That study was looking at an elderly female population, and essentially using leg strength as a proxy for overall fitness level. The authors never used that da

That study was looking at an elderly female population, and essentially using leg strength as a proxy for overall fitness level. The authors never used that data to argue that there was something particular about leg strength that correlated with intelligence. Rather, they were making the point that overall fitness and activity levels correlate with healthy aging. This was a classic misrepresentation in science media.