Poster Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2019

Cerebral blood flow during high-intensity interval exercise in breast cancer survivors (#339)

Joseph M Northey 1 2 , Patrice Brassard 3 4 , Ashley Ikin 1 , Ben Rattray 1 2
  1. Discipline of Sport and Exercise Science, Faculty of Health, University of Canberra, Canberra, ACT, Australia
  2. UC Research Institute of Sport and Exercise, University of Canberra, Canberra, ACT, Australia
  3. Research Center of the Institut Universitaire de Cardiologie Pneumologie de Québec, Quebec, Canada
  4. Department of Kinesiology, Faculty of Medicine, Laval University, Quebec City, Quebec, Canada

Background: It is unclear how the homeostatic challenge of high-intensity interval training (HIIT) affects cerebral hemodynamics, a concern in breast cancer survivors given the potential for cerebrovascular damage if flow regulation is impaired.

Aim: Describe the cerebral hemodynamic responses of breast cancer survivors to a bout of HIIT.

Methods: Seven breast cancer survivors (mean±SD: age 60±8) underwent an initial graded exercise test, a familiarisation of the HIIT protocol, and a HIIT session in which their responses were recorded. The HIIT protocol was conducted on a cycle ergometer and consisted of a 5 min warm-up followed by 4 x 30 s high-intensity intervals (in which participants were asked to do as much as work as possible over the 4 efforts) alternating with 2 min of active recovery and a cool-down period. Middle cerebral artery mean flow velocity (MCAVmean), the fraction of carbon dioxide in expired air (PETCO2), mean arterial pressure (MAP) and heart rate were recorded throughout.

Results: During each high-intensity interval, MCAVmean showed a small increase, before declining steadily. The early increase in MCAVmean matched the initial surge in MAP, before declining in response to the reduction in PETCO2 observed during each interval. Overall, MCAVmean reached values below the resting baseline during the third or fourth interval, matching the profile of PETCO2.

Conclusion: The present study demonstrated that although there is an increase in cerebral blood flow early in a HIIT session, these increases are relatively modest in cancer survivors. A hyperventilatory-mediated hypocapnia transiently reduced cerebral blood flow and may place participants at a higher risk of issues such as syncope or reduced cognitive function. Alternatively, this hyperventilatory-induced hypocapnia could be interpreted as a protective mechanism against potential damage associated with elevated mean arterial pressure.