The Impact of High-Intensity Interval Training Exercise on Breast Cancer Survivors: A Pilot Study to Explore Fitness, Cardiac Regulation and Biomarkers of the Stress Systems

Seventeen participants (62 ± 8 years) were randomly assigned to; 1) high intensity interval training (HIIT; n = 6); 2) moderate-intensity, continuous aerobic training (CMIT; n = 5); or 3) a wait-list control (CON; n = 6) for a 12-week (36 session) stationary cycling intervention. Cardiorespiratory fitness (VO2peak), resting HRV and salivary biomarkers were measured at baseline 2-4 d pre-intervention and 2-4 d post the last exercise session. Exercise groups Participants in the two exercise interventions attended the University of Canberra laboratory three times per week for twelve weeks (up to 36 sessions). Participants could choose from a series of scheduled timeslots where supervision was provided across the week and where compliance could be recorded. Each session was conducted on the Monark cycle ergometer and lasted 20-30 mins depending on the allocated intervention group. Participant numbers in each session were between 1 and 4 dependent on number of participants attending at each session. Sessions were fully supervised by an experienced Accredited Exercise Physiologist or Accredited Exercise Scientist. Participant’s heart rate (HR) was continuously measured and recorded during all exercise sessions using a heart rate monitor (Polar FT40, Finland). Rating of perceived exertion (RPE) was monitored and recorded throughout each session (Borg 6-20). Exercise sessions started and finished with a 5-minute warm up and cool down, completed on the cycle ergometers at ~50% of their maximal power (watts) achieved in the baseline incremental exercise test. The CMIT group cycled for 30 minutes in total, with 20 minutes at 55-65% of their maximal power. The workload was adjusted over 12 weeks within this range to ensure their RPE remained between 9 and 13 on the Borg scale . The HIIT group completed seven 30 second intervals (as hard as they could) with 2 minutes of active recovery between each. Participants were instructed to increase their cadence to between 95 and 115 RPM to ensure consistent performance. Participants initially completed four intervals in each session, and this was gradually increased to achieve the target of seven intervals by week four. Control group Participants in the waitlisted control group (CON) were asked to continue with their current lifestyle for 12 weeks after the baseline tests. After completion, the participants from the CON group were offered the 12 week fully supervised intervention.