reactivation after exercise is a crucial mechanism for protecting the heart of healthy individuals and patients7,8.
Music can effectively regulate the mood and ANS activity. Moreover, it serves as a potentially economical and safe interventional and treatment method9. Studies have revealed that sedative music exerts dual effects of high subjective relaxation and low tension in young adults. The relaxation effect of music can stimulate or strengthen the autonomic nerve balance and parasympathetic innervation, thereby stabilizing the ANS state10. In a study, the group listening to high-speed music exhibited stimulation in their parasympathetic activity more effectively than the control group exposed to a quiet environment11.
Thus, music can regulate the ANS activity after exercise. The body's acceptance of different music types might affect the parasympathetic nervous system differently. For example, studies have analyzed this phenomenon by asking participants to listen to their favorite music. However, these studies did not consider the type and tempo of music. The music consists of various components, such as melody, tempo, and harmony. Among these components, the tempo is the primary factor that causes changes in the parasympathetic nervous system12,13. Although a few studies have already analyzed the effects of different music tempos on the ANS activity after exercise, the current study attempted to verify whether different music tempos have a related impact on the HR and HRV system during the recovery period after high-intensity exercise among athletes. The current study also investigates the most effective music tempo for the recovery of ANS and HR after exercise to develop methods for accelerating fatigue recovery.