Rest Intervals

I am often asked by my members “how long do I need to rest between sets?” This is a good question and in fact an important question. Here is the answer.

The rest interval is the time between sets and exercises. Rest intervals play a major role in the outcome of a training program. The energy systems of the body are dependant on the training phase and intensity level. The rest period will determine the extent at which the energy resources are restored for the next set. A rest phase of approximately 30 seconds replenishes about 50% of ATP/CP stores. ATP is the high energy phosphate compound that gives rise to cellular energy throughout the entire body. The shorter the rest period, the less ATP/CP system has to restore, this in turn will provide less energy for subsequent sets. Lactic acid accumulation occurs decreasing neuromuscular control. Fatigue of the muscle cell decreases overall force production, stablization, force reduction factors within the motor unit continuum.

Another component that occurs from insufficient rest periods is the insufficient replenshing of acetylcholine at the neuromuscular junction. A decreased concentration of acetylcholine decreases propagation of the the action potential, which ultimately reduces contractability force of the muscle cell.

High levels of lactic acid decreases peak tension affecting the overall production of the muscle cell itself. A delayed or fatigued action potential produces a weaker electrical signal to the brain and CNS making the synaspse weaker. Decreased proprioceptive factors and kinesthesia awareness is hindered in a fatigued state. Ultimately, poor rest intervals can result in injury.

However, on the other spectrum resting for too long between sets or exercises, the blood leaves the muscle area and the temperature decreases, the neurohormones turn off, and the recovery phase begins. Trying to restart the muscle tissue after a long rest intervals becomes counterproductive.

I advocate taking in oxygen between sets to help increase the restoration of ATP quicker and to help buffer off accumulated lactic acid. The best method is to bend over and take 6-8 deep breaths filling the lungs completely. Breath in through the mouth, through pursed lips. This method works great and will help you get the necessary oxygen back into the bloodstream to keep the muscle myoglobin concentration high enough to recharge the action potential of the muscle for the next set.

Daryl Conant, M.Ed