Neuromuscular adaptations to single-session combined strength and endurance training in untrained men : an examination of the order effect

Pulverenti, Timothy (2013). Neuromuscular adaptations to single-session combined strength and endurance training in untrained men: An examination of the order effect. Department of Biology of Physical Activity, University of Jyväskylä. Master’s Thesis in Science of Sport Coaching and Fitness Testing. 98 pp. Understanding the adaptations to single-session combined strength (S) and endurance (E) training has received increased attention in scientific literature through the expanding use of combined training programs for practical purposes. However, the intrasession exercise order when performing both E and S in the same training session may limit potential strength development, as the neuromuscular adaptations to either training mode alone are very different. Research on the effect of the intra-session exercise order of combined training on various training-induced adaptations, i.e. the order effect, is currently limited, especially with regard to the neuromuscular adaptations. Therefore, the purpose of this study was to investigate the order effect to single-session combined strength and endurance training on the long-term neuromuscular adaptations. Thirty-two young adult male subjects (29 ± 4 years) completed a 24-week progressive single-session combined strength and endurance-training program. The subjects were split into two groups performing opposite intra-session exercise orders, endurance before strength (E+S; n = 14) or strength before endurance (S+E; n= 18) by pairwise matching of basal maximum strength results. All subjects were tested on three separate occasions (0, 12 and 24 weeks). A group of subjects (n = 8) participated in a two-week control period performed before week 0 (-2 to 0 weeks) to ensure reproducibility and stability of important dependent variables. Maximal voluntary activation (VA), surface electromyography (sEMG), one-repetition maximum concentric strength (1-RM), maximal voluntary isometric force (MVC) and rapid force production (AV500) of the leg extensors and flexors were evaluated. No changes occurred in strength during the two-week control period, while after the 24week training period significant increases in 1-RM load of 13% (p<0.001) and 17% (p<0.001), knee extension MVC of 7% (p<0.05) and 14% (p<0.01) and leg press MVC of 15% (p<0.01) and 13% (p<0.01) were observed for E+S and S+E, respectively. There were no significant between group differences in strength gains. After 24 weeks a significant increase took place in VA of quadriceps femoris of 4% (p<0.01) in S+E only whereas no significant changes occurred in E+S. There were differences between groups in changes in maximum sEMG activity of the vastus lateralis after 24 weeks as large increases took place in S+E whereas non-significant changes occurred in E+S. The present data provide some evidence of an order effect on training induced adaptations to combined strength and endurance training. Maximum voluntary activation of trained leg muscles appeared to be interfered after training E+S when compared to S+E. Additionally, strength development appeared to be affected by training order as larger strength gains were continually observed for S+E when compared to E+S, however, strength gains were not statistically significant. These findings highlight the importance of combined training order as the level or neural activation governs muscular strength.