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Back to play of athletes after exertional heat stroke.

A recurrent exertional heat stroke (EHS) in an endurance athlete and a protocol for return to play were described by Johnson et al. (2). The authors claim that the Israel Defense Forces (IDF) heat tolerance test (HTT), being in use for more than three decades, is not suitable for elite endurance athletes. We suggest that the presented case emphasizes the importance to undergo a HTT after EHS to reduce the risk for recurrent EHS, as was shown already in a similar case of recurrent EHS (4). In the presented case, the athlete was not qualified to return to practice after the first episode, although the athlete could endure a race under mild environmental conditions. According to the IDF protocol, he would have been suspended from endurance field exercises until passing the test after the recovery of the thermoregulatory system, which in most cases takes 6 to 8 wk (7). Expectedly, 16 months after the second EHS episode, the athlete’s thermoregulatory mechanism fully recovered and he endured a triathlon under heavy heat load. It was debated that the HTT reflects an acute response and does not account for organ function (5), or for the state of acclimation (1). The IDF-HTT is taken only after full medical clearance (and with normal laboratory values). The argument that organ failure still exists long after recovery was shown only in a non-EHS mice model (5) and was not established in humans. The IDF-HTT protocol challenges the thermoregulatory response but enables its completion (7). Noteworthy, tests that were performed by unacclimatized (winter) or acclimatized (summer) individuals revealed the same results. A negative test qualifies to return to duty/practice. A positive result on the first HTT, which happens in about 10% of the cases, requires another HTT 3 months later; consequently the rate of failure is G2%. This highlights the following: (a) EHS possibly results with a temporary heat intolerance (HI); (b) intersubject variability exists in recovery time of the thermoregulatory system; (c) high sensitivity of the IDF-HTT. Noteworthy, no recurrent EHS was reported in individuals who fully returned to active duty after being qualified as heat tolerant. Likewise no heat stroke-related sequel was reported in these individuals. The protocol suggested by Johnson et al. is based on a 2-wk acclimation protocol and an intense exercise. We argue that the reported case does not justify the necessity to revisit the IDF-HTT protocol that is based on a 2-h exercise heat stress protocol. The athlete could not sustain more than 45 min in the first test and 70 min during the second test (2). The only drawn conclusions from this case are as follows: (a) an acclimation effect was achieved and (b) the exercise heat stress was too intense and overchallenging. In conclusion, we argue that passing a valid HTT is a prerequisite for return to duty/play. We believe that the IDFHTT is adequate and sensitive to this goal; this is supported by others (3,6). We are aware of the logistic burden in performing a HTT that requires a climatic chamber, and we encourage the development of other modalities.