Hamstring strain injuries commonly occur during sporting activities at the high school, collegiate, and professional levels. Participants in track, football, baseball, soccer and rugby are especially prone to this injury given the sprinting demands of these sports. Dancers have a similar susceptibility due, in part, to the extreme stretch incurred by the hamstring muscles. When it comes to hamstring strains, two things are certain:
- They are super common in athletes, with research showing that almost 30% of all lower extremity injuries in sports are hamstring injuries. In NFL football players, the occurrence of hamstring strains injuries are second, only to knee sprains.
- The rate of recurrence is high, with research showing up to a 30% recurrence rate for hamstring injuries. This is evidence that athletes are rushing back to sport too soon, that return to sport criteria is not being adequately met, or these hamstring strains are not being rehabilitated well.
MECHANISM OF INJURY
A majority of hamstring strain injuries occur during high-speed running during the terminal swing phase of the running cycle. During the second half of swing, the hamstrings are active, lengthening and absorbing energy from the decelerating limb in preparation for foot contact. Running-related hamstring strain injuries typically occur along an intramuscular tendon, or aponeurosis, and the adjacent muscle fibers.
Another common mechanism of injury is with slow or fast movements that involve simultaneous hip flexion and knee extension, placing the hamstrings in a position of extreme stretch, with injuries most commonly presenting in the semimembranosus and its proximal free tendon. Injuries involving an intramuscular tendon or aponeurosis and adjacent muscle fibers (biceps femoris during high-speed running) typically require a shorter recovery period than those involving a proximal, free tendon. This finding is consistent with the observation that injuries involving the free tendon (near the buttocks) require a longer rehabilitation period than those within the muscle belly. The proximity to the ischial tuberosity (bony prominence within the buttocks muscle we sit on) is believed to reflect the extent of involvement of the proximal tendon of the injured muscle, and therefore a greater recovery period. Injuries at ~6.7-7.1 cm from ischial tuberosity may take up to 16 weeks for recovery. Injuries at ~ 2.3-0.8 cm from ischial tuberosity may take up to 50 weeks for recovery.
What does this all mean? Strains of the hamstring that are closer to the buttocks will take longer time to heal and are more susceptible to re-tear due to the biomechanics and force vectors that occur in this region.
4 MISTAKES PEOPLE MAKE WHEN REHABILITATING HAMSTRING STRAINS
1. STRETCHING THE HAMSTRING TOO EARLY
The first mistake we often see is simple, people often load the hamstring tissue way too early. Contracting a strained hamstring causes discomfort, so this is typically avoided. However, for some reason, often people tend to stretch through this pain and discomfort, thinking that if they get “looser” it will feel better.
This is not true, and over-stretching too early is just going to delay the healing process. In fact, research has shown that too much stretching can actually delay the return to sport. This unfortunately happens all too often in the rehabilitation setting, but also from the athlete themselves as they constantly want to stretch or “test” the area throughout the day.
One of the easiest things you can do acutely following a hamstring strain, is to avoid stretching. Some gentle range of motion is encouraged in the acute phase, but we don’t want to stretch the tissue just damaged by an overstretch type of injury. It makes sense not to stress a tissue that has just been torn. By taking a step back in this acute phase and refraining from stretching, you are putting the tissue in a position to succeed in the future phases of rehab when we need to start applying more load for proper healing.
2. LEAVING ECCENTRIC EXERCISES OUT OF THE PICTURE
It has been theorized that hamstring strains are so common due to the large amounts of eccentric contractions that are observed during the swing phase of running/walking as the hip flexes and the knee extends outward. It makes sense that hamstring strain rehabilitation and prevention programs that incorporate an emphasis on eccentric hamstring exercises tend to have better results.
After a hamstring strain, it has been demonstrated that eccentric hamstring strength is impaired.
The common belief is that there is a change in the force-length relationship of the hamstring after an injury, resulting in peak force at a shorter length. But, eccentric training can shift this relationship and allows peak force at a longer length. These results emphasize the importance of including eccentric exercises during hamstring rehabilitation. We also recommend you perform eccentrics with exercises at various degrees of hip flexion, for example the Nordic hamstring exercise at 0 degrees, and a single leg dead lift, which includes hip flexion. This allows for dynamic tensile load that the hamstring is exposed to during sporting activity.
3. OMMITING DYNAMIC HAMSTRING EXERCISES
While it’s vital to incorporate eccentric exercises as part of the rehabilitation of hamstring strains, we are surprised at how little we read or see recommendations for dynamic exercises.
It’s one thing to perform a simple and slow eccentric contraction exercise, and another to perform a dynamic and explosive contraction that mimics the specific movements the athlete performs. At Wright Physical Therapy, we often use lower body plyometrics for this, as it allows both a rapid eccentric contraction, followed by an explosive concentric contraction which is a sport movement.
4. RETURN TO SPORTS TOO EARLY
This is the great debate, when do we return the athlete back to their sport? Several studies show that many athletes return back to sport too quick, showing signs of residual loss of hamstring strength, weakened scar tissue, poor mobility, and imbalances. A rush back to full activity can occur as pain is abolished before the hamstring has regained its full tensile strength throughout the full range of motion and certain risk factors can easily be overlooked.
The risk factors that contribute to the high rate of hamstring re-injury include the following :
1. Persistent weakness in the injured muscle
2. Reduced extensibility of the musculotendon unit due to residual scar tissue, and
3. Adaptive changes in the biomechanics and motor patterns of sporting movements following the original injury.
Unfortunately, part of the problem is that proper return to sport criteria is rarely used in the determination if an athlete is ready to return to sport. A rehabilitation approach focused on objective criteria to progress in the healing process is vital, instead of merely basing a return to activity on pain-free function alone. In our return to sport hamstring protocol, there are 3 specific phases of progression. An athlete is not allowed to progress to the next phase until specific criteria is met that demonstrates the hamstring’s readiness to accept load. Phase 1 focuses on protecting the injury site while minimizing atrophy in the hamstring. Phase 2 emphasizes regaining pain-free hamstring strength, beginning at mid-range and progressing to longer hamstring length. In this phase, we also focus on developing neuromuscular control of the trunk and pelvis with progressive increase in movement speed. Phase 3 is where the athlete is symptom-free during all activities and where integration of dynamic sports specific movements are incorporated to ensure the athlete is ready to return to sport.
We understand the difficulty of navigating a hamstring strain and getting the athlete back to the field quickly and safely. We are here to answer questions as you wade through the waters of this frustrating injury. The knowledge to skillfully heal a strained hamstring is vital and all Wright Physical Therapy Doctors of Physical Therapy are trained at the highest levels of orthopedic specialty. Our team will properly diagnose and treat the hamstring strain through our proven 3 phase approach. Check out our website at wrightpt.com and call us at one of our convenient locations. We will put you in touch with one of our experts so you can get to the root of your pain now!