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

21.03.2014 Achilles tendon forces during human running The role of tendon elasticity for sports performance Jun.-Prof. Kirsten Albracht 5 – 12 times body weight Institute of Biomechanics and Orthopaedics German Sport University Cologne albracht@dshs-koeln.de Komi et al. 1992, J Sports Sci Jumps with a run up Sports performance No series-elastic compliance in all MTUs  26% maximum sprinting velocity (Miller et al., 2012, J Biomech) http://www.iaaf.org/about-iaaf/documents/research No series-elastic compliance in the Achilles Tendon Source of energy  10% maximum walking velocity (Sellers et al., 2010, Int J Primatol) Material properties are important for tendon function + COM Muscle ‚energy conservation‘ ‚power amplification‘ modified from Roberts & Azizi, 2011, J Exp Biol Energy conservation stance Touch down Toe off Muscle Unit Tendon COM http://www.oeb.harvard.edu/affiliates/cfs/movies/cfs_wallaby.avi ‚energy conservation‘ Energy storage Energy release Biewener et al., J Exp Biol, 1998 Biewener et al., J Exp Biol, 1998 Roberts & Azizi, J Exp Biol, 2011 Roberts & Azizi, J Exp Biol, 2011 1

21.03.2014 proximal distal Muscle pre-activation Ultrasonography is used to study muscle and tendon behaviour of the GM Muscle activation before ground contact regulates muscle stiffness and therefore energy storage in the tendon (Gollhofer & Kyröläinen, 1991; Komi & Gollhofer, 1997; Ishikawa & Komi, 2004) 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) . Energy conservation - Human running - knee heel Phase 1: COM Deceleration Phase 2: COM Acceleration 0.50 fascicle MTU change in length [ l 0,fl ] 0.25 0.00 -0.25 energy storage energy release -0.50 0 20 40 60 80 100 Stance [%] Modified from Albracht & Arampatzis, Eur J Appl Physiol, 2013 Force and Power generation Energy conservation Leistung & Effizienz - Muscle - Phase 1: COM Deceleration Phase 2: COM Acceleration 0.50 fascicle MTU 1.0 change in length [ l 0,fl ] 0.25 l  f , 0 v 6 MTU Power s Force/ Power 0.00 0.05 Force -0.25 energy storage energy release l -0.50  1.0 f , 0 v 1 . 5 0 20 40 60 80 100 Maximum f s Shortening velocity Stance [%] shortening  velocity 0 . 15 v max Modified from Albracht & Arampatzis, Eur J Appl Physiol, 2013 Adapted from A.V. Hill, 1938 2

21.03.2014 Over-challenging situation Tendon function 120 % Optimum  Force transmission Optimum Drop Height Drop Height  Energy Storage & Release SO  Decoupling of the muscle from the entire muscle-tendon unit GM • enable the muscle to work at a higher force potential due to the force length and force velocity relationship Drop jumps Modified from Ishikawa & Komi, Exercise and Sport Science Reviews, 2008 Jumps with a run up Power Amplifikation - Squat Jump - 𝑸𝒑𝒙𝒇𝒔 = Work / Time http://www.iaaf.org/about-iaaf/documents/research Source of energy + ‚Catapult effect‘ COM Muscle ‚energy conservation‘ ‚power amplification‘ Modified from Roberts & Azizi, 2011, J Exp Biol Roberts & Azizi, 2011, J Exp Biol The catapult mechanism of frog jumping 1000 Mechanical power (W ) + + 0 - http://video.nationalgeographic.com/video/news/frog- muscle-study -800 -100 0 Time (ms) H. C. Astley & T. J. Robert, 2012 Roberts, T. J., Abbott, E. M. and Azizi, E. 2011 Data adapted from Kurokawa et al., 2001, J Appl Physiol 3

