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

Biochemistry of Sports
Biochemical Factors of Athletic Performance
Factors Limiting Human Physical Performance

Physical performance, or The ability to perform a specific type of muscular work, depends on an individual's innate qualities and potentials, the realization of which ensures the successful execution of given tasks. This capacity manifests itself most vividly and fully in competitive sports. To achieve high results and triumph over equally gifted and capable rivals, an athlete must master a full arsenal of complex motor skills and, through years of multi-year training, reach the highest level of development in those qualities upon which success in their chosen discipline depends.

Among the factors determining human physical performance, some manifest themselves across all types of human motor activity (primary factors), while others are specific to a particular kind of activity. The primary factors of universal significance typically include the following: 1 — human bioenergetic capacities (aerobic and anaerobic); 2 — neuromuscular capabilities (Muscle strength and exercise execution technique); 3 — psychological factors (motivation and athletic competition tactics).

Muscle strength and bioenergetic capacities constitute the group of potential factors, whereas technique, tactics, and psychological preparation form the group of performance factors, which determine the degree to which potential factors are realized under the specific conditions of a chosen activity. Rational exercise technique allows for a greater and more effective utilization of strength and bioenergetic capacities within each movement cycle or its individual elements. Advanced tactical execution in competitive sports enables a better realization of strength and bioenergetic potentials throughout a competition or in its specific episodes.

The crucial role of performance factors lies in the fact that under the specific conditions of a chosen activity, strength and bioenergetic potentials can manifest themselves to their fullest extent. These potentials may remain inaccessible if an individual lacks the necessary motor skills or is insufficiently motivated to accomplish the given task.

In the manifestation of muscle strength and power—qualities commonly grouped in sports theory and practice under METABOLISM/2.html">THE CONCEPT OF speed-strength preparedness—the structural Organization and enzymatic properties of muscle contractile Proteins are of decisive importance. The magnitude of the force developed by a muscle during contraction is proportional to the number of cross-bridges (links) between Actin and Myosin filaments within the myofibrils. The potentially possible number of these bonds, and consequently the magnitude of maximum muscle strength, depends on the actin content and the length of myosin filaments within each sarcomere comprising the myofibrils.

Sarcomere length or the degree of myosin polymerization in the thick filaments of myofibrils is a genetically determined factor, meaning it does not change during individual development or under The Influence of training, yet it significantly affects the manifestation of motor qualities. Different types of muscle fibers possess varying sarcomere lengths. The content of actin protein within Muscles changes substantially during individual development and through training, showing marked differences across various fiber types and in muscles with distinct functional profiles.

In voluntary human movements, The Development of muscular force occurs alongside changes in contraction speed, and the overall result of the summation of these properties is expressed by the level of power developed. In skeletal muscles, this power depends on the ATPase activity of myosin, which varies significantly among different muscle fiber types, being higher in fast-twitch fibers compared to slow-twitch ones.

In human skeletal muscles, fast- and slow-twitch fibers exist in varying proportions. Changes in the proportion of specific fiber types in different muscles directly affect their functional properties. Fast- and slow-twitch fibers are part of different motor units that respond differently to stimulation. At low stimulation frequencies during exercise of moderate intensity, slow motor units are primarily recruited. As exercise intensity increases and the stimulation frequency exceeds the threshold for fast motor units, the enhancement of work performance increasingly relies on fast-twitch muscle fibers: the higher the percentage of fast-twitch fibers within a Skeletal Muscle, the greater its speed-strength characteristics.

The most important factors limiting human physical performance are bioenergetic capacities. The execution of any type of work involves Energy Expenditure. As demonstrated previously (see Chapter 15), energy production in The Human Body during muscular work is accomplished via aerobic or anaerobic pathways.

Depending on The Nature of the bioenergetic processes occurring during muscular work, it is customary to distinguish three main Functional Characteristics of an individual that determine physical performance:

✵ alactic anaerobic capacity, associated with the processes of anaerobic breakdown of ATP and PCr in working muscles;

✵ glycolytic anaerobic capacity, reflecting the potential for an enhanced anaerobic glycolytic process during work, which leads to the accumulation of lactic acid in the body;

✵ aerobic capacity, associated with the ability to perform work through enhanced aerobic processes in Tissues alongside an increased delivery and utilization of oxygen to working muscles.

The metabolic performance of each of the aforementioned Energy Sources is characterized by such quantitative criteria as power, capacity, and efficiency.

These criteria can be represented by A large number of diverse biochemical indicators, some of which characterize Biochemical changes in individual Organs and tissues and thus have local significance, while others reflect the properties and capabilities of the entire Organism.