First published online October 7, 2005
Journal of Experimental Biology 208, 3907-3923 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01830
Mechanical and morphological properties of different muscle–tendon units in the lower extremity and running mechanics: effect of aging and physical activity
Kiros Karamanidis and
Adamantios Arampatzis*
Institute for Biomechanics and Orthopaedics, German Sport University
of Cologne, Carl-Diem-Weg 6, 50933, Cologne, Germany
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Fig. 1. Ultrasound image of the gastrocnemius medialis (GM, left) and vastus
lateralis (VL, right) at rest. L, fascicle length; T, muscle
thickness;  , pennation angle; digitized cross-point indicates insertion
of the fascicle into the deep aponeurosis.
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Fig. 3. (A) Normalized RMS values of the EMG signal for quadriceps femoris (vastus
lateralis, vastus medialis and rectus femoris) and (B) knee joint moment
during isometric maximal voluntary knee extension contraction at 11 different
joint angle configurations for the examined groups. Values are means ±
S.D. RMS values for each subject were normalised to the
highest RMS value measured over all joint angle configurations. O, older
adults; Y, young adults. Asterisks indicate statistically significant
differences between older and young adults: *P<0.05,
**P<0.01, ***P<0.001; there was no age-by-running
activity interaction for the analysed parameters (P>0.05).
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Fig. 4. Normalised stiffness of the triceps surae and quadriceps femoris tendon and
aponeurosis for the different groups. Values are means ±
S.D. O, older adults; Y, young adults. **Statistically
significant differences between older and young adults (P<0.01);
there was no age-by-running activity interaction for the analysed parameters
(P>0.05).
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Fig. 5. Average values of the limb angle (A) and sagittal plane angular motion at
the knee (B) and ankle (C) joints of the left leg during running (2.7 m
s–1) for the examined groups. O, older adults; Y, young
adults. The x-axis was normalised as follows: –200% to
–100%, flight phase before ground contact of the left leg; –100%
to 0%, ground contact of the left leg; 0% to 100%, flight phase before ground
contact of the right leg; 100% to 200%, flight phase during ground contact of
the right leg. The posterior and anterior position of the COM relative to the
midpoint of the foot in vertical direction were defined as negative and
positive limb angles, respectively.
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Fig. 6. Mean values of the mechanical power (A,B) and sagittal plane joint moment
(C,D) at the ankle (A,C) and knee joint (B,D), and vertical (E) and horizontal
(F) ground reaction force (GRF) of the left leg during running (2.7 m
s–1) for the examined groups. O, older adults; Y, young
adults. The x-axis was normalised as follows: 0% to 100%, ground
contact.
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Fig. 7. (A) Moment arm of the ground reaction force (R) and (B) gear ratio
(R/r) acting about the ankle joint during ground contact for
the examined groups. Values are means ± S.D. of
both legs. O, older adults; Y, young adults. (Phase 1, 10–26%; Phase 2,
26–42%; Phase 3, 42–58%; Phase 4, 58–74; Phase 5,
74–90% of the period of ground contact). Asterisks indicate
statistically significant differences between older and young adults:
*P<0.05, **P<0.01; there was no age-by-running
activity interaction for the analysed parameters (P>0.05).
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Fig. 8. (A) Moment arm of the ground reaction force (R) and (B) gear ratio
(R/r) acting about the knee joint during ground contact for
the examined groups. Values are means ± S.D. of
both legs. O, older adults; Y, young adults. (Phase 1, 10–26%; Phase 2,
26–42%; Phase 3, 42–58%; Phase 4, 58–74%; Phase 5,
74–90% of ground contact).  Significant differences
between runners and non-active individuals (P<0.05); there was no
age-by-running activity interaction for the analysed parameters
(P>0.05).
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Fig. 9. Rate of force generation and force generation per meter distance during
running (2.7 m s–1) for the examined groups. Values are means
± S.D. of both legs. O, older adults; Y, young
adults. Asterisks indicate statistically significant differences between older
and young adults: *P<0.05, **P<0.01; there was no
age-by-running activity interaction for the analysed parameters
(P>0.05).
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© The Company of Biologists Ltd 2005
significant age-by-running activity interaction
(P<0.05);