My body's reaction to the chemotherapy cream that I'm using for a skin cancer on my left ear is following a definite pattern. I use the cream 5 days per week, Monday night through Friday night. My wakeup heart rate has been low (typically 51 or 52) on Monday morning due to not having used the cream for two days. I've thus had good runs on Monday morning. However, during the week my wakeup heart rate increases, usually to 59 or 60, although during one week of using the cream, my heart rate increased to 75. On Saturdays, my wakeup heart rate has been about 55, and I've had to reduce the distance of my Saturday runs due to being tired.
My wakeup heart rate this morning was 55, as it has been in past Saturdays, and I've decided to take a rest day rather than likely run a reduced distance. By taking a rest day, I'll hopefully be stronger for my Monday run. If my wakeup heart rate is low on Monday and I feel fine, I'll run 6.6 miles instead of my normal 5 miles.