Andy Murray withdrew from the men’s singles and was not able not to defend his Olympic title in Tokyo due to quadriceps muscle strain. The two-time Olympic champion, who won the men’s singles at London 2012 and Rio 2016, chose to continue competing in the doubles alongside teammate Joe Salisbury, following the advice from the doctors that he could only participate in one event.
The quadriceps muscles are composed of the rectus femoris, vastus medialis, vastus lateralis, and vastus intermedius. The rectus femoris is a two-jointed muscle as it crosses both the hip and knee joint and allows for hip flexion and knee extension. The quadriceps group functions in kicking, jumping, and running.
MECHANISM OF INJURY: Most injuries are noncontact, suggesting that injuries were sustained due to explosive movements, such as sprints and jumps. Acute quadriceps strain injuries happen during sudden forceful eccentric contraction of the muscles to control knee flexion and hip extension. Sports that require a lot of jumping are at high risk for quadriceps strains due to the significant eccentric work that the quadriceps must perform to counteract hip extension during upward propulsion and knee flexion during the landings. Sprinting and football kicking also require the quadriceps to perform significant eccentric work, specifically due to sudden deceleration such as in kicking and cutting, or forceful contraction of the muscles in sprinting, leaving them vulnerable to injury.
Excessive passive stretching or activation of a maximally stretched quadriceps can also cause strains.
Quadriceps strain is common in sports, such as running, jumping, soccer, basketball, or football, with an increased risk with conditions, such as tight/weak quadriceps, muscle imbalance, and/or muscle fatigue. A recent hamstring muscle injury was a risk factor for quadriceps muscle injury, possibly because changes in the biomechanics occur that predispose athletes to injury in different muscle groups (Orchard, 2001).
Of the quadriceps, the rectus femoris is most frequently strained because of the inherent risk of two-jointed muscles with a high percentage of type-II muscle fibers, similar to hamstrings and calf muscle strains. Excessive passive stretching or activation of a maximally stretched muscle can also cause strains. Muscle fatigue has also been shown to play a role in acute muscle injury.
Age was a risk factor for hamstring and calf muscle strains but was not a risk factor for quadriceps muscle strain (Orchard, 2001).
To prevent injuries, trainers, coaches, and therapists should always investigate these potential risk factors, and once identified, they should be addressed and fix with appropriate treatment/preventive remedies.
Evidence shows that there are ways to prevent quadriceps strain injuries and re-injuries.
An active warm-up should always precede any type of rehabilitation exercises as it has been shown to activate neural pathways in the muscle and reduce muscle viscosity (see reference). A proper warm-up begins with mild aerobic activity for 5-to-10 minutes to increase blood flow to the muscles, which increases their temperature and makes the fibers more responsive to stretching.
Quadriceps muscle flexibility should be part of any prevention program targeted to reduce rectus femoris injury. Dynamic stretching is preferred because, unlike static stretching, it is not associated with strength or performance deficits as studies suggest that dynamic stretching may even increase acute muscular power, such as leg extension power as demonstrated in one study.
Strengthening helps in improving muscle function, range of motion, and mobility, increasing efficiency and performance as well as reducing fatigue, all of which can greatly reduce the chances of injury. The benefits of targeted strengthening exercises have been documented, as they promote the strengthening of the soft and bony structures. Strength training needs to be targeted and specific, that is, strengthening the right muscle specific to its function relative to the condition where injury typically occurs. As calf strain is often associated with the weakness in the eccentric strength of the gastrocnemius, resistance exercises targeting eccentric strength, as well as strength endurance have been implicated in preventing future muscle strains.
Jump-landing training focusing on decreasing the quadriceps to hamstring ratio is already recommended to decrease the risk of injuries for anterior cruciate ligament ruptures during jumping tasks, which may also apply to decrease the risk of quadriceps strains (see reference)
Athletes should strengthen their quadriceps eccentrically, which was also seen to decrease the incidence of hamstrings strains(see reference).
Core stability has been shown to decrease chances of lower extremity injuries, including injuries to the quadriceps muscles (see reference).
While stretching techniques have been proven to be effective in increasing muscle flexibility, studies have reported stretching, both static and dynamic, may cause a reduction in the maximal force output of the muscle (see reference). The application of localized vibration to the hamstrings of one leg has been reported to increase its flexibility without affecting the isometric strength of both the hamstrings and quadriceps of either leg (see reference). These suggest that localized vibration therapy, such as by Recovapro, may enhance or replace stretching for gaining flexibility without affecting the strength of the muscles.
CREDIT: Andy Murray Photograph by Lucy Nicholson/Reuters and Adam Pretty/Getty Images