I'm 60+, spent most of my time outdoors (a few million+ SLOC of exploration geophysics sensing | analysis | GIS code written in field ) and have yet to meet a bodybuilder that can put in an 8 hour shift on a long handle shovel day in day out.

Wirey station hands can, skinny and|or fat farmers can, I still can and my father (still alive, born 1935) still can.

Sustained steady physical work is a thing that seems largely orthoganal to gym fit.