A couple easy days and slight hamstring strain

Sunday was a complete rest day. Yesterday was just a easy 6 mile recovery run. Today I did a 20 minute warmup and 5x100m @ 15,14,13.5, 12.5,12.7. On my last interval I went for full effort and felt a slight strain in my right hamstring. If I kept up the pace I think I would have ran sub 11.5 if I had not let up the last 50 meters. The weather was unusually cool for this time of year. I think my muscles tightened up in the cold weather and caused my hamstring strain. I also had some very hard workouts last week. I was thinking about doing an 800m time trial tomorrow but I am now having second thoughts. I will see how I feel tomorrow.