In vivo changes in the human patellar tendon moment arm length with different modes and intensities of muscle contraction

2007 ◽  
Vol 40 (15) ◽  
pp. 3325-3332 ◽  
Author(s):  
Dimitrios E. Tsaopoulos ◽  
Vasilios Baltzopoulos ◽  
Paula J. Richards ◽  
Constantinos N. Maganaris
1999 ◽  
Vol 86 (5) ◽  
pp. 1445-1457 ◽  
Author(s):  
D. E. Rassier ◽  
B. R. MacIntosh ◽  
W. Herzog

The sliding filament and cross-bridge theories of muscle contraction provide discrete predictions of the tetanic force-length relationship of skeletal muscle that have been tested experimentally. The active force generated by a maximally activated single fiber (with sarcomere length control) is maximal when the filament overlap is optimized and is proportionally decreased when overlap is diminished. The force-length relationship is a static property of skeletal muscle and, therefore, it does not predict the consequences of dynamic contractions. Changes in sarcomere length during muscle contraction result in modulation of the active force that is not necessarily predicted by the cross-bridge theory. The results of in vivo studies of the force-length relationship suggest that muscles that operate on the ascending limb of the force-length relationship typically function in stretch-shortening cycle contractions, and muscles that operate on the descending limb typically function in shorten-stretch cycle contractions. The joint moments produced by a muscle depend on the moment arm and the sarcomere length of the muscle. Moment arm magnitude also affects the excursion (length change) of a muscle for a given change in joint angle, and the number of sarcomeres arranged in series within a muscle fiber determines the sarcomere length change associated with a given excursion.


2014 ◽  
Vol 47 (6) ◽  
pp. 1294-1298 ◽  
Author(s):  
Robert M. Erskine ◽  
Christopher I. Morse ◽  
Stephen H. Day ◽  
Alun G. Williams ◽  
Gladys L. Onambele-Pearson
Keyword(s):  

2016 ◽  
Vol 116 (10) ◽  
pp. 1921-1929 ◽  
Author(s):  
Luis M. Alegre ◽  
Michael Hasler ◽  
Sebastian Wenger ◽  
Werner Nachbauer ◽  
Robert Csapo

2003 ◽  
Vol 125 (6) ◽  
pp. 893-901 ◽  
Author(s):  
Ei Yamamoto ◽  
Susumu Tokura ◽  
Kozaburo Hayashi

Effects of cyclic stress on the mechanical properties of collagen fascicles were studied by in vitro tissue culture experiments. Collagen fascicles (approximately 300 μm in diameter) obtained from the rabbit patellar tendon were applied cyclic load at 4 Hz for one hour per day during culture period for one or two weeks, and then their mechanical properties were determined using a micro-tensile tester. There was a statistically significant correlation between tensile strength and applied peak stress in the range of 0 to 5 MPa, and the relation was expressed by a quadratic function. The maximum strength (19.4 MPa) was obtained at the applied peak stress of 1.8 MPa. The tensile strength of fascicles were within a range of control values, if they were cultured under peak stresses between 1.1 and 2.6 MPa. Similar results were also observed in the tangent modulus, which was maintained at control level under applied peak stresses between 0.9 and 2.8 MPa. The stress of 0.9 to 1.1 MPa is equivalent to approximately 40% of the in vivo peak stress which is developed in the intact rabbit patellar tendon by running, whereas that of 2.6 to 2.8 MPa corresponds to approximately 120% of the in vivo peak stress. Therefore, the fascicles cultured under applied peak stresses of lower than 40% and higher than 120% of the in vivo peak stress do not keep the original strength and modulus. These results indicate that the mechanical properties of cultured collagen fascicles strongly depend upon the magnitude of the stress applied during culture, which are similar to our previous results observed in stress-shielded and overstressed patellar tendons in vivo.


2019 ◽  
Vol 201 (Supplement 4) ◽  
Author(s):  
Xiaolong Wang* ◽  
Yiming Wang ◽  
Christian Gratzke ◽  
Bingsheng Li ◽  
Qingfeng Yu ◽  
...  

1999 ◽  
Vol 14 (9) ◽  
pp. 661-666 ◽  
Author(s):  
Constantinos N. Maganaris ◽  
Vasilios Baltzopoulos ◽  
Anthony J. Sargeant

2020 ◽  
Author(s):  
Guanyin Chen ◽  
wangqian zhang ◽  
Jintao Gu ◽  
Yuan Gao ◽  
Lei He ◽  
...  

Abstract Background: Tendon injury is a common but tough medical problem. Unsatisfactory clinical results have been reported in tendon repair using mesenchymal stem cells (MSCs) therapy, creating a need for a better strategy to induce MSCs to tenogenic differentiation. This study was designed to investigate the role of hypoxia in the tenogenic differentiation of MSCs in vitro and in vivo and to compare the tenogenic differentiation capacities of different MSCs under hypoxia condition in vitro. Methods: Adipose tissue-derived MSCs (AMSCs) and bone marrow-derived MSCs (BMSCs) were isolated and characterized by the expression of MSC-specific markers and tri-lineage differentiation. The expression of hypoxia induced factor-1 alpha (Hif-1α) and the proliferation of AMSCs and BMSCs were examined in order to confirm the establishment of hypoxia condition. qRT-PCR, western blot, and immunofluorescence staining were used to evaluate the expression of tendon-associated marker Col-1a1, Col-3a1, Dcn, and Tnmd in AMSCs and BMSCs under hypoxia and/or Tgf-β1 condition. In vivo, a patellar tendon injury model was established. Normoxic and hypoxic BMSCs were cultured and implanted. Histological, biomechanical and transmission electron microscopy analyses were performed to assess the improved healing effect of hypoxic BMSCs on tendon injury. Results: Hypoxia remarkably increased the expression of Hif-1α and the proliferation of AMSCs and BMSCs. Our in vitro results detected that hypoxia not only promoted a significant increase in tenogenic markers in both AMSCs and BMSCs compared with the normoxia group, but also showed higher inductility compared with Tgf-β1. In addition, hypoxic BMSCs exhibited higher potential of tenogenic differentiation than hypoxic AMSCs. Our in vivo results demonstrated that hypoxic BMSCs possessed better histological and biomechanical properties than those of normoxic BMSCs, as evidenced by histological scores, quantitative analysis of immunohistochemical staining for Col-1a1 and Tnmd, the range and average of collagen fibril diameters and patellar tendon biomechanical tests. Conclusions: These findings suggested that hypoxia may be a practical and reliable strategy to induce tenogenic differentiation of BMSCs for tendon repair and could enhance the effectiveness of MSCs therapy in treating tendon injury.


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