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Lee Saxby's Wisdom of Coaching Blog

Running Technique and Physical Education

‘Everything’s already been said, but since nobody was listening, we have to start again.’

Andre Gide

The Fundamentals of Body Mechanics & Conditioning (an illustrated teaching manual) by Mabel Lee and Miriam. M Wagner  (1949) provides an insight into the philosophy and purpose of physical education in the schools of Europe and the US circa 1920s -1940s. Society was beginning to recognise that ‘progress’ had a price, namely the increasing number of deaths and disabilities attributed to the ‘diseases of affluence’ and the sedentary lifestyles of the industrialised, white-collar workforce. In an attempt to prevent the predicted decline of the physical, psychological and social health of future generations a new breed of PE teacher began to emerge who could teach the fundamentals of postural education, corrective gymnastics and conditioning exercises as well as the traditional sports and games education. Included in this ‘new’ approach to physical education was the belief that standing, walking and running were fundamental movement skills that needed to be taught and corrected at a young age to improve the quality of every day living in adult life.

This video circa 1925 captures the essence of this ‘new’ approach to Physical Education

Are your feet NORMAL or NATURAL?

normal natural definitions

As the owner of a footwear retail store licensing BTR’s NATURAL Feet education and an active BTR Running Technique Coach I have analyzed plantar pressures for 100s of clients over the last 3 years.

A frequent customer statement, prior to their BTR Assessment, is that they have low arches or flat feet, which is often backed up by statements from their physiotherapist/doctor with the unsubstantiated belief that low longitudinal arches are bad.

However, when they stand on the plantar pressure plate I often see what BTR classify as a NORMAL FOOT.

naturalvnormal plantar pressures

The BTR foot classification definitions:

NATURAL = big toe and a whole plantar surface area (natural longitudinal arch)

NORMAL = no big toe function and/or no connection between fore-foot and rear-foot (high longitudinal arch)

The low incidence of flat feet in my client records was highlighted to me recently when I searched for an example and I struggled to find cases from 300+ records.

table naturalvnormal

How to check if your feet are NATURAL or NORMAL if you don’t have access to a plantar pressure plate, wet your feet and check your footprints.

Future posts in this series:

  • how to rehabilitate your feet from NORMAL to NATURAL
  • Why low arches are not a bad thing

Harvard research supports BTR coaching wisdom

Professor Dan Lieberman’s latest publication supports the Born to Run coaching philosophy

Lee Saxby’s Born to Run coaching system emphasizes the detrimental effects of over stride both on injury risk and on running economy. Lee made the connection between over stride and running rhythm / stride frequency a long time ago and subsequently made rhythm the second priority in his ‘posture-rhythm-relaxation’ movement mantra.

About the study

The study examined the relationships between stride frequency, over stride, braking forces, peak-impact forces and loading rates, and the energy cost of running at a fixed speed (3.0 m/s) in 14 experienced runners. Participants were asked to run on a treadmill with stride frequencies of 75, 80, 85, 90 and 95 strides/min. Ground-reaction forces, lower-extremity joint angles and the metabolic cost of running were measured.

What the study showed

  • For every increase of 5 strides/min, the energy cost of swinging the leg forwards (estimated from maximum-hip-flexion moment) increased by 5.8%, and over stride (landing position of the foot relative to the hip) decreased by 5.9%
  • Larger over stride associated with higher braking (backwards oriented) forces and with higher peak-vertical-ground-reaction forces
  • Metabolically-optimal (least costly) stride frequency was around 85-90 strides/min (170-180 steps/min)

Take home message

Increased stride frequency (within optimal range) decreases over stride and, in turn, decreases braking force and peak-vertical-impact force that are related to injury risk. In addition to reduced braking and impact forces, stride frequency within the BTR recommended range decreases the metabolic cost of running.

References

Lieberman, D.E., Warrener, A.G., Wang, J. and Castillo, E.R. (2015). Effects of stride frequency and foot position at landing on braking force, hip torque, impact peak force and the metabolic cost of running in humans. Journal of Experimental Biology, 218, 3406-3414.

Paper available HERE.

