Feet kinematics upon slipping discriminate between recoveries and three types of slip-induced falls

Abstract

This study investigated the relationship between feet kinematics upon slipping while walking and the outcome of the slip. Seventy-one slips (induced by walking over an unexpectedly slippery surface) were analysed, which included 37 recoveries, 16 feet-split falls, 11 feet-forward falls and seven lateral falls. Feet kinematics differed between recoveries and three types of slip-induced falls, and a discriminant model including six measures of feet kinematics correctly predicted 87% of slip outcomes. Two potentially modifiable characteristics of the feet kinematics upon slipping that can improve the likelihood of successfully averting a fall were identified: (1) quickly arresting the motion of the slipping foot and (2) a recovery step that places the trailing toe approximately 0-10% body height anterior to the sacrum. These results may inform the development of task-specific balance training interventions that promote favourable recovery responses to slipping. Practitioner Summary: This study investigated the relationship between feet movements upon slipping and outcomes of the slip. Potentially modifiable characteristics that can reduce the likelihood of falling were: (1) quickly arresting slipping foot motion and (2) a recovery step that places the trailing toe approximately 0-10% body height anterior to the sacrum.

Perturbation-based balance training targeting both slip- and trip-induced falls among older adults: a randomized controlled trial

“…Walking trials with speeds outside of this range were discarded and repeated. After a minimum of 10 trials, participants were exposed to a slip or trip using methods described earlier [9,28,29]. In brief, slips were induced by spreading a thin layer of vegetable oil over a 0.9 × 0.9 m section of the walkway while participants were facing away, and slips occurred when the heel of the dominant foot contacted the oil.…”

“…2). Both of these actions are critical to prevent a fall after slipping while walking [9]. Training was individualized to participant capability as evaluated qualitatively and visually by the investigator (LJA) administering training.…”

“…We estimated a necessary sample size of 36 participants (equally split between intervention groups) using PBT effect sizes reported elsewhere for clinically-relevant reductions in peak trunk angle after tripping (Cohen's d = − 1.24) [19], and slip speed after slipping (d = − 1.59) [21]. These differences were considered clinicallyrelevant, based on the anchor-based method for determining minimal clinically important difference [38], given that they were comparable to effect sizes between falls and recoveries after laboratory-induced trips [39] and slips [9] reported elsewhere. Using G*Power [40] for an independent t-test, and specifying 80% power and a one-sided Type I error rate of 5%, a sample size of nine participants per group was necessary.…”

“…PBT, when tailored to mimic common fall scenarios such as slipping or tripping, is a form of task-specific training that leverages motor learning principles by allowing participants to practice reactive responses in a safe, controlled setting [5]. Slips commonly occur at heel strike when the friction required for walking exceeds the friction available between the foot and floor [8], and typically result in a backwards loss of balance [9]. Examples of PBT for slipping have involved repeated exposure to slips while walking over a sliding platform [6], or a structured step-training regimen onto a low-friction surface [10].…”

An alternative method for analyzing the slip potential of workers on sloped surfaces

“…The shear force can be either a traction force (in the walking direction) or a resistant force (opposite to walking direction); hence, the slip could occur in any direction with the maximum ratio of the shear force and normal force. While a minor slip for a short period of time may not result in a fall, a major slip may lead to a fall if the slip results in the loss of body balance and it cannot be recovered during the slip reaction (Hanson et al, 1999;Redfern et al, 2001;Allin et al, 2018).…”