Cardiac Adaption To Isometric Exercise In Distance Runners And Weight Lifters

I.D. Wallach*, G.W. Gleim, FACSM, N. Marino*, N. Stachenfeld, B. Glace, P. Magnusson, N. Coplan, J.A. Nicholas.

NISMAT and Cardiology Section, Lenox Hill Hospital, NY, NY.

Left ventricular hypertrophy relative to lean body mass has been shown to be greater in distance runners (DR) than in weight lifters (WL), (Longhurst et. Al. 1980). We studied whether this anatomic difference results in a different functional response to maximal isometric exercise of a large muscle group in addition to the Valsalva maneuver. Nine male distance runners (mileage > 30miles/week) and six male weight lifters (lifting > 6 hours/week) had 2-D echocardiography performed at rest, during Valsalva maneuver alone, and during maximal knee extension exercise with Valsalva. Runners had a significantly increased left ventricular mass/lean body mass compared to weight lifters (4.2 +/-.2 g/kg vs. 3.3 +/-.4 g/kg, p=.038). Results are expressed as mean +/- SEM.

                       REST     VALSALVA    EXERCISE
End-Diastolic  DR   143 +/- 6  132 +/- 6   112 +/- 9*
 Volume (ml)   WL   140 +/- 14 138 +/- 10  117 +/- 9*
End-Diastolic  DR    43 +/- 2   36 +/- 4    34 +/- 5
 Volume (ml)   WL    49 +/- 7   45 +/- 8    43 +/- 7
Stroke Volume  DR    99 +/- 7   96 +/- 6    77 +/- 7*
     (ml)      WL    91 +/- 9   93 +/- 5    75 +/- 7*
         *P < .01, compared to REST and VALSALVA.

VALSALVA did not result in significant changes for either group. EXERCISE resulted in a significant decrease in end-diastolic volume and stroke volume for both groups, while there was no significant change in end-diastolic volume. The decline in stroke volume with isometric exercise combined with Valsalva is due to a decline in end-diastolic volume, not to declining contractility, since end-systolic volume is maintained despite the increased afterload of isometric exercise. Although weight lifters experience isometric stress frequently during training, cardiac adaptation to isometric stress was similar in both groups.

Med. Sci. Sports Exerc., Vol. 24(5):s30, 1992.