The Brain’s view of anatomy

‘Never judge a book by it’s cover’

anon

animal homunculi

Most movement coaches use anatomical frames of reference (i.e. muscle groups) when coaching. The problem with this approach is that the coach’s eyes have a very different view of the world to the client’s brain! The brain is the primary organ of the movement system (see sea squirt) and it’s job is to process the information received from the visual, vestibular and somatosensory systems and construct an appropriate motor response. The relative importance of each sensory organ to the movement system of different species and their perception of the world becomes very apparent when their somatosensory cortex is displayed as a sensory ‘body map’ or  ‘homunculus’.

Screen Shot 2015-11-07 at 13.07.24The human somatosensory homunculus is typical of most primates who require sensitive, dextrous hands and feet for climbing, leaping, feeding and grooming (note the exceptionally large representation of the lips and tongue due to the human necessity for speech)* Any reduction in sensory input from the major sensory organs dramatically reduces the accuracy of motor output (see pendulums and springs) leading to inappropriate biomechanics, tissue damage and pain. Understanding that motor output problems (lack of balance, strength and flexibility) are symptomatic of sensory input problems (a sensory homunculus-environment mismatch) helps define ‘mind-body exercise’ and the organising principles of movement therapy.

* this probably explains the observation that some clients need to talk incessantly during coaching sessions.

 

BTR-21century-homunculus

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reference:

Penfield W, Rasmussen T. The cerebral cortex of man. New York: The Macmillan Company; 1950.

The Curious Case of F. W. Knowles (the scientific power of an N of 1 trial)

In 1948 F. W. Knowles, a Lecturer in Anatomy at the University of Queensland in Australia, conducted an experiment on the assumption that modern shoes distort the feet and that wearing “naturally” shaped shoes may permit some reversal of the distortion.

knowles-fig1knowles-fig4Knowles had shoes made with a natural “substantially triangular plantar aspect” based on the profile in Fig I left.

A 37-year-old volunteer (probably Mr Knowles himself) wore the shoes, shown in Fig IV right, for three and a half years with no other treatments, only walking (time on feet in the gravitational vector).

Figures V and VII below shows the changes in the foot structure from August 1948 to April 1952. Note the improvement in the hallux of the right foot.

knowles-fig5-7

Knowles summarized his paper with the following:

“it is suggested that the medical profession might encourage the wearing of shoes of the type described as a relief from conventional footwear, in an attempt to control the incidence of the discomfort and deformities and other conditions consequent upon the continuous wearing of badly designed footwear”.

Refer to our Anatomically Intelligent Footwear criteria when choosing shoes for you and your family.

Reference:

F. W. Knowles. Effects of Shoes on Foot Form: An Anatomical Experiment. The Medical Journal of Australia April 25, 1953

 

Is the human foot the ultimate fashion victim

“Seest thou not what a deformed thief this fashion is?”

‘Much Ado About Nothing’, William Shakespeare

A 19th century advertisement for the Clark’s (UK) ‘Hygienic line’ a range of shoes which followed the natural shape and line of the foot.

clarks-hygienicIn 1881 William Henry Flower published Fashion in Deformity: As Illustrated in the Customs of Barbarous and Civilised Races. Here are a selection of the illustrations:

Flower’s book is available HERE

More than a century later only a few shoe manufacturers create footwear conforming to our Anatomically Intelligent Footwear criteria.

Anatomically Intelligent Footwear

Continuing from our Intelligent Design post where we discussed the plastic foot. The BTR footwear manifesto.

Non-negotiable features

Choose footwear that:

  1. has a wide toe box allowing natural big toe alignment
  2. is flat, zero-drop with no arch support
  3. has no toe-spring

BTR-foot-in-shoe

 

Trade-off features

Choose footwear which provides maximum plantar sensory feedback (see post on the influence of shoes) with trade-offs against:

  • flexibility
  • traction
  • protection (thermal and puncture)

when appropriate for terrain or use.

btr-scales

The science of falling

Who has seen the wind? Neither you nor I, but when the trees bow down their heads, the wind is passing by”. (Rossetti, 1915).

The Science of Falling: How a virtual pivot point explains constant-velocity running using gravitational torque. 

