Abstract
BACKGROUND: Acute physical activity often induces an acute reduction in pain sensitivity known as exercise induced hypoalgesia (EIH). The aim of this study was to investigate the effects of a high intensity functional training (HIFT) on EIH compared to a control session. METHODS: 50 (age: 26.0 ± 2.7; 23 female) participants successfully conducted this study consisting of a pre-experimental test as well as a 12-minute HIFT (body-weight exercises) and a 12-minute control (supervised breathing) session in a randomized crossover design. Pre and post, pressure pain thresholds (PPT) were measured at the ankles, knees, elbows, and forehead. RESULTS: The HIFT resulted in a relative maximum and average heart rate of 96.2% (± 3.6%) and 91.1% (± 4.2%), respectively, and maximum and average RPE values of 19.1 (± 1.2) and 16.2 (± 1.4), respectively. Results reveal a significant 'Intervention' × 'Time point' interaction (p < 0.001) for PPT (pooled for one average value) with hypoalgesia observed following the HIFT (p < 0.001; pre: 56.0 ± 16.8, post: 61.6 ± 19.0 [Newton]) and no change following the control (p = 0.067; pre: 56.6 ± 18.4, post: 55.3 ± 18.9 [Newton]). Further, a significant 'Time' × 'Intervention' × 'Landmark' interaction effect (p = 0.024) is observed and all landmarks showed significant hypoalgesia following HIFT (p < 0.01), except for the right elbow and forehead. Following control, no hypoalgesia was observed at any landmark. Analysing male and female participants separately, it was observed that EIH occured only in men. CONCLUSION: A HIFT using bodyweight exercises reduces pain sensitivity. Hence, combining strength and aerobically demanding exercises in a short but high intensity manner, as done in HIFT, can be seen as a usable tool to induce hypoalgesia. Yet, these results were observed only in male participants, necessitating future sex-specific research. TRIAL REGISTRATION: DRKS00034391, retrospectively registered on the 4th of June 2024.