Abstract
Introduction
Repetitive subconcussive head impacts alter gait and postural control, including reduced stepping-in-place variability hours after exposure. Laboratory-based repetitive soccer heading also produces significant postural control changes. What remains unknown is the extent to which arm swing during gait may also exhibit changes in dynamics after head impacts. If so, wearables such as smartwatches could be used to monitor neuromotor changes. The purpose of this study was to examine the acute changes in stepping-in-place gait variability and arm swing variability following repetitive soccer heading.
Methods
Ten college aged participants completed baseline stepping-in-place assessments under three conditions: eyes open, eyes closed, head shake. The participants then performed ten soccer headers from nine meters at approximately 25 mph, followed immediately by performing the same three stepping-in-place tasks. Variability was quantified as the coefficient of variation (CoV) of peak thigh and arm flexion, measured using a validated custom Android application called AccWalker. Hedges g was used due to the small sample size.
Results
For leg swing, moderate effects were observed across conditions: eyes open (pre: 0.911 +/- 2.166; post: 1.270 +/- 0.524; g = 0.561), eyes closed (pre: 1.576 +/- 1.343; post: 1.339 +/- 0.883; g = 0.670) and head shake (pre: 1.293 +/- 0.658; post: 1.417 +/- 1.078; g = 0.569). For arm swing, effect sizes were moderate: eyes open (pre: 1.092 +/- 0.229; post: 1.189 +/- 0.361; g = 0.605), eyes closed (pre: 1.116 +/- 0.314; post: 1.035 +/- 0.239; g = 0.641), and head shake (pre: 1.065 +/- 0.232; post: 1.028 +/- 0.249; g = 0.551).
Conclusion
Decreased variability following repetitive subconcussive impacts in the leg swing eyes closed condition aligns with prior research, whereas increases during the leg swing eyes open and head shake condition are not supported by previous findings. Differences between arm and leg swing variability suggest that arm swing using AccWalker requires further validation. These findings support prior evidence of acute postural control/gait changes following repetitive soccer heading and highlight the need for further evaluations of arm swing and eyes open CoV to determine if they are valid markers of postural control/gait variability after subconcussive head impacts.