Hip Extension

Do you have adequate hip extension?

Running is an integrated and skilled movement. We have discussed motor patterns and programming in previous posts. Today we briefly discuss hip extension mechanisms (or lack of) and resultant forces in the lower limb.

It is common to see running technique with a torso/ trunk that is behind the centre of mass (COM), particularly when fatigue sets in. At the centre of this is the position of the pelvis and the musculature acting upon this.

The driving force behind this is almost always poor pelvic position. This occurs most commonly due to posterior pelvic tilt. Another position may exist where an anterior pelvic tilt is observed with overly tight (short) hip flexors disrupting full extension of the hip. For now we will focus on lack of hip extension in  the following two forms:

·      Posterior pelvic tilt (the pelvis is tucked under)

·      Anterior displacement of the pelvis (essentially a posterior pelvic tilt with the pelvis displaced anteriorly fostering a host of biomechanical faults)

These postures create a nutated (‘tucked under’) sacrum jamming the ability of the boney innominates to rotate around the sacrum disrupting full hip extension. A lack of full hip extension will result in a posterior lean during the stance phase of gait to accommodate lack of range of motion and resultant weakness. This position decreases demand on the hip extensors by reducing hip flexion. The result is an increased work on the knee due to increased knee flexion moments. In this case (reduced hip extension) the glute max, hamstring and adductor magnus and a host of deep glute stabilisers decrease their activity due to length tension relationships within the pelvis.

The increased knee moment loads the patella-femoral joint. Larger forces across the knee joint are due to the eccentric loading as the quadriceps slows the increased knee moments. These larger angles have been associated with patella-femoral pain, a leading cause of over use injury in distance runners.

Lack of hip extension increases overstriding.  Overstriding is seen when we land in front of the bodies COM essentially creating a rear foot strike increasing collision forces. Dan Lieberman (2010) found this in his correlation between habitually shod and barefoot runners. The piece of information we don’t have conclusive evidence for is whether this increased collision force increases injury risk. The more important factor here is probably not how you land but ‘where ‘ you land. More research in this area is needed.

Landing outside the COM also puts the hamstring at a biomechanical disadvantage attempting to decelerate the limb at peak knee extension just before stance phase. In this position there is a decreased pre stretch which loses the ability to fully use the stretch shortening cycle (SSC). This is often termed ‘free energy’ as the serial elastic components store potential energy in the tendinous structures and myofascial system (predominantly the ‘slings’* through out the body)

A decrease hip extension may also change the toe off phase placing increase loads on the calf musculature as it attempts to push off in a shortened position. Essentially there are larger contractile forces on the calf with less hip extension.

The typical runners body observed here is one with large quads and calves and lazy glutes and hamstrings (they have ‘no bum’). These are injuries waiting to happen in the calves and lumbo-pelvic area.

A further set back of decreased hip extension is lack of stability and loading through the lumbar spine. A posterior tilt ‘opens’ up the lumbar spine lengthening the multifidus and deep spinal stabilisers (rotatores, transversarri, spinales). These protect and stabilise the lumbar spine. When the length tension relationship is disrupted – the stabilisers cannot contract, as they do not have enough muscle fibre overlap – they are too long and weak in this position. Changing the pelvic position towards neutral and some basic re-education usually helps address this however, depending on the health of your back it may take some time to recover from this.

On a very practical level this position of running creates a run that ‘muscles’ and ‘fights’ it’s way through the gait cycle. There is no free fall or use of the SSC every step accelerates and decelerates more than it needs to. Increased amount of rotation will find their way into the gait. This results in a quick onset of fatigue.

If you have the range to get into good hip extension when running but you don’t do it, it’s probably a biomechanical education scenario. In other words you need some education on how to clean up your biomechanics. If you don’t have the range then get your pelvis in the correct position

Try this; Go for a run and tuck your pelvis under. What you’ll find is that it decreases your hip extension, creates large rear foot loading and tightens up the hamtrings. Because your pelvis is in a sense in front of you, a lean back is the most natural thing to do.

In closing start with the pelvis and you’ll be surprised with the changes it can achieve!

Feet Vs Shoes

Barefoot debacle!

