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Objective: The current investigation examined how a bout of soccer heading may impact brain function. Design: Semi-randomized crossover cohort. Setting: Controlled soccer heading. Participants: Seven male soccer players (24.1 ± 1.5 years). Intervention: 40 successful soccer headers were performed in 20 min (25 m, launch velocity ~80 km/h). X2 xPatch recorded linear and rotational head accelerations during each impact. A contact control “sham” condition – ball made body contact, but not by the head; and a no activity time “control” condition were also completed. Main Outcome Measures: Posterior and middle cerebral artery (PCA and MCA, respectively), cerebral blood velocity (CBV) was recorded during a visual task (neurovascular coupling: NVC) alongside SCAT3 symptoms scores pre/post a controlled bout of soccer heading. Results: Cumulative linear and rotational accelerations were 1,574 ± 97.9 g and 313,761 ± 23,966 rads/s2, respectively, during heading and changes in SCAT3 symptom number (pre: 2.6 ± 3.0; post: 6.7 ± 6.2, p = 0.13) and severity (pre: 3.7 ± 3.6, post: 9.4 ± 7.6, p = 0.11) were unchanged. In the PCA, no NVC differences were observed, including: relative CBV increase (28.0 ± 7.6%, p = 0.71) and total activation (188.7 ± 68.1 cm, p = 0.93). However, MCA-derived NVC metrics were blunted following heading, demonstrating decreased relative CBV increase (7.8 ± 3.1%, p = 0.03) and decreased total activation (26.7 ± 45.3 cm, p = 0.04). Conclusion: Although an acute bout of soccer heading did not result in an increase of concussion-like symptoms, there were alterations in NVC responses within the MCA during a visual task. This suggests an acute bout of repetitive soccer heading can alter CBV regulation within the region of the brain associated with the header impacts.

Ocular near point of convergence (NPC) has been shown to be sensitive to the effects of concussion and subconcussive impacts. To determine if NPC is also sensitive to a previous history of concussion, male contact-sport athletes either with (n=26) or without (n=16) a history of at least one previous concussion had their NPC assessed. The results showed that participants with a history of concussion displayed NPC values (9.4±1.6 cm) indistinguishable from those with no history of concussion (8.4±2.1 cm, t-test, p=0.09). This was the case regardless of whether 1, 2, or 3 or more concussions had occurred and despite the fact participants with concussion (mean time since last concussion: 1136 days) suffered from an increased number and severity of symptoms as assessed with the SCAT 3 (3.6±2.2 vs. 2.13±1.89 symptoms, 6.1±4.1 vs. 3.19±2.99 severity, t-test, p

In the present study we investigated how attention contributes to the interaction between reach planning and execution, and postural control. Reaching movements were generated while standing and were performed either in isolation or in conjunction with a secondary reaction time (RT) task. In addition, to better understand how online movement control is affected by this interaction, the reaching movements could be unexpectedly perturbed medial-laterally. Postural kinetic, arm kinematic and RT, and secondary RT measures were used to characterize the responses. Results indicate task performance worsened when both the reaching and secondary tasks were completed simultaneously. Our results imply the generation of reaching movements while standing requires attentional resources to properly coordinate the interaction between the reaching task and postural control.

Although balance control has been studied extensively following acute concussion, little is known regarding repetitive sub-concussive head impacts or chronic exposure to multiple concussive events. Quiet stance postural control was characterized in contact sport athletes at pre-season (n = 135) and post-season (n = 48) to evaluate the effects of subconcussive trauma to the head. To determine the impact of acute concussion on postural control, athletes diagnosed with a concussion during the season (n = 12) were tested at 72-h, 2-weeks, and 1-month post-injury. Because only 4 of the concussed athletes completed baseline testing, control athletes (n = 12) matched for sport, age, body mass index (BMI), and previous concussion history served as a comparison group. Finally, the effects of previous concussion history on quiet stance postural control were determined by comparing pre-season data in contact sport athletes with either zero (Hx0, n = 50) or three or more (Hx3+, n = 25) previous concussions. A force plate was used to compare changes in centre-of-pressure root-mean-square displacement (RMSdisp) and mean-velocity (COPvel) in the anterior/posterior (AP) and medial/lateral (ML) directions. One-minute trials were performed with feet hip-width apart, hands-on-hips, and A) eyes-open and B) eyes-closed. Biomechanical head-impact exposure (impacts over 10 g) was indexed over the season using mastoid-fixed impact sensors. In acutely injured athletes, repeated-measures ANOVA revealed a significant effect of time for RMSdisp AP with increased displacement at 2 weeks compared to 72 h (p = 0.008, 95% CI: −0.180, −0.310 cm). No other COP variables were affected by acute concussion. Moreover, there was no effect of concussion history or repeated sub-concussive impacts on any quiet stance metric. Additionally, head-impact exposure metrics were not correlated with COP metrics. Taken together, the data suggests alterations in COP sway during quiet stance persist in the acute 2-week period after injury. These findings were not present with either a history of multiple concussions or exposure to sub-concussive head impacts indicating acute concussion does not have appear to have long term effects for these measures.

