Delayed Onset Muscle Soreness (DOMS)
We mentioned pain due to lack of conditioning and poor technique above, and the medical name for that is Delayed Onset Muscle Soreness (DOMS). It happens after you exercise. You start off feeling great, but by the end of your workout, you feel like you just ran a marathon. That is known as DOMS.
However, this isn’t necessarily caused by running. Actually, the most common culprit is weight training, but only when you’re not used to the weight you’re trying to lift and when it is the first time lifting weights after a long time.
This happens because the muscles you use to move the weights are being used more than usual. The muscle is not used to this type of work, and the tissue becomes very tight. You will likely notice that they hurt when you try to stretch these muscles. DOMS is not a problem that requires urgent medical help, but you might want to ask your doctor about it if the problem persists for more than five days.
References:
https://www.buoyhealth.com/learn/thigh-pain