Be Nice to Your Hamstrings
It is a near constant to see exercise participants of all ages engaging in the prolonged static stretching of a given muscle or muscle group. From competitive sport to physical education classes to yoga, passive static stretching has been a mainstay. It is particularly common to see a variety of stretches for the hamstrings being utilized, however, this may not be the path to performance and injury resilience that many believe it to be. Increased mobility, pain-free function, and injury risk reduction may be contingent upon flipping the relationship between strength and flexibility in the lower extremity as we stretch our quadriceps, instead of strengthening them, and strengthen our hamstrings, instead of stretching them.
Anatomy
The interconnectedness of the tissues of the human body should not be underappreciated when we consider how and why we stretch. A prime example is the lumbopelvic-hip complex. Essentially, the quadriceps and the hamstrings meet at the pelvis, two connected structures called innominate bones, creating a three-dimensional fulcrum. If one imagines a rather complex marionette, there is a basic relationship between the anterior thigh (quadriceps and hip flexors) and posterior thigh (hamstrings and glutes) that can affect and be affected by the muscles of the abdominal wall and low back, via the pelvis, which share a similar basic anterior/posterior, or front to back, relationship.(1)
Mechanics
As this relates to the muscles of the thigh, typically, the resting position of the quadriceps is short, think when lying on your stomach or back, sitting in your favorite easy chair, or lounging at the beach, while the hamstrings are typically resting in an elongated, or taught, position. The same holds true for much of the day when walking or standing. As such, the hamstrings are inherently at a disadvantage that is made more pronounced when they are placed into a further elongated position via static stretching, giving up more ground to the quadriceps as it relates to the pelvic fulcrum and becoming weaker.(1-5)
Strength Imbalances
Some researchers suggest that the ratio of hamstring to quadriceps strength should be roughly 0.6, meaning that the hamstrings should possess 60% of the strength of the quadriceps.(6,7) In athletic populations, it has been suggested that this strength ratio be closer to 1.0, or equal, for purposes of injury prevention.(6,7) Given that static stretching has been shown to weaken force production, reduce strength endurance, and diminish sprint performance, we may be putting ourselves at a mechanical disadvantage by habitually utilizing static stretching of our hamstrings, potentially predisposing ourselves to harm in the pursuit of injury prevention.(2-5)
But what do I do if I can’t stretch?
As a general rule, we still want you to stretch. It is all about timing, (post-exercise v. pre-exercise), type (dynamic v. static), and perhaps most importantly, what area of your body is becoming more mobile and what mechanical changes are occurring as a result. For example, if we use the model of the pelvis as a three-dimensional fulcrum mentioned above, stretching the quadriceps, with an emphasis on movement, may help reduce tension in the hamstrings by reducing the anterior, or forward, tilt of the pelvis and increasing hip mobility in multiple ranges of motion prior to training or competition. If we consider strength imbalance as part of our dysfunctional hip and pelvis equation, another key step may be the addition of high-quality posterior chain focused strength and conditioning training such as deadlifts and kettlebell swings.(8,9) So keep stretching, training, and playing, but be mindful that sometimes our attempts at preventing injury aren’t always what they seem.
References
1. Janda V. Muscles and motor control in low back pain: Assessment and management. In: Twomey Lt. Physical therapy of the low back. New York, Edinburgh, London: Churchill Livingston, 1987;253-87
2. Ogura Y, Miyahara Y, Naito H, Katamoto S, Aoki J. Duration of static stretching influences muscle force production in hamstring muscles. J Strength Cond R. 2007;21(3):788-92
3. Nelson AG, Kokkonen J, Arnall DA. Acute muscle stretching inhibits muscle strength endurance performance. J Strength Cond Res. 2005;19(2):338-43.
4. Nelson AG, Driscoll NM, Landin DK, Young MA, Schexnayder IC. Acute effects of passive muscle stretching on sprint performance. J Sports Sci. 2005:23(5);449-54
5. Winchester JB, Nelson AG, Landin D, Young MA, Schexnayder IC. 2008. Static stretching impairs sprint performance in collegiate track and field athletes. J Strength Cond Res. 2005:22(1);13-19.
6. Coombs R and Garbutt G. Developments in the use of the hamstring/quadriceps ratio for the assessment of muscle balance. J Sports Sci Med. 2002:1(3); 56-62.
7. Holcomb WR, Rubley MD, Lee HJ. Effect of Hamstring-Emphasized Resistance Training on Hamstring: Quadriceps Strength Ratios. J Strength Cond Res. 2007:21(1);41-47.
8. Lake JP and Lauder MA. (2012). Kettlebell swing training improves maximal and explosive strength. J Strength Cond Res. 2012:26(8);2228-33
9. Zebis MK, Skotte J, Andersen CH, Mortensen P, Petersen HH, Viskær TC, Jensen TL, Bencke J, Andersen LL. Kettlebell swing targets semitendinosus and supine leg curl targets biceps femoris: an EMG study with rehabilitation implications. Br J Sports Med. 2013:47(18);1192-98.