The Effects of High-Intensity Functional Training With a Respiratory Muscle Training Device on Performance, Mood, and Ventilatory Function

Abstract Chandler, AJ, Martin-Diala, C, Mastrofini, GF, Stray-Gundersen, S, Artsinger, R, Nakagawa, N, and Arent, SM. The effects of high-intensity functional training with a respiratory muscle training device on performance, mood, and ventilatory function. J Strength Cond Res XX(X): 000–000, 2026—Respiratory muscle training (RMT) may enhance exercise performance by delaying respiratory muscle fatigue. This study examined the effects of performing an RMT protocol during high-intensity functional training (HIFT) on pulmonary function, exercise performance, and psychometrics. Twenty-six volunteers (age = 22.4 ± 1.9 years, BMI = 23.8 ± 3.0 kg·m −2 ) were randomized into an RMT or control group and completed three 30-minute HIFT sessions per week for 6 weeks. Each session included 4 rounds of 6 exercises using a 30:30-second work-to-rest ratio, with 2.5 minutes of rest between rounds. Pretesting and posttesting occurred across 3 days. On day 1, the Pittsburgh Sleep Quality Index, Positive and Negative Affect Scale, Profile of Mood States, spirometry, body composition, and V̇ o 2 max testing were completed. On day 2, countermovement jump testing and the Wingate Anaerobic Test were performed. On day 3, an 18-minute HIFT-specific test was administered. Repeated-measures analyses of variance and analysis of covariance with baseline V̇ o 2 max as a covariate were used to determine time and group main effects and group-by-time interactions with significance set at p < 0.05 for all analyses. Analysis of covariances revealed group-by-time interaction for forced expiratory volume in 1 second/forced vital capacity approached significance ( p = 0.06; = 0.05). Pittsburgh Sleep Quality Index scores improved, % body fat decreased and fat-free mass increased, V̇ o 2 max improved, and HIFT performance improved over time for both groups ( p < 0.05), with no differences between groups. These results suggest no additive benefits of the RMT device when used during HIFT sessions. Future research should investigate if RMT sessions completed outside of exercise provide benefits beyond those seen with exercise alone.