Influence of aging on the in vivo properties of human patellar tendon

Tendons are important for optimal muscle force transfer to bone and play a key role in functional ability. Changes in tendon properties with aging could contribute to declines in physical function commonly associated with aging. We investigated the in vivo mechanical properties of the patellar tendon in 37 men and women [11 young (27 ± 1 yr) and 26 old (65 ± 1 yr)] using ultrasonography and magnetic resonance imaging (MRI). Patella displacement relative to the tibia was monitored with ultrasonography during ramped isometric contractions of the knee extensors, and MRI was used to determine tendon cross-sectional area (CSA) and signal intensity. At peak force, patellar tendon deformation, stress, and strain were 13 ( P = 0.05), 19, and 12% less in old compared with young ( P < 0.05). Additionally, deformation, stiffness, stress, CSA, and length were 18, 35, 41, 28, and 11% greater ( P < 0.05), respectively, in men compared with women. After normalization of mechanical properties to a common force, no age differences were apparent; however, stress and strain were 26 and 22% higher, respectively, in women compared with men ( P < 0.05). CSA and signal intensity decreased 12 and 24%, respectively, with aging ( P < 0.05) in the midregion of the tendon. These data suggest that differences in patellar tendon in vivo mechanical properties with aging are more related to force output rather than an age effect. In contrast, the decrease in signal intensity indirectly suggests that the internal milieu of the tendon is altered with aging; however, the physiological and functional consequence of this finding requires further study.

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Mechanical properties and collagen cross-linking of the patellar tendon in old and young men

Journal of Applied Physiology ◽

10.1152/japplphysiol.00291.2009 ◽

2009 ◽

Vol 107 (3) ◽

pp. 880-886 ◽

Cited By ~ 154

Author(s):

C. Couppé ◽

P. Hansen ◽

M. Kongsgaard ◽

V. Kovanen ◽

C. Suetta ◽

...

Keyword(s):

Mechanical Properties ◽

Patellar Tendon ◽

Structural Integrity ◽

Young Men ◽

Activity Level ◽

Cross Linking ◽

Collagen Concentration ◽

Cross Sectional ◽

Age Related

Age-related loss in muscle mass and strength impairs daily life function in the elderly. However, it remains unknown whether tendon properties also deteriorate with age. Cross-linking of collagen molecules provides structural integrity to the tendon fibrils and has been shown to change with age in animals but has never been examined in humans in vivo. In this study, we examined the mechanical properties and pyridinoline and pentosidine cross-link and collagen concentrations of the patellar tendon in vivo in old (OM) and young men (YM). Seven OM (67 ± 3 years, 86 ± 10 kg) and 10 YM (27 ± 2 years, 81 ± 8 kg) with a similar physical activity level (OM 5 ± 6 h/wk, YM 5 ± 2 h/wk) were examined. MRI was used to assess whole tendon dimensions. Tendon mechanical properties were assessed with the use of simultaneous force and ultrasonographic measurements during ramped isometric contractions. Percutaneous tendon biopsies were taken and analyzed for hydroxylysyl pyridinoline (HP), lysyl pyridinoline (LP), pentosidine, and collagen concentrations. We found no significant differences in the dimensions or mechanical properties of the tendon between OM and YM. Collagen concentrations were lower in OM than in YM (0.49 ± 0.27 vs. 0.73 ± 0.14 mg/mg dry wt; P < 0.05). HP concentrations were higher in OM than in YM (898 ± 172 vs. 645 ± 183 mmol/mol; P < 0.05). LP concentrations were higher in OM than in YM (49 ± 38 vs. 16 ± 8 mmol/mol; P < 0.01), and pentosidine concentrations were higher in OM than in YM (73 ± 13 vs. 11 ± 2 mmol/mol; P < 0.01). These cross-sectional data raise the possibility that age may not appreciably influence the dimensions or mechanical properties of the human patellar tendon in vivo. Collagen concentration was reduced, whereas both enzymatic and nonenzymatic cross-linking of concentration was elevated in OM vs. in YM, which may be a mechanism to maintain the mechanical properties of tendon with aging.

