The Effects of an Inclusive Badminton Program on Static Postural Control for Individuals with Intellectual and Developmental Disabilities.

The purpose of the study was to examine static postural control/balance in young adults with intellectual and developmental disabilities (IDD) and typically developing (TD) young adults before, during, and after an inclusive badminton intervention. Eight participants (four IDD-BADM and four TD-BADM) participated in a 12-week inclusive badminton intervention, with the other eight participants as matched controls (four IDD-CONTR and four TD-CONTR) (74.19 kg ± 9.8 kg, 171.96 cm ± 5.4 cm; 21.7 ± 1.8 years of age; nine females and seven males; eight with IDD and eight TD). The study followed a repeated measures design (pre, mid, post) before the intervention, at 6 weeks, and after 12 weeks. Static postural sway conditions included: bilateral stance eyes open (20 s), eyes closed (10 s), foam eyes open (20 s), foam eyes closed (10 s), and unilateral stance eyes open (10 s) and foam eyes open (10 s). Sway measurements included: average anterior/posterior (A/P) displacement (in), average medial/lateral (M/L) displacement (in), average 95% ellipsoid area (in2), and average velocity (ft/s). Significant time × group interactions were reported for average velocity (EO) (p = 0.030), average length (EO) (p = 0.030), 95% ellipsoid area (EO) (p = 0.049), and average A/P displacement (1LEO) (p = 0.036) for IDD-BADM. Significant time main effects were reported for average A/P displacement (FEO) (p = 0.040) for IDD groups. Significant time main effects were reported for average M/L displacement (EO) (p = 0.001), (EC) (p = 0.004), (FEO) (p = 0.005), (FEC) (p = 0.004), and average A/P displacement (EO) (p = 0.006) and (FEO) (p = 0.005) for TD groups. An inclusive badminton program indicated evidence of improved static postural control for those with IDD. However, no significant differences were reported for TD peers.

Closed-Loop Reflex Responses of the Lateral Ankle Musculature From Various Thresholds During a Lateral Ankle Sprain Perturbation.

CONTEXT: Latency is a reliable temporal metric used to evaluate sensorimotor integration of the fibularis longus (FL) and fibularis brevis (FB) during lateral ankle sprain perturbations. Currently, no clinical recommendations exist to select appropriate thresholds to evaluate the closed-loop reflex response of the lateral ankle musculature. The purpose of this study was to assess threshold value on latency of the FL and FB during an unanticipated inversion perturbation that simulates the mechanism of a lateral ankle sprain. DESIGN: Descriptive laboratory study. METHODS: Twenty healthy adults with no history of lateral ankle sprain injury completed an unanticipated single-leg drop landing onto a 25° laterally inclined force platform from a height of 30 cm. Surface electromyography recorded muscle activity data from the FL and FB during the inversion perturbation. Latency was identified at points where muscle activity exceeded 2, 5, and 10 SD above the average muscle activity 200 milliseconds prior to foot contact, and compared across threshold value using a 1-way analysis of variance (P < .05). RESULTS: The 2 SD threshold was significantly shorter than both 5 SD and 10 SD thresholds for the FL (P < .01) and FB (P < .01). Likewise, the 5 SD threshold was significantly shorter than the 10 SD thresholds for FL (P = .004) and FB (P = .003). CONCLUSIONS: More sensitive thresholds results in a shorter closed-loop reflexive response compared to the more rigorous thresholds. We recommend that selection of the appropriate threshold to identify latency of the lateral ankle musculature should be based on the device used to simulate a lateral ankle sprain and the ankle inversion velocity produced during the ankle inversion perturbation.

Physiological and Subjective Measures of Anxiety with Repeated Exposure to Virtual Construction Sites at Different Heights.

