Walking is an essential motor skill used during the activities of daily life. There are factors that can affect an individual’s stability during locomotion which should be considered when determining the risk and probability of sustaining an injury due to a slip, trip, or fall. The mechanisms of walking and gait control can be disrupted by certain neurological diseases or aging, resulting in increased gait unsteadiness and risk of falling (Figure 1).
Every year, over one-third of adults over the age of 65 fall.  Trips and slips are the most common causes of falling, accounting for up to 60% of all falls.  Research has found that as we age, our gait changes. Older people reduce their speed and stride length, increase their step width, reduce the joint range of motion, and typically walk with a more stooped posture.  It is generally assumed that these changes are adaptive and lead to an increase in stability during walking. Additionally, older individuals may experience reduced vision, increased reaction times, and other cognitive impairments, all of which increase the probability of slipping or tripping.
In humans, recovery from a loss of balance due to slipping or tripping relies on a rapid and effective protective step either behind or in front of the center of mass.  People tend to increase the step length and generate a strong push-off in the recovery foot in order to recover balance after a trip;  however, fall avoidance after a slip is dependent upon arresting the motion of the slipping foot and rapidly lowering the non-slipping limb to the ground behind the center of mass.  Recovery of balance after a slip or a trip becomes more limited as we age. Initially, people tend to lean forward due to stooped posture and have a reduction in joint movement which further decreases their ability to swing the recovery leg in order to take a large step. Additionally, decreases in muscular strength and delayed responses in generating adequate muscular forces to push off the recovery foot contribute to the overall increased risk of falling as we age. 
Considering the increased risk of falling associated with age, it is important to examine the conditions in which the fall occurred and to keep in mind that older individuals are more susceptible to slips and trips and are less likely to recover their balance, which may ultimately result in a fall. Furthermore, older individuals are more likely to sustain a severe injury when compared to a young individual due to increased fragility and reduced elasticity of bone, muscle, and ligament in an older individual.
Karla Cassidy is a Senior Engineer in J.S. Held's Accident Reconstruction Practice. Ms. Cassidy has been an active member in the biomechanics community since 2006 and in the accident reconstruction industry since 2010. Her expertise spans both biomechanical and mechanical engineering. She has been involved in hundreds of cases involving vehicles, pedestrians, motorcycles, farm equipment, and cyclists. Her specialty areas are biomechanics, personal injury, injury probability, seatbelt usage, slip, trip and falls, and determination of occupant position. Ms. Cassidy also conducts collision reconstruction and damage consistency analyses. She is a published author and has provided litigation support.
Karla can be reached at [email protected] or +1 416 977 0009.
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