It is one of the most common tests, touch your toes, or even better, reach forward as far as you can. The goal is to measure flexibility, particularly at the hamstrings. After all, it is one of the most commonly strained muscles, accounting for around 12% of injuries in athletes. Yet, no study has proven that hamstring flexibility will reduce injury rate. In fact, some individuals might even increase the likelihood of injury by improving this range of motion.
First, some definitions. The hamstrings are the three posterior thigh muscles (semitendinosus, semimembranosus and biceps femoris). Flexibility refers to the absolute range of motion in a joint, or series of joints, as well as the length of muscles that cross the joints. The hamstrings are also connected to the back muscles and calves, running from the neck to the big toes. This connection occurs through a thin layer of soft tissue called fascia to make a connection known as the superficial back line. In fact, we have seen phenomenal hamstring improvements by targeting the feet (plantar fascia) alone!
The problem with many tests, like the ones mentioned above, is that any hamstring inflexibility is usually compensated for by range of motion in the lumbar spine, the lower back. So if you can touch your toes, it is hard to truly decipher how much you round your back to achieve this range of motion. This compensation is critical because the lower back serves as a stabilizer, and should not be a major contributor towards flexibility (see Sparta Point).
So the body is not isolated by muscles. If you are tight in your hamstring you’ll be tight in other muscles. And if you’re flexible in your hamstrings, guess what? Our force plate research has solidified these findings particular in the “hinge” movement signature. This signature has extremely high EXPLODE compared to LOAD and DRIVE, an example of this graph is shown to the left. This athlete does not load through the ankle, but rather bends forward at the hips and trunk to produce movement. The result are tight calves to stabilize, tighter hamstrings from over reliance on these extensors. Basically, they are tight and stiff everywhere; making them very explosive but also inflexible to decelerate over a longer period of DRIVE.
One of the best movements to eliminate the explosiveness of “hinge” athletes and stress a longer range of motion is the Overhead Squat (see Sparta Point). It takes the hamstrings through a full range of motion, while stabilizing the lumbar spine. In addition to overhead squat, all movements should be taken through a full range of motion to provide the simultaneous benefit of flexibility and strength (stability).
Be wary of hamstring flexibility tests, they usually include compensation from the lumbar spine
Flexibility is a global attribute, never isolated to one or two muscle groups
The stronger, more explosive movement signatures (“hinge”), require more flexibility
You can also just keep targeting hamstring flexibility, isolating muscles will at least ensure that you will never be finished improving.