Deconditioning from inactivity can create a similar clinical picture as your PCP suggests. However, consider seeing a neurologist to make sure nothing else is going on. You have some conflicting symptoms-?sharp pains vs. muscle spasms - 2 different things that point to different diseases. Could be a peripheral neuropathy which is a problem with your nerves or a myopathy, which is a problem with the muscles. Also, the stiff neck and tingling may be indicative of a problem with the cervical spine. Talk to your doc about getting a referral to a neurologist for a formal examination just to make sure that nothing else is going on. Some routine blood tests may also be helpful such as thyroid and muscle enzymes CK, aldolase as well as routine laboratory screening. It's important to make sure that nothing correctable is missed before chalking it all up to disuse. Good luck.