QUESTION: I’m 58 and don’t understand what’s happening to my heart during longer road rides. After about 90 minutes of steady riding at around 80% of my max heart rate, it gradually climbs to 90% even though my speed, cadence and energy output remain constant. Why? — Len M.
RBR REPLIES: I suspect you’re experiencing a common phenomenon known as “cardiac drift.” This is a gradual rise in heart rate after about an hour of steady aerobic work, even though power output isn’t increased. It’s caused by dehydration and other factors, although physiologists haven’t figured out all of them. Merely staying hydrated won’t eliminate cardiac drift, but it helps delay it.
So, use plenty of sports drink, and continue training to gradually extend the time before your heart rate drifts higher.
Another approach is to vary your workouts so you aren’t always doing the steady rides you’ve implied are your habit. Instead, each week do a couple of rides quite easily at about 60-70% of your max heart rate. Do two longer rides at 80% like you’ve described. And add an interval or climbing day that raises your heart rate to 90% or higher for short periods, alternated with easy cruising for recovery.
Funny, my “cardiac drift” goes DOWN as a ride progresses. That’s part of why I don’t bother with a HRM anymore, as I know it’s not giving me an accurate assessment of my efforts.
So, I’m 71 and use an Apple Watch when I ride, paired with Strava. Riding now for more than 50 years continuously. Consider myself very fit. Weigh 132 wringing wet. I don’t race but ride with groups that move along fairly quickly (+ 17 mph over 40 / 50 miles). According to Strava via my watch, my heart rate consistently exceeds what we’d call my max (using 205.8 – age x .685). I have no trouble hitting 170 bpm and higher even. Jamming uphill watch/Strava often tells me I hit 180 bpm.
Before using the watch, I paid no attention to my heart rate with no issues that I know of. I must say this now puzzles me and I wonder if the damn thing is going to explode. Does anyone know if wearing a chest HRM would be more accurate? And is the watch likely to be so far off? Is it possible 180 is an accurate recording, and what are effects of consistently exceeding what would be generally considered my max? Anyone else out there having similar experience? Thanks!
If you’ve stayed fit over the years, it’s likely you’d have a higher heart rate max than a sedentary person or someone who didn’t train very much. A heart rate monitor strop is definitely a lot more accurate, so it’s also possible that the Apple watch is showing a number a little bit off from the real number. Polar and Wahoo both make Bluetooth straps that will sync with your iphone, if you don’t use a Garmin or other bike computer that reads it.
Here’s Joel Friel on max heart rates, where he is skeptical of the formula in general:
https://joefrielsblog.com/max-heart-rate-and-performance/
I’m 74 and when I recently told my internist that I occasionally hit the low 180s on hills, he told me that is impossible, citing the “rule”. I assured him it’s true, based on a Polar HRM with a chest strap. He had me wear a Zio monitor for a week. On one of the days I went out and hit the hills and saw 175 on the Polar. The Zio results confirmed this, as well as showing 7 straight days of normal sinus rhythm. QED.
Those numbers come from an average population and don’t necessarily apply to a well trained athlete who has been exercising for decades. There are more and more 70 plus athletes who are still racing and training in a structured way, so it’s not surprising to me that there are people like you who can still hit the low 180s. But I’ll bet there aren’t very many! That’s a high number.
I use an Apple Watch and Garmin with chest strap and find them recording near the same HR almost beat for beat. I had the same concern and doubted my old Garmin after my HR ran up to near 200 on a few occasions. Turns out it was AFIB. Without scientific tests, what is your Max HR? Old calculators are debunked by many. At 59 yrs old, 230+ lbs, a 165 max is probably accurate based on my experience. However, two riding buddies, 75 and 55 yrs old, both routinely ride comfortably at effort with HR in the 180’s or higher. More and more evidence points to varied physiology and healthcare providers are way behind. Anyone following here is not the typical patient a Dr sees, and it is worse over 50. They expect you to be prediabetic with hypertension. Don’t even get me started about Calcium scores for plaque.
The max HR formulas are like saying, since the average male shoe size is 8 1/2, all men wear size 8 1/2. Obviously jot true.
And although you can’t train you max HR, it’s apparent that older men who have been fit for a long time tend to exhibit less decline in their max.
Your max heart rate is a function of genetics rather than fitness level, according to many sources. You can’t “train your heart rate up.” The formulae are guidelines, not rules, that are derived from empirical data on a large sampling of people. At any given age, there will be a distribution of HRs. Mr. Dewey is way out on the tail of the distribution for 71 year-olds. Hats off to him.
PS-Friel’s article is very good. His last paragraph:
Finally, there is absolutely no reason to compare HR zones. It tells us nothing about either person as far as fitness, health, or performance is concerned. It’s like comparing shoes sizes to determine how fit people are. There is little in the way of an absolute and direct relationship between the two.