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Mechanical properties of human patellar tendon at the hierarchical levels of tendon and fibril

Journal of Applied Physiology ◽

10.1152/japplphysiol.01172.2011 ◽

2012 ◽

Vol 112 (3) ◽

pp. 419-426 ◽

Cited By ~ 49

Author(s):

René B. Svensson ◽

Philip Hansen ◽

Tue Hassenkam ◽

Bjarki T. Haraldsson ◽

Per Aagaard ◽

...

Keyword(s):

Mechanical Properties ◽

Young’S Modulus ◽

Patellar Tendon ◽

Young's Modulus ◽

Hierarchical Structures ◽

Collagen Fibrils ◽

Cross Sectional ◽

Hierarchical Levels

Tendons are strong hierarchical structures, but how tensile forces are transmitted between different levels remains incompletely understood. Collagen fibrils are thought to be primary determinants of whole tendon properties, and therefore we hypothesized that the whole human patellar tendon and its distinct collagen fibrils would display similar mechanical properties. Human patellar tendons ( n = 5) were mechanically tested in vivo by ultrasonography. Biopsies were obtained from each tendon, and individual collagen fibrils were dissected and tested mechanically by atomic force microscopy. The Young's modulus was 2.0 ± 0.5 GPa, and the toe region reached 3.3 ± 1.9% strain in whole patellar tendons. Based on dry cross-sectional area, the Young's modulus of isolated collagen fibrils was 2.8 ± 0.3 GPa, and the toe region reached 0.86 ± 0.08% strain. The measured fibril modulus was insufficient to account for the modulus of the tendon in vivo when fibril content in the tendon was accounted for. Thus, our original hypothesis was not supported, although the in vitro fibril modulus corresponded well with reported in vitro tendon values. This correspondence together with the fibril modulus not being greater than that of tendon supports that fibrillar rather than interfibrillar properties govern the subfailure tendon response, making the fibrillar level a meaningful target of intervention. The lower modulus found in vitro suggests a possible adverse effect of removing the tissue from its natural environment. In addition to the primary work comparing the two hierarchical levels, we also verified the existence of viscoelastic behavior in isolated human collagen fibrils.

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Lower tendon stiffness in very old compared with old individuals is unaffected by short-term resistance training of skeletal muscle

Journal of Applied Physiology ◽

10.1152/japplphysiol.00028.2018 ◽

2018 ◽

Vol 125 (1) ◽

pp. 205-214 ◽

Cited By ~ 1

Author(s):

Christian Skou Eriksen ◽

Cecilie Henkel ◽

Rene B. Svensson ◽

Anne-Sofie Agergaard ◽

Christian Couppé ◽

...

Keyword(s):

