Monday, April 30, 2012

Forward lean or not forward lean? Pirie, Dryer or both?

Gordon Pirie's book (below) is very adamant about "not leaning forwards" but that was 40 years prior to Gebreselassie. Pirie was clearly well ahead of his time and there are some great insights in his ideas - but when held to comparison with Danny Dreyer's "ChiRunning" there are some gaping holes exposed.

Below... Haile Gebreselassie in the 1998 Helsinki 5000m - setting a world record.  He is the one at the back - the two in front are pacemakers. He clearly has a midfoot strike  - not a forefoot strike and all three of them have forward lean. Exactly as described in ChiRunning. 

Pirie's book gets seriously into technique on pages 17 to 20.

It's interesting to compare ChiRunning and Pirie to see both the differences and similarities.

First of all what do they have clearly in common?
  1. The foot lands directly beneath the body
  2. Heel striking is avoided
  3. Both end up with whole foot on the ground
  4. Falling forwards is implicit
  5. High cadence
  6. Good posture essential
  7. Knees stay slightly flexed
  8. Arms play an important role, bent at 90° and not crossing the center-line of the body
  9. Constant focus and attention is required and developed
Where are the clear differences? (Colour red indicates where one is probably more accurate)
  1. Level or Ascending terrain: Pirie - forefoot strike, Dryer - mid-foot strike
  2. Alignment: Pirie- one foot directly in front of the other, Dryer - each foot either side of a thin central line.
  3. Lower leg: Pirie pushes off with foot, ankle and calf, Dryer - picks up feet instead - no push off.
  4. Lean: Pirie is adamant that forward lean is to be avoided, Dryer - makes forward lean central to technique
  5. Arms: Pirie emphasizes sharp brake of forward swing, Dryer emphasizes rear swing (Upward swing when climbing)
  6. Energy Recovery: Pirie mentions "springing", Dryer shows role of tendons and ligaments in core for energy recovery
  7. Propulsion: Pirie - proper use of arms and legs, Dryer - gravity is source of propulsion
  8. Upper body: Pirie - keep it immobile, Dryer - allow the spine to twist up to the T12 vertebrae
  9. Core: Pirie - no mention, Dryer - use of core central with transfer of dominant muscle use here
  10. Stride: Pirie - faster speed gives longer stride, Dryer - stride lengthened behind with pelvic rotation and spine involved - gives higher speed
  11. Relaxation: Pirie - no mention, Dryer - source of speed and efficiency
  12. Minimalism: Pirie -  advocates minimalist shoes, Dryer - standard running shoes
  13. Walking: Pirie - straight leg and heel strike, bad for running, Dryer - mid-foot strike, same mechanics as running (ChiWalking)
Dreyer's logic relating speed directly to stride length (gearing) appears to be faulty. Pirie points out that by using the power of the arms and legs coordinated together it's by virtue of a stronger spring that you spend more time in the air and so achieve a longer stride. However Dreyer makes a more conscious use of relaxation and the forward vector component of gravity during a supported fall. Dreyer states that to increase speed the cadence is kept constant and the stride lengthened - but without a spring there is a limit to how much the stride can be extended. Altogether it's impossible to go fast with a fixed cadence and limited stride length. Perhaps just picking up the feet higher and leaning more generates greater speed - which then lengthens the distance covered in the air - but without a spring this is difficult to imagine. Dreyer in general has keyed into the correct mechanics but then if you add the active power of the upper body through the arms as advocated by Pirie you get a spring even without using the lower legs/calves etc. With the arms and upper body ahead of the feet on the ground then the strong acceleration and deceleration of the arms adds power to both give a spring and to recover the opposite leg. You can actually feel the power in your hands like you are pulling on a rope and then  pushing against a resistance as the force transmits through the body in a very connected way. Pirie is clearly wrong about not leaning forwards and this is why he is unconscious of how to exploit gravity intelligently.  Ironically his only given exercise for beginners is to stand on the tip toes and fall forwards! Pirie's observation that using the arms powerfully and coordinated with the legs removes the need to over-reach ahead with the legs is amazingly good. 

One interesting aspect of using gravity for propulsion is that this impulse can only be accessed when in contact with the ground and toppling forwards - otherwise gravity is generating a purely vertical motion. This fact would also go some way towards explaining why good runners use a high cadence. Normally the high cadence is explained in terms of the elasticity of tendons - the fact that they only retain elastic force for a small fraction of a second. The more frequently you can have a brief contact with the ground the more frequently you can obtain a forward impulse from gravity. Momentum, forward lean and foot placement will all then interact in interesting ways. Greater momentum will cause the centre of mass to move ahead of the support foot more rapidly - causing increased speed through a positive feedback loop. That's why relaxation will generate speed - it's removing resistance. Tilting the entire body forwards will place the emphasis more directly on gravity itself than momentum. The more efficient you are at maintaining momentum the less you should need to exaggerate the forwards tilt - which is probably why Gebreselassie is slightly less tilted forwards than his pacemakers. Balancing the downwards impulse of gravity through a strong hip/leg extension is hard work and this is probably why the pacemakers tire out more rapidly. Using the forefoot-strike is going to guarantee a good shock absorption through all the 100+ muscles, tendons and ligaments in the foot and the big calf muscles. However, this is probably not necessary or efficient unless sprinting with the centre of mass well ahead of the support foot and working hard to balance the downward vector of gravity (sprinters are powerful!). If enough shock absorption is achieved with a mid-foot strike then less of the energy from forwards momentum is absorbed and then re-transmitted by the foot/calf mechanism and will be retained directly in momentum. This could also go some way to explaining why Gebreselassie is more efficient in maintaining momentum and than his pacemakers who are using forefoot strikes. The trick would seem to lie in getting the right mix of each of those parameters for the task in hand. 

