Energetic Contributions Including Gender Differences and Metabolic Flexibility in the General Population and Athletes

Metabolic flexibility includes the ability to perform fat and carbohydrate oxidation, as well as oxidative capacity, which is associated with mitochondrial function, energetic contributions, and physical health and performance. During a session of graded incremental exercise testing (GIET), we investigated metabolic flexibility, the contributions of three energy systems, and performances of individuals with different metabolic characteristics. Fifteen general population (GP; n = 15, male n = 7, female n = 8) and 15 national-level half-marathon and triathlon athletes (A; n = 15, male n = 7, female n = 8) participated in this study. During GIET, heart rate (HR), oxygen uptake ((V)over dot O-2mean and (V)over dot CO2mean), metabolic equivalents (METs) in (V)over dot O-2mean, and blood glucose and lactate concentrations (La-) were measured. Furthermore, jogging/running speeds (S) at specific La-, fat and carbohydrate oxidations (FATox and CHOox), and energetic contributions (oxidative; W-Oxi, glycolytic; W-Gly, and phosphagen; W-PCr) were calculated. The percentages of HRmax, relative (V)over dot O-2mean, (V)over dot CO2mean, and METs in (V)over dot O-2mean were all lower in A than they were in GP. FATox values were lower in GP than in A, while CHOox and La- were higher in GP than in A. Negative correlations between La- and FATox were also observed in both groups. Contributions of W-Oxi, W-Gly, and W-PCr were higher in GP than in A during GIET. Moreover, values of W-Gly, and W-PCr were significantly lower and higher, respectively, in male GP than in female GP. Furthermore, S at specific La- were higher in A than in GP. It is suggested that an individualized low-intensity recovery exercise program be established, to achieve increased metabolic flexibility and oxidative capacity (aerobic base), such as public health improvements and a greater volume of higher exercise intensities; this is the type of exercise that elite athletes worldwide mostly perform during their training period and progression. This may prevent cardiac/metabolic diseases in GP.