Barefoot Running

This is such a big topic and has been one of the hottest in running over the last few years. It is also a very emotive topic with many people hell-bent, one way or the other. I will state for the record that I don’t fall one way or the other, in fact there may be cases for both. I will do my best in the space and time that I have to cover some of the major aspects and try to give a few different practical points while giving it some justice. I will cover some of the research and look at the aspects of injury.

Barefoot running is not new, whether you look at it from an evolutionary point of view or a literature point of view. In fact the opposite may be said. Shoes (as we know them) have only been around for the last 50 years or so, however, the last 30 years and more recently, the last decade has seen huge advances in shoe technology. The question must be asked ‘what are they based on – is there evidence for them?’ If there is no evidence for shoes, do we ditch them and just go barefoot? Or if there is evidence for them, which shoes are best?

Barefoot running is enjoying the limelight at the moment, slowly gaining popularity with a surge at about the same time as the book ‘Born to Run’ (by Christopher McDougall) travelled through distance running circles. This was followed shortly after by Dan Lieberman who published a study in Nature looking at shod (shoes) versus unshod (no shoes) running and foot strike characteristics. He found some interesting (probably not new) foot strike and landing positions.

The shoe companies saw this coming and quickly responded with barefoot running shoes – these are marketed as enjoying the barefoot benefits without the risk of acute puncture injuries. So the question must be asked “do the shoe companies believe in their current shoe technology or do they simply respond to market demand?”

We must consider the reason for wearing shoes. Is it to reduce injury? Is it for performance? Is it for comfort? Is it for trend? Certainly the big debate seems to be around injury rates yet the reasons for wearing shoes are multifactorial. This is not to dismiss the fact that they probably were designed initially to reduce injury. Here we are 30 years on debating on the design, implications and perhaps the viability of the humble running shoe!

Before we jump into looking at either, let’s have a quick recap on running and motor patterning, as this really does relate to this topic and impact on foot strike positions.

Let me state for the record, running is a skill and not simply a skill that we all possess at the same level. It is also one of the few sports where technique seems to be left in the dark. Very few coaches/athletes, even at the top level, regard technique as a major factor in sports performance or injury profile (sprinting, I must say, is quite different). Running like many sports needs to be taught and refined. Good efficient running technique doesn’t happen by accident. Many believe it’s an innate skill and something that just develops over time. There is varying abilities and skill levels. Quite simply there are responders and non-responders

Running is a complex motor pattern generated by the central nervous system. Because distance runners generate similar patterns on each stride they can re-enforce poor motor patterns pretty quickly! What we really need to consider is whether running bare foot changes these poor patterns and if so, does it reduce their risk of injury?

Barefoot Benefits?

Proponents of barefoot running claim a better landing position on the fore foot and mid-foot during the foot strike phase. This foot strike creates lower collision forces and was certainly re enforced by Lieberman et al (2010) when he published a study in Nature showing lower collision forces when habitually barefoot runners made ground contact compared to habitually shod runners. Some barefoot runners in this study did land in a RFS (rear foot strike), but most did not. The key here is habitual – do we assume barefoot to make those similar adjustments in motor patterning to habitually shod runners? Does it take time to create new motor patterns? With regards to lower collision forces, they have not been shown to decrease injury in runners, so the jury is still out on this one.

Fig 1. Zola Bud (second from right) looks to strike rear foot even as she runs at her pace of close to 3 min/km pace! Not all runners strike forefoot while barefoot running.

There are also claims of a more natural foot strike. Natural does not mean better, we could point out many things that are natural but not necessarily better.

Further research by Lieberman (2012) in a retrospective study on foot strike and injury in collegiate level cross country runners found that those who habitually rear foot strike had twice the rate of over use injuries than those that fore foot strike. While this study is certainly interesting it’s not conclusive. It would be interesting to note whether any of the fore foot strikers who experience injury had biomechanical changes towards a more rear foot strike after injury? It would also be interesting to look at speed of movement – do the fastest runners fore foot strike?

Fig 2. This runner looks to a more midfoot strike during his barefoot gait pattern.

A third study again from Lieberman published this year, (2012) were more economical when wearing minimal shoes (fore foot striking) and again more economical when rear foot striking in minimal shoes when compared to the shod condition. There was no difference in the shod condition between forefoot or rear foot striking. This study agrees that minimally shod runners are moderately more economical than traditionally shod (shoes) runners regardless of foot strike, presumably due to elastic energy storage during the stretch shortening cycle (SSC) in minimal shoe running. This is an interesting study with conflicting evidence.

