Abstract
Background: We previously reported a pilot randomized controlled trial in prostate cancer survivors suggesting that resistance training (RT) 3 days/week versus 2 days/week may improve physical functioning but may also blunt psychosocial improvements. Here, we explore potential motivational explanations for this paradoxical effect. Methods: Prostate cancer survivors (N=30) were randomized to 12 weeks of supervised RT either 3 days/week (n=16) or 2 days/week (n=14). Using the theory of planned behavior, we assessed patient preference for group assignment, perceived difficulty (including specific barriers), perceived benefits (including specific benefits), perceived enjoyment, and perceived support for the RT program. Results: Patient preference for group assignment was balanced at pre-randomization and did not change after the intervention. At postintervention, there were potentially meaningful differences suggesting that the 3 days/week group perceived less support (d=-0.40; p=0.27), more difficulty (d=+0.36; p=0.34), and fewer benefits (d=-0.30; p=0.37) from the RT program. More specifically, the 3 days/week group reported less benefit for self-esteem (d=-0.92; p=0.010), physical functioning (d=-0.82; p=0.012), fatigue (d=-0.73; p=0.041), cardiovascular endurance (d=-0.67; p=0.058), and happiness (d=-0.64; p=0.066). Moreover, there were potentially meaningful differences suggesting the 3 days/week group perceived more barriers to the RT program including feeling sick (d=+0.42; p=0.27), traveling to/from the fitness center (d=+0.36; p=0.32), and other medical problems (d=+0.25; p=0.49). Conclusions: These preliminary data suggest that perceptions of less support, fewer benefits, and more barriers may explain why prostate cancer survivors experienced fewer psychosocial benefits from a 3rd day/week of RT. These motivational explanations should be investigated in larger trials.Acknowledgments: Kerry S. Courneya is supported by the Canada Research Chairs Program.