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The Conconi test is not valid for estimation of the lactate turnpoint in runners
ANDREW M. JONES and JONATHAN H. DOUST
Human Performance Laboratory, Chelsea School Research Centre, University of Brighton, Eastbourne BN20 7SP, UK
Accepted 16 October 1996
Conconi et al. (1982) reported that an observed deviation from linearity in the heart rate-running velocity relationship determined duringa field test in runners coincided with the 'lactate threshold'. The aim of this study was to assess the validity of the original Conconi test using conventional incremental and constant-load laboratory protocols. Fourteen trained male distance runners (mean +/-s: age 22.6 +/- 3.4 years; body mass 67.6 +/- 4.8 kg; peak VO2 66.3 +/- 4.7 ml kg-1 min-1) performed a standard multi-stage test fordetermination of lactate turnpoint and a Conconi test on a motorized treadmill. A deviation from linearity in heart rate was observed in nine subjects. Significant differences were found to exist between running velocity at the lactate turnpoint (4.39 +/- 0.20 m s-1) and at deviation from linear heart rate (5.08 +/- 0.25 m s-1) (P < 0.01), and between heart rate at the lactate turnpoint (172 +/- 10beats min-1) and at deviation from linearity (186 +/- 9 beats min-1) (P < 0.01). When deviation of heart rate from linearity was evident, it occurred at a systematically higher intensity than the lactate turnpoint and at approximately 95% of maximum heart rate. These results were confirmed by the physiological responses of seven subjects, who performed two constant-velocity treadmill runs at 0.14 ms-1 below the running velocity at the lactate turnpoint and that at which the heart rate deviated from linearity. For the lactate turnpoint trial, the prescribed 30 min exercise period was completed by all runners (terminal blood lactate concentration of 2.4 +/- 0.5 mM), while the duration attained in the trial for which heart rate deviated from linearity was 15.9 +/- 6.7 min (terminal bloodlactate concentration of 8.1 +/- 1.8 mM). We concluded that the Conconi test is invalid for the non-invasive determination of the lactate turnpoint and that the deviation of heart rate from linearity represents the start of the plateau at maximal heart rate, the expression of which is dependent upon the specifics of the Conconi test protocol

Introduction
The “anaerobic threshold”, defined as theexercise VO2 above which anaerobic high-energy phosphate production supplements aerobic high-energy phosphate production (Wasserman et al., 1994), has long been recognized as an important determinant of endurance exercise performance (Davies and Thompson, 1979; Sjodin and Jacobs, 1981; Tanaka et al., 1986). The determination of the anaerobic threshold has traditionally required laboratory exerciseand blood sampling procedures for the assessment of the exercise intensity above which lactate starts to accumulate in the blood (lactate threshold), or sophisticated gas analysis apparatus if the anaerobic threshold is defined by non-inva-sirve gas exchange methods (Wasserman et al., 1973).
Conconi et al. (1982) reported the development of a non-invasive field test of the anaerobic thresholdafter hypothesizing that anaerobic energy production would “spare” aerobic demand and result in a reduced rate of increase in VO2 (and heart rate) above the anaerobic threshold. This test, which was to become known as the “Conconi test”, was simply based upon the relationship between heart rate and running velocity in runners performing an incremental exercise protocol. Conconi et al. (1982) reportedthat beyond a certain submaxim al running velocity exceeded the increase in heart rate. The Conconi group validated this point of deviation in heart rate against measurements of blood lactate obtained during an unconventional protocol in the field, and reported coincidence between running velocity at which heart rate deviated from linearity and that at the “lactate threshold” Conconi et al....
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