Fore foot strikers were found to have a more plantar flexed ankle, which is said to attenuate the collision forces by presumably loading through the myo-tendinous structures. These structures are more compliant and return energy via the SSC. They also increase muscle activity and presumably energy cost as their muscles must be used in place of the shoe cushioning. This was investigated in a recent research article when researchers looked at the metabolic cost of running barefoot versus shod. Franz et al. (2012) found the energy cost of running to be no less in shoes compared to barefoot. Previous studies have looked at an energy cost of approx. 1% increase per 100g of shoe on a VO2 max test. This would equate to a 3-4% increase in energy cost for most shoes. This is quite energy expensive over a 10km run.

Franz and his team did not find this, in fact they found for foot wear conditions of equal mass shod running had 3-4% lower VO2 and metabolic power demand than barefoot. Does this mean that shoes may increase performance? More research needs to be done to be conclusive.

If we consider the motor pattern aspect and we have someone who runs in a poor pelvic position (remember this influences foot positioning) by placing (them) barefoot will this simply change their hard wired motor pattern? I am not sure this has been studied but I debate that this would occur.  You would find they would either land RFS or mid to fore foot and destroy their Achilles a few months down the track. This is considering someone who is myofascially stiff and cannot run with his or her pelvis in a neutral to anterior pelvic tilt. More mobile athletes will attain this position more easily. Plantar flexing certainly does attenuate forces, however if you have had previous lower limb and/or calf problems this would be a major risk.

Plantar flexion of the ankle will certainly de-load the knee. A small study at the University of Southern Carolina, Hashish (2011) showed that subjects running shod and barefoot had larger mechanical demands shifting away from the knee in the barefoot condition. The load was transferred to the ankle with a larger percentage taken here. Since knee injuries compose such a large number of total overuse injuries this may be a tick for the barefoot condition. However, if you have decreased range of motion at the ankle or previous Achilles problems this may not be such a good idea.


Further biomechanical changes you would expect to see with changes in foot strike (for most, not all) would be an increase in cadence and shorter stride. This also means less time on the ground – as we know this is the slowest portion of the gait cycle. Deceleration is taken through the SSC therefore braking forces are less when compared to shoes. As discussed above this would partly explain why the ankle is more involved in load transference.

The biggest injury risk is for the lower limb namely the Achilles tendon and boney architecture of the foot. The metatarsals will assume a big load as will the plantar fascia. The soleus and gastrocnemius will work harder as the tendon transfers load though the foot to the lower limb. Wakeling et al (2001) showed myo electrical activity to change depending on the level of cushioning. They found less cushioning increased the activity of the muscles. We would consider that barefoot then produces much higher activity producing the reduced collision forces that Lieberman (2010) talked about.

Anecdotally there are many runners who do well and perhaps perform well barefoot. In my experience, having been a runner for a long time and having competed for nearly as many years, there are stories of triumphs and failures from both sides - the barefoot runners seem to speak the loudest.

Practicalities of Barefoot Running

Barefoot running also has its down sides practically. If you live in a cool climate like I do, there are at least 4 months (sometimes more) where you simply cannot run barefoot – it’s too cold!! Even in minimalist shoes it’s tough. If you have any type of circulatory problems to the extremities in the cold (that’s me) running barefoot ceases to be enjoyable.

Further, brittle skin (cracks in the skin) is acutely painful as are the risks of glass and puncture wounds etc. On another very practical level, I dislike paying more for a shoe (minimalist shoes) where it is quite obviously cheaper to produce with less material than your standard running shoe! That has to be marketing! If you do go totally barefoot, that problem would of course be solved.

So why don’t the most elite runners run barefoot? This would most likely be due to marketing than anything else. You get paid big these days for winning a big city marathon with your sponsors logo! The barefoot technology doesn’t seem to have affected the top echelon (yet) - time will tell. Most of the major shoe companies now make a barefoot minimalist shoe - maybe 2013 will see an increase in this?

What I would like to see is a comparison of the middle distance events with regards to barefoot and performance shoes (spikes) ie; performance over the middle distance on the track. Does barefoot offer an advantage or do we need the grip of the spikes?

