Too intensive training without adequate recovery may lead to overreaching or overtraining, which urges for early detection. To study whether quantitative needle electromyography (QEMG) is more sensitive to detect training (mal) adaptation than muscle enzyme activities, 12 Standardbred geldings were subjected to a 32 week program. After a habituation training phase (phase 1, 4 weeks), and a normal training (NT) phase with increasing intensity and volume (phase 2, 18 weeks), an intensified trained group (IT, phase 3) and a control group was formed, which continued normal training as in the last week of phase 2. All horses entered a detraining phase (DT, phase 4). After each training phase, QEMG analysis and biochemical enzyme activity in muscle biopsies were performed from vastus lateralis (VL) and pectoralis descendens (PD) muscle in order to identify (mal)adaptation of skeletal muscle to NT, IT and DT. NT resulted in a significant adaptation of QEMG parameters, whereas in muscle biopsies hexokinase activity was significantly decreased. IT induced a stronger adaptation in QEMG variables compared to trained controls. After IT, enzyme activities of 3- hydroxyl-acyl dehydrogenase (HAD) and citrate synthase (CS) displayed similar increases in activity in both control and IT animals. We conclude that QEMG analysis is a more sensitive tool to monitor training adaptation in an early stage than muscle enzyme activities. Furthermore, we observed that IT, as applied in this study, led to a normal training adaptation rather than mal-adaptation in skeletal muscle that was more prominent in QEMG variables than in biochemical analysis.