Fitnessfatigue

Fitnessfatigue refers to a core idea in exercise science about how training affects performance through two interacting, opposing processes: fitness and fatigue. Fitness represents the positive adaptations and increased capacity that accumulate with training, such as stronger muscles, better endurance, and improved metabolic efficiency. Fatigue represents the temporary weariness and performance decrement that follow training, due to factors like muscle damage, depleted resources, and psychological strain. In the fitness–fatigue framework, daily performance is viewed as the net result of these two components.

The model describes distinct time courses for fitness and fatigue. Fitness tends to rise gradually with training, with lasting benefits that persist beyond individual sessions. Fatigue tends to rise quickly after training and dissipates more rapidly. Because fatigue often decays faster than fitness, well-timed training cycles and tapering can produce days when the overall performance potential is high, particularly around competition.

Applications of fitnessfatigue include planning training loads, monitoring readiness, and optimizing competition performance. Practitioners may track internal metrics such as rating of perceived exertion, sleep, mood, and soreness, alongside objective measures, to estimate the current balance of fitness and fatigue. By adjusting training frequency and intensity and incorporating taper periods, coaches aim to maximize the difference between performance capacity and residual fatigue on target days.

Limitations of the model include its simplification of complex physiology and the substantial individual variation in responses. Other models and factors, including technique, motivation, illness, and nutrition, also influence performance, making fitnessfatigue one useful but not exclusive guide for training design.