THE RELATIONSHIP BETWEEN HEART RATE DEFLECTION POINT AND THE VENTILATORY ANAEROBIC THRESHOLD IN BASKETBALL PLAYERS

Jurica Šango1, Davor Šentija1, Vlatko Vučetić1

Faculty of Kinesiology, Zagreb, Croatia

ABSTRACT

The purpose of this study is to examine the relationship between the heart rate deflection point (HRDP) and the ventilatory anaerobic threshold (AT) and to determine whether changes in heart rate to workload linearity can be used to accurately estimate AT in elite basketball players. Forty-three professional male basketball players performed a graded maximal exercise test on a motor-driven treadmill. The anaerobic threshold was assessed by a nonlinear increase in carbon dioxide output to oxygen consumption ratio (V-slope method). The HRDP was determined using the method of deflection of linearity by visual inspection There was no statistically significant difference between the. the running speed (RS) at the AT (12.9±1.0km*h-1) and HRDP (13.0±1.2km*h-1) (p>.05). However, a small but significant difference between the heart rate (HR) at the AT (163.3±7.8 b*min-1) and HRDP (166.3±8.6 b*min-1) was found (p<0.05). We can conclude that the intensity at the HRDP is a potential tool for non-invasive detection of the intensity at the AT based on HR response during graded exercise in professional basketball players.

Key words: Anaerobic threshold, heart rate deflection point, basketball

INTRODUCTION

Several methods have been applied for detecting anaerobic threshold, based on blood lactate concentration as well as respiratory gas exchange parameters. The AT has been shown to be highly correlated to performance in aerobic events and is valuable in determination of optimal training loads and fitness level in competitive athletes. Laboratory assessement of the AT by lactate or gas exchange measurement represents an accurate but expensive procedure, and is thus out of reach for many athletes and sport coaches. Therefore, there is a need in sports diagnostics for simple and unexpensive, but nevertheless valid and accurate tests to assess the AT. During progressive incremental exercise a deflection point from the linear heart rate-work relationship is evidenced (Brooke and Hamley, 1972; Conconi et al., 1982). The relationship between HRDP and AT is the subject of research in the last 2 decades with contradictory results ( Bodner and Rhodes, 2000.). Conconi et al. (1982.) first suggested the use of a simple field test for determination of the HRDP as a valid measure of AT in runners.

The purpose of this study is to determine the relationship between the HRDP and the ventilatory anaerobic threshold in athletes with specific morphological characteristics, such as basketball players.

METHODS

Fourty two male elite basketball players (22.7±4.7 yrs of age, 197.3±8.0 cm height, 95.7±9.8 kg weight) participated in this study. All subjects are members of professional basketball teams or their national teams.

The subjects performed an incremental maximal exercise test with one minute stages on a motor-driven trademill (Run race, Technogym, Italy), with 1.5% inclination. A „breath-by-breath“ gas analisys system (Quark b2,Cosmed, Italy) was used for respiratory gas exchange recording. Heart rate was monitored using a Polar Vantage NV (Polar ElectroOi, Finland) heart rate monitor. HR, metabolic gas and ventilatory parameters were averaged for every thirty seconds. The maximal exercise test was terminated at volitional fatigue of the subject.

The anaerobic threshold was estimated by the V-slope method,using a second disproportionate increase of the volume of carbon dioxide expired in relation to the volume of oxygen consumption (respiratory compensation point). Heart rate and running speed at AT were determined by interpolation. Using the same test data, the heart rate vs. time was plotted and evaluated by visual inspection for detecting the HR breakpoint. The subjects whose HRDP could not be indentified, were excluded from further analysis.

The paired t-test for dependent samples was used to evaluate the statistical significance of differences between the ventilatory AT and the HRDP method. The significance level was set at p < 0.05.

RESULTS AND DISCUSSION

The results of the study are presented in Table 1. The HRDP could not be identified in 5 (11.9%) subjects, and their results were not included in the analysis. All other subjects demonstrated a downward-like HRDP. Similar percentages in the ocurrance of the HRDP (80-90%) were also reported in other studies.

Table 1. Speed of running and heart rate at the AT and HRDP

AT /

HRDP

/

P

HR (bpm) / 163.3±7.8 / 166.4±8.6 / 0.02
V (km/h) / 12.9±1.0 / 13.0±1.2 / 0.71

Legend: see text

The mean running speed (V) at HRDP and AT are almost identical (t=-0.36, p=0.71). This finding is consistent with the work of several authors (Zacharogiannis et al., 1993; Bunc et al., 1995), which confirms the validity of workload at HRDP as a measure of intensity at the anaerobic threshold. However, the mean difference in heart rate between HRDP and AT (3.0 b*min-1) although very small, is statistically significant (t=2.39, p<0.02). The explanation for this is not clear. Conconi and co-workers (1996) showed that heart rate adapts to each new work rate within 30 seconds; we can speculate that the adaptation of heart rate to each new work rate is slower than for the gas exchange parameters.

In conclusion, our data suggest that the intensity at the HRDP coincides with the intensity at the ventilatory anaerobic threshold during graded exercise in professional basketball players and in most cases can be used for the detection of the anaerobic threshold. More caution is necessary when using the heart rate at the deflection point as a measure of AT intensity, as it slightly, but significantly overestimates the heart rate at the AT. The simplicity and low-cost favors the use of noninvasive methods such as the HRDP method in diagnostics of sports performance, especially where the laboratory equipement for AT determination (lactate and gas analysers) is not available.

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