Background: Occupational workers at altitudes are more prone to falls, leading to catastrophic outcomes. Acrophobia, height-related anxiety, and affected executive functions lead to postural instabilities, causing falls. This study investigated the effects of repeated virtual height exposure and training on cognitive processing and height-related anxiety. Methods: Twenty-eight healthy volunteers (age 20.48 ± 1.26 years; mass 69.52 ± 13.78 kg) were recruited and tested in seven virtual environments (VE) [ground (G), 2-story altitude (A1), 2-story edge (E1), 4-story altitude (A2), 4-story edge (E2), 6-story altitude (A3), and 6-story edge (E3)] over three days. At each VE, participants identified occupational hazards present in the VE and completed an Attitude Towards Heights Questionnaire (ATHQ) and a modified State-Trait Anxiety Inventory Questionnaire (mSTAIQ). The number of hazards identified and the ATHQ and mSTAIQ scores were analyzed using a 7 (VE; G, A1, A2, A3, E1, E2, E3) x 3 (DAY; DAY 1, DAY 2, DAY 3) factorial repeated measures analysis of variance. Results: The participants identified the lowest number of hazards at A3 and E3 VEs and on DAY 1 compared to other VEs and DAYs. ATHQ scores were lowest at G, A1, and E1 VEs. Conclusion: Cognitive processing is negatively affected by virtual altitudes, while it improves with short-term training. The features of virtual reality, such as higher involvement, engagement, and reliability, make it a better training tool to be considered in ergonomic settings. The findings of this study will provide insights into cognitive dual-tasking at altitude and its challenges, which will aid in minimizing occupational falls.

Quick on Your Feet: Modifying the Star Excursion Balance Test with a Cognitive Motor Response Time Task.

The Star Excursion Balance Test (SEBT) is a common assessment used across clinical and research settings to test dynamic standing balance. The primary measure of this test is maximal reaching distance performed by the non-stance limb. Response time (RT) is a critical cognitive component of dynamic balance control and the faster the RT, the better the postural control and recovery from a postural perturbation. However, the measure of RT has not been done in conjunction with SEBT, especially with musculoskeletal fatigue. The purpose of this study is to examine RT during a SEBT, creating a modified SEBT (mSEBT), with a secondary goal to examine the effects of muscular fatigue on RT during SEBT. Sixteen healthy young male and female adults [age: 20 ± 1 years; height: 169.48 ± 8.2 cm; weight: 67.93 ± 12.7 kg] performed the mSEBT in five directions for three trials, after which the same was repeated with a response time task using Blazepod™ with a random stimulus. Participants then performed a low-intensity musculoskeletal fatigue task and completed the above measures again. A 2 × 2 × 3 repeated measures ANOVA was performed to test for differences in mean response time across trials, fatigue states, and leg reach as within-subjects factors. All statistical analyses were conducted in JASP at an alpha level of 0.05. RT was significantly faster over the course of testing regardless of reach leg or fatigue state (p = 0.023). Trial 3 demonstrated significantly lower RT compared to Trial 1 (p = 0.021). No significant differences were found between fatigue states or leg reach. These results indicate that response times during the mSEBT with RT is a learned skill that can improve over time. Future research should include an extended familiarization period to remove learning effects and a greater fatigue state to test for differences in RT during the mSEBT.

Impact of Sub-Clinical and Clinical Compression Socks on Postural Stability Tasks among Individuals with Ankle Instability.

Compression socks are used by a very diverse group of individuals and may potentially have a greater impact on physically diminished or impaired individuals as opposed to healthy individuals. The purpose of this study was to compare the effects of sub-clinical (SC) and clinical (CL) compression socks among healthy (CON), copers (COP), and individuals with chronic ankle instability (CAI). Postural stability was evaluated in 20 participants (11 males and 9 females) using Balance Tracking System Balance platform (BTrackS™) during the modified clinical test of sensory integration in balance (mCTSIB) and limits of stability (LOS) tests. Postural sway parameters were analyzed using a mixed model repeated measures analysis of variance 3 (group: CON, COP, and CAI) by 3 (compression condition: BF, SC, and CL) × 4 (balance condition: EO, EC, EOF, and ECF) for mCTSIB and a 3 (group: CON, COP, and CAI) by 3 (compression condition: BF, SC, CL) × 4 (balance condition: FL, BL, BR, FR) for LOS. Results revealed significantly greater postural stability with both SC and CL compression socks when compared to barefoot conditions. However, no significant differences were observed among groups for compression socks grades. Both SC and CL compression socks may be effective in increasing postural stability.

Lower extremity joint kinematics of a simulated lateral ankle sprain after drop landings in participants with chronic ankle instability.

