It is generally accepted that (1) cancer survivors are deconditioned regardless of where they are on the cancer continuum, (2) their deconditioned status can compromise their treatment and add to their posttreatment symptom burden, and (3) participation in an exercise training program can ameliorate their conditioning status, thus improving their psychological and physiological status and reducing their symptom burden.1 As such, exercise training has become an important therapeutic intervention in oncology rehabilitation.
Successful exercise training programs for anyone, including cancer survivors, must be of sufficient physiological stress to bring about adaptive and beneficial changes. The FITT (Frequency, Intensity, Time, Type) model, developed by the American College of Sports Medicine and widely used clinically, provides a framework that assists in developing exercise prescriptions that are both safe and efficacious.2 Such prescriptions, or treatment plans, typically modulate exercise intensity and duration in a very ordered, stepwise fashion to sufficiently stress an individual so as to ensure that adaptive changes occur.2 Recently, Sasso et al3 argued that the application of the FITT model creates generic and homogeneous exercise prescriptions that result in a “linear” approach to exercise training that “may be masking the full therapeutic potential of exercise treatment in the oncology setting.” These authors argue that greater adherence to the fundamental tenets of training will allow for a greater degree of “personalized” exercise prescriptions. For example, these authors point out that an individual's maximum heart rate can vary by 10 to 12 beats per minute from estimated maximum heart rates, leading to their suggestion that maximum heart should be determined empirically from exercise testing and not estimated from available prediction equations. Furthermore, these authors point out that using a traditional target heart rate range may not be sufficiently challenging to stress all components of the of the complex, multisystem response to the demands of exercise.3 Space limitations do not allow for a more complete review of this publication, but I thought that I would write briefly about some alternative approaches to developing exercise prescriptions for cancer survivors that have recently emerged and can generate personalized prescriptions.
HIGH-INTENSITY INTERVAL TRAINING
High-intensity interval training (HIIT) involves short, repeated bursts of very high-intensity exercises (aerobic and resistance types of exercise) separated by short, low-intensity activity (active recovery) that allows for partial recovery. The time of exercise relative to that of active recovery can be varied, and the number of such cycles per exercise session can also be varied. Because of the high-intensity component of the program, the total duration of individual exercise sessions is relatively short (15-25 minutes) and herein lies a significant part of the appeal of HIIT. Available evidence suggests that HIIT protocols are more effective than usual care in improving cardiorespiratory fitness in patients with lung, colorectal, and breast cancer after completion of treatment as well as in individuals with other chronic diseases.4,5 Peak exercise intensities in HIIT protocols can be as high as 95% of
O2peak, with recovery intensities generally being 50% to 60% of
O2peak or heart rate reserve. The argument is that this approach ensures the respiratory, cardiac, and muscular systems are sufficiently stressed to bring about adaptive responses.4,5 Equally interesting, but not noted, is the fact that high-intensity exercise ensures the recruitment of fast twitch skeletal muscle fibers, which are, in contrast to slow muscle fibers, preferentially preserved with aging and cancer.6 Such a recruitment pattern would most improve the power, speed, and strength of participants who have participated in HIIT protocols.4,5
Periodization is a nonlinear, organized approach to exercise training (both aerobic and resistance training) that involves cycling of various components of an exercise training program (intensity, duration, mode) across a specific period of time. The treatment plan calls for systematically alternating high loads of training with low loads of training in an effort to maximally improve muscular and aerobic fitness without compromising recovery. These oscillations occur across weeks and months rather than within single exercise sessions. Athletes frequently “periodize” their training regimens across a season to optimize their performance across their competition schedule. High-intensity activities, low-intensity activities, and periods of recovery are all incorporated into the training program in an effort to provide training variability and prevent overtraining and staleness.7,8 Varying exercise intensity across a training program helps ensure that all the individual components of the multisystem response to exercise are adequately challenged, particularly those that may be most compromised. Strohacker et al8 reported in a systematic review that periodization appears to be a feasible means for prescribing exercise for inactive people. Similar data are not currently available for cancer survivors; however, Fairman et al9 provide a solid theoretical foundation for using periodization and fundamental tenets of exercise prescription in treating cancer survivors across the entire cancer continuum. One could easily imagine a periodization program calling for low-intensity exercises pursued during active treatment, followed by a slow but progressive increase in the FITT components as the individual recovers from chemotherapy, achieving maximum exercise volume shortly before undergoing the next cycle of chemotherapy. The reverse of this periodization might be used with patients receiving radiation therapy; higher-intensity exercises as the radiation protocol begins, with intensities diminishing toward the middle of the protocol, a time when fatigue is typically at its worst. As rehabilitation professionals we may not be familiar with the mechanics of periodization programs, thus co-treating with an exercise physiologist might optimize the use and utility of this intervention in cancer survivors.
