E10 Energy Balance

Topic

The energy balance models the flow of energy during movement and physical exertion: from the metabolic substrates consumed by the body to the useful mechanical work produced by that consumption and the dissipated heat lost in the process.

The first stage involves metabolic substrates: the body consumes these substrates to generate the energy required to sustain physical exertion; the greater the exertion the body must sustain, the more metabolic substrates it consumes per unit of time.

The second stage is useful mechanical work: a portion of the energy released through the consumption of metabolic substrates is converted into useful mechanical work—that is, the actual movement the body produces during physical exertion.

The third stage is dissipated heat: energy released from metabolic substrate consumption that is not converted into useful mechanical work is lost as dissipated heat; consequently, the greater the amount of dissipated heat relative to useful mechanical work, the less efficient the body's energy conversion becomes.

Based on this transformation chain, the energy balance quantifies three metrics: oxygen consumption (the amount of oxygen the body needs to release energy from metabolic substrates); energy expenditure (the total energy released by that substrate consumption); and musculoskeletal system efficiency (the proportion of that energy expenditure converted into useful mechanical work rather than lost as dissipated heat).

Quantifying oxygen consumption, energy expenditure, and musculoskeletal efficiency enables the energy balance to precisely calibrate therapeutic exercise: by knowing how much energy a person requires to sustain a specific level of physical exertion and what proportion of that energy is effectively converted into useful mechanical work, it is possible to adjust the intensity of the therapeutic exercise to match the person's actual musculoskeletal capacity, without demanding more energy than their energy balance can sustain.

ID:883