Effects of aging on the biomechanics of slips and falls

Abstract

Although much has been learned in recent decades about the deterioration of muscular strength, gait adaptations, and sensory degradation among older adults, little is known about how these intrinsic changes affect biomechanical parameters associated with slip-induced fall accidents. In general, the objective of this laboratory study was to investigate the process of initiation, detection, and recovery of inadvertent slips and falls. We examined the initiation of and recovery from foot slips among three age groups utilizing biomechanical parameters, muscle strength, and sensory measurements. Forty-two young, middle-age, and older participants walked around a walking track at a comfortable pace. Slippery floor surfaces were placed on the track over force platforms at random intervals without the participants' awareness. Results indicated that younger participants slipped as often as the older participants, suggesting that the likelihood of slip initiation is similar across all age groups; however, older individuals' recovery process was much slower and less effective. The ability to successfully recover from a slip (thus preventing a fall) is believed to be affected by lower extremity muscle strength and sensory degradation among older individuals. Results from this research can help pinpoint possible intervention strategies for improving dynamic equilibrium among older adults.

Figure 1

The process of initiation, detection, and recovery of inadvertent slips and falls with possible causes and effects.

Figure 2

Field layout of the experiment, including fall-arresting rig, potentiometer interfaced with the LabView system, safety harness, force platforms, optoelectric switch, CCD cameras (4), AG 6300 VCR (4), and remote control floor changer (RCFC) units with baseline carpet floor material.

Figure 3

Locations of marker placements and internal landmarks used to generate whole-body center of mass and calculations of slip parameters.

Figure 4

Composite view of the slip parameters. Adapted with permission from STP 1424 Metrology of Pedestrian Locomotion and Slip Resistance, copyright ASTM International, 100 Barr Harbor Dr., West Conshohocken, PA 19428 (Lockhart et al., 2002).

Figure 5

Heel velocity profiles of young (left panel), middle (middle panel), and older (right panel) age groups (116 ms before and 116 ms after heel contact). Each tick marker (frame) represents 1/60 s. Heel contact was defined as the time when the vertical ground reaction force exceeded 10 N. The darker lines represent averages of heel contact velocities in each of the age groups.

Figure 6

Sliding heel velocity profiles of three age groups (116 ms before and 116 ms after heel contact). Each tick marker (frame) represents 1/60 s. Heel contact was defined as the time when the vertical ground reaction force exceeded 10 N. The darker lines represent averages of sliding heel velocities in each of the age groups.

Figure 7

Relationship between distance slipped and sensory organization scores of each participants (r = −.49). In general, individuals with lower SOT scores slipped farther.

Figure 8

The relationship between muscle latency times and distances slipped (r = .2). In general, individuals with longer muscle latency times slipped farther.

Figure 9

The relationship between SOT scores and MCT times (r = −.51). In general, individuals with higher SOT scores took less time to actively respond to the support surface movements.

Figure 10

The relationship between maximal isometric leg strength and distance slipped (r = −0.57). In general, individuals with stronger lower extremities slipped less.

Figure 11

Illustration of actual slip distances and predicted slip distances. The prediction model further suggests that the vision, reaction time, and muscle strength (lower extremity) were important for determining slip distances.