Archive for December, 2007

Gordon Pirie

December 31, 2007

Gordon Pirie was world record holder for 5000m and 3000m in 1956. The Guinness Book of Records attributes to him the record for most miles ever run by a human being. In his book, ‘Running Fast and Injury Free’ Pirie states that he ran 240,000 miles in 45 years. He also states that he suffered only a few injuries that stopped him from training. His achievements and ideas have been the main driving force behind my belief that it is possible to run more efficiently (i.e. run with lower energy consumption and fewer injuries per Km) by developing the correct technique. My article ‘The Mechanics of Efficient Running’ owes a huge amount to Pirie, though I do not agree fully with every statement that he makes.

In this post I will summarize the main points about running style made by Pirie in Chapter 2 of his book, pointing out why I agree with him when I do, and presenting the reasons for my doubt where I am sceptical. After each quote, I give the relevant page number from his book, in brackets. Further explanation of my own comments is given in my article ‘The Mechanics of Efficient Running’ (see the side bar of this blog). In a subsequent post I will summarize the points he makes in Chapter 3. Here are the style points from Chapter 2 presented in the order they occur in the book.

You must become conscious of the necessity of running properly and take steps towards developing correct technique. The best training in the world is useless unless proper technique is employed’ (p15). It is possible to run fast with poor technique but the risk of injury is high.

Shoes.. with heavily padded heel ..make correct technique impossible’ (p16). Heel padding prevents effective transfer of the energy of impact to the longitudinal arch.

over-balance forward .. you should begin to run’ (p16) Overbalancing initiates an automatic protective reflex forward swing of the leg. A small degree of overbalancing is useful for promoting lift-off from stance, but potentially dangerous as it will lead to accelerated rotation about the horizontal axis which is wasteful of energy and risks injury.

‘run .. with very light quick steps’ (p16) Rapid cadence is essential to ensure a fairly short airborne time per stride, thereby minimizing inefficient gravitational free fall (see illustrative calculations in the side bar). Rapid cadence also promotes a short time on stance, which minimizes harmful gravitational torque. Foot fall should be largely driven by gravity to prevent excessive ground reaction forces.

By keeping his knees flexed and landing on the ball of the foot on each step and with the foot beneath the body, the runner will spring along very quietly’ (p16) Slight knee flexion on landing minimizes jarring of the body and promotes storage of energy in the quadriceps. Placing the foot beneath the body prevents wasteful and damaging braking on each step. A quiet footfall indicates effective absorption of the energy of impact by muscles and ligaments. I am doubtful about the mental image evoked by the phrase ‘spring along’ as it is important to minimize vertical motion – though Pirie subsequently makes this point clear.

The runner will generate more power and cover more ground with each stride by taking advantage of the springyness and power of the muscles in the feet and forelegs and well as the thighs (p16)’ Correct foot fall will store the energy of impact in the ligaments and muscles of the foot, the calf and the quadriceps, and this can be recovered at lift off.

‘The runner’s tempo should be at least three steps per second’ (p16) Rapid cadence is essential as discussed above. Observation of elite athletes demonstrates that most employ a cadence of 180 strides per minute or higher.

Do not look down…don’t lean forwards’ (p17) Keeping the head pointing forwards and the trunk upright minimizes wasteful and potentially damaging rotation of the body around the horizontal axis, though, as pointed out above, a very small amount of lean, from the ankles rather than the waist, promotes a reflex swing of the leg, which can help lift-off from stance.

The arms should be held close to the body with the elbows bent at an acute angle (less than 90 degrees). ..The forwards and backwards strokes of the arms should form a quick sharp jabbing motion….The result is increased efficiency and greater speeds…Keep your arm action vigorous and compact’ (p17) The legs and arms naturally move with a reciprocal action to maintain balance. Reinforcing the association of a compact arm action with a compact leg action by regular drilling can be beneficial. Proprioceptive feedback from the arms to the brain is stronger than feedback from the legs. If arms and legs are well coordinated, good form might be monitored better though awareness of arm action.

The runner will no longer feel compelled to stride out – that is to throw the feet and legs forward in an exaggerated effort…. Over-striding is the most common technical affliction of runners, and one of the most dangerous.’ (p18). According to Newton’s first law of motion, no propulsive force is required to maintain a constant velocity on a horizontal surface in the absence of wind resistance. The practical consequence is that muscular effort to drive the body forwards is likely to waste energy and increase the risk of injury.

For more information about Gordon Pirie, see the Gordon Pirie Resource Centre website maintained by John Gilbody, at http://www.gordonpirie.com

 

Is my efficiency improving?

