1. In this systematic review and meta-analysis, high intensity interval training (HIIT) led to small improvements in overall mental wellbeing compared to other forms of exercise in healthy populations and those with physical illnesses.
2. Compared to no exercise, those who participated in HIIT had moderate improvements in mental wellbeing, depression severity, and perceived stress compared to inactive individuals.
Evidence Rating Level: 1 (Excellent)
Compared to the general population, those who suffer from physical illness are known to suffer from higher rates of depression, anxiety and stress. High intensity interval training (HIIT) has been recently popularized due to its ability to achieve similar benefits compared to lower intensity sessions. However, due to the paucity of data on this topic, the aim of this systematic review and meta-analysis was to investigate the mental health benefits of HIIT in both healthy populations and those with physical illnesses, and to compare its effects to non-exercising individuals (non-active controls) and those performing other forms of exercise (active controls).
From 3659 screened records, 58 studies (3038 participants) were included from the database’s inception to July 2020. Included studies evaluated all forms of HIIT on mental health outcomes in healthy populations and those with physical illnesses. Studies reporting patients with a structural mental health diagnosis were excluded. The quality of the evidence was assessed through the Grading of Recommendations, Development and Evaluation criteria. Mental health outcomes were measured using the Mental Component Summary (MCS) score.
The results of this study demonstrated that HIIT leads to improvements in mental well-being, depression severity, and perceived stress compared with those who didn’t exercise. In addition, HIIT showed small improvements in mental health compared to active controls. It was also suggested that HIIT may improve psychological distress and sleep compared to non-exercising individuals; however, few RCT’s reported this finding. This study was limited by the mixed quality of the included studies which may limit interpretability. However, the study’s inclusion of a wide variety of physical conditions that hold a high mental health burden holds promise that HIIT may have a larger therapeutic role in the near future.
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