Effect of low- and high-carbohydrate diets on swimming economy: a crossover study
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(2020) 17:64
RESEARCH ARTICLE
Open Access
Effect of low- and high-carbohydrate diets on swimming economy: a crossover study Merry A. Bestard1†, Jeffrey A. Rothschild1,2†
and George H. Crocker1*
Abstract Background: Swimming economy refers to the rate of energy expenditure relative to swimming speed of movement, is inversely related to the energetic cost of swimming, and is as a key factor influencing endurance swimming performance. The objective of this study was to determine if high-carbohydrate, low-fat (HCLF) and lowcarbohydrate, high-fat (LCHF) diets affect energetic cost of submaximal swimming. Methods: Eight recreational swimmers consumed two 3-day isoenergetic diets in a crossover design. Diets were tailored to individual food preferences, and macronutrient consumption was 69–16-16% and 16–67-18% carbohydrate-fat-protein for the HCLF and LCHF diets, respectively. Following each 3-day dietary intervention, participants swam in a flume at velocities associated with 50, 60, and 70% of their maximal aerobic capacity (VO2max). Expired breath was collected and analyzed while they swam which enabled calculation of the energetic cost of swimming. A paired t-test compared macronutrient distribution between HCLF and LCHF diets, while repeated-measures ANOVA determined effects of diet and exercise intensity on physiological endpoints. Results: Respiratory exchange ratio was significantly higher in HCLF compared to LCHF (p = 0.003), but there were no significant differences in the rate of oxygen consumption (p = 0.499) or energetic cost of swimming (p = 0.324) between diets. Heart rate did not differ between diets (p = 0.712), but oxygen pulse, a non-invasive surrogate for stroke volume, was greater following the HCLF diet (p = 0.029). Conclusions: A 3-day high-carbohydrate diet increased carbohydrate utilization but did not affect swimming economy at 50–70% VO2max. As these intensities are applicable to ultramarathon swims, future studies should use higher intensities that would be more relevant to shorter duration events. Keywords: Fat, Energy expenditure, Efficiency, Macronutrients
Introduction It is well established that providing adequate carbohydrate to working muscles is a key contributor to optimal endurance performance [1]. However, there has been an increased interest in low-carbohydrate, high-fat (LCHF) diets in recent years, as a mechanism to increase fat oxidation during exercise and utilize more of the body’s fat stores [2]. A high capacity for fat oxidation may be * Correspondence: [email protected] † Merry A. Bestard and Jeffrey A. Rothschild contributed equally to this work. 1 School of Kinesiology, Nutrition & Food Science, California State University, Los Angeles, 5151 State University Dr, Los Angeles, CA 90032, USA Full list of author information is available at the end of the article
particularly important for athletes competing in ultradistance events [3], and adaptation to a LCHF diet could benefit long-distance swimmers who perform prolonged sub-maximal exercise with limited opportuni
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