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 [email protected] 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  10% maximum walking velocity Source of energy (Sellers et al., 2010, Int J Primatol) Material properties are important for tendon function + Muscle COM ‚power amplification‘ ‚energy conservation‘ modified from Roberts & Azizi, 2011, J Exp Biol Energy conservation stance Touch down Toe off Muscle Unit Tendon COM ‚energy conservation‘ http://www.oeb.harvard.edu/affiliates/cfs/movies/cfs_wallaby.avi Energy storage Biewener et al., J Exp Biol, 1998 Roberts & Azizi, J Exp Biol, 2011 Energy release Biewener et al., J Exp Biol, 1998 Roberts & Azizi, J Exp Biol, 2011 1 distal proximal 21.03.2014 Muscle pre-activation 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., Muscle activation before ground contact regulates muscle stiffness and therefore energy storage in the tendon (Gollhofer & Kyröläinen, 1991; Komi & Gollhofer, 1997; Ishikawa & Komi, 2004) 2005; Kawakami et al., 2002; Lichtwark et al., 2007; Spanjaard et al., 2007). Energy conservation knee - Human running - heel Phase 1: COM Deceleration Phase 2: COM Acceleration 0.50 change in length [ l0,fl ] fascicle MTU 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 Phase 1: COM Deceleration Leistung & Effizienz - Muscle - Phase 2: COM Acceleration 0.50 1.0 vMTU  6 l f ,0 s Force/ Power change in length [ l0,fl ] fascicle MTU 0.25 0.00 Power 0.05 Force -0.25 energy storage energy release -0.50 0 20 40 60 Stance [%] 80 100 v f  1.5 l f ,0 s  0.15vmax Modified from Albracht & Arampatzis, Eur J Appl Physiol, 2013 Shortening velocity 1.0 Maximum shortening velocity Adapted from A.V. Hill, 1938 2 21.03.2014 Over-challenging situation Tendon function 120 % Optimum Drop Height Optimum Drop Height  Force transmission  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 Jump𝑷𝒐𝒘𝒆𝒓 = Work / Time http://www.iaaf.org/about-iaaf/documents/research Source of energy + COM ‚energy conservation‘ ‚Catapult effect‘ Muscle ‚power amplification‘ Modified from Roberts & Azizi, 2011, J Exp Biol Roberts & Azizi, 2011, J Exp Biol The catapult mechanism of frog jumping 1000 + 0 http://video.nationalgeographic.com/video/news/frogmuscle-study Mechanical power (W) + -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 + 0 - Mechanical power (W) + Muscle-Tendon-Unit Power > 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 - ∆ 𝐹𝑜𝑟𝑐𝑒 Tendon stiffness (k): The extent to which the tendon resists deformation in response to an applied force Force Force Force deformation relationship ∆ 𝐷𝑒𝑓𝑜𝑟𝑚𝑎𝑡𝑖𝑜𝑛 Legerlotz et al., 2007, J Appl Physioll 𝑘= ∆ 𝐹𝑜𝑟𝑐𝑒 ∆ 𝐷𝑒𝑓𝑜𝑟𝑚𝑎𝑡𝑖𝑜𝑛 Deformation 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 tendon ∆ 𝐷𝑒𝑓𝑜𝑟𝑚𝑎𝑡𝑖𝑜𝑛 Force ∆ 𝐹𝑜𝑟𝑐𝑒 Force ∆ 𝐹𝑜𝑟𝑐𝑒 Less stiff tendon ∆ 𝐷𝑒𝑓𝑜𝑟𝑚𝑎𝑡𝑖𝑜𝑛 𝑘= Def ∆ 𝐹𝑜𝑟𝑐𝑒 ∆ 𝐷𝑒𝑓𝑜𝑟𝑚𝑎𝑡𝑖𝑜𝑛 Deformation Energy Tendon mechanical properties - Energy storage - - Stiffness - Force Tendon mechanical properties equal deformation equal force level Force Force Def 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] 180 160 140 Stiffness [N/mm] * * 120 300 * 250 200 100 150 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% Arampatzis, Karamanidis, Albracht., 2007, J. Exp. Biol Data adapted from Arampatzis, Karamanidis, Albracht., 2007, J. Exp. Biol 5 21.03.2014 Mechanical & morphological Properties of the Tendon - Effects of resistance training - Endurance running Sprint running High power generation High 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 jump height [cm] 45 Kenyan 40 35 30 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* + 6 cm 25 0 5 10 15 maximum strain [%] 20 Sano K, et al., Eur J Appl Physiol, 2013 Data adapted from Bobbert 2001, J Biomech Running economy 50 [Nm] 120 -1 100 80 150 60 100 40 50 20 0 0 -1 200 40 * * 35 30 . * 45 VO2 [ml min kg ] * 250 pre post 140 -1 300 pre post [kN strain ] 350 Caucasian control group 25 5 0 max. moment stiffness 3.0 ms -1 3.5 ms -1 exercise group 3.0 ms -1 3.5 ms -1 control group 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 6 21.03.2014 Conclusion  Tendons material properties play an important role in athletic performance (Bobbert 2001, J Biomech, Miller et al., 2012) Thank you for your attention  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