Systemic Training Adaptations
To promote muscle growth, flexibility, endurance or agility; training must introduce stress.
Which must be followed by rest. And then stress again the type which varies.
Each new plateau achieved has to be challenged for continued growth.
Muscles adapt in cardiovascular ways as well as structurally, metabolically, neurologically, and hormonally.
Structural changes that can occur is an increase in size known as hypertrophy, and an increase in cross-linking which helps the individual fibers contract together creating more force.
Metabolically, the individual muscle fibers can learn to use energy more efficiently as well as store greater amounts of reserve energy for both force and endurance.
The way nerves send signals to muscle fibers also adapts which helps neurologically. Generally, smaller fibers are recruited first during a contraction and larger ones later which is why it is essential to train different reps in resistance training and cross train for endurance training. By exercising a muscle through a variety of angles and actions, a maximum number of motor units can be recruited for continuous growth.
Exercise leads to an absolute increase in circulating hormone levels. The type of training affects how these changes occur. For example, aerobic sustained activity will increase cortisol a stress hormone that breaks down muscle tissue and lower testosterone.
On the other hand, testosterone increases with resistance training and HIIT training.
In addition, exercise promotes growth hormone secretion. If there was one hormone everyone could use more of, one hormone that promotes health and longevity, it would be growth hormone.
Aerobic training increases the heart’s ability to contract over time, sending larger volumes of blood with each stroke. Of course, this improves oxygen delivery to tissues and promotes endurance. Although, HIIT training does not improve stroke volume as much as it improves metabolism of oxygen at the cellular level.
When considering your needs analysis, consider what systems above require the most adaptation and how to augment that system. Consider personal interests and conditioning state. In some cases, hormone replacement may be extremely beneficial. An exercise prescription may require a transition period to improve cardiovascular health and endurance prior to any serious resistance training as another example.