ACKNOWLEDGMENTS

earlier, Edwards (10) in his initial study showed that subjects who had not been at high altitude long enough for good acclimatization had higher maximum blood lactate levels than well-acclimatized subjects. The data in Fig. 1 predict that there would be no rise in blood lactate concentration on maximal exercise above the resting level at altitudes above 7,600 m and indeed the highest data point (6) seems to confirm this. It is very extraordinary that under these conditions of extreme tissue hypoxia, blood lactate levels are so different from those seen in acute hypoxic exposure. Irrespective of whether this strange state of affairs does not occur in everybody (although the data in Fig. 1 are from a large number of subjects including both acclimatized lowlanders and high-altitude residents), and there may be some recovery of blood lactate levels with increased time spent at high altitude, this extreme reduction in blood lactate is cer-tainly intriguing