ADVERSE EFFECTS AND COMORBIDITIES
Another method for individualizing an exercise program and one that many rehabilitation staff members may already be employing, knowingly or unknowingly, involves writing an exercise prescription in the context of comorbidities and/or treatment adverse effects present in the survivor. Modifications and tailoring of the prescription may be driven by when in the continuum an exercise program is initiated, how severe the adverse effects are when initiated, and the level of adherence/compliance expected.
Van der Leeden et al10 provide a framework supporting clinical decisions for tailoring exercise interventions for these survivors predicated in the presence of adverse effects and comorbidities. Specifically, these authors used a 4-step i3-S search strategy to first identify common comorbidities associated with a particular cancer diagnosis and then identified contraindications and restrictions for the therapeutic use of exercise in the context of the diagnosis and comorbidities. The final step involved synthesizing this information into a framework to guide treatment planning and clinical decisions. The example presented in this article identified (1) symptoms often found in patients with breast cancer and undergoing chemotherapy, that is, myelosuppression, peripheral neuropathy, and fatigue; and (2) the potential effect of these symptoms on exercise performance and tolerance. Finally, these authors offered actions and/or strategies that may be used to guide clinical decision-making regarding the creation of a safe and efficacious exercise prescription in the context of these factors. For example, the presence of anemia in a breast cancer survivor suggests reducing exercise intensity based on patient symptoms ie, dyspnea, and fatigue at low levels of exertional to effort relative to the program for a breast cancer survivor who is not anemic. It is worth noting that exercise guidelines are available to guide decision making for several chronic conditions often associated with a cancer diagnosis including aging, diabetes, arthritis, and osteoporosis. I can easily imagine carrying out performance improvement projects that focus on the first 3 individual steps, all evidence-based. Once this work is completed, the results are integrated into a framework as described by van der Leeden et al.10 Creation of this framework could function as institutional or departmental evidence-based clinical practice guidelines.
TEMPLATE FOR INTERVENTION DESCRIPTION AND REPLICATION GUIDELINES
Personalizing an exercise prescription may be as straightforward as knowing how others have developed and implemented an exercise program. While such information helps avoid pitfalls and “reinventing the wheel,” Campbell et al 11 and others have noted that the reporting of even the basic constructs of the FITT model in research studies is limited at best and poor at worst. These authors found that no reviewed studies reported all FITT components of the exercise program, leading to the conclusion that this inadequate reporting of exercise interventions limits the reproducibility and/or replicability of the intervention. In other words, descriptions of exercise-based interventions are too inadequate to allow a reader to transfer the intervention to a clinical setting.
This underreporting of essential intervention details is not unique to exercise studies and has led Hoffmann et al 12 to suggest a 12-item checklist to assist authors, editors, and reviewers in assessing the completeness of an intervention description with an eye to improving replicability of an intervention, the Template for Intervention Description and Replication or TIDieR. This checklist goes beyond simply looking at how much and what kind of exercise was used (constructs of the FITT model). This checklist asks the user the why, what, how, where, when, and who provided the intervention. Relevant to the central theme of this article, this checklist calls for a description of how, why, and when an intervention such as exercise training was modified over the course of the intervention. To be sure, using this check list represents another hurdle to reporting exercise-based interventional protocols but improved reporting is essential for allowing the replication of an exercise prescription whether that prescription is used in a clinical study or simply used clinically.
Exercise is increasingly viewed as an important therapeutic intervention across the entire cancer continuum, and, as with other interventions, the call for individualizing those interventions continues to increase in volume. Current exercise guidelines rely on linear or very regimented models of exercise prescription and do not offer a great deal of guidance in individualizing exercise prescriptions in treatment planning. This failure may well limit the potential effectiveness of this intervention. In this article, my penultimate column as President of the Academy, I have presented some ideas to help guide the clinician in treatment planning beyond the basic interventional strategies suggested by the FITT model. Personalizing the exercise prescription may allow patients to derive even greater than anticipated benefit from their participation in an exercise program.
Changing gears, I would like to extend my heartiest congratulations to those who have earned the recognition as a Board Certified Clinical Specialist in Oncologic Physical Therapist. You are the future of oncology rehabilitation and are poised to take leadership roles in advancing the care of our patients. I would also like to extend my deepest appreciation for those who served as item writers and case report reviewers. It indeed took a village to generate our first class of specialists (this phrase has a nice ring to it!!). Thanks to all involved directly and indirectly in the Herculean effort that was required to move us to where we are today.
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2. American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription. 10th ed. Philadelphia, PA: Wolters Kluwer; 2017.
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12. Hoffmann TC, Glasziou PP, Boutron I, et al Better reporting of interventions: Template for Intervention Description and Replication (TIDieR) checklist and guide. BMJ. 2014;348:g1687. doi:10.1136/bmj.g1687.