Effects of triceps surae muscle strength and tendon stiffness on the reactive dynamic stability and adaptability of older female adults during perturbed walking

Gaspar Epro*, Christopher McCrum, Andreas Mierau, Michael Leyendecker, Gert-Peter Brueggemann, Kiros Karamanidis

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Abstract

This study aimed to examine whether the triceps surae (TS) muscle-tendon unit (MTU) mechanical properties affect gait stability and its reactive adaptation potential to repeated perturbation exposure in older adults. Thirty-four older adults each experienced eight separate unexpected perturbations during treadmill walking, while a motion capture system was used to determine the margin of stability (MoS) and base of support (BoS). Ankle plantar flexor muscle strength and Achilles tendon (AT) stiffness were analyzed using ultrasonography and dynamometry. A median split and separation boundaries classified the subjects into two groups with GroupStrong (n = 10) showing higher ankle plantar flexor muscle strength (2.26 +/- 0.17 vs. 1.47 +/- 0.20 N center dot m/kg, means +/- SD: P <0.001) and AT stiffness (544 +/- 75 vs. 429 +/- 86 N/mm; P = 0.004) than GroupWeak in = 12). The first perturbation caused a negative Delta MoS (MoS in relation to unperturbed baseline walking) at touchdown of perturbed step (Pert(R)), indicating an unstable position. GroupStrong required four recovery steps to return to Delta MoS zero level, whereas GroupWeak was unable to return to baseline within the analyzed steps. However, after repeated perturbations, both groups increased Delta MoS at touchdown of Pert(R) with a similar magnitude. Significant correlations between Delta BoS and Delta MoS at touchdown of the first recovery step and TS MTU capacities (0.41 <r <0.57: 0.006 <P <0.048) were found. We conclude that older adults with TS muscle weakness have a diminished ability to control gait stability during unexpected perturbations, increasing their fall risk, but that degeneration in muscle strength and tendon stiffness may not inhibit the ability of the locomotor system to adapt the reactive motor response to repeated perturbations.

NEW & NOTEWORTHY Triceps surae muscle weakness and a more compliant Achilles tendon partly limit older adults' ability to effectively enlarge the base of support and recover dynamic stability after an unexpected perturbation during walking, increasing their fail risk. However, the degeneration in muscle strength and tendon stiffness may not inhibit the ability of the locomotor system to adapt the reactive motor response to repeated perturbations.

Original languageEnglish
Pages (from-to)1541-1549
Number of pages9
JournalJournal of Applied Physiology
Volume124
Issue number6
DOIs
Publication statusPublished - Jun 2018

Keywords

  • aging
  • falls
  • margin of stability
  • muscle strength
  • tendon stiffness
  • ACHILLES-TENDON
  • MORPHOLOGICAL PROPERTIES
  • LOCOMOTOR STABILITY
  • SUPPORT LIMB
  • YOUNG-ADULTS
  • LIFE-SPAN
  • IN-VIVO
  • FALLS
  • RECOVERY
  • BALANCE

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