BIOLOGY Volume 2 - A Guide to General Biology - 2004

18. THE ANIMAL SKELETAL AND MUSCULAR SYSTEMS

18.4. The Muscular System

18.4.6. Effects of Training on Muscle Performance

Although an individual's Muscle mass is fundamentally determined by genetics, it can be increased through Physical Exercise by roughly 60%. This occurs primarily due to an increase in the diameter of muscle fibers, and to a lesser extent, through an increase in the number of fibers themselves and their myofibrils.

Long-Term Biochemical Changes

Regular training increases both the number and size of Cell/35.html">Mitochondria within muscle fibers. As a result, processes associated with aerobic Respiration—the Krebs cycle, electron transport, and Fatty acid oxidation—proceed more intensely. The capacity of mitochondria to generate ATP can double. The fibers accumulate greater amounts of creatine phosphate, Glycogen, fat, and Myoglobin. As myoglobin enriches the Muscles, oxygen reserves increase. Combined, these adaptations mean that during physical exertion, athletes experience a reduced dependence on Anaerobic respiration, resulting in less lactate accumulation in the muscles. At the same time, the body's ability to mobilize lipid reserves for energy by breaking them down into Fatty acids improves. Consequently, it is easier for an athlete than for an untrained person to "lose weight" through physical exercise.

Long-Term Increases in Muscle Strength

The force exerted by a muscle increases only when it works against a greater load than before. This is achieved by increasing either the intensity of the work or its overall duration. Muscles forced to develop contraction forces close to their maximum become stronger very rapidly, even if training sessions take only a few minutes a day. However, to maintain this result, training must be regular. Otherwise, the muscles revert to their baseline state, losing strength and The ability to contract frequently, leading to what is commonly known as falling out of shape.

Blood supply to Muscles

Regular training increases the density of Blood Vessels supplying the muscles. This creates a more efficient system for delivering oxygen and glucose to the muscles, as well as for removing metabolic end-products. With prolonged training, the cardiovascular and respiratory systems adapt in such a way that the oxygen debt experienced during initial exercise can subsequently be fully compensated. A muscle's capacity for sustained, intense work generally depends on the speed and efficiency with which it absorbs and utilizes oxygen.

Coordination

Training improves the coordination of muscles operating in antagonistic pairs, enabling more complex and precise movements; the speed of contraction and relaxation also increases. The latter is particularly crucial because if a muscle fails to relax in time, it can be torn by the pulling force of its antagonist.

Muscle strains and tears can occur under excessive loads. To reduce the likelihood of injury, specialized "warm-up" exercises are used. Following intense exertion, some residual tension typically remains in the muscles. To relieve this, relaxation exercises are employed, during which the musculature is gently stretched.