Running Injuries
Running injuries (or running-related injuries, RRI) affect about half of runners annually. The frequencies of various RRI depend on the type of running, such as speed and mileage. Some injuries are acute, caused by sudden overstress, such as side stitch, strains, and sprains. Many of the common injuries that affect runners are chronic, developing over longer periods as the result of overuse. Common overuse injuries include shin splints, stress fractures, Achilles tendinitis, Iliotibial band syndrome, Patellofemoral pain (runner's knee), and plantar fasciitis.
Proper running form is important in injury prevention. A major aspect of running form is foot strike pattern. The way in which the foot makes contact with the ground determines how the force of the impact is distributed throughout the body. Different types of modern running shoes are created to adjust the foot strike pattern in an effort to reduce the risk of injury. In recent years, barefoot running has increased in popularity in many Western countries, because of claims that it reduces the risk of injury. However, this has not been proven and is still debated.
Acute injuries
Side stitch
A side stitch is an intense stabbing abdominal pain under the lower edge of the ribcage that occurs during exercise. It is also called a side ache, side cramp, muscle stitch, or simply a stitch, and the medical term is Exercise-related Transient Abdominal Pain (ETAP). It sometimes extends to shoulder tip pain, and commonly occurs during running, swimming, and horseback riding. Approximately two-thirds of runners will experience at least one episode of a stitch each year. The precise cause is unclear, although it most likely involves irritation of the abdominal lining, and the condition is more likely after consuming a meal or a sugary beverage. If the pain is present only when exercising and is completely absent at rest, in an otherwise healthy person, it does not require investigation. Typical treatment strategies involve deep breathing and/or manual pressure on the affected area.
Strains
A strain is an injury that occurs to a muscle, tendon, or both. Generally, the muscle or tendon overstretches and partially tears, under more physical stress than it can withstand, often from a sudden increase in duration, intensity, or frequency of an activity. Strains most commonly occur in the foot, leg, or back. Immediate treatment typically includes five steps abbreviated as PRICE: protection, rest, ice, compression, elevation.
Sprains
A sprain, also known as a torn ligament, is the stretching or tearing of ligaments within a joint, often caused by an injury abruptly forcing the joint beyond its functional range of motion. Ligaments are tough, inelastic fibers made of collagen that connect two or more bones to form a joint. Sprains can occur at any joint but most commonly occur in the ankle, knee, or wrist. The majority of sprains are mild, causing minor swelling and bruising that can be resolved with conservative treatment, typically summarized as RICE: rest, ice, compression, elevation. However, severe sprains involve complete tears, ruptures, or fractures, often leading to joint instability, severe pain, and decreased functional ability. These sprains require surgical fixation, prolonged immobilization, and physical therapy.
Overuse injuries
Causes and prevention
In general, overuse injuries are the result of repetitive impact between the foot and the ground. With improper running form, the force of the impact can be distributed abnormally throughout the feet and legs. Running form tends to worsen with fatigue. When moving at a constant pace along a straight path, a symmetrical gait is considered to be normal. Asymmetry is considered to be a risk factor for injury. One study attempted to quantify the change in running form between a rested and fatigued state by measuring asymmetrical running gait in the lower limbs. The results showed that "knee internal rotation and knee stiffness became more asymmetrical with fatigue, increasing by 14% and 5.3%, respectively." These findings suggest that focusing on proper running form, particularly when fatigued, could reduce the risk of running-related injuries. Running in worn-out shoes may also increase the risk of injury, and altering the footwear might be helpful. These injuries can also arise due to a sudden increase in the intensity or amount of exercise.
Shin splints
A shin splint, also known as Medial Tibial Stress Syndrome (MTSS), is pain along the inside edge of the shinbone (tibia) due to inflammation of tissue in the area. Generally this is between the middle of the lower leg to the ankle. The pain may be dull or sharp, and is generally brought on by high-impact exercise that overloads the tibia. Groups that are commonly affected include runners (especially on concrete or asphalt), dancers, gymnasts, and military personnel. Rates of shin splints in at-risk groups range from 4% to 35%. The condition occurs more often in women. Shin splints are generally treated by rest followed by a gradual return to exercise over a period of weeks.
Stress fractures
A stress fracture is a fatigue-induced bone fracture caused by repeated stress over time. Instead of resulting from a single severe impact, stress fractures are the result of accumulated injury from repeated submaximal loading, such as running or jumping. Because of this mechanism, stress fractures are common overuse injuries in athletes.
Stress fractures can be described as small cracks in the bone, or "hairline fractures". Stress fractures of the foot are sometimes called "march fractures" because of the injury's prevalence among heavily marching soldiers. Stress fractures most frequently occur in weight-bearing bones of the lower extremities, such as the tibia and fibula (bones of the lower leg), metatarsal and navicular bones (bones of the foot). Less common are stress fractures to the femur, pelvis, and sacrum. Treatment usually consists of rest followed by a gradual return to exercise over a period of months.
