A Semi-tethered Incremental Protocol Is A Valid Method Of Measuring VO2max In Trained Swimmers

Swimming VO2max tests have typically been limited to discontinuous protocols that employed backwards extrapolation to estimate O2max. This has resulted in reporting VO2peak and not VO2max, the latter of which requires validation of a VO2-work rate plateau. We previously used a continuous semi-tethered swimming incremental protocol that enabled the measurement of VO2 every minute, but we were unable to detect a VO2-work rate plateau. Moreover, these tests often resulted in values lower than would be expected of well-trained athletes, begging the question of the validity of their results. PURPOSE: Test the hypothesis that VO2 measured upon exhaustion during a continuous semi-tethered swimming incremental protocol will not be a valid measure of VO2max. METHODS: Sixteen trained swimmers (6 women) completed a semi-tethered incremental swimming test and verification protocol. Participants were tethered to a pulley system while swimming in a flume at a constant speed. The resistance on the pulley was increased every minute until achieving volitional exhaustion. Participants then rested for five minutes before performing a supramaximal bout in which the resistance was increased ~10% from their final workload. Heart rate and breath-by-breath metabolic data (indirect calorimetry) were collected continually. VO2 data were filtered post hoc using a rolling time average. Paired t-tests were used to compare outcomes at the end of the incremental and verification trials. Least squares regression was used to determine if VO2 had a plateau between the final incremental stage and the verification trial (i.e., mean diff <50%). Data are presented as mean ± SD. RESULTS: VO2 (inc: 50.7 ± 7.8 mL/kg/min, ver: 51.3 ± 7.4 mL/kg/min; p = 0.18) and heart rate (inc: 178 ± 7 bpm (90 ± 4% HRmax), ver: 178 ± 6 bpm (90 ± 3% HRmax); p = 0.46, n = 12) did not differ between the incremental and verification trials. RER differed between trials (inc: 0.97 ± 0.08, ver: 0.86 ± 0.11; p < 0.01). No verification trials resulted in >50% difference of the predicted slope (mean diff: 10 ± 21%) indicating a VO2-work rate plateau. CONCLUSION: A semi-tethered swimming incremental test provides a valid measure of VO2max when measured breath-by-breath. Moreover, standard secondary criteria may not be an accurate means to determine the validity of a swimming VO2max test. World Aquatics