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Int J Sports Med 1982; 03(3): 163-168
DOI: 10.1055/s-2008-1026082
© Georg Thieme Verlag Stuttgart · New York

Hormonal and Metabolic Consequences of Prolonged Running at the Individual Anaerobic Threshold*

A. Schnabel, W. Kindermann, W. M. Schmitt, G. Biro, H. Stegmann
  • Abteilung Sport- und Leistungsmedizin (Leiter: Prof. Dr. med. W. Kindermann) und II. Medizinische Poliklinik (Direktor: Prof. Dr. med. K.F. Weinges) der Universität des Saarlandes, Saarbrücken
* Supported by the Bundesinstitut für Sportwissenschaft, Köln-Lövenich.
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Publikationsdatum:
14. März 2008 (online)

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Abstract

To examine the metabolic and hormonal responses to non-exhaustive steady-state exercise at the individual anaerobic threshold (IAT), 12 male physical education students performed treadmill exercise of 50 min duration. The treadmill speed equaled that at the IAT as assessed in a standardized progressive exercise test (75 + 2% of maximal oxygen uptake). Heart rate averaged 177.0 ± 12.2 min-1 at 15 min and 184.5 ± 11.5 min-1 at 50 min.

After the initial adjustment, arterial lactate stabilized at individually different levels between 2.70 and 6.00 mmol/l without any substantial trend in the individual curves. Arterial glucose was unchanged throughout the test. Glycerol increased continuously to 157% above the pre-exercise value (P < 0.001). The FFA blood level was not depressed but rather showed an increasing tendency between 25 and 50 min (P < 0.05). Between 0 and 25 min, insulin decreased (P < 0.01), growth hormone increased to 8 times its pre-exercise value (P < 0.001), and Cortisol did not show any significant changes. Between 25 and 50 min, no significant additional changes were detected for these hormones. At 15 min epinephrine and norepinephrine had increased 2.8- and 7-fold above the respective pre-exercise values (P < 0.001); both catecholamines continued to increase until 50 min (P < 0.001 and P < 0.01).

It is concluded that prolonged exercise at the IAT is associated with a steady-state condition in carbohydrate supply and turnover, as is suggested by the stable blood levels of glucose and lactate.

The stably elevated blood level of lactate did not result in depression of the FFA blood level, suggesting unimpaired supply of FFA from extramuscular sources. Exercise at the IAT plasces a high load on aerobic metabolism without encountering progressive lactate accumulation and the associated metabolic effects.

Key words

prolonged exercise - catecholamines - insulin - growth hormone - Cortisol - substrates