# Force Calculation Of Altitude Drops

As Duxx stated,you can calculate only the medium force(and isn’t so immediate).
The peak force is function of the impact dynamic,wich depends from the ground reaction (material) and mainly from the human exact movement (wich is always different).

While a number might have some value, the real “impact” will depend on a number of factors as duxx stated. We also have to realize that the effect on the athlete will be more pronounced the less skilled they are at landing but also how their tendons, etc. handle the stress.

It’s too early for physics, but the distance traveled during deceleration, from the feet touching down to the body stopping/reversing direction, seems to have beeen overlooked here. This can’t of course just be averaged: V/D, since the rate of deceleration will not be linear. Also, the force is of course much greater momentarily of you are reversing direction and not just stopping.

The system the US uses doesn’t prevent you from doing a conversion as duxx asked for. I’d do it myself if I thought it would get us anywhere.

lol i know it can be converted, im just not going to do it.

Exaclty…!!! We can only calculate the average force and average power during the impact, but only if we have “time to zero velocity” (TV0) of the falling object!
The instantenous values of both power and force will depend on various factors — technique, shoes, material, etc
Thus,

Average Force at Impact = Velocity at impact / TV0 * m
Average Power at Impact = Kinetic Energy at Impact / TV0

Anyway, without force plate you cannot even calculate the variables above, because you don’t have TV0… the falling object will usually bounce which make the calculation a lot more complicated….“Also, the force is of course much greater momentarily of you are reversing direction and not just stopping.” — Juggler

This is what is called a “leg stiffness” if you reffer to feet touch when running, jumping etc. If the leg is more “stiffer” (calculated as the distance of COM traveled— legs or whole body, dont know certainly: stooped reading Biomechanical texts for a year — more directed to sports training). Greater stiffness — shorter ground contact time, and larger force peak (but same force impulse—area under F/T graph).

It is interesting to mention here, that altought some of the coaches say that to improve running speed the athlete should reduce GCT — true, but it should be stressed that minimal GCT is NOT the GOAL, but rather OPTIMAL GCT!!!
Shorter GCT — athlete has less time to apply propulsive forces. Less propulsive forces, less distance traveled and thus speed
Long GCT — great time to apply propulsive forces, but the frequency will suffer and thus speed will suffer too
Optimal GCT — optimal for a given velocity (start, vmax), thus the frequency is optimal, there is enought time to apply propulsive force and thus the stride lenght is optimal too — speed is maximal

Great Stiffness — greater muscle co-contraction (agonists-anatagonists), greater short range active stiffness, greater leg stiffnes, greater plyometrical effect “elastcity”, shorter GCT, reduced propulsive forces application due shorter GCT and antagonists co-contraction — LOWER SPEED

Small Stiffness — smaller muscle co-contraction, greater ability of prime mover to apply force (lower antagonists breaking)
, but lower leg stiffness, increase GCT, more time to apply propulsive force, more time on the ground, less frequency ---- LOWER SPEED

Optimall Stifness — optimall muscle co-contraction for optimal leg stiffness for optimal speed achived, optimal time for propulsive forces to be achived, optimal GCT and stride lenghts — MAXIMAL SPEED

Leg stiffness, is largely affected by muscle-co-contraction, or muscle tone (of agonists and antagonists). Muscle tone is affected by tonic myotatical reflex and voluntary activation ---- thus various types of masages, stretches can RE-SET the tone and affect leg stiffnes and thus performance. This is my explanation of Charlies method’s to reset muscle tone btw runs/heat!

Thats what you get being the derivative of an Imperial power - imperial measurements

ok, this might be a dumb question, but do any of you think that a longer time on the ground during any kind of plyo is benificial? or is this just not working the ssc to its fullest potential? just wondering…
thanks for anyones input