all the running is taking away your muscle, 4-5 miles is a lot every day. that is almost cross-country milage you are running. are slow/short days were in teh 4-6 miles a day. if you want to add muscle mass run only 1-3 miles every other day. and so some strength training instead of just distance. run stairs (run them) or hills ( sprint up jog down), do indian runs (i.e. on a track sprint 200m then jog 200m then sprint 200m and then jog 200m repeat that for a mile and rest then redo) , sprints, etc.
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