December 30, 2007

I have now done three runs since settling on the style described in my blog on Mechanics of Efficient Running posted yesterday, and I have been practising the swing drill daily since I developed it 4 days ago (amidst the ennui of Boxing Day). For each of the three runs since Christmas, I have had a very strong subjective feeling that I am running in a more relaxed manner than previously. Furthermore, I have been free of significant musculoskeletal aches and pains.

Today’s run was a 15 Km run at 4/10 effort over a path that is fairly flat apart from 5 short, sharp hills. For many months I have been using this run to gauge my fitness. So, although it is far too early to draw any firm conclusions about improvement in efficiency, I thought it would be interesting to compare today’s run with my two most recent runs over the same course under comparable conditions. Those two were on 25th November and 2nd December.

After a relatively substantial amount of training in the summer, when I ran an average of 50Km per week over a period of three months, I have decreased my running since mid-September to around 25Km per week. Therefore, I suspect that I have not increased my cardio-respiratory fitness since September. This is confirmed by my resting heart rate with reached an ‘all-time’ low of 44 beats/min in the summer, rose to 48 by the end of November and is now 51. Therefore, my subjective experience that I am running faster for a given degree of effort since adopting my new style is unlikely to be due to increased cardio-respiratory fitness.

With this in mind, I was interested to look at the performance data for today’s run compared with the comparable runs at end of November and early December. On 25th November my time for 15Km was 82 minutes and mean heart rate was 131. On 2nd December, the time was again 82 minutes and mean heart rate was 129. Today, my time was 79 minutes and mean heart rate was 130. The very similar mean heart rate recordings confirm that I had adjusted the effort to approximately the same level on all three occasions. However my time today was almost 4% faster than on the other two occasions, and was in fact the fastest I have ever recorded over this course. So my subjective experience that I am running faster at the same effort was confirmed by the data from heart rate monitor and stop watch, though a 4% improvement on a single run is unlikely to be statistically significant. This evidence is at best anecdotal.

The other important issue is musculo-skeletal stress. For the past year I have recorded musculo-skeletal aches and pains in the morning and evening every day. I rate the aches and pains on a numerical scale which I devised myself. This scale places emphasis on pre-existing problems with my right knee and also with metatarsalgia (pain in the right forefoot). My average evening score throughout the year on this numerical scale is 2.5. The score is usually a little higher after a long training run. My peak evening score so far, recorded on three separate occasions during the summer, is 6. On both 25th November and 2nd December, after the 15 Km run, the evening score was 4. Today it is 2, with contributions from very mild metatarsalgia and mild generalised muscular ache. My knee is fine, and I have no focal muscular pain. So the evidence suggests that my new running style does not exacerbate my musculoskeletal problems. So far, so good!

It would be foolish to draw too many conclusions from a single training run, but these observations do at least suggest that my new style has not caused any deterioration in my running efficiency. The important question is what will I be able to report after several months.

Wind resistance and hills

December 29, 2007

I have just been for a run on a very windy December day, so it is a good time to consider the issues of responding to wind resistance, and also hills.

Responding to wind resistance
As outlined in the article on the Mechanics of Running (see sidebar), the main driver of the leg swing is the action of lifting the ankle towards the hip at lift-off from stance. When there is wind resistance, forward propulsion is required. I believe this requires an even more forceful lift-off (and accompanying more forceful back-swing of the arm), but rather than think of a more forceful muscle action. I concentrate on an image of being towed forwards by a cable attached to the front of the pelvis below the solar plexus. The imagined cable pulls forwards. I believe that this image encourages slightly greater forward lean of the trunk (but without bending forwards at the hip), increasing destabilization and promoting a more energetic lift-off.

Climbing hills
Again the requirement is for a more energetic lift-off. When ascending a hill, I consciously lift the ankle higher and lean a little more into the hill.

The Mechanics of Efficient Running

December 29, 2007

This article is a speculative account of how to run with minimal consumption of energy and minimum risk of injury per kilometre.We will start by addressing the question of how to run at constant velocity on the flat in the absence of wind resistance, and subsequently consider how to adapt to wind resistance and hills.

The first principle is that according to Newton’s first law of motion, no propulsive force is required to maintain a constant velocity on a horizontal surface in the absence of wind resistance.The practical consequence is that muscular effort to drive the body forwards is likely to waste energy and increase the risk of injury.

