A comparison of circadian rhythms in work performance between physically active and inactive subjects

Area of Science:

• Chronobiology
• Exercise Physiology
• Human Performance

Background:

• Circadian rhythms influence physiological and performance variables.
• Habitual physical activity levels may modulate these rhythms.
• Understanding these modulations is crucial for optimizing performance and well-being.

Purpose of the Study:

• To compare circadian rhythms in physiological, subjective, and performance measures between physically active and inactive male subjects.
• To investigate the impact of habitual physical activity on the amplitude and phasing of circadian rhythms.

Main Methods:

• Fourteen male subjects (aged 19-29) were divided into physically active and inactive groups based on leisure-time activity.
• Measurements included rectal and oral temperature, pulse rate, arousal, sleepiness, flexibility, strength, vertical jump, PWC150, and self-chosen work-rate at six time points over 24 hours.
• Data were analyzed using the group cosinor method.

Main Results:

• Physically active subjects (Group I) showed 1.5-2.5 times greater rhythm amplitudes than inactive subjects (Group II) for oral temperature, arousal, sleepiness, flexibility, grip strength, submaximal heart rate, and self-chosen work-rate (p < 0.05).
• Group I exhibited significantly greater early-morning troughs in most performance measures (p < 0.05).
• No significant differences in rhythm phasing were observed between groups.

Conclusions:

• Physically fit individuals demonstrate higher circadian rhythm amplitudes in physiological and performance measures.
• Greater early-morning performance decrements in active individuals may contribute to these amplified rhythms.
• Findings suggest that training effects of physical activity play a role in modulating circadian rhythm characteristics.