Sports Drink Ingestion Inflates Heart Rate Variability: Implications for Pre-training Measures
Presentation given at National Strength and Conditioning Association National Conference, Washington, D.C.
Sports teams acquire pre-training heart rate variability (HRV) in athletes to assess training status. HHowever, pre-training hydration practices may acutely affect cardiovascular dynamics and thus obscure resting-HRV. This creates a methodological concern for staff because coolers filled with bottles of water and sports drinks are typically made available for athletes in the hours before training. PURPOSE: To determine the effects of 591 ml of cold water and sports drink ingestion on HRV. METHODS: Recreationally-trained, college-age men (n = 6) and women (n = 3) volunteered for this study. On separate days after an overnight fast, subjects ingested 591 ml of water, a sports drink or control (10 ml water) in a randomized order. R-R intervals were recorded for 10 min pre- and for an additional 25 min post-fluid ingestion. Beverages were consumed within a 2-min window. The natural logarithm of the root-mean square of successive R-R intervals (LnRMSSD) was calculated from min 5–10 pre-ingestion to establish baseline (T1) and again at 5–10 min post- (T2) and 20–25 min post-fluid ingestion (T3). A linear mixed model and Cohen’s effect sizes (ES) were used to examine variation in LnRMSSD responses. RESULTS: A significant condition × time interaction was observed (p < 0.0001). LnRMSSD did not change across time for control (T1 = 4.19 ± 0.36, T2 = 4.17 ± 0.39, T3 = 4.27 ± 0.31, p >0.05). LnRMSSD increased following both water (T2 = 4.52 ± 0.26, ES = 1.06) and sports drink (T2 = 4.66 ± 0.38, ES = 1.27) ingestion at T2 (p < 0.05). LnRMSSD remained significantly elevated at T3 for sports drink (T3 = 4.54 ± 0.37, ES = 0.97) relative to control (p < 0.05). Though not statistically significant, ES analysis revealed that LnRMSSD at T2 for the sports drink condition was greater than water (ES = 0.83, p >0.05). In addition, water at T3 (4.49 ± 0.31, ES = 0.64, p >0.05) was greater than control at T3. CONCLUSIONS: Water and sports drink ingestion caused significant increases in LnRMSSD at 5–10 min post-ingestion. The effects persisted to 20-25 min post-ingestion, primarily for the sports drink condition. PRACTICAL APPLICATIONS: Fatigue-related decrements in LnRMSSD may be masked by acute fluid ingestion and thus result in a misinterpretation of training status. For example, elevated HRV typically indicates a positive coping and recovery response to training, reflecting high cardiac-parasympathetic activity. However, the effects of fluid ingestion may produce a false positive by transiently inflating an athletes HRV, masking their true resting-state autonomic activity. Therefore, practitioners should control for fluid ingestion when obtaining HRV measures prior to training. Since LnRMSSD remained above baseline at 25 min post-ingestion, further investigation using extended post-ingestion follow-up is needed to determine how long effects persist.
National Strength and Conditioning Association National Conference
Ragsdale, Chase C., Justin T. Ellis, Jade Phelps, Nicole Foster, Andrew A. Flatt.
"Sports Drink Ingestion Inflates Heart Rate Variability: Implications for Pre-training Measures."
Health and Kinesiology Faculty Presentations.