IB Sports, exercise and health science A.3.3 Fatigue and Recovery Key Definitions

Acidosis occurs when the pH within muscle fibers decreases, typically due to an accumulation of H⁺ ions, resulting in impaired muscle function and fatigue.

Active recovery is submaximal activity performed after fatiguing exercise, with the aim of accelerating return to homeostasis through faster lactate clearance and improved metabolite removal.

Adenosine triphosphate (ATP) is the primary chemical energy currency of the cell. Hydrolysis of ATP releases the energy used for muscle contraction, ion transport, and most other energy-requiring processes.

Central fatigue is the decline in neural activation of muscles due to changes in the brain and spinal cord, reducing an individual’s ability to sustain forceful contractions.

Chronotype describes an individual's natural predisposition toward morning alertness, evening alertness, or somewhere in between. It is shaped by genetics, environment, and age.

Circadian rhythm is the body's internal 24-hour biological cycle that regulates sleep, wakefulness, body temperature, hormone release, and other functions. It is synchronised to external cues, especially light.

A supplement that enhances ATP replenishment, muscle hydration, and recovery from high-intensity exercise.

Cryotherapy is the local or whole-body application of cold for recovery or treatment. It reduces metabolic activity, constricts capillaries, lowers nerve conduction velocity, and limits inflammation.

Muscle pain and stiffness that occur 24–48 hours after intense exercise due to microtears in muscle fibers.

A neurotransmitter involved in motivation and mood regulation, affected by psychological recovery and sleep quality.

Electrolytes are minerals that carry an electrical charge, essential for fluid balance, nerve signaling, and muscle contraction.

Excitation-contraction coupling is the process linking a muscle action potential to calcium release and contraction.

Exercise-induced muscle damage (EIMD) is the muscle disruption caused by high-intensity or unaccustomed exercise (especially eccentric work), producing reduced force, increased soreness, and reduced range of motion.

A connective tissue surrounding muscles that can become tight or restricted, affecting flexibility and muscle recovery.

Fatigue refers to the reduced capacity of muscles to perform due to prolonged exertion.

Fatigue is the inability to maintain the required or expected power output during physical activity, resulting in a decline in performance.

The production of glucose from non-carbohydrate sources, such as proteins and fats.

The stored form of glucose found in the liver and muscles, which can be broken down into glucose for ATP production during exercise.

Hyperglycaemia is an abnormally high concentration of glucose in the blood, the defining feature of both type 1 and type 2 diabetes.

A state of excess body water content, above the normal range.

Hyperthermia is an abnormally high core body temperature. It develops when heat production exceeds the body's ability to dissipate heat, often during exercise in hot or humid conditions.

Hypertrophy refers to the increase in the size of muscle fibers.

A condition where excess water intake dilutes sodium levels in the blood, causing cells to swell.

A condition in which the body or a tissue is exposed to insufficient oxygen, typically caused by low atmospheric oxygen at altitude or by impaired oxygen delivery.