Fabricio Saucedo

Effects of visual deprivation on stability among young and older adults during treadmill walking.

The purposes of this study were 1) to investigate the effect of visual deprivation on stability during treadmill walking in older and young adults, and 2) to examine if such an effect differs between age groups. Under the protection of a safety harness, 10 young (23.20±2.44years) and six older adults (67.83±2.48years) participants performed two 90-s walking trials (one with eyes open or EO and the other with eyes closed or EC) at their self-selected treadmill walking speeds determined during EO walking. The step length, step width, foot landing angle, the duration of stance phase, and cadence were calculated from the foot kinematics collected for each participant. The variability (i.e., the standard deviation) of step length, step width, foot landing angle, and the duration of stance phase was also calculated to quantify the stability during walking. Our results revealed that both young and older adults took a cautious gait pattern during EC walking, as evidenced by the shorter step length, smaller foot landing angle and shortened stance phase compared to EO walking. Under both visual conditions, older adults exhibited shorter step length and smaller foot landing angle than their young counterparts. No age-related differences were observed for the measurements of variability (i.e., the quantification of stability) while the variability measurement of all four variables was higher during EC walking than during EO walking for both age groups. Findings from this study could provide insights into the mechanisms of how visual information affects stability during gait.

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.

EFFECTS OF A SINGLE-SESSION STANCE-SLIP PERTURBATION TRAINING PROGRAM ON REDUCING RISK OF SLIP-RELATED FALLS

The purpose of this pilot study was to establish the efficacy and feasibility of a single-session treadmill-based stance-slip perturbation program on preventing slip-related falls while walking over the ground among young adults. Two groups (training vs. control) of healthy young participants were respectively exposed to a treadmill-based stance-slip perturbation training protocol and a placebo training protocol. Post training, both groups experienced an unexpected overground gait-slip. Our results indicated that 28.6% of individuals in the training group and 55.0% of controls fell when responding to the overground slip. In comparison with the control group, the training group exhibited better control over the compensatory step and dynamic stability at the instant immediately prior to recovery touchdown. The improved dynamic stability control in the training group likely resulted from the enhanced capability of harnessing the slip kinematics of the base of support. Dynamic stability did not display any significant group-associated difference at slipping foot touchdown and recovery foot liftoff. This implies that a stance-slip perturbation training protocol with eight slips may not provide enough and very task-specific incentive to the Central Nervous System to form the capability of sufficiently modifying regular gait pattern after an unexpected gait slip. However, given its ease of use, stance-perturbation could be a practical option to train individuals in clinical settings as a simple push or pull could exert a perturbation to a standing individual. The findings from this study provide information for developing future studies based on large-scale samples.

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.