Therefore, it's exceedingly important to know the limitations and capability of the muscles in order to avert sore muscles. This goes to show that there is no truth in the saying, No pain, no gain. What counts most is on how people stay fit by exercising on a regular basis at a normal range but on a fixed routine.
https://www.disabled-world.com/artman/publish/sore-muscles.shtml
The joints in a person's body may experience stiffness from an injury or a strain. Stiffness in the joints can also begin as a person ages. Tendinitis, muscle spasms and arthritis cause pain and stiffness in the joints as well.
http://www.wisegeek.org/what-causes-muscle-stiffness.htm
Why Muscles get Stiff and Sore. Because people age, they start to complain more of pains in their muscles and joints. They seem to tighten up with age, and such humdrum actions as bending over for the morning paper can cause them cringe. Such painfulness can grip so fiercely that they're sure it commences deep in their bones.
https://www.disabled-world.com/artman/publish/sore-muscles.shtml
When your child's muscles seem loose and slack, he could have what's called low muscle tone. Your child's motor skills are regressing. Motor regression (including deterioration in strength or agility that's not due to an identifiable cause such as illness) in a... Your child favors one hand or side of his body.
https://www.babycenter.com/0_your-childs-limbs-seem-stiff_12577.bc
Muscle stiffness is caused when the muscles in a certain area of the body contract and become tense. Stiff muscles can happen from a variety of situations. These situations can range from having periods of inactivity to exercising, physical labor or playing sports.
http://www.wisegeek.org/what-causes-muscle-stiffness.htm
When the body is toxic, inflamed and swollen, it is more likely that stress, minimal physical exertion, exercise, massage and even chiropractic treatments can cause more inflammation, swelling, stiffness and neck and joint pain, because the underlying causes have not been corrected.
https://www.bodyzone.com/most-neck-back-and-joint-stiffness-and-pain-are-caused-by-unhealthy-lifestyles-and-underlying-thyroid-dysfunction/
ABC News. Stiff Person Syndrome Locks Up One Woman's Body. Kristie Tunick, 32, was determined to go to her future brother-in-law's 2007 wedding, despite being ill for several years from stomach problems and an autoimmune condition that leaves her weak. In the end, Tunick went and had a terrific time. But she paid for it later when her body became achy and stiff.
http://abcnews.go.com/Health/PainManagement/story?id=7521312&page=1
I have found in my holistic practice that the number one most common cause of most body stiffness from neck, back and joint stiffness and pain, also including arm, elbow, hand, leg, knee and foot problems and also including exacerbation of chronic fibromyalgia pain, is slouching during waking hours and sleeping on the abdomen, sleeping with the arms ...
https://www.bodyzone.com/most-neck-back-and-joint-stiffness-and-pain-are-caused-by-unhealthy-lifestyles-and-underlying-thyroid-dysfunction/
Experiencing stiffness in the hip area is usually a result of arthritis or a more serious medical condition like Antley-Bixler syndrome or hypophosphatemic rickets. Antley-Bixler Syndrome and arthritis cause stiffness in the knees. An elbow with muscle stiffness can be caused by a sprain or epicondylitis.
http://www.wisegeek.org/what-causes-muscle-stiffness.htm
Your child's limbs seem stiff. What you may notice. If your child seems stiff or rigid, he may have what's described as high muscle tone (hypertonia), which means that his muscles are chronically contracted. You may notice that your child holds his hands in tight fists or that he seems unable to relax certain muscles.
https://www.babycenter.com/0_your-childs-limbs-seem-stiff_12577.bc
what makes a body stiffen
An injury or a strain makes a body stiffen. The joints in a person's body may experience stiffness from an injury or a strain.