Dutch researchers report that a different technique for assessing adaptation to training gives a more accurate picture than the usual approach of measuring muscle enzyme levels. In the study, researchers instead used "quantitative needle electromyography" (QEMG) to evaluate adaptations in skeletal muscle in athletic horses.

A horse’s performance can be improved by gradually increasing the duration and intensity of its exercise sessions. If the training load is balanced with the horse’s exercise tolerance, then an increased athletic performance will ensue within a few days.

"In contrast, sustained, vigorous exercise can result in incomplete recovery and a decreased performance level," explained Inge Wijnberg, DVM, PhD, Dipl. ECEIM, of the department of equine science, faculty of Veterinary Medicine at Utrecht University, and lead researcher on the study.

This incomplete recovery is referred to as overreaching and can progress to a more severe and chronic stage called overtraining