Agreed, but you are talking of sprints it seems. Check out sprinters versus marathon runners. For you Falcon with good leg genetics sprinting may work for a average guy without the genetis it may increase his thighs for awhile but he will need resistance to go further with size. Myself included I can take up a sprint regimen and it will take me only to a certain point I dont have great leg genetics. So in summary most need more than sprints to develop the legs to potential.
sprints is completely ALL OUT running, and you will be spent afte a few and REQUIRE calories after only a few sprints to keep going
the key is getting in the calories without getting that full feeling, thats why i reccomend denser foods for this purpose
running is still a sprint at about half the strength but double the length would make it equivelant to a sprint, with running or sprinting you hit that phsycial barrier after 30 seconds on a sprint and 1-2 min on a run
i think most have the incorrect idea about cardio as in they picture weak people doing slow ass jogging with 12 inch strides
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now that wont do sheit