Neuromuscular and Strength Adaptations to ‘Concurrent’ Training in the Young Recreationally Trained Men

Abstract

The amount of neuromuscular adaptation depends on the characteristics and effectiveness of the exercise prescriptions used in the training program. Thus, each person responds differently to each training program. Therefore, this study aimed to compare the effects of 8 weeks of three distinct “concurrent” training: Traditional Concurrent Training (TCT), Sprint Interval Training (SIT), and High Intensity Resistance Circuit-Based Training (HRC) protocols on neuromuscular and strength performance. Thirty-four young males were recruited (24±5.8 years, 174.9±5.9 cm height, and 73.4±7.9 kg) and randomly assigned to three groups (HRC: 13, SIT: 10, and TCT: 11). All subjects exercised twice a week for 8 weeks. Maximal Voluntary Contraction (MVC), Rate of Force Development (RFD) and H-Reflex, M wave, and 6RM were assessed. Standard descriptive statistics were used to characterize the study population. A mixed analysis of variance with repeated measures and Bonferroni post hoc tests were used to investigate the interaction effect and significant differences. The main results show that significant increment (P<0.05) in MVC and 6RM following HRC and TCT, while both induced increases in RFD but only HRC was significant (P<0.05). However, SIT showed decrement in RFD and H max, whereas leg extension and deadlift only attained significant increment (P<0.05). After comparison of protocols, significant between-group statistical differences were shown in H max, M max and muscle strength in bicep curl following HRC and TCT. HRC induced a small effect size of maximal H-Reflex (ES=0.32), H:M ratio (ES =0.44) with significant increases in MVC and 6RM, it suggests that possible adaptations occurred in efferent motoneuronal output. Probably, slow twitch and fast twitch fatigue-resistant motor units’ activation decreased H reflex, H:M ratio, and RFD after SIT, indicating possible adaptations in neuromuscular function. Remarkably, TCT based training led to an enhanced response at the spinal cord level and muscle contraction velocity. Overall, these observations suggest each training protocol induced more or less strength adaptation associated with spinal reflex specifically to the training demands