Frans Bosch - Basics of Jumping(1)

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.

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Ker (1981) J. Exp. Biol. 93: 283

Model 

Hill

PEC

SEC

CE

model Hill

SEC(series linked elastic component) CE- ( contracting element)

optimum length-change

model Hill

no length-change

SEC(series linked elastic component) CE- ( contracting element)

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

Muscle trade power for force production

Muscle suited for power

Model 

Hill

PEC

SEC

CE

model Hill

Muscle trade power for force production

SEC(series linked elastic component) CE- ( contracting element)

Muscle suited for power

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

PRETENSIONRELEASE 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

  ELASTICSTRETCH  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

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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

thanks for listening /IFACScotland @IFAC_SCOTLAND

2012