The call for environmentally compatible and economical vehicles, which nevertheless must still satisfy demands for high performance, necessitates immense efforts to develop innovative engine concep...
Descrição: The call for environmentally compatible and economical vehicles, which nevertheless must still satisfy demands for high performance, necessitates immense efforts to develop innovative engine concep...
Deskripsi lengkap
bosch
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These notes are created by me for the benefit of those who are keen to gain a theoritical introduction to South Indian Classical Music which is also popularly known as Carnatic Music. Thi…Full description
Fundamentals of IEC 61850
Basics of single leg jumping Frans Bosch • elasticity versus power • muscle slack as influential factor for performance • using reflexes in take off • amortization in power and speed jump • p-step • preparing for p-step • regulating stride-length
2012
Overall: intra-individualy there is a strong correlation between run up speed and jump height.
very good leg stiffness (± 5 dgr) > very good handling of speed > good use of top speed
BiomechanicsHJ-Boettcher
Is power production a key factor in jumping??
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It is not possible to add energy to the system in the take off
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Performance depends greatly on how much energy can be added to system. Power production is the basis of jumping Why is this not possible?
elasticity versus power
elasticity as main characteristic of running
Running turkeys Roberts et al (1997) Science 275: 1113. During stance, 20mm muscle fibres lengthen and shorten by 1mm
± isometric contraction
Hopping wallabies Biewener et al (1998) J Exp Biol 201: 1691
length
length-change during stance
gastrocnemius muscle fibres tendon
18mm 170mm
2mm ~7mm
plantaris muscle fibres tendon
16mm 300mm
0.5mm ~7mm
horse plantaris muscle fibres just 2-6mm
Ker, Bennett, Bibby, Kester & Alexander (1987) The spring in the arch of the human foot. Nature 325: 147-9.
concentric power => CE behaviour “the muscle as a pump” SEC load limited
CE shortening
SEC load high
CE isometric
elastic behaviour => SEC behaviour “the muscle as a super elastic rubber band”
14
1 body posture erect 2 short contact time and little change in joint angles 3 pretension prior to ground contact 4 drop height not more than jumping height
As long as there is substantial elastic load in the SEC elements. muscle fibres stay in an isometric contraction.
muscle slack as influential factor for performance
Rate of Force Development
slack in concentric muscle behavior
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slack
Rate of Force Development
decreasing influence slack
increasing forces on bones
28 SEC
SEC parts
24
CE
force
SEC
PEC
lenghthchange (mm)
PEC
20
CE parts
16
take off 12
8
4
0
stretch
-400
-300
-200
-100
0
time (msec) a
b (vertical squatjump)
Rate of Force
stiffness Development
decreasing influence slack
increasing forces on bones
28 SEC
SEC parts
24
CE
force
SEC
PEC
lenghthchange (mm)
PEC
20
CE parts
16
take off 12
8
4
PRETENSION RELEASE 0
stretch
-400
-300
-200
-100
time (msec) a
slack energy transport
b (vertical squatjump)
0
No slack because of extra weight
Pre-stretch versus slack
Kracht en snelheid 3 de counterbeweging; v Ingen, de Boer,Vergoesen 1984
COUNTERMOVEMENTJUMP
PRESTRETCH VAN )NGEN
ELASTIC STRETCH SLACK
ELASTIC STRETCH \
trying to increase the ROM of the “pre-stretch” will only increase slack and influence performance in a negative way
Fxd=M
- EXTERNAL ± 20 degrees
- MUSCLE
KNEE EXTENDED
COLLAPS
KNEE BEND
Conclusion; It is not possible to add energy to the system in the take off Power production is not a key factor in single leg jumping from run up Leg stiffness and elastic muscle work is key Trying to increase pre-stretch is counterproductive
using reflexes in take off
fixed elements in running cycle and single leg jumps
Stumble reflex Extension reflex
big change of direction
stumble reflex to overcome loss of horizontal speed
small change of direction extension reflex to to increase stiffness in the take off leg
relevant position
irrelevant position
emphasis on a high knee position and a vertical shin in take off is wrong
amortization in power and speed jump
big loss of speed
little loss of speed
little loss of speed
p-step up
big loss of speed
p-step down
Amortization in take off
sagittal plane only frontal plane not measured
frontal plane amortization
sagittal plane amortization in running
frontal plane more in high swingleg
sagittal plane more in low swingleg in jumping
frontal plane more in high swingleg
sagittal plane more in low swingleg in jumping
1! ! ! ! ! ! ! 2! ! ! ! ! ! ! ! 3 Rybakov downward hip-motion in take off and turning ankle from 1-2 clearance from 1-3 miss
isometric conditions in highjump look at the free hip
p-step
Criteria p-step:
• short contact with knee extended • be as high as possible (do not sit on p-step) • no heel to toe action (slack) • instant reaction hip in upward direction
Do not do this
CM moving up in the P-step
upward motion in p-step
p-step and take off
criteria
CM has to travel over the foot well CM has to travel in ± straight line good use of extension reflex hip knee- ankle sequence and footplant from above
Conclusion; The run up should be designed for gaining speed But also for getting the CM in the right position before the p-step The hight of the CM is very critical for performance From the p-step the CM should travel up as much as possible.
regulating stride-length
Variability (Long Jump run up)
Non-Long Jumpers Novice Males (Berg et al.,1994) Elite Males (Hay,1988) Elite Females (Hay, 1988) Lee et al. (1982) Richard Shuttleworth QU Aus.
start runup
take off board
-6 strides
+ of - 5 cm
+ of - 40cm
-10 of -0 cm
periferal vision
run up
start runup
-6 strides
+ of - 5 cm
take off board
central vision
+ of - 40cm
-10 of -0 cm
53
arm-action
vertical GRF
positive running
vertical displacement and abduction
frontal plane amortization
sagittal plane amortization
arm-action
vertical GRF
positive running
with rotation
without rotation
arm-action
vertical GRF
controling vertical displacement by controling hipswing
positive running
conclusion; Total pelvic movement consists of movement in 3 planes. Frontal plane rotation helps increasing vertical displacement Transversal plane rotation helps reducing vertical displacement
