Exploring the influence of individual factors on the perception of mental workload and body postures.

Studies have revealed that physical and mental demands, psychosocial factors, and individual factors can contribute to the development of WMSDs. Yet, much is still unknown regarding the effects of individual characteristics on WMSDs susceptibility. Previous studies discovered people assumed more awkward body postures to perform an activity when the perception of mental workload is higher. This research study explored if individual characteristics such as age, sex, personality, and anxiety help explain changes or differences in the perception of mental workload and body postures assume when performing activities. The study provided evidence that these individual characteristics have a modifying role on perceived mental workload and body postures. The results suggest that perceived mental workload is influenced to a higher extent by individual characteristics such as anxiety, sex, and personality traits. Women have a higher (18.7%) mental workload perception than men. Likewise, NASA-TLX scores are 22% higher for feelers than thinkers. In general, higher perceptions of mental workload were observed in participants with higher anxiety levels. On the other hand, body postures seem to be influenced by different individual factors depending on the nature of the activity. RULA scores increased on average by 13.1% between baseline and time constraint conditions. Larger differences were observed in certain individuals (e.g. introverts (19.7%) and intuitors (13.8%)) across conditions.

This study looked to explore if individual factors such as age, sex, personality, and anxiety have any effect in perceived mental workload and body postures. Participants performed two physical activities under four levels of mental workload. Results indicated that personality traits (sensors/intuitors), anxiety, and sex exhibited the higher contributions.

Development and Reliability of a Visual-Cognitive Reactive Triple Hop Test.

CONTEXT: Current lower-extremity return to sport testing primarily considers the physical status of an athlete; however, sport participation requires continuous cognitive dual-task engagement. Therefore, the purpose was to develop and evaluate the reliability of a visual-cognitive reactive (VCR) triple hop test that simulates the typical sport demand of combined online visual-cognitive processing and neuromuscular control to improve return to sport testing after lower-extremity injury. DESIGN: Test-retest reliability. METHODS: Twenty-one healthy college students (11 females, 23.5 [3.7] y, 1.73 [0.12] m, 73.0 [16.8] kg, Tegner Activity Scale 5.5 [1.1] points) participated. Participants performed a single-leg triple hop with and without a VCR dual task. The VCR task incorporated the FitLight system to challenge peripheral response inhibition and central working memory. Maximum hop distance, reaction time, cognitive errors, and physical errors were measured. Two identical testing visits were separated by 12 to 17 days (14 [1] d). RESULTS: Traditional triple hop (intraclass correlation coefficients: ICC(3,1) = .96 [.91-.99]; standard error of the measurement = 16.99 cm) and the VCR triple hop (intraclass correlation coefficients(3,1) = .92 [.82-.97]; standard error of the measurement = 24.10 cm) both demonstrated excellent reliability for the maximum hop distance, and moderate reliability for the VCR triple hop reaction time (intraclass correlation coefficients(3,1) = .62 [.09-.84]; standard error of the measurement = 0.09 s). On average, the VCR triple hop resulted in a hop distance deficit of 8.17% (36.4 [5.1] cm; P < .05, d = 0.55) relative to the traditional triple hop. CONCLUSIONS: Hop distance on the VCR triple hop had excellent test-retest reliability and induced a significant physical performance deficit when compared with the traditional triple hop assessment. The VCR triple hop reaction time also demonstrated moderate reliability.

Influence of Fatigue on Cognitive-Motor Function During Unanticipated Landings.

BACKGROUND: Physical fatigue and cognitive performance have been suggested as risk factors for an anterior cruciate ligament (ACL) injury, and fatigue has also been demonstrated to reduce cognitive processing. The combined effects of fatigue and lower cognitive function during cognitive-challenging movements may increase knee mechanics associated with the ACL injury risk. HYPOTHESES: We hypothesized that (1) knee mechanics would be detrimentally affected by fatigue and associated with baseline cognitive function and (2) fatigue-induced deleterious changes in cognitive performance and knee mechanics would be correlated. STUDY DESIGN: Descriptive laboratory study. METHODS: A total of 22 athletes completed baseline cognitive testing. After performing maximal vertical jumps, they performed a jump-land-jump task based on unanticipated visual cues. Then, they completed a fatigue protocol including countermovement jumps, among other tasks, until the jump height decreased below 90% of their assessed maximum. Immediately after reaching the first fatigue point, they performed another set of jump-landing tasks, followed by repeating the fatigue protocol until the jump height decreased below 85% of their assessed maximum. After reaching the second fatigue point, they performed a final set of jump-landing tasks and repeated the initial cognitive assessment battery. RESULTS: Mixed-effects models revealed that knee flexion decreased through the fatigue protocol (baseline: 61.8°; midpoint: 61.1°; final: 60.1°; P = .003). Stepwise regression showed that fatigue-worsened attentional control corresponded to smaller knee abduction angles (R2adjusted = 51.68%; ßstandardized = 1.16; P = .001), and worse reaction time after fatigue correlated with increased knee abduction angles (ßstandardized = 0.85; P = .006) after accounting for the role of attentional control. CONCLUSION: Fatigue induced incremental modifications in sagittal-plane knee mechanics during an unanticipated sports movement. In addition, fatigue induced changes in cognitive function related to ACL injury-relevant knee mechanics. CLINICAL RELEVANCE: The novel findings regarding fatigue-dependent changes in injury-relevant biomechanics during cognitively challenging movements represent an extension of recent developments in understanding the role of cognition in the ACL injury risk.

