We all know that postural muscles get tired and that creates knots. But muscles also get tired after exercises, this is called DOMS - delayed onset muscle soreness.
DOMS is characterised by a dull, aching pain in the affected muscle, often combined with tenderness and stiffness. The pain is typically felt only when the muscle is stretched, contracted or put under pressure, but otherwise the muscle feels fine. The soreness usually increases in intensity in the first 24 hours after exercise. It peaks from 24 to 72 hours, then subsides and disappears up to seven days after exercise.
DOMS can be the reason why sporty people feel aches and pains when they are treated if they have recently been pushing themselves when exercising.
Unfortunately stretching or warming up the muscles does not prevent DOMS but gradually increasing the intensity of the exercise does.
If treatment is desired, any measure that increases blood flow to the muscle, such as hot baths, sauna or a massage may help.