Aging and the effects of a half marathon on Achilles tendon force-elongation relationship.
OBJECTIVE
We aimed to determine whether there are different changes in Achilles tendon (AT) mechanical properties in middle-aged, compared to younger runners that might indicate that tendon fatigue, induced by long-distance running, is age-dependent.


METHODS
27 middle-aged (50-67 years) and 22 younger (21-29 years) participants ran a 21 km route at their own pace (mean and SD: old: 3.1 ± 0.3 m s-1; young: 3.6 ± 0.5 m s-1). We tested for changes in the AT force-elongation relationship using dynamometry and ultrasonography during isometric voluntary ankle plantarflexion ramp contractions, conducted 20-28 h pre-run, immediately pre-run, immediately post-run and 20-28 h post-run. Stride frequency and number were examined to estimate cyclic tensile loading characteristics of the tendon during running.


RESULTS
Muscle strength decreased significantly (P < 0.05) in both groups immediately post-run (old: 17 %; young: 11 %) and recovered to baseline within 20-28 h post-run. AT stiffness did not change for the younger adults, whereas the middle-aged adults showed a significant (P < 0.05) decrease in AT stiffness (22 %). However, tendon stiffness recovered to baseline 20-28 h post-run. Middle-aged, compared to young adults, demonstrated significantly (P < 0.05) greater stride frequency and number, but no correlations with tendon fatigue changes were determined (R2≤ 0.038).


CONCLUSIONS
The results suggest that the plasticity of the AT in response to short-term mechanical loading may be age dependent and that the AT length-tension properties of middle-aged runners may be more vulnerable to change following running compared to younger athletes. However, the observed AT changes in the middle-aged runners dissipated within 20-28 h post-run, suggesting that a tendon viscoelastic recovery mechanism may occur in vivo.
Institute of Movement and Sport Gerontology, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany.|Department of Human Movement Science, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Universiteitssingel 60, 6229 ER, Maastricht, The Netherlands.
Thijs Maria Anne
TM
Ackermans
Institute of Movement and Sport Gerontology, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany.|Institute of Biomechanics and Orthopaedics, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany.
Gaspar
G
Epro
Institute of Movement and Sport Gerontology, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany.|Department of Human Movement Science, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Universiteitssingel 60, 6229 ER, Maastricht, The Netherlands.
Christopher
C
McCrum
Fresenius University of Applied Sciences, Media School, Im Mediapark 4C, 50670, Cologne, Germany.
Kai Daniel
KD
Oberländer
Department of Molecular and Cellular Sport Medicine, Institute of Cardiovascular Research and Sport Medicine, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany.
Frank
F
Suhr
Department of Human Movement Science, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Universiteitssingel 60, 6229 ER, Maastricht, The Netherlands.
Maarten Robert
MR
Drost
Department of Human Movement Science, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University Medical Centre+, Universiteitssingel 60, 6229 ER, Maastricht, The Netherlands.
Kenneth
K
Meijer
Institute of Movement and Sport Gerontology, German Sport University Cologne, Am Sportpark Müngersdorf 6, 50933, Cologne, Germany. karamanidis@dshs-koeln.de.
Kiros
K
Karamanidis
D000125:Achilles Tendon / Q000033:anatomy & histology / Q000502:physiology*; D000328:Adult; D000368:Aged; D000375:Aging / Q000473:pathology / Q000502:physiology*; D003198:Computer Simulation; D055119:Elastic Modulus / Q000502:physiology; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D010807:Physical Endurance / Q000502:physiology*; D012420:Running / Q000502:physiology*; D013314:Stress, Mechanical; D013718:Tensile Strength / Q000502:physiology; D055815:Young Adult
Age; Mechanical loading; Muscle contraction; Running; Tendon fatigue; Tendon stiffness
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