Real-world efficacy of equipment-free reduced-exertion high-intensity interval training in improving physical and mental health in inactive males: A randomized controlled trial

Aim: Although reduced-exertion high-intensity interval training (REHIT) confers well-documented health benefits, most supporting evidence derives from laboratory studies that rely on specialized equipment. This study examined the real-world efficacy of equipment-free REHIT using burpees (BIT) in sedentary young adults. Methods: A 12-week randomized controlled trial (n = 319 inactive men, age 20.5 ± 1.1 years, maximal oxygen uptake [VO_2max] 37.7 ± 1.4 ml/min/kg) compared four cohorts: supervised BIT (n = 79), unsupervised BIT in real-world conditions (BIT-RW; n = 79), supervised cycling-based sprint interval training (SIT; n = 82), and a non-exercising control (CON; n = 79). Exercise groups performed 2 × 20s all-out effort sessions 3–5 times weekly. Training and affective responses were monitored throughout the intervention. Pre- and post-intervention outcomes included body composition, cardiorespiratory fitness, and mental health (stress, depression, anxiety, sleep quality, resilience, and health-related quality of life [QoL]). Results: The supervised BIT achieved 91 %–94 % of maximal heart rate (HR_max), compared to ∼90 % HR_max in BIT-RW. All exercise groups exhibited significant physiological improvements: 6 %–8 % body mass reduction, 8 %–13 % VO_2max increase (η²p = 0.7–0.8, p < 0.001). Additionally, exercise training resulted in significant reductions in stress (49–61 %, p < 0.001), anxiety (37–86 %, p < 0.001), depression (14–48 %, p < 0.001), as well as improvements in resilience (22–27 %, p < 0.001) and QoL (14–27 %, p < 0.001). Supervised BIT matched SIT in VO_2max gains (5.0 ± 0.6 ml/min/kg), while BIT-RW showed smaller physiological benefits (3.0 ± 0.6 ml/min/kg) but 10 % greater improvements in affective responses (p < 0.05). Conclusions: This study demonstrates that a 40-s equipment-free REHIT protocol utilizing burpees improves both physical and mental health outcomes, even when implemented in unsupervised free-living settings. These findings suggest that BIT is an accessible and time-efficient training option for individuals constrained by limited access to equipment or professional oversight.