Muscle-tendon mechanics of a heel drop-raise exercise

Transcription

1 Muscle-tendon mechanics of a heel drop-raise exercise Taija Finni Neuromuscular Research Center Department of Biology of Physical Activity University of Jyväskylä

2 Stretch-Shortening Cycle Braking phase Push-off phase Muscle-tendon unit Lengthens Shortens Muscle fibers?? Taija Finni 2001, PhD defense

3 Fascicle length change (mm) When does eccentric muscle action occur? WALKING What was this locomotion? RUNNING Cronin & Finni 2013 HOPPING Hoffren et al. 2012

4 Heel drop-raise exercise Calf-raise test -> clinical test Heel raise exercise Heel drop-raise exercise Eccentric component? Alfredson et al. 1998

5 Muscle-tendon function in heel drop-raise exercise Taija Finni, Emma Niemi, Andrew G Cresswell & Glen A Lichtwark

6 Muscle-tendon function in 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 Tendon Length

7 Tendon-aponeurosis strain% Aponeurosis of insertion Free Achilles tendon MVC % Achilles tendon strain Aponeurosis strain Reference & muscle Arampatzis et al GM - elongated <1.2 nonuniform <2.2 nonuniform Finni et al SOL Finni et al SOL Magnusson et al GM Relevance: Use of elastic potential in tendon, optimize muscle performance Force Tendon Length

8 Tendon vs. aponeurosis Tibialis anterior muscle Aponeurosis length changes do not depend on force alone but depend critically on activation level... At given TA force, length of elastic tissues dependes on muscle length: longer length, smaller length chang Raiteri et al ASBabstract Tilp et al. 2012

9 Muscle-tendon function in 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. 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?

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

11 Time (s) Achilles tendon force (kn) Movement symmetry Time of the phases 1,2 CON 1 ECC 0, Mean tendon forces of the phases CON mean ECC mean 0, , , /min 50/min 0 BL BL+30 BL+40 UL UL+10 UL+30

12 Methods MG fascicle Muscletendon junction Bilateral & Unilateral Motion capture 30 & 50 times/minute Ground reaction forces With body weight up to +40%BW Ultrasonography

13 Heel raise-drop cycle

14 Methods Ultrasound in lab space MG fascicle Aponeurosis MG tendon Joint moments -> Achilles tendon force Joint angles -> MG muscle-tendon unit length

15 Achilles tendon force Moment arm ratios change

16 ATF (N) EMG (%) MTU min CON ECC MTU max 4.5 ATma (cm) 4.4 AT moment arm in walking (Rasske et al. 2016)

17 Mean Achilles tendon force (N) Activation level Normalized EMG (%MVC)

18 Achilles tendon force Vibration stimulates collagen synthesis Do fluctuations provide stimulus for tendon?

19 Fascicle length change (mm) Do muscle fascicles stretch? WALKING RUNNING Cronin & Finni 2013

20 Do muscle fascicles stretch in heel drop exercise? Concentric Eccentric

21 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?