I guess you missed the part about physical labor in my comment.

You're looking for an answer via a really poor proxy. Lifting weight is lifting weight. Gyms are more popular because of the lack of sensible alternatives for a comprehensive workout. Any data you find about them will also be biased towards the recent decades of office work and working from home. Is there any way to tell if gyms are even picking up the slack? My guess would be overall exercise is down, even for those who go to the gym regularly.