I am a 41 year old personal trainer and have been working out for over 20 years. My resting heart rate is about 50 bpm, and I usually keep my heart rate at about 153 when doing cardio. I was surprised to find my heart rate climbing to almost 170 during a spinning class last week. I felt okay, but I was working hard. I tried slowing it down a bit, but it stayed over 160 for about 15 to 20 minutes before it began coming down. Then for the rest of the class, it was about 158-ish. Is this dangerous? The instructor said her heart rate does the same thing, and I should start out slower. She also said this is probably due to the fact that I only spin about once a week (this also happens to me when I bike outdoors on hilly terrain), and my body was not used to the intensity. My heart rate dropped very quickly during the cool down part of the class and did not remain high. I am planning to talk to my doctor this week, but do you have any input into this?
Although this is a new occurrence to you, it is not entirely uncommon, even in the well-trained fitness community.
This is a difficult question to answer because there are so many "intangibles" that may factor as potential causes. For example, you did not disclose:
- Heart rate monitor or pulse-rate method
- Pre-workout stimulants or supplements
- Amount of life stress?
- Pre-existing conditions such as asthma (exercise induced)
- Post-viral fatigue (from influenza)
- Over the counter cold medications
- Did nausea accompany your elevated heart rate?
- How many days/week do you exercise at this intensity?
These are just a few items that could narrow the list of possible conditions, if one truly existed. But your question was, "Is this dangerous?" To put it simply: yes! Better to error on the side of conservatism when it comes to cardiac function. You are well aware of the benefits of cardiovascular training. Increased anaerobic threshold and aerobic capacity are just an example.
You reportedly train at a heart rate of 85 percent regularly. While on the spin cycle, you noticed an increase to approximately 170 bpm (95 percent of your maximum heart rate). Prolonged exercise at the higher ends of the heart rate training spectrum decreases overall benefit. And at 41 years old, what benefit are you specifically working toward? Are you on a maintenance program or advanced training program with pre-designed workloads at given heart rate intensities? These are just questions to ask yourself to design the most appropriate cardiovascular fitness program.
I am glad to see you were consulting a physician. Hopefully, the results of the exam were normal, although many people with documented cases of atrial fibrillation and cardiomyopathy continue to participate in regular cardiovascular and cross training fitness programs.