How would that test do at predicting achievement in archery? How about curling? Are those not "real" sports, or is athleticism a squishy human concept rather than an objectively measurable value?
There are plenty of metrics you can use to quantify someones atheletic capability, not least of which is your bodies ability to hold and transport oxygen.
() I don't know the technical term, but the point stands.
As noted in the study, the largest influence they tested for archery performance was height. I'd bet a large sum of money that height is also a strong positive influence on many sports (eg basketball), similar to how G is an influence on many cognitive 'sports' like occupations. We can easily measure height and most would have no trouble believing that (largely genetic) factor greatly influences athletic performance. Why is IQ so different?
Even if the test doesn't predict performance in every single sport, that doesn't mean it has zero predictive power in all sports.
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Similarly, I'm not saying IQ is destiny or even the largest factor in any given endeavour, its not. But its equally wrong to say its not a factor at all. It is somewhere in the middle.
Like most metrics, it doesn't capture the entirety of the squishy concept as you say, but it does capture something about it.
I think we understand this in many other areas. Look at PE ratio or revenue growth for a stock, look at goals on target for a football striker, VO2max or running economy for a runner, mileage for a car. IQ is understandably more controversial but the concept is the same.
https://aassjournal.com/browse.php?a_id=897&slc_lang=en&sid=...
I didn't see any specific research related to curling, but it is definitely a fairly high peak intensity activity that demands a high level of fitness:
https://curlnoca.ca/wp-content/uploads/2013/06/Curling-Heart...