Post training recovery and delayed muscle pain
Often when we come back into high intensity training when we have been sedentary for a while [just a few weeks], we may well make tiny tears in the muscle, this is perfectly normal and part of the strengthening process. This typically happens in people who have played sport and competed at a good level.
Any new type of training we do, the body will adapt and grow stronger. In particular high intensity explosive exercises, but the reason we do these exercises at one element is because they are exceptionally good for us. You are accessing more muscle, you are burning high calories and your body composition is becoming leaner. Sprinting is a movement you may not have done for a while, when we exert ourselves above our normal level of activity we make tiny tears in the muscle fibers, you are essentially accessing muscle that you have not used for a while or never used making the legs stiff over the next week or so. - This is nothing to worry about; it is all part of the natural process of becoming stronger.
The muscles have been healing and strengthening and then we get you out to train again, because the little tears are not fully healed the muscle around the tiny tears locks up to protect the leg. It can feel like the leg is cramping
It is deeply frustrating.
Over the next week, you should try to stretch the quad as much as possible; also you could try a foam roller. This is not to say stretching is the whole answer, the quad has to recover, so try to stick at about 80% and [i know it is difficult] don't get too frustrated by it, this is a natural process and once you are through it it will not come back.
A glass of milk pst session has been shown to be very effective in recovery.