He attributes these feats to training with his Wim Hof Method (WHM).

He has accumulated 20 “world records” for feats such as standing in a container while covered with ice cubes for 2 h, climbing Mount Kilimanjaro in shorts, swimming 60 m underneath ice, and running a half marathon barefoot on snow and ice north of the Arctic Circle (Hof, 2020c). Wim Hof is a Dutch athlete, nicknamed “Iceman” for his ability to withstand freezing temperatures. These findings indicate that despite large physiological effects, a single WHBM session does not improve anaerobic performance in repeated sprinting exercise. Upon completion of RAST, 8 min cumulated expired carbon dioxide volumes in the WHBM and HV were greater than in SB, suggesting lingering carbon dioxide stores depletion. Upon the last HV in the WHBM and HV conditions, end-tidal CO 2 partial pressure (PETCO 2) values were 19 ± 3 and 17 ± 3 mmHg, indicative of respiratory alkalosis with estimated arterial pH increases of +0.171 and of +0.181, respectively. Finger SpO 2 dropped to 60 ± 12% at the end of the BHs. Despite large physiological effects in the SpO 2 and expired carbon dioxide (VCO 2) levels of both HV and WHBM, no significant positive or negative condition effects were found on RAST peak power, average power, or fatigue index. Gas exchange, heart rate, and finger pulse oxygen saturation (SpO 2) were monitored. Fifteen amateur runners performed a single WHBM session prior to a Repeated Ability Sprint Test (RAST) in comparison to voluntary HV or spontaneous breathing (SB) (control) in a randomized cross-over design. We determined the feasibility of implementing a single WHBM session before repeated sprinting performance and evaluated any acute ergogenic effects.

It has been increasingly adopted by coaches and their athletes to improve performance, but there was no published research on its effects. The Wim Hof breathing method (WHBM) combines periods of hyperventilation (HV) followed by voluntary breath-holds (BH) at low lung volume.

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