To answer your last question to the best of my ability. Frans Bosch coached or still coaches high jumpers Wilbert Pennings (NED) and Tora Harris (USA) to heights of about 2.30. He also coached sprinter Pally de Leeuw (100m 10.36 or thereabouts) and long jumper Jurgen Cools (ca. 7.85-7.90). These last two athletes are the main athletes performing the exercises shown on the DVD. Frans also takes care of the strength and speed aspects in the training of 400m hurdler Thomas Kortbeek (48.8s).
Klomp is a distance coach, having coached Van Langen (but not when she was world’s no.1), and steeple chasers Laros (8.15-20) and I believe Vroemen (but before Vroemen became big on the world stage as European record holder).
Although I do recommend the book and DVD as “food for thought”, the fact that long jumper Jurgen Cools, the main model in the videos, has great trouble breaking 11 secs (I have actually beaten him on occasion) keeps me wondering about the efficacy of the system.
Oh, Jurgen is a good jumper, no doubt about that, 7.90 is nothing to be laughed at (my 6.59m is though, especially if you see me in the flesh struggling to get any height at takeoff!). But you would expect, assuming that the Bosch model is correct, a guy like him with great strength and power qualities and who apparently approaches the technical model of Bosch to perfection to be much, much faster. And no way, any sprinter however lousy their start (say 4.1-4.2 over first 30m) who runs 11 flat possesses “great” topspeed. You’d have to run at least something like 10.3-4 with a poor start. But I guess our definitions of “greatness” differ.
Yes they are two different things, but I think they are connected… The purpose of this ‘reflex’ is (my free interpretation) to prevent this from happening.
Can you voluntary traini something that isn’t voluntary (if it is reflex)?
For example ‘thinking’ about durring running how to swing the knee forward ASAP of the push-of leg (to facilitate/prestrech the hams of the swing leg preparing to hit the ground).
I had some ‘success’ with cue ‘swing the knee forward’ with some athletes that try to be be powerfull and push-of hard insetad of being quick and relaxing…
Or maybe (I am insinuating) the B&K model is better for jumping (high jumping / long jumping) itself than for sprinting… Jumping differs from running in that the vertical oscillation of the center of Mass is larger. Actually, in running/sprinting, the center of Mass does not rise higher than the position of the center of mass when you stand erect.
I insinuate based on the following. In their book they say that enough pretension in the to-be stance leg should be available in order to shorten electromechanical delay (and increase the rate of force development). However the first part of the stance phase has a horizontal braking component. What happens if you land with a pretensioned leg (especially “stiff” ankle)? I would expect increased vertical oscillation. And that’s exactly what they want.
Is increased vertical oscillation something to strive for in sprinting?
Stefan
The answer to your question may be in the Weyand study. If he force is directed mainly vertical and if there is a relation between how big the force is and how fast you run, then running and jumping are very simular.
If so, the problem can be getting more vertical oscilation (bigger stride lenght) or appliing force quicker after contact. Pretension before landing could assist that. I know you do not like the pretension concept, but lack of pretension in dropjumps do not say anything about pretension in running.
Is this true in elite athletes? I think charlie and those of us who review film on a regular basis will disagree - postive vertical displacement (otherwise known as lift off!)
your may be correct in saying that lack of pretension does not say anything about pretension in running. See below the abstract you (and I) are referencing to.
I speculate that especially a stiff ankle might prevent top speed to be achieved. The reason is that vertical oscillation diminishes as speed increase in sprinting. If a stiff ankle contact the ground the impact of the body on the ground will create an opposite ground reaction force (falling object hits the ground). A stiff ankle will transfer a larger percentage of this force to the COM==> more braking. A less stiff ankle will in my opinion absorb more force in the lower extremity.
Ankle stifness does neet seem to increase markedly at higher speeds, as does knee stifness (work by Arampatzis amd by Kuitunen and Komi).
Another question is if their concept of pretension leading to shortening of the electromechanical delay is correct. Their idea seem to be leant from Bobbert and colleagues based on counter movement jumps. I think counter movent jumps are a different ball game than high velocity sprinting.
My argument of questioning the role of pretension are two-fold:
based on the following article I speculate that it might not be so important
when it is important (for a different reason), I think you should not try to influence volitionally (I believe in autoregulation of the motor system and question whether volitional interventions focused on pretenstion will work, not natural in my opinion)
regards,
Stefan
Netherlands
Abstract:
Duncan A, McDonagh MJ.
