In last week’s article “How Does Cadence Affect Injury and Performance,” we saw how making a small change to one’s running mechanics can have a significant knock on effect elsewhere in the body.

It is important that we remind ourselves that this change can be for better or for worse, so when modifying our running form it is vital that changes are made gradually (5-10% increments in the case of cadence) and that we listen to the body throughout the process.

Likewise, as we have discussed before, “correct” running form is very much individualized; what works for one will not necessarily work for all.

With that said, there are some “big picture” topics or ideas that generally apply across the board. And one of these is the idea of “gravity”. And that’s what we’re going to discuss today.

Leaning forward: does gravity help?

One idea that has gained popularity through the emergence of structured running styles is that by leaning forwards when we run we encourage “gravity to help propulsion.”

Although I am of agreement that a slight forward lean can indeed help increase running efficiency, I sometimes feel that attributing it to “getting help from gravity” can mask what I regard as a more beneficial explanation of the purpose of a forward lean, and help runners avoid the common error of leaning forwards from the waist as opposed to leaning the whole body slightly forwards in a straight line, from ankle to shoulder.

When Amby Burfoot, Editor-at-Large for Runner’s World, asked running expert panelists Michael Tammaro, Ph.D. (Physicist), Steve Magness, and biomechanist Irene Davis, Ph.D. (director of the new National Running Center at the Spaulding Rehabiltation Hospital in Boston) if leaning forwards helps you run more efficiently by letting gravity do some of the work, the consensus was:

“Gravity can do nothing to improve your running efficiency on a flat surface. That’s because gravity provides no horizontal force; it simply pulls you back down to the earth.”

All three of the panel did however favor a slight forward lean while running.

So what’s it all about?

The importance of hip extension

Last week we saw that during swing phase (when the foot is in the air, from toe-off to foot strike), propulsion of the leg forwards is a passive movement (i.e. with no conscious effort) using a stretch-reflex similar to a sling-shot.

The drawing back of the slingshot is equivalent to the hip flexors (at the front of the hip) lengthening under tension.

As the body moves over the weight-bearing foot, the hip flexors store elastic energy that will later be used for propulsion.

In other words, the more we manage to lengthen the hip flexors under tension, the stronger the forward propulsion (firing) of the leg will be.

So, let’s imagine what happens if you bend forwards at the waist whilst running. You are in effect reducing the range of movement available in the hip flexors, reducing the amount of tension you can achieve, and thus reducing the level of propulsion.

In other words, you are reducing the power of the sling-shot.

This is why having restricted range of movement in the hip flexors can limit running efficiency. The level of propulsion is limited by the amount of elastic energy you are able to store in the hip flexors during hip extension (and likewise during knee and ankle extension where the stretch reflex is also used).

Use it or lose it

Unfortunately, making a living for most of us involves holding the pelvis in a relatively fixed position throughout the day, be it sitting in front of a computer, at the wheel of a car or standing in front of a whiteboard.

The static nature of our daily life is one reason why the hip flexors (at the front of the hip) lose the dynamic mobility required for optimum running efficiency. As a result, runners with restricted hip flexors typically tend to achieve hip extension (get the supporting leg behind them) by dropping the pelvis forward and arching the lower back. This allows the body to pass over the weight bearing foot without the hip flexor needing to lengthen so much.

However, as we have seen, less lengthening of the hip flexors under tension means less storing of elastic energy, meaning less propulsion. By reducing the efficiency of the running action, the lack of pelvic stability can create extra loads on the leg muscles and/or increase stress through the lumbar spine and pelvis. Either of these may increase the chances of injury.

Lean from the ankles, not the waist

Promoting efficient hip extension is one of the main rationales behind adopting a slight forward lean when running. The lean itself needs to start at the ankles and promote alignment of the whole body in a straight line, all the way up to the shoulders.

Maintaining this alignment over long distances however does require a certain level of conditioning, which is why strength and mobility exercises play such an important role in improving running performance.

Weak hamstrings, glutes and lower back can lead to too much of a forward lean, whilst tight quadriceps and hip flexors can encourage leaning forwards from the waist.

Typical cues include “lead with the hips”, “keep your hips pressed forward” and “tuck your backside under your hips” but unless you have sufficient strength and dynamic mobility to maintain such alignment, the coach can keep shouting as much as they want.

Running Biomechanics researcher Jay Dicharry describes how restricted hip extension can also cause runners to run in the “back seat” with their weight over the heel. According to Jay’s studies, this can promote overstriding and the associated problems that we considered in last week’s article.

Testing your hip flexor mobility

A good way to test your range of movement in the hip flexors (all be it in a static environment) is the kneeling tilt. Normally, this is how it goes:

When you first get into the kneeling position (see photo below), note how much tension you feel up the back leg, from the knee to up the thigh and across the hip. The chances are you will not feel too much (as your body will tend to hold your pelvis in a position that avoids tension). Try and tilt the pelvis upwards, such that the waistline at the front of your trousers moves to level or a little higher than the line at the back (as in the right photo below). In other words, tuck your backside under your hips. For many, this movement will not come easily as it requires a coordination of muscle recruitment that your body is probably not familiar with. You may need to practice the movement lying down (tilting your pelvis so your lower back touches the floor) in order to engage the necessary muscles, and then try it again in a kneeling position. Those of you of who can tilt the pelvis upwards (without moving the rest of the body) should now get an indication of any restrictions you may have in hip flexion.

As is often the case, the test becomes the exercise to reduce restrictions. Don’t forget to test and compare both sides!

No one running style reigns supreme

Having given so much weight to the benefits of a slight forward lean from the ankles, it is once again important for us to remember that no one running style suits everybody or indeed wins all races, even at elite level.

The screenshot below taken from the Boston 2011 Marathon shows Gebre Gebremariam (in the green singlet) who finished third with a personal best of 2:04:53 (third also in 2013 with a time of 2:10:38), and Ryan Hall (blue/red singlet) who finished 4th with an American record time of 2:04:58 (but sadly had to pull from Boston 2013).

Just 5 seconds between them, and yet the differences in style are obvious: Hall showing a slight forward lean whilst Gebremariam exhibits a very upright torso.

“What about the 2011 winner and runner up?” I hear you say. Well, in the photo below, you can see Geoffrey Mutai (in the green singlet) who won with a time of 2:03:02, and Moses Mosop (black/red singlet) who came second in 2:03:06. Maybe a slight forward lean is the way to go for the majority of us!

As always, feel free to use the comment box below for debate as the world of running performance is rarely black & white! We welcome your personal experiences, questions and suggestions for future articles.

Happy running!