Physical Activity ◽

Mechanical Properties ◽

Resistance Training ◽

Patellar Tendon ◽

Cross Sectional ◽

Tendon Stiffness ◽

Very Old ◽

Reduced Physical Activity ◽

Heavy Resistance Training

Aging negatively affects collagen-rich tissue, like tendons, but in vivo tendon mechanical properties and the influence of physical activity after the 8th decade of life remain to be determined. This study aimed to compare in vivo patellar tendon mechanical properties in moderately old (old) and very old adults and the effect of short-term resistance training. Twenty old (9 women, 11 men, >65 yr) and 30 very old (11 women, 19 men, >83 yr) adults were randomly allocated to heavy resistance training (HRT) or no training (CON) and underwent testing of in vivo patellar tendon (PT) mechanical properties and PT dimensions before and after a 3-mo intervention. Previous measurements of muscle properties, blood parameters, and physical activity level were included in the analysis. Data from 9 old HRT, 10 old CON, 14 very old CON, and 12 old HRT adults were analyzed. In addition to lower quadriceps muscle strength and cross-sectional area (CSA), we found lower PT stiffness and Young’s modulus ( P < 0.001) and a trend toward the lower mid-portion PT-CSA ( P = 0.09) in very old compared with old subjects. Daily step count was also lower in very old subjects ( P < 0.001). Resistance training improved muscle strength and cross-sectional area equally in old and very old subjects ( P < 0.05) but did not affect PT mechanical properties or dimension. We conclude that PT material properties are reduced in very old age, and this may likely be explained by reduced physical activity. Three months of resistance training however, could not alter PT mechanical properties in very old individuals. NEW & NOTEWORTHY This research is the first to quantify in vivo tendon mechanical properties in a group of very old adults in their eighties. Patellar tendon stiffness was lower in very old (87 yr on average) compared with moderately old (68 yr on average) individuals. Reduced physical activity with aging may explain some of the loss in tendon stiffness, but regular heavy resistance training for 3 mo was not sufficient to change tendon mechanical properties.

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Habitual loading results in tendon hypertrophy and increased stiffness of the human patellar tendon

Journal of Applied Physiology ◽

10.1152/japplphysiol.90361.2008 ◽

2008 ◽

Vol 105 (3) ◽

pp. 805-810 ◽

Cited By ~ 159

Author(s):

C. Couppé ◽

M. Kongsgaard ◽

P. Aagaard ◽

P. Hansen ◽

J. Bojsen-Moller ◽

...

Keyword(s):

Mechanical Properties ◽

Patellar Tendon ◽

Cross Sectional Area ◽

Isometric Contractions ◽

Sectional Area ◽

Cross Sectional ◽

Strength Difference ◽

Distal Tendon

The purpose of this study was to examine patellar tendon (PT) size and mechanical properties in subjects with a side-to-side strength difference of ≥15% due to sport-induced loading. Seven elite fencers and badminton players were included. Cross-sectional area (CSA) of the PT obtained from MRI and ultrasonography-based measurement of tibial and patellar movement together with PT force during isometric contractions were used to estimate mechanical properties of the PT bilaterally. We found that distal tendon and PT, but not mid-tendon, CSA were greater on the lead extremity compared with the nonlead extremity (distal: 139 ± 11 vs. 116 ± 7 mm2; mid-tendon: 85 ± 5 vs. 77 ± 3 mm2; proximal: 106 ± 7 vs. 83 ± 4 mm2; P < 0.05). Distal tendon CSA was greater than proximal and mid-tendon CSA on both the lead and nonlead extremity ( P < 0.05). For a given common force, stress was lower on the lead extremity (52.9 ± 4.8 MPa) compared with the nonlead extremity (66.0 ± 8.0 MPa; P < 0.05). PT stiffness was also higher in the lead extremity (4,766 ± 716 N/mm) compared with the nonlead extremity (3,494 ± 446 N/mm) ( P < 0.05), whereas the modulus did not differ (lead 2.27 ± 0.27 GPa vs. nonlead 2.16 ± 0.28 GPa) at a common force. These data show that a habitual loading is associated with a significant increase in PT size and mechanical properties.

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Does knee joint cooling change in vivo patellar tendon mechanical properties?

European Journal of Applied Physiology ◽

10.1007/s00421-016-3444-5 ◽

2016 ◽

Vol 116 (10) ◽

pp. 1921-1929 ◽

Cited By ~ 10

Author(s):

Luis M. Alegre ◽

Michael Hasler ◽

Sebastian Wenger ◽

Werner Nachbauer ◽

Robert Csapo

Keyword(s):

Mechanical Properties ◽

Knee Joint ◽

Patellar Tendon

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Effects of Cyclic Stress on the Mechanical Properties of Cultured Collagen Fascicles from the Rabbit Patellar Tendon

Journal of Biomechanical Engineering ◽

10.1115/1.1634286 ◽

2003 ◽

Vol 125 (6) ◽

pp. 893-901 ◽

Cited By ~ 21

Author(s):

Ei Yamamoto ◽

Susumu Tokura ◽

Kozaburo Hayashi

Keyword(s):

Mechanical Properties ◽

Tensile Strength ◽

Patellar Tendon ◽

Control Level ◽

Quadratic Function ◽

Peak Stress ◽

Cyclic Stress ◽

Original Strength

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.

