James R. Vallerand

Predictors of adherence to different types and doses of supervised exercise during breast cancer chemotherapy

BackgroundExercise is beneficial for breast cancer patients during chemotherapy but adherence to different types and doses of exercise is a challenge. The purpose of this study was to examine predictors of adherence to different types and doses of exercise during breast cancer chemotherapy in a multicenter randomized controlled trial.MethodsBreast cancer patients in Edmonton, Vancouver, and Ottawa, Canada receiving chemotherapy (N = 301) were randomized to a standard dose of 25–30 minutes of aerobic exercise (STAN), a higher dose of 50–60 minutes of aerobic exercise (HIGH), or a higher dose of 50–60 minutes of combined aerobic and resistance exercise (COMB). Predictors included demographic, medical, fitness, and quality of life variables. Exercise adherence was measured as the percentage of supervised exercise sessions completed.ResultsOverall adherence to the supervised exercise sessions was 73% (SD = 24%). In a multivariate regression model, six independent predictors explained 26.4% (p < 0.001) of the variance in exercise adherence. Higher exercise adherence was achieved by breast cancer patients in Vancouver (p < 0.001), with fewer endocrine symptoms (p = 0.009), randomized to STAN (p = 0.009), with fewer exercise limitations (p = 0.009), receiving shorter chemotherapy protocols (p = 0.015), and with higher VO2peak (p = 0.017). Disease stage (p for interaction = 0.015) and body mass index (p for interaction = 0.030) interacted with group assignment to predict adherence. For disease stage, patients with stage I/IIa disease adhered equally well to all three exercise interventions whereas patients with stage IIb/III disease adhered better to the STAN intervention than the two higher dose exercise interventions. For body mass index, healthy weight patients adhered equally well to all three exercise interventions whereas overweight patients adhered best to STAN and worst to COMB; and obese patients adhered best to STAN and worst to HIGH.ConclusionsDeterminants of exercise adherence in breast cancer patients receiving chemotherapy are multidisciplinary and may vary by the exercise prescription.

Subgroup effects in a randomised trial of different types and doses of exercise during breast cancer chemotherapy

Background:The Combined Aerobic and Resistance Exercise Trial tested different types and doses of exercise in breast cancer patients receiving chemotherapy. Here, we explore potential moderators of the exercise training responses.Methods:Breast cancer patients initiating chemotherapy (N=301) were randomly assigned to three times a week, supervised exercise of a standard dose of 25–30 min of aerobic exercise, a higher dose of 50–60 min of aerobic exercise, or a higher dose of 50–60 min of combined aerobic and resistance exercise. Outcomes were patient-reported symptoms and health-related fitness. Moderators were baseline demographic, exercise/fitness, and cancer variables.Results:Body mass index moderated the effects of the exercise interventions on bodily pain (P for interaction=0.038), endocrine symptoms (P for interaction=0.029), taxane/neuropathy symptoms (P for interaction=0.013), aerobic fitness (P for interaction=0.041), muscular strength (P for interaction=0.007), and fat mass (P for interaction=0.005). In general, healthy weight patients responded better to the higher-dose exercise interventions than overweight/obese patients. Menopausal status, age, and baseline fitness moderated the effects on patient-reported symptoms. Premenopausal, younger, and fitter patients achieved greater benefits from the higher-dose exercise interventions.Conclusions:Healthy weight, fitter, and premenopausal/younger breast cancer patients receiving chemotherapy are more likely to benefit from higher-dose exercise interventions.

Explaining the Aerobic Exercise Intention-behavior Gap in Cancer Survivors.