Objective To determine the influence of a history of 3+ previous concussions on quiet stance. Design Retrospective cohort. Setting Laboratory. Participants Eighty-seven male (age range 17–22) contact-sport athletes (football and hockey) entered the study. Participants were recruited from the same sport teams and tested during the pre-season. Exclusion criteria: concussion in the prior 6 months, or history of 1 or 2 concussions. Forty-four met the inclusion criteria: thirty-one had no previous concussions, and thirteen had a history of 3+ concussions. Interventions Participants held quiet upright stance on a force plate (NDI True Impulse) with feet hip-width apart and hands on hips with eyes-open (1 min), and closed (1 min). Independent variables included condition (2) and concussion history (2). Outcome measures Root-mean-square displacement (RMSd), and mean velocity of centre-of-pressure (COP) in the anterior/posterior (AP) and medial/lateral (ML) directions. Main results Mixed ANOVA indicated a significant condition effect in ML-RMSd (p=0.015, 95% CI: 0.032–0.277) between eyes-open and eyes-closed conditions. ML mean velocity also displayed a significant condition effect (p=0.025, 95% CI: 0.025–0.358). In contrast to the effect of visual input, there was no main effect of concussion history on these metrics. Conclusions A history of 3+ concussions does not appear to result in long-term deficits controlling in quiet stance. Those ML variables were sensitive to condition and indicate that frontal plane COP movements may be more sensitive than those in the sagittal plane. These findings are important as a history of concussion does not appear to alter quiet stance balance control mechanisms. Competing interests None.

Objective To examine how sub-concussive head trauma throughout a contact-sport season affects quiet stance centre of pressure (COP) sway Design Prospective cohort Setting Laboratory Participants: Twenty-four elite male football players (age range 18–22) were recruited for the study Intervention Quiet stance data was collected at the start and at the end of the competitive season. One-minute trials were performed with eyes-open and eyes-closed on a force plate (NDI True Impulse) with feet hip-width apart and hands-on-hips. Biomechanical head-impact exposure was indexed using the xPatch (X2 Biosystems) Outcome measures COP measures: Anterior/posterior (AP) and medial/lateral (ML) root-mean-square displacement (RMSd) and mean velocity. Biomechanical head-impact data: For hits above 20g, peak linear acceleration (PLA), and peak rotational acceleration (PRAwere estimated across the competitive season. Independent variables included time (2) and condition (2) Results RM-ANOVA reveal an effect of condition (eyes-open vs eyes-closed) in AP-RMSd (p=0.035, 95% CI: 0.006, 0.159), ML-RMSd (p Conclusions In contrast to the prolonged COP alterations observed following acute concussions, there were no discernable effects of sub-concussive trauma on COP sway during quiet stance in the same population. This is an important finding as it reveals that participation in contract-sport does not impair quiet stance balance Competing interests None.

Objective To examine how acute sport-related concussion influences centre of pressure (COP) sway during quiet stance Design Prospective cohort Setting Laboratory Participants Eighty-seven male contact-sport (football and hockey) athletes entered the study. Seven subjects (age range 17–22) were concussed and completed follow-up testing 72-hours, two-weeks, and one-month following the injury. Intervention One-minute eyes-open and eyes-closed quiet stance trials were performed on a force plate (NDI True Impluse) with feet hip-width apart. Force plate data and SCAT3 were collected at each time point. Outcome measures Root-mean-square COP displacement (RMSd) and mean COP velocity were quantified in the anterior/posterior (AP) and medial/lateral (ML) directions. Independent variables included condition (2) and time (4) Main results RM-ANOVA indicated a main effect of time for all outcomes: AP-RMSd (p=0.006), AP mean velocity (p=0.012), ML-RMSd (p=0.001), ML mean velocity (p=0.001). Pairwise comparisons indicated reductions at 2-weeks in AP-RMSd (0.05, 95% CI: −0.672, 0.000), and AP mean velocity (p=0.039, 95% CI: −1.275, −0.036). ML-RMSd was reduced 1 month post-concussion (p=0.021, 95% CI: −0.365, −0.034). Change scores from baseline to 72-hours were correclated between: AP-RMSd and Balance Error Scoring System (r=0.878, p=0.009), AP mean velocity and Standardised Assessment of Concussion (SAC) (r=−0.822, p=0.023), and ML mean velocity and SAC (r=−0.836, p=0.019). Conclusions Measures of COP sway during quiet stance revealed alterations in displacement and velocity that persisted up to one-month following a sports-related concussion. These COP alterations exceeded the duration of clinical recovery (median return-to-play: 14 days) indicating that clinical recovery does not equal physiological recovery. Competing interests None.

Objective Examine how the frequency-dependent relationship between blood pressure (BP) and cerebral blood velocity (CBV) is affected by acute sport-related concussion. Design Prospective Cohort. Setting Laboratory. Participants: 136 male contact-sport athletes (19.1±1.4 years) recruited, subset of 14 sustained concussions (19±1.4 years). Intervention Participants completed baseline (T0) and post-injury testing at 72-hours (T1), 2-weeks (T2), and 1-month (T3). BP was monitored via finger photoplethysmography, and transcranial Doppler ultrasound indexed CBV in the middle cerebral artery. Squat-stand manoeuvers were performed at 0.05 and 0.10Hz to enhance BP variation. RM-ANOVA independent variables included time (4) and frequency (2). Outcome measures Transfer function analysis point estimates quantified coherence (correlation), phase (synchronisation) and gain (amplitude buffer) metrics between BP and CBV waveforms. Results Significant frequency-time interactions for phase (p=0.007) and gain (p=0.049). Simple effects analysis revealed time effects for phase at 0.10 Hz, indicating reductions at T1 (95% CI: 0.033 – 0.24 rads, p=0.008) and T2 (95% CI: 0.014–0.196 rads, p=0.02) compared to T0. On average, return-to-play occurred at T2 (median 14 days). Phase reductions at T1 were correlated with Standardised Assessment of Concussion performance (r=0.659, p=0.02). Conclusions These results reveal transient post-concussion impairments in the capacity of the cerebrovasculature to buffer BP oscillations, which exceeded clinical recovery duration. Phase reductions at 0.10Hz suggest the presence of a cerebrovascular autonomic dysregulation, which could leave the brain less protected to BP surges. This key finding may help explain why the brain is more vulnerable to additional trauma during the post-injury recovery period. Competing interests None.