What is a muscle strain?
A muscle strain can be a micro or macro tear in the muscle, where the muscle and tendon meet, or where the tendon attaches to the bone. There are 3 degrees of muscle strains. A first degree strain is a micro tear that is inflamed and painful when the muscle is contracted or stretched. A second degree strain is a larger tear that is also painful when the muscle is contracted or stretched but presents with swelling, bruising, and muscle spasm. Lastly a third degree strain is a complete tear of the muscle with severe pain, bruising, and loss of function and strength. With third degree strains you can feel a defect in the muscle just by touching it.
Strains commonly occur when there is a forceful stretching or contraction of the muscle, or when the muscle is overloaded in an eccentric contraction. This type of contraction occurs when the muscle is stretched to end range while opposing a force. For example, an eccentric contraction of the biceps occurs when you start with the elbows bent with a weight in your hand and slowly lower the weight as you bring your hand away from your shoulder. This places a greater load on the muscles than a concentric contraction, which works in the opposite direction as you raise the weight back up to your shoulder. This contraction is a greater challenge to the muscle because the muscle fibers are separating as they are stretched while also contracting to control the movement.
How do the hamstrings get injured?
Hamstring strains are a common condition occurring in athletes. There are 3 muscles that run down the back of the thigh that make up the hamstrings: semitendinosus, semimembranosus, and biceps femoris. These muscles start at the bottom of the pelvis and cross the knee joint. Semitendinosus and semimembranosus attach on the inner side of the knee while the biceps femoris attaches on the outside of the knee. These muscles work at both the hip and knee joints, extending the hip backward and flexing the knee, bringing the foot up towards the butt.
One of the most common ways hamstring strains occur is sprinting. During sprinting, we shift our weight from one leg to the other. As one leg pushes off the ground the other lands in order to support our body weight. The supporting leg moves backward as we propel our bodies forward. The hamstrings eccentrically contract while that supporting leg is extended back and the toes are used to push off and move forward. The hamstrings are stretched as the knee is straightened and they are loaded by both body weight and the force required at push off to move the body forward.
There are a few factors that may predispose you to a hamstring injury. Decreased flexibility of the hamstrings means that there is increased tension in the muscle, commonly described as muscle tightness. With increased tension there is a higher risk of injury as the muscle is not able to move through its full range of motion and function properly.
A muscle imbalance is also another source of injury. Human movement requires a proper balance of muscle length and strength throughout the body to allow joints to function efficiently. A muscle imbalance occurs when one muscle group is stronger than a surrounding muscle group. For example, hamstring strains often occur when the quadriceps muscles of the front of the thigh are stronger than the hamstrings on the back of the thigh. The quads tend to be more powerful during high speed activities such as sprinting and the hamstrings tend to fatigue faster. Fatigue reduces the muscles’ ability to absorb energy during movement, which can lead to a strain.
Poor conditioning can be another contributing factor of hamstring strains. Weak muscles are not accustomed to the stress of exercise and are therefore less able to cope with that stress, leaving them more likely to be injured. Another possible cause of injury is improper warm up. Muscles are like rubber bands and for individuals who sit at a desk all day, those rubber bands are not being used. They become extra tight and constricted when you are not active. If you jump right into explosive exercise, like sprints, those unstretched rubber bands get pulled apart very quickly and can snap.
In the early stages of a hamstring strain it is important to rest, especially avoiding exercises that aggravate pain, such as sprinting. Ice is also an important part of treatment and is an excellent way to fight the inflammation that can occur at the hamstrings. It should be used for 15-20 minutes at a time and can aid in pain relief. Heat may also help to relieve symptoms by encouraging blood flow to the hamstrings for more rapid healing. Heat helps to ease the tension that builds up in injured muscles which can restrict normal blood flow.
Manual therapy is another way to promote blood flow and ultimately muscle healing. Myofascial release (MFR) is a soft tissue technique designed to relieve the tissue tension and trigger points that can form in the injured muscles. Trigger points are small knots that develop in a muscle after injury. These areas are highly irritable and sensitive to pain when pressure is applied and can often send referred pain to other areas.
Once an individual’s pain is more manageable stretching and strengthening exercises can be incorporated. Stretching of the hamstrings will decrease the tissue tension built up in those muscles and allow for a more functional range of motion. Strengthening is also key in order to adjust the muscle imbalances of the leg. Eccentric activities should be progressed as pain decreases to challenge the muscles further and prevent future injury. Along with these exercises, agility training should slowly be incorporated to prepare the individual to return to their sport or activity.
If you think you may have a hamstring strain, contact Total Performance Physical Therapy to schedule an appointment.