This study examined lower extremity joint kinematics in individuals with chronic ankle instability (CAI) and controls during unanticipated and anticipated single-leg drop landings onto a laterally inclined platform. Physically active adults with CAI 15 (n = 15) and controls (n = 15) performed an unanticipated and anticipated 30 cm single-leg drop landing onto a 20° laterally inclined platform. Three-dimensional ankle, knee and hip-joint kinematics were recorded 200 ms pre- to 200 post-landing and analysed with a 2 (group) × 2 (landing condition) SPM ANOVA (p < 0.05). Results revealed individuals with CAI displayed significantly greater ankle internal rotation post-landing across both landing conditions. Anticipated landings elicited significantly greater pre-landing ankle inversion and external rotation, knee abduction and hip adduction. Additionally, significantly less ankle inversion, knee and hip flexion, and knee adduction and hip abduction were present during post-landing of the anticipated landing. Greater ankle internal rotation during landing may contribute to the ankle 'giving way' in individuals with CAI. However, preparatory and reactive proximal-joint kinematics were similar in both groups during landing. This highlights the possible role of the knee and hip joints in assisting with ankle-joint stability during anticipated inversion perturbations.

Dual Tasking during Trip Recovery and Obstacle Clearance among Young, Healthy Adults in Human Factors Research.

Trip-induced falls are extremely common in ergonomic settings. Such situations can lead to fatal or non-fatal injuries, affecting the workers' quality of life and earning capacity. Dual tasking (DT) is a leading cause of trips and ineffective obstacle clearance among workers. DT increases their attentional demand, challenging both postural control and concurrent secondary tasks. As the human brain has limited attentional processing capacity, even young, healthy adults need to prioritize duties during DT. This article aimed to analyze these secondary task types and their applications in recent trip-related studies conducted on young, healthy adults. An extensive review of the recent trip-related literature was performed to provide a condensed summary of the dual tasks used. In previous trip-related literature, distinct types of secondary tasks were used. The choice of the concurrent task must be made vigilantly depending on the occupation, environmental context, available resources, and feasibility. DT can be used as a tool to train workers on selective attention, which is a lifesaving skill in ergonomic settings, especially in the occupations of roofers, construction workers, or truck drivers. Such training can result in successful obstacle clearance and trip recovery skills, which eventually minimizes the number of falls at the workplace.

Sensory Organization Test Conditions Influence Postural Strategy Rather than Footwear or Workload.

BACKGROUND: Postural strategies such as ankle, hip, or combined ankle-hip strategies are used to maintain optimal postural stability, which can be influenced by the footwear type and physiological workload. PURPOSE: This paper reports previously unreported postural strategy scores during the six conditions of the sensory organization test (SOT). METHODS: Fourteen healthy males (age: 23.6 ± 1.2 years; height: 181 ± 5.3 cm; mass: 89.2 ± 14.6 kg) were tested for postural strategy adopted during SOT in three types of occupational footwear (steel-toed work boot, tactical work boot, low-top work shoe) every 30 min during a 4-h simulated occupational workload. Postural strategy scores were analyzed using repeated measures analysis of variance at 0.05 alpha level. RESULTS: Significant differences among postural strategy scores were only evident between SOT conditions, and but not between footwear type or the workload. CONCLUSIONS: Findings indicate that occupational footwear and occupational workload did not cause a significant change in reliance on postural strategies. The significant changes in postural strategy scores were due to the availability of accurate and/or conflicting sensory feedback during SOT conditions. In SOT conditions where all three types of sensory feedback was available, the ankle strategy was predominantly adopted, while more reliance on hip strategy occurred in conditions with absent or conflicting sensory feedback.

Impact of Prolonged Exposure to a Slippery Surface on Postural Stability.

Falls are extremely common in occupational settings. Intrinsic factors such as overexertion and extrinsic factors such as the supporting surface are causative factors of falls. The impact of prolonged exposure to a slippery surface on postural stability has not been previously studied. The purpose of the study was to analyze the effect of extended exposure to a dry and a slippery surface on postural stability. Eighteen males (age: 21.17 ± 3.38 years; height: 1.77 ± 0.08 m; mass: 89.81 ± 14.23 kg) were recruited and subjected to one-hour walking on a dry surface and a slippery surface on two different days. Participants' balance was assessed using a force platform in stable and unstable conditions at 0, 30, and 60 min. Postural sway variables were analyzed using a 2 (surface) × 3 (time) repeated-measures ANOVA. Significant time main effects were observed in the stable condition with greater balance decrements at 30 and 60 min. Greater balance decrements were observed on the slippery surface compared to the dry surface in the unstable condition. The balance decrements can be attributed to overexertion due to the physiological workload of prolonged walking and to the potential gait modifications due to walking on the slippery surface.

