Differences in stair descent biomechanics between older fallers, older non-fallers and younger individuals.
Thijs Ackermans, Natasha Francksen, Carolyn Lees, Paulo Lisboa, Mark Hollands, Thomas O'Brien, Constantinos Maganaris
Liverpool John Moores University, Liverpool, United Kingdom


Introduction: Falls on stairs, especially during descent, are a major cause of injury and loss of independence in older people and have important financial consequences for the National Health Service (NHS) [1]. One known risk factor for falling in older age is falls history, but our understanding of the mechanisms through which risk for a future fall is increased by a previous fall is limited. The present study was set out to investigate whether older people who have experienced a prior fall adopt riskier stepping strategies and have poorer postural stability than older non-fallers and younger adults when descending stairs.


Methods: Thirty healthy older adults (16 fallers, 14 non-fallers: mean±SD: age: 70.5 ± 4.1years; body mass: 69.1 ± 15.2kg; body height: 1.68 ± 0.08m) and 20 healthy younger adults (age: 24.5 ± 3.3years; body mass: 70.1 ± 8.4kg; body height: 1.74 ± 0.06m) descended an instrumented seven-step staircase in a step-over-step manner, without using the handrail. Participants classified as fallers had experienced a non-injurious fall in the previous year. Biomechanical parameters were quantified from three descents and included: ankle, knee and hip joint moment contributions; cadence; Centre of mass (CoM) angular acceleration with respect to the stance foot; foot clearance; the product of foot overhang and foot angle relative to the step; CoM-Centre of pressure (CoP) separation; the variability within the last four parameters. A one-way ANOVA followed by Bonferroni post hoc testing was used to identify differences between groups for each variable (P=0.05).


Results: No differences (P>0.05) were found in any biomechanical parameter between older fallers and non-fallers (Fig. 1). Younger adults differed (P<0.05) from the older fallers in: foot clearance, foot positioning, CoM-CoP separation, variance of foot clearance and variance of foot separation (Fig. 1).

Discussion: The present study revealed two findings: A) A previous fall had no impact on stair biomechanics, indicating that the falling incidents were not severe enough to make the older fallers adopt more conservative stepping strategies. B) The younger individuals adopted a riskier stepping behaviour based on the findings of: a decreased foot clearance, larger mean values and variance in foot overhang and foot angle (increasing the risk for a slip) and a greater CoM-CoP separation (indicating a diminished dynamic stability) (Fig. 1). This may indicate that younger adults have control mechanisms that allow them to confidently execute the stair descent in this risky manner. One such control mechanism identified is a decreased variability in foot clearance [2]. More work is needed to identify biomechanical factors that can differentiate individuals at risk for a stair fall so that targeted cost-saving interventions can be delivered timely.


References: [1] Startzell, (2000) Am Geriatr Soc, 48:567-580; [2] Hamel, (2005) Gait Posture, 21:135-40.