I’m not suggesting this is a problem. It may even be on benefit? More just curious on the science, than concerned.
I’ve been wearing a heart rate monitor during training for quite some time. My heart rate has always been low during this time. Being a long time competitor of conditioning and endurance sports, it has always taken higher intensity cardio to elevate my heart rate a good amount.
With that said, previously my heart rate would stay below 50% of my max during weight lifting sessions. Lifting 6-10 rep maxes for exercises too. During heavy leg exercises, it may briefly elevate to 60-70%, but drop back down quickly. My muscles would be fatigued, but my heart rate remained low.
For this reason, I always sort of felt I wasn’t burning as much calories as most when weight lifting. Lately, my heart rate has been more elevated during my lifting sessions. More in the 60-75% range, while I generally feel the same, or maybe a bit better, feeling more “amped up” and energized throughout the session.
I’m not concerned by this. I’m wondering what might explain this? The increase in IGF-1? Increase in Free T? Increase in free t3? Or otherwise?