THE MODIFIED Dmax METHOD IS RELIABLE TO PREDICT THE SECOND VENTILATORY THRESHOLD IN ELITE CROSS-COUNTRY SKIERS

Fabre, N, Balestreri, F, Pellegrini, B, and Schena, F. The modified Dmax method is reliable to predict the second ventilatory threshold in elite cross-country skiers. J StrengthCond Res 24(6): 15461552, 2010-This study was designed to evaluate, in elite cross-country skiers, the capacity of the D-MAX lactate threshold method and its modified version (D-MAX MOD) to accurately predict the second ventilatory threshold (VT2). Twenty-three elite cross-country skiers carried out an incremental roller-ski test on a motorized treadmill. Ventilation, heart rate (HR), and gas exchanges were continuously recorded during the test. Blood was sampled at the end of each 3-minute work stage for lactate concentration measurements. The VT2 was individually determined by visual analysis. The D-MAX, D-MAX MOD points also with the 4 mmol.L-1 fixed lactate concentration value (4 mM) were determined by a computerized program. Paired t tests showed nonsignificant differences between HR at VT2 and HR at D-MAX MOD, between HR at VT2 and HR at 4 mM, and between HR at D-MAX MOD and HR at 4 mM. HR at D-MAX was significantly lower than HR at VT2, D-MAX MOD, and at 4 mM(p < 0.001). HR at VT2 was strongly correlated with HR at 4 mM (r = 0.93, p < 0.001), HR at D-MAX (r = 0.97, p < 0.001) and especially with HR at D-MAX MOD (r = 0.99, p < 0.001). Bland-Altman plots showed that HR at D-MAX underestimated HR at VT2 and permitted to observe that the D-MAX method and particularly the D-MAX MOD method had smaller limits of agreement as compared with the 4 mM method. Our results showed that the D-MAX MOD lactate threshold measurement is extremely accurate to predict VT2 in elite cross-country skiers.