(Over)training effects on quantitative electromyography and muscle enzyme activities in standardbred horses

Abstract

To study whether quantitative needle electromyography (QEMG) is more sensitive to detect training (mal)adaptation than muscle enzyme activities, 12 standardbred geldings trained for 32 wk in age-, breed-, and sex-matched fixed pairs. After a habituation and normal training (NT) phase (phases 1 and 2, 4 and 18 wk, respectively), with increasing intensity and duration and frequency of training sessions, an intensified training (IT) group (phase 3, 6 wk) and a control group (which continued training as in the last week of phase 2) were formed. Thereafter, all horses entered a reduced training phase (phase 4, 4 wk). One hour before a standardized exercise test (SET; treadmill), QEMG analysis and biochemical enzyme activity were performed in muscle or in biopsies from vastus lateralis and pectoralis descendens muscle in order to identify causes of changes in exercise performance and eventual (mal)adaptation in skeletal muscle. NT resulted in a significant adaptation of QEMG parameters, whereas in muscle biopsies hexokinase activity was significantly decreased. Compared with NT controls, IT induced a stronger adaptation (e.g., higher amplitude, shorter duration, and fewer turns) in QEMG variables resembling potentially synchronization of individual motor unit fiber action potentials. Despite a 19% decrease in performance of the SET after IT, enzyme activities of 3-hydroxyacyl dehydrogenase and citrate synthase displayed similar increases in control and IT animals. We conclude that 1) QEMG analysis is a more sensitive tool to monitor training adaptation than muscle enzyme activities but does not discriminate between overreaching and normal training adaptations at this training level and 2) the decreased performance as noted in this study after IT originates most likely from a central (brain) rather than peripheral level. equine; motor unit action potential analysis; training adaptation; muscle metabolism; enzymology; overreaching THE AIM OF PHYSICAL TRAINING is to increase performance capacity by gradually increasing both duration and intensity of the exercise bouts. Each exercise session induces, dependent on the total training load, disturbances in cellular homeostasis. If the training load is balanced with the individual's exercise tolerance, regenerative processes will restore or increase athletic performance within a couple of days (35,36,39,40). In this situation adaptive processes result in, among others, increments in aerobic key enzymes in skeletal muscle (32) or excitability after endurance, strength, or sprint training (7,23,25,28,29) . However, sustained vigorous training, often coupled with other stressors, may result in incomplete recovery, and decrement rather than improvement or maintenance of performance will occur. This process is termed overreaching, which might lead to the more severe chronic situation called overtraining (33,40).Since overtraining and, to a lesser extent, overreaching are severe conditions leading to decreases in performance capacity for several weeks to several months, this obviou...

Surface Electromyography During Both Standing and Walking in m. Ulnaris lateralis of Diversely Trained Horses

“…In a recent study it was shown that exercise positively influences hypertrophy and neuromuscular excitability in humans and horses (Mileva et al, 2010;Wijnberg et al, 2008). Indeed, both of these authors found an increase in amplitude with exercise, a finding that is in agreement with the present study (see Figure 2).…”

“…The short yet coordinated bursts of sEMG signal activity in the HW horses in the present study reflects a training induced synchronization of the individual compound muscle action potentials (CMAPs) within the UL muscle measured (Mileva et al, 2010;Wijnberg et al, 2008).…”

Effect of head and neck position on outcome of quantitative neuromuscular diagnostic techniques in Warmblood riding horses directly following moderate exercise

“…The increases in number of turns in HNP4 and HNP7 and duration in HNP7, suggest a less synchronous arrival of the individual motor unit action potentials of which the recorded motor unit action potential is composed (Gabriel et al . 2006; Wijnberg et al . 2008), which is in agreement with the results of the single fibre EMG.…”

“…In addition training adaptation can also be elucidated using this technique (Gabriel et al . 2006; Wijnberg et al . 2008).…”

“…Quantitative electromyography (QEMG) has proved to be useful in revealing myopathy or neuropathy at various stages of disease (Sonoo and Stålberg 1993;Montagna et al 2001;Wijnberg et al 2002aWijnberg et al , 2003aWijnberg et al , 2004Wijnberg et al , 2006Fuglsang-Frederiksen 2006;Daube and Rubin 2009). In addition training adaptation can also be elucidated using this technique (Gabriel et al 2006;Wijnberg et al 2008). In human medicine, 2 types of tests are commonly used to study neuromuscular transmission, repetitive nerve stimulation and single fibre (SF) EMG (Stålberg and Trontelj 1997).…”