Lower Extremity Muscle Activation in Alternative Footwear during Stance Phase of Slip Events.

Muscle activity from the slipping leg have been previously used to analyze slip induced falls. However, the impact of casual alternative footwear on slipping leg muscle activity when exposed to slippery environments is still unknown. The purpose of the study was to analyze the impact of alternative footwear (crocs (CC) and flip-flops (FF)) compared to slip-resistant footwear (LT) on lower extremity muscle activity when exposed to dry gait (NG), unexpected (US), alert (AS), and expected slips (ES). Eighteen healthy males (age: 22.3 ± 2.2 years; height: 177.7 ± 6.9 cm; weight: 79.3 ± 7.6 kg) completed the study in a repeated measures design in three footwear sessions separated by 48 h. Electromyography (EMG) muscle activity from four muscles of the lead/slipping leg was measured during the stance phase of the gait-slip trials. A 3 (footwear) × 4 (gait-slip trials) repeated measures analysis of variance was used to analyze EMG dependent variables mean, peak, and percent of maximal voluntary contraction. Greater lower extremity muscle activation during the stance phase was seen in US and AS conditions compared to NG and ES. In addition, footwear differences were seen for the alternative footwear (CC and FF) during US and AS, while the low top slip resistant shoe had no differences across all gait trials, suggesting it as the most efficient footwear of choice, especially when maneuvering slippery flooring conditions, either with or without the knowledge of an impending slip.

Impact of Fat Grip Attachments on Muscular Strength and Neuromuscular Activation During Resistance Exercise.

ABSTRACT: Krings, BM, Shepherd, BD, Swain, JC, Turner, AJ, Chander, H, Waldman, HS, McAllister, MJ, Knight, AC, and Smith, JW. Impact of fat grip attachments on muscular strength and neuromuscular activation during resistance exercise. J Strength Cond Res 35(2S): S152-S157, 2021-The purpose of this study was to examine the acute effects of Fat Gripz (FG) on muscular activation and strength. Resistance trained men (n = 15; age = 22.4 ± 2.3 years; mass = 83.2 ± 11.1 kg) performed 2 experimental trials in a randomized order. Subjects completed 1 repetition maximum (1RM) testing with an Olympic barbell (OB) and with FG attached to an OB during the exercises of deadlift, bent-over row, upright row, concentration curl, and completed maximum repetitions of pull-ups until failure. Surface electromyography (EMG) was used to measure muscle activity from 8 upper extremity muscles (trapezius, medial deltoid, biceps brachii, triceps brachii, flexor carpi radialis, flexor carpi ulnaris, extensor carpi radialis, and extensor carpi ulnaris), while performing maximal voluntary isometric contractions during 1RM trials and while performing maximum number of pull-ups. When using the FG, 1RM strength was significantly decreased for each exercise, and the maximal number of pull-ups completed was significantly lower. Electromyography muscle activity was significantly increased in the forearm and shoulder muscles, but significantly decreased in the upper arm muscles with the use of FG during deadlift, bent-over row, and pull-ups. However, there were no differences for EMG activity for upright row and concentration curl. Differences in maximal strength, pull-up performance, and EMG activity with FG use may be due to the different muscle length positions. Although FG training may increase neuromuscular activation, decrements in muscular strength may result in prescribing low training loads that may not be ideal for building muscular strength.

Impact of Virtual Reality-Generated Construction Environments at Different Heights on Postural Stability and Fall Risk.

BACKGROUND: Falls due to postural instability are common in construction environments especially from a height. The purpose of the study was to investigate the impact of virtual reality (VR)-generated environments at different virtual heights on postural stability. METHODS: Nineteen adults were analyzed for postural stability, tested in real (No VR) environment and in three VR environments, randomly assigned, at virtual heights of 0 ft. (VR0), 40 ft. (VR40), and 120 ft. (VR120). Postural stability was quantified using center of pressure postural sway variables and analyzed using a repeated measures analysis of variance (ANOVA). Participants also completed a simulation sickness questionnaire (SSQ) before and after VR exposure and a presence questionnaire (PQ) after VR exposure. FINDINGS: Significant postural instability (p < .05) was identified between VR and No VR, in which increased postural instability was evident in all VR conditions compared with No VR. Scores from SSQ were within a pre-post score difference of five and the PQ score was (104.21 ± 14.03). CONCLUSION/APPLICATION TO PRACTICE: Findings suggest that VR environments, regardless of virtual height, induced increased postural instability, which can be attributed to visual sensory conflicts to the postural control system created by VR exposure. Participants' subjective responses on SSQ and PQ confirmed the feasibility of using VR to represent realistic immersions in virtual heights. However, objectively, VR could potentially lead to postural instability, stressing caution. VR can be a potential tool for providing virtual high-altitude environment exposure for fall prevention training, however, more research is needed on postural adaptation with acute and chronic exposure to VR.

