Active Voice: Exercise is NOT a Single Medicine - Targeted Prescription Ameliorates Muscle and Bone Loss in Patients with Prostate Cancer
By Robert U. Newton, Ph.D., AEP, CSCS*D, FESSA, FNSCA
Robert Newton, Ph.D., has been a member of ACSM for 19 years. He is associate dean of medical and exercise sciences and research professor at the Exercise Medicine Research Institute, Edith Cowan University Perth, in Western Australia. His current major research directions include reducing decline in strength, body composition and functional ability in cancer patients, cancer related fatigue and the influence of exercise on tumor biology. Dr. Newton is an accredited exercise physiologist in Australia and maintains a clinical role in management of cancer patients.
This commentary presents Dr. Newton’s views on the topic of a research article which he and colleagues authored. Their research article appears in the April 2019 issue of Medicine & Science in Sports & Exercise® (MSSE).
As a profession, we must become much more sophisticated in the way we prescribe exercise for the management of various chronic diseases. While any physical activity is likely to be beneficial, patients experiencing considerable morbidity and potential mortality from chronic diseases such as cancer need, and certainly deserve, access to the optimal exercise prescription. It should be tailored to provide the greatest physical and psychological health benefits. Exercise is not a single medicine — instead it ought to be viewed as a medical intervention with a myriad of mode and dosage combinations having highly differentiated effects on the body systems.
Based on our study, as presented in the April 2019 issue of MSSE, we found very precise effects of three different targeted and periodized exercise interventions in 154 men with prostate cancer receiving androgen deprivation therapy (ADT). Our aim was to determine if specific exercise prescriptions could slow or reverse bone and muscle loss, which are highly problematic toxicities of ADT. By combining resistance and impact training, we ameliorated bone loss in these patients. Importantly, a comparison group undertaking the same resistance training combined with aerobic training but without the impact loading did not exhibit the same benefit to bone health. We found these contrasting outcomes, even though such an exercise program previously has been demonstrated to reduce osteoporosis in other patient populations. Had we compared a combination of resistance and aerobic training to usual care, we would have concluded that exercise was ineffective for preventing bone loss in men on ADT — a false conclusion because the wrong medicine was trialed.
The complexity of exercise prescription goes even deeper. In our study, bone loss was attenuated both at the lumbar spine and femoral neck, but not at the trochanter site. We believe this was due to the specific exercises we selected for our protocol-imposed bone loading only in the sagittal plane. Other studies in the same patient population have used movements that incorporated bone loading in all three planes and reported significant bone gain at more skeletal sites.
Further, we reported increases in appendicular skeletal mass in the patients undertaking a program of combined impact and resistance training but observed a lack of such effects in patients doing a combination of aerobic and resistance training. This, despite the fact that the resistance exercise performed was identical between the two groups. This is noteworthy and may suggest a potential “interference effect of aerobic exercise” that constrained the muscle hypertrophy drive of resistance training. While this phenomenon has been reported in young trained individuals, the interference is usually negligible in healthy older adults and so combination training can be performed without concern. However, it could be that androgen suppression results in a catabolic environment such that even modest aerobic exercise compromises muscle size and strength gains. This is problematic as these older, chemically castrated male patients with cancer exhibit rapid muscle loss and decline to a sarcopenic condition.
Findings such as ours point to the need for tailored exercise prescription for cancer patients by which health issues causing the greatest morbidity and mortality risk are prioritized. Mode and dosage of exercise should specifically target these issues in priority order — recognizing that exercise is not a single medicine. Further, it is increasingly evident that exercise prescriptions must be periodized for cancer patients to reduce mode interference. Periodization also elicits a continued disturbance to homeostasis to drive adaptations in metabolic, endocrine and immune functions. In addition, it also prepares the patient for more intense exercise phases, such as the impact training or enhancing their readiness for challenging surgical and chemotherapy interventions. A cancer diagnosis initiates what for many will be the ultimate marathon; and all patients deserve the optimal preparation, event support and recovery plan.