Abstract
BackgroundWith prolonged physical activity, it is important to maintain adequate fluid balance. The impact of consuming isotonic drinks during and after exercise on the autonomic regulation of cardiac function is unclear. This study aimed to analyze the effects of consuming an isotonic drink on heart rate variability (HRV) during and after prolonged exercise.MethodsThirty-one young males (21.55 ± 1.89 yr) performed three different protocols (48 h interval between each stage): I) maximal exercise test to determine the load for the protocols; II) Control protocol (CP) and; III). Experimental protocol (EP). The protocols consisted of 10 min at rest with the subject in the supine position, 90 min of treadmill exercise (60% of VO2 peak) and 60 min of rest placed in the dorsal decubitus position. No rehydration beverage consumption was allowed during CP. During EP, however, the subjects were given an isotonic solution (Gatorade, Brazil) containing carbohydrate (30 g), sodium (225 mg), chloride (210 mg) and potassium (60 mg) per 500 ml of the drink. For analysis of HRV data, time and frequency domain indices were investigated. HRV was recorded at rest (5–10 min), during exercise (25–30 min, 55–60 min and 85–90 min) and post-exercise (5–10 min, 15–20 min, 25–30 min, 40–45 min and 55–60 min).ResultsRegardless of hydration, alterations in the SNS and PSNS were observed, revealing an increase in the former and a decrease in the latter. Hydrating with isotonic solution during recovery induced significant changes in cardiac autonomic modulation, promoting faster recovery of linear HRV indices.ConclusionHydration with isotonic solution did not significantly influence HRV during exercise; however, after exercise it promoted faster recovery of linear indices.
Highlights
With prolonged physical activity, it is important to maintain adequate fluid balance
It is known that reduced cardiac parasympathetic regulation associated with increased sympathetic activation may trigger malignant ventricular arrhythmias, and that systemic metabolic disorders, as well as hemodynamic or neurophysiological disorders appear to play an important role in lethal arrhythmias [9]
The anthropometric characteristics of the subjects and their responses obtained during the incremental test are described in Table 1, while Table 2 shows data regarding body mass and temperature in CP and EP
Summary
It is important to maintain adequate fluid balance. Physical activity leads to increased metabolic rate and heat production [1], resulting in loss of water and electrolytes and glycogen depletion in the liver and muscles [1,2]. The loss of these elements may lead to dehydration, affecting physical performance and impairing health [3]. According to Brouns et al, [6] and Coyle [7], sports drinks without caffeine can help to maintain physiological homeostasis Another aspect of risk related to exercise is failure of cardiovascular function, especially for practitioners who exercise infrequently [8]. According to Carter et al, [5], “the combination of these two factors suggests changes in the global cardiac autonomic stability”
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