Your quadricep muscles, or "quads," are an important group of leg muscles that include the vastus lateralis, vastus medialis, vastus intermedius and the rectus femoris. These muscles play an integral part in straightening or extending the knee. When exercising, these muscles are especially targeted during actions like lunges, squats, leg presses and leg extensions. In some cases, you may feel muscle spasms in the quads accompanied by muscle tension or tightness after exercising. These symptoms can be caused by one or even a combination of reasons.
Overuse is one of the most common reasons why you may feel tightness in your quad muscles. Anytime you exercise a muscle group, you can create microtears, which begin the process of hypertrophy, or the building and strengthening of the muscles. However, when you over-work a particular muscle during exercise, the muscle can spasm and contract to prevent more damage. This tightening of the quadriceps limits blood flow to the muscle tissue and can result in the feeling of tightness.
Dehydration and Electrolytes
Dehydration and electrolyte imbalance may also contribute to muscle cramps, spasms and tightness, says the American College of Sports Medicine. Water is essential for proper muscle function and health. It makes up about 83 percent of your blood supply. Without adequate water, electrolytes like sodium and potassium can become unbalanced, and the flow of oxygen and other nutrients can be slowed to the quadriceps. A healthy blood flow is needed for the cells of the muscle to create energy, and without these important nutrients, the muscle may contract and tighten to conserve nutrients.
Severe injuries to the muscle, such as a grade three muscle strain, can result in swelling of the muscle tissue. Swelling occurs as the muscle damage triggers the immune system to flood the area with fluids to repair and protect the damaged area. As the quadriceps fills with fluid, the muscle may feel tight accompanied by a restriction in range of motion when trying to extend your knee.
When your body experiences emotional stress, the "fight or flight" response is activated, which stimulates the adrenal glands to produce adrenaline. Adrenaline creates certain physical reactions that are meant to protect and prepare the body in case of an emergency, including the tensing of muscles groups. Chronic stress continually triggers this effect, which can result in more long-lasting feelings of tight muscles.