The neuromuscular, biochemical, and endocrine responses to a single-session vs. double-session training day in elite athletes

Purpose: The aim of this study was to compare the acute neuromuscular, biochemical, and endocrine responses of a training day consisting of a speed session only to performing a speed and weight training session on the same day. Methods: Fifteen male academy level rugby players completed two protocols in a randomized order. The speed only protocol involved performing 6 maximal effort repetitions of 50m running sprints with 5 minutes recovery between each sprint, while the speed and weights protocol involved the same sprinting session but was followed 2h post by a lower body weights session consisting of 4 sets of 5 back squat and Romanian deadlift at 85% 1RM. Testosterone, cortisol, creatine kinase, lactate, and perceived muscle soreness were determined immediately before, immediately after, 2h post, and 24h post both protocols. Peak power, relative peak power, jump height, and average rate of force development were determined from a counter movement jump (CMJ) at the same time points. Results: At 24h post, muscle soreness was significantly higher following the speed and weights protocol compared to speed only protocol (effect size eta2= .253, F=4.750, p < 0.05). There was no significant difference between any of the CMJ variables at any of the post training time points. Likewise creatine kinase, testosterone, and cortisol were unaffected by the addition of a weight training session. Conclusion: These data indicate that the addition of a weight training session 2h post a speed session, while increasing the perception of fatigue the following day, does not result in a difference in endocrine response or in neuromuscular capability