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The relationship of the heart rate threshold to the ventilatory threshold in trained cyclists

University of British Columbia

The purpose of this study was to assess the relationship of the heart rate threshold (HRT) to the ventilatory threshold (TVENT) in trained cyclists. Twenty-one endurance trained cyclists (mean ± SD values: age = 26.2 ± 5.6 years; weight = 76.2 ± 8.2 kg; height = 179.1 ± 6.3 cm; VO₂ max. = 67.6 ± 4.7 ml • kg • min⁻¹) volunteered to participate in this study. Each subject completed a maximal cycle ergometer test to volitional fatigue. The procedure utilized a ramped protocol on an electronically braked cycle ergometer with initial resistance set at 50 watts (W) • min⁻¹ with a 30 W • min⁻¹ increase. Ventilatory variables (VE, VO₂ , VCO₂ ) and power were measured on-line with averages reported every twenty seconds. Heart rate (HR) was measured using a portable cardio-telemetric monitor and was observer recorded every twenty seconds. TVENT was assessed using the excess CO₂ (ExCCh) elimination curve. The HRT was assessed using a mathematical model (MM) that incorporates the natural log of H R data points to produce a curvilinear fit through these points. The first order derivative of the upper portion of the logistic curve delineated the HRT. Statistical significance was set a priori at p < 0.01. Paired t-tests indicated that there were no significant differences (p > 0.01) between HR values at HRT (171.7 ± 9.6 beats • min⁻¹) and TVENT (169.8 ± 9.9 beats • min⁻¹) or VO₂ values at HRT (53.6 ± 4.2 ml • kg • min⁻¹ ') and TVENT (52.2. ± 4.8 ml • kg • min"1). However, power values at HRT (318.7 ± 30.7 W) were significantly different from those at TVENT (334.8 ± 36.7 W). Pearson product-moment zero-order correlation coefficient demonstrated significant relationships between HRT and T V E N T for the physiological variables of H R (r = 0.92, p < 0.001), VO₂ (r = 0.72, p < 0.001) and power (r = 0.77, p < 0.001). These findings indicate that H R and VO₂ at the HRT are not significantly different from those values at TVENT in trained cyclists.

Thesis/Dissertation

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2009-06-16

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http://hdl.handle.net/2429/9292

Human Kinetics

University of British Columbia

UBCV

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