V. N. Pradeep Ambati

Assessment of oculomotor control and balance post-concussion: A preliminary study for a novel approach to concussion management

Abstract Primary objective: Balance disturbances occur in ∼30% of concussion injuries, with vestibular dysfunction reported as the main contributor. However, few have studied oculomotor control post-concussion to assess vestibular dysfunction. Research design: The current research measured the differences in oculomotor control between athletes post-concussion (PC) and athletes without concussion (NC) during an active balance control task. Methods: Nine PC and nine NC athletes wore a monocular eye tracking device, while balance tests were performed using the Nintendo WiiFit® soccer heading game. Average game scores, eye deviations from centre (Gaze Deviations) and gaze fixation (Percentage Time on Centre) were measured. Results: PC made significantly greater Gaze Deviations from centre compared to NC (p < 0.001), however Percentage Time on Centre and game scores were not significantly different between groups. Correlations between gaze and balance within groups revealed a significant positive correlation in NC, while a significant negative correlation in PC. Conclusions: Results from this exploratory examination of oculomotor behaviour post-concussion revealed significant differences in gaze stability between athletes with a concussion and those without, suggesting vestibular involvement post-concussion. Assessment of oculomotor control during balance activities may provide further insight into dysfunction of the vestibular system following a concussion injury.

Tactile stimuli affect long-range correlations of stride interval and stride length differently during walking

Sensory feedback below the sole of the foot using sub-threshold mechanical noise significantly reduced postural sway in patients with diabetes and stroke. However, the effects of tactile parameters on walking are still elusive. Specifically, the effects of such parameters on human gait variability need to be studied because of possible rehabilitation outcomes in terms of bringing improvement in temporal and spatial gait parameters. The purpose of this study was to investigate whether different frequency and amplitude combinations of vibro-tactile stimulation of feet would affect stride-to-stride variability in healthy young adults. Ten healthy subjects walked on a treadmill at self-selected pace while wearing customized insoles fitted with tactors that vibrated at selected frequencies and amplitudes. The results show that the frequency manipulations of tactile stimulation altered the long-range correlations (LRCs) in stride length while amplitude manipulations affected the LRCs in stride interval without having any effect on the amount of gait variability. Our findings suggest that independent neural mechanisms may be responsible for coordinating LRCs of gait parameters in the spatial and temporal domains.

Simulated Visual Field Loss Does Not Alter Turning Coordination in Healthy Young Adults

ABSTRACT Turning, while walking, is an important component of adaptive locomotion. Current hypotheses regarding the motor control of body segment coordination during turning suggest heavy influence of visual information. The authors aimed to examine whether visual field impairment (central loss or peripheral loss) affects body segment coordination during walking turns in healthy young adults. No significant differences in the onset time of segments or intersegment coordination were observed because of visual field occlusion. These results suggest that healthy young adults can use visual information obtained from central and peripheral visual fields interchangeably, pointing to flexibility of visuomotor control in healthy young adults. Further study in populations with chronic visual impairment and those with turning difficulties are warranted.

Assessment of Oculomotor Control and Balance in Concussed and Non-concussed Individuals

BACKGROUND: Poor lower limb stability during dynamic movement is thought to increase the risk of musculoskeletal injury. Biomechanically, stability is determined by a number of factors including the external load and contributions from passive and active tissues. One approach for studying lower limb stability is the single leg squat (SLS) test, which requires coordinated lower limb movement across a range of joint motions under external load. Although clinicians typically assess SLS quality from a single point of view (i.e. frontal plane), a 3D investigation of SLS kinematics would help to determine factors that differentiate clinician-defined “good” from “poor” quality performance. PURPOSE: To determine the kinematic parameters that characterise a good or a poor SLS performance in young adults. METHODS: 22 healthy young adults (13 male, 9 female; age: 23.8 ±3.1 years; height: 1.73 ±0.07 m; mass: 69.4 ±12.7 kg) free from musculoskeletal impairment were recruited. Video footage was collected in the frontal plane as participants performed three SLSs on each leg. SLS quality was assessed by a panel of physiotherapists using a ten-point ordinal scale. Performances were subsequently divided into tertiles corresponding to poor, intermediate and good SLS technique. 3D trajectories of 28 reflective markers attached to the pelvis, and lower limbs were simultaneously recorded at 200 Hz using a 10-camera, motion capture system (Vicon Motion Systems, Oxford, UK). Pelvis, hip and knee angles were calculated using a validated lower limb biomechanical model that incorporated functional identification of hip and knee joint centres. RESULTS: Mean rating of SLS quality as assessed by the panel of physiotherapists was 6.3±1.9 (range: 2.4 - 9.1). 3D analysis of SLS performance revealed that poor squatters had increased hip adduction (22.4 ±6.1 vs 14.7 ±4.7 deg, p<0.01), reduced knee flexion (73.1 ±8.7 vs 90.1 ±12.1 deg, p<0.01) and increased medal-lateral displacement of the knee joint centre (53.7 ±16.8 vs 38.4 ±14.3 mm, p=0.02) compared to good squatters. CONCLUSION: In healthy young adults a poor SLS is characterised by inadequate knee flexion and excessive frontal plane motion at the knee and hip. It is recommended that clinicians standardise knee flexion angle when using the SLS test as it might confound the perception of SLS quality.Purpose: To evaluate changes in performance and cardiac autonomic control (i.e. heart rate [HR] variability [HRV]) in elite soccer players during their pre-season training regime. Methods: Eight Spanish Premier League soccer players were examined at the first (week 1) and the last week (week 8) of the pre-season period (July-September). Nocturnal HR recordings on 4 days per week were averaged to evaluate the weekly HRV. Players also completed the Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1) for the assessment of specific fitness. Results: During the pre-season period, there was no significant change (4.5 ± 23.9%) in Yo-Yo IR1 performance (2,475 ± 421 vs. 2,600 ± 786 m, p=0.55), while there was a significant decrement (6.3 ± 4.3%) in maximal HR (HRmax) recorded during the test (191 ± 7 vs. 179 ± 8 bpm, p = 0.004). Over the 8-week pre-season, significant increases in the standard deviation of the long-term continuous HRV (SD2) (174 ± 56 vs. 212 ± 53 ms, p = 0.017), and in the standard deviation of all HR intervals (SDNN) (135 ± 50 vs. 163 ± 41 ms, p = 0.023) were noted. No significant correlations were identified between Yo-Yo IR1 and HRV measures at week 1. In contrast, Yo-Yo IR1 performance was significantly correlated with SDNN (r =0.89, p=0.007) and SD2 (0.92, p=0.003) at week 8. Greater values in HRV at week 1 were substantially associated with lower HRV changes at the end of pre-season (r values ranged from -0.79 to -0.98, p< 0.05). Furthermore, HRV changes were significantly correlated with decreases in HRmax during the pre-season (r values from 0.83 to 0.94, p<0.05). Conclusions: The current results confirm that despite minimal changes in specific fitness (i.e. Yo-Yo IR1), pre-season training significantly improved various HRV indices in elite soccer players with greater changes evident for those with lower initial HRV levels. Nocturnal HRV may provide an important monitoring tool for identification of cardiovascular function changes in top-class soccer players during pre-season regimes.

