Indirect estimation of VO2max in athletes by ACSM's equation: valid or not?

Aim: The purpose of this study was to assess the indirect calculation of VO(2)max using ACSM's equation for Bruce protocol in athletes of different sports and to compare with the directly measured; secondly to develop regression models predicting VO(2)max in athletes. Methods: Fifty five male athletes of national and international level (mean age 28.3 +/- 5.6 yrs) performed graded exercise test with direct measurement of VO2 through ergospirometric device. Moreover, 3 equations were used for the indirect calculation of VO(2)max: a) VO(2)max = (0.2 . Speed) + (0.9 . Speed . Grade) + 3.5 (ACSM running equation), b) regression analysis model using enter method and c) stepwise method based on the measured data of VO2. Age, BMI, speed, grade and exercise time were used as independent variables. Results: Regression analysis using enter method yielded the equation (R=.64, standard error of estimation [SEE] = 6.11): VO(2)max (ml.kg(-1).min(-1)) = 58.443 - (0.215 . age) - (0.632 . BMI) - (68.639 . grade) + (1.579 . time) while stepwise method (R = .61, SEE = 6.18) led to: VO(2)max (ml.kg(-1).min(-1)) = 33.971 - (0.291 . age) + (1.481 . time). The calculated values of VO(2)max from these regression models did not differ significantly from the measured VO(2)max (p>.05). On the contrary, VO(2)max calculated from the ACSM's running equation was significantly higher from the actually measured value by 14.6% (p <05). Conclusions: In conclusion, it seems that ACSM's equation is not capable of accurately predicting VO(2)max in athletes aged 18-37 years using Bruce protocol. Only the regression models were correlated moderately with the actually measured values of VO(2)max.