You might try voluntary rapid deep breathing to simulate heavy excercise. It's a very strange sensation and I wouldn't recommend doing it too often (maybe even check with a doctor first). Generally, after about 5-10 minutes, I feel very similar to the way I feel when working out, except without the sweat, elevated heart rate, and muscle strain.

It's not exactly practical to swim 20 laps then sit down and do some design or development, even if you could bring your laptop to the pool.

But yeah, metacognition techniques are basically metaprogramming for your brain.