21.03.2014 Jumping performance - Squat Jump - 1000 Mechanical power (W ) + + Muscle-Tendon-Unit Power > 0 Muscle Power - ~ 30% -800 -100 0 Time (ms) Bobbert 2001, J Biomech Data adapted from Kurokawa et al., 2001, J Appl Physiol Tendon function Mechanical properties of the tendon  Force transmission - Effects of resistance training -  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 Tendon mechanical properties Tendon mechanical properties - Stiffness - - Stiffness - Tendon stiffness (k): The extent to Force deformation relationship which the tendon resists deformation in response to an applied force Force ∆ 𝐺𝑝𝑠𝑑𝑓 Force ∆ 𝐺𝑝𝑠𝑑𝑓 𝑙 = ∆ 𝐸𝑓𝑔𝑝𝑠𝑛𝑏𝑢𝑗𝑝𝑜 ∆ 𝐸𝑓𝑔𝑝𝑠𝑛𝑏𝑢𝑗𝑝𝑜 Deformation Legerlotz et al., 2007, J Appl Physioll Deformation 4

21.03.2014 Tendon mechanical properties Tendon mechanical properties - Stiffness - - Energy - Tendon stiffness (k): The extent to which the tendon resists deformation in response to an applied force Stiff Less stiff Force tendon tendon ∆ 𝐺𝑝𝑠𝑑𝑓 ∆ 𝐺𝑝𝑠𝑑𝑓 Force ∆ 𝐸𝑓𝑔𝑝𝑠𝑛𝑏𝑢𝑗𝑝𝑜 ∆ 𝐸𝑓𝑔𝑝𝑠𝑛𝑏𝑢𝑗𝑝𝑜 Def ∆ 𝐺𝑝𝑠𝑑𝑓 𝑙 = ∆ 𝐸𝑓𝑔𝑝𝑠𝑛𝑏𝑢𝑗𝑝𝑜 Deformation Energy Tendon mechanical properties Tendon mechanical properties - Energy storage - - Stiffness - Force equal deformation equal force level Def Force Force Raspanti et al., 2002 Def Def CSA Length Material properties Mechanical & morphological Properties of the Tendon Mechanical & morphological Properties of the Tendon - Effects of resistance training - - Effects of resistance training - Moment [Nm] Stiffness [N/mm] 180 300 * * * 160 250 140 120 200 100 150 80 60 100 40 50 20 0 0 low high low high Isometric training, 14 weeks Isometric resistance training, 14 weeks Low: isometric 55% MWC/ 2.85 ± 0.99% strain High: isometric 90% MVC / 4.55 ± 1.38% Data adapted from Arampatzis, Karamanidis, Albracht., Arampatzis, Karamanidis, Albracht., 2007, J. Exp. Biol 2007, J. Exp. Biol 5

21.03.2014 Mechanical & morphological Properties of the Tendon - Effects of resistance training - Endurance running Sprint running High power High generation economy optimal muscle & tendon properties  Tendon’s response to training is later than that of muscle ? Kubo et al., Journal of Strength and Conditioning Research, 24 (2), 2010 Jumping performance - DEPENDENCE OF HUMAN SQUAT JUMP PERFORMANCE ON THE ACHILLES TENDON COMPLIANCE - 50 optimal tendon mechanical properties 45 Kenyan Caucasian control jump height [cm] group 40 Shank length [mm] 400 ± 20 430 ± 20 35 MG Fascicle length [mm] 54.2 ± 4.0 56.8 ± 9.4 30 MG tendon length [mm] 264 ± 25 196 ± 13* + 6 cm 25 0 5 10 15 20 maximum strain [%] Sano K, et al., Data adapted from Bobbert 2001, J Biomech Eur J Appl Physiol, 2013 Running economy 50 pre 350 140 pre post * * post 45 300 120 * -1 ] 250 100 40 -1 kg * -1 ] [kN strain 200 80 VO 2 [ml min 35 [Nm] 150 60 30 100 40 . 25 50 20 5 0 3.0 ms -1 -1 -1 -1 0 0 3.5 ms 3.0 ms 3.5 ms max. moment stiffness exercise group control group 14 week resistance training for the plantarflexors  sign. Increase in tendon stiffness (~15%) and muscle strength (~7%)  sign. better running economy : ~4.0 %, p < 0.002 Albracht & Arampatzis, Eur J Appl Physiol, 2013 Albracht & Arampatzis, Eur J Appl Physiol, 2013 6

21.03.2014 Conclusion Thank you for your attention  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) 7