Accession Number:

ADA162003

Title:

Respiratory Response and Muscle Function during Isometric Handgrip Exercise at High Altitude

Descriptive Note:

Technical Report

Corporate Author:

ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK United States

Report Date:

1985-07-15

Pagination or Media Count:

32.0

Abstract:

The purpose of this investigation was to determine if the hyperventilatory response to fatiguing isometric exercise at sea level could predict resting ventiliation and acute mountain sickness AMS at 4300 m altitude. Exercise consisted of four successive endurance handgrips held to complete fatigue at 40 of maximum isometric handgrip strength MHS. There was no relationship between the magnitude or pattern of exercise-induced hyperventiliation at sea level and the severity of AMS later at altitude. Sea level hyperventilatory response was not predictive of resting ventilation at altitude. Altitude exposure progressively increased both the incidence and magnitude of the hyperventilatory response to exercise and prolonged it for 60-90 s into the recovery period, providing support for the central command theory of ventilatory control during isometric exercise. MHS was significantly increased at altitude, by 11 on day 2 and 16 on day 6. Endurance times to fatigue were reduced, but not always significantly so. A follow-up study involving more practice at sea level demonstrated MHS to be significantly increased throughout an entire 18-day stay at 4300 m and for 3, but not 5, days after descent. Significant changes in endurance could not be demonstrated. Neither AMS nor changes in body weight or circulating norepinephrine levels can account for the temporal pattern of increased grip strength, but the respiratory alkalosis occurring at altitude appears to be a likely mechanism.

Subject Categories:

Distribution Statement:

APPROVED FOR PUBLIC RELEASE