Lifting weights generally has variety in motion and muscle group. Writing is doing the same, short lift - without using the full range of motion - for the same

Lifting weights generally has variety in motion and muscle group. Writing is doing the same, short lift - without using the full range of motion - for the same muscle group day after day after day. It isn't a short-term issue: Comic artists often work long days (contract work) and work until their arm doesn't function well anymore (often decades before retirement age). Writing (and drawing) can produce a number of repetitive strain injuries (hand, wrist, elbow and shoulder). You can increase your tolerance if you are healthy, but it still is going to lead to injuries over time and you are better off taking more breaks than you think you need and learning not to press as hard as people are prone to do. You do "improve", but the improvement isn't really in strength but fine motor control and motion and things like that (especially with drawing).