exertion

Exertion refers to the act of applying effort or energy to perform work, movement, or cognitive tasks. It encompasses physical exertion, such as lifting or running, and mental exertion, such as solving problems or sustaining attention. Exertion is typically described by its intensity and duration and can be measured through physiological responses or subjective perception.

Physical exertion triggers increases in heart rate, respiration, and energy expenditure. Muscles generate force to perform work, and the body's metabolism shifts to supply the needed energy, often using oxygen. Perceived exertion can be quantified by scales like the Borg Rating of Perceived Exertion, while objective measures include heart rate, oxygen consumption, and caloric burn. Sustained exertion may lead to fatigue and trigger adaptations with training.

Mental exertion involves cognitive load, sustained attention, and decision-making. It can elevate perceived effort, strain mental resources, and impair performance when demands exceed capacity or sleep and rest are inadequate.

The cost of exertion depends on fitness, age, health, nutrition, hydration, acclimatization, and environmental conditions such as temperature and humidity. Regular training can reduce relative effort for a given task and improve recovery.

Applications include athletic training, occupational design, ergonomics, and rehabilitation. Risks from overexertion include dehydration, heat illness, musculoskeletal injury, and, in extreme cases, rhabdomyolysis or cardiac events. Management relies on graduated workload increases, rest periods, hydration, and awareness of symptoms.