Effect of home-based smartphone-supported high-intensity interval training on cardiorespiratory fitness in breast cancer survivors: A randomized controlled trial of the habit-B program

ABSTRACT

Background: A strategy for maintaining and/or improving cardiorespiratory fitness (CRF) in the growing population of cancer survivors is of major clinical importance in the COVID-19 era. With the aim of increasing CRF, recent studies have focused on the use of high-intensity interval training (HIIT) in supervised experimental settings, which appeared to be more beneficial than usual care in cancer survivors at all stages of treatment and aftercare. However, the effect of unsupervised HIIT on increasing CRF in breast cancer survivors is not known. Purpose: To determine whether the newly developed habit-B program, which involves home-based smartphone-supported HIIT using body-weight exercises, improves CRF in early-stage breast cancer survivors. We hypothesized that the habit-B program would improve VO2peak compared with a control group. Methods: This single-center, 12-week, parallel-group, single-blind, randomized controlled trial involved 50 women with stage I-IIa breast cancer, aged 20 to 59 years, who had completed initial treatment except for hormone therapy. Participants wore a smartwatch and were randomized to either the exercise or control group from May 27, 2019 through November 30, 2020. The planned sample size was 60 Spatients to detect the increase of 2.0 ml/kg/min change in VO2peak with a standard deviation of 2.6 ml/kg/min, one-sided significance level of 2.5% and 80% power. The exercise group underwent home-based HIIT using a smartphone and a Fitbit Versa thrice weekly for 12 weeks (three times per week). The primary outcome was the 12-week change in peak oxygen uptake (VO2peak;mL/kg/min) between the groups. Other outcomes included muscle strength, 6-min walk test, resting heart rate, physical activity, fatigue, safety, and quality of life. Results: Of the 50 participants, 44 (exercise group, n=23;control group, n=21) completed the CRF assessment and 6 did not because of issues related to the COVID-19 pandemic. The change in VO2peak increased significantly in the exercise group (0.9 [95%CI, 0.1 to 1.7]) compared with the control group (-0.8 [95%CI,-1.5 to-0.1]) (mean difference, 1.7 [95% CI, 0.7 to 2.7], p <.01). Leg strength also increased significantly in the exercise group compared with the control group (mean difference, 13.5 [95% CI, 2.9 to 24.1], p <.01). Changes in other outcomes were not significantly different between the groups. Conclusion: A home-based HIIT intervention can lead to improved cardiorespiratory fitness and muscle strength in early-stage breast cancer survivors;however, a multicenter pragmatic clinical trial is required to confirm the benefits of the habit-B program.