Muscle-tendon mechanics of a heel drop-raise exercise · Muscle-tendon mechanics of a heel...

Muscle-tendon mechanics of a heel drop-raise exercise

Taija FinniNeuromuscular Research Center

Department of Biology of Physical ActivityUniversity of Jyväskylä

Taija Finni 22.9.2016 Biomechanics symposium, Jyväskylä

Stretch-Shortening Cycle

Braking phase Push-off phase

Muscle-tendon unit Lengthens Shortens

Muscle fibers ? ?Taija Finni 2001, PhD defenseTaija Finni 22.9.2016 Biomechanics symposium, Jyväskylä

When does eccentric muscle action occur?

What was thislocomotion?

Fas

cicl

ele

ng

th

chan

ge

(mm

)

Cronin & Finni 2013

RUNNING

HOPPING

WALKING

Hoffren et al.

2012Taija Finni 22.9.2016 Biomechanics symposium, Jyväskylä

Heel drop-raise exercise

• Calf-raise test -> clinical test

• Heel raise exercise

• Heel drop-raise exercise

Alfredson et al. 1998

Eccentriccomponent?


Muscle-tendon functionin heel drop-raise exercise

Taija Finni, Emma Niemi, Andrew G Cresswell & Glen A Lichtwark




How is tendon and aponeurosis length (and stiffness) modulated with increasing force and in different types of muscle actions?

Hypotheses: • With higher load the tendon elongates more but the

aponeurosis does not.

Force

Length

Tendon


Tendon-aponeurosis strain%

MVC %

Achilles tendonstrain

Aponeurosis strain

Reference & muscle

0 2 4 Arampatzis et al. 2006

GM - elongated

20 2.8 <1.2 nonuniform

Finni et al. 2003

SOL

40 4.7 <2.2 nonuniform

Finni et al. 2003

SOL

100 8.0 1.4 Magnusson et al. 2003

GM

Free Achilles tendon

Aponeurosis

of insertion

Relevance: Use of elastic potential in tendon, optimize muscle performance

Force

Length

Tendon


Tendon vs. aponeurosis

Tilp et al. 2012

Aponeurosis length changes do not depend on force alone but depend critically on activation level...

Tibialis anterior muscle

At given TA force, length of elastictissues dependes on muscle length: longer length, smaller length chang

Raiteri et al. 2016 ASBabstract




How is tendon and aponeurosis length (and stiffness) modulated with increasing force and in different types of muscle actions?

Hypotheses: • With higher load the tendon elongates more but the

aponeurosis does not. • Aponeurosis stiffness is different between contraction

modes at a given force level • Tilp et al 2012: TA aponeurosis lengthens less in

eccentric vs. concentric action.

Muscle fascicle function?Taija Finni 22.9.2016 Biomechanics symposium, Jyväskylä

Methods

• Bilateral & Unilateral• 30 & 50 times/minute• With body weight up to +40%BW


Movement symmetry

0

0,2

0,4

0,6

0,8

1

1,2

30/min 50/min

Tim

e (

s)

CON

ECC

Time of the phases

Ach

ille

ste

nd

on

forc

e(k

N) CON mean

ECC mean

BL BL+30 BL+40 UL UL+10 UL+300

0.5

1.0

1.5

2.5

3.0

2.0

Mean tendon forces of the phases


Methods

• Bilateral & Unilateral• 30 & 50 times/minute• With body weight up to +40%BW

MG fascicle

Muscle-tendonjunction

• Motion capture• Ground reaction forces• Ultrasonography


Heel raise-drop cycle


MethodsUltrasound in lab space

MG fascicle

MG tendon

Aponeurosis

• Joint moments -> Achilles tendon force• Joint angles -> MG muscle-tendon unit length


Achilles tendon forceMoment

arm ratioschange


1000

400

600

800

ATF (N)

EMG (%)

4.5

4.4

ATma(cm)

0.4

0.6

0.2

0

MTU min

MTU max

ECCCON

AT moment armin walking(Rasske et al. 2016)


Activation level

Mea

nA

chill

este

nd

on

forc

e(N

)

Normalized EMG (%MVC)


Achilles tendon force

Do fluctuationsprovide stimulus

for tendon?

Vibrationstimulatescollagensynthesis


Do muscle fascicles stretch?

Fas

cicl

ele

ng

th

chan

ge

(mm

)

Cronin & Finni 2013

RUNNINGWALKING


Do muscle fascicles stretchin heel drop exercise?

Concentric Eccentric


Take home messages

• Stretch of muscle fibers is uncoupled from MTU

– Muscle specificity

– Movement specificity

• Tendon – aponeurosis behavior is uncoupled

• Tendon oscillates in eccentric phase of heel drop

– > stimulus for collagen synthesis?


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