Unilateral arm binding generated greater transverse plane whole body angular momentum range during both steady-state walking and perturbation recovery, and reduced deltoid activation of the bound arm, highlighting the importance of clinicians screening patients for balance conditions prior to prescribing upper limb bracing or casting.
Key Findings
Results
Unilateral (non-dominant) arm binding generated greater transverse plane whole body angular momentum range (Lrange) during steady-state walking compared to the unbound condition.
Ten able-bodied individuals participated in the study.
Participants walked on an instrumented treadmill under two conditions: with and without non-dominant arm binding.
Whole body angular momentum range (Lrange) was averaged across the middle ten steady-state strides per trial.
Transverse plane Lrange was greater during arm-bound steady-state walking.
Results
Unilateral arm binding generated greater transverse plane whole body angular momentum range during perturbation recovery compared to the unbound condition.
Twelve perturbed walking trials per condition were completed by each participant.
EMG and kinematic data were collected during perturbation recovery.
Lrange was averaged across the first five post-perturbation strides per trial.
The increase in Lrange during perturbation recovery mirrors the pattern observed during steady-state walking.
Results
Deltoid activation of the bound arm was reduced during steady-state walking in the arm-bound condition compared to the same limb in the unbound condition.
EMG data were integrated (iEMG) across the middle ten steady-state strides per trial.
The reduction in deltoid activation was specific to the bound (non-dominant) arm.
This finding reflects the mechanical restriction imposed by the binding on normal arm swing musculature activity.
Results
Deltoid activation of the bound arm was reduced during perturbation recovery in the arm-bound condition compared to the same limb in the unbound condition.
iEMG was averaged across the first five post-perturbation strides per trial.
The reduced deltoid activation persisted into the reactive balance response following perturbation.
This suggests the bound arm contributes less muscular effort to reactive stabilization strategies.
Background
Bilateral arm binding has been associated with poorer stability in response to trip perturbations, and this study extends that work by examining unilateral arm binding.
Asymmetrical arm swing due to post-surgical bracing or upper limb loss has been associated with increased fall risk in the community.
Falls are described as the leading cause of non-fatal injuries in the United States, many of which occur during walking.
Prior research had not investigated the influence of unilateral arm binding on reactive balance strategies.
This study used healthy able-bodied individuals as the sample population.
What This Means
This research suggests that restricting movement of one arm — as might happen with a post-surgical brace or cast — disrupts the body's natural balance mechanisms during walking, both under normal conditions and when recovering from a stumble or trip. When participants walked with their non-dominant arm bound, the body's rotational momentum in the horizontal plane increased, meaning the torso was spinning more than usual and the body had a harder time maintaining controlled, symmetrical movement. At the same time, the shoulder muscle (deltoid) on the bound arm was less active, indicating that the arm was not contributing its normal share of muscle effort to stabilizing the body.
These effects were present not just during normal, undisturbed walking, but also during the critical moments after a perturbation — the kind of balance challenge that can lead to a fall in real life. This is important because people with one-sided arm restrictions, such as those recovering from arm or shoulder surgery, may be at greater risk of falling, particularly when they encounter unexpected obstacles or uneven terrain.
This research suggests that healthcare providers should assess a patient's underlying balance and gait abilities before prescribing upper limb bracing or casting that restricts arm movement on one side. Individuals who already have balance challenges may be at heightened risk if their arm swing is further disrupted by a brace or cast, and this factor may warrant additional fall prevention strategies or monitoring during recovery.
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Paulus P, Moore B, Hammond P, Stine R, Rosenblatt N, Major M. (2026). Dynamic balance adaptations in response to bound arm walking.. Journal of biomechanics. https://doi.org/10.1016/j.jbiomech.2026.113373