Moderate exercise after altitude exposure fails to induce decompression sickness

Area of Science:

• Aerospace Medicine
• Physiology
• Environmental Health

Background:

• Current U.S. Air Force guidelines prohibit exercise after altitude exposure due to concerns about decompression sickness (DCS).
• Operational personnel have expressed interest in understanding the risks of post-exposure exercise.
• This study evaluated exercise as a potential stressor for DCS after altitude exposure.

Purpose of the Study:

• To determine the effect of post-exposure exercise on the incidence of subsequent altitude decompression sickness (DCS).
• To investigate whether exercise following altitude exposure could induce delayed-onset or recurring DCS.

Main Methods:

• 67 subjects underwent a 2-hour exposure to 30,000 ft with mild, upper body exercise after 1-hour preoxygenation.
• Venous gas emboli (VGE) were monitored using echo-imaging, and subjects were observed for DCS symptoms.
• Subjects were randomly assigned to either post-exposure rest or moderate exercise (50% peak oxygen uptake) and monitored for delayed/recurring DCS.

Main Results:

• The initial altitude exposure resulted in a 48.3% incidence of DCS among the 60 volunteers.
• In the post-exposure exercise group, 15 subjects developed DCS that resolved during descent.
• No cases of DCS were observed or reported during or after the post-exposure exercise period.

Conclusions:

• Moderate exercise performed after altitude exposure did not lead to delayed-onset or recurring decompression sickness.
• The findings suggest that exercise may not be a significant DCS-inducing stressor in the post-exposure period.
• This research could inform revised safety protocols regarding physical activity after altitude exposure.