21.03.2014 Achilles tendon forces during human running The role of - - PDF document

21.03.2014 1

The role of tendon elasticity for sports performance

Jun.-Prof. Kirsten Albracht

Institute of Biomechanics and Orthopaedics German Sport University Cologne albracht@dshs-koeln.de

Komi et al. 1992, J Sports Sci

Achilles tendon forces during human running

5 – 12 times body weight

Sports performance

No series-elastic compliance in all MTUs  26% maximum sprinting velocity

(Miller et al., 2012, J Biomech)

No series-elastic compliance in the Achilles Tendon  10% maximum walking velocity

(Sellers et al., 2010, Int J Primatol)

Material properties are important for tendon function

COM

‚energy conservation‘

Muscle

‚power amplification‘

modified from Roberts & Azizi, 2011, J Exp Biol

+

Jumps with a run up

http://www.iaaf.org/about-iaaf/documents/research

Source of energy

Biewener et al., J Exp Biol, 1998 Roberts & Azizi, J Exp Biol, 2011

Energy conservation

COM

‚energy conservation‘

http://www.oeb.harvard.edu/affiliates/cfs/movies/cfs_wallaby.avi

Biewener et al., J Exp Biol, 1998 Roberts & Azizi, J Exp Biol, 2011

Energy storage Energy release stance

Muscle Tendon Unit Touch down Toe off

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Muscle pre-activation Muscle activation before ground contact regulates muscle stiffness and therefore energy storage in the tendon (Gollhofer & Kyröläinen, 1991; Komi & Gollhofer, 1997; Ishikawa & Komi, 2004)

distal proximal

Ultrasonography is used to study muscle and tendon behaviour of the GM during human locomotion (e.g. Aggelousis et al., 2009, Fukunaga et al., 2001; Ishikawa et al.,

2005; Kawakami et al., 2002; Lichtwark et al., 2007; Spanjaard et al., 2007).

knee heel 20 40 60 80 100

• 0.50
• 0.25

0.00 0.25 0.50 fascicle MTU

change in length [ l0,fl ] Stance [%]

energy storage energy release Phase 1: COM Deceleration Phase 2: COM Acceleration

Energy conservation

• Human running -

Modified from Albracht & Arampatzis, Eur J Appl Physiol, 2013

20 40 60 80 100

• 0.50
• 0.25

0.00 0.25 0.50 fascicle MTU

change in length [ l0,fl ] Stance [%] s l v

f MTU ,

6 

max ,

15 . 5 . 1 v s l v

f f

 

energy storage energy release

Energy conservation

Modified from Albracht & Arampatzis, Eur J Appl Physiol, 2013

Phase 1: COM Deceleration Phase 2: COM Acceleration Leistung & Effizienz Adapted from A.V. Hill, 1938 1.0 0.05 1.0 Maximum shortening velocity Shortening velocity Force/ Power Power Force

Force and Power generation

• Muscle -

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Drop jumps

Optimum Drop Height 120 % Optimum Drop Height Modified from Ishikawa & Komi, Exercise and Sport Science Reviews, 2008

Over-challenging situation

SO GM

Tendon function  Force transmission  Energy Storage & Release  Decoupling of the muscle from the entire muscle-tendon unit

• enable the muscle to work at a higher force potential due to the

force length and force velocity relationship

COM

‚energy conservation‘

Muscle

‚power amplification‘

Modified from Roberts & Azizi, 2011, J Exp Biol

+

Jumps with a run up

http://www.iaaf.org/about-iaaf/documents/research

Source of energy

Power Amplifikation

• Squat Jump-

‚Catapult effect‘

Roberts & Azizi, 2011, J Exp Biol

𝑸𝒑𝒙𝒇𝒔 = Work / Time

• H. C. Astley & T. J. Robert, 2012

The catapult mechanism of frog jumping

Roberts, T. J., Abbott, E. M. and Azizi, E. 2011 http://video.nationalgeographic.com/video/news/frog- muscle-study Data adapted from Kurokawa et al., 2001, J Appl Physiol

• +

+

1000

• 800
• 100

Time (ms) Mechanical power (W)

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• +

+

1000

• 800
• 100

Time (ms) Mechanical power (W) Data adapted from Kurokawa et al., 2001, J Appl Physiol

Jumping performance

• Squat Jump -

Bobbert 2001, J Biomech

Muscle-Tendon-Unit Power > Muscle Power ~ 30%

Tendon function  Force transmission  Energy Storage & Release  Decoupling of the muscle from the entire muscle-tendon unit

