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

INTERVENTION: 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 1 CONDITION: Breast Cancer; ; Breast Cancer Cancer ‐ Breast PRIMARY OUTCOME: Cardiorespiratory fitness ; Assessment of maximal aerobic power; A maximal graded incremental cycling test was conducted to determine VO2 Peak, intervention relative intensity and pre and post intervention fitness levels (High‐Performance Ergometer, Schoberer Rad MeBtechnik, Germany). Participants respired through an oro‐nasal mask (Hans‐Rudolph 7450 Series V2TM Mask, CareFusion, France), breath by breath cardiopulmonary data (Vyntus CPX, Metabolic Cart, Jaeger, Germany) were measured to calculate VO2Peak in the cardiopulmonary exercise test. Throughout the test an Accredited Exercise Physiologist monitored participants with 12‐Lead electrocardiogram (ECG). Blood pressure was assessed via sphygmomanometry and was recorded every two minutes.; ; The protocol commenced with a five minute warm up at 20 watts. Thereafter, the workload was increased by = 20 watts each minute until three of the following criteria were reached: 1) no change in oxygen consumption with increasing workload, 2) respiratory exchange ratio > 1.1, 3) heart rate within 10% of age predicted maximal heart rate or, 4) inability to maintain pedalling cadence. Participants self‐selected peddling cadence > 60 revolutions per minute. In addition, exercise was terminated on the presentation of volitional fatigue, abnormal changes in blood pressure, or ECG abnormalities. ; ; ; [Participants were asked not to consume food or caffeine or participate in exercise within two hours prior to pre‐and post‐testing. ] ; ; ; SECONDARY OUTCOME: Heart rate variability was assessed using a Suunto watch and chest belt (Suunto model t6, Finland) and HRV was analysed using software (Kubios heart rate variability software version 2.0; Biosignal Analysis and Medical Imaging Group, Department of Physics, University of Kuopio, Kuopio, Finland).[Participants were asked not to consume food or caffeine or participate in exercise within two hours prior to pre‐and post‐testing. Assessments were carried out within the 2‐4 days prior to commencement of the program and within 2‐4 days following completion. HRV and salivary biomarker measures were taken prior to cardiorespiratory fitness testing.] Saliva samples (s‐AA) were obtained using IPRO Oral Fluid Collection (OFC) kits that were labelled and provided to each participant. The OFC kits collect 0.5mL of oral fluid and contain a colour changing volume adequacy indicator within the swab, giving collection times typically in the range of 20‐50 seconds. ; Baseline saliva samples were collected at two‐time points on the same day at home, two days before and after the intervention commenced and ended (immediately upon waking whilst still in bed and 30 min post waking). The participants received training on the saliva collection procedure during their first visit to the laboratory. They were requested to adhere as closely as possible to the standardised collection guidelines, which was carried out in their home. Participants recorded the time each saliva sample was collected. All samples were frozen immediately after collection in home freezers and kept frozen until reaching the laboratory, upon which they were stored at ‐20 °C until analysis. ; [Participants were asked not to consume food or caffeine or participate in exercise within two hours prior to pre‐and post‐testing. Assessments were carried out within the 2‐4 days prior to commencement of the program and within 2‐4 days following completion. HRV and salivary biomarker measures were taken prior to cardiorespiratory fitness testing.] Saliva samples (s‐cortisol) were obtained using IPRO Oral Fluid Collection (OFC) kits that were labelled and provided to each participant. The OFC kits collect 0.5mL of oral fluid and contain a colour changing volume adequacy indicator within the swab, giving collection times typically in the range of 20‐50 seconds. ; Baseline saliva samples were collected at two‐time points on the same day at home, two days before and after the intervention commenced and ended (immediately upon waking whilst still in bed and 30 min post waking). The participants received training on the saliva collection procedure during their first visit to the laboratory. They were requested to adhere as closely as possible to the standardised collection guidelines, which was carried out in their home. Participants recorded the time each saliva sample was collected. All samples were frozen immediately after collection in home freezers and kept frozen until reaching the laboratory, upon which they were stored at ‐20 °C until analysis. ; [Participants were asked not to consume food or caffeine or participate in exercise within two hours prior to pre‐and post‐testing. Assessments were carried out within the 2‐4 days prior to commencement of the program and within 2‐4 days following completion. HRV and salivary biomarker measures were taken prior to cardiorespiratory fitness testing.] Saliva samples (s‐IgA) were obtained using IPRO Oral Fluid Collection (OFC) kits that were labelled and provided to each participant. The OFC kits collect 0.5mL of oral fluid and contain a colour changing volume adequacy indicator within the swab, giving collection times typically in the range of 20‐50 seconds. ; Baseline saliva samples were collected at two‐time points on the same day at home, two days before and after the intervention commenced and ended (immediately upon waking whilst still in bed and 30 min post waking). The participants received training on the saliva collection procedure during their first visit to the laboratory. They were requested to adhere as closely as possible to the standardised collection guidelines, which was carried out in their home. Participants recorded the time each saliva sample was collected. All samples were frozen immediately after collection in home freezers and kept frozen until reaching the laboratory, upon which they were stored at ‐20 °C until analysis. ; [Participants were asked not to consume food or caffeine or participate in exercise within two hours prior to pre‐and post‐testing. Assessments were carried out within the 2‐4 days prior to commencement of the program and within 2‐4 days following completion. HRV and salivary biomarker measures were taken prior to cardiorespiratory fitness testing.] INCLUSION CRITERIA: Participants were included in this study if they were; (1) females between the ages of 50 and 75 years, (2) sedentary as classified by the American College of Sports Medicine, (3) were within two years post‐cancer treatment and (4) did not take blood pressure medication (angiotensin‐converting enzyme inhibitors or angiotensin receptor blockers or calcium channel blockers or beta‐blockers), (5) did not have brain or bone metastasis or (6) a diagnosis of secondary cancers and (7) were able to perform the exercise sessions on a stationary cycle ergometer (Monark 828E Ergometer).