Head and Trunk Coordination in Turning between Young and Old Adults

BACKGROUND: Poor lower limb stability during dynamic movement is thought to increase the risk of musculoskeletal injury. Biomechanically, stability is determined by a number of factors including the external load and contributions from passive and active tissues. One approach for studying lower limb stability is the single leg squat (SLS) test, which requires coordinated lower limb movement across a range of joint motions under external load. Although clinicians typically assess SLS quality from a single point of view (i.e. frontal plane), a 3D investigation of SLS kinematics would help to determine factors that differentiate clinician-defined “good” from “poor” quality performance. PURPOSE: To determine the kinematic parameters that characterise a good or a poor SLS performance in young adults. METHODS: 22 healthy young adults (13 male, 9 female; age: 23.8 ±3.1 years; height: 1.73 ±0.07 m; mass: 69.4 ±12.7 kg) free from musculoskeletal impairment were recruited. Video footage was collected in the frontal plane as participants performed three SLSs on each leg. SLS quality was assessed by a panel of physiotherapists using a ten-point ordinal scale. Performances were subsequently divided into tertiles corresponding to poor, intermediate and good SLS technique. 3D trajectories of 28 reflective markers attached to the pelvis, and lower limbs were simultaneously recorded at 200 Hz using a 10-camera, motion capture system (Vicon Motion Systems, Oxford, UK). Pelvis, hip and knee angles were calculated using a validated lower limb biomechanical model that incorporated functional identification of hip and knee joint centres. RESULTS: Mean rating of SLS quality as assessed by the panel of physiotherapists was 6.3±1.9 (range: 2.4 - 9.1). 3D analysis of SLS performance revealed that poor squatters had increased hip adduction (22.4 ±6.1 vs 14.7 ±4.7 deg, p<0.01), reduced knee flexion (73.1 ±8.7 vs 90.1 ±12.1 deg, p<0.01) and increased medal-lateral displacement of the knee joint centre (53.7 ±16.8 vs 38.4 ±14.3 mm, p=0.02) compared to good squatters. CONCLUSION: In healthy young adults a poor SLS is characterised by inadequate knee flexion and excessive frontal plane motion at the knee and hip. It is recommended that clinicians standardise knee flexion angle when using the SLS test as it might confound the perception of SLS quality.Purpose: To evaluate changes in performance and cardiac autonomic control (i.e. heart rate [HR] variability [HRV]) in elite soccer players during their pre-season training regime. Methods: Eight Spanish Premier League soccer players were examined at the first (week 1) and the last week (week 8) of the pre-season period (July-September). Nocturnal HR recordings on 4 days per week were averaged to evaluate the weekly HRV. Players also completed the Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1) for the assessment of specific fitness. Results: During the pre-season period, there was no significant change (4.5 ± 23.9%) in Yo-Yo IR1 performance (2,475 ± 421 vs. 2,600 ± 786 m, p=0.55), while there was a significant decrement (6.3 ± 4.3%) in maximal HR (HRmax) recorded during the test (191 ± 7 vs. 179 ± 8 bpm, p = 0.004). Over the 8-week pre-season, significant increases in the standard deviation of the long-term continuous HRV (SD2) (174 ± 56 vs. 212 ± 53 ms, p = 0.017), and in the standard deviation of all HR intervals (SDNN) (135 ± 50 vs. 163 ± 41 ms, p = 0.023) were noted. No significant correlations were identified between Yo-Yo IR1 and HRV measures at week 1. In contrast, Yo-Yo IR1 performance was significantly correlated with SDNN (r =0.89, p=0.007) and SD2 (0.92, p=0.003) at week 8. Greater values in HRV at week 1 were substantially associated with lower HRV changes at the end of pre-season (r values ranged from -0.79 to -0.98, p< 0.05). Furthermore, HRV changes were significantly correlated with decreases in HRmax during the pre-season (r values from 0.83 to 0.94, p<0.05). Conclusions: The current results confirm that despite minimal changes in specific fitness (i.e. Yo-Yo IR1), pre-season training significantly improved various HRV indices in elite soccer players with greater changes evident for those with lower initial HRV levels. Nocturnal HRV may provide an important monitoring tool for identification of cardiovascular function changes in top-class soccer players during pre-season regimes.