High-intensity exercise requires energy utilization rates that exceed the oxidative capabilities of the muscle. Activities such as sprinting require the anaerobic resynthesis of ATP to produce and maintain high levels of muscular force and are therefore limited in duration. Strength training also relies heavily on anaerobic energy sources and requires high force production by specific muscle groups.
Adaptations to High-Intensity Exercise and Strength Training
The main alterations that occur in response to regular high-intensity exercise or strength training are improvements in the structure and function of the neuromuscular system that allow more efficient production of the forces required for these activities and an enhanced ability to produce the energy required through anaerobic processes.
Neuromuscular The initial improvements in performance that occur with high-intensity exercise training are largely a result of improved coordination of the nervous system. Increased nervous system activation, more efficient neuromuscular recruitment patterns, and a decrease in inhibitory reflexes allow the individual to produce greater levels of force.
The maximum force a muscle can exert is largely determined by its cross-sectional area. In addition to the neural adaptations, strength training stimulates an increase in muscle size. This hypertrophy occurs preferentially in fast twitch muscle fibers and is brought about by increased protein synthesis in response to resistance training. The degree to which muscle hypertrophy occurs is dependent on many factors, including gender and body type. Although some researchers have suggested that strength training may increase the number of muscle cells (hyperplasia), the results of these studies are far from conclusive.
Since both high-intensity and strength training rely largely on anaerobic processes for energy production, adaptative alterations in oxygen delivery and utilization, such as increased capillarization or mito-chondrial mass of muscle cells, are relatively minor.
Metabolic In addition to the neuromuscular alterations that occur with high-intensity and strength training, several metabolic adaptations improve the ability of the muscle to resynthesize ATP from anaerobic sources. Intramuscular stores of the anaerobic energy intermediates, such as creatine phosphate (CP) and glycogen, increase after a period of supramaximal training. The activity of enzymes involved in anaerobic production of energy, such as creatine kinase and myokinase, is also increased.
Was this article helpful?