From a personal viewpoint I'm curious about how efficient running might link to "resonance" and how it might relate to a wave-like motion. The thing about resonance is that it only takes an accurately timed small impulse to create a very powerful effect. Nicolai Tesla (inventor of exploitable AC current, induction electric motor, radio, and wireless power transmission) reckoned he could split the Earth in two with resonance:

What follows is part of an article and interview with Tesla by Allan L. Benson,
published in The World To-Day, Vol. XXI, No. 8, February 1912, Page 1763-1767.

The principle embodied in [experiments with resonance] interested Tesla, and he
determined to try it upon a larger scale.  He ordered from a steel company a
steel link, two feet long and two inches thick.  He was careful to specify that
the steel should be of the best quality.  As a matter of fact, the link was
strong enough to bear a weight of hundreds of tons.

Tesla fastened to this link an electric vibrator, no larger than an alarm-
clock, but so constructed that the frequency of the vibrations could be altered
at will.  He set the vibrator to going and then began to vary the vibrations
for the purpose of getting the vibrator in "tune" with the link.  For a long
time, nothing happened -- the vibrations of the link and of the machine did not
chance to coincide. But at last he got them together, the great steel link
began to tremble, increased its trembling until it dilated and contracted like
a beating heart -- and finally broke!

Sledge hammers could not have done it; crowbars could not have done it, but a
fusillade of taps, no one of which would have harmed a baby, did it.

Tesla was pleased.  He had learned something.  He wanted to learn more.  He put
his little vibrator in his coat pocket and went out to hunt a half-erected
steel building.  Down in the Wall Street district, he found one -- ten stories
of steel framework without a brick or a stone laid around it.  He clamped his
vibrator to one of the beams, and fussed with the adjustment until he got it.

"In a few minutes", he said, "I could feel the beam trembling. Gradually, the
trembling increased in intensity and extended throughout the whole great mass
of steel.  Finally, the structure began to creak and weave, and the steel-
workers came to the ground panic-stricken, believing that there had been an
earthquake.  Rumors spread that the building was about to fall, and the police
reserves were called out.  Before anything serious happened, I took off the
vibrator, put it in my pocket and went away.  But if I had kept on ten minutes
more, I could have laid that building flat in the street. And, with the same
vibrator, I could drop Brooklyn Bridge into the East River in less than an

Tesla says that he can split the earth in the same way -- split it as a boy
would split an apple -- and forever end the career of man.

This seems like quite a large order -- but see what he says about it.

"The vibrations of the earth," said he, "have a periodicity of approximately
one hour and forty-nine minutes.  That is to say, if I strike the earth this
instant, a wave of contraction goes through it that will come back in one hour
and forty-nine minutes in the form of expansion.  As a matter of fact, the
earth, like everything else, is in a constant state of vibration.  It is
constantly contracting and expanding.

"Now, suppose that at the precise moment when it begins to contract, I explode
a ton of dynamite.  That accelerates the contraction and, in one hour and
forty-nine minutes, there comes an equally accelerated wave of expansion.  When
the wave of expansion ebbs, suppose I explode another ton of dynamite, thus
further increasing the wave of contraction.  And, suppose this performance be
repeated, time after time.  Is there any doubt as to what would happen?  There
is no doubt in my mind.  The earth would be split in two.  For the first time
in man's history, he has the knowledge with which he may interfere with cosmic

I asked Tesla how long he thought it would take him to split the earth in two.
He said he didn't know.  Months might be required; perhaps a year or two.

"But in a few weeks," he said, "I could set the earth's crust into such a state
of vibration that it would rise and fall hundreds of feet, throwing rivers out
of their beds, wrecking buildings, and practically destroying civilization.

"The principle cannot fail.  It is as powerful when applied to the earth as it
is when applied to a [violin note shattering a] wineglass, a [boy pushing a man
on a] swing, or a steel link.  Any one who doubts should only bear in mind the
illustration of the swing.  A small boy, by each time adding a pound to the
force with which a 200-pound man swings, can soon set the man swinging with the
force of 500 pounds.  It is necessary only to keep adding a little force at the
right time."

 * Origin: RAD BBS, Melrose, Oregon (93:9705/4)

It seems pretty certain that resonance is a key to efficient running so it would be interesting to investigate how it might function. Cadence is obviously part of this. Relaxation, foot placement, gravity, muscular impulse from the legs and core and arm actions will contribute to timing.  Perhaps the seemingly disproportionate effect of the arms is due directly to resonance. Perhaps the whole motion could be seen like a wave and successful coordination of all the parts generating a resonance  that sustains momentum with the greatest efficiency. 

1 comment:

  1. A few Pirie notes:

    RE: #11 - Pg. 25, "The relaxation should takeplace during the short passive (stationary) rest period between the power phases of each step of your running. Concentrate very hard on mastering this brief period of relaxation."

    RE: #9 - Pg. 18, "The body's centre of movement is located in the centre of the stomach. The arm position relative to this centre of movement decides your tempo. Thus, arms far away, spread out from the body result in a slow tempo, and a close compact posture produces a rapid/fast tempo. A good example is a skater who spins quickly when compact, but slows dramatically when the arms are thrown away from the body. To run faster, therefore, keep tidy and compact.
    When the athlete wishes to speed up, he must compact up, quicken his tempo, and try to apply more power within these movements. The result is a running style that belies the amount of effort being utilized."