A Comparison of Substrate Utilization Profiles During Maximal and Submaximal Exercise Tests in Athletes

Abstract

BackgroundExercise is primarily sustained by energy derived from lipids (plasma free fatty acids and intramuscular triglycerides), and glucose (plasma glucose and muscle glycogen). Substrate utilization is the pattern by which these fuel sources are used during activity. There are many factors that influence substrate utilization. We aim to delineate the effect of exercise intensity and body composition on substrate utilization.ObjectiveThe objective of our study was to discern the differences in substrate utilization profiles during a maximal and submaximal graded exercise test, and to determine the extent to which body composition influences substrate utilization during the exercise tests.MethodsA total of 27 male athletes, 32.5 ± 11 years of age, were recruited for this study. Body composition was analyzed using a bioelectrical impedance analyzer. Maximal and submaximal exercise tests were performed on a treadmill. A novel graded submaximal treadmill protocol was used for the submaximal test.ResultsAverage percent body fat (PBF) was 15.8 ± 5%. Average maximal oxygen consumption (VO2max) was 47.6 ± 9 mL/kg/min, while the average exercise intensity (percent VO2max) at which participants were shifting to glucose predominance for energy during the maximal and submaximal tests were 76 ± 8.3% and 58.4 ± 21.1%, respectively. A paired-samples t-test was conducted to compare percent VO2max at crossover point in maximal and submaximal graded exercise tests. There was a significant difference in percent VO2max at the crossover point for maximal (76 ± 8.3%) and submaximal (58 ± 21.1%) tests (t = 4.752, p = 0.001). A linear regression was performed to elucidate the interaction between exercise intensity at the crossover point and body composition during a maximal and submaximal graded exercise test. There was a significant effect of PBF on percent VO2max at crossover point during the maximal graded exercise test [F(1,24) = 9.10, P = 0.006] with an R2 of 0.245. However, there was no significant effect of PBF on percent VO2max at crossover point during the submaximal graded exercise test (P > 0.05).ConclusionSubstrate utilization, represented by the crossover point, is dependent on the rate of increase in exercise intensity. At maximal efforts, the crossover to carbohydrates from fats as the predominant fuel source occurs at a significantly later stage of percent VO2max than at submaximal efforts. Furthermore, body composition represented by PBF is a significant predictor of substrate utilization during maximal efforts. Athletes with a relatively higher PBF are more likely to have increased lipid oxidation during high intensity exercises than those with a lower body fat percentage.

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“…RER for instance is associated with substrate utilization [11] and alteration in the basal metabolic rate (BMR) in women of reproductive age that are performing exercise [12]. Substrate utilization depict how energy expenditure is derived from fat and carbohydrates in exercise condition [13]. Although, controversy persist on the extent at which COC influences substrate utilization from basal level into exercise condition in premenopausal women.…”

Effect of Speed Agility Quickness and Circuit Training on Lipid Profile of Soccer Players: An Observational Study

“…This change involves an increase in the relative reliance on carbohydrate oxidation to meet energy demands, accompanied by a simultaneous decrease in the relative contribution of fat oxidation. This shift in substrate utilization occurs as physical activity transitions from moderate to high intensity (Ramadoss et al, 2022). During the course of exercise, the source of fatty acids (FA) utilized also undergoes changes.…”