OBJECTIVES We sought to quantify the aerobic exercise intention-behavior gap in hematologic cancer survivors (HCS), and examine the correlates of intention formation and translation using the multi-process action control framework. METHODS HCS (N = 606) completed a survey reporting their aerobic exercise motivation and behavior. The correlates of intention formation and translation were analyzed using separate logistic regressions. RESULTS Overall, 71% (N = 428/606) of HCS intended to do aerobic exercise, 44% (N = 267/606) met aerobic exercise guidelines, and 60% of intenders (N = 256/428) translated their intention into aerobic exercise. Attitude (OR = 1.9), perceived control (OR = 1.5), younger age (OR = 2.0), and higher education (OR = 2.1) explained intention formation (all ps ≤ .001). A sense of obligation/regret (OR = 2.8), self-regulation over alternative activities (OR = 1.6), attitude (OR = 2.0), perceived control (OR = 1.7), planning (OR = 1.7), being female (OR = 2.0), and younger (OR = 3.0) explained intention translation (all ps < .005). CONCLUSIONS Forming an intention is insufficient for many HCS to meet aerobic exercise guidelines. Interventions targeting the determinants of both intention formation and translation may be most effective in promoting aerobic exercise in cancer survivors.

Correlates of meeting the combined and independent aerobic and strength exercise guidelines in hematologic cancer survivors

BackgroundMost previous research on the correlates of physical activity has examined the aerobic or strength exercise guidelines separately. Such an approach does not allow an examination of the correlates of meeting the combined guidelines versus a single guideline, or one guideline versus the other. Here, we report the prevalence and correlates of meeting the combined and independent exercise guidelines in hematologic cancer survivors (HCS).MethodsIn a population-based, cross-sectional survey of 606 HCS from Alberta, Canada using a mailed questionnaire, we obtained separate assessments of aerobic and strength exercise behaviors, as well as separate assessments for motivations, regulations, and reflective processes using the multi-process action control framework (M-PAC).ResultsOverall, 22% of HCS met the combined exercise guideline, 22% met aerobic-only, 10% met strength-only, and 46% met neither exercise guideline. HCS were more likely to meet the combined guideline over the aerobic-only guideline if they had no children living at home, and over both the aerobic and strength-only guidelines if they had completed university. As hypothesized, those meeting the combined guideline also had a more favorable strength-specific M-PAC profile (i.e., motivations, regulations, and reflective processes) than those meeting the aerobic-only guideline, and a more favorable aerobic-specific M-PAC profile than those meeting the strength-only guideline. Interestingly and unexpectedly, HCS meeting the combined guidelines also reported significantly greater aerobic-specific perceived control, planning, and obligation/regret than those meeting the aerobic-only guideline, and greater strength-specific perceived control, planning, and obligation/regret than those meeting the strength-only guideline.ConclusionsFew HCS are meeting the combined exercise guidelines. M-PAC based variables are strong correlates of meeting the combined guidelines compared to aerobic or strength only guidelines. Strategies to help HCS meet the combined guidelines may need to promote more favorable behavioral regulations and reflective processes for both types of exercise rather than just the type of exercise in which HCS are deficient.

Predictors of Adherence to Different Volumes of Exercise in the Breast Cancer and Exercise Trial in Alberta

BACKGROUND Exercise demonstrates a dose-response effect on many health outcomes; however, adhering to higher doses of exercise can be challenging, and the predictors of adherence may differ based on exercise volume. PURPOSE To examine the predictors of adherence to two different volumes of aerobic exercise within the Breast Cancer and Exercise Trial in Alberta (BETA). METHODS In BETA, we randomized 400 inactive but healthy postmenopausal women to either a moderate volume (150 min/week) or a high volume (300 min/week) of aerobic exercise for 1 year. We collected data on several predictors of exercise adherence at baseline and used linear and mixed-effect models to determine predictors of exercise adherence to exercise volume and overall. RESULTS Adherence was higher in the moderate-volume group (84.5%) compared with the high-volume group (75.2%; p < .001). There were no statistically significant interactions between predictors of exercise adherence and exercise volume. Overall, we found that exercise adherence was predicted by randomization group, body mass index (BMI), employment status, and physical health. Adherence was 8.6% lower in the high-volume versus moderate-volume group, 6.7% lower for women working full time versus not, 0.8% lower per BMI increase of 1 kg/m2, and 0.5% higher per unit of physical health. CONCLUSIONS Adherence to high-volume aerobic exercise was more challenging than for moderate-volume aerobic exercise, but the predictors of adherence were similar. Moreover, few factors were major predictors of exercise adherence in this setting suggesting that well-controlled efficacy trials that produce high adherence rates may reduce the influence of individual characteristics on exercise adherence. TRIAL REGISTRATION NCT1435005.