1

Tendon hypertrophyIs it possible? Do we want it?

How can we target it?

Per Aagaard

Institute of Sports Sciences and Clinical Biomechanics,University of Southern Denmark

paagaard@health.sdu.dk

2nd MuscleTech Network Workshop on Muscle and TendonFrom Translational Research to Translational Medicine

Barcelona - September 26th-28th 2010

Effects of chronic knee loading pattern

Sports participation Strength training

Tendon hypertrophyIs it possible? Do we want it? How can we target it?

Achilles tendon CSAin runners and untrained

subjects (males)

Magnusson &Kjær EJAP 2003

2

Elevated Achilles tendon CSA inmale runners vs untrained males

Magnusson & Kjær EJAP 2003

mm's above insertion

...But no change in Achilles tendon CSAfollowing 9 months running training (females)

Hansen, Aagaard, Kjaer, Magnussonet al, J Appl Physiol 2003

Achilles tendon CSA pre and post 9 months run exercise

Pre 1 Pre 2 Post

Couppé et al, J Appl Physiol 2008

PATELLAR CROSS-SECTIONAL AREA

3

Couppé et al, J Appl Physiol 2008 Carroll et al, J Appl Physiol 2008

Stiffness =Slope = ∆F / ∆L

Couppé et al, J Appl Physiol 2008

Non-leadextremity

0

1000

2000

3000

4000

5000

6000

7000

Lead extremity

PATELLAR TENDON STIFFNESS

*

* P < 0.05

Stiffness =Slope = ∆F / ∆L

Stiffness =Slope = ∆F / ∆L

Couppé et al,J Appl Physiol 2008

4

Stiffness =Slope = ∆F / ∆L

Couppé et al,J Appl Physiol 2008

Youngs Modulus(dimension normalizedStiffness) not different

Patellar Tendon CSAElite (National Team) badminton players

1

*

CSA

(mm

2 / BW

2/3 )

02

6

8

10

NDOM side DOM side

Tendinopathy Controls

##

#*

Controls 26 yrsTendinopathy 22 yrs

ControlsTendinopathy

Couppé, Magnusson et al,unpublished results

Tendinopathy < Controls (# p<0.05, ## p<0.01)

Leading Leg

*

Stre

ss (M

Pa)

0

15

20

25

30

NDOM side DOM side

ControlsTendinopathy

#

##**

ControlsTendinopathy

Couppé, Magnusson et al,unpublished results

Patellar tendon stress (proximal site)[at largest common force]

Patellar Tendon CSAElite (National Team) badminton players

Leading Leg

Controls 26 yrsTendinopathy 22 yrs

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Effects of resistance training?

Tendon CSA Tendon stiffness Tendon strain

Tendon hypertrophyIs it possible? Do we want it? How can we target it?

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Kongsgaard, Aagaard, Kjær, Magnusson et al, Acta Physiol Scand 2007

Effects of 12 wks heavy-resistance strength trainingon patella tendon cross-sectional area (CSA)

Tendon levelprox mid dist

CSA

(mm

)

90

100

110

120

130

140

Heavy-pre Heavy-post

↑ proximaltendon CSA

+ 6 %

Cro

ss-s

ectio

nal a

rea

(mm

2 )

Tendon level

↑ distaltendon CSA

+ 4 %

Kongsgaard, Aagaard, Magnusson et al, Acta Physiol Scand 2007

force FPretraining

force FAftertraining

↑ CSA

↓ F/CSA

TENDON

TENDON

Effects of 12 wks heavy-resistance strength trainingon patella tendon cross-sectional area (CSA)

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force FPretraining

force FAftertraining ↓ F/CSA

Tendon hypertrophy ⇒ reduced tendon stress (↓N/cm2)for given level of force loading

may reduce the risk of tendon overuse injury

↑ CSA

TENDON

TENDON

1.65±0.161.47±0.171.36±0.191.42±0.21Modulus (GPa)

4213±405*3676±3773375±3613716±452Stiffness (N/mm)

5.8±0.6*6.3±0.66.5±0.46.3±0.4Strain (%)

PostPrePostPre

Heavy-legs Light-legs

Tendon mechanics calculated based on proximal tendon CSA.Values are means ± SE. Average common tendon force: 4725±374 N.* Significantly higher than pre (p<0.05)

Kongsgaard, Aagaard, KjærMagnusson et al,Acta Physiol Scand 2007

DCB

↑ 14.6%

1.65±0.161.47±0.171.36±0.191.42±0.21Modulus (GPa)

4213±405*3676±3773375±3613716±452Stiffness (N/mm)

5.8±0.6*6.3±0.66.5±0.46.3±0.4Strain (%)

PostPrePostPre

Heavy-legs Light-legs

Tendon mechanics calculated based on proximal tendon CSA.Values are means ± SE. Average common tendon force: 4725±374 N.* Significantly higher than pre (p<0.05)

DCB

↑ 14.6%

↓ 7.9%

Kongsgaard, Aagaard, KjærMagnusson et al,Acta Physiol Scand 2007

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Forc

e (N

)