In part 3 of the series of posts on the extensor paradox, it was concluded that gravity creates a turning force or torque on the center of mass of a runner about the supporting foot, when the former passes in front of the latter. It was also concluded that this gravitational torque provides the motive force in running. This theory is in agreement with kinetic and EMG data from previously published research (Mann et al., 1986; Rodano, 1987; McClay et al., 1990), whereas the prevailing theory that runners actively ‘push’ into the ground is at odds with both – hence the so-called extensor paradox that is not a paradox at all.

The theory that gravity provides the motive force in running is not new (Morton, 1935; Perry, 1992; Romanov and Fletcher, 2007). However, the mechanism used to explain the action of gravitational torque in these publications struggle to explain constant-velocity running, and instead would lead to constant acceleration, closer to what happens when sprinters initially leave the blocks, and as depicted in part three of the extensor paradox post. A recent attempt to explain gravitational torque in locomotion, and to experimentally demonstrate it’s effectiveness in reducing the energy cost of running and walking (Kanstad and Kononoff, 2015), suffers from fatal methodological issues and reporting bias. Constant-velocity running, as well as acceleration and deceleration using gravitational torque can, however, be perfectly explained by the virtual pivot point model (VPP) (Maus et al., 2010). This model also explains the stability observed in what ought to be a very unstable gait.

Unstable bipeds and running robots

The VPP model has its origins in engineering and was borne out of the seemingly insurmountable problem of preventing an inherently-unstable-bipedal robot locomote without falling over. Keeping a heavy torso upright over a long leg with a small base of support is a complex task amidst the varied forces acting on it during the running cycle. It is no less a challenge for humans, yet healthy humans rarely fall over. The solution lies in aligning the ground reaction force vector with a fixed, though virtual axis high in the torso, above the center of mass, at every stage of the stance phase. This is the virtual pivot point model.

The VPP and constant-velocity running

 

Science of falling VPP_corection hq_muscles

The image above depicts a runner at initial ground contact (left), mid stance (middle), and terminal stance (right). The graphs below show the vertical ground reaction force and torque about the hip joint respectively. At initial ground contact, the GRF vector is angled backwards and up through the VPP and in front of the center of mass (producing a slight braking effect). The perpendicular distance between the GRF vector and the hip joint is shown as D. This discrepancy creates a hip flexion torque and a forward pitching of the torso that must be controlled by hip extensors. The shaded region about the rear of the hip and lower back illustrate the EMG response of the hip extensors whose primary purpose (see teleology post) is to control the forward pitch of the torso in running, hence their extensive development in humans but not non-running apes and chimps (Lieberman et al., 2006). This slight forward pitch of the torso is evident in slow-motion observations of every elite runner and was leveled as a criticism of the ‘Pose’ conception of running (Brodie et al., 2007).  At mid stance, the GRF vector is vertically-aligned with the hip, center of mass and VPP. The EMG activity shown in the legs here is simply to resist the squash of gravity and the opposing GRF and to aid storage of energy in the major tendons of the leg. Immediately after mid stance, the extensor muscles switch off and the runner’s center of mass falls forward using gravitational torque at the same time as the leg spring passively recoils providing the upward motion seen in the trajectory of the center of mass. This time, the GRF is aligned forwards and up through the VPP and behind the CoM and hip, creating acceleration, and a hip extension torque that activates hip and trunk flexor muscles and begins the recovery of the support leg. There is also a resulting backwards pitch of the torso, which again, can be seen in slow-motion footage of all good runners. The figure shows how the GRF vectors at initial contact and terminal stance are exactly opposite each other creating equal but opposite hip flexion and extension torques and a constant velocity i.e. the slight braking effect is counteracted by the acceleration effect provided by gravitational torque after mid stance. Acceleration and deceleration result from mismatches in the hip flexion and extension torques.

The VPP model explains and accounts for kinetic and kinematic observations of human and animal runners and how they work with gravity, to save energy, as predicted by the biological imperative. Predictions of the theory have been supported by observations in rigorously-designed studies. A theory that explains and account for all observations is of course superior to one that does not. The current ‘runners push’ theory, and past and recent ‘gravitational torque’ theories constitute the latter.

References:

Brodie, M., Walmsley, A., and Page, W. (2007). Coments on “Runners do not push off but fall forward via a gravitational torque” (Vol. 6, pp. 434-452). Sports Biomechanics, 7(3), 403-405.

Kanstad, S.V. and Kononoff, A. (2015). Gravity-driven horizontal locomotion: theory and experiment. Proceedings of the Royal Society A, 471(20150287), 2-11.

