I have always wondered about this, but never bothered to ask anyone, so here goes. I have incorporated squats into my program since day 1. I love them, and they will always be part of my lifting program. I do legs every 5 days mixing things up with hacks, presses, squats, and a few lunges here and there. The day after leg day I am usually a bit sore, but not too sore. A good feeling kind of sore. I can usually tell if I had a good leg day by the levels of DOMS. I decided the other day to start incorporating some sprints into my program to see if it would have any effect on my leg development.
So I took a trip to the park and began doing 100m sprints all out with about 3 min rest in between. If you have never done all out sprints, my god they are taxing on the legs. I did about 5 of these before I threw in the towel. The next day, being yesterday, My legs were so sore I could barely get out of bed. It’s not much better today either. Just friggin sore like I have never been. I do realize that it was the first time I have done sprints in a long time and the next round won’t be so bad as the first.
My question is: What type of fibers are used during sprints that are not used during squats or other types of leg movements? I may be wrong here, but I thought they both used fast twitch explosive type fibers. I have done high rep explosive squats and low rep explosive squats. The same with leg presses or any other leg exercise. My legs are sore from sprints in the stretch position more than in the contracted position like they would be from doing squats. They are both explosive and use the same types of fibers, so why would I be so damn sore from sprints. Do other fibers come out of the wood work when doing sprints that don’t during squats or other leg movements that would cause this much DOMS? Even though I don’t even want to think about sprints right now, They are going to be part of my program now. I just need to figure out where to fit them in without missing out on squats on leg day.