Accession Number:

ADA230454

Title:

Enhancing the Tolerance to +Gz Acceleration by Optimizing the Use of Isometric Contractions in Combination with Straining Maneuvers

Descriptive Note:

Final rept. Oct 1986-Sep 1987

Corporate Author:

EAST TENNESSEE STATE UNIV JOHNSON CITY DEPT OF PHYSIOLOGY

Report Date:

1990-08-01

Pagination or Media Count:

49.0

Abstract:

Experiments were performed on 9 male subjects who exerted L-1 straining maneuvers in a pilot chair apparatus with a seatback at 30 and a spine-to-thigh angle of 110. The L-1 maneuvers were performed with or without simultaneous application of isometric contractions. Contractions were exerted at high levels of force in either a sustained fashion or in an intermittent fashion, in 15 sec periods, until fatigue occurred. Isometric contractions were exerted by either the forearm flexors handgrip, quadriceps, or jaw muscles at tensions of 70 MVC handgrip, quadriceps or 100 MVC jaw. During the experiments, changes in arterial pressure, heart rate and electromyographic activity, from the intercostals and the contracting muscle group, were recorded. During the L-1 maneuver along, mean blood pressure MBP increased to 205 mmHg initially at the onset of the maneuver, but then fell by 50 mmHg, to 155 mmHg during the first 5 seconds of the procedure. The MBP recovered to 170 mmHg and remained at this level during the last 5 sec of the procedure. When isometric contractions were simultaneously applied, initial MBP were essentially the same as with the L-1 maneuver alone, but there was significantly higher MBP maintained throughout the remainder of the L-1 procedure with the isometric contractions, such that MBP averaged almost 30 mmHg higher during the last 5 sec of the procedure.

Subject Categories:

  • Aircraft
  • Medicine and Medical Research

Distribution Statement:

APPROVED FOR PUBLIC RELEASE