Metabolic specificity of exercise and training is based on an understanding of the transfer of energy in biological systems. Efficient and productive training program can be designed through an understanding of the process of energy repletion for muscle work of various inensity and duration of load.
Adenosine triphosphate allows the transfer of energy from exergonic to endergonic reactions. Without an adequate supply of ATP, muscular activity and growth would not be possible.
Indicators of exercse load provide information on the condition of organism during training activity. They are sensitive to changes in the size of load. Among the indicators, there are:
The ability to resist external resistance with muscle contraction represents a basic principle of developing the complex of strength ability. Muscle contraction is conditioned by many factors. If there is no visible movements of body segments during muscle contraction, this is referred to as static strength (e.g. holding tim in squat when thighs are held horizontally to the ground). On the other hand, if muscle contraction causes a visible movement of body segments by stretching (excentric muscle contraction) or by shortening the muscle (concentric muscle contraction), it is referred to as dynamic strength (e.g. mutual movement of forearm and upper arm during benchpress exercise). The dynamic strength can further be divided into partial manifestations of dynamic strength:
Maximal strength is manifested by overcoming high or even limit external resistance at a slow speed with a specific muscle group usually in one repetition (e.g. in benchpress).
Explosive strength is manifested by overcoming low external resistance or weight of own body with maximal acceleration in single (acyclic) movement of participating segments (e.g. in throws, or take-offs).
Endurance sports are activities which are performed during longer time interval and which prevailingly use aerobic metabolism involvement. Aerobic metabolism prevails during physical exercise which is longer than than 2-3 minutes at a low, middle or submaximal intensity load. Exercies used are usually locomotions or repeated cyclic movements. Many scientific works proved that aerobic endurance may last for a longer time before fatique appears and that it can last even in the state of fatique. Also recovery rates are highly related to quality of endurance abilities and faster recovery allows the athlete to shorten rest intervals within and between training sessions and increase overall training load.
The most recognized model of endurance abilities physiology is the Cardiovascular/Anaerobic model, initially suggested by British physiologists A.V. Hill and associates in the mid-1920s. This model basically posits that a lack of oxygen in working muscles is what ultimately limits exercise performance. The cause of fatigue is primarily in cardiorespiratory system and utilization of oxygen. Most adherents to this model use the terms of VO2max, lactate threshold, and running economy when discussing aerobic or endurance training or physiology. Thanks to the new knowledge’s from this field of exercise physiology were made several new models from various points of view, e.g Neuromuscular fatigue model, Muscle trauma model, Biomechanical model, Thermoregulatory model, etc. Every of these models have wanted to supplement the initial model of Hill. The most complex revised physiological model proposed Nakes (2002) as a Central Governor Model. He draw from the original cardiovascular anaerobic model and four additional models that regulate short-time, maximal or long-time submaximal exercise. The basis of this idea is that fatigue is caused by CNS, which is not able to activate muscles to following activities or activities on a desired level. The brain protects the body by regulating power output during any form of exercise with the ultimate goal of maintaining homeostasis and protecting life. Muscle fibre power output is not regulated by factors in the muscle itself but in the brain based on continuous information from senses of the whole body. Fatigue is a relative process and as a consequence of it the exercise intensity is constantly changed during exercise as the brain either employs additional fibres to increase power output or to decrease fibre activation to adjust power output (energy) based on its calculations.