Abstract and Introduction
Purpose: Current evidence suggests many health benefits from physical activity during and after cancer treatment. However, the optimal exercise program for cancer survivors has not yet been established. The purpose of this meta-analysis was to summarize evidence for the efficacy of resistance training (RT) interventions to improve muscle strength and body composition among adult cancer survivors. We also investigate potential dose–response relationships between intensity, duration, and frequency of RT and assessed outcomes.
Methods: A systematic literature review of the Clinical Trial Register, Cochrane Trial Register, MEDLINE, and EMBASE literature databases was undertaken. Studies were included if they were randomized controlled trials (RCT) comparing RT with an exercise or nonexercise control group in cancer survivors during and after treatment. Thirteen articles from 11 RCT met our inclusion criteria. We performed a random-effects meta-analysis to determine weighted mean differences (WMD) with 95% confidence intervals using the Cochrane Review Manager 5.0.25. A random-effects metaregression model was performed to examine dose–response relationships between RT variables and assessed outcomes.
Results: Quantitative evidence shows a large effect of RT on lower-limb and upper-limb muscle strength (WMD: +14.57 kg, P = 0.0005 and +6.90 kg, P < 0.00001, respectively) and moderate effects on lean body mass and percentage of body fat (WMD: +1.07 kg, P < 0.0001 and -2.08%, P = 0.003, respectively). A small positive effect of RT was noted on Functional Assessment of Cancer Therapy–Fatigue (P = 0.05). Upper-limb muscle strength and percentage of body fat improved to a greater extent when RT interventions were of low to moderate intensity (<=75% one-repetition maximum, P = 0.042).
Conclusions: RT was shown to be associated with clinically important positive effects on muscular function and body composition in patients during treatment or in long-term follow-up.
Cancer is the second leading cause of death in the United States, with breast and prostate cancer being the most frequently diagnosed cancers for women and men, respectively,. There are numerous side effects to cancer treatment, which often include muscle wasting or atrophy, reduced physical functioning, unfavorable changes in body composition, and depression and fatigue. A decrease in physical activity levels associated with other side effects, such as loss of appetite, can intensify muscular wasting and consequently loss of overall body strength, leading patients to experience a negative spiraling effect that further exacerbates the sense of fatigue. This loss of muscular strength together with a reduction in aerobic fitness makes it difficult to perform simple daily activities, significantly compromising the quality of life in cancer patients as well as contributing to increased rates of mortality.[27,28] Recent systematic reviews have shown that resistance training (RT) has the power to combat many of the side effects of cancer treatment and, thus, can be of significant benefit to patients in the short and long term.[10,15,16] Benefits include improved muscle strength and physical functioning and reduced fatigue, all potentially leading to improved quality of life. However, this has so far only been investigated for very few cancer types.
Normal aging is associated with a decline in muscle mass between 5% and 10% each decade after age 50 yr, averaging approximately 0.4 kg of lean weight loss per year after the fifth decade of life. Although weight loss occurs in roughly half of cancer patients, in cachexia, the weight loss represents a marked loss of predominantly skeletal muscle. In cachectic patients, a loss of 25% of body weight represents an approximately 75% reduction in skeletal muscle protein. Approximately 20% of cancer deaths are attributed to cachexia.
Numerous studies have demonstrated that relatively brief sessions of regular RT can increase muscle mass in adults of all ages through the 10th decade of life. Effects of RT are more pronounced if exercises are muscle site specific, high intensity, and when combined with calcium and vitamin D intake.[8,31] Furthermore, RT can provide functional benefits and improvements in overall health and well-being, including increased bone mineral density (BMD), improved physical performance,[25,71] and cardiovascular health. Therefore, RT may have beneficial effects in cancer patients in terms of reducing muscle wasting or regaining lost muscle mass as well as improving muscle function and a diversity of biomarkers. In turn, this may lead to reduced fatigue levels and an overall enhancement in mental health.
The current systematic review was undertaken 1) to perform a meta-analysis of randomized controlled trials (RCT) regarding the effect of RT on muscle function, body composition, and fatigue both during and after cancer treatment and (2) to investigate the potential for a dose–response relationship between intensity, duration, and frequency of RT and assessed outcomes.
Med Sci Sports Exerc. 2013;45(11):2080-2090. © 2013 American College of Sports Medicine