@inproceedings{,
    author = {Holzer, Denis; Hahn, Daniel; Schwirtz, Ansgar; Siebert, Tobias; Seiberl, Wolfgang},
    title = {Exploring the In Vivo Stretch-Shortening Cycle Effect and the Role of Muscle-Tendon Behaviour in the Human Triceps Surae Muscle.},
    editor = {},
    booktitle = {German Exercise Science & Training Conference (16., 2023, Köln)},
    series = {},
    journal = {},
    address = {},
    publisher = {},
    edition = {},
    year = {2023},
    isbn = {},
    volume = {},
    number =  {},
    pages = {},
    url = {},
    doi = {10.13140/RG.2.2.10939.18726},
    keywords = {},
    abstract = {Exploring the In Vivo Stretch-Shortening Cycle Effect and the Role of 
Muscle-Tendon Behavior in the Human Triceps Surae Muscle 
 
 
Exploring the In Vivo Stretch-Shortening Cycle Effect and the Role of 
Muscle-Tendon Behavior in the Human Triceps Surae Muscle 
Denis Holzer1*, Daniel Hahn2,3, Ansgar Schwirtz1, Tobias Siebert4, Wolfgang Seiberl1,5 
1Technical University of Munich, 2Ruhr University Bochum, 3University of Queensland, Australia, 4University 
of Stuttgart, 5Universität der Bundeswehr München 
Keywords: muscle-tendon dynamics, decoupling, architectural gearing, in vivo 
Introduction 
During the shortening phase of stretch-shortening cycles (SSC), muscle force and work are 
increased compared with pure shortening muscle action (SHO). This is referred to as the 
SSC-effect and has been demonstrated in various experiments on a variety of structural 
levels (Seiberl et al., 2015). However, the underlying mechanisms and their interactions are 
still controversially discussed (Seiberl et al., 2021). The aim of this study was to identify how 
architectural  muscle-tendon  unit (MTU)  gearing and  MTU decoupling contributes  to  the 
SSC-effect during in vivo contractions.  
Methods 
Eleven participants (age: 30±5 years, height: 179±5cm, body mass: 79±7kg) performed sub-
maximal  fixed-end,  SSC  and  SHO  plantarflexion  contractions  on  a  dynamometer 
(IsoMed2000, D&R Ferstl GmbH) elicited by electrical nerve stimulation of the tibialis nerve. 
Motion capture (Vicon Peak) was used to assess lower leg kinematics. Ultrasound (Echo 
Blaster 128 CEXT LV7.5/60/128Z-2, UAB Telemed) measures were used to determine fas-
cicle and tendon behavior of the gastrocnemius medialis MTU. A repeated measure analysis 
of variance was performed to identify significant differences during active muscle shortening 
across different contraction conditions. Results are presented as means ± standard devia-
tion, the level of significance is set at α=0.05 and the effect size (η²) of .01, .06, and .14 
refers to small, medium, and large effects, respectively. 
Results 
In SSCs, ankle joint torque and work, MTU force and work, and fascicle force were signifi-
cantly increased during shortening compared with the SHO condition, (joint torque: 19±12%, 
p<0.001 [η²=0.58], MTU force: 22±14%, p<0.001 [η²=0.43], fascicle force: 22±17%, p<0.001 
[η²=0.37]; joint work: 12±13%, p<0.001 [η²=0.83], MTU work: 17±18%, p<0.001 [η²=0.74]). 
In contrast, fascicle work was decreased by 35±41% during SSC shortening compared with 
SHO (p<0.001 [η²=0.24]).  During shortening of SSC,  fascicle  rotation (44±12%, p=0.006 
[η²=0.14]),  fascicle  length  change  (58±72%,  p=0.009  [η²=0.13])  and  shortening velocity 
(32±46%,  p=0.039  [η²=0.07])  were significantly  reduced  compared  with  SHO condition. 
Achilles tendon (AT) length at the beginning of shortening, AT tendon shortening velocity 
and AT length change throughout the shortening phase were unaffected by the contraction 
type (p=0.457 [η²=0.01], p=0.131 [η²<0.01], p=0.127 [η²<0.01], respectively). 
Discussion 
 
