Fong et al. systematically evaluated the effects of ‘physical activity’ in adult patients after completion of main treatment related to cancer.(1) Nevertheless, the effects of (increased) physical activity on health indicators were not studied, and changes in daily physical activity levels were not reported.(2) Indeed, the characteristics of the 34 randomized controlled trials included in this meta-analysis show that Fong et al. mostly studied the effects of structured exercise training programs including aerobic and/or resistance exercises.(1) Although physical activity and exercise training are closely related, these are two distinct domains with their own definitions. Physical activity refers to ‘body movement that is produced by the contraction of skeletal muscles and that increases energy expenditure’; while exercise refers to ‘planned, structured, and repetitive movement to improve or maintain one or more components of physical fitness’.(3)

Therefore, we believe that the conclusion of this meta-analysis should be that structured exercise training is associated with clinically important positive effects on physical functions and quality of life in patients who had completed their treatment for cancer. Whether and to what extent these interventions will also increase daily physical activity levels in cancer survivors remains currently unknown.

Dr. Martijn A. Spruit, scientific advisor
Program Development Center, CIRO+, center of expertise for chronic organ failure
Horn, the Netherlands

Dr. Emiel F.M. Wouters, professor in respiratory medicine
Dept. of Respiratory Medicine, Maastricht University Medical Centre (MUMC+)
Maastricht, the Netherlands

References

1. Fong DY, Ho JW, Hui BP et al. Physical activity for cancer survivors: meta-analysis of randomised controlled trials. Bmj 2012;344:e70.

2. Bravata DM, Smith-Spangler C, Sundaram V et al. Using pedometers to increase physical activity and improve health: a systematic review. Jama 2007;298:2296-304.

3. Chodzko-Zajko WJ, Proctor DN, Fiatarone Singh MA et al. American College of Sports Medicine position stand. Exercise and physical activity for older adults. Med Sci Sports Exerc 2009;41:1510-30.

Competing interests: None declared