• enable the muscle to work at a higher force potential due to the

force length and force velocity relationship

• high power output due to a quick release of the stored energy

Mechanical properties of the tendon

• Effects of resistance training -

Tendon mechanical properties

• Stiffness -

Force deformation relationship

Force Deformation Legerlotz et al., 2007, J Appl Physioll

Tendon mechanical properties

• Stiffness -

Tendon stiffness (k): The extent to which the tendon resists deformation in response to an applied force

Force Deformation 𝑙=

∆ 𝐺𝑝𝑠𝑑𝑓 ∆ 𝐸𝑓𝑔𝑝𝑠𝑛𝑏𝑢𝑗𝑝𝑜 ∆ 𝐺𝑝𝑠𝑑𝑓 ∆ 𝐸𝑓𝑔𝑝𝑠𝑛𝑏𝑢𝑗𝑝𝑜

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Tendon mechanical properties

• Stiffness -

Tendon stiffness (k): The extent to which the tendon resists deformation in response to an applied force Force Deformation

Stiff tendon Less stiff tendon

𝑙=

∆ 𝐺𝑝𝑠𝑑𝑓 ∆ 𝐸𝑓𝑔𝑝𝑠𝑛𝑏𝑢𝑗𝑝𝑜 ∆ 𝐺𝑝𝑠𝑑𝑓 ∆ 𝐺𝑝𝑠𝑑𝑓 ∆ 𝐸𝑓𝑔𝑝𝑠𝑛𝑏𝑢𝑗𝑝𝑜 ∆ 𝐸𝑓𝑔𝑝𝑠𝑛𝑏𝑢𝑗𝑝𝑜

Tendon mechanical properties

• Energy -

Def Force

Energy

Tendon mechanical properties

• Energy storage -

Def Force Def Force

equal force level equal deformation

Def Force

CSA Length

Raspanti et al., 2002

Material properties

Tendon mechanical properties

• Stiffness -

Arampatzis, Karamanidis, Albracht., 2007, J. Exp. Biol

Isometric resistance training, 14 weeks

Mechanical & morphological Properties of the Tendon

• Effects of resistance training -

20 40 60 80 100 120 140 160 180 low high

Moment [Nm]

50 100 150 200 250 300 low high

Stiffness [N/mm]

* * *

Data adapted from Arampatzis, Karamanidis, Albracht., 2007, J. Exp. Biol Low: isometric 55% MWC/ 2.85±0.99% strain High: isometric 90% MVC / 4.55±1.38%

Isometric training, 14 weeks

Mechanical & morphological Properties of the Tendon

• Effects of resistance training -

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Kubo et al., Journal of Strength and Conditioning Research, 24 (2), 2010

 Tendon’s response to training is later than that of muscle

Mechanical & morphological Properties of the Tendon

• Effects of resistance training -

Sprint running Endurance running High power generation High economy

• ptimal muscle & tendon properties

?

Jumping performance

• DEPENDENCE OF HUMAN SQUAT JUMP PERFORMANCE

ON THE ACHILLES TENDON COMPLIANCE- Data adapted from Bobbert 2001, J Biomech 25 30 35 40 45 50 5 10 15 20 jump height [cm] maximum strain [%]

• ptimal

tendon mechanical properties

Kenyan Caucasian control group Shank length [mm] 400 ± 20 430 ± 20 MG Fascicle length [mm] 54.2 ± 4.0 56.8 ± 9.4 MG tendon length [mm] 264 ± 25 196 ± 13*

Sano K, et al., Eur J Appl Physiol, 2013

+ 6 cm

50 100 150 200 250 300 350

• max. moment

[kN strain

• 1]

stiffness [Nm] pre post 20 40 60 80 100 120 140

14 week resistance training for the plantarflexors



• sign. Increase in tendon stiffness (~15%) and muscle strength (~7%)

* *

Albracht & Arampatzis, Eur J Appl Physiol, 2013 

• sign. better running economy: ~4.0 %, p < 0.002

Albracht & Arampatzis, Eur J Appl Physiol, 2013

5 25 30 35 40 45 50

control group exercise group

3.5 ms

• 1

3.0 ms

• 1

3.5 ms

• 1

3.0 ms

• 1

.

VO2 [ml min

• 1 kg
• 1]

pre post

* *

Running economy

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Conclusion  Tendons material properties play an important role in athletic performance (Bobbert 2001, J Biomech, Miller et al., 2012)  Tendons have the potential to adapt (CSA, material properties)  Tendons‘ response to training is later than that of muscle

(Kubo, 2008, J Theor Biol)

 Optimal tendon stiffness is task specific and depends on the mechanical and morphological properties of the MTU

(Lichtwark & Wilson, 2008, J Theor Biol)

Thank you for your attention