Hofmann, P., Pokan, R., Von Duvillard, S. P., Seibert, F. J., Zwiker, R., & Schmid, P. (1997). Heart rate performance curve during incremental cycle ergometer exercise in healthy young male subjects. Medicine and Science in Sports and Exercise, 29, 762-768.

In 1992 Conconi et al. presented an indirect and noninvasive method for determining anaerobic threshold using an incremental field test for runners. This method is dependent on the occurrence of a deflection of the heart rate performance curve. This study evaluated the degree and direction of the deflection of the heart rate performance curve and the relationship of the heart rate threshold to the lactate turn point in a group of 227 healthy young males.

Ss were divided into three groups by means of second degree polynomial fitting. No significant differences between the groups were found in the anthropometric data, power output, blood lactate concentration at both the first and second lactate turn points, and at maximum performance. Using the method of Conconi et al., 85.9% (GI) of Ss showed a "regular" deflection, 6.2% (GII) showed no deflection at all, and 7.9% (GIII) showed an inverted deflection of the heart rate performance curve. A heart rate threshold could be obtained in both GI and GIII, and power output at heart rate threshold was not significantly different in comparison to that at the lactate turnpoint. The heart rates at heart rate threshold and the lactate turn point were significantly lower in GIII compared with GI. No heart rate threshold could be assessed in GII.

The phenomenon of heart rate break point may be an attractive concept for training regulation, but its application is limited because a heart rate deflection cannot be found in a substantial number of young Ss.

It is possible this phenomenon is an artifact of the Conconi et al. procedure since protocols for determining lactate, ventilatory, and heart rate thresholds determine the values obtained which are usually different between each method.

Implication. When assessing lactate or heart rate thresholds, approximately 15% of Ss will not demonstrate the phenomena being sought. A significant proportion will demonstrate the reverse of what is normally expected.

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