Making the most of your X-Line Run

The X-line run is part of a range of insoles with a long established and trusted pedigree that are used within the NHS for medical complaints, as well as by the general public for comfort. They offer a foot contoured profile that supports but does not prevent, motions within the foot during activities such as daily walking, hiking, and sport.

Running offers a few distinct differences to walking. In running there is no period where both feet are on the ground and there is an aerial or float phase, where neither foot is on the ground (see figure 1). Interestingly, jogging is defined as neither having a period when both feet are on the ground or an aerial phase.

Figure 1 

he Hip Adduction Angle

What does the X-Line Run do for the hip adduction angle

The other major difference is that in running, the support limb is tucked further under the body than in walking. This is a direct result of not having a period of double leg contact with the ground. In walking, bodyweight can be passed centrally between the two legs when we transfer our support from one foot to the next, with only a short period where one leg maintains all the weight of the
body. Therefore, although we tuck our legs a little under the body when walking, the angle required at the hip to move the legs under us is small. This angling of the leg to the hip is called the lower leg or hip adduction angle or hip varus angle. 

This angle from the hip to the leg means that the body weight can pass over the support leg, but without it being in the way of the opposite leg swinging forward. Thus, body weight needs to be positioned just to the inside of the support leg and then moves towards the opposite foot as it contacts the ground. The distance between a foot on the ground to the next step from left to right, is termed the base of support. This base of support is clearly visible when you walk across sand (see figure 2)

Figure 2

Base Of Support In Running

The base of support in running must be very narrow because bodyweight is basically being dropped onto one single supporting limb (each leg in turn) with each running step, never being supported between the two legs together. Therefore the foot needs to be more under the trunk to support body weight. This requires the hip to tuck the leg more underneath the body by increasing
the hip adduction angle.

Body weight must now be pulled towards the support limbs hip largely through the activity of muscles called the hip abductors. The problem with this limb position is the foot is also presented to the ground at an angle and thus has to rotate inwards (known as eversion or incorrectly as pronation) to bring the foot flat to the ground. Once the foot is flat to the ground, the hip abductors are
able to function better and tend to pull the hip level to better balance the body weight. It is the initial process of loading the foot, leg, and body weight that stresses the system most (see figure 3).

Figure 3

When first contacting the ground (left image), the leg is positioned under the body to support the body weight, with the hip angled inward (adducted). This tends to cause the opposite side of the pelvis to drop a little, which is resisted by muscles on the side of the hip (hip abductors) pulling against the drop. The foot being angled with the leg has to roll inwards to become flat to the ground. Once the foot is flat to the ground (right image), the leg to hip position improves so that it is easy for the hip muscle to keep the pelvis level and the body weight stable.

 

Some Problems

Some runners, for a number of reasons, angle their limb further underneath their body, increasing the hip adduction angle as they impact the ground. This requires more hip abductor muscle power to keep the bodyweight pulled towards the supporting hip.

Other runners have weak hip abductor muscles that struggle to control the hip adduction moment, allowing the bodyweight to fall away from the support limb, causing the hip to drop down too far. This is known as a Trendelenburg sign or gait, and it necessitates the shoulder dropping to twist the body’s weight back towards the support limb. Some unfortunate runners have both problems of high lower limb adduction angles and weak hip abductors that together can cause excessive hip adduction motions during running.

However, most runners only have issues when their hip muscles become fatigued during a longer or more taxing run. These hip angle problems can link to injuries to the iliotibial tract (band) and anterior knee structures (patella or knee cap tracking or stability/issues). Indeed the amount of hip adduction angle during loading is strongly link prospectively to running injuries, i.e, the more your hip angles to the leg, the more likely you are to pick up a running injury over time (see figure 4).

Figure 4

If hip adduction angles are high (more common in female runners), then the hip abductors have to work harder and the foot may roll in further and faster on initial ground contact, as seen in the left image. If the hip abductors aren’t strong enough or become fatigued, stabilising body weight across the pelvis at ground contact can become harder, causing the opposite pelvis to drop down excessively (right image). This in turn requires the body weight and trunk to tilt towards the support limb, causing the shoulder on the support limbs side to drop. This posture is inefficient and increases injury risks.

HealthyStep_®  are very aware of the research that shows this fact, and have therefore constructed a light running insole with all the comfort benefits of the tried and test X-Line range, but with the addition of a small angled heel seat, to help reduce the hip adduction angle and the associated inward roll of the foot. In effect we bring the ground to the leg to give a little help when your hip muscles get tired (see figure 5).

Figure 5

X-Line run insoles have a number of features that reduces the need to excessively adduct the leg under the body and reduces the amount the foot must roll inwards during initial contact. Keeping hip abductors strong and being careful not to over-stride is also important for safe running.

 

Watch Your Stride Length And Keep Your Hip Adbuctor Muscles Strong

HealthyStep_® recommends two ways to control your hip adduction angle.

• Don’t run with a long stride length. Your muscles are more likely to tire and become over strained (see image 6).

Figure 6

• Keep your hip abductors strong with some simple exercises (see figure 7 and text).

 

Hip Adbuctor Strengthening Exercises

Figure 7 

Exercise 1:
Position yourself as shown, standing on one leg with the supporting knee very slightly bent 5°-10°. Keep the inside of the your foot arch raised.

Slowly raise one foot off the ground, hold for 5 seconds, then slowly lower the foot back to the ground again, and straighten both legs and knees. Keep your pelvis as level as you can while you do this.

Don’t let your pelvis tilt or turn inwards (be crooked out of a straight line front on). Try to keep the kneecap of the standing support leg positioned over the 2nd to 3rd toes throughout the exercise. It is important not to let your knee turn inwards during bending the knee.

Repeat the exercise 10 times 4 times daily.

Now try on the opposite foot.

Exercise 2:
If the first exercise becomes easy, try this next exercise:

In the same position as above bending the support knee 5°-10° again but now lift one foot off the ground and hold for 30 seconds.

Repeat 10 times, 4 times daily.

Exercise 3:
If the above exercise 2 becomes easy, then in the same position try briefly lifting the supporting foot’s heel off the ground while standing on one leg, and then let it back down again trying to keep the pelvis level while you do so.

Repeat 10 times 4 times daily.