here's the deal. there is some minimum level of fitness in order to compete near your talents. like a soccer player who needs to get in shape to run 90 minutes in a game and not need to be subbed. that is not "hard work." that is being fit enough to actually play at a reasonable fascimile of your talent level. otherwise your legs will be heavy to execute skills, you will make tired mental mistakes, and you will double over breathing heavy and ask for a sub. and in competitive soccer i may have sub rules, finite subs per half, or need to factor your fitness into selection.
this is baseline. this is not you work harder than the next guy. this is you show up in reasonable fitness you can do your job.
you're acting like the whole amount some runner does is "hard work." no. there is some amount, perhaps 20-25 miles a week, where a talented runner could turn that into sufficient fitness to approximate their talents and compete successfully and quickly.
if you do less than that, you will struggle to complete the distance correctly. everyone serious runs that practice mileage. you are not working hard doing minimum mileage.
thus the "hard work" arguments need to account for the first 20-25 miles being basic fitness to compete.
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also, as some have suggested, there are curves. you take a stud off the couch, he will be faster out of shape than a less talented sort. he might run 440 or so out of shape. other dude might be over 5. someone from the school PE might run a mile in 10. some old fart might not even finish a mile or run it in like 15-20.
if they do the baseline work, stud is down to 415-420, squadie is under 5, etc.
if they really work hard, stud gets down to 410, squadie chases 430, etc.
so each is moving along their varied talent arc. the squadie would have to be incredibly fit to match the stud lazy off the couch.
talent dominates and sets the curves. you might as well tell the squadie to work harder to try and keep anywhere near them.
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this then speaks to my HS or college distance point. XC gives jobs to more people beyond the mere talented. if it was sprints, 5 or so guys would be it. the fastest guys in the school. hard work ain't fixing that. you're slower, you're not making varsity. period.
XC employs 7 guys HS and dozens college. so i can grab the speedy natural miler types, but there is also some room for workhorses. you might have 20-30 people rostered. you can have a 420-430 type on a roster with kids who run 4 flat.
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that, and at a point, the sheer quality of competition, everyone needs an edge, and so you're trying to find anything left on your growth curve. maybe a few more miles does it. or maybe you've squeezed out the orange.
which, to me, it's mostly talent.