Sprint Interval Training Attenuates Neuromuscular Function and Vagal Reactivity Compared With High-Intensity Functional Training in Real-World Circumstances

Abstract Benítez-Flores, S, de S. Castro, FA, Lusa Cadore, E, and Astorino, TA. Sprint interval training attenuates neuromuscular function and vagal reactivity compared with high-intensity functional training in real-world circumstances. J Strength Cond Res 37(5): 1070–1078, 2023—The aim of this study was to compare the acute cardiovascular and neuromuscular effects of 3 time-matched sessions of high-intensity training. Eighteen moderately active adults (9 women and 9 men [age: 23 ± 2.9 years; maximum oxygen consumption (V̇o 2max): 47.6 ± 4.1 ml·kg−1·min−1]) performed three low-volume (∼9 minutes) sessions in a randomized order: sprint interval training (SIT), burpee interval training (BIT) (10 × 5 seconds efforts × 35 seconds recovery), and vigorous intensity continuous training (VICT) (6 minutes 5 seconds of running at ∼85% of peak heart rate [HRpeak]). Indices related to heart rate (HR), neuromuscular performance (counter movement jump height [CMJheight] and squat and bench press power), and autonomic balance (heart rate recovery and heart rate variability [HRR and HRV] )were monitored during exercise. Sprint interval training and VICT elicited a higher HRmean (171.3 ± 8.4 and 166.5 ± 7.5 vs. 150.5 ± 13.6 b·min−1, p < 0.001) and time of ≥90%HRpeak (133.3 ± 117.4 and 110 ± 128.9 vs. 10 ± 42.4 seconds, p < 0.01) than BIT. Sprint interval training exhibited a slower HRR and lower HRV than BIT and VICT (p < 0.05) postsession. Moreover, only SIT resulted in a significant decline (p < 0.01) in CMJheight (34.7 ± 7.2 to 33.5 ± 7.2 cm), relative squat mean power (25.5 ± 4.5 to 23.8 ± 4.9 W·kg−1), and relative bench press peak power (6.9 ± 2.4 to 6.2 ± 2.5 W·kg−1). Results revealed that SIT diminishes the sympathovagal reactivation and neuromuscular performance compared with work-matched BIT and VICT.