I’ve noticed that my heart rate goes up towards the end of a race, even though I’m running at the same pace throughout the entire race – why is that?
E.g. I had a run at a pace of 5:50 min/km, and at the end of the run I had to run at 7:00 min/km to keep the same heart rate.
In: Biology
I think it’s called aerobic decoupling and it can be from a number of things but usually it can be attributed to pushing outside your training. I notice it a lot in the early season until my fitness comes back. Zone 2 power creeps into zone 3 heart rate.
Your body becomes less efficient as it fatigues so your heart has to work harder to maintain the same effort.
Ooooooo my wheelhouse (Kinesiology grad here)
Essentially it has to do with two things – duration and intensity.
The longer you run, the more you are burning through your energy stores (I can get into the shift from glucose > fat for ATP production for energy, but I wont) – so the LONGER you run at the same pace, the more your energy stores deplete, and the more your burning to produce the same output (muscular contraction)
How intesne the run is – this depends on a lot of things – if you’re running on a track, it’s flat, there’s no undulations or hills, and then it all depends on how HARD or FAST you’re running – same principle applies – the harder you run, the more energy you’re burning quickly, and your heart needs to keep up to push blood throughout your body – not only for O2, but for nutrients that feed the muscles to cause contraction.
So – anytime you hit an uphill and have to push harder to keep pace, your heart is going to work harder, and there is a refractory period once you get back on flat ground to get back to steady state.
Thanks for letting me nerd out for a second.
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