Med Sci Sports Exerc. 2018 Sep 19
To assess the quality of the relationship between VO2peak estimated from patient outcomes on the 6-minute walk test (6-MWT) and the VO2peak calculated from patient outcomes on the University of Northern Colorado Cancer Rehabilitation Institute (UNCCRI) treadmill protocol.
Cancer survivors (N = 187) completed the UNCCRI treadmill protocol and a 6MWT one week apart in randomized order to obtain VO2peak. Values from the UNCCRI treadmill protocol were compared against four common 6MWT VO2peak prediction equations.
All four 6MWT prediction equations significantly (p < 0.001) underestimated VO2peak with predicted values ranging from 8.0 ± 4.1 to 18.6 ± 3.1 mL/kg/min, while the UNCCRI treadmill protocol yielded a significantly higher value of 23.9 ± 7.6 mL/kg/min. A positive strong correlation occurred between estimated VO2peak derived from the UNCCRI treadmill protocol and only one of the VO2peak values derived from the 6MWT prediction equations (r = 0.81), and all four equations consistently underpredicted VO2peak.
These findings suggest that the 6MWT is not a valid test for predicting VO2peak in the cancer population due to its consistent underestimation of VO2peak regardless of the prediction equation. Obtaining an accurate and valid VO2peak value is necessary in order to correctly prescribe an individualized exercise rehabilitation regimen for cancer survivors. It is recommended that clinicians avoid the 6MWT and instead implement treadmill testing to volitional fatigue to quantify VO2peak in cancer survivors.