• The validity of predicting O2max from perceptually regulated treadmill exercise

      Morris, Mike; Hayton, John (University of Chester, 2008-06)
      Objective: The purpose of this study was to assess the validity of predicting O2max from sub-maximal O2 values elicited during perceptually-regulated treadmill exercise tests. Methods: Eleven males and seven females with a mean age of 21.7 (±2.8) years completed three identical sub-maximal, perceptually-guided graded exercise tests (PGXTs) on a motorised treadmill and a final maximal graded exercise test (GXT) to establish O2max. Participants performed testing over a ten day period, allowing for two days rest between tests. When performing the PGXTs participants were required to produce intensities corresponding to levels 9, 11, 13 and 15 on Borg’s 6-20 ratings of perceived exertion (RPE) scale, in that order. Each RPE production level was performed for three minutes, measurements of O2 and heart rate were measured continuously and recorded in the final 30 seconds of each level. The Bruce protocol was selected for the maximal GXT ( O2maxGXT). Individual linear regression relationships between RPE and O2 for the RPE ranges of 9-15, 9-13 and 9-11 were extrapolated to both RPE19 and RPE20. Results: For the RPE range 9-15 prediction accuracy improved with practice across consecutive trials reporting 50.0±10.1, 49.1±8.1, and 47.3±6.9 ml•kg-1•min-1 for trials 1, 2 and 3 respectively, as the actual mean O2max reported was 48.0±6.2. The third and final trial produced the best LoA between predicted and actual O2max of -0.6±7.1 ml•kg-1•min-1, therefore achieving a worst case scenario range of 6.5 ml•kg-1•min-1 below the criterion O2max score and 7.7 ml•kg-1•min-1 above. Consistency soundly improved between trials reporting LoA of 0.90±12.3 between trial 1 and 2, and 1.72±8.50 between 2 and 3. However, the RPE ranges 9-11 and 9-13 decreased in accuracy and consistency from consecutive trials and thus reported considerably less favourable LoA analyses. The closest predictions to actual O2max when using the 9-13 and 9-11 range were generated from the first trial, providing poor worst case scenario ranges of 18.6 – 18.9 ml•kg-1•min-1 and 16.9 – 32.2 ml•kg-1•min-1, respectively. Conclusions: The data suggest that a sub-maximal, perceptually-guided, graded treadmill exercise protocol can provide acceptable estimates of O2max when employing a perceptual range including at least a high order RPE of 15. Estimates are further improved with practice in young, healthy individuals. The poor predictive performance when using the RPE ranges 9-11 and 9-13 were attributed to less apparent sensations of exertion.