Biochemical Foundations of Human Vital Activity - Volkov, N.I., Nesen, E.N. 2000

Biochemistry of Sports
Biochemical Factors of Fatigue

Fatigue is a temporary decrease in work capacity that occurs during exercise, signaling the onset of unfavorable biochemical and functional shifts in the body, which leads to either cessation of activity or a significant drop in performance.

The Development of fatigue during physical exertion depends on a multitude of internal and external factors. Among the complex causes leading to fatigue, any organ or function can act as the leading link when its capacity at a given moment becomes inadequate to meet the demands of the load. Depending on the specific conditions of muscular activity and individual physiological characteristics, the primary cause of fatigue may be:

✵ a depletion of energy resources in working Muscles, as well as reduced activity of Key Enzymes;

✵ the accumulation of Metabolic waste products;

✵ the disruption of functional structures due to insufficient plastic reserves or impaired Homeostasis;

✵ alterations in neural and hormonal regulation, among others.

Identifying the leading link in the development of fatigue in each specific case is possible only through precise experimental measurements. Table 29 presents the primary results of experimental research identifying the leading factors of fatigue during exercises across various zones of relative intensity and maximum duration.

As shown in the table, the causes of fatigue vary significantly depending on the parameters of the exercise and should therefore be examined separately.

Class="center">TABLE 29. Leading factors of fatigue during exercises of varying intensity and maximum duration

Exercises

Limiting Functions

Fatigue factors

Maximum intensity (Tпр < 20 с)

Inadequate ATP resynthesis rate, depletion of intramuscular PCr reserves

↓КрФ, ТАДФ

Submaximum intensity (Tпр = 20 с 2,5 мин)

Inadequate ATP resynthesis rate, depletion of intramuscular PCr reserves, acidosis

↓КрФ, ↑АДФ, ↓рН, ↑HN3,

impaired electrochemical coupling

High intensity (Tпр = 2,5 + 10 мин)

Depletion of intramuscular Glycogen reserves, lactic acid accumulation, acidosis

↓Гликоген, ↓pH, ↓pO2

Moderate intensity (Tпр = 10 мин)

Depletion of intramuscular glycogen reserves, hypoglycemia, hyperthermia, dehydration, Ketosis

↓Гликоген, ↑R=0, ↑tвнут, ↓Н2О, CNS and cardiovascular disorders


Last update: 06/08/2026

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