During lockdown I set up some basic equipment in my garage, and like you say, there was a lot of precum.
I find being naked helps for two reasons. It focuses your mind on the workout, especially if you have a mirror and can see your muscles as you lift. There is something very inspirational and auto erotic about watching your body respond to exercise.
But it also gives your body some freedom to respond sexually. You begin to feel the connection form between your breathing, musculature and sexual core.
When I'm up gripping the bar suspended in the rafters of my garage, I try to visualise it like a wave of energy gradually moving from my arms, through biceps, pectorals and abdominals to the pelvic muscles. Once that energy hits my genitals then the feelings are euphoric. If I had the strength and stamina of a gymnast then I reckon i could exercise myself to a mind-blowing orgasm every time. Alas, the reality of age, muscle fatigue and pain sometimes gets in the way of this, and I have to settle for lots of precum instead!