Some say that such work is detrimental to speed and can cause conversion of fast twitch muscles to slow twitch.
Clyde Hart says that new thinking prescribes as much as 40% of early season training toward aerobic foundation and he even encourages a few days a month of long distance cross country runs to 'refresh the base' ... even during the competition season.
I don't really see how this could be detrimental if the apropriate strength and speed work were not compromised.
In Bill Collins' book, he prescribes mileage foundation for September workouts. Quantity rather than quality. Some of these first early season workouts include: 3 mile runs in 24 min, 8 x 400m at 90 sec with 2 min rest, 15 x 300m with 2 min rest at ~ 70 sec., 2 x 2 mile run in 17 min with 8 min rest. Each week, similar aerobic runs are prescribed but getting faster each week. He prescribes these runs twice a week through Novemeber and one per week all the way through Dec., gradually introducing more and faster speed work. He also suggests 2 consecutive days off every week, 3 running workouts and 2 weight workouts ... a lot less ambitious than Clyde Hart's grids that include 5 days of running and 3 days of weights on the same days as running.
Hart says it's better to undertrain than overtrain. Somewhere in between Collins and Hart, there probably lies a happy medium. Collins, however is specifically conceived for masters sprinters, where Hart is for collegiate athletes.
Since I adopted the routine of early morning training, I think I could carry that through the fall and do weights/resistance in the evening. I seem to be able to get enough of a variety of upper and lower body resistance at home from the convertible pullup bar, resistance bands and dumb bells. I probably won't need to go to the gym more than once a week, more later as my weights increase and reps go down toward competition season.
What I've planned is to workout on the track early, be back at home by 9 ish, nap / rest /practice guitar and go to work at 2pm, work until 6 or 8pm.