Effects of virtual reality immersion on postural stability during a dynamic transition task.

Dynamic postural stability paradigms with virtual reality (VR) provide a means to simulate real-world postural challenges and induce customised but controlled perturbations. The purpose of this study was to determine the effects of a VR unanticipated perceptual sport perturbation on postural stability compared to traditional methods. Sixteen individuals between the ages of 18-23 years (19.5 ± 1.4 years) with no history of injury within 12 months were recruited. A double-leg to single-leg transition task was performed on a force plate in one of the following conditions: eyes open (EO), eyes closed (EC), a sport video with a standard non-immersive computer monitor (SV), and VR. The VR and SV conditions used a pre-recorded tackle avoidance task video where participants shifted to a leg in the opposite direction of a simulated opponent, while EC and EO were completed with auditory prompts. Relative to the EO condition, EC and VR induced greater postural instability. The largest effect sizes were between VR and EO for path length (g = 3.57), mean velocity anterior-posterior centre of pressure (CoP) (g = 3.65), and mean velocity medial-lateral CoP (g = 3.27). By including VR, the difficulty of a clinically based postural stability task was increased to the level of EC while accounting for the sporting environment.

Associations Between Cognitive Function and ACL Injury-Related Biomechanics: A Systematic Review.

CONTEXT: Does lower baseline cognitive function predispose athletes to ACL injury risk, especially when performing unplanned or dual-task movements? OBJECTIVE: To evaluate the association between cognitive function and biomechanics related to ACL injuries during cognitively challenging sports movements. DATA SOURCES: PubMed (MEDLINE), Web of Science, Scopus, and SciELO databases were searched; additional hand searching was also conducted. STUDY SELECTION: The following inclusion criteria had to be met: participants completed (1) a neurocognitive test, (2) a cognitively challenging sport-related task involving lower limbs, and (3) a biomechanical analysis. The following criteria determined exclusion from the review: studies involving participants with (1) recent or current musculoskeletal injuries; (2) recent or current concussion; (3) ACL surgical reconstruction, reviews of the literature, commentary or opinion articles, and case studies. STUDY DESIGN: Systematic review using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Protocols (PRISMA-P) statement and registered at the International Prospective Register of Systematic Reviews (PROSPERO). LEVEL OF EVIDENCE: Level 3. DATA EXTRACTION: Two of authors independently extracted data and assessed the methodological quality of the articles with the Downs and Black and ROBINS-I checklists, to assess methodological quality and risk of bias, respectively. RESULTS: Six studies with different methodologies and confounding factors were included in this review. Of these 6 studies, 3 were ranked as high-quality, 3 demonstrated a low risk of bias, 2 a moderate risk, and 1 a severe risk. Five studies found a cognitive-motor relationship, with worse cognitive performance associated with increased injury risk, with 1 study reporting the opposite directionality for 1 variable. One study did not identify any interaction between cognitive function and biomechanical outcomes. CONCLUSION: Worse cognitive performance is associated with an increased injury risk profile during cognitively challenging movements.

Characterizing impact and providing perspective by assessing National Biomechanics Day events.

In this Perspective article we make the case for assessing National Biomechanics Day in order to better understand and maximum its impact. We present the opportunities and benefits that exist to assess National Biomechanics Day, as well as suggest assessment resources and tools that can be utilized. A case study is also included that details the ways that including assessment via a pre- and post-National Biomechanics Day survey provided insight into how our event changed student perceptions related to biomechanics, as well as informed us about how we might improve our event in the future.

Effects of cognitive- and motor-dual tasks on postural control regularity following anterior cruciate ligament reconstruction.

