Predictive validity of ventilatory and lactate thresholds for cycling time trial performance Markus Amann 1,2 , Andrew W. Subudhi 1,2 , Carl Foster 3 1 The Orthopedic Specialty Hospital, Salt Lake City, UT, USA, 2 University of Utah, Salt Lake City, UT, USA, 3 University of Wisconsin, La Crosse, WI, USA Corresponding author: Markus Amann, PhD, Room 4245, Medical Sciences Center, 1300 University Avenue, Madison, WI 53706-1532, USA. Tel: 11 608 262 9499, E-mail: amann@wisc.edu Accepted for publication 16 July 2004 Purpose: To determine which laboratory measurement best predicts 40 km cycling time-trial (TT) performance. Methods: Fifteen male cyclists performed lactate-threshold (LT), ventilatory-threshold (VT), 5 km and 40 km TT. Key variables of interest were Watts at thresholds. For VT determination we used: breakpoint of ventilatory equivalent of oxygen (VE/VO 2 ); breakpoint of ventilatory equivalent of carbon dioxide (VE/VCO 2 ); V-slope; respiratory ex- change ratio (RER) 5 1 and 0.95. For LT we used Steg- mann’s individual anaerobic threshold; the stage preceding the second 0.5 mmol L  1 increase (Baldari); 4 mmol L  1 ; 1 mmol L  1 increase in 3 min; the stage preceding the first 1 mmol L  1 increase as criterion methods (o1 mmol). Analyses also included peak power during the incremental threshold tests (MaxVT watts , MaxLT watts ) and 5 km per- formance (5K avgwatts ). Results: Regression analyses be- tween VT variables and 40K avgwatts were significant for V-slope (r 2 5 0.63), VE/VO 2 (r 2 5 0.64), RER 0.95 (r 2 5 0.53), RER 1 (r 2 5 0.57), and MaxVT watts (r 2 5 0.65). Regressions between LT variables and 40K avgwatts were significant for Baldari (r 2 5 0.52), 4 mmol L  1 (r 2 5 0.36), o1 mmol (r 2 5 0.35), Keul (r 2 5 0.34), and MaxLT watts (r 2 5 0.51). Regressions between 5K variables and 40K avgwatts were significant for 5K avgwatts (r 2 5 0.58). Paired t-tests between these variables and the 40K avgwatts indicated that absolute power outputs at VE/VO 2 (P 5 0.33), RER 0.95 (P 5 0.93), and 4 mmol L  1 (P 5 0.39) were not significantly different from 40K avgwatts . Conclusion: We conclude that VT-based variables are generally superior to LT variables relative to predicting 40K avgwatts , the simplest of several valid measures appears to be VE/VO 2 . Although VO 2max has traditionally been considered the ‘‘gold standard’’ for evaluation of endurance performance (Costill, 1967; Saltin & Astrand, 1967), recent evidence suggests that a performance threshold (PT) (often imprecisely referred to as ‘‘anaerobic threshold’’) provides a better index of aerobic endurance and therefore may be a better predictor for submaximal endurance performance (Davis, 1985; Londeree, 1997) than VO 2max . The term PT is adopted to replace the term ‘‘anaerobic threshold’’ in this study. The PT is commonly deter- mined using either blood lactate (lactate threshold (LT)) or ventilatory gas (ventilatory threshold (VT)) parameters. A wide variety of diagnostic strategies for each threshold have been described in the litera- ture. The assessment of the PT from ventilatory variables (Wasserman & McIlroy, 1964), lactate analyses (Keul et al., 1979), or from a combined analysis of ventilatory and lactate variables (Beaver et al., 1986) has been refined over the years. Never- theless, controversy continues to persist regarding the relationship between the LT and the VT. Some believe that there is a strong physiological linkage between VT and LT (Anderson & Rhodes, 1991; Burke et al., 1994) while others believe it is coin- cidental (Gladden et al., 1985). Regardless, numer- ous studies have suggested that identifying physiological parameters, such as LT and VT, and associated variables (Watts, HR, VO 2 , lactate) may be useful predictors of endurance exercise perfor- mance. The goal of this study was to identify which of several widely used laboratory-based tests best predicts 40 km cycling time trial (40K) performance. The novel idea was to directly compare and evaluate a variety of different PT identification methods. Methods Subjects Fifteen experienced male road cyclists (Table 1) volunteered for this investigation. Written informed consent was obtained from each participant. The protocol was approved by the institutions’ human subjects committees. Study protocol For 3 days prior to and during the study, subjects followed a high-carbohydrate diet, and small volume of low-intensity Scand J Med Sci Sports 2006: 16: 27–34 COPYRIGHT & BLACKWELL MUNKSGAARD 2004 Printed in Singapore . All rights reserved DOI: 10.1111/j.1600-0838.2004.00424.x 27