do thyroid hormones influence heart rate from influencing the heart itself or from the nerves attached to it?

An excess of thyroid hormones increases cardiac contractility and resting heart rate (see box below). Cardiac output may increase by 50-300 per cent as a result of the combined effect of increases in resting heart rate, contractility, ejection fraction and blood volume, with a concomitant decrease in SVR

answer increasing the intensity, duration,and frequency of exercise progressively;