Ankle kinematics, center of pressure progression, and lower extremity muscle activity during a side-cutting task in participants with and without chronic ankle instability.

This study assessed ankle kinematics, surface electromyography, and center-of-pressure (COP) progression relative to the medial border of the foot during a side-cutting task in individuals with and without chronic ankle instability (CAI). Thirty participants (CAI = 15; Controls = 15) performed a side-cutting task on a force platform while 3-dimentional ankle kinematics, COP position, and surface electromyography from the tibialis anterior, medial gastrocnemius, fibularis longus, fibularis brevis, vastus medialis, and semitendinosus were recorded on the testing leg. Ankle kinematics, root-mean-square muscle activity and COP position relative to the medial boarder of the foot were compared between CAI and healthy controls (p < 0.05). Significantly greater ankle internal rotation from 35-54% of the stance phase (p = 0.032) was found for the CAI group compared to controls. Furthermore, significantly greater tibialis anterior muscle activity from 86-94% of the stance phase (p = 0.022) and a more medial COP position from 81-100% (p < 0.05) and of the stance phase was also observed in the CAI group. Less lateral COP progression and increased tibialis anterior activation in the CAI group could reflect a protective movement strategy during anticipated side-cutting to avoid recurrent injury. However, greater ankle internal rotation during mid-stance highlights a potential 'giving way' mechanism in individuals with CAI.

Lower Limb Joint Kinetics During a Side-Cutting Task in Participants With or Without Chronic Ankle Instability.

CONTEXT: Individuals with chronic ankle instability (CAI) demonstrate altered lower limb movement dynamics during jump landings, which can contribute to recurrent injury. However, the literature examining lower limb movement dynamics during a side-cutting task in individuals with CAI is limited. OBJECTIVE: To assess lower limb joint kinetics and sagittal-plane joint stiffness during the stance phase of a side-cutting task in individuals with or without CAI. DESIGN: Cohort study. SETTING: Motion-capture laboratory. PATIENTS OR OTHER PARTICIPANTS: Fifteen physically active, young adults with CAI (7 men, 8 women; age = 21.3 ± 1.6 years, height = 171.0 ± 11.2 cm, mass = 73.4 ± 15.2 kg) and 15 healthy matched controls (7 men, 8 women; age = 21.5 ± 1.5 years, height = 169.9 ± 10.6 cm, mass = 75.5 ± 13.0 kg). INTERVENTION(S): Lower limb 3-dimensional kinematic and ground reaction force data were recorded while participants completed 3 successful trials of a side-cutting task. Net internal joint moments, in addition to sagittal-plane ankle-, knee-, and hip-joint stiffness, were computed from 3-dimensional kinematic and ground reaction force data during the stance phase of the side-cutting task and analyzed. MAIN OUTCOME MEASURE(S): Data from each participant's stance phase were normalized to 100% from initial foot contact (0%) to toe-off (100%) to compute means, standard deviations, and Cohen d effect sizes for all dependent variables. RESULTS: The CAI group exhibited a reduced ankle-eversion moment (39%-81% of stance phase) and knee-abduction moment (52%-75% of stance phase) and a greater ankle plantar-flexion moment (3%-16% of stance phase) than the control group (P range = .009-.049). Sagittal-plane hip-joint stiffness was greater in the CAI than in the control group (t28 = 1.978, P = .03). CONCLUSIONS: Our findings suggest that altered ankle-joint kinetics and increased hip-joint stiffness were associated when individuals with CAI performed a side-cutting task. These lower limb kinetic changes may contribute to an increased risk of recurrent lateral ankle sprains in people with CAI. Clinicians and practitioners can use these findings to develop rehabilitation programs for improving maladaptive movement mechanics in individuals with CAI.

