First, I'm not a competitive athlete, nor am I of an age that I might be. I was a jogger, however.
I've taken both Rythmol and Metoprolol, but at much higher dose levels. I'm now off of Rythmol as it didn't do anything to reduce AFib.
I know Toprol does lower the HR, one of its prime purposes when subscribed, the other to lower blood pressure. Clearly, you didn't need anything to lower your HR.