Lieberman, D.E., Raichlen, D.A. and Pontzer, H. (2006). The human gluteus maximus and its role in running. Journal of Experimental Biology, 209, 2143-2155.

Mann, R.A., Moran, G.T. and  Dougherty, S.E. (1986). Comparative electromyography of the lower extremity in jogging, running and sprinting. The American Journal of Sports Medicine. 14(6), 501-510.

Maus, H.M., Lipfert, S.W., Gross, M., Rimmel, J and Seyfarth, A. (2010). Upright human gait did not provide a major mechanical challenge for our ancestors. Nature Communications, 1(70), 1-6.

McClay, I.S., Lake, M.J. and Cavanagh, P.R. (1990). Muscle activity in running. In P.R. Cavanagh (Ed.), Biomechanics of Distance Running (pp 165-186). Champaign, Illinois: Human Kinetics.

Morton, D.J. (1935). The Human Foot: its evolution, physiology and functional disorders. New York: Columbia University Press.

Perry, J. (1992). Gait Analysis: Normal and Pathological Function. Thorofare, New Jersey: SLACK Inc.

Rodano, R. (1987). Evaluation of movement in sport by means of vectograms. International Symposium on Biomechanics in Sports, 506-522.

Romanov, N and Fletcher, G. (2007). Runners do not push off the ground but fall forwards via a gravitational torque. Sports Biomechanics, 6(3), 434-452.

Rossetti, C.G. (1915). Sing-song: a nursery rhyme book. London: MacMillan and Co.

The influence of shoes on pendulums and springs

Continuing our series on Pendulums and Springs.

1. The skill of creating pendulums and springs

2. Changing from a pendulum to a spring

The decision by the sensorimotor system to select a pendulum or spring strategy (kinematics) is a subconscious one based on the sensory feedback provided by the proprioceptive system regarding the forces acting on the body (kinetics). Simple ’force-time’ graphs (see below) are useful visual aids when attempting to explain the different kinematic adaptations observed in runners when running at different speeds, on different substrates and in shod-unshod conditions.

force-time-curve-fig1and2

Fig 1 is the ‘classic’ barefoot heel-strike on a hard surface with the relevant kinetic information labeled.

Fig 2 is the ‘classic’ barefoot heel-strike on a hard surface with an arbitrary ‘signal to transition’ line added. This line can be considered the ‘pendulum threshold’ ie the forces acting on the body are no longer suitable for a ‘pendulum strategy’ and a ‘spring strategy’ should be adopted (fig 3).

force-time-curve-fig3and4

The ‘decision’ to adopt a ‘spring strategy’ is a risk-benefit analysis of the biomechanical and metabolic implications of changing from a pendulum to a spring (see teleology post). The ‘wisdom’ of this decision is based on accurate sensory feedback on the kinetic situation. The physiological ‘cost of cushioning’ must be weighed up against the biomechanical risk of injury. If the sensory feedback is dampened or delayed the ‘signal to transition’ is no longer received and a pendulum strategy will be maintained inappropriately (see skill of creating pendulums and springs). The major cause of ‘sensory dampening’ is a cushioned shoe (fig 4).

The benefits and risks of changing from a pendulum to a spring

Following our post the skills of creating pendulums and springs

BENEFITS

The Science Suggests

  • Injury Prevention: By changing technique we can change joint torques and loading rates which are the two biggest risk factors for injury.
  • Increased Efficiency: By changing technique we can change the ratio of muscle action to elasticity which influences efficiency.
  • Increased Speed: By changing joint torques, loading rates and the ratio of muscle action to elasticity we can improve how we control and direct the Ground Reaction Force experienced by the body which is the ultimate determinant of speed.

The Observations and Anecdotes

Elite Runners, habitually-barefoot populations, and uninjured- shod runners – display similar spinal alignment, foot contact times, cadence and hip mechanics when running.

RISKS

The individual: The postural and structural stability of the individual and their physiological health will determine the benefit/risk ratio of changing running technique. This is where a running specific screening process involving video analysis, movement skill milestones and educated coaching comes into the equation and is the reason Lee Saxby’s BTR Coaching Methodology exists.

BTR-good-bad-ugly-technique

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