Photo by Jay Prasuhn

The ability to assume an aerodynamic position on the bike is critical for maintaining speed during long course triathlon. Tolerating an aggressive position not only takes time for the tissues of the body to adapt, but also requires adequate flexibility of key lower extremity musculature. The hamstring muscle group receives particular attention when it comes to improving time trial position, given its anatomic location and unique function as a two-joint muscle group. The hamstrings consist of three long muscles that originate off the pelvis at the ischial tuberosity (sit bone) and travel down the back of the thigh before crossing the knee joint and inserting on both sides of the upper leg. The lateral hamstring is known as the biceps femoris and is comprised of a short head and long head while the medial hamstring consists of the semimembranosus and semintendinosus. The hamstrings not only act to extend the hip and flex the knee but also help to rotate the leg inward and outward.

When the hamstrings are tight they cause the pelvis to rotate backwards, thereby flattening the lower back. Triathletes suffering from hamstring tightness may find their ability to assume a more aggressive time trial position limited by an inability to flex forward at the level of the trunk. This leads to compensations at the level of the spine and shoulders in an effort to get outstretched so the arms can rest on the aero bars.

It’s not surprising that cyclists and triathletes report a high incidence of neck and low back pain (Manninen et al., 1996; Villavicencio et al., 2006; Clarsen 2010). Consequently, fitness and medical professionals who work with triathletes routinely stretch the hamstrings to safeguard against injury while improving time trial performance. Given the focus placed on hamstring flexibility, it is critical to not only understand the most effective approach to stretch this muscle group but to also realize that the nerves, which exit the spine and course through the soft tissues of the thigh and leg, can limit one’s range of motion during hamstring stretching (McHugh et al 2010). Failure to consider the role of the nerves in the context of hamstring stretching will not only decrease the efficacy of the stretch but may also lead to strength loss of the hamstrings.

There are a variety of ways to stretch the hamstrings. A few of the more common approaches include 1) bending over to touch the toes, 2) performing a sit and reach maneuver, and 3) propping your leg on an object at waist level while leaning forward. When performing these stretches, an emphasis is routinely placed on keeping the knee straight while flexing forward at the trunk and reaching. Unfortunately, stretching the hamstrings in this manner places greater load on the nerves. This was recently demonstrated by McHugh et. al., who investigated the role of neural tension in hamstring flexibility (McHugh et al. 2010). The authors showed that flexing the neck and upper back during hamstring stretching resulted in a 10 percent decrease in the maximum ROM that could be achieved as compared to maintaining the spine in a neutral position. Furthermore, numerous studies have documented acute losses of strength following stretching in this manner. While the mechanism of this strength loss remains unclear, it has been suggested that it may be due to sustained stretch of the nerves. In an animal model, sustained stretch of the nerves has been shown to result in decreased nerve conduction velocity that was present up to 30 minutes after release of the stretch.

So what does all this mean when it comes to improving your time trial position? The optimal approach involves a combination of stretches designed to target hamstring flexibility as well as nerve glides to ensure that the nerves are able to adequately glide through the surrounding tissues. Keys to success when stretching your hamstrings are twofold. First, you should afford a small amount of bend in the knee to put the nerves on slack. This biases the stretch to the hamstrings. Secondly, it’s important to maintain a neutral spine since flexing the neck and upper back places a greater load on the neural tissue and limits range of motion. If you’re stretching the hamstrings properly, you’ll feel the stretch in the back of the thigh. With regards to improving mobility of the nerves, an emphasis should be placed on movement rather than sustained stretching.

I’ve put together three videos to accompany this article. The first two demonstrate a supine (lying on back) and standing hamstring stretch, respectively, while the third video shows a “nerve glide” geared toward improving mobility of the neural tissue. To determine the efficacy of these interventions, try getting into a time trial position before and after to experience the difference for yourself. Hamstring stretches should be held for 90 seconds and repeated five times (Magnusson et al. 1995). In the case of the nerve glides, start by performing three sets of 15 while holding the last repetition of the third set for five seconds.

Video 1: Supine Hamstring Stretch

Video 2: Standing Hamstring Stretch

Video 3: Neural Mobilization

References:

1. Clarsen B, Krosshaug T, Bahr R. Overuse injuries in professional road cyclists. Am J Sports Med 2010. Dec; 38(12):2495-501.

2. Magnusson SP, Simonsen EB, Aagard P, Gleim GW, McHugh MP, Kjaer M. Viscoelastic response to repeated static stretching in the human hamstring muscle. Scand J Sports Med. 1995 Dec; 5(6): 342-7.

3. Manninen JS, Kallinen M. Low back pain ad other overuse injuries in a group of Japanese triathletes. Br J Sports Med 1996. Jun; 30(2):134-9.

4. McHugh MP, Johnson CD, Morrison RH. The role of neural tension in hamstring flexibility. Scand J Med Sci Sports 2010. Aug 24.

5. Turl SE, George KP. Adverse neural tension: a factor in repetitive hamstring strain? J Orthop Sports Phys Ther1998. Jan; 27(1):16-21.

6. Villavincencio AT, Burneikiene S, Hernandez TD, Thramann J. Back and neck pain in triathletes. Neurosurg Focus 2006. Oct 15; 21(4): E7.

7. Villavincencio AT, Hernandez TD, Burneikiene S, Thramann J. J Neurosurg Spine 2007. Oct; 7(4):408-13.

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Chris Johnson is a leading New York City physical therapist who specializes in the care of endurance athletes. In addition to being the owner and director of Chris Johnson PT, located in the Flatiron District of Manhattan, he is also a co-founder of Formula Triathlon Club, and an all-American triathlete. Chris also shares tips and advice for multisport athletes on his blog, “Critter’s Corner,” at www.chrisjohnsonpt.com.