However, it would be misleading to imply that no muscular effort is required.If the feet were fixed to the ground, forward momentum and gravity would combine to cause the runner to crash face-down, so it is necessary to move the legs forward alternately in such a way as to arrest the tendency to fall.In contrast to walking, while one leg is swinging forwards (‘the swing phase’), the other leg is on the ground (‘stance phase’) for only a part of the time.Thus, for a substantial portion of time the runner’s body is airborne.The effort to become airborne and the impact with the ground at foot strike, create risk of injury.The art of efficient running entails swinging the leg forward in a way that uses minimum energy with minimal risk of injury.

To understand how this is done requires an understanding of what muscular actions are required and what muscular actions are to be avoided.Learning how to do it requires acquisition of the correct sequence of movements, which can be facilitated by use of a specific drill (the swing drill, described in a separate article), and subsequent practice of this sequence of movement until it becomes habitual.In my experience, the sequence can be acquired with less than an hour of practice. Warm-up for each running session should begin with the swing drill and a period of relaxed running focussing on technique.Once the sequence of actions is habitual, execution of the procedure does not require conscious planning of each muscle action, but rather, the use of simple imagery to evoke the learned sequence.

General principles

Certain principles of physics and physiology can be invoked to determine the optimum sequence of actions. The guiding principle is that acceleration or deceleration of the body’s centre of gravity (COG) relative to the ground should be kept to a minimum, because acceleration and deceleration require energy and also have potential for injury. Furthermore, acceleration of one body part relative to another should also be used a sparingly. The following specific principles follow:

1)      To minimise braking, the period of time for which the foot is on the ground in front of the COG should be minimised.  However, any change in the speed of rotations of the body around the pivot point where the foot contact ground, and also any change in horizontal velocity between footfall and mid-stance (when the COG is immediately above the point of support) must balance the oppositely directed changes that occur between mid-stance and lift-off from stance (in order to  satisfy the laws of conservation of angular momentum and conservation of linear momentum). Therefore if the time on stance with the foot in front of the COG is short, the time on stance between mid-stance and lift-off must also be short.  Thus total time on stance will be short.  To achieve this a relatively large push against the ground is required.   A large push against the ground generates a large ground reaction force (according to Newton’s third law of motion.) and some of the implications of this are discussd in point 4 below.

2)      Vertical motion of the COG should be minimized as downwards motion increases force on the ground and upwards motion requires energy. Nonetheless, during the airborne period, the body is unsupported and must fall. However, because acceleration under the influence of gravity causes a steady build up a speed, the body will fall less during a series of several short airborne periods than during a series of fewer longer airborne periods of the same total duration (See the article on calculations for the mathematical demonstration of this). Therefore, to minimize free fall under the influence of gravity, the airborne period should be relatively short.  However there is a limit as to how short it can be.  The leg must swing forward from its downwards and rearward orientation at lift off form stance to a position in front of the COG  at footfall.  The time available for the swing is the sum of one stance period (while the other foot is on the ground)and two airborne periods.  The swing is a forced pendular action.  Although the duration of the swing can be decreased a little my various strategies such as ensuring the knee is flexed in mid-swing so the pendulum arm is short, even very fast runners can achieve only a modest decrease in swing time compared to less talented runners.  As we have seen, it is desirable to minimise time on stance in order to minimise braking, but the need for adequate time to complete the swing sets a lower limit on the sum of  stance  and two airborne periods, so there is a limit as to how much it is possible to reduce airborne time.

3) If both airborne time stance time should be as short as possible within the constraint of allowing adequate time for the swing, then cadence must be high. Observation of elite runners indicates that it should be at least 180 steps per minutes (i.e. 90 full cycles of the gait cycle per minute)

4) According to Newton’s third law (action and reaction are equal and opposite) the vertical component of ground reaction force (GRF) must be equal and opposite to the downwards force exerted by the foot on the ground. The average value of the vertical component of GRF averaged over the full gait cycle must equal the body weight. As GRF is only exerted during stance, the average value during stance is the body weight multiplied by the ratio of total duration of the cycle to the time on stance. Thus if time on stance is half of the total gait cycle, the average GRF during stance will be twice the body weight. Peak GRF during stance might be considerably higher than this, as the load is not distributed as uniformly over the stance period. However it is desirable that the rise and fall of the load during stance should follow a smooth curve that minimise the likelihood of sharp peaks.  This is probably best achieved by landing with the ankle almost neutral (or with a very slight degree of plantar flexion) so that weight is taken on the mid-foot; then rapidly transferred to the first metatarsal where the energy can be temporarily absorbed by some flattening of the longitudinal arch by a slight roll of the foot towards the inside edge (mild pronation). Some of the energy is stored in the stretched Achilles tendon, whose role includes sustaining the arch. This stretch can only be maintained if the calf muscle is contracted. Finally, the joints of the foot are stiffened by a slight roll laterally (supination) to promote recovery of energy by elastic recoil at lift off. The time on stance must be long enough to allow the transfer of energy between the structures of the foot, but in view of the fact that calf muscle contraction is required to maintain the stored energy, too long on stance will lead to exhaustion of the calf. Thus, consideration of foot dynamics also indicates the need for a relatively short time on stance to optimise the capture of elastic energy. (But if airborne time is much greater than time on stance, GRF during stance will necessarily be high to ensure that average GRF over the entire cycle is equal to weight)

