Physical fitness and cardiovascular regulation

Mechanisms of orthostatic intolerance

B. D. Levine, J. C. Buckey, J. M. Fritsch, C. W. Yancy, D. E. Watenpaugh, P. G. Snell, L. D. Lane, D. L. Eckberg, C. G. Blomqvist

Research output: Contribution to journalArticle

109 Citations (Scopus)

Abstract

We studied three groups of eight men each - high, mid, and low fit (peak O2 consumption 60.0 ± 0.8, 48.9 ± 1.0, and 35.7 ± 0.9 ml·min-1·kg-1) - to determine the mechanism of orthostatic intolerance in endurance athletes. Tolerance was defined by progressive lower body negative pressure (LBNP) to presyncope. Maximal calf vascular conductance (G(max)) was measured. The carotid baroreflex was characterized using both stepwise R-wave-triggered and sustained (2 min) changes in neck chamber pressure. High-fit subjects tended to have lower LBNP tolerance than mid- and low-fit subjects but similar baroreflex responses. Subjects with poor LBNP erance had larger stroke volumes (SV) (120 ± 6 vs. 103 ± 3 ml) and greater decline in SV with LBNP to -40 mmHg (40 ± 2 vs. 26 ± 4%). Stepwise multiple linear regression analysis revealed that G(max) and steady-state gain of the carotid baroreflex contributed significantly toward explaining interindividual variations in LBNP tolerance. Thus endurance athletes may have decreased LBNP tolerance, but apparently not as a simple linear function of aerobic fitness. Orthostatic tolerance depends on complex interactions among functional characteristics that appear both related (G(max) and SV) and unrelated (baroreflex function) to fitness or exercise training.

Original languageEnglish (US)
Pages (from-to)112-122
Number of pages11
JournalJournal of Applied Physiology
Volume70
Issue number1
StatePublished - 1991

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Orthostatic Intolerance
Lower Body Negative Pressure
Physical Fitness
Baroreflex
Stroke Volume
Athletes
Syncope
Blood Vessels
Linear Models
Neck
Regression Analysis
Exercise
Pressure

ASJC Scopus subject areas

  • Endocrinology
  • Physiology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

Cite this

Levine, B. D., Buckey, J. C., Fritsch, J. M., Yancy, C. W., Watenpaugh, D. E., Snell, P. G., ... Blomqvist, C. G. (1991). Physical fitness and cardiovascular regulation: Mechanisms of orthostatic intolerance. Journal of Applied Physiology, 70(1), 112-122.

Physical fitness and cardiovascular regulation : Mechanisms of orthostatic intolerance. / Levine, B. D.; Buckey, J. C.; Fritsch, J. M.; Yancy, C. W.; Watenpaugh, D. E.; Snell, P. G.; Lane, L. D.; Eckberg, D. L.; Blomqvist, C. G.

In: Journal of Applied Physiology, Vol. 70, No. 1, 1991, p. 112-122.

Research output: Contribution to journalArticle

Levine, BD, Buckey, JC, Fritsch, JM, Yancy, CW, Watenpaugh, DE, Snell, PG, Lane, LD, Eckberg, DL & Blomqvist, CG 1991, 'Physical fitness and cardiovascular regulation: Mechanisms of orthostatic intolerance', Journal of Applied Physiology, vol. 70, no. 1, pp. 112-122.
Levine BD, Buckey JC, Fritsch JM, Yancy CW, Watenpaugh DE, Snell PG et al. Physical fitness and cardiovascular regulation: Mechanisms of orthostatic intolerance. Journal of Applied Physiology. 1991;70(1):112-122.
Levine, B. D. ; Buckey, J. C. ; Fritsch, J. M. ; Yancy, C. W. ; Watenpaugh, D. E. ; Snell, P. G. ; Lane, L. D. ; Eckberg, D. L. ; Blomqvist, C. G. / Physical fitness and cardiovascular regulation : Mechanisms of orthostatic intolerance. In: Journal of Applied Physiology. 1991 ; Vol. 70, No. 1. pp. 112-122.
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