The Shoe Story

Shoes – There seems to be little evidence in favour of shoes (Richards et al. 2009). Modern shoes appear to encourage a rear foot strike position (RFS), (Lieberman, 2010) and there is little evidence to support that foot type and shoe type lower injury incidence (Joseph et al. 2010). In fact there seems to be very little evidence for injuries possibly related to pronation and shoe type or shoes overall.

Modern day shoes have advanced significantly since the 1970’s yet injury rates remain high. There could be a number of factors here not just shoes (diagnostic techniques, knowledge of injuries, reporting of injuries, increase in popularity of running etc), we’ll keep our focus on shoes for now.

Ground reaction forces in shoes seem to have a double peak. Clarke et al. (1983) showed that a softer, more cushioned shoe had a similar magnitude force but slower time to reach vertical impact force peak, in other words it takes longer to reach the peak force but the magnitude was the same. Does this matter in terms of musculoskeletal adaptation? Do we need an adjustment [time] going from eccentric to concentric contraction? These are all questions that need to be answered.

In 2008 Wegner et al. showed two types of neutral running shoe to be more effective at cushioning, reducing plantar pressures than a control shoe (Dunlop Volley’s). Further to this Wakeling, Tscharner and Nigg, (2001) found that different materials affected loading rates and muscle activity in the leg as a tuned response to ground reaction forces. They found, depending on the type of cushioning will determine the myo-electrical activity in the leg. Leg activity will be greater in a less cushioned shoe.

The question is “does the reduction in plantar pressure or peak impact reduce injury rates? Does comfort play a role?”. In this same study Wegner (2008) reported the softer neutral running shoes to be more comfortable than a control. If you are running a marathon, you want to be comfortable. This is a practical yet often overlooked component - it is difficult from a comfort point of view to run across gravel laden bush trails – even in minimalist shoes.

So why do so many wear shoes? That’s a really interesting question and for most they probably don’t know or it’s just something that they’ve always done. How much does comfort play a role? It would seem logical that a base of cushioned foam underneath your foot will help protect you from potential injurious loading forces.

If placing cushioning underneath your foot creates a RFS, which increase collision forces – we could ask the question “can we actually run with a forefoot strike in shoes?”. I believe we can – however it would probably take a conscious effort to do so and a lot of effort to change that motor pattern.

Despite a lack of conclusive evidence in favour of shoes, this does not mean they are bad or do not play a significant role in performance, comfort and injury reduction. Just because we ran for 1000’s of years without shoes, this also does not mean that they do not serve a purpose for runners.

The interesting point about injury rates is this; If you had a non runner go out for a 20 min run in running shoes they would probably make it, albeit sore the next day. If you asked that same person to do this barefoot – you would be confident in thinking they would not make it or injure themselves. There are a variety of factors involved here not just myo-tendinous load.

There is inconclusive evidence for barefoot and shoes, though there is a lot of barefoot research being published and looking at shod versus unshod. I think barefoot has some merit, though it must be done slowly initially. Perhaps the very fact you do less running unshod (initially) is one of the reasons you may find a reduction in injury.

Conclusion – The debate with barefoot and shoes will go on. Some will find it the most efficient way to run, others will find it an injury waiting to happen. Only a slow progression and trial and (hopefully not much) error will answer this. If this raises more questions than it answers, then we are in a good place.
Jimmy

References

1. Daniel E. Lieberman, Madhusudhan Venkadesan, William A. Werbel, Adam I. Daoud, Susan D’Andrea, Irene S. Davis, Robert Ojiambo, Mang’Eni & Yannis Pitsiladis, (2010), Foot strike patterns and collision forces in habitually barefoot versus shod runners, Nature 463, 531-535 (28 January 2010)

2. Adam I. Daoud, Gary J. Geissler, Frank Wang, Jason Saretsky, Yahya A. Daoud, and Daniel E. Lieberman, (2012), Department of Human Evolutionary Biology, Harvard University, Cambridge, MA; Department of Athletics, Harvard University, Boston, MA; University Health Services, Harvard University, Cambridge, MA; and Baylor Health Care System, Institute of Health Care Research and Improvement, Dallas, TX , Foot Strike and Injury Rates in Endurance Runners: A Retrospective Study, Medicine in Science and Sports Exercise, Jul; 44 (7):1325-34

