That is a mighty definitive statement. As mass moves over it does indeed press the toe into the substrate...and how far down it goes depends on the weight of the horse and the deformability of the substrate. I can't walk on water so I won't speculate the reasoning behind it, but I wrote a song about it. Want to hear it...here it goes: "The following are three of the many examples found in veterinary literature: “Toward the end of the stance phase, the point of action of the ground reaction force moves toward the toe” [1] Dr. Rooney states, while describing how the hind limb propels the body forward, “The retractor muscles continue to operate and, with the foot fixed to the ground, drive the body forward.” [2] “This is followed by propulsion as the toe pushes off from the ground.” [3] " [1] Parks, Andrew. Form and function of the equine digit. The Veterinary Clinics of North America Equine Practice 19 (2003) p. 301 [2] Rooney, James. The Lame Horse. Russell Meerdink Co. (1998) p.140-141 [3] Reigel, R. and Hakola, S. Illustrated Atlas of Clinical Equine Anatomy and Common Disorders of the Horse. Equistar Publications (1996) p.16 Don't need a video. Walk, trot, or canter one across the dirt then look at the foot print left behind. Where is the majority of the depth of deformation of the print? Yes, it is...and it is exactly because of the reciprocal apparatus. When you pick a hind leg up and hold it as if you were sighting down the cannon to the foot, where is the toe pointed? My inner nerd gets in the way of my common sense sometimes too.
In the anterior phase of retraction, the foot is in front of the mass of musculature attachment that is pulling the mass over a fixed position (the foot on the ground). In the posterior phase of retraction, the foot is behind the mass of musculature attachment that is pushing the mass forward. So...if maximum thrust is happening a millisecond before the foot is unloaded, the unloading is occurring toward the end of the posterior phase of retraction...during the push. If this is the case, the mass of the horse's quarter and leg are in front of the foot. Retraction has a unique action within the hock. At the most anterior point of retraction, the hock is extended. As the mass of the hind moves forward and over the stationary foot, the hock flexes. At the point of stride where the transition from anterior to posterior phase of retraction occurs, the hock transitions from flexion back to extension. When maximal extension is reached, the foot turns over and retraction begins. The foot lands heel first and exits toe last. From the time of landing to leaving weight bearing transitions from heel to toe. This transition occurs during force application. Instead of measuring peak force application only, a force plate measurement showing the transition in time with the application would be necessary to determine the significance of the role of 'the toe' in forward motion...but if my understanding of what you are saying is correct (the ground surface of the foot is parallel with the substrate for the vast majority of retraction/force application), you may have a very valid point(s) regarding the significance, or lack thereof, of the toe's action of 'digging in' and the subsequent utilization thereof in force application. Speculation to follow, but I believe a graphic representation of a force plate's measurement of the hind foot during retraction, would show the force moving from heel at landing to toe at leaving...even though on hard such as concrete, the foot would neither sink in the heel at landing nor sink in the toe prior to leaving...or maybe my inner nerd is beating the manure out of my common sense at the moment... Interesting points to ponder Tom...interesting indeed.
Good Stuff, I see it in my head..the conditions of the ground would be the only effect except pathological problems?
Tom you nailed it. The harder the track (and the more difficult it is for the feet to dig in) the faster the times. Always. Bettors and handicapers know this. The sample size is staggeringly large and harder tracks are faster. If the hinds had to dig in to propel the horse the converse would be true.
Accurately stated. Having spent eighteen years as a State Steward for the Texas Racing Commission I had the opportunity to observe this is person time and time again. In addition, having seen literally thousands of races in "frame by frame" sequence, allowed me the opportunity to observe the propulsion that occured at the "starting gate" as compared to the actual "running" of the race. Casual walks on the "turf" and "dirt" enabled me to observe the affect of the hoof on the surface. On the "turf" the distance of the "divot" would be as much as 10 feet from the actual hoof print at the start of the race, whereas it would only be inches away during the course of the race when in full stride, and sometimes there wouldn't be a divot at all. The same was true on the dirt. Times were faster when the surfaces were dry and packed. The "divot" crew on the turf had little to do under dry conditions.
With humans or horses a harder track allows the runner's feet to cycle faster, so faster times, on the soft track it takes longer to get their feet out of the dirt, so slower times (along with the excess energy expenditure on the softer track). Here's a video I thought was interesting with the draft horses digging in with their toes (starts around 2:20 mark). If they weren't trying to "push" harder against the ground, why are they trying to get up on their toes? View: http://youtu.be/D7zk3RdizMk
I think you can still make a case that the hinds are pointed for "digging in" and gaining traction and building momentum, not necessarily for running faster.
