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Impaired reactive stepping adjustments in older adults.

Tseng SC, Stanhope SJ, Morton SM - J. Gerontol. A Biol. Sci. Med. Sci. (2009)

Bottom Line: The purpose of the current study was to compare mechanisms of reactive stepping adjustments in young versus older adults when responding to an unexpected perturbation during voluntary step initiation.We tested 13 healthy community-dwelling older adults and an equal number of young control participants performing stepping movements onto a visual target on the floor.The decreased capability for rapidly planning and executing an effective voluntary step modification could reveal one potential cause for the increased risk of falls in the older population.

View Article: PubMed Central - PubMed

Affiliation: Department of Physical Therapy & Rehabilitation Science, University of Maryland School of Medicine, Baltimore, USA.

ABSTRACT

Background: The ability to redirect the path of the foot during walking is critical for responding to perturbations and maintaining upright stability. The purpose of the current study was to compare mechanisms of reactive stepping adjustments in young versus older adults when responding to an unexpected perturbation during voluntary step initiation.

Methods: We tested 13 healthy community-dwelling older adults and an equal number of young control participants performing stepping movements onto a visual target on the floor. In some trials, perturbations were introduced by unexpectedly shifting the target, at various time points, from its usual location to a new location 20 cm to the right. We measured ground reaction forces under the supporting leg and three-dimensional kinematics of the stepping leg in baseline and target shift trials.

Results: During target shift trials, that is, when reactive adjustments were required, older adults demonstrated the following: delayed responses in modifying the lateral propulsive forces under the supporting foot, reduced rates of lateral force production, delayed responses in modifying the stepping foot trajectory, and prolonged movement execution times.

Conclusions: The current study quantitatively distinguishes between healthy older and young adults in generating reactive stepping adjustments to an unpredictable shift of a visual target. The decreased capability for rapidly planning and executing an effective voluntary step modification could reveal one potential cause for the increased risk of falls in the older population.

Show MeSH
Stepping foot endpoint accuracy. Average step accuracy across all conditions and groups. Accuracy is depicted as the medial/lateral error in the foot endpoint position. Negative numbers indicate errors in the leftward (undershoot) direction. Error bars, ±1 SEM.
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fig2: Stepping foot endpoint accuracy. Average step accuracy across all conditions and groups. Accuracy is depicted as the medial/lateral error in the foot endpoint position. Negative numbers indicate errors in the leftward (undershoot) direction. Error bars, ±1 SEM.

Mentions: Figure 2 shows the averaged lateral stepping endpoint accuracy. As the available response time decreased, stepping errors incrementally increased (condition effect, F(3,22) = 13.86, p < .001). Stepping errors in the middle and late conditions were both significantly larger than those in the others (post hoc, both p ≤ .001). Although there was a visible trend for the older group to show increased stepping errors, particularly in the later target shift conditions, there were no significant differences between groups (F(1,24) = 0.39, p = .54) and no interaction effect (F(3,22) = 0.65, p = .59).


Impaired reactive stepping adjustments in older adults.

Tseng SC, Stanhope SJ, Morton SM - J. Gerontol. A Biol. Sci. Med. Sci. (2009)

Stepping foot endpoint accuracy. Average step accuracy across all conditions and groups. Accuracy is depicted as the medial/lateral error in the foot endpoint position. Negative numbers indicate errors in the leftward (undershoot) direction. Error bars, ±1 SEM.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2691798&req=5

fig2: Stepping foot endpoint accuracy. Average step accuracy across all conditions and groups. Accuracy is depicted as the medial/lateral error in the foot endpoint position. Negative numbers indicate errors in the leftward (undershoot) direction. Error bars, ±1 SEM.
Mentions: Figure 2 shows the averaged lateral stepping endpoint accuracy. As the available response time decreased, stepping errors incrementally increased (condition effect, F(3,22) = 13.86, p < .001). Stepping errors in the middle and late conditions were both significantly larger than those in the others (post hoc, both p ≤ .001). Although there was a visible trend for the older group to show increased stepping errors, particularly in the later target shift conditions, there were no significant differences between groups (F(1,24) = 0.39, p = .54) and no interaction effect (F(3,22) = 0.65, p = .59).

Bottom Line: The purpose of the current study was to compare mechanisms of reactive stepping adjustments in young versus older adults when responding to an unexpected perturbation during voluntary step initiation.We tested 13 healthy community-dwelling older adults and an equal number of young control participants performing stepping movements onto a visual target on the floor.The decreased capability for rapidly planning and executing an effective voluntary step modification could reveal one potential cause for the increased risk of falls in the older population.

View Article: PubMed Central - PubMed

Affiliation: Department of Physical Therapy & Rehabilitation Science, University of Maryland School of Medicine, Baltimore, USA.

ABSTRACT

Background: The ability to redirect the path of the foot during walking is critical for responding to perturbations and maintaining upright stability. The purpose of the current study was to compare mechanisms of reactive stepping adjustments in young versus older adults when responding to an unexpected perturbation during voluntary step initiation.

Methods: We tested 13 healthy community-dwelling older adults and an equal number of young control participants performing stepping movements onto a visual target on the floor. In some trials, perturbations were introduced by unexpectedly shifting the target, at various time points, from its usual location to a new location 20 cm to the right. We measured ground reaction forces under the supporting leg and three-dimensional kinematics of the stepping leg in baseline and target shift trials.

Results: During target shift trials, that is, when reactive adjustments were required, older adults demonstrated the following: delayed responses in modifying the lateral propulsive forces under the supporting foot, reduced rates of lateral force production, delayed responses in modifying the stepping foot trajectory, and prolonged movement execution times.

Conclusions: The current study quantitatively distinguishes between healthy older and young adults in generating reactive stepping adjustments to an unpredictable shift of a visual target. The decreased capability for rapidly planning and executing an effective voluntary step modification could reveal one potential cause for the increased risk of falls in the older population.

Show MeSH