3. Franz JR, Wierzbinski CM, Kram R, (2012), Metabolic cost of running barefoot versus shod: is lighter better? Medicine and Science in Sports and Exercise [44(8):1519-1525]

4. Rami Hashish, Sachithra Samarawickrame and George Salem, (2011), Ground Reaction Forces In Barefoot Running Before And After Exertion, University of Southern California, Los Angeles, CA, USA

5. James M. Wakeling, Vinzenz Von Tscharner, Benno M. Nigg, and Pro Stergiou, (2001), Muscle activity in the leg is tuned in response to ground reaction forces, Journal of Applied Physiology September 1,  vol. 91 no. 3 1307-1317

6. C E Richards, P J Magin, R Callister, (2009), Is your prescription of distance running shoes evidence-based?

7. Joseph J. Knapik,, Daniel W. Trone, David I. Swedler, Adriana Villasenor, Steve H. Bullock, Emily Schmied, Timothy Bockelman, Peggy Han, and Bruce H. Jones, (2010), Injury Reduction Effectiveness of Assigning Running Shoes Based on Plantar Shape in Marine Corps Basic Training, J Sports Med;43:159-162

8. Clarke TE, Frederick EC, Cooper LB, (1983), Effects of shoe cushioning upon ground reaction forces in running, International Journal of Sports Medicine [4(4):247-251]

9. Caleb Wegener, Joshua Burns and Stefania Penkala, (2008), Effect of Neutral-Cushioned Running Shoes on Plantar Pressure Loading and Comfort in Athletes With Cavus Feet: A Crossover Randomized Controlled Trial, Am J Sports Med November vol. 36 no. 11 2139-214

10. Lieberman D , Daoud A,  (2012), Effects of footwear and strike type on running economy, Medicine in Science and Sports Exercise, Jul;44 (7):1335-43

‘Windmill Arms’ and ‘Beating the Drum'

A post on the direction of arms and the flow-on effect to the pelvis and lower limb.

How often have you seen the windmill arm action or one arm doing something quite different to the other? You might ask, what difference does it make? You may also ask does it change biomechanics enough to make a difference? Let’s explore this from a practical perspective.

The arms are like a cadence monitor - if we want to accelerate we drive our arms faster to cause an action/reaction in our legs. Ideally both arms should move in a similar path matching our stride. This produces a more even stride with similar timing in the air and on the ground, left side to right side. But what happens if we have one arm moving relatively well and the other is externally rotating or waving out to the side?

Fig 1. You can see the right arm externally rotating. This runner is probably navigating a corner/road deviation however, a rotation of this magnitude in the arm should not occur.

What you will see is a slower arm drive on the side of external rotation. A few things are occurring;

·      The arm drive is slower as it travels a further distance (in a circular motion away from the body)

·      The contralateral leg has to react to this by slowing the swing phase slightly or producing an abducted leg swing (we’ve all seen these)

·      The lack of movement in a more linear plane will not take advantage of the stretch shortening cycle (SSC), (our ability to store and use kinetic energy). This stored energy is often considered free energy and is most evident in activities that produce eccentric actions with ground contact. This also occurs in running through out our posterior sling*

Fig 2. This runner is externally rotating his left arm (away from his body). This will probably change the right leg swing phase to an abducted (away) from the midline position.

This will appear as a jerky gait or someone that appears to have a slight limp. The arm swing in effect is slowing a portion of the gait. Another consideration is the loading on the opposite side. Does it increase time on the ground and loading in stance phase? This would be hard to prove unless a force plate is used. Needless to say it’s less than ideal.

A similar scenario in the lower limb can be caused by what a friend of mine calls ‘beating the drum’. This occurs when the arm extends back but does so from the elbow. taking the arm from about 90 degrees to 130-150 degrees. Again, this is slower not only because it has to travel further but also because more force is needed to propel a longer lever.

Does this increase injury? Again, this would be hard to prove. Having said that, if you do possess a musculoskeletal imbalance then this would most likely increase your injury risk.

