Initial Strength Gains
After one’s first few sessions of regular resistance exercise, it is typical to perceive noticeable strength gains. This is interesting because you have not been at it for long although you feel stronger. The reason for this is primarily due to changes in your nervous system from the brain all the way down to the muscle fiber. One of the most significant changes has to do with what physiology textbooks describe as improved recruitment of “motor units” at the level of the muscle. A motor unit is a single nerve that has tentacle like extensions connecting into many muscle fibers within one muscle. Groups of motor units fire in certain patterns to create a muscle contraction. These patterns can be quite different in the hands of a piano player, a violinist, and a tennis player. Small muscles that are responsible for a high level of coordination such as those found in the hand or eye have small motor units consisting of the motor nerve and say, ten muscle fibers. Large muscles responsible for high force output such as those in your thigh can have as many as 2000 or so fibers per motor unit. After just a handful of exercise sessions, there is enhanced efficiency in the firing rate, the order and coordination of the symphony of motor unit activation. This is a type of learning and is why you feel stronger.
During normal every day tasks we do not use 100% of our muscle fibers. The right dose of strength training can help you exercise a much larger portion of these fibers and can help maintain your muscle potential throughout life. You lose what you don’t use. Physical Therapists are licensed healthcare professionals who can design individualized wellness plans.
Anna Kotula, Doctor of Physical Therapy