Ischemic Preconditioning of One Forearm Enhances Static and Dynamic Apnea

AB Introduction: Ischemic preconditioning enhances ergometer cycling and swimming performance. We evaluated whether ischemic preconditioning of one forearm (four times for 5 min) also affects static breath hold and underwater swimming, whereas the effect of similar preconditioning on ergometer rowing served as control because the warm-up for rowing regularly encompasses intense exercise and therefore reduced muscle oxygenation. Methods: Six divers performed a dry static breath hold, 11 divers swam underwater in an indoor pool, and 14 oarsmen rowed "1000 m" on an ergometer. Results: Ischemic preconditioning reduced the forearm oxygen saturation from 65% +/- 7% to 19% +/- 7% (mean +/- SD; P < 0.001), determined using spatially resolved near-infrared spectroscopy. During the breath hold (315 s, range = 280-375 s), forearm oxygenation decreased to 29% +/- 10%; and in preparation for rowing, right thigh oxygenation decreased from 66% +/- 7% to 33% +/- 14% (P < 0.05). Ischemic preconditioning prolonged the breath hold from 279 +/- 72 to 327 +/- 39 s, and the underwater swimming distance from 110 +/- 16 to 119 +/- 14 m (P < 0.05) and also the rowing time was reduced (from 186.5 +/- 3.6 to 185.7 +/- 3.6 s; P < 0.05). Conclusions: We conclude that while the effect of ischemic preconditioning (of one forearm) on ergometer rowing was minimal, probably because of reduced muscle oxygenation during the warm-up, ischemic preconditioning does enhance both static and dynamic apnea, supporting that muscle ischemia is an important preparation for physical activity.