Effects of Weighted Vest Loading During Daily Living Activities on Countermovement Jump and Sprint Performance.

PURPOSE: Wearing a weighted vest (WV) during daily living and training can enhance jump and sprint performance; however, studies examining the efficacy of this method in female populations is limited. This study examined the effect of wearing a WV during daily living and training on countermovement jump (CMJ), change-of-direction, and sprint performance. METHODS: Trained females were separated into intervention (n = 9) and control (n = 10) groups. The intervention group wore WVs of ∼8% body mass 4 days per week for 8 hours per day (32 h/wk total), and 3 training sessions per week for the first 3 weeks. Subsequently, 3 weeks of regular training without WV stimulus was completed. The control group received no intervention and continued normal training for 6 weeks. Average and best performance was assessed on the single CMJ, four continuous CMJ, t-test change-of-direction drill, and a 25-m sprint at baseline, week 3, and week 6. RESULTS: No significant interactions or group effects were found. However, significant time main effects revealed increases in average rate of force development during the CMJ from baseline to week 3 (P = .048) and week 6 (P = .013), whereas peak vertical ground reaction force increased during the four continuous CMJ from baseline to week 3 (P = .048) and week 6 (P = .025) for both groups. CONCLUSIONS: The lower relative WV load used in this study failed to elicit significant improvements in jump and sprint performance in comparison with routine training, or that which have been found in past investigations with elite male athletes completing high-intensity performance tasks with greater WV loads.

Impact of occupational footwear and workload on postural stability in work safety.

BACKGROUND: The impact of occupational footwear and workload on postural stability has been studied previously to prevent fall-related workplace injuries. OBJECTIVE: The purpose of this study was to assess the impact of two types of occupational footwear [steel-toed (SB) and tactical (TB) work boots] on human balance, when exposed to physical workload. METHODS: Postural stability was evaluated in eighteen male participants in the following conditions: eyes open (EO), eyes closed (EC), eyes open unstable surface (EOU) and eyes closed unstable surface (ECU). Postural sway parameters were analyzed using a 2×3 repeated measures analysis of variance design [prior to (PRE) and twice post-workload (POST1 & POST2) separated by 10 minutes of rest]. RESULTS: Findings revealed that the use of SB resulted in greater postural stability, which could be attributed to the design characteristics of these footwear and that postural stability was negatively impacted immediately after the workload which could be attributed to the physical exertions during the workload. However, significant differences were limited to ECU with no visual and altered somatosensory feedback. CONCLUSION: Design features on occupational footwear can aid postural stability while physical exertional tasks can be detrimental. Findings can offer design and work-rest scheduling suggestions to improve work safety.

Virtual-Reality-Induced Visual Perturbations Impact Postural Control System Behavior.

BACKGROUND: Virtual reality (VR) is becoming a widespread tool in rehabilitation, especially for postural stability. However, the impact of using VR in a "moving wall paradigm" (visual perturbation), specifically without and with anticipation of the perturbation, is unknown. METHODS: Nineteen healthy subjects performed three trials of static balance testing on a force plate under three different conditions: baseline (no perturbation), unexpected VR perturbation, and expected VR perturbation. The statistical analysis consisted of a 1 × 3 repeated-measures ANOVA to test for differences in the center of pressure (COP) displacement, 95% ellipsoid area, and COP sway velocity. RESULTS: The expected perturbation rendered significantly lower (p < 0.05) COP displacements and 95% ellipsoid area compared to the unexpected condition. A significantly higher (p < 0.05) sway velocity was also observed in the expected condition compared to the unexpected condition. CONCLUSIONS: Postural stability was lowered during unexpected visual perturbations compared to both during baseline and during expected visual perturbations, suggesting that conflicting visual feedback induced postural instability due to compensatory postural responses. However, during expected visual perturbations, significantly lowered postural sway displacement and area were achieved by increasing the sway velocity, suggesting the occurrence of postural behavior due to anticipatory postural responses. Finally, the study also concluded that VR could be used to induce different postural responses by providing visual perturbations to the postural control system, which can subsequently be used as an effective and low-cost tool for postural stability training and rehabilitation.

The Interaction of Cognitive Interference, Standing Surface, and Fatigue on Lower Extremity Muscle Activity.

