Muscle tighness from inactivity can be caused by a number of factors.
Muscle tension refers to two very different conditions. In one instance, muscle tension correlates with muscle tone, which is healthy, passive muscle tension and its related firmness and definition. However, when linked to lack of exercise, muscle tension refers to muscle stiffness and tightness. This form of tension is manifested in skeletal muscles, and can be alleviated with various techniques.
Skeletal muscles are the more than 600 muscles that are attached to your bones via connective tissues called tendons. Movement occurs because as a muscle contracts, the tendon pulls the bone with the motion of the muscle. Joints also turn with the motion, creating further movement. As the American Council on Exercise reports, restricted movement due to prolonged inactivity causes muscles to become tight.
Muscle tension from inactivity can result from muscle imbalances. Muscle imbalances commonly occur when you are in seated positions -- such as at a desk -- for extended periods. When seated, some of your muscles are bent or flexed, placing them in a shortened position, while others are in a lengthened position. According to ACE, the muscle imbalance causes the lengthened muscle -- such as your back muscle -- to become weak, and the shortened muscle -- such as your leg or hip muscle -- to become tense.
Additionally, as Millar Sports Chiropractic points out, exercise supplies oxygen to the muscles. When you don't exercise, your muscles experience lower oxygen levels, causing lactic acid to build up in your muscles. This type of lactic acid accumulation forms knotted points in your muscles, which can lead to muscle tension. MSC further reports that when muscles are not stretched with exercise, they become shortened and also develop knotted points.
ACE advises that muscle tension caused by muscle imbalances can be alleviated by maintaining proper posture, strengthening the weak, lengthened muscles and by stretching the tense, shortened muscles. MSC recommends cardiovascular, stretching and strengthening exercises to treat and prevent knotted points. According to MSC, cardiovascular exercise is by far the most important because it supplies the oxygen your muscles need to break down the lactic acid. There's a wide array of cardiovascular exercises to choose from, including walking, cycling, skating and stair stepping. MSC recommends at least 10 minutes of cardio exercises that stimulates 70 to 80 percent of your maximum heart rate, three times per week.