Differences in Electromechanical Delay Subsequent to Neuromuscular Fatigue: A Potential Relationship to Physical Fitness Training

Background: lower body strength is a vital factor in combat sports success. When combat sport athletes (CSA) performing workouts, leg muscles occupied in all technical, tactical, and movements actions. The prevalence of non-contact injuries in CSA and non-athlete remains high. As muscular strength contributes to joint constancy, neuromuscular fatigue is considered as a danger factor for noncontact impairments. Purpose: To examine and compare the impacts of fatiguing on electromechanical in 3 different physical fitness training groups (CSA, healthy, and sedentary). Study design: Randomized controlled laboratory study. Methods: Ninety male participants (mean ± SD: age = 22.16 ± 3.51) were included and divided into three groups each of 30 individuals (30 combat sport athletes [Boxing=10; Kickboxing=7; Taekwondo=5; Karate=5; Judo=4], 30 healthy individuals, and 30 sedentary individuals). Evaluation of EMD was performed pre-and-post fatiguing protocol using Biodex System isokinetic dynamometer and wireless 8-channel Delsys electromyography (EMG) telemetry system. The three groups performed periodical intermittent contractions utilizing a 0.6 duty cycle, including 6 s contraction followed by 4 s relaxation at 60% of maximum voluntary contractions till task-incompetence. Results: Repeated measures analysis of the variance (RMANOVA) was utilized to measure the main effect of time (pre-and-post-fatigue), speed (60, 180, and 300 ˚/s), within the physical condition (CSA, healthy, and sedentary), and interaction between them on EMD. In all three studied groups, EMD was consistently increasing (p<0.001) after increasing the speed. Main effect (p<0.001) for time and speed was detected across entire muscle groups. Also, significant interaction effect (p<0.001) between time and speed in all muscle groups. Irrespective of muscle, speed or time, mean EMD was greater in the sedentary group in comparison to CSA group (p<0.001) and healthy group (P = 0.011) respectively. Conclusion: The results reinforce that neuromuscular fatigue significantly increases EMD, which might lead to augment risk factors for injuries. Elevated rate of lower EMD were induced by physical condition. Raising angular velocity might affect neuromuscular functioning, causing a reduction of joints stability, and might to injuries. The increased electromechanical delay can affect maximal performance then augment the risk of injuries whether in CSA or others. Joining sport team physical fitness training sessions is a great prevention factor than being sedentary.