I was just messing with the engine in my car and this just struck me:- intake, compression, ignition, and exhaust. How does this relates to the cycle of the leg? Where does each phase of the cycle begin or end? How can we best time the stroke based on TDC or BDC? The relationship of the arms to the legs (cam to the crank)? How can we best increase the efficiency of the stroke based on pure mechanical principles (not based on video on what some one else is doing)? What are your thoughts?
first of all let the mechanic worry about the mechanics of a car and 2-let the coach worry about the mechanics of the athlete!
the mechanical principals of sprint mechanics are natural.the actions involved with these movements are exact from a young age but are put out of place by poor coaching.coach hare look at young kids running/playing out on the field.without thinking what they are doing the mechanics of sprinting are all in place.
i have yet to see a kid run with absurd actions
I always thought kids had bad technique. The swing phase and arm mechanics of kids seems to be far from perfect.
look again at the legs vs arms.they will get TEx and a proper leg action.video your kid/nephew and slow it down
Not all kids have good technique. Believe me, I have seen some bad ones. The kid who is coordinated will execute most of the movements correctly but sometimes the timing of stoke is a bit off. This topic was supposed to stimulate thought on parallels and comparisons to other entities using the same mechanical principles. Only when we understand the principles themselves, can we best help our athletes. I may get an insight from a piece of mechinery working or an animal running in the wild. The mechanical principle are usually similar or there could be some carry over. I find that if you understand the principles, then it is easier to correct any biomechanical problems that the athlete may have.
Show me a native child with poor technique…I tend to see the problems with the xbox kids.
Coachhare,
I would say TDC, is when the foot of the leg passing under the but is at it’s highest point before it goes forward.
I would say BDC, is the instance where the foot is on the ground, but is not on the way off the ground. The part where both the runners arms are at his side.
I would have to say the exhaust is the rear mechanics of the leg after contact with the track. Before the leg is pulled back up.
Compression and igniton will be a little tough. Lets see…
I would have to say that compression is when the leg is actually recovering, on the way back up and to the front of the body. When the hammy’s are activated. Pulling the leg back through.
Igniton would have to be the instant the foot goes past the knee. Since it wouldn’t be loading anymore. This would be the part where the quads are acvitvated and the leg is starting to extend. Everything after that would seem to happen anyway. Just like a piston would go down after igniton, from the force of the explosion.
How do we make the engine more efficient? How do we make more horse’s per liter? Without NOS or Supercharger’s. Funny you bring up timing and all that. My car is out of order right now, becase of a snapped timing belt. 
I think the timing would have to be takin care of with drills and speed work. This is considering we’re talking about an athlete who’s coordinated.
I’m glad you brought this up. I’ve been thinking about it for a while too.
Here is what I equate the movement to:-
Intake: The foot is drawn up. Some coaches call it step over, some call it step up. This action provides the foot with potential energy which is then converted to kenetic energy.
Compression: The foot is accelerated down to the ground underneath the knee. I do not teach negative foot speed or pawing. The foot moving back is incidental to the hips extending. The hip takes on burden of applying force where the knee joint works only to directing the force.
Ignition: This is the push off. The best explaination of this that I have seen is found in the green East German Text. It states that the athlete stretches up off of the ground. Here is where the force is actually applied to allow the athlete to rebound from the ground.
Exhaust: This is the instants foot contact is broken and the foot momentarily hangs at the back waiting to step up/over.
The coach then finds the relation between these positions with both legs. Now it is easier to see if the stroke off depending on the corresponding positions of the legs. It will be easier to fix these problems because of the sequence of movements along with their corresponding actions with both legs.
Should the step over/up be a result of the sprinter pushing his feet off the ground, or an attempt to pull the foot off the groung.
Supposedly, Dan Pfaff teaches pushoff and John Smith teaches pullup.
coach hare you’re right not all kids have good mc’s.clemson is right,ps2+x-box kids can find it difficult walking.i have proven this alot and the general slim/fit/normal weighted kid will have everything in place and will happen without thought thus being natural.
we are trying to get a video going to prove the point
Kids can be very co-ordinated, but their joint ROM in sprinting is small - seems to me this has to be tought.
Most of this stuff happens if the athlete pushes off (ignition) correctly. It is the push off (how, when, where) that causes everything else to happen correctly.
Richard,
Could the small ROM be due to low levels of strength?
Beta, I have wondered this and it could be a factor, but I think primarily kids simply try and move their legs as fast as possible which dictates short ROM. Also, they wouldn’t understand that they should extend the front leg at the end of swing phase ready to ‘sweep’ it underneath, or swing the arms at the shoulders and not so much at the elbows etc.
Range of motion is critical if the athlete wants to execute the motion correctly. This allows all 4 steps to take place. The most critical step is the ignition or the push off.
I have the athlete lead with the knee after the foot breaks contact with the ground. This reduces the moment of inertia of the leg as the leg is tucked thus causing the leg to come through faster.
I find that if the arms move through the full range of motion and the foot is place correctly on the ground, that everything else falls into place. Kids have a tendency to be too quick or in a hurry.
I have this 10 year old athlete who just ran 12.6 in the 100 meters. When he executes well he runs very fast. The hardest thing for him to do was to slow every thing down. For those who want to jump on me, first let me explain. I wanted him to include everything and execute the whole motion. I know he can move fast, but I stress range of motion first, then speed. Meaning that he can only move as fast as he is doing the movement right.
so Richard it that a full extend at the end of the swing phase? Or is it almost full? And then the sweep motion? I thought we were firing or exploding down like a piston. Just looking for clarity.
The (thigh) leg pushes the foot to the ground. Think in terms of pushing the air down underneath the feet for the compression. The athlete should not attempt to sweep the foot back. This is one of the major reasons for hamstring problems and is also a misdirection of force. The leg is tucked and allow to swing through where the athlete leads with the knee. After the knee comes through, the knee joint opens then the foot starts to drop. Remember that the hip is the crank.:afro: