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Research Papers

Age-Related Effect of Static and Cyclic Loadings on the Strain-Force Curve of the Vastus Lateralis Tendon and Aponeurosis

[+] Author and Article Information
Lida Mademli

Institute of Biomechanics and Orthopaedics, German Sport University Cologne, Carl-Diem-Weg 6, D-50933 Cologne, Germany

Adamantios Arampatzis1

Institute of Biomechanics and Orthopaedics, German Sport University Cologne, Carl-Diem-Weg 6, D-50933 Cologne, Germanyarampatzis@dshs-koeln.de

Mark Walsh

Department of Physical Education, Health and Sport Studies, Miami University, Oxford, OH

1

Corresponding author.

J Biomech Eng 130(1), 011007 (Feb 07, 2008) (7 pages) doi:10.1115/1.2838036 History: Received October 23, 2006; Revised May 11, 2007; Published February 07, 2008

The objective of the present study was to investigate the age-related effects of submaximal static and cyclic loading on the mechanical properties of the vastus lateralis (VL) tendon and aponeurosis in vivo. Fourteen old and 12 young male subjects performed maximal voluntary isometric knee extensions (MVC) on a dynamometer before and after (a) a sustained isometric contraction at 25% MVC and (b) isokinetic contractions at 50% isokinetic MVC, both until task failure. The elongation of the VL tendon and aponeurosis was examined using ultrasonography. To calculate the resultant knee joint moment, the kinematics of the leg were recorded with eight cameras (120Hz). The old adults displayed significantly lower maximal moments but higher strain values at any given tendon force from 400N and up in all tested conditions. Neither of the loading protocols influenced the strain-force relationship of the VL tendon and aponeurosis in either the old or young adults. Consequently, the capacity of the tendon and aponeurosis to resist force remained unaffected in both groups. It can be concluded that in vivo tendons are capable of resisting long-lasting static (4.6min) or cyclic (18.5min) mechanical loading at the attained strain levels (4–5%) without significantly altering their mechanical properties regardless of age. This implies that as the muscle becomes unable to generate the required force due to fatigue, the loading of the tendon is terminated prior to provoking any significant changes in tendon mechanical properties.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Experimental setup. The subjects performed a warmup period, three MVCs, and two fatiguing protocols: (a) a sustained submaximal isometric knee extension (static loading) and (b) repetitive submaximal isokinetic concentric knee extensions (cyclic loading) until failure to hold the predefined moments. The isokinetic maximum was defined as the highest achieved moment during five consecutive maximal isokinetic contractions. After each MVC, a passive rotation of the knee joint at 5deg∕s in a range of motion of 85–180deg and two submaximal isometric knee flexion contractions were performed (for knee joint moment correction).

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Figure 2

Ultrasound images of the VL at rest (top) and at maximum tendon force (bottom). The elongation of the VL tendon and aponeurosis was defined as the distance traveled by the cross point along the visualized deeper aponeurosis during the knee extension. The marker between the skin and the ultrasound probe was used to register any motion of the probe relative to the skin during the knee extension.

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Figure 3

Mean curves for the old (n=14) and the young adults (n=12) of the measured displacement (ΔL measured) and the passive displacement due to the joint rotation (ΔL passive) of the analyzed point at the deeper aponeurosis of the VL as well as the corrected VL tendon and aponeurosis elongation considering the joint rotation (ΔL corrected) during MVC-1. Tmax: time to achieve maximal tendon force.

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Figure 4

Strain-force curves of the VL tendon and aponeurosis. The strain values at every 200N and at maximum calculated tendon force during the MVC preloading (MVC-1), after static loading (MVC-2), and after cyclic loading (MVC-3) are displayed. The curves end at 1400N for the old adults and at 1800N for the young ones; these values correspond to the maximum common force achieved by all subjects in either group, old and young adults. Y: young (n=12); O: old adults (n=14). Means and SEM;  *: age effect (p<0.05).

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Figure 5

Muscle architecture. Means and SEM of the VL pennation angle (deg), fascicle length (cm), and muscle thickness (cm) at rest (knee: 100deg, hip: 140deg) before loading (preloading), after static loading (static loading), and after cyclic loading (cyclic loading) (old n=14; young n=12). Although the old adults had smaller pennation angle and muscle thickness (p<0.05, age effect), there were no differences in the muscle architecture prior to or after mechanical loading in either group (p>0.05).

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Figure 6

Means and SEM of the ratios of the rms of the EMG signals from VL to the sum of the rms of all three muscles (VL∕total), VM to the sum of the rms of all three muscles (VM∕total), and RF to the sum of the rms of all three muscles (RF∕total) during the MVC preloading (MVC-1), after static (MVC-2), and after cyclic loading (MVC-3) (old, n=14; young, n=12).

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