 
Our results indicate that architectural muscle gearing leads to a reduction in fascicle short-
ening velocity and fascicle rotation, thereby increasing the muscle’s force production capac-
ity during shortening of SSC. Findings demonstrate how architectural gearing contributes to 
the SSC-effect on all structural levels and underline the compromised transferability of joint 
work measurements to estimated fascicle work. 
Literature 
Seiberl, W., Hahn, D., Power, G. A., Fletcher, J. R. & Siebert, T. 2021 Editorial: The Stretch-Shortening Cycle 
of  Active Muscle and Muscle-Tendon  Complex:  What,  Why  and  How It Increases  Muscle Perfor-
mance? Frontiers in physiology 12, 693141. 
Seiberl, W., Power, G. A., Herzog, W. & Hahn, D. 2015 The stretch-shortening cycle (SSC) revisited: residual 
force enhancement contributes to increased  performance during  fast SSCs of human m.  adductor 
pollicis. Physiological Reports 3. 
Denis Holzer1*, Daniel Hahn2,3, Ansgar Schwirtz1, Tobias Siebert4, Wolfgang Seiberl1,5 
1Technical University of Munich, 2Ruhr University Bochum, 3University of Queensland, Australia, 4University 
of Stuttgart, 5Universität der Bundeswehr München 
Keywords: muscle-tendon dynamics, decoupling, architectural gearing, in vivo 
Introduction 
During the shortening phase of stretch-shortening cycles (SSC), muscle force and work are 
increased compared with pure shortening muscle action (SHO). This is referred to as the 
SSC-effect and has been demonstrated in various experiments on a variety of structural 
levels (Seiberl et al., 2015). However, the underlying mechanisms and their interactions are 
still controversially discussed (Seiberl et al., 2021). The aim of this study was to identify how 
architectural  muscle-tendon  unit (MTU)  gearing and  MTU decoupling contributes  to  the 
SSC-effect during in vivo contractions.  
Methods 
Eleven participants (age: 30±5 years, height: 179±5cm, body mass: 79±7kg) performed sub-
maximal  fixed-end,  SSC  and  SHO  plantarflexion  contractions  on  a  dynamometer 
(IsoMed2000, D&R Ferstl GmbH) elicited by electrical nerve stimulation of the tibialis nerve. 
Motion capture (Vicon Peak) was used to assess lower leg kinematics. Ultrasound (Echo 
Blaster 128 CEXT LV7.5/60/128Z-2, UAB Telemed) measures were used to determine fas-
cicle and tendon behavior of the gastrocnemius medialis MTU. A repeated measure analysis 
of variance was performed to identify significant differences during active muscle shortening 
across different contraction conditions. Results are presented as means ± standard devia-
tion, the level of significance is set at α=0.05 and the effect size (η²) of .01, .06, and .14 
refers to small, medium, and large effects, respectively. 
Results 
In SSCs, ankle joint torque and work, MTU force and work, and fascicle force were signifi-
cantly increased during shortening compared with the SHO condition, (joint torque: 19±12%, 
p<0.001 [η²=0.58], MTU force: 22±14%, p<0.001 [η²=0.43], fascicle force: 22±17%, p<0.001 
[η²=0.37]; joint work: 12±13%, p<0.001 [η²=0.83], MTU work: 17±18%, p<0.001 [η²=0.74]). 
In contrast, fascicle work was decreased by 35±41% during SSC shortening compared with 
SHO (p<0.001 [η²=0.24]).  During shortening of SSC,  fascicle  rotation (44±12%, p=0.006 
[η²=0.14]),  fascicle  length  change  (58±72%,  p=0.009  [η²=0.13])  and  shortening velocity 
(32±46%,  p=0.039  [η²=0.07])  were significantly  reduced  compared  with  SHO condition. 
Achilles tendon (AT) length at the beginning of shortening, AT tendon shortening velocity 
and AT length change throughout the shortening phase were unaffected by the contraction 
type (p=0.457 [η²=0.01], p=0.131 [η²<0.01], p=0.127 [η²<0.01], respectively).},
    note = {},
    institution = {Universität der Bundeswehr München, Fakultät für Humanwissenschaften, HUM 5 - Institut für Sportwissenschaft, Professur: Seiberl, Wolfgang},
    
    
}