VO2 max changing significantly without running or cycling

I haven't done a run for a month, but my VO2 max has changed 2 points yesterday. All I did yesterday was a strength exercise so it shouldn't qualify for anything like that. 

I updated my weight today, which is all I can assume changed it, but why would it say yesterday, and especially when I haven't done a run in so long? Is this normal when doing a weight change?