Task-specific strength increases after lower-limb compound resistance training occurred in the absence of corticospinal changes in vastus lateralis.

NEW FINDINGS: What is the central question of the study? Are corticospinal responses to acute and short-term squat resistance training task-specific? What is the main finding and its importance? A single bout of resistance training increased spinal excitability, but no changes in corticospinal responses were noted following 4 weeks of squat training despite task-specific increases in strength. The present data suggest that processes along the corticospinal pathway of the knee extensors play a limited role in the task-specific increase in strength following resistance training. ABSTRACT: Neural adaptations subserving strength increases have been shown to be task-specific, but responses and adaptation to lower-limb compound exercises such as the squat are commonly assessed in a single-limb isometric task. This two-part study assessed neuromuscular responses to an acute bout (Study A) and 4 weeks (Study B) of squat resistance training at 80% of one-repetition-maximum, with measures taken during a task-specific isometric squat (IS) and non-specific isometric knee extension (KE). Eighteen healthy volunteers (25 ± 5 years) were randomised into either a training (n = 10) or a control (n = 8) group. Neural responses were evoked at the intracortical, corticospinal and spinal levels, and muscle thickness was assessed using ultrasound. The results of Study A showed that the acute bout of squat resistance training decreased maximum voluntary contraction (MVC) for up to 45 min post-exercise (-23%, P < 0.001). From 15-45 min post-exercise, spinally evoked responses were increased in both tasks (P = 0.008); however, no other evoked responses were affected (P ≥ 0.240). Study B demonstrated that following short-term resistance training, participants improved their one repetition maximum squat (+35%, P < 0.001), which was reflected by a task-specific increase in IS MVC (+49%, P = 0.001), but not KE (+1%, P = 0.882). However, no training-induced changes were observed in muscle thickness (P = 0.468) or any evoked responses (P = 0.141). Adjustments in spinal motoneuronal excitability are evident after acute resistance training. After a period of short-term training, there were no changes in the responses to central nervous system stimulation, which suggests that alterations in corticospinal properties of the vastus lateralis might not contribute to increases in strength.

Sodium Bicarbonate Supplementation Delays Neuromuscular Fatigue Without Changes in Performance Outcomes During a Basketball Match Simulation Protocol.

Ansdell, P and Dekerle, J. Sodium bicarbonate supplementation delays neuromuscular fatigue without changes in performance outcomes during a basketball match simulation protocol. J Strength Cond Res 34(5): 1369-1375, 2020-To investigate the development of neuromuscular fatigue during a basketball game simulation and to ascertain whether sodium bicarbonate (NaHCO3) supplementation attenuates any neuromuscular fatigue that persists. Ten participants ingested 0.2 g·kg of NaHCO3 (or an equimolar placebo dosage of sodium chloride [NaCl]) 90 and 60 minutes before commencing a basketball game simulation (ALK-T vs. PLA-T). Maximal voluntary isometric contractions (MVICs) of the knee extensors and potentiated high- (100 Hz) and low- (10 Hz) frequency doublet twitches were recorded before and after each match quarter for both trials. In addition, 15-m sprint times and layup completion (%) were recorded during each quarter. Maximal voluntary isometric contraction, 100- and 10-Hz twitch forces declined progressively in both trials (p ≤ 0.05) with a less pronounced decrease in MVIC during ALK-T (p < 0.01). Both 100- and 10-Hz twitch forces were also significantly greater in ALK-T (p ≤ 0.05). Fifteen-meter sprint time increased over the course of both trials (∼2%, p < 0.01); however, no significant condition or time effect was found for layup completion (p > 0.05). A basketball simulation protocol induces a substantial amount of neuromuscular (reduction in knee extensor MVICs) and peripheral fatigue with a concomitant increase in 15-m sprint time over the protocol. NaHCO3 supplementation attenuated the rate of fatigue development by protecting contractile elements of the muscle fibers. This study provides coaches with information about the magnitude of fatigue induced by a simulated basketball game and provides evidence of the efficacy of NaHCO3 in attenuating fatigue.