Eli5 the relationship between heart rate and fitness level/stamina


I (38f) was hiking with my partner (49m). I was feeling fine and would have liked to go faster but he was huffing and puffing and needed lots of breaks. His heart rate was around 130, while mine was up around 160. I have always heard that having a slower heart rate is a sign of better cardio fitness, but I work out more and have much better stamina during exercise than he does. What’s that about?

(Edited because I forgot how old I am)

In: 5

It’s hard to say without more details, but if he was huffing and puffing he might have been limited by his lungs directly rather than his overall cardiovascular fitness.

Also, he’s 10 years older than you, and the older you get the lower your exercising heart rate gets. It’s not a 30 point difference for 10 years, but it’s likely a contributor.

Lower heart rate for the same amount of work (amount of force required to move a certain distance) means your cardiovascular system is good/efficient. You are transporting oxygen to your muscles with a combination of breathing and heart rate. Him beign winded probably had more to do with a male is heavier and has more mass to move, which requires more force, which requires more oxygen to feed the muscles to do so. If you wore a weighted vest that made you as heavy as he was, you would probably be breathing heavily as well, and you might even have a higher heart rate than what you had. Youd need more oxygen to feed your muscles to push the extra mass.

The relationship between heart rate and fitness is complicated to say the least.. at the end of the day your heart rate determines how fast oxygen is going around your body and generally has no major indication on what your exact physical health is.

In general however the medical community values a lower resting heart rate as it suggests your heart is a stronger muscle, and as such is capable of pumping more blood in less beats. Your exercise heart rate on the other hand doesn’t mean much at all, instead your fatigue (and how fast you fatigue) indicates your level of fitness overall. As such if you want to see how medically fit you are against each other, the resting heart rate can be a better indicator.

On the other hand you not fatiguing is also a sign of better fitness. Individuals who are fitter use less oxygen to do the same task, they will also use the same amount of oxygen to do a task faster/stronger. This is why weight lifters can lift extreme weights, and runners can run extreme distances – they are more efficient.

Your body can become good at something in different ways, it’s only when your body is challenged however can it improve at something. In your situation you are capable of doing more, if you pushed yourself too your limit you would fatigue (like him) and your body will either:
– work your heart harder by pumping faster.
– or pump harder as the muscle builds.
– become more efficient with what it’s got.
If you over push your heart, it can break, this is why we have to fatigue – it’s also why we never tell someone to push themselves to extreme levels.

At higher levels of fitness your battle is to avoid fatigue for as long as you possibly can, how your body achieves this is it’s own choice. If you can do more then someone, you are likely fitter then them in that area.

My word of warning however is:
If I use myself as an example, I am a 100kg male. You ask me to run? I’m terrible at it, im not use to running. You ask me to spin on a spin bike? I love it, I can go for an exceptionally long time at an exceptionally high gear.

Fitness is a broad spectrum, in areas you struggle someone will succeed and vice versa. It’s not about who is “more fit”, it’s about being able to do the things you love together. I would maybe suggest to him you go on more walks, build his stamina, that way you can go longer and he will feel more comfortable.

Has your partner had a cardiac stress test?