Stretch reflex distinguished from pre-programmed muscle activations following landing impacts in man.
J Physiol. 2000 Jul 15;526 Pt 2:457-68.
Duncan A, McDonagh MJ.
Applied Physiology Research Group, School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
Electromyographic activity and joint rotation were measured whilst human subjects jumped down to land on a solid surface 0.45 m below them and then to a false collapsible surface at the same level. The collapsible surface did not produce ankle joint rotation. Objective evidence from post-take-off EMG onset latencies showed that the subjects were surprised by the false surface. 2. Following landing on the solid surface, the gastrocnemius and soleus muscles showed peak responses at latencies of 53 and 56 ms, respectively, and the antagonist m. tibialis anterior showed an early peak response with a latency of 26 ms. These responses occurred following landing on the solid surface but not following passage through the false surface. 3. The rectus femoris and biceps femoris muscles showed no clear reflex activity with this fall distance but pre-programmed activity was clearly present following impact. 4. It is concluded that the post-landing activity in m. soleus and m. gastrocnemius is a short-latency spinal reflex triggered by ankle joint rotation.
@Top cat: are you sure? Knee bends during stance, and of course ther will be vertical oscillation, but I was saying that the COM does not rise higher thant the location of the COM when standing erect (reference: Margaria R. 1975. Biomechanics and energetics of. muscular exercise)
The 1975 study, by definition, could not have involved individuals travelling above 12mps. A problem with studies generally.
Regardless, the faster the speed, the closer under the CM the leg is at its maximum extention (closer to standing erect) and the greater the positive vertical displacement (therefore height) that is added to that.
Of course, if you roll the shoulders forward, therefore locking the hip under and restrict foot extention, claw at the track, and pull back rather than down with the arms, you guarantee that the 1975 study will never be disproved by you!
Well just thinking about it do you think it is impossible for a top sprinter to create so much reaction force that their COM cannot rise after toe off? I’m not sure what the difference is between hip height in stance and when errect is really that great - maybe it is. I’d like to find out.
P90-92
"Another fundamental characteristic of running is that the vertical component of the push (Me:resultant acceleration) has a value equal to the body weight, and it is a constant independent of speed. (me: measured speeds were between 10 and 20 km/h, there was a tendency for more variation at the lower speeds and less variation at speeds around 20 km/h)
…
As shown in fig. 3.18, in running the centre of gravity of the body never lifted above the position it has when the subjes is standing in the erect position"
vertical oscillation migh be less at higher speeds (if sub-elite subjects are taken as research subjects) . In my opinion logical, spending too much time in the air won’t make you faster. At close to top speeds stride lenght does not increase, as does stride rate. Possible the shortest possible ground contact has been reached, and only making the flight more horizontal, less vertical (and hence less time consuming) can add to speed at this point. In addition, leg stifness of the whole leg as a total also increases when speed increases.
The study by Weyand* (famous Hardvard study) showed that both slow and fast sprinters have equal flight time, and since gravity is constant the vertical displacement is the same with slow and fast sprinters.
The following picture is created by Alex Michalow, MD and shows this ‘phenomena’ (to call it like that). Its pure physics.
And since ‘all’ sprinters have equal ArialTime and GroundContactLength, the things that differ between slow and fast sprinter are GroundContactTime and ArialLength.
For two sprinters with equal bodymass, but different speed, since VerticalDispalcement is the same (due same ArialTime) their vertical velocity at the end of the support phase will be the same. This means that VERTICAL FORCE IMPULS will be the same. But since GCT is shorter in fast sprinter he must apply greater vertical ground force (mv=Ft) or have greater ‘leg stiffness’.
If one want to read more comprehensive analysis he should contact Alex Michalow who is member at this forum (alexmicha).
*Weyand, PG, et al. Faster top running speeds are achieved with greater ground forces not more rapid leg movements. J Appl Physiol, 89: 1991 – 1999. 2000.
100m is very different from 800/1500 3000, 5000. The biomechanics of the first 30-40 meter of the 100m differ from biomechanics of constant running. A small part of the book discusses the biomechanics of the start and sprint. Some of the exercises are for sprinters only. Most of the exercises are based on the model of constant running. Main idea is that not VO2max is differentiator between toprunners, but running economy is the key differentiator.
Frans will discuss in june/july during the Track&Field conference:
-Positive Running (sprint subject)
-Running Economy (constant running)
