Strength in arms: empowering older adults against the risk of slipping and falling-a theoretical perspective.

Background: Slips and falls are a serious health concern, particularly among older adults. Current physical therapy protocols strengthen the legs to improve balance. However, arm movements help maintain balance during a slip incident. Understanding how arm movements improve balance may help clinicians develop more comprehensive fall-prevention protocols to improve patient outcomes. Clinical question: What limitations exist in current fall prevention protocols for reducing falls in older adults during slip incidents, and what new strategies can enhance these outcomes? Key results: Slip incidents often result in a sideways loss of balance, leading to hip fractures in older adults. During a slip, the legs do not produce sideways motion and are less effective in regaining balance in this direction. Contrary, the arms produce 100 + degrees of abduction and this motion reduces falls by 200%+ during a slip incident. Notably, older adults exhibit 35.7% decreased arm abduction acceleration responses compared to younger adults during a slip incident. This delay may be attributed to age-related decreases in type II fibers of the deltoid. High-velocity and ballistic training have been shown to improve the proportion and size of type II fibers as well as improve fall outcomes when focused on the lower extremities. Clinical application: Therefore, I propose incorporating arm abductor training, alongside leg exercises, as a cost-effective and low-risk intervention to enhance the slip responses in older adults. In light of its minimal risk and considerable potential benefits, starting arm abductor exercises with older adults is a sensible move.

Reactive responses of the arms increase the Margins of Stability and decrease center of mass dynamics during a slip perturbation.

Although reactive arm motions are important in recovering from a slip event, the biomechanical influences of upper extremity motions during slipping are not clear. The purpose of the current study was to determine whether reactive arm motions during slip recovery leads to increased margins of stability (MoS), and decreased center of mass (CoM) velocity and excursion. Thirty-two participants were randomized into 2 conditions: arms free and arms constrained. Participants traversed a 10-meter walkway and were exposed to an unexpected slip while wearing a protective harness. Anterior-posterior and medial-lateral MoS, as well as the CoM excursion and velocity during the slip perturbation was quantified using a three-dimensional motion capture system. In the frontal plane, individuals with their arms unconstrained demonstrated greater MoS (0.06 ± 0.03 vs -0.01 ± 0.02 m, p < 0.01), decreased CoM excursion (0.05 ± 0.02 vs 0.08 ± 0.01 m, p = 0.015), and a reduced CoM velocity (0.07 ± 0.03 vs. 0.14 ± 0.02 m/s, p < 0.01) compared to individuals with their arms constrained. In the sagittal plane, individuals with their arms unconstrained demonstrated, decreased CoM excursion (0.83 ± 0.13 vs 1.14 ± 0.20 m, p < 0.01) reduced CoM velocity (1.71 ± 0.08 vs. 1.79 ± 0.07 m/s, p = 0.02), but no differences in margins of stability (0.89 ± 0.13 vs 0.94 ± 0.10 m, p = 0.32). Our findings demonstrate that arm motions during a slip perturbation act to restore balance by minimizing displacement and velocity of the body CoM during a slip event in the frontal plane.

Obstacle clearance performance in individuals with high body mass index.

The objective of this study was to quantify performance in an obstacle clearance task among individuals with excess body weight or body mass index (BMI). Task performance was operationalized as the maximum obstacle height cleared, four duration measures of successful task completion and compensatory movements used in the process of task completion. Eighteen participants with a BMI exceeding 30 kg/m2 completed a laboratory experiment that required stepping over seven lightweight obstacles. Obstacle heights were sequentially increased from 36 cm in 5 cm increments until participants were unsuccessful or unable to clear the obstacle up to 66 cm. Successful task completions decreased from 100% at an obstacle height of 36 cm to 66.1% at 66 cm. Higher obstacle heights were associated with significantly fewer task completions, longer leading and trailing leg stance and overall task duration, and more frequent use of compensatory movements for successful obstacle clearance. Cox PH regression was used to test the association between probability of obstacle clearance and normalized obstacle height adjusting for BMI, standing balance, and type of compensatory movement used, namely, hover and pivot motions involving the leg, and hands for bracing. The probability of successful task completion significantly decreased with increases in BMI (hazard ratio, HR = 1.14, 95% CI: 1.05-1.25), and increased with use of a leg pivot motion (HR = 0.30, 95% CI: 0.09-0.96) during task completion, after adjusting for standing balance and other types of compensatory movements. Overall, the results demonstrated that obstacle clearance performance is affected by an individual's BMI and the use of compensatory behaviors for regaining stability. The ability to recruit internal and external stabilization techniques could potentially serve as a clinical indicator of reduced fall risk and be the focus of fall prevention interventions. Implications for evaluating stability, fall risk, and identifying modifiable factors for fall prevention in the obese population are discussed.

Constraining the arms during a slip perturbation results in a higher fall frequency in young adults.

Slip and fall incidents are a major health concern. Although studies have reported the mechanical benefits of upper extremity responses during a slip to regain balance, it is not currently known if reactive arm motions aid in the recovery of a slip event. Sixty-four healthy young adults were randomized into 4 gait conditions: arms free, both arms constrained, contralateral arm to the slipping foot constrained and ipsilateral arm to the slipping foot constrained. While wearing a protective harness, participants traversed a 10-m walkway and were exposed to an unexpected slip. The group with their arms constrained exhibited a higher proportion of falls compared to the group with the arms free (62.5% vs 18.8%). In addition, individuals assigned to the contralateral arm constraint group exhibited a significantly higher proportion of falls compared to the group in which the ipsilateral arm was constrained (68.8% vs. 31.2%). Our findings suggest that arm motions aid in the recovery of balance during a slip perturbation. Motion of the arm contralateral to the slipping foot appears to be most important. Training upper extremity reactive responses training the arms may be a useful adjunct to fall prevention programs fall prevention.

Quantification of reactive arm responses to a slip perturbation.

The purpose of this study was two-fold: 1) characterize bilateral upper extremity responses during a slip event in both the sagittal and frontal planes, and 2) to examine the utility of using slip onset as the measurement reference for behavioral responses of the upper extremities using EMG latency. Sixteen healthy young adults were exposed to an unexpected slip during walking. Three-dimensional arm kinematics (excursions) and electromyographic onset latencies (bilateral deltoids) were quantified. Thirteen of the 16 participants recovered their balance following the slip perturbation. Of those who recovered, multi-planar arm responses were observed bilaterally. The arm contralateral to the slipping foot demonstrated significantly greater excursion in the frontal plane than the ipsilateral arm (p < 0.001), whereas excursions in the sagittal plane did not differ between arms (p = 0.75). Further, the frontal plane excursion of the contralateral arm was greater than sagittal plane excursion (p < 0.001). The electromyographic onset of deltoid activity was equivalent in both arms (57-76 ms), despite the differences in kinematics. Multi-plane arm motion occurs in response to a slip perturbation. Specifically, frontal plane motion of the arm contralateral to the slipping foot exhibited the greatest amount of excursion.