The effects of body hydration on perceptual responses during blood flow restriction exercise

Blood flow restriction (BFR) training has emerged as a novel modality with clinical potential. However, BFR increases perceived effort and pain, highlighting the need to identify factors influencing perceptual responses to optimize its practical application. Hypohydration similarly increases discomfort during exercise or painful stimuli, but whether this interacts with BFR is unknown. The purpose of the study was to determine if hydration affects the perceptual response to BFR exercise. Of the 34 participants recruited, 17 (7 females) completed two BFR exercise bouts: (1) Hydrated (regular fluid intake) and (2) Hypohydrated (24 h fluid restriction). Rating of perceived exertion (RPE) and leg pain were recorded throughout. With hypohydration, urine specific gravity increased (Hydrated = 1.01 ± 0.009, vs. Hypohydrated = 1.025 ± 0.002, p < 0.0001), body mass decreased (-2.3 ± 0.7%, p  < 0.0001), and plasma volume decreased (-7.0 ± 3.4%, p  < 0.0001). Similar RPE and leg pain were reported during BFR exercise (RPE: 10.6 ± 0.9, vs. 11.1 ± 0.9, p = 0.054, leg pain: 3.5 ± 1.1, vs. 3.8 ± 1.2, p = 0.2). Similarly, during the rest periods, there was a minimal effect for RPE (9.1 ± 1, vs. 9.5 ± 1.3, p = 0.1) and leg pain (3.1 ± 1.5, vs. 3.6 ± 1.8, p = 0.09). Preliminary analyses show minimal sex differences in perceptual responses, with hydration status changes unrelated to BFR perception. Thus, hydration status has little impact on perceptual responses to BFR exercise.