The aim of the present study was to investigate the accuracy of the maximal constant heart rate method for predicting anaerobic threshold (AnT) in running. This method only requires a common heart rate (HR) monitor and is based on the identification of the maximal constant HR maintainable for 30 min (HRMC). HRMC, 4-mmol threshold, and maximal lactate steady state (MLSS) were determined in 31 probands. 17 probands underwent an additional MLSS retest within 2 weeks. The correlation between HR at MLSS and at MLSS retest was very close (r = 0.807; SEE = 5.25 beats x min(-1); p < 0.001). So were the correlations between HR at 4-mmol threshold and MLSS (r = 0.844; SEE = 6.43 beats x min(-1); p < 0.001) and between HRMC and HR at MLSS (r = 0.820; SEE = 6.73 beats x min(-1); p < 0.001). Mean velocities at maximum constant HR trials and MLSS (r = 0.895; SEE = 0.185 m x s(-1); p < 0.001) as well as 4-mmol threshold and MLSS (r = 0.899; SEE = 0.186 m x s(-1); p < 0.001) were highly correlated. In conclusion, data presented in this study confirm that the determination of HRMC is a manageable method giving a highly accurate estimation of both HR and velocity at MLSS in running.
These results show that the ATS standard protocol, using a heart rate formula for assessing the exercise intensity, is not sufficient to cause predominantly anaerobic lactate metabolism and hence exercise-induced hyperventilation. Therefore, a potential bronchial obstruction could not be induced in 56% of the subjects. For a sensitive study design, exercise intensities demanding anaerobic lactate metabolism should always be ensured. A more precise protocol is required.
Introduction
Prolonged time trials proved capable of precisely estimating anaerobic threshold. However, time trial studies in recreational cyclists are missing. The aim of the present study was to evaluate accuracy and viability of constant power threshold, which is the highest power output constantly maintainable over time, for estimating maximal lactate steady state in recreational athletes.
Methods
A total of 25 recreational athletes participated in the study of whom 22 (11 female, 11 male) conducted all constant load time trials required for determining constant power threshold 30 min and 45 min, which is the highest power output constantly maintainable over 30 min and 45 min, respectively. Maximal lactate steady state was assessed subsequently from blood samples taken every 5 min during the time trials.
Results
Constant power threshold over 45 min (175.5 ± 49.6 W) almost matched power output at maximal lactate steady state (176.4 ± 50.5 W), whereas constant power threshold over 30 min (181.4 ± 51.4 W) was marginally higher (P = 0.007, d = 0.74). Interrelations between maximal lactate steady state and constant power threshold 30 min and constant power threshold 45 min were very close (R2 = 0.99, SEE = 8.9 W, Percentage SEE (%SEE) = 5.1%, P < 0.001 and R2 = 0.99, SEE = 10.0 W, %SEE = 5.7%, P < 0.001, respectively).
Conclusions
Determination of constant power threshold is a straining but viable and precise alternative for recreational cyclists to estimate power output at maximal lactate steady state and thus maximal sustainable oxidative metabolic rate.
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