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Dynamics of the Tracheal Airway and Its Influences on Respiratory Airflows: An Exemplar Study

Journal of Biomechanical Engineering ◽

10.1115/1.4043723 ◽

2019 ◽

Vol 141 (11) ◽

Cited By ~ 1

Author(s):

Bora Sul ◽

Talissa Altes ◽

Kai Ruppert ◽

Kun Qing ◽

Daniel S. Hariprasad ◽

...

Keyword(s):

Morphological Changes ◽

Minute Ventilation ◽

Correlation Coefficients ◽

Dynamic Imaging ◽

Imaging Data ◽

Cross Sectional ◽

Mild Conditions ◽

Large Airways ◽

Magnetic Resonance Imaging Mri

Respiration is a dynamic process accompanied by morphological changes in the airways. Although deformation of large airways is expected to exacerbate pulmonary disease symptoms by obstructing airflow during increased minute ventilation, its quantitative effects on airflow characteristics remain unclear. Here, we used in vivo dynamic imaging and examined the effects of tracheal deformation on airflow characteristics under different conditions based on imaging data from a single healthy volunteer. First, we measured tracheal deformation profiles of a healthy lung using magnetic resonance imaging (MRI) during forced exhalation, which we simulated to characterize the subject-specific airflow patterns. Subsequently, for both inhalation and exhalation, we compared the airflows when the modeled deformation in tracheal cross-sectional area was 0% (rigid), 33% (mild), 50% (moderate), or 75% (severe). We quantified differences in airflow patterns between deformable and rigid airways by computing the correlation coefficients (R) and the root-mean-square of differences (Drms) between their velocity contours. For both inhalation and exhalation, airflow patterns were similar in all branches between the rigid and mild conditions (R > 0.9; Drms < 32%). However, airflow characteristics in the moderate and severe conditions differed markedly from those in the rigid and mild conditions in all lung branches, particularly for inhalation (moderate: R > 0.1, Drms < 76%; severe: R > 0.2, Drms < 96%). Our exemplar study supports the use of a rigid airway assumption to compute flows for mild deformation. For moderate or severe deformation, however, dynamic contraction should be considered, especially during inhalation, to accurately predict airflow and elucidate the underlying pulmonary pathology.

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Imaging

10.1093/med/9780190607166.003.0002 ◽

2017 ◽

Author(s):

Robert Laureno

Keyword(s):

Resonance Imaging ◽

Cross Sectional ◽

Advantages And Disadvantages ◽

Mri Scans ◽

Cross Sectional Imaging ◽

Magnetic Resonance Imaging Mri ◽

Cellular Pathology ◽

Brain And Spinal Cord ◽

The Brain

This chapter on “Imaging” examines the relative advantages and disadvantages of computed tomography (CT) and magnetic resonance imaging (MRI) scans. It compares the modalities to each other and to gross neuropathology. For several decades, neurologists have been able to view cross-sectional images of living patients. Analogous to gross neuropathology, cross-sectional imaging displays the brain as an entire organ but does not demonstrate microscopic tissue or cellular pathology. By allowing practitioners to view sections of brain and spinal cord in vivo, imaging has improved neurologic practice and facilitated clinical research. This chapter deals with imaging topics that are important to the neurologist. The timing of scans, the effects of gravity, and the importance of plane of section are considered. Imaging is compared to gross neuropathology, and MRI is compared to CT.

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