The Shackelford Protocol Elicits More Vo2max Criteria Than Modified Bruce And Balke-Ware In Cancer Survivors

INTRODUCTION: Cancer, its treatment, and side effects negatively impact cardiovascular functioning, measured by maximum volume of oxygen consumed (VO2max). A graded exercise test (GXT) is commonly used to assess VO2max, which is a key predictor of chronic disease risk, mortality, and is crucial to the development of exercise prescriptions (ExRx). Establishing true VO2max may be indicated by >85% of max heart rate (MHR), > 1.1 respiratory exchange ratio (RER), or > 8 on the modified Borg rating of perceived exertion (RPE) scale. Achieving VO2max criteria indicates a valid cardiovascular assessment, resulting in an accurate ExRx. The Shackelford Protocol (SP) is the only valid treadmill protocol for cancer survivors (CS) due to its ability to elicit VO2max criteria and obtain accurate measures of VO2max. However, the Balke-Ware (BW) and Modified Bruce (MB) protocols remain in use for VO2max testing despite these protocols lacking validation in CS. PURPOSE: To determine the effectiveness of the SP, MB, and BW protocols in eliciting VO2max criteria in CS. METHODS: Forty-five CS completed three maximal treadmill protocols using gas analysis via a metabolic cart. Testing was completed once per week for three weeks, assigning and performing the SP, BW, and SP protocols in random order. A Cochran’s Q statistical test was used to compare total max criteria obtained between protocols. Significance was set at p < 0.05. RESULTS: The frequency of achieved VO2max criteria significantly differed between the SP and BW (p = 0.002) and the SP and MB protocols (p = 0.03). No significant differences occurred between the BW and MB (p = 0.302) in achieved VO2max criteria. VO2max criteria was met 90%, 82%, and 76% in the SP, MB, and BW, respectively. CONCLUSION: Cancer toxicities create physiological detriments that decrease VO2max values, leading to inaccurate ExRx’s. The SP allows CS to elicit maximal criteria during VO2max tests more often than other commonly used protocols. The BW’s constant moderate speed and the MB protocol’s incline may generate more musculoskeletal fatigue (MF), whereas the SP gradual stage changes allow CS to reach more VO2max criteria prior to the onset of MF. The SP remains the superior protocol for CS as it accounts for the physiological detriments of cancer treatment.