Black and White Race Differences in Aerobic Capacity, Muscle Fiber Type, and Their Influence on Metabolic Processes

Abstract

Obesity is a known risk factor for cardiometabolic disease. Increasing aerobic capacity (VO2max) reduces adiposity, maintains weight, and reduces the risk of developing obesity and cardiometabolic disease. Two major determinants of aerobic capacity are the metabolic properties specific to a particular muscle fiber type and the capacity of the cardiorespiratory system to deliver nutrient-rich content to the muscle. Recent research suggests that some race/ethnic groups, particularly non-Hispanic Black subjects, are predisposed to a reduced VO2max by way of muscle fiber type. Combined with insufficient physical activity, these characteristics place non-Hispanic Black subjects at an increased risk for obesity and other adverse health outcomes when compared with other race/ethnic groups. The purpose of this review was to suggest a model for explaining how skeletal muscle fiber type may contribute to reduced aerobic capacity and obesity among non-Hispanic Black subjects. Our review indicates that metabolic properties of type II skeletal muscle (e.g. reduced oxidative capacity, capillary density) are related to various cardiometabolic diseases. Based on the review, non-Hispanic Black subjects appear to have a lower maximal aerobic capacity and a greater percentage of type II skeletal muscle fibers. Combined with reduced energy expenditure and reduced hemoglobin concentration, non-Hispanic Black subjects may be inherently predisposed to a reduced maximal aerobic capacity compared with non-Hispanic White subjects, thereby increasing the risk for obesity and related metabolic diseases.

Protective role of physical activity on type 2 diabetes: Analysis of effect modification by race–ethnicity

“…Another mechanism that could contribute to lower S i and compromised glucose control, is a higher percentage of Type II skeletal muscle fibers that can be found among NHBs compared with NHWs. Previous research contrasting race–ethnic groups has suggested a potential predisposition to an increased risk for T2D with a higher percentage of Type II fibers . More specifically, among lean, obese or T2D participants, Type I fibers have been shown to have higher expression of the glucose transporter GLUT4, a greater insulin‐stimulated glucose disposal rate, higher glucose oxidation rates, and higher non‐oxidative glucose metabolism compared with Type II fibers .…”

“…changes in GLUT4 expression among Type II fibers) . Thus, PA at higher intensities may be necessary to elicit the same benefits as those with higher percentage of Type I fibers . However, more research is needed to confirm this hypothesis, especially among NHBs.…”

Racial Differences in Cancer Susceptibility and Survival: More Than the Color of the Skin?

“…The prevalence of obesity in African Americans and Hispanics is significantly higher than in Caucasians and Asians [50]. Black individuals have a lower maximal capacity of aerobic metabolism and greater percentage of fast contracting (type II) skeletal muscle fibers, which, together with a reduced energy consumption, predisposes them to obesity and other metabolic disorders [51]. While African Americans are particularly susceptible to obesity-related cancers, Hispanics seem to be relatively unaffected [48].…”

Contribution of prostaglandins to exercise hyperaemia: workload, ethnicity and sex matter!

“…). Thus, even though post‐exercise vasodilatation is smaller in BA than in WE men, and even though BAs have smaller proportions of oxidative fibres (Ceaser & Hunter, ), the fall in tissue during contractions at 60% MVC is apparently sufficient to allow PGs whose release is largely O 2 ‐dependent, to be released in BA men and make a substantial contribution to exercise hyperaemia.…”