2012

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

BiomechanicsHJ-Boettcher

very good leg stiffness (± 5 dgr) > very good handling of speed > good use of top speed

Overall: intra-individualy there is a strong correlation between run up speed and jump height.

Is power productiona key factor in jumping??

}

}

It is not possible to add energy to the system in the take off

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

± isometric contraction

Running turkeysRoberts et al (1997) Science 275: 1113.

During stance, 20mm muscle fibres lengthen and shorten by 1mm

Hopping wallabiesBiewener et al (1998) J Exp Biol 201: 1691

length length-change

during stance

gastrocnemius

muscle fibres 18mm 2mm

tendon 170mm ~7mm

plantaris

muscle fibres 16mm 0.5mm

tendon 300mm ~7mm

horse plantaris muscle fibres just 2-6mm

9

Ker, Bennett, Bibby, Kester & Alexander (1987) The spring in the arch of the human foot. Nature 325: 147-9.

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

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

Model� Hill

SEC

PEC

CE

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

no length-changeoptimumlength-change

concentric power => CE behaviour“the muscle as a pump”

elastic behaviour => SEC behaviour“the muscle as a super elastic rubber band”

SEC loadlimited

CE shortening

SEC loadhigh

CE isometric

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 powerfor force production

Muscle suitedfor power

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

Model� Hill

SEC

PEC

CE

Muscle trade powerfor force production

Muscle suitedfor 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

slack in concentric muscle behavior

28

24

20

16

12

8

4

0

-400 -300 -200 -100 0

forc

e

stretch

time (msec)

leng

hthc

hang

e (m

m)

a b (vertical squatjump)

SEC parts

CE parts

take off

decreasing influence slack

increasing forces on bones

SEC

PEC

SEC

PEC

CE

Rate of ForceDevelopment

28

24

20

16

12

8

4

0

-400 -300 -200 -100 0

forc

e

stretch

time (msec)

leng

hthc

hang

e (m

m)

a b (vertical squatjump)

SEC parts

CE parts

take off

decreasing influence slack

increasing forces on bones

SEC

PEC

SEC

PEC

CE

Rate of ForceDevelopmentstiffness

slack

energytransport

No slack because of extra weight

Pre-stretch versus slack Kracht en snelheid 3 de counterbeweging; v Ingen, de Boer, Vergoesen 1984

trying to increase the ROM of the “pre-stretch” will only increase slack and influence performance in a negative way

± 20 degrees

F x d = M

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

Stumble reflex

Extension reflex

fixed elements in running cycle and single leg jumps

stumble reflex to overcome loss of horizontal speed

big change of direction

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

little loss of speed

big loss of speed

p-step up p-step down

little loss of speed big loss of speed

Amortization in take off

sagittal plane onlyfrontal plane not measured

sagittal plane amortization

frontal plane amortization

in running

sagittal plane more in low swingleg

frontal plane more in high swingleg

in jumping

sagittal plane more in low swingleg

frontal plane more in high swingleg

in jumping

Rybakov downward hip-motion in take off and turning anklefrom 1-2 clearancefrom 1-3 miss

1! ! ! ! ! ! ! 2! ! ! ! ! ! ! ! 3

isometric conditions in highjumplook 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 linegood use of extension reflexhip 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

startrunup -6 strides

take off board

+ of - 5 cm + of - 40cm -10 of -0 cm

Non-Long Jumpers

Novice Males (Berg etal.,1994)Elite Males (Hay,1988)

Elite Females (Hay,1988)Lee et al. (1982)

Variability (Long Jump run up)

Richard ShuttleworthQU Aus.

53

startrunup

-6 strides take off board

+ of - 5 cm + of - 40cm -10 of -0 cm

run up periferalvision

centralvision

vertical displacement and abduction

arm-actionvertical GRF

positive running

sagittal plane amortization

frontal plane amortization

arm-actionvertical GRF

positive running

with rotation

without rotation

arm-action vertical GRF

positive running

controling vertical displacementby controling hipswing

conclusion;

Total pelvic movement consists of movement in 3 planes.

Frontal plane rotation helps increasing vertical displacement

Transversal plane rotation helps reducing vertical displacement

2012

thanks for listening/IFACScotland

@IFAC_SCOTLAND