BACKGROUND: Performing cognitive tasks and muscular fatigue have been shown to increase muscle activity of the lower extremity during quiet standing. A common intervention to reduce muscular fatigue is to provide a softer shoe-surface interface. However, little is known regarding how muscle activity is affected by softer shoe-surface interfaces during static standing. The purpose of this study was to assess lower extremity muscular activity during erect standing on three different standing surfaces, before and after an acute workload and during cognitive tasks. METHODS: Surface electromyography was collected on ankle dorsiflexors and plantarflexors, and knee flexors and extensors of fifteen male participants. Dependent electromyography variables of mean, peak, root mean square, and cocontraction index were calculated and analyzed with a 2 × 2 × 3 within-subject repeated measures analysis of variance. RESULTS: Pre-workload muscle activity did not differ between surfaces and cognitive task conditions. However, greater muscle activity during post-workload balance assessment was found, specifically during the cognitive task. Cognitive task errors did not differ between surface and workload. CONCLUSIONS: The cognitive task after workload increased lower extremity muscular activity compared to quite standing, irrespective of the surface condition, suggesting an increased demand was placed on the postural control system as the result of both fatigue and cognitive task.

Bilateral spatiotemporal postural control impairments are present in participants with chronic ankle instability.

OBJECTIVES: This study evaluated center-of-pressure (COP) and time-to-boundary (TTB) measures of postural control during a Lateral Step-Down Test in participants with chronic ankle instability (CAI). DESIGN: Cohort study. SETTING: Biomechanics laboratory. PARTICIPANTS: Physically active adults with CAI (n = 15) and matched controls (n = 15). MAIN OUTCOME MEASURES: Traditional COP and TTB measures of postural control were computed in the medial/lateral (ML) and anterior/posterior (AP) directions. RESULTS: No significant results were found for the traditional COP measures (p > 0.05). The CAI group exhibited a lower TTB ML absolute minimum on their affected limb compared to the matched limb of the control group (p < 0.001). Additionally, on average the CAI group displayed significantly lower TTB ML mean of minima (p = 0.004) and TTB standard deviation of minima in the ML (p < 0.001) and AP directions (p = 0.002) regardless of limb. CONCLUSIONS: Sensorimotor impairments associated with CAI negatively alter spatiotemporal postural control and may cause a maladaptive reorganization of centrally mediated motor control strategies that results in bilateral postural control deficits during the Lateral Step-Down Test. In addition, traditional COP measures did not reveal any postural control deficits suggesting that a spatiotemporal analysis should be used when assessing postural control in participants with CAI.

Anticipating ankle inversion perturbations during a single-leg drop landing alters ankle joint and impact kinetics.

Anticipatory responses to inversion perturbations can prevent an accurate assessment of lateral ankle sprain mechanics when using injury simulations. Despite recent evidence of the anticipatory motor control strategies utilized during inversion perturbations, kinetic compensations during anticipated inversion perturbations are currently unknown. The purpose of this investigation was to examine the influence of anticipation to an inversion perturbation during a single-leg drop landing on ankle joint and impact kinetics. Fifteen young adults with no lateral ankle sprain history completed unanticipated and anticipated single-leg drop landings onto a 25° laterally inclined platform from a height of 30 cm. One-dimensional statistical parametric mapping (SPM) was used to analyze net ankle moments and ground reaction forces (GRF) during the first 150 ms post-landing, while peak GRFs, time to peak GRF, peak and average loading rates were compared using a dependent samples t-test (p ≤ 0.05). Results from the SPM analysis revealed significantly greater plantar flexion moment from 58 to 83 ms post-landing (p = 0.004; d = 0.64-0.77), inversion moment from 89 to 91 ms post-landing (p = 0.050; d = 0.58-0.60), and medial GRF from 62 to 97 ms post-landing (p < 0.001; d = 1.00-2.39) during the unanticipated landing condition. Moreover, significantly greater peak plantarflexion (p < 0.001; d = 1.10) and peak inversion moment (p = 0.007; d = 0.94), as well as greater peak (p = 0.002; d = 1.03) and average (p = 0.042; d = 0.66) medial loading rates, were found during the unanticipated landing condition. Our findings suggest alterations to ankle joint and impact kinetics occur during a single-leg drop landing when inversion perturbations are anticipated. Researchers and practitioners using drop-landings onto a tilted surface to assess lateral ankle sprain injury risk should consider implementing protocols that mitigate anticipatory responses.