Int J Sports Med 1992; 13(8): 562-566
DOI: 10.1055/s-2007-1024565
© Georg Thieme Verlag Stuttgart · New York

A Comparison of the Blood Lactate and Plasma Catecholamine Thresholds in Untrained Male Subjects

D. A. Schneider, M. E. McGuiggin, G. H. Kamimori
  • Human Performance Laboratory, Department of Cardiopulmonary Sciences, Northeastern University, Boston, MA 02115 and the Department of Behavioral Biology, Walter Reed Army Institute of Research, Washington, D.C. 20307-5100
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Publication History

Publication Date:
14 March 2008 (online)

Abstract

The relationships between the plasma epinephrine threshold (TE), the norepinephrine threshold (TNE), and the blood lactate threshold (Tlact) were examined during incremental cycling in 10 untrained male subjects. When oxygen uptake (V̇O2) measured at each threshold was expressed as a percent of V̇O2max, the thresholds occurred at 40.8 ± 2.4%, 45.5 ± 3.0%, and 46.6 ± 3.0% for Tlact, TE, and TNE, respectively. The average V̇O2 and power output values obtained at the lactate and epinephrine thresholds were not found to be significantly different (p < 0.10). However, Tlact and TE occurred simultaneously in six subjects, whereas TE occurred at a higher work stage than Tlact in the other four subjects. The mean V̇O2 and power output values determined at TNE were found to be significantly greater than the values obtained at Tlact (p < 0.05). These two thresholds occurred together in four subjects, while TNE was observed to occur at a higher work stage than Tlact in the other six subjects. None of the differences between TE and TNE were significantly different. Although plasma norepinephrine concentrations were much greater than those for epinephrine at a given power output, the two catecholamine thresholds occurred simultaneously in seven subjects. The results are not consistent with the hypothesis that the increase in plasma catecholamine levels during incremental exercise is the sole determinant of the lactate threshold. It is also possible that a decrease in muscle pH, due to increased lactic acid, stimulated a reflex increase in sympathetic outflow and a subsequent rise in catecholamine levels.

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