Definition of Endurance

Classification of endurance

• Long-term endurance: in efforts lasting more than 15–30 minutes, when neither pace nor intensity decreases. The energy supply process is aerobic, during which cardiac output increases.
• Mid-distance endurance: refers to efforts lasting between 2 and 9 minutes. It involves both aerobic and anaerobic processes. The higher the exercise intensity, the larger the proportion of anaerobic energy production.
• Short-term endurance: between 45 seconds and 2 minutes. Important factors are the conditioning of energy stores, the capacity for oxygen-deficient energy production, and the ability of muscles to contract despite high lactate levels.
• Strength endurance plays a role in activities performed against high resistance (wrestling, artistic gymnastics), as well as in mid- and long-distance endurance sports. During strength-endurance training, special exercises are needed to increase the body's resistance to fatigue.
• Speed endurance is the resistance to the decrease in speed caused by fatigue.

Factors determining endurance

• the amount of stored energy
• the quality of metabolism
• the ability to utilize oxygen
• the storage and detoxification capacity of the liver and other organs; the functioning of the endocrine system
• the coordinated functioning of organs and organ systems; neural regulation
• morphological determinants of muscle fiber structure and distribution; the amount of working muscle (a higher proportion of slow-twitch fibers leads to more stable endurance)
• the level of movement coordination and technical skill (more economical, more efficient movements)
• psychological traits (e.g., pain tolerance)
• the magnitude of the resistance/load
• current conditioning state
• the nature of the work performed

General effects of endurance training

• slow-twitch muscle fibers are recruited in the trained muscles
• the metabolism of (muscle) cells improves (oxygen utilization, energy-producing processes, removal of metabolites)
• the resistance of (muscle) cells to toxins improves (function is not impaired even at higher metabolite levels)
• blood supply to the muscles improves; vessel walls become more elastic; the total vascular cross-sectional area increases (capillary proliferation)
• the heart's work becomes more economical and efficient (it pumps a larger blood volume at a lower heart rate)
• resting heart rate and resting blood pressure decrease
• during exertion, the increase in heart rate and blood pressure remains moderate
• blood viscosity decreases (less dense, so it flows more easily through vessels and capillaries)
• the autonomic nervous system shifts toward parasympathetic dominance

Effects of regular, high-intensity endurance work

• lung and heart volumes increase, and organ size may grow
• total hemoglobin content increases
• peripheral oxygen utilization improves
• liver functions become more efficient (energy production, removal of metabolites)
• endocrine glands enlarge (adrenal cortex, anterior pituitary lobe, thyroid, pancreatic islets)
• activity of metabolic enzymes increases