- Power shows what you are doing. Heart rate shows how your body is responding.
- Heart rate lags behind effort and moves with heat, sleep and stress, so it is a poor guide for short intervals.
- It is most useful over time: the same power at a lower heart rate, or a higher one on a tired day.
Two different signals
Power is immediate. The watts on the screen are an average of the last three seconds, so they respond quickly but not instantly. Heart rate is your body’s answer to that effort, and it answers slowly.
Why it lags
Start an interval and your heart rate takes a minute or two to catch up. By the time it settles, a three-minute effort is almost over. That is why Hammy’s targets are all power, and heart rate is something to watch alongside them.
Drift
During a long steady effort, heart rate often creeps up even though the power stays flat. Warmth is a common reason. A fan and plenty of water help.
What it is good for
- On easy rides, it is a quick check that easy really is easy.
- Over weeks, the same workout at a lower heart rate than a month ago is a sign of progress.
- On off days, a heart rate that is high for the same power can mean you are tired, warm or short on sleep.
- After hard intervals, you can see how quickly it falls.
It is less useful for pacing short efforts, and for comparing yourself with other riders. Heart rates differ a lot between people.
Stop and get help if you have chest pain, dizziness, fainting or breathlessness that feels out of proportion to the effort. Heart rate is a training guide, not a medical test. If you have a heart condition, talk to a doctor before hard training.
Getting a good signal
A chest strap is usually more accurate than a wrist sensor, especially in hard intervals. Moisten the contacts, wear it snug, and keep your phone close so Bluetooth stays connected.
Pair a Bluetooth heart rate strap and Hammy shows your heart rate on the ride screen and saves it with the ride. In the ride details you can see heart rate next to power and target. The strap is never required to start a ride.
Show sources (4)Hide sources
- Coyle EF, González-Alonso J (2001). Cardiovascular Drift During Prolonged Exercise: New Perspectives. Exercise and Sport Sciences Reviews, 29(2), 88–92. doi:10.1097/00003677-200104000-00009
- Gillinov S, Etiwy M, Wang R, et al. (2017). Variable Accuracy of Wearable Heart Rate Monitors during Aerobic Exercise. Medicine & Science in Sports & Exercise, 49(8), 1697–1703. doi:10.1249/mss.0000000000001284
- Hunt KJ, Grunder R, Zahnd A (2019). Identification and comparison of heart-rate dynamics during cycle ergometer and treadmill exercise. PLOS ONE, 14(8), e0220826. doi:10.1371/journal.pone.0220826
- Sawka MN, Burke LM, Eichner ER, et al. (2007). American College of Sports Medicine position stand. Exercise and fluid replacement. Medicine & Science in Sports & Exercise, 39(2), 377–390. doi:10.1249/mss.0b013e31802ca597
