Acute Effects of Progressive Muscle Relaxation on Brain Waves, Heart Rate Variability, Muscle Tone, and Mental Stress

In modern environments, stress is present regardless of age or social role. Stress does not always have negative effects; in fact, it is a necessary response for survival, known as the stress response. This response includes increased heart rate, blood pressure, blood glucose levels, and decreased alpha brainwave activity. These physiological changes are primarily regulated by the sympathetic and parasympathetic branches of the autonomic nervous system, enabling us to cope with environmental threats. However, when the stress response system becomes overwhelmed or imbalanced-whether due to accumulated chronic stress or acute stress-it may result in adverse effects on both physical and mental health.

Relaxation techniques are non-pharmacological methods that promote parasympathetic nervous system activity. The goal is to reduce excessive arousal, alleviate anxiety, slow down thought processes, and relieve stress, thereby achieving relaxation in a natural way. These methods help lower blood pressure, improve circulation, relax muscles, and enhance concentration. Previous studies have demonstrated a correlation between relaxation and attention, suggesting that relaxation can improve attentional efficiency. Moreover, it is well-documented that executive function tends to decline under stress. Relaxation techniques are commonly incorporated into psychological therapies, yet they are more accessible, easier to practice, and can be conveniently performed at home.

Therefore, the aim of this study is to investigate whether PMR can produce immediate relaxation effects as measured by EEG (cortical excitability), heart rate variability, and muscle tone, and whether it can improve performance under psychological stress. The goal is to further explore the potential application of PMR in healthy populations facing acute stress conditions.