As part of our data explainer series, we speak to Edward Theuns (Team Sunweb), Adam Hansen (Lotto Soudal) and Dr Dan Dwyer, of Deakin University, Geelong, Australia, about how to interpret a cyclist's heart rate.
Data explainer: Heart Rate
As we’ve seen in Velon’s data explainer series, power is considered the most objective performance value available to cyclists, teams and sports scientists.
On the other hand heart rate – while offering a significant clue to a rider’s performance and condition, and the amount of effort being put in – is one of the more subjective values, and can be influenced by many external factors.
Super-fit professional cyclists have very low resting heart rates, due to their high level of physical conditioning - while their maximum heart rates, when they are racing, may well go much higher than normal, untrained people.
“Heart rate is related to the circumstances, so if it’s hot, your heart rate goes up,” Trek-Segafredo’s Edward Theuns told us. "Power is more objective."
Adam Hansen of Lotto Soudal adds: “If a rider has a bad night’s sleep, or has a few extra coffees in the morning, or the temperature changes, his heart rate is totally different.
"If I’m cruising in the bunch, my heart rate could 90 or a 100, and the average guy just sitting on the couch, his heart rate could be 100 just relaxing," Hansen added. "But it can be very interesting if you compare data for two different riders."
Dr Dan Dwyer, Senior Lecturer in Applied Sport Science at Deakin University, says: "Heart rate is prone to being affected by other factors, like mental stress, anticipation, ambient temperature, immune function, and also over-training.
"Many factors can interfere with the ability to use heart rate as an indicator of effort. Fighting off a cold can affect heart rate at rest and the heart rate response to exercise."
Cyclists tend to be built in a broadly similar way, but there is still significant variation within the peloton in weight and height – which means heart rate data must be interpreted carefully, says Dr Dwyer:
"It's important to point out the other factors – for example differences in body size, and heart size. When the peloton is cruising, you could be looking at the heart rate of two different cyclists, one might be the climber of the team, and the other one could be the big heavy time trial specialist.
"The climber’s heart rate might be higher simply because he’s smaller and he’s probably got a smaller heart.
"Equally in a small breakaway group and they're working hard to try and maintain a gap from the peloton, you'd expect to see high heart rates, and if one of them seemed unusually low, that might be a clue that the rider is not working very hard, he’s not sharing the burden.
"These heart rates can be used as a clue as to both the effort the cyclist is putting in, whether they're pulling their weight, or whether they're in the red zone and if they're going to pop before they finish a climb."
So it’s important to remember that differences in body size and heart size will naturally affect heart rate. A heavier rider like John Degenkolb (Trek-Segafredo) is going to be different to a lighter climber like Nairo Quintana (Movistar Team).
But heart rate will always give an indication of how hard a rider is working, especially on a climb or in a breakaway, and forms an important part of the data Velon offers live to cycling fans around the world.