Heating the tissues temporarily reduces stiffness, making for a more cooperative unit. My preference is an IR pad. I use the pad with a light contrictor at the base which reduces blood (enhanced bloodflow takes away heat from the area). This allows for the heating to occur quicker.
Over time I’ve learned the exact feeling when I reach the right temperature, which is a very deep below the skin. With my particular pad and the above method this takes around 30 minutes and does not burn the skin. With a regular (conduction) type heat pad ro rice sock, care must be taken to heat the tissues without scorching the skin or anything else. It should never be uncomfortable.
A few days ago I tried the IR pad heating whilst clamping. This got tissues up to heat within a couple of minutes, but as noted in another thread, oxygen burned up pretty quickly in my unit making it go more purple very quickly, so care must be taken if using this route (by that I mean it’s not a ‘passive’ heating method).
As for how often to apply the heat; All the time would be optimal. For practical reasonsthis is often achievable though, so maybe every 10 minutes or between sets while your arms recover might be a reasonable protocol.