More contractions mean more micro trauma (microscopic tears in muscle fibers) and an increased metabolic rate. (homefitnessguru.net)
This rest is needed only because you have used weights that cause more microscopic tears within your muscles. (fitbodyhq.com)
A muscle strain, also called a pulled muscle, occurs when a muscle is stretched too far, and microscopic tears occur within the muscle fibers. (verywellhealth.com)