Despite my lack of a comprehensive training program, something I'm working on thru what I'm learning here, I too have found it takes 2 – 3 days after a strenuous round of intervals. I used to use a "shotgun" approach and try to work on all aspects sprinting on one day. I'm currently injured (calf pull) and hope to do as you have done – cut back the work load. When people find out that I'm a sprinter they tend to say "wow, your old to be sprinting. My take on it is "I'm not old – I'm getting older, everyone is… You just need to learn how to adjust your training and listen to your body. Something I still working on. Good Luck – "Keep on Tracking"