INTRODUCTION
- Roughly 50% of sprinters muscle injuries are to hamstrings; and 40% of soccer players injuries.
- Most likely to occur within the first 10 weeks of the season program.
- Strongest indicator of risk is imbalance hamstring (weaker ) versus quadricep ( stronger ) strength.
- The key factors are: 1. tight rectus femoris (2) deactivated glutes (3) Possibly poor ankle mobility
- Usually the biceps femoris tears: weak, stretched and overloaded.
- Hamstring injuries are most common during competition.
- Injury commonly occurs in a sprinting scenario.
- Over 18% incidence of injury per season among sprinters.
- 40% over 2 seasons found in track and field athletes.
- 23% per season in Aussie Rules football.
- 16% per season for soccer.
- Older players are at increased risk.
- Re-injury rates run as high as 39% in soccer, up to 31% in Aussie Rules, and 23% in Rugby Union.
In other words, once injured, risk of recurrence increases dramatically. Once a hamstring has been torn, when it recovers, it’s optimum length for active tension is shorter, thereby reducing it’s capacity to withstand excessive lengthening, and predisposing to injury during eccentric loading when nearing full extension. So training programs should focus on prevention against injury. There is significant confusion as to whether hamstring inflexibility plays a big role, or only a minor role in injury risk. It is my opinion that the main issue is anterior pelvic tilt, tight/short hip flexors, and unbalanced strength between quadriceps and hamstrings. Obviously, a flexible hamstring should avoid injury longer than a tight one. Weak glutes are implicated because of their role as concentric hip extensors. Pelvic stability is important to help prevent hamstring injury.
THE IMPORTANCE OF ANKLE MOBILITY
Poor ankle mobility is indicated when ankle dorsiflexion is poor. During mid to late stance phase, the contralateral (opposite side) ankle may restrict a normal stride length, again causing the ipsilateral (same side) leg to over-stride. This limited flexibility precipitates the development of quadricep dominant patterns when the glutes should be firing. This condition causes an imbalance between front and rear thigh, as the quadriceps become too strong for the hamstrings, which in itself can cause hamstring tears, usually the biceps femoris. Added to this, the quads bear too much of the workload, become inflexible, and pull the hips forward into anterior pelvic tilt. The rectus femoris is both a quadricep and a hip flexor, and is the main culprit. Not only is the hamstring weaker than the quadricep, but evidence has proven that they fatigue faster than the quads, with most injuries occuring late in either half of a soccer match. Regardless of the exercise, we find that as exercise duration increases, the hamstring continues to weaken, relative to it’s antagonist, and is unable to generate and absorb as much force in it’s vulnerable range. With fatigue, sprint times slow, and stride lengths shorten, thus placing the hamstring in dangerous territory. Furthermore, the tight quads may also pull one hip more forward of the other, creating internal/external hip rotator imbalances, which quite probably could have originated from the loss of ankle mobility. The external hip rotators become too tight, pulling the hips anteriorly even further. From all this above information, one could assume that poor mobility at the ankles is always found in cases of anterior pelvic tilt, but that isn’t true. Ankle mobility could be sufficient, but hip flexors MUST be tight if the hips are in anterior tilt. If anterior tilt is present, then gluteal function WILL be insufficient, and the hamstrings will be pulled, much like a rubber band, stretched, overworked, and ready to snap somewhere down the track.
POSTERIOR PELVIC TILT
This is a posterior rotation of the pelvis due to very tight/short hamstrings, and is characterized by a flattening of the lumbar curvature, excessive thoracic kyphosis, and increased cervical extension. In this scenario, the hip flexors and quads are weak, but the glutes are still inhibited. The main difference from A.P.T. is a dominant posterior chain, with many of the same issues present. The hamstring is just as susceptible to injury in this condition.
IMPORTANCE OF THE GLUTEALS
They play a twofold role. Firstly, neuromuscular control of the pelvis may allow the hamstrings to function at safe lengths. As posterior rotators of the pelvis, contralateral glutes limit the anterior rotation of pelvis in late stance phase, thereby assisting normal ipsilateral stride length. Furthermore, during early stance phase, the glutes act as synergists to the concentrically acting hamstrings, so if the glutes are firing, they can relieve the hamstrings at this point.
THE IMPORTANCE OF ABDOMINAL MUSCLES
As controllers of pelvic rotation, they can reduce anterior pelvic tilt and the negative effect of tight hip flexors and low-back muscles. In the presence of anterior pelvic tilt they become lengthened and lose reciprocal innervation, and so need to be strengthened as part of the pelvic tilt correction strategy.
CONCLUSION
So what really causes a hamstring tear? Answer: Quad dominant movement patterns.
Key factors: (1) weak and overloaded hamstrings versus much stronger/tight hip flexors and quadriceps. (2) Pelvic instability—including tilting, and unbalanced internal/external hip rotators (3) Under-active gluteals (4) Poor ankle mobility
Shane Shiels
