Bioenergetics of Exercising Humans

Abstract

Human muscles, limbs and supporting ventilatory, cardiovascular, and metabolic systems are well adapted for walking, and there is reasonable transfer of efficiency of movement to bicycling. Our efficiency and economy of movement of bipedal walking (≈30%) are far superior to those of apes. This overall body efficiency during walking and bicycling represents the multiplicative interaction of a phosphorylative coupling efficiency of ≈60%, and a mechanical coupling efficiency of ≈50%. These coupling efficiencies compare well with those of other species adapted for locomotion. We are capable runners, but our speed and power are inferior to carnivorous and omnivorous terrestrial mammalian quadrupeds because of biomechanical and physiological constraints. But, because of our metabolic plasticity (i.e., the ability to switch among carbohydrate (CHO)- and lipid-derived energy sources) our endurance capacity is very good by comparison to most mammals, but inferior to highly adapted species such as wolves and migratory birds. Our ancestral ability for hunting and gathering depends on strategy and capabilities in the areas of thermoregulation, and metabolic plasticity. Clearly, our competitive advantage of survival in the biosphere depends in intelligence and behavior. Today, those abilities that served early hunter-gatherers make for interesting athletic competitions due to wide variations in human phenotypes. In contemporary society, the stresses of regular physical exercise serve to minimize morbidities and mortality associated with physical inactivity, overnutrition, and aging.

A new method to calculate external mechanical work using force-platform data in ecological situations in humans: Application to Parkinson's disease

“…The results showed that the average W EXT from a standing position was very close to theoretical work (0.4% difference). We also found, in agreement with the literature [7,32,33], an expected value for mechanical work efficiency of 25-30%.…”

Integrative Biology of Exercise

“…Hypotheses generated over the last two decades from comparative physiologists (Hochachka et al, 1999) and anthropologists (Bramble and Lieberman, 2004) suggest that the combined traits of superior endurance capacity and an impressive ability to thermoregulate permitted ancestral humans from the high plains of East Africa to succeed as game hunters and thereby obtain high-protein sources of food that were essential for the emergence of larger brains and complex cooperative behavior. Human skeletal muscles, limbs, and the supporting ventilatory, cardiovascular, and metabolic systems were well suited for upright locomotion, with economy of movement for bipedal walking and running far exceeding that of other primates (Bramble and Lieberman, 2004;Brooks, 2012). At this time, lifestyle and energy availability were inextricably linked to the periodic cycles of feasts and famines, with certain genes evolving to regulate efficient storage and utilization of endogenous fuel stores, the so-called ''thrifty genes'' (Neel, 1962).…”

Higher rate of fat oxidation during rowing compared with cycling ergometer exercise across a range of exercise intensities

“…A myriad of intrinsic biochemical factors influence the relative contributions of fat and carbohydrate to energy expenditure during exercise (Spriet & Watt, ; Brooks, ), but extrinsic factors such as the intensity and mode of exercise are important regulators of substrate utilization (Romijn et al., ; van Loon et al., ; Achten et al., ; Knechtle et al., ). The contribution of fat to energy expenditure is greatest during low‐ and moderate‐intensity exercise but declines thereafter (Romijn et al., ; van Loon et al., ).…”