Graduate Research Assistant , University of Pittsburgh
The hand-rung force required to recover with a ladder after a ladder climbing misstep
Falls are a leading cause of accidental deaths worldwide. The majority of fatal fall injuries are to lower levels (i.e. fall from a ladder), compared to falls that occur at the same level (i.e. fall from a ground level slip). Of fatal falls to lower levels, ladders are the main cause of these falls. To reduce the number of fatal fall injuries, my research focuses on understanding mechanisms that contribute to a ladder fall. This is done by studying ladder climbing biomechanics through a motion capture system and custom designed ladders. The motion capture system measures the ladder climbing kinematics, and the custom designed ladders capture the forces being loaded onto the ladder to measure the climbing kinetics. In addition, the custom designed ladders simulate a slip or misstep perturbation. Simulating a climbing perturbation allows us to determine ladder climbing biomechanics that lead to a ladder slip and the biomechanics that promote recovery with the ladder after a perturbation to prevent the falling event from resulting into a fall. Knowledge gained from my research on mechanisms that contribute to a ladder fall can be used for ladder climbing interventions that reduce the number of ladder fall injuries. Specifically, this knowledge can be used to improve ladder safety guidelines, promote safer ladder designs, and develop ladder climbing training program. The findings I will be presenting at the 41st Annual Meeting of the American Society of Biomechanics is on the applied hand-rung force after a simulated ladder climbing misstep perturbation. The key findings from this research support a horizontal cylinder handhold design to achieve necessary forces to recover with the ladder after a climbing perturbation, and increase the understanding on the interaction between the upper and lower body kinetics during a ladder falling event. The broader impact of disseminating these findings can lead to a ladder climbing intervention that promotes a safer handhold design to reduce the number of ladder fall injuries.
Abstract: Ladder falling accidents are a significant, growing and severe occupational hazard. The factors that contribute to falls from ladders and specifically those that influence the motor response from ladder falls are not well understood. The aims of this research were to determine the effects of hand placement (rung versus rail) on muscle activation onset and peak activity timing in response to slipping on a ladder and to sequence the timing of events following slip initiation. Fifteen unexpected slips from 11 experienced ladder climbers were induced with a freely spinning rung under the foot, while subjects were randomly assigned to a rung versus rail hand grasping strategy. EMG onset time and peak activity time from five bilateral muscles (semitendinosis, vastus lateralis, triceps, biceps and anterior deltoid) were analyzed. Results indicated that significantly slower muscle activation onset and peak response times occurred during rail hand placement, suggesting that grasping ladder rungs may be preferable for improving the speed of the motor response. The triceps muscle activated and reached peak activity earlier in the slip indicating that subjects may initially extend their arms prior to generating hand forces. The study also revealed that slips tended to occur around the time that a foot and hand were in motion and there were just two points of contact (one hand and the slipping foot).
Pub.: 04 Oct '15, Pinned: 27 Jun '17
Abstract: Publication date: April 2017 Source:Applied Ergonomics, Volume 60 Author(s): Erika M. Pliner, Na Jin Seo, Kurt E. Beschorner Ladder falls cause many fatal injuries. The factors that affect whether a ladder perturbation leads to a fall are not well understood. This study quantified the effects of several factors on a person's ability to recover from a ladder perturbation. Thirty-five participants each experienced six unexpected ladder missteps, for three glove conditions (bare hands, high friction, low friction) and two climbing directions (ascent, descent). Fall severity was increased during ladder descent (p < 0.001). Gloves did not affect fall severity. Females compared to males had greater fall severity during ascent (p < 0.001) and descent (p = 0.018). During ascent, females had greater fall severity during the second perturbation but similar fall severity to males during the other perturbations. Additional protection may be needed when descending a ladder. Also, females may benefit from targeted interventions like training. This study does not suggest that gloves are effective for preventing ladder falls.
Pub.: 14 Dec '16, Pinned: 27 Jun '17
Abstract: This study developed biomechanical models for hand breakaway strength that account for not only grip force but also hand-handle frictional coupling in generation of breakaway strength. Specifically, models for predicting breakaway strength for two commonly-used handle shapes (circular and rectangular handles) and varying coefficients of friction (COF) between the hand and handle were proposed. The models predict that (i) breakaway strength increases with increasing COF and (ii) a circular handle with a 50.8 mm-diameter results in greater mean breakaway strength than a handle with a rectangular cross-section of 38.1 by 38.1 mm for COFs greater than 0.42. To test these model predictions, breakaway strengths of thirteen healthy young adults were measured for three frequently-encountered COF conditions (represented by three glove types of polyester (COF=0.32), bare hand (COF=0.50), and latex (COF=0.74) against an aluminum handle) and for the two handle shapes. Consistent with the model predictions, mean breakaway strength increased with increasing COF and was greater for the circular than rectangular handle for COFs of 0.50 and 0.74. Examination of breakaway strength normalized to body weight reveals that modification of COF and handle shapes could influence whether one can hold his/her body using the hands or not (thus must fall), highlighting the importance of considering these parameters for fall prevention. The biomechanical models developed herein have the potential to be applied to general handle shapes and COF conditions. These models can be used to optimize handle design to maximize breakaway strength and minimize injuries due to falls from ladders or scaffolds.
Pub.: 28 Jan '12, Pinned: 27 Jun '17