Breast Cancer and the Athlete: Part 1, Exercise Intensity

By SUSAN GILCHRIST, M.D., M.S.

In 2016, my team and I published a case-report (Savage, Medicine & Science in Sports and Exercise, 2016 Oct - link at the bottom of the article) about one of my patients who had been diagnosed with HER2+ breast cancer and was also a highly trained athlete. She had seen me in clinic hoping to understand whether she could continue her exercise training during breast cancer treatment. She made it very clear that being highly active was an essential part of who she was as a person. I was determined to help her through this journey.

As a first step, we performed a cardiopulmonary exercise test (CPET). In this test, a patient starts walking on a treadmill, then gradually goes up an incline every few minutes resulting in a run to exhaustion. While exercising, the patient breathes through a facemask to measure the efficiency of oxygen intake and carbon dioxide (C02) output; this provides information about the patient’s fitness level and overall cardiopulmonary health. Peak heart rate (PHR) is also obtained at the end of maximal exercise as this helps guide exercise intensity for future workouts.

Exercise intensity is important when creating a training regimen. Intensity of exercise should be in a person’s sweet spot – the point in which they are not doing too little (and thus not getting fitter) or too much (outside of their limits causing injury). A general rule of thumb is that if you can talk but not sing during exercise you are likely at a moderate level of intensity. However, for training purposes the most accurate way to guide intensity during workouts is via heart rate obtained during a CPET. For example, if a person’s PHR at the end of exercise is 180 bpm, then the moderate-intensity HR goal is ~ 130 bpm (70% of PHR).

While moderate-intensity exercise is the recommended level of intensity by all of the major guidelines and professional societies, I can tell you that intensity goals of the highly trained athlete varied throughout her cancer journey (chemotherapy, HER2+ agents, surgery, radiation, additional surgeries, thyroid dysfunction) from just moving (light), to moderate, to vigorous-intensity exercise. This is outlined in manuscript. However, it is important to note that she did not perform vigorous or high-intensity exercise (>85% PHR) while she was receiving anthracycline-based chemotherapy. Anthracyclines are a stress to the heart and so is high-intensity exercise – thus, I am not a fan of combining the two together.

That being said, exercise intensity is only one aspect of a training regimen. We did personalize other aspects of her workout to keep her engaged and she was able to eventually get back to her baseline fitness levels. Stay tuned how she was able to pull that off next week.

If you were given HR goals to monitor exercise intensity, how would you track your heart rate and why?

a) I wouldn’t
b) Heart rate monitor – like a wearable device on my wrist
c) Polar monitor around my chest
d) I would put my hands on an exercise machine and wait for the reading
e) Feel my own pulse and count
f) Measure heart rate by placing my fingertip on front of the camera light of my phone

Link to Case Report: Medicine & Science in Sports and Exercise, Oct. 2016 https://www.ncbi.nlm.nih.gov/m/pubmed/27187100/