The issue of stride length is something that has been battled against for a long time. Usain Bolt has a stride length that seems to eat up ground quicker than any competitor can keep pace with, yet many followers of the ‘running re-education’ community may believe that a shorter stride is better, providing you can increase your leg speed.
This article is a somewhat fickle read that only aims to address a small part of stride length. Forget ankle plantar-flexion range, spinal mobility, thoracic rotation, pelvic rotation, arm drive, head position, emotional resources, body tension etc. This article will focus predominantly on the hip and specifically the muscular contribution.
Before we get into the weeds of ‘which muscles is most important’, let’s consider whether it is even possible to change muscle length. Muscle length is something that has evaded science. I could ruin this article by invading it with my thesis on the effects of stretching on muscle length and performance. I can summarise these briefly:
Little quality evidence exists to support the use of one stretching against another for increasing ROM or stride length. Although Isometric exercises performed in outer range seem to be the latest fad.
Evidence for changing actual muscle length at a level of sarcomeres only exists on rodents and requires weeks of consistent stretching by which time it would probably induce peripheral nerve injury and limb paralysis in humans.
Perceived (transient) muscle length is created by short periods of stretching and the effects are only short lived with no guarantee on actually changing movement patterns or function.
So what’s the point of this article?
How can we create actual or perceived length in muscle, change in ROM or function?
Is it even possible?
What can be done other than stretching?
Stretching has been used for decades with the hope of changing the characteristic of a muscle from being stiff or short to being flexible.
Stretching may help in the short term to change the effect of a stiff muscle but what is the reason for the muscle stiffness?
Is it advantageous?
Does our vocational behavior influence muscle stiffness or length?
If a person sits for 9 hours at work all day, then strengthens their abs in a short position doing sit ups, after which they sit for several more hours on the sofa each day, then I wonder if their abdominal muscles might be short.
How strong is the muscle in mid or outer range during activity?
If the muscle has no strength in outer range, will it ever function well at that length?
Is stretching ever going to change that?
What changes to strengthening and vocational habits need to occur to allow a change in perceived length and movement pattern?
Are we barking up the wrong tree by answering the questions of performance with a mechanical approach?
In the event that a mechanical approach has a role to play in influencing performance, which muscle you choose to stretch for gaining a greater stride length should be methodical in testing. Below are a few ideas of muscles to assess for both hip flexibility and strength before you decide to go for the old faithful hamstring and quad/’hip flexor’.
At the hip, extension mobility is important to allow a powerful forward drive and for this the usual Thomas test allow for assessment of iliopsoas, and to some extent, rectus fermoris/TFL as the knee is also flexed.
A commonly forgotten muscle is Sartorius. Hip drive in running occurs with an extended knee so whilst rec fem and TFL are useful for early swing phase they don’t impede hip extension as much as you think.
Sartorius on the other hand, flexes the hip and the knee, so it will reach maximum length at hip extension and knee extension. It is a lateral rotator of the hip so early lateral rotation of the hip can occur if Sartorius has limited length. Pectineus and adductor longus may also restrict hip extension or perhaps impede the important coupled movements of abduction and lateral rotation which are imperative for hip extension.
To expand on Sartorius, changing its perceived length may give a potential advantage other than optimal extension at the hip. As the leg is able to extend unimpeded, the calf will operate better as the foot propels through high gears. With excessive lateral rotation of the leg, the ankle propels through the lateral border of the foot which can be referred to as low gear propulsion. High gear propulsion uses predominantly the gastrocnemius and low gear propulsion uses predominantly the deep posterior compartment and peroneals.
So what creates shortness in Sartorius? This may be answered in many ways, all of which may be valid. During the running motion we can observe the use of sartorius in hip and knee flexion during the swing phase but this should not be a predominantly active muscle. Correct athletics coaching may hold one of the keys to preventing excessive tone in the muscle by encouraging the biceps femoris (hamstring) to flex the knee, the psoas complex is more capable of flexing the hip once the hamstring has performed its role well. Perhaps poor co-ordination and strength of these muscles leads to compensation by the Sartorius? Perhaps a sedentary sitting lifestyle creates shortness in the sartorius muscle? Perhaps poor gluteal strength causes compensation within Sartorius for it is also a lateral rotator. There may be many more possibilities that are outside the confines of this article and it may be an avenue worth exploring in your own practice.
In the opposite hip movement, flexion can be restricted by hamstring flexibility as well as the gluteals, but it is possible to be more specific than this and there are other muscles that prevent forward swing of the leg.
The hamstring can be separated into medial and lateral groups. Laterally, the biceps femoris is predominantly a knee flexor so will have more influence limiting knee extension.
Medially the semimembranosis and semitendinosis have a main function in extending the hip and this function is supported by the adductor magnus. The difference being that adductor magnus operates as a hip extensor above 90 degrees of hip flexion. So when trying to increased hip flexion and a powerful forward drive, the adductor magnus is another important muscle to test for length as well as strength adducting through the full range of hip flexion.
Hopefully this article has provoked some thought in looking outside of the box when improving function of the hips as opposed to dishing out the same exercises for all patients with low back pain, knee or hip pain. Although tempting to simply work with ‘recipes’, the profession and our clients/athletes sometimes demand more to find a solution to their obstacles.