Estimates of in vivo Achilles tendon (AT) force are needed to measure tendon mechanical properties as a function of the measured net ankle joint torque, and to understand AT function using musculoskeletal modeling approaches. The AT moment arm is required to convert the measured external ankle
Steven J. Obst, Lee Barber, Ashton Miller and Rod S. Barrett
Katherine Histen, Julia Arntsen, Lauren L’Hereux, James Heeren, Benjamin Wicki, Sterling Saint, Giselle Aerni, Craig R. Denegar and Michael F. Joseph
Tendon adapts to load through alterations in its composition and mechanical properties. Mechanical adaptation to increased load often involves increases in cross-sectional area (CSA), stiffness, and modulus. Runners exhibit these adaptations.
To determine if runners wearing minimalist shoes had larger and stiffer Achilles tendons (AT) than traditionally shod runners.
Cross-sectional study of well-trained, traditionally and minimally shod runners.
Laboratory assessment of trained runners.
23 men (11 traditional, 12 minimalist) and 8 women (6 traditional, 2 minimalist). Runners wearing minimalist shoes had 4.2 ± 1.6 y of training experience in minimalist shoes.
Main Outcome Measures:
The authors used diagnostic ultrasound and isokinetic dynamometry to generate a force-elongation curve and its derivatives.
Minimalist runners had a greater CSA: mean difference (MD) = 9.2 mm2, stiffness (MD = 268.1 N/mm), and modulus (MD = 202.9 MPa). ATs of minimalist runners experienced greater stress (MD 8.6 N/mm2) during maximal voluntary isometric contraction of the plantar-flexor muscles due to greater force of contraction (MD 798.9 N).
The AT in minimalist runners adapts by increasing size, stiffness, and modulus, which is consistent with our understanding of mechanical adaptation of tendon to increased loading. Increased stress to the AT likely requires a slow transition to minimalist running to allow the AT to adapt without evidence of injury.
Sabrina S.M. Lee, Gregory S. Lewis and Stephen J. Piazza
The accuracy of an algorithm for the automated tracking of tendon excursion from ultrasound images was tested in three experiments. Because the automated method could not be tested against direct measurements of tendon excursion in vivo, an indirect validation procedure was employed. In one experiment, a wire “phantom” was moved a known distance across the ultrasound probe and the automated tracking results were compared with the known distance. The excursion of the musculotendinous junction of the gastrocnemius during frontal and sagittal plane movement of the ankle was assessed in a single cadaver specimen both by manual tracking and with a cable extensometer sutured to the gastrocnemius muscle. A third experiment involved estimation of Achilles tendon excursion in vivo with both manual and automated tracking. Root mean squared (RMS) error was calculated between pairs of measurements after each test. Mean RMS errors of less than 1 mm were observed for the phantom experiments. For the in vitro experiment, mean RMS errors of 8–9% of the total tendon excursion were observed. Mean RMS errors of 6–8% of the total tendon excursion were found in vivo. The results indicate that the proposed algorithm accurately tracks Achilles tendon excursion, but further testing is necessary to determine its general applicability.
Stephen J. Pearson, Tim Ritchings and Ahmad S.A. Mohamed
The work describes an automated method of tracking dynamic ultrasound images using a normalized cross-correlation algorithm, applied to the patellar and gastrocnemius tendon. Displacement was examined during active and passive tendon excursions using B-mode ultrasonography. In the passive test where two regions of interest (2-ROI) were tracked, the automated tracking algorithm showed insignificant deviations from relative zero displacement for the knee (0.01 ± 0.04 mm) and ankle (–0.02 ± 0.04 mm) (P > .05). Similarly, when tracking 1-ROI the passive tests showed no significant differences (P > .05) between automatic and manual methods, 7.50 ± 0.60 vs 7.66 ± 0.63 mm for the patellar and 11.28 ± 1.36 vs 11.17 ± 1.35 mm for the gastrocnemius tests. The active tests gave no significant differences (P > .05) between automatic and manual methods with differences of 0.29 ± 0.04 mm for the patellar and 0.26 ± 0.01 mm for the gastrocnemius. This study showed that automatic tracking of in vivo displacement of tendon during dynamic excursion under load is possible and valid when compared with the standardized method. This approach will save time during analysis and enable discrete areas of the tendon to be examined.
Laura C. Slane, Stijn Bogaerts, Darryl G. Thelen and Lennart Scheys
Chronic tendon injuries, such as tendinopathy, commonly occur in energy-storing tendons and can have a high socioeconomic impact on the general population, both in terms of lost work and the effects on normal daily living. 1 Intriguingly, tendinopathies often arise in consistent locations
Feng-Hua Tsai, I-Hua Chu, Chun-Hao Huang, Jing-Min Liang, Jia-Hroung Wu and Wen-Lan Wu
The Achilles tendon is located at the back of the ankle and is important for various human activities, such as walking and running. 1 Most tendons in the foot and ankle bear a maximum load of about 30 megapascal (MPa) during human activity, but the Achilles tendon load is about 67 MPa 2 and
Jared R. Fletcher and Brian R. MacIntosh
Direct measurement of muscle forces in vivo is highly invasive, 1 so muscle forces are typically estimated from measurement of joint moments. 2 , 3 Estimating muscle forces from joint moments requires knowledge of the muscle/tendon moment arm, that is, the perpendicular distance from the joint
Kenneth Färnqvist, Stephen Pearson and Peter Malliaras
Tendinopathy is a general term indicating any abnormal state of a tendon, including pain, dysfunction, and, but not necessarily, pahology. 1 , 2 Pathological tendons are defined as having abnormal changes on imaging (eg, increased signal intensity on magnetic resonance imaging [MRI] or hypoechoic
Josep C. Benítez-Martínez, Pablo Martínez-Ramírez, Fermín Valera-Garrido, Jose Casaña-Granell and Francesc Medina-Mirapeix
) and abnormal vascular structures (neovascularization [NV]), detected with Doppler ultrasound, have been shown to be an important source of patellar tendon pain. 5 – 7 In cases of tendinopathy, several histological findings have been suggested to be the cause of the changes observed in the pathology
Carly C. Sacco, Erin M. Gaffney and Jesse C. Dean
. While less well studied than tactile enhancement, stochastic resonance can also be used to enhance muscle proprioceptive feedback. Early human 19 and animal 20 experiments found that white noise tendon vibration increases the stretch-sensitivity of muscle spindles embedded in the vibrated