Abstract
Introduction
Blood lactate concentration (BLC) is a generally accepted measure of exercise intensity (Beneke et al. 2001). The purpose of this study was to investigate two models describing the relationship between BLC and power, and BLC and relative exercise intensity in incremental load cycling. Previously, a mono-exponential equation with two parameters (2-PM) BLC = ae(power bx), where x can be either power output or intensity (Pansold and Zinner 1994) had been used. In the latter model the parameter “a” does not only affect the increase of the BLC with time, but is also strongly affected by resting lactate. Therefore, we tested the hypothesis that a three-parameter model (3-PM) BLC = ae(power bx) + c gives a better description of the BLC response to incremental load exercise.
Methods
Fifteen healthy male subjects (age: 22.9 ± 3.2 yrs, height: 180.8 ± 8.5 cm, body mass: 74.7 ± 14.6 kg) completed an incremental cycling test to exhaustion at pedal rate of 50 revolutions per minute. The power output was initiated at 1
W kg-1 body mass and increased by 0.5 W kg-1 body mass. Capillary blood samples were drawn from the hyperaemic earlobe at rest and at the end of every two-minute stage. The relative intensity was calculated as percentage of peak
power. The BLC response to incremental exercise was approximated for each test separately using non-linear regression procedures based on the 2- and the 3-parameter model, respectively. The goodness of the two approximations of both models was compared based on coefficients of determination and further residual analyses including distribution and auto-correlation. For all statistics the level of significance was set at p < 0.05.
Results
Based on power output both the 2- and the 3-parameter model revealed high and similar coefficients of determination (R²: 0.95 ± 0.05 vs. 0.95 ± 0.04, p > 0.05). However both models provided skewed and auto-correlated residuals (Durbin-Watson coefficient: 1.37 ± 0.67 vs. 1.45 ± 0.63, p > 0.05). Based on intensity the explanation of the variance was higher (p < 0.05) using the 3-PM (R² = 0.99 ± 0.01) than the 2-PM (R² = 0.97 ± 0.02). Furthermore this finding was combined with almost normal distributed residuals without relevant auto-correlation in the 3-PM but not in the 2-PM (Durbin-Watson coefficient: 2.3 ± 0.18 vs. 1.16 ± 0.33, p < 0.05).
Conclusion
The present results indicate that mono-exponential models have limitations in the description of the interrelationship between BLC and power output. However, the tested 3-parameter model seems to be a feasible tool for the approximation of BLC intensity curves.
References
Beneke R, Leithauser RM, Hutler M (2001) Br J Sports Med;35(3):192-6
Pansold and Zinner (1994) In Clasing D, Weicker H, Böning D (Eds) Stellenwert der Laktatbestimmung in der Leistungsdiagnostik, Fischer, ISBN 3-437-11444-1
Blood lactate concentration (BLC) is a generally accepted measure of exercise intensity (Beneke et al. 2001). The purpose of this study was to investigate two models describing the relationship between BLC and power, and BLC and relative exercise intensity in incremental load cycling. Previously, a mono-exponential equation with two parameters (2-PM) BLC = ae(power bx), where x can be either power output or intensity (Pansold and Zinner 1994) had been used. In the latter model the parameter “a” does not only affect the increase of the BLC with time, but is also strongly affected by resting lactate. Therefore, we tested the hypothesis that a three-parameter model (3-PM) BLC = ae(power bx) + c gives a better description of the BLC response to incremental load exercise.
Methods
Fifteen healthy male subjects (age: 22.9 ± 3.2 yrs, height: 180.8 ± 8.5 cm, body mass: 74.7 ± 14.6 kg) completed an incremental cycling test to exhaustion at pedal rate of 50 revolutions per minute. The power output was initiated at 1
W kg-1 body mass and increased by 0.5 W kg-1 body mass. Capillary blood samples were drawn from the hyperaemic earlobe at rest and at the end of every two-minute stage. The relative intensity was calculated as percentage of peak
power. The BLC response to incremental exercise was approximated for each test separately using non-linear regression procedures based on the 2- and the 3-parameter model, respectively. The goodness of the two approximations of both models was compared based on coefficients of determination and further residual analyses including distribution and auto-correlation. For all statistics the level of significance was set at p < 0.05.
Results
Based on power output both the 2- and the 3-parameter model revealed high and similar coefficients of determination (R²: 0.95 ± 0.05 vs. 0.95 ± 0.04, p > 0.05). However both models provided skewed and auto-correlated residuals (Durbin-Watson coefficient: 1.37 ± 0.67 vs. 1.45 ± 0.63, p > 0.05). Based on intensity the explanation of the variance was higher (p < 0.05) using the 3-PM (R² = 0.99 ± 0.01) than the 2-PM (R² = 0.97 ± 0.02). Furthermore this finding was combined with almost normal distributed residuals without relevant auto-correlation in the 3-PM but not in the 2-PM (Durbin-Watson coefficient: 2.3 ± 0.18 vs. 1.16 ± 0.33, p < 0.05).
Conclusion
The present results indicate that mono-exponential models have limitations in the description of the interrelationship between BLC and power output. However, the tested 3-parameter model seems to be a feasible tool for the approximation of BLC intensity curves.
References
Beneke R, Leithauser RM, Hutler M (2001) Br J Sports Med;35(3):192-6
Pansold and Zinner (1994) In Clasing D, Weicker H, Böning D (Eds) Stellenwert der Laktatbestimmung in der Leistungsdiagnostik, Fischer, ISBN 3-437-11444-1
| Original language | English |
|---|---|
| Pages | 232 |
| Number of pages | 1 |
| Publication status | Published - Jul 2005 |
| Event | 10th Annual Congress of the European College of Sport Science (ECSS), 13-16th July, 2005, Belgrade, Serbia & Montenegro. - Belgrade, Belgrade, Serbia Duration: 13 Jul 2005 → 16 Jul 2005 |
Conference
| Conference | 10th Annual Congress of the European College of Sport Science (ECSS), 13-16th July, 2005, Belgrade, Serbia & Montenegro. |
|---|---|
| Country/Territory | Serbia |
| City | Belgrade |
| Period | 13/07/05 → 16/07/05 |