Achilles tendinitis
Achilles tendinitis is inflammation of the Achilles tendon, resulting in pain along the back of the leg near the heel. There are two types of Achilles tendinitis, insertional and noninsertional. Noninsertional Achilles tendinitis is the type that more commonly affects runners. In this case, inflammation is occurring in the middle portion of the tendon, whereas insertional Achilles tendinitis is inflammation located where the tendon connects (inserts) to the heel bone. Having tight calf muscles may also increase the risk of Achilles tendinitis. Stretching the calves before starting heavy exercise may help relieve tightness in the muscles.
Patellofemoral pain syndrome
Patellofemoral pain syndrome is associated with pain in the knee and around the patella (kneecap). It is sometimes referred to as runner's knee, but this term is also used for other overuse injuries that involve knee pain. It can be caused by a single incident but is often the result of overuse or a sudden increase in physical activity.
Iliotibial band syndrome
Iliotibial band syndrome (ITBS) is defined as inflammation of the iliotibial band on the outside of the knee. This inflammation occurs a result of the iliotibial band and the outside of the knee joint rubbing together. The resulting pain typically is initially mild and worsens if running continues. Recurrence is a common issue with iliotibial band syndrome, as pain goes away with a period of rest, but symptoms can easily come back as the runner returns to training. During recovery, the muscles on the outside of the hip can be stretched to reduce tightness in the band.
Plantar fasciitis
The plantar fascia extends from the heel bone to the toes, and helps support the arch of the foot. Plantar fasciitis is a common cause of heel pain and affects about two million people in the United States. Though once considered an inflammatory condition, plantar fasciitis is now characterized as a degenerative pathology. Intrinsic risk factors include obesity and limited ankle flexibility. Extrinsic risk factors include deconditioning, hard surfaces, inadequate stretching and poor footwear.
Footwear
Traditional running shoes
So-called "traditional" running shoes are designed to give more support and cushion the landing to reduce the effects of impact. They allow for more-comfortable running on hard surfaces such as asphalt and also protect the foot when stepping on rocks or other potentially sharp objects. However, the cushioning provided in traditional running shoes is thought to encourage a foot strike pattern where the heel lands first. Heel striking generates a relatively large amount of impact force that can put different parts of the lower extremities under excessive stress.
Barefoot running
Barefoot running has been promoted as one method of reducing the risk of running-related injuries. Barefoot running is thought to improve running form by encouraging forefoot striking. The collision of the forefoot with the ground generates a significantly smaller impact force in comparison to striking heel first. However, barefoot running leaves the foot unprotected from stepping on sharp objects. Although running barefoot may reduce the risk of running-related injuries, it is important to take time while switching from running with shoes.
Beginning to run barefoot without reducing intensity or mileage of training can actually cause muscle or tendon injury. Changing one's style of running shoe or switching to barefoot running will most likely alter the foot strike pattern, meaning that the force of impact will be absorbed differently. Injuries are more likely to occur in novice barefoot runners. This may be a result of not yet having fully adapted to a new style of running, and therefore running with inconsistent technique. To measure this, a study was conducted involving runners who habitually run with a rearfoot strike while wearing shoes. Of the runners involved in the study, 32% used a heel strike pattern in initial attempts at running barefoot. Running barefoot while heel striking leads to increased muscle activation and impact accelerations. The findings suggest that an inconsistency in running technique among novice barefoot runners may put them at a higher risk of injury in comparison to running with shoes.
Endurance running hypothesis
According to the endurance running hypothesis, long-distance running may have played a significant role in the lifestyle and evolution of early hominins. Before developing more-advanced hunting tools such as the bow and arrow, early humans are thought to have used endurance running for scavenging and hunting. Persistence hunting is "a form of pursuit hunting in which [the hunter uses] endurance running during the midday heat to drive [prey] into hyperthermia and exhaustion so they can easily be killed". Unlike many medium-to-large mammals that use panting as a form of evaporative cooling, hominins rely on sweating, allowing evaporation to occur on a much larger surface area. In this way, sweating results in better thermoregulation that allows the hominin to outlast the prey during the chase. This is one potential explanation for the loss of most body hair in humans. Those individuals with less body hair would be able to better thermoregulate while running to avoid overheating. For this species to exist under the endurance running hypothesis, running most likely did not result in the frequency of injuries that it does today, because such an injury to early hominins likely led to starvation. This example would imply that recent ancestors of humans experienced selective pressure to adapt to barefoot running for long periods of time.
Minimalist footwear
As an intermediate option between traditional running shoes and running barefoot, "minimalist" shoes lack thickly cushioned heels and are designed to encourage forefoot striking. Compared to traditional running shoes, one study observed that high-speed runners in minimalist shoes experienced a significant redistribution of mechanical work from the knee to the ankle. Therefore, minimalist shoes may be beneficial for runners who have experienced a knee injury in the past, although the shoes might increase the risk of ankle and calf injuries. As with barefoot running, runners who switch to minimalist shoes should not start out at full training intensity.