Issn Print: 0195-9131
Publication Date: 1997/05/01
DIFFERENT PREDICTORS OF MAXIMAL EXERCISE STROKE VOLUME IN TRAINED AND UNTRAINED SUBJECTS 285
P. A. Derchak; T. P. Gavin; J. M. Stager
Excerpt
Stroke volume (SV) plays a fundamental role in determining maximal cardiac output, but is difficult to measure during heavy exercise. In order to identify the best non-exercising predictor of max stroke volume for both trained (TR) and untrained (UT) groups, 24 healthy male subjects were recruited into TR (VO2max 61.8 ± 4.3 mlO2/kg/min, n=14) and UT (VO2max 47.9 ± 8.6 mlO2/kg/min, n=10) based on average weekly activity (TR ≥ 4 exercise bouts/week: UT ≤ 2 exercise bouts/week). Subjects performed an incremental progressive VO2max test on an upright cycle ergometer throughout which impedance cardiography data was collected. Prior to the test supine (SVsup), upright resting(SVrest), and heart rate measurements were taken. All impedance cardiography values were calculated using the equation developed by Kubicek. SVsup and SVrest data was collected following 5-6 minutes quiet rest and lasted approximately 4 minutes each. Data was collected during each minute of the VO2max test and the relationship between VO2 and Q was used to develop a regression line for each subject from which maximal SV(SVmax) was calculated. Regression was employed to allow the use of thoracic impedance despite signal noise during the heavier workloads. All SV values are reported as ml/kg/bt as suggested by Faulkner (1977). SVMax estimates were also made using Faulkner's equation (SVFaulk). SVrest was significantly smaller than any other condition (p < 0.05) and SVmax was not different from SVFaulk for TR. However, SVFaulk was less than SVmax for UT (1.61 ± 0.19 ml/kg/bt vs 1.79 ± 0.23 ml/kg/bt). Independent groups t-tests showed that the TR group had greater SVmax/kg (2.17 ± 0.34 ml/kg/bt vs. 1.79± 0.23 ml/kg/bt) and Q/kg (404.17 ± 55.73 ml/kg/min vs. 342.95± 53.35 ml/kg/bt). The UT group had no significant difference between SVmax and SVSup (1.79 ± 0.23 ml/kg/bt vs. 1.60 ± 0.33 ml/kg/bt p=0.232), which supports the findings of Bevergaard (1960). For the TR group the best predictor of SVmax was SVrest as indicated by the relationship SVmax/kg = (SVrest/kg * 0.8082) + 1.268 (r=0.56). In contrast to generally accepted practice, SV did not plateau in TR until 80% VO2max, whereas UT stroke volume plateaued at 60% VO2max. The results indicate that SVSup is a potential estimate of SVMax in untrained individuals while SVRest may be a predictor of SVmax in trained people.
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