James,
I am not saying that the maximal load will be moved at 10m/s^2, I am saying that the load will move at a constant velocity nominal greater than zero. In order for this to happen, the force applied to the bar must equal, in magnitude, the force of gravity acting on the bar which is F=(m)(a) or 2000N in my example.
James,
I’m not sure what to make of the equation you gave or how you derived it, but I’d like to hear how you got it (I’m not that advanced in physics…yet! :o ) Also you mentioned athletes experiencing massive forces while sprinting and landing from heights but these are eccentric muscle actions, the F/V relation debate was being discussed with the pretense of muscle shortening or concentric action only, with Anders stating that the greatest forces are experienced with eccentric activities.
lol - i taught my 14yr athlete how to do cleans in 10min. within 2 weeks she is now hang cleaning 115+
we are getting into a complex subject because to accurately describe the forces involved during a lift a complex model must be established, external and internal forces will not be the same and accelerations will differ depending on joint angle and individual. but I see where you are coming from. still lets say that the acceleration is 1m/s/s during a maximal lift then with a 50 % load accelerating the bar at 10m/s/s will produce an outcome in which force generated is the same, this is a very attainable level of acceleration.
the equation came from Supertraining by Siff and Verk. they do have a derivation there, its really just a manipulation of the original f=ma. so I didn’t derive it. I was not under the pretense of muscle shortening. is obvious the muscular tension during eccentric actions can easily exceed that of concentric actions. and in actually the greatest tension during the movements come with what is called an explosive isometric. during this movement cycle it becomes somewhat useless to differentiate between positive or negative work but conceive of the movement as a fluid action instead of broken up into individual ones. must text will quote that eccentric strength will out match concentric by 130%. but when you consider the ground contact forces during catching a falling load or during a sprint etc. you can start to understand the training effect and transfer to athletics.
James,
I agree that the subject is likely much more complex than the basic physics calculations we are using to describe it. However, say we take the bench press with the maxes described earlier and have the athlete attempt to throw the bar as high in the air as possible. Assuming his bench “stroke” is approx. 1/3 meter it would mean he is capable of getting to lockout and releasing the bar within .26sec. I don’t have access to a force plate, tendo unit or anything of the sort which would be able to measure these quantaties and I know I’m slow but that does not seem to be an attainable feat, at least with 50% 1RM. Maybe someone who does have access to this type of equiptment can chime and let us know if they have seen comparable force readings between maximal lifts and submaximal weights lifted with maximal acceleration.
James,
I’ll have to take a look at that (in Supertraining I assume) when I go home. Anders comment earlier was pertaining to concentric actions only- guess you missed it? I agree with you though about the forces encountered during high velocity eccentrics- sprinting, depth landings, etc.
jay schroeder use to have his atheltes perform 15 maximal velocity reps (30-60% of 1 rep max) for every maximal load lift and each maximal velocity lifts must be completed in a quarter of a second ore less(measured with a tendo unit, now he uses a v scope) or the rep did not count. hell adam archuleta did a max with 531 on the bench in 1.09 seconds (concentric phase). maybe i am getting a littel ahead of myself. being able to lift submaximal loads at high rates of accelration for some requires training. so maybe joe blow in the weight room cant produce a equal force with a light weight but it often exceeds the force generated in a maximal load in trained athletes (properly trained athletes).
i realized wut he was talking about i just expanded the subject as i felt it to be the right time. like i said before i use a fluid model of movement, not one broken up into parts. but the inclusion of eccentric action in the argument does not negate the argument for the concentric. as power athletes our goal should be inversion of the force velocity curve so that at high velocity high forces are generated.
well you’re a better man than me then.
but for real. some people can pick it up quick but it’s very difficult for others. heck i get people who can’t even do a correct bodyweight squat.
While the best high jumpers manage over 1.90m in standing high jump – far better than any weightlifter will ever do – it’s of no surprise that weightlifters are very good at vertical leaps. On the other hand, when looking at their event (biomechanical), it’s rather apparent that two legged verticals belong to their domain (much more so than for high jumpers). High jumpers breed on their eccentric capabilities, speed and a rather straight leg at take off. Yet such training will have some of them perform well in concentric activities as well, without reaching near the loads that professional weightlifters do in the weight room (their strength to weigh ratio are nowhere near the weightlifters). Food for thought! Although, for example, Stefan Holm is horrible at standing long- or high jump, yet managed to clear 2.40m!
vertical jumps and standing high jump have a very poor correletion…
We are talking about power and how to develop it, the high jump is quite peculiar in its training, great jumpers tend to have exceptional eccentric reactive ability, but not super muscular power (explosive strenght).
Returning to speed squats, they can have a role in stimulatin cns and muscle differently, but these are all general means, in no way they approach an actual sprint stride contact time and contraction time
Thats a good explanation…
Does the reactive strength (as expressed in the high jump for example) stem from maximum VOLUNTARY strength?
Personally, I think not…
Excellent example!
what about jump squats and the many variations?
you mean weighted jump squats? Your joints will not thank you. Cleans, powercleans,hang cleans , snatches, hang snatches, powersnatches offer an ideal alternative and a distinct advantage, because they look similar to weighted VJ (2nd pull), without the unnecessary impact.
verticals and standing high jump are very different i doubt any high jumper has a 74 inch vert (1.9m). either way its not important i was only attempting to show that their is abenefit to doing olympic lifts and that those benefits can be further broken down into traits which will help individuals run faster and jump higher. there are a lot of considerations when comapring two atheltes from completly different events. but lol we are both gettin a little off topic.
exactly it is simply a tool, also it cannot come close to the ground contact forces. but that can be replicated throught other means.
dont see how weighted jumps squats with 10-20% of bw lights weights are bad for ur joints