Abstract
Background: Investigating soft tissue motion related to impact events is important for understanding how the body mitigates potentially injurious forces through shock attenuation. Objectives: The aims of this study were to: 1) quantify displacement and velocity of the forearm soft tissues following forward fall impacts; and 2) compare two massless skin marker designs (single layer, uniform (SLU) design; stacked, non-uniform (SNU) design) in terms of how well they could be tracked over varying skin pigmentations using automated motion capture software. Methods: Two participant groups (skin pigmentation: light – 9F, 8M; dark – 9F, 6M) underwent simulated forward fall hand impacts for each marker design using a torso-release apparatus. Marker positions associated with planar motion of forearm soft tissues during impact were automatically tracked (ProAnalyst®) in the proximal-distal and anterior-posterior axes from high speed recordings (5000 f/s). Mean peak displacements and velocities for eight forearm regions were then calculated (LabVIEW®). Results: Overall, soft tissue displacement and velocity increased from distal to proximal forearm regions. The greatest displacement (1.47 cm) and velocity (112.8 cm/s) occurred distally toward the wrist. Soft tissue impact responses between sexes did not differ, on average (p > 0.05). The SLU and SNU markers produced different kinematic values (p < 0.05); however, the magnitudes of, and consequently meaningfulness of these statistical differences for automatically tracking soft tissue motion, were negligible (displacement: ≤ 0.05 cm; velocity: ≤ 2.5 cm/s). Conclusions: Forearm soft tissue motion was successfully quantified for forward fall hand impacts; both marker designs were deemed functionally equivalent.
Highlights
Impacts to the hands and wrists resulting from forward falls, whether accidental in nature or due to recreational sporting activities, are problematic in both young and older adult populations because of the high incidence of upper extremity injuries associated with them (Nevitt & Cummings, 1993; Idzikowski, Janes & Abbott, 2000; Palvanen et al, 2000; Mirhadi, Ashwood & Karagkevrekis, 2015)
Preliminary screening of the forearm impact responses revealed that two male participants in the light pigmentation group had extreme outliers (z-score > 3.29) with respect to anterior soft tissue displacement
Despite clear differences in upper extremity soft and rigid tissue masses between females and males (Maughan, Abel, Watson & Weir, 1986; Mazess, Barden, Bisek & Hanson, 1990), the general lack of sex differences across the impact responses in this study suggests that forearm soft tissue motion associated with forward fall hand impacts may not be driven by tissue composition, but rather, the distribution of soft tissues along the forearm
Summary
Impacts to the hands and wrists resulting from forward falls, whether accidental in nature or due to recreational sporting activities, are problematic in both young and older adult populations because of the high incidence of upper extremity injuries (e.g., sprains, dislocations, fractures) associated with them (Nevitt & Cummings, 1993; Idzikowski, Janes & Abbott, 2000; Palvanen et al, 2000; Mirhadi, Ashwood & Karagkevrekis, 2015). Objectives: The aims of this study were to: 1) quantify displacement and velocity of the forearm soft tissues following forward fall impacts; and 2) compare two massless skin marker designs (single layer, uniform (SLU) design; stacked, non-uniform (SNU) design) in terms of how well they could be tracked over varying skin pigmentations using automated motion capture software. Marker positions associated with planar motion of forearm soft tissues during impact were automatically tracked (ProAnalyst®) in the proximal-distal and anterior-posterior axes from high speed recordings (5000 f/s). The SLU and SNU markers produced different kinematic values (p < 0.05); the magnitudes of, and meaningfulness of these statistical differences for automatically tracking soft tissue motion, were negligible (displacement: ≤ 0.05 cm; velocity: ≤ 2.5 cm/s). Conclusions: Forearm soft tissue motion was successfully quantified for forward fall hand impacts; both marker designs were deemed functionally equivalent
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