The components of the gait cycle

As outlined above, during the full gait cycle, each foot is engaged in a stance phase and a swing phase. During the swing phase, the foot must be lifted, moved forwards and allowed to drop back to the ground, moving backwards relative to the COG at the point of foot fall. Thus, the foot follows a quadrilateral path, rounded at the corners as each stage of the cycle grades in to the next one. The four segments of the path are:

1) Base position

In the base position the foot is on stance: The COG moves forwards over the foot. According to principle 1) time on stance should be short.  Nonetheless some braking is inevitable as the leg is pressed against the ground while angled forward and downwards prior to mid-stance.  Thus some forward momentum is lost.  In early stance, the body continues to descend but at a deceasing rate as the tendons of the large muscles of the hip and thigh absorb the energy of impact (as described in greater detail below in the description of footfall).  In addition the processes of foot pronation and supination absorb, store and redistribute some of the energy of impact. After mid-stance the release of captured elastic energy initiates the forward and upward propulsion of the body, to compensate for the braking in early stance and to recover the height lost during the fall after mid-flight.   Also, in mid and late stance the calf muscles (especially gastrocnemius) contract to assist in the forward and upward propulsion.

2) Lift -off

At lift off from stance, the ankle is lifted towards the hip. This action is initiated by the recoil of Achilles tendon and assisted by an adjustment in the relative tension in hamstrings and quadriceps that allows the knee to flex.  Because the hamstrings cross both hip and knee joint, unopposed hamstring contraction would also produce undesirable hip extension which would move the leg backwards behind the line from lift-off point to hip. Observation of elite athletes like Haile Gebrselassie suggests that the ankle should in fact curve upwards in a path that arches behind the direct line towards the hip.  However, the main goal of the swing phase is repositioning the foot in front of the COG in time for the next footfall, and it is probably desirable to initial hip flexion as soon as the foot lifts from the ground.   The hip flexion is largely automatic, promoted by recoil of the hip flexors that had been subject to stretching as the leg extended backwards in late stance.   It is helpful to envisage a rapid pulling of the foot from the ground, though of course task of propelling the body upwards had been achieved by the push against that ground that had been maximal in mid-stance.

3) Leg swing

The swinging leg is propelled forwards by flexion of the hip, but the pendular action cannot be forced.  In late swing, the hip extensors arrest the swing and the knee extensor partially straightening the knee. However, the knee should not extend fully but remain slightly flexed so that it can help absorb impact at foot fall.

4) Foot fall

The foot falls to the ground as the hip swings back towards the neutral position largely under the action of gravity, but with assistance from the hip extensors, with the knee remaining slightly flexed.  Except perhaps when sprinting, it is best to avoid consciously pushing the foot to the ground, as this is likely to result in a mistimed push and might actually delay the subsequent lift-off form stance.   Although deliberate muscle action is not required, a strong automatic stabilizing contraction of the quadriceps must occur to prevent the knee collapsing on impact, while contraction of the hip, flexors occurs to prevent the torso rotating forwards. Because the hip swings back almost to the neutral position during the fall, the point of impact is only slightly in front of the COG, thereby minimizing any braking effect. The quadriceps absorbs a large amount of energy at impact, some of which will be recovered by elastic recoil to assist in raising the body to recover height lost during freefall.  The contraction of the hip extensors in early stance promote the capture of elastic energy in the tendons of the hamstrings and also the iliotibial band (ITB), which is tensioned  by the gluteus maximus and tensor fascia lata muscles.  The subsequent release of elastic energy from the tendons of the quadriceps hamstrings and ITB around mid-stance provides the main propulsive force that will accelerate the body forwards and upwards in late stance.

The ‘swing drill’ (see separate article) entails practice of the three segments of the swing: ankle lift, leg swing and foot fall, while the body is stationary, supported by the opposite leg.

Torso
Upper body orientation and movement should be used to facilitate the leg movements. The torso should be held in an almost upright orientation, with the pelvis held level and not allowed to drop back.  in a manner that would compromose the backward extesnion of the hip in late stance. The shoulders should be drawn slightly back and rest downwards in a relaxed state. This orientation of the body facilitates a relaxed foot fall to the correct position under the COG.

