Whey Protein Isolate Supplementation Effects on Cortisol Awakening Response, Profile of Mood States, and Heart Rate Variability

Abstract

INTRODUCTION: Decreases in heart rate variability (HRV), disruptions in cortisol awakening response (CAR), and changes in Profile of Mood States (POMS), have been associated with fatigue and strenuous physical exercise. Whey protein isolate can affect stress responses. PURPOSE: To determine the effects of whey protein isolate supplementation on CAR, POMS, and HRV after strenuous exercise. Methods: Eleven recreationally active women (19 ± 2 yrs) completed a double blinded, crossover trial. Placebo was maltodextrin (PL), intervention was 25 g of maltodextrin and 25 g of whey protein isolate (WH). Exercise was 30 min at 70-75% VO2peak (21.7 ± 0.1 ml/kg/min), 5 min rest, and 30 s Wingate anaerobic test (WAnT). HRV and POMS were recorded. Repeated measures ANOVA were used to determine differences (p < 0.05) in salivary cortisol AUCg, POMS, HRV, and WAnT fatigue index (FI). Pearson correlation and multiple regression determined associations between CAR, POMS, and HRV to FI. Results: Cortisol AUC were significantly different (p = 0.033) between PL (33.4 ± 2.0 μg*hr/dL) and WH (30.9 ± 0.8 μg*hr/dL), with no significant differences in POMS, HRV, or FI (p > 0.05). Significant Pearson correlation on Day 3 during the PL, between POMS and FI (r = -.582, p = 0.030). Neither CAR, POMS, nor HRV was able to predict FI (all p > 0.05). CONCLUSIONS: Whey protein isolate may decrease CAR, but may have no effect on POMS, HRV, or FI, and no effect on short-duration sprint cycling performance, and or reduction in central fatigue may be minimal. No supporting funding. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.