Just thought I would give my 2c on the topic, as this is always a contentious and “hot” topic in PE (see what I did there). I warmed up a handful of times when I started and didn’t really feel like it helped or benefited me all that much. I have never warmed up since I started PE. If it is cold out or my unit has shrivelled up and turtled, I will do a few helicopter shakes and some light stretches before going into the main PE work. To be honest, the main reason I did not bother with warm-ups, as well as feeling they were not of much help, is because they were very time-consuming. Throw in warm-up and warm-downs/cool-downs (I think both are daft), and you got an extra 30 minutes onto your routine that involves you sitting there with a heating pad or rice sock on your cock. I have gained quite well in the year and half I have been doing PE, never any serious injuries or issues, but I understand that many others love heat. As I said earlier, it really all depends on preference. I definitely would not say that they are mandatory though.