Have you ever felt like your post-workout soreness was worse two days after your workout? You know the soreness I'm talking about - when it's hard to sit on the toilet or you feel every muscle in your abs when you laugh. If you are experiencing more intense soreness on day two following a workout, you are likely experiencing Delayed Onset of Muscle Soreness (DOMS).
The medical and fitness community used to attribute that soreness to lactic acid buildup, but that's no longer the belief. DOMS is an inflammation of your muscles due to the tough workout you just completed.
Eccentric movements, which elongate your muscle, are believed to be contributors to DOMS. When you are strength training, a concentric movement is when you shorten the muscle (curling the weight toward your bicep). An eccentric movement is when you lengthen the muscle - the downward curl of a bicep curl or the elongation of your quadriceps muscles as you walk down a hill. When you strength train, you cause micro-tears in your muscle fibers, which your body repairs in order to build muscles. Eccentric training is believed to cause more micro-tears, which would explain additional soreness.
The good news is that your muscles are getting stronger! Also, you are less likely to be that sore the next time you do that workout. Your body is adapting and getting stronger every workout. Depending on the extent of your sore muscles, a light workout can help lessen your soreness. If touching the muscle doesn't make it sore and you have a full range of motion, consider doing some light cardio.
However, if your soreness persists for longer than a few days (or feels way more severe than just workout soreness), go see a medical professional.