First men on the moon

Heart rates averaged 145 to 160 beats/min, sometimes reaching a peak on some flights of 185 beats/min. Medical experts had previously only witnessed such high rates on sick people or people under stress. It was detennined from repeated flight tests, however, that strcss or exertion was not involved and that the high rates were primarily due to psychological factors associated with the excitement of launch and acceleration of the X-15. Such behavior was finally accepted to be non-nal for this kind of activity. Nobody gets concerned, for example, when an astronaut shows similar rates during a launch or reentry sequence. As a matter of interest, Neil Armstrong registered a heart beat of 156 during the first lunar landing.

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(Hallion)
Just one comment on the heart rates and that I hope will lay it to rest. This was sort of a baseline data point. In 1967-68 the U.S. Navy did an interesting series of studies on heart rates on fighter attack pilots in Vietnam, on combat operations over North Vietnam. They were expecting to see an awful lot of stress related to certain points in the mission and they expected these would be things like encountering SAMS, encountering Migs, you know, attacking the target, what not. It turned out actually the highest heart rates that they experienced were during night carrier landings, and the heart rates were higher, in fact, than the heart rates experienced in the X-15 program. Interesting data point.