Careful that people don't equate 'faster times because the toe doesn't dig in' or 'slower times because the toe does dig in'...which is a completely false assumption. I think what Tom is saying...and is completely accurate...is that when retraction is at an end, and the foot lands, the toe doesn't immediately turn down in effort to 'dig in' over the course of retraction...if this were true, horses walking down an asphalt road would all be walking on their toes...of course, this does not happen. Set two equally fit and fast runners to do a 100 yard dash; both barefoot. One on beach sand and the other on a gym floor. The one on gym floor will win every time. It is not because his/her toe "can't" depress into the ground...nor does the runner on beach sand lose because his/her toe "does" depress into the ground. In a soft ground there is very low friction to provide resistance to the push/pull of the retractor muscles. If we took oil and coated the gym floor prior to the race, the beach sand runner would probably win even though its toes would be pressing down in the sand and the gym floor runner's wouldn't be sinking anywhere...and it would have nothing to do with whether or not either of their toes were or were not sinking in the ground. It has to do with friction. It is an absolute, undeniable, requirement for friction. Without friction there is zero force application to the ground. Without force application to the ground, there is zero forward motion. This is an unavoidable requirement for anything that moves over the ground. People get all bent out of shape about 'putting tension' on tendons...they are supposed to be tensed. That is what they are made for. If they are not under tension, the horse will not move. During acceleration (starting, stopping, turning are all acceleration) there is a higher requirement for traction/friction than there is when maintaining momentum in a straight line. Which is more beneficial to the horse for applying force to the ground ...a shoe that increases traction or one that decreases traction? Slipping/losing traction decreases the ability to apply force. Decrease in force application decreases acceleration. Would you rather run on the beach with bowling shoes or cross-country sneakers? So as the foot moves posterior during retraction (over a soft ground) the point of action/traction starts toward the heel at landing and moves toward the toe at leaving. During this transition, as the mass moves over the stationary foot, the front half of the foot starts being pressed into the ground and right before turn over, it is the 'deepest.' A question needs to be answered here...is the deformation only a consequence of the mass moving over it or is it beneficial to increasing friction...or both? Why do human sprinters use starting blocks on an asphalt/rubber track? What does the starting block do to the position of their foot/toe? Is this different from what happens when the front half of a horse's foot gets pressed into the ground as mass above moves over? (regardless of how 'far' it gets pressed in...wether none on concrete or a lot in heavy sand...the point of action moves toward the toe)
Watch a horse back out of a trailer. They will stab the toe straight down in the ground until they feel secure. Why is that? Take that same horse and leave its front feet in the trailer and just let it stand there for a few moments. Eventually they will transition to flat footed stance. Why do they do this?
Because the flexor becomes an extensor and extensor become a flexor and they dont work well that way round.
We are both wrong on this because the reciprocal apparatus does not function the same when the foot is on the ground vs. when the foot is off the ground. (Rooney, James. The Lame Horse. 1998. p139-141.) ^^^It is possible for the horse to dig it's hind toe in, due to the overlying mass pressing it down. ^^^No, it is not. It is because of the overlying mass pressing it down. Tom may have granted that in his statement. I was just completely wrong in my statement.
The way I see it is if the toe is digging in (which I have not observed in slow motion video shot at high frame rates ~1000frames/sec+) I would call that evidence of loss of energy and propulsion efficiency due to slip. 'nuther words if some dirt got displaced, whatever force went into digging the hole didn't get used to move the horse forward. And none of your references to anatomical function explain why a horse travelling at speed on pavement (I get to see a lot of Amish buggy horses trotting or pacing on the road) does not lift it's heels and subsequently the rest of it's limb and body to raise itself up on its toe due to the supposed rotational force applied on the toe that would otherwise dig in. I can appreciate the theory put forth by the anatomists and I have great respect for their work. But as a scientist I am naturally skeptical of claims that infer that burning rubber means going faster. It just looks cool and makes a lot of smoke.
Denise, did you notice the horses were wearing a collar attached to a sled and that they were also using their front feet for pulling (carpus not locked). And how much speed are we talking about? The handlers are walking beside the sled. You've posted a video of a tractor pull in a thread about formula 1 racing. Though it is a very cool video and I did enjoy watching it, so thanks.
Would a human sprinter run faster if the whole track was lined with starting blocks so that every stride landed in a ratchet lock grip with the track?
Agreed 100%. I don't necessarily believe the horse is utilizing musculature energy to push the toe in the ground. I think the mass of the animal does that on its own as it moves over the foot. Because pavement is strong enough not to allow a foot to be pressed into it and by the time the foot gets to the point of turnover, it is already well behind the mass so if anything it pushes more forward than up. Watch the slow motion part of this video from :19-:37 ish. The cyclic motion pushes the whole limb simultaneously up and forward. View: http://www.youtube.com/watch?v=thpmgolDsbQ Agreed 100%. However, I think it is prudent to point out that acceleration in soft ground is slower due to the substrate moving under the foot, not because of what the foot is doing. The horse is trying to push against ground that is moving out from under it. If the substrate didn't move, there would be no preferential deformation of it under the foot. I believe some got the impression that because the foot sinks in, this causes the slower acceleration when in reality the sinking action is a symptom, not the causative factor. If the foot didn't sink in, it would be even slower because there would be more slippage. In a soft substrate like sand, during the posterior phase of retraction, when the limb is pushing the mass forward, which has a higher frictional coefficient, or more traction, resistance, purchase, or whatever other applicable synonym one chooses to employ: a foot on the top layer of sand or a foot partially rotated down into the sand? This is why professional sprinters (with their body's mass ahead of their feet) use a starting block to push against. ...and stop talking about trailer ramps...someone that knows my wife might read this and in conversation, she might get to thinking that she needs a new trailer with a ramp.
Mechanical advantage is reduced on the soft. Is it possible that posture is altered specific to to ground conditions that you could both be right? If the horse is on soft ground it moves its center of mass forward in relation to the length of stride and on top of the ground it moves it backwards, or at least lengthens it. I can imagine the horse rotating the pelvis forward on firm ground and increasing the cranial part of the stride on soft ground . But just a thought.
