Submaximal loads and strength development
Coaches are constantly searching for answers to how they can make their trainees stronger. Some use a mixture reps and sets, some use percentage based loads and others stick to heavy, high intensity sessions. One thing is certain; using light loads for high repetitions will not get your athlete stronger. They may be able lift the lightweight twenty, thirty or more times, but when the weights start pilling on the bar, they are unable to move the load.
When a person lifts a lightweight, some positives do occur. They are exercising; however, they are not maximizing their time in the session.
The physiological response to the lightweight exercise results in several different actions with in the body.
Only a portion of the available motor units (MU) are recruited to lift the load.
The fastest twitch and strongest MU’s are not called upon to lift the weight at all.
The neural stimulation frequency is not at its optimal state.
The MU activity is not synchronous within the muscle.
Thus, the lightweight loads produce a limited training effect on the lifter. However, this situation changes immediately when a heavier, higher intensity of the 1RM is used in the training schedule
The most dramatic change occurs in the number of motor units that are recruited to lift the load. In the case of the heavy loads these MU are maximized to their fullest extend.
The fastest and strongest MU are then recruited.
The MU’s discharge frequency is at its optimal state.
It is believed that the motoneuron activity is synchronous meaning the structure is working together to produce a superior muscleman effort output.
V. M. Zatsiorsky states in his book, Science and Practice of Strength Training, that lifting at a level of low intensity will not improve the intramuscular coordination that is so vital to successfully lifting at the heavier percentages of your one repetition maximum.
Bearing the latter in mind, it doesn’t make a lot of sense to spend a great deal of time lifting lightweights does it? Unless you are training for speed, but that is a whole different issue.
 Motor unit (MU): a motonneuron and the muscle fibers that it fires up