I read a very good article on muscle regulation problems in ADHD, but alas it doesn't exist it English. (Though the research it's based on does.) It's about how 80% of people with ADHD have difficulty regulating muscle tension.
If you have ADHD, these motor function issues may be linked to it (and may be helped by medication):
Muscle pain! Just in general! Super common!
Being unable to sit upright/straight-backed for long periods of time. (Over-tension in chest and back leads to exhaustion.) Poor posture is a symptom of ADHD and not your fault!
Getting out of breath quickly, despite being in decent shape. (Again, muscle tension in chest and back.)
Problems with handwriting and fine motor function. (Shoulder tension limits mobility.) Tension in hands/elbows means it's hard to control how hard you write, especially over time.
Co-movement in hands and feet. When you write or draw, you might move your feet along too -- this why it's more comfortable to sit on your feet while doing this!!
General clumsiness, being able to fine control muscles leads to bumping into things. It's hard to control both the force and the flow of movement.
Physical exhaustion and tiredness. Cause. You're tensing.
All this does not necessarily prevent ADHDers from being accomplished athletes, though they found these same problems in ADHD athletes. Nor does ADHD mean general motor function problems, so it may not necessarily be detected in motor function tests. And even if you know how to do stuff and can do it, these problems usually show up with repeated movements.
As you grow older, your body learns to compensate better - however there's also higher instance of muscle pain and exhaustion.
All these things are improved by stimulant ADHD medication. It is also very beneficial to do muscle stretches, esp for your back.
SOURCES: This is mostly a translation/summary from an article at ADHD Norway, by author Liv Larsen Stray.
If you want to look at one of the most recent research articles on it, head to sci-hub and put in the DOI: 10.4172/2165-7025.1000255
