Evaluation of Valid VO_2max Criteria for Graded Exercise Testing in Cancer Survivors

Cardiovascular fitness (VO_2max) predicts all-cause mortality and is vital to assess in cancer survivors (CS) for individualized exercise prescriptions. Metabolic carts confirm VO_2max with respiratory exchange ratio (RER) ≥1.10; other VO_2max criteria include ≤10 beats/minute of maximal predicted heart rate and/or a rating of perceived exertion (RPE) of >8 on the Modified Borg Scale. Another suggested criterion is respiratory frequency (Rf) ≥ 40 breaths per minute. These criteria are assumed applicable for all populations, but due to cancer-related toxicities, frequency and validity of traditional VO_2max criteria usage in CS remains unconfirmed. The purpose was to evaluate the frequency of VO_2max criterion achievement of RER and alternate maximal criteria using HR, RPE, and Rf in CS. Forty CS performed three graded exercise tests (GXT) using gas analysis, totaling 111 GXTs. Max RER, HR, RPE, and Rf were measured. Differences in successful VO_2max criterion achievement frequency were assessed using a Cochran's Q test and Pairwise Comparison Dunn test with Bonferroni adjustment. Maximal criteria were successfully met in 84%, 79%, 92%, and 43% of trials when evaluating RER, HR, RPE, and Rf, respectively. Significant differences occurred between Rf and all other measures (p < 0.001); no significant differences occurred between RER, HR, RPE. Traditional VO_2max criteria may be feasibly obtained and used in CS; HR and RPE are valid alternatives to RER, but Rf is not. The equivalency between RER, RPE, and HR suggests metabolic carts may be unnecessary for CS during maximal testing, increasing accessibility and validity of VO_2max values.