Can you change this? Of all the biomechanical dealings with distance running I find this one the easiest and often the biggest change to running efficiency and perception. Changing arm swing would seem to be easier because you have more co-ordination and finer movement control over your upper limbs (more receptors per gram of tissue when compared to the pelvis and leg musculature).

Often there is an immediate change to the stride pattern and a more even running pattern. It also feels lighter on the foot strike to the same as the arm which externally rotates.

So the arms do more that just go back and forth, they can literally dictate actions of the lower limb and influence pelvic function. Next time you run, think about what your arms might be doing

* Posterior sling: An anatomical sling extending from our hamstring, sacrotuberous ligament, gluteus maximus, to the contralateral lumbo-dorsal fascia into our lats. This sling acts like a spring storing energy from side to side with each stride

Mortons Neuroma

A relatively common injury in the forefoot is a condition called Morton’s neuroma. Let’s take a quick look at how it might affect the distance runner:

Anatomy

The interdigital nerves between the metatarsals provide sensory feedback. These nerves do not provide movement (motor) to this area hence their innervation is primarily to the skin, giving tingling and acute sensory pain. The most common area is between the third and fourth metatarsals however, it can occur between the first and second or second and third metatarsals. The metatarsal heads are covered with layer subcutaneous fat (padding) to reduce compressive load.


Fig 1. A build up of fibrous tissue around the interdigital nerve can cause pain and compression of the nerve, limiting mobility.                                                       

Cause

Morton’s neuroma most commonly comes on after a period of loading to this area or after being placed in a prolonged stretch position (think of gardening or tiling the bathroom floor!) In this position your toes go into an extended position placing the interdigital nerve on stretch. This position ‘irritates’ the nerve, setting off an inflammatory cascade. Further compression through this area is commonly associated with poor foot biomechanics. In this scenario the forefoot fails to re-supinate on take off. This places increased pronation and compressive force between the metatarsal heads. After a number of insults, scar tissue tends to gather around the nerve, causing thickening and decreased mobility.

Signs and symptoms

Morton’s neuroma often presents with acute local pain on weight bearing made worse by stretching with the toes in an extended position. It is often described as a burning or sharp neural pain, sometimes referring into the toes. It may warm up initially however it tends to worsen throughout the run.

Treatment

Treatment about this area needs to address and modify any factors of causation (if they can be identified). Most commonly clinicians will look to modify any foot abnormalities such as increased pronation, poorly fitting shoes, poor glute control further up the chain. Decreased ability of the great toe (hallux) to go into extension places further load on the area. Clinically we find passive great toe extension of 60 degrees to be adequate. This allows the forefoot to supinate on toe-off, decreasing compressive forces.

Fig 2. Local corticosteroid injection to the nerve. The injection is aimed at 'bathing' the nerve with cortisone.

It is very difficult to manually address the soft tissue fibrosis around the area. If there is limited mobility about the forefoot joint mobilisation may help. Often donut padding around the area is enough to de-load the forefoot and help spread load across the metatarsal heads. Further treatment may involve mobilising the nerve. In chronic cases cortisone to the affected area can provide short-term relief. In recalcitrant cases excision of the offending tissue may be performed.

Fig 3. Recalcitrant cases may need to resort to surgery.Conservative treatment should be explored first. 

Differential Diagnoses

Less commonly there may be inflammation of the bursa that lie within the interdigital space. The cause is similar, an increase in toe extension as may occur with an increase in speed work or hill running. Pain originating from the bursa is usually painless with passive ranges of motion however particularly painful with active range of motion. Bursal pain does not warm up and increases with increased loads. In these cases the initial treatment is similar with regards to causation. Further to this, cortisone is effective at decreasing inflammation within the bursa.

Fig 4. The arrows show the close proximity of the nerve and the bursa demonstrating a possible co-existence. An inflamed bursa may place extra pressure on the adjacent nerve.

The possible side effects of corticosteroid injection (particularly repeated at the same site) are atrophy and degeneration of the fat pad. This can lead to increased load through the boney and tendinous architecture through the forefoot. 

Prognosis

Morton’s neuroma can be quite difficult to treat, especially if caught late. Once thickening starts to occur around the nerve, it becomes more likely to become irritated again causing further tissue thickening. This creates a vicious cycle. This is one of those injuries that can flare up quite quickly and then lay dormant for a few months before returning.