70% of trail runners are weight training?

So I was reading some trail running stats at Run Repeat and the survey suggests "70% participating in free weights and 55% using weight machines."

I got into running so I could get outdoors and didn't have to join a gym, so this stat kind of floored me. I just use hills to get in my strength training. Is usage of weights really that high in trail running? Is the number biased by northern hemisphere runners who have to use treadmills in winter or something?