Increased tendon CSA may reduce the risk of tendon overuse injury

tendon CSA

Deformation ∆L (mm) Kongsgaard, Aagaard, KjærMagnusson et al, Acta Physiol Scand 2007

Forc

e (N

)

Increased tendon CSA may reduce the risk of tendon overuse injury

Inceased tendon CSA

Deformation ∆L (mm) Kongsgaard, Aagaard, KjærMagnusson et al, Acta Physiol Scand 2007

Forc

e (N

)

*

Increased tendon CSA reduce tendon strain (*) thereby reducing

the risk of tendon overuse injury

Inceased tendon CSA

Deformation ∆L (mm) Kongsgaard, Aagaard, KjærMagnusson et al, Acta Physiol Scand 2007

↑ Stiffness (Slope = ∆F / ∆L)

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Micro BiomechanicsMicro Biomechanicssingle collagen fasciclessingle collagen fascicles

Haraldson, Aagaard ,Magnusson et al. 2005

Yield point

Failure point

Length change (mm)

0 1 2 3 4

Stre

ss (M

Pa)

0

20

40

60

80

peak

yield

modulus

Haraldsson, Aagaard, Magnusson et al, 2007

Strain (∆L/Lo, percent)0 5 10 15

Effects of 14 wks strength training on Achilles tendon CSA

Arampatzis et al, J Exp Biol 2007

High Forceresistancetraining

Low Forceresistancetraining

Similar total work load (area under curves)in both training groups

Low Force (55% MVC) - small strain

High Force (90% MVC) - large strain

Low Force (55% MVC) - small strain

High Force (90% MVC) - large strain

TEN

DO

N F

OR

CE

(N)

Gastrocnemius TENDON ELONGATION (mm)

Pre training

Post trainingStiffness = ∆Force / ∆Elongation =Slope

Duclay et al, Muscle Nerve 2009

Changes in tendon stiffness with ECC training7 wks (18 sessions) of ECC plantarflexor training:

6 sets x 6 reps at 120% CONC 1RM

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Pre Post Pre Post Controls ECC Training

Duclay et al, Muscle Nerve 2009

Changes in tendon stiffness with ECC training7 wks (18 sessions) of ECC plantarflexor training:

6 sets x 6 reps at 120% CONC 1RM

Gastrocnemius tendonStiffness

Strength training results in increased tendon stiffness Reeves 2003, Kongsgaard 2007, Arampatzis 2007, Duclay 2009

Strength training may lead to increased tendon CSA Kongsgaard 2007, Arampatzis 2007

…although not demonstrated in all studies Reeves 2003 (old individuals: 74.3 ±3.5 yrs)

Strength training results in diminished tendon strain Kongsgaard 2007, Reeves 2003, Arampatzis 2007

Strength training may lead to increased Youngs Modulus,indicating altered intrinsic tendon properties Reeves 2003 (old individuals), Arampatzis 2007

…although not seen in all studies Kongsgaard et al 2007, 2009, 2010

Effects of resistance training ontendon properties [non-injured tendons]

Increased Tendon stiffness followingheavy-resistance strength training

may protect against tendon overloading due toreduced magnitude of tendon strain

but may also lead to enhanced rapid force capacity(↑ Rate of Force Development: RDF), hencecausing enhanced athletic performance

Rationale: high tendon stiffness is known to berelated to high RFD

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Rapid Force Capacity

1000

2000

3000

4000

5000

0

0.20 0.4 0.6 0.8

Time (seconds)

Forc

e (N

)

RFD = ∆Force / ∆Time

∆Fo

rce

∆Time

max Force

Rate of Force Development (RFD)during maximal isometric muscle contraction

Aagaard et al,J Appl Physiol 2002

Influence of aponeurosis-tendon stiffness in vivo on RFDRapid force capacity (RFD) is positively influenced by muscle tendon stiffness

Bojsen-Møller, Aagaard et al, J Appl Physiol 2005

Bojsen-Møller, Aagaard et al, J Appl Physiol 2005

Influence of aponeurosis-tendon stiffness in vivo on RFDRapid force capacity (RFD) is positively influenced by muscle tendon stiffness

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CONCLUSIONS

It is possible to achieve tendon hypertrophy?Yes!

Do we want it?Yes, indeed! It is likely to protect against tendon overuse dueto a reduced tensile loading (↓F/CSA) and lowered tendonstrain (↓∆L/L).

CONCLUSIONS

It is possible to achieve tendon hypertrophy?Yes!

Do we want it?Yes, indeed! It is likely to protect against tendon overuse dueto a reduced tensile loading (↓F/CSA) and lowered tendonstrain (↓∆L/L).Further, it results in a stiffer tendon → elevated contractileRate of Force Development → allowing high acceleration andelevated muscle power production during rapid movements

How can we target it?Certain types of exercise (RT) seem better than others (RUN)

AcknowledgementsCoworkers at Institute of Sports Medicine Copenhagen,

University of Copenhagen; Institute of Sports Science and ClinicalBiomechanics, University of Southern Denmark:

Henning LangbergMichael KjærJens Bojsen-MøllerPhilip Hansen

Peter MagnussonMads KongsgaardChristian CouppeBjarki Haraldsson