Arm swing
The arms swing in a minimal arc in a reciprocal action to the leg on the same side. As the ankle is lifted towards the hip the arm moves back moderately forcefully, reflecting the sharp, compact movement of the ankle towards the hip. Then the arm swings forward largely under the influence of gravity, but not in a floppy state, while the leg swings forwards and the foot falls to the ground. If a compact arm movement is practiced during the swing drill, the brain will readily associate the compact arm swing with a compact leg action. Because proprioceptive feedback from the upper limb is more strongly represented in the brain than that from the leg, good form can be monitored more easily if arm and leg are coordinated.

All unnecessary muscle action should be avoided.However in addition to the actions described above there are several other important actions.Reflex contraction of the hip abductors minimizes pelvic tilt and dropping of the hip on the unsupported side.Footfall with slightly flexed knee and the impact absorbing foot action described above would be expected to minimise abrupt loading of the hip abductors while also protecting the knee joint and ankle joint and minimising sharp localized forces on the bones of the foot.

It should be emphasized that this description of efficient running is based in observation a few elite athletes and an attempt to apply the principles of physiology, anatomy and physics as described above, but has only been tested by the author himself.It has not been subjected to any form of controlled trial and hence must be regarded as a speculative proposal rather than a proven method of safe, efficient running.

 This article was edited in April 2012 to make it more consistent with my posts in the months Jan to April 2012

Acknowledgments

Gordon Pirie, gritty and thoughtful elite athlete, former 5000m and 3000m world record holder and source of inspiration, whose thinking about running style has shaped my own;

Dr Nicholas Romanov, developer of the Pose technique of running, who has emphasised that running style can be improved by thoughtful application of principles;

Cable_Tow, sports medicine specialist and generous-spirited guru on the Fetcheveryone website;

nrg-b: Pose coach with a delightful sense of humour;

Jeremy Huffman, elite athlete and Pose coach;

Jack Becker, generous spirited Pose coach;

Jack Cady, developer of Stride Mechanics;

Haile Gebrselassie, elite athlete, marathon world record holder, and model for efficient running;

Fetch, founder of an amazing website for runners and pace-setter in one of the few races that I have ever won;

Danny Dreyer, developer of Chi running;

F. Matthias Alexander (1869-1955) who showed how changing one’s thinking can re-direct posture and movement, and honed the concept of listening to your body.

Introduction

December 29, 2007

I am a sixty-plus year old runner who competed intermittently in teenage and young adult life, but then stopped running because hill-walking, mountaineering and all of life’s other activities got in the way. As the years went by, life’s other activities crowded out first the mountaineering and then the hill walking so by the time I reached sixty, I was becoming alarmingly unfit. In the hope of slowing the rate of decline I took up running again.

By my age I have become very aware of the vulnerability of the body to injury – though in fact it is not just the older runner who faces the risk of injury. Many younger runners also spend a frustrating amount of time side-lined by injury, and the ability to sustain heavy and consistent training without injury is a major factor in the success of elite athletes.

So I began looking into the question of how to run efficiently. By efficient running I mean running in a style that maximizes performance by minimizing the risk of injury and minimizing the energy consumption at a given speed.

There are three ways of determining the optimum technique:

1) Anecdotal evidence obtained by observing individuals, including elite athletes and also ourselves. A great source – but how do we know we are not focussing on an individual’s idiosyncrasies.

2) Formal scientific studies in which groups who use different techniques are compared and results are tested to assess the statistical significance of any benefit or harm of one technique compared with another. However, any conclusion only applies for the precise aspect of technique studied, and to runners at a similar level of fitness and physical constitution as the people in the study.

3) Developing techniques based on understanding the underlying physics, physiology and anatomy. In the end, a good technique must be consistent with the principles of physics, physiology and anatomy, but the body is complex and any theoretical approach might overlook some crucial factor, so eventually a practical test is required.

Because none of these approaches alone is likely to give us the complete answer, this blog will try to assemble evidence gleaned by all three approaches, and assign special value to the ideas that are supported by all three.

The format I plan to follow in this blog is to post my thoughts on various aspects of efficient running, starting with a detailed speculation about the mechanics of running. That post and others that might be of enduring interest will also be saved as updateable articles accessed via the side bar of this site. The posts and articles are not intended to be authoritative because I am not an expert. Rather, they are intended to be a stimulus for further thought and discussion. I would hope to be able to update the main articles from time to time as people point out the errors of my early efforts, and as more information emerges

Any reader should be aware of limitations of this site and should seek professional advice before introducing changes in their running style.