Does resting heart rate predict aerobic capacity

I’m just wondering about what the research says about this. I have a very low resting heart rate, but I have not spent a lot of time training specifically for endurance. I do some stair climbing sometimes with a heavy pack for about 3-4 hours a week on average. Recently also technical climbing.

Otherwise I’ve been doing a lot of strength training for years, mostly low rep high weight but in recent years more high rep low weight.

So when I’m in the mountains I can get the job done, but it can feel pretty shitty and I’m slower than other guys I know.

So what I’m wondering is:

Either the low resting heart rate (lowest measured is 38, average is around 42, measured over the course of a few months with an HR monitor) is just genetic, and it has no bearing on my capacity.

Or the years of hard strength training did something, and I have this low HR because my capacity is pretty good, and the reason I don’t perform that well in the mountains is because I don’t know how to push hard enough.

Perfomance-wise in absolute numbers with stair climbing the best I can do now is just to climb 1000 meters in 2 hours with a 14 kg pack (taking the elevator down) and boots in zone 1. 600 meters in an hour with just sneakers in zone 2.