Biology of Sport
eISSN: 2083-1862
ISSN: 0860-021X
Biology of Sport
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vol. 40
Original paper

Effect of 3 and 6 mg/kg of caffeine on fat oxidation during exercise in healthy active women

David Varillas-Delgado
Millán Aguilar-Navarro
Alejandro Muñoz
Álvaro López-Samanés
Carlos Ruiz-Moreno
María Posada-Ayala
Francisco J. Amaro-Gahete
Juan Del Coso
Jorge Gutiérrez-Hellín

Universidad Francisco de Vitoria, Faculty of Health Sciences, Madrid, Spain
Camilo José Cela University, Exercise Physiology Laboratory, Madrid, Spain
Universidad Francisco de Vitoria, Faculty of Experimental Sciences, Madrid, Spain
Department of Medical Physiology, Faculty of Medicine, University of Granada, Granada, Spain
Centre for Sport Studies, Rey Juan Carlos University, Madrid, Spain
Biol Sport. 2023;40(3):827–834
Online publish date: 2022/11/18
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The aim of this study was to investigate the effect of 3 and 6 mg of caffeine per kg of body mass (mg/kg) on whole-body substrate oxidation during an incremental cycling exercise test in healthy active women. Using a double-blind placebo-controlled counterbalanced experimental design, 14 subjects performed three identical exercise trials after the ingestion of 3 or 6 mg/kg of caffeine or placebo. The exercise trials consisted of an incremental test on a cycle ergometer with 3-min stages at workloads from 30 to 70% of maximal oxygen uptake (VO2max). Substrate oxidation rates were measured by indirect calorimetry. During exercise, there was a significant effect of substance (F = 5.221; p = 0.016) on fat oxidation rate. In comparison to the placebo, 3 mg/kg of caffeine increased fat oxidation rates at 30 to 60% of VO2max (all p < 0.050) and 6 mg/kg at 30 to 50% of VO2max (all p < 0.050). There was also a significant effect of substance (F = 5.221; p = 0.016) on carbohydrate oxidation rate (F = 9.632; p < 0.001). In comparison to placebo, both caffeine doses decreased carbohydrate oxidation rates at 40 to 60% VO2max (all p < 0.050). The maximal rate of fat oxidation with placebo was 0.24±0.03 g/min, which increased with 3 mg/kg to 0.29±0.04 g/min (p = 0.032) and to 0.29±0.03 with 6 mg/kg of caffeine (p = 0.042). Acute intake of caffeine improves the utilization of fat as a fuel during submaximal aerobic exercise in healthy active women with an effect of similar magnitude after the intake of 3 and 6 mg of caffeine per kg of body mass. Thus, the use of 3 mg/kg of caffeine would be more recommended than 6 mg/kg for women seeking increased fat utilization during submaximal exercise

stimulant, phytochemical, substrate oxidation, endurance exercise, female athletes

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