Four gigging fitness aspects seem to affect me. All mentioned in the thread by others: 1. The physical bass playing, I wonder how many notes I play in a night, until recently I rehearsed for about 8 hours weekly, hand strength, back strength no problem. 2. Concentration, I now find being 'on it' for 3 - 4 hours increasingly hard, pa problem solving then instant switch to musical stuff, blunders happen due to concentration fails. 3. Moving kit, even with lightweight kit (and the pa is not) it is all too easy to damage yourself - rotator cuff injury anyone. 4. Driving 2 hours to a gig in the daylight can be very pleasant on a sunny day. Driving back in the dark after doing the business is no longer fun. The result is that I am usually shattered the day after, at nearly 67 age is catching up despite pretty good fitness. Hence, my decision to scale back my musical efforts - I do not need 30 gigs per year.