Medications can be a big factor in heart rate regardless of other fitness parameters, including aerobic conditioning, strength, etc.
If I take sudafed for sinus congestion (pseudo-ephedrine, not the phenylephrine substitute), my heart rate will often increase 10 bpm or more. That might offer a minor benefit in some sports, although there are increased risks of heart stress and other problems.
Occasionally I take blood pressure meds for severe headaches -- for some reason, beta blockers and calcium channel blockers sometimes help with migraines. Metoprolol and lisinopril will decrease my resting HR about 10 bpm, and my exertion HR 20-30 bpm. So on a familiar route at my usual speed and level of exertion where my average HR would be around 140 and peaks around 160 bpm, instead the average will be around 120 and I'll have a hard time getting my peak HR above 140 bpm even when my legs are cooked and I'm about gassed out. It feels like I'm not getting enough oxygenated blood circulating. Efforts that would be moderate on most days feel like high intensity on days when I take BP meds.
And I tend to feel sluggish and sleepy on BP meds, although I don't take them every day and don't know whether I'd eventually adapt. I've resisted doctors' suggestions to take BP and cholesterol meds as preventive measures, and prefer to watch my diet, get plenty of exercise, etc.