Long-term weight training brings significant adaptations that can result in enhanced size, strength, and power of trained musculature. When there is an increase in anabolic hormones brought about by heavy weight lifting, it can increase hormonal interactions with various cellular mechanisms and enhance the development of muscle protein contractile units. When there is stimulation from a motor neuron to initiate muscle contraction, various signals are sent from the brain and muscles to endocrine glands. Hormones are secreted during and after weight lifting due to the physiological stress of the exercise itself. Hormone secretion provides information to the body regarding the amount and type of physiological stress (e.g. epinephrine), the metabolic demands (e.g. insulin), and the need for changes in resting metabolism. Thus, specific patterns of nervous system stimulation from weight training results in certain hormonal changes that are simultaneously activated for specific purposes related to recovery and adaptation to the acute exercise stress.
The patterns of stress and hormonal responses combine to shape the tissues’ adaptive response to a specific training program (like Olympic and power lifting). So without going into anything too confusing, the specific force produced by the activated muscle fibers determines the alteration in hormone receptor sensitivity to anabolic hormones as well as changes in receptor synthesis. As few as one or two weight lifting days can increase the number of androgen receptors (the receptors for testosterone) in the muscle tissue. Combined, these alterations lead to muscle growth and strength increase in the intact muscle. Following strength training sessions, remodeling of the muscle tissue takes place in the environment of hormonal secretions that provide for anabolic actions. There is an increase in the synthesis of actin and myosin and a reduction in protein degradation. Now, here is the catch to all of this great stuff due to strength training. If the stress is too great for the athlete, catabolic actions in the muscle may exceed anabolic as a result of the inability of anabolic hormones to bind to their receptors or the down regulation of receptors in the muscle tissue. So hormonal actions are important both during and after an exercise session to respond to the demands of the exercise stress. The magnitude of hormonal response depends on the amount of tissue stimulated, the amount of tissue remodeling, and the amount of tissue repaired after strength training sessions. Only muscles fibers activated by the strength training are able to be adapted. Here is where genetics and muscle fiber types come into play. Some fibers may be close to the athlete’s genetic ceiling for cell size, while others may have a great potential for growth. This is where many people draw their conclusion as to the fact that Cross Fitters are on performance-enhancing drugs, because many believe that people only have a certain ceiling for cell growth, but ultimately, unless we can see your genetic code, no one can know for certain what your genetic ceiling is for skeletal muscle cell size. Just because someone doesn’t look like you, doesn’t mean it’s impossible to look like that. Now going back to hormones, the extent of hormonal interactions in the growth of muscle fibers is directly related to the adapted size of the fibers. Thus, if an exercise program uses the same exercises over and over again, only a specific set of muscle fibers associated with those movements will be activated and stimulated to grow. Since Cross Fit is the epitome of variety, in most cases people are working various muscle groups at any given time, which will aid in the growth of all muscle groups, not just one individual group. Studies show that the volume of work, rest periods between sets, and the type of exercise are vital to the response pattern and magnitude of hormonal changes in men and women.