I took 37 from about 15 miles north of Martinsville to Bloomington the past 2 Saturdays and had no problem either time. With a 4 o'clock start again this week I would guess that traffic will be spread out throughout the day and that local traffic will be light. If this is the case, you might add a little extra time as 37 south from Martinsville to B'town is mostly one lane and 50 mph or so. Still, I don't think you will encounter enough traffic to seek an alternate route if this is your usual path.
Early starts when everyone is heading in at the same time, or OSU when the visiting team traffic is likely to all be on 37 might become a different story but I would think this week should be fine.