Hormonal and Glycemic Responses During and After Constant- and Alternating-Intensity Exercise

Area of Science:

• Exercise Physiology
• Endocrinology
• Metabolic Studies

Background:

• Exercise intensity significantly impacts glucose metabolism and hormonal profiles.
• Many sports involve alternating exercise intensities, necessitating a comparison with constant intensity protocols.
• Understanding these responses is crucial for optimizing training and performance.

Purpose of the Study:

• To compare glycemic and hormonal responses to constant (CON) versus alternating (ALT) intensity cycling exercise.
• To investigate the effects of exercise intensity patterns on blood glucose, insulin, leptin, and prolactin levels.
• To determine if exercise duration and total work influence these physiological responses.

Main Methods:

• Ten healthy males completed two 60-minute cycling bouts in a randomized order.
• The ALT bout alternated high and low intensities, while the CON bout maintained a constant moderate intensity (~70% VO2max).
• Both protocols were matched for duration and total work, with mean intensity at 105% of lactate threshold.

Main Results:

• No significant differences in blood glucose concentrations were found between CON and ALT protocols or over time.
• Insulin levels decreased significantly over time in both protocols but did not differ between them.
• Leptin and prolactin levels showed no significant inter-protocol differences, though minor time-dependent changes occurred in specific protocols.

Conclusions:

• Cycling exercise at constant or alternating moderate intensity elicits similar glycemic responses in healthy males.
• Despite similar glucose control, hormonal responses over time can differ between constant and alternating exercise intensities.
• These findings highlight the nuanced physiological adaptations to different exercise intensity patterns.