A framework for prescription in exercise-oncology research

Abstract

The field of exercise-oncology has increased dramatically over the past two decades, with close to 100 published studies investigating the efficacy of structured exercise training interventions in patients with cancer. Of interest, despite considerable differences in study population and primary study end point, the vast majority of studies have tested the efficacy of an exercise prescription that adhered to traditional guidelines consisting of either supervised or home-based endurance (aerobic) training or endurance training combined with resistance training, prescribed at a moderate intensity (50-75% of a predetermined physiological parameter, typically age-predicted heart rate maximum or reserve), for two to three sessions per week, for 10 to 60 min per exercise session, for 12 to 15 weeks. The use of generic exercise prescriptions may, however, be masking the full therapeutic potential of exercise treatment in the oncology setting. Against this background, this opinion paper provides an overview of the fundamental tenets of human exercise physiology known as the principles of training, with specific application of these principles in the design and conduct of clinical trials in exercise-oncology research. We contend that the application of these guidelines will ensure continued progress in the field while optimizing the safety and efficacy of exercise treatment following a cancer diagnosis.

© 2015 The Authors. Journal of Cachexia, Sarcopenia and Muscle published by John Wiley & Sons Ltd on behalf of the Society of Sarcopenia, Cachexia and Wasting Disorders.

Figures

Figure 1

The principles of training.

Figure 2

Oxygen consumption and ventilatory responses to incremental treadmill exercise in a 65 year-old woman with early-stage breast cancer. (A) Increasing workloads during the cardiopulmonary exercise test causes linear increases in oxygen consumption (VO2 in mL/kg/min) to the point of volitional fatigue at a VO2peak of 18.9 mL/kg/min. (B) A graphical representation of alveolar ventilation (VE in L/min) demonstrate two exponential ‘breakpoints’ in ventilation corresponding to Ventilatory Threshold 1 (VT1) and Ventilatory Threshold 2 (VT2). These thresholds demarcate the transition of low, medium, and high exercise intensity, and correspond to specific parameters that may be used for identification of relative intensity for exercise prescription and monitoring. These intensities and the corresponding ranges of physiological identification thereof (heart rate, blood pressure, and rating (Rtg) of perceived exertion on a 6–20 scale) provide an appropriate tool for indirect assessment of training stress and intensity.

Figure 3

Comparison of linear and nonlinear exercise prescriptions. Each bar represents a training session at prescribed workloads based on the absolute or relative intensity. (A) The conventional (linear) approach utilizes standard intensity, frequency, and duration parameters after an initial lead in period, with static increases in session duration (i.e. 20 to 45 min). (B) The alternative non-linear approach considers the principles of exercise training in order to optimize the adaptations to the exercise stimulus. Sessions are tailored to an individual's relative intensity, based on cardiopulmonary exercise testing or exercise tolerance testing, and specified to address a particular endpoint. Sessions and weeks progress over the course of the prescription and vary between low intensity (e.g. 55% VO2peak; white bars) and moderate (e.g. 75%; grey bars) and high intensity (e.g. 100% VO2peak; black bars) training in order to target various physiological systems involved in the cardiopulmonary response to exercise. Session intensity is inversely related to session duration, that is, sessions involving high relative intensity workloads are conducted in shorter bouts through short duration training sessions and are less frequent to ensure recovery between sessions. VO2peak, peak rate of oxygen consumption.