BACKGROUND: High injury rates following anterior cruciate ligament reconstruction (ACLR) motivate the need to better understand lingering movement deficiencies following return to sport. Athletic competition involves various types of sensory, motor, and cognitive challenges; however, postural control deficiencies during this spectrum of conditions are not well understood following ACLR. RESEARCH QUESTION: To what extent is postural control altered following ACLR in the presence of sensory, motor, and cognitive challenges, and does postural control correlate with patient-reported symptoms? METHODS: Fourteen individuals following ACLR (4 m/10 f, 21.2 ± 2.4 yr, 76.9 ± 19.1 kg, 1.70 ± 0.14 m) and fourteen matched healthy controls (4 m/10 f, 21.2 ± 1.4 yr, 75.4 ± 15.3 kg, 1.70 ± 0.15 m) participated in the study. Participants completed single-leg balance, ACLR limb or matched side for controls, under four conditions: 1) eyes open, 2) eyes closed, 3) visual-cognitive dual task (i.e., reverse digit span), and 4) motor dual task (i.e., catching a ball). Sample entropy (SEn) was calculated for each balance condition to characterize regularity of center of pressure control. Participants also completed patient-reported outcomes to characterize self-reported knee function, symptoms, and fear. A mixed effects model tested for differences in SEn between balance conditions, and Spearman correlations tested for relationships between SEn and patient-reported outcomes. RESULTS: A significant Group-by-Condition interaction was detected (P = 0.043). While the motor dual task and eyes closed balance conditions were associated with the lowest SEn for both groups, only the visual-cognitive dual task condition demonstrated a significant difference between groups, with the ACLR group having lower SEn [95% confidence interval for ΔSEn: (0.03, 0.35)]. Lower KOOS-Sport scores were associated with decreased SEn for the ACLR group (ρ = 0.81, P < 0.001). SIGNIFICANCE: These findings are consistent with ACLR individuals using a less automatic approach to postural control compared to controls, particularly when presented with a visual-cognitive challenge. Altered neuromuscular control persists well after ACLR surgery and can be related to patient-reported outcomes.

Development and reliability of a visual-cognitive medial side hop for return to sport testing.

OBJECTIVES: To develop and evaluate the reliability of a new visual-cognitive medial side hop (VCMH) test that challenges physical and cognitive performance to potentially improve return to sport testing. DESIGN: Test-retest experimental design. SETTING: Laboratory. PARTICIPANTS: Twenty-two healthy college students participated (11 females; 23.5 ± 3.64 years; 172.9 ± 11.58 cm; 74.1 ± 17.25 kg; Tegner Score 5.6 ± 1.1). MAIN OUTCOME MEASURES: Subjects performed a medial side hop for distance with and without a visual-cognitive task (VCMH). Maximum hop distance and cognitive errors were measured. RESULTS: There was strong reliability for the traditional medial side hop (ICC3,1 = 0.88[0.72, 0.95]; SEM = 7.16 cm) and VCMH distances (ICC3,1 = 0.86[0.66, 0.94]; SEM = 6.82 cm). Maximum hop distance was significantly lower during the VCMH (86.9 ± 18.2 cm) compared to the traditional medial side hop (96.3 ± 20.7 cm; p < 0.05; d = 0.74), with a performance deficit of 9.69%. CONCLUSION: The VCMH has high test-retest reliability and resulted in a significant dual-task cost with a reduction in physical performance when compared to the traditional medial side hop.

Influence of serial subtraction tasks on transient characteristics of postural control.

We sought to better understand the influence of cognitive perturbations on transient aspects of postural control. Twenty healthy, younger adults had their postural control assessed during eyes open quiet stance. Participants completed three different conditions that either had no cognitive perturbation present, an easy cognitive perturbation (i.e., serial subtraction by ones), or a more difficult cognitive perturbation (i.e., serial subtraction by sevens). All trials finished with 60 s of undisturbed eyes open quiet stance, which was the focus of the balance assessment. 95% confidence ellipse area (EA) was calculated for 5-s epochs throughout the trial. The difference in EA from the first epoch after participants started (onset) or stopped (offset) the cognitive task to the last epoch of the trial (i.e., 55-60 s after perturbation) was used to characterize transient postural control behavior. Functional near-infrared spectroscopy was also used to quantify changes in prefrontal cortex activation during the counting tasks to support interpretation of the transient balance findings. There was a significant effect of condition for transient balance characteristics following a cognitive perturbation (P < 0.001), with greater transient increases in postural sway for both difficult (Cohen's d = 0.40, P < 0.001) and easier (Cohen's d = 0.29, P = 0.013) cognitive perturbations relative to no cognitive perturbation. The onset of cognitive tasks was also associated with greater transient increases in postural sway than the offset of the cognitive tasks (Cohen's d = 0.24, P = 0.019). The functional near-infrared spectroscopy data indicated that a significant decrease in deoxygenated hemoglobin was observed for left Brodmann area 46 for both the subtraction by ones (T = -3.97; Benjamini-Hochberg significance value (q) = 0.008) and subtraction by sevens (T = -3.11; q = 0.036) conditions relative to the baseline condition. The subtraction by sevens condition was also associated with a relative increase in deoxygenated hemoglobin for the right Brodmann area 9 (T = 3.36; q = 0.026) compared to the subtraction by ones condition. In conclusion, serial subtraction can elicit transient increases in postural sway, with more difficult tasks and the onset of the cognitive-motor challenge exhibiting magnified effects. Additionally, even the cessation of a cognitive task (i.e., serial subtraction) can be associated with lingering perturbing effects on balance control.

Quantifying national biomechanics day's impact on student perceptions toward biomechanics: A multisite pilot study.

National Biomechanics Day (NBD) is an international celebration of biomechanics that seeks to increase the awareness and appreciation of biomechanics among the high school community. Initial research supports the positive effects of NBD on students' attitudes toward the field of biomechanics; however, quantitative evidence remains scarce. The purpose of this study was to quantify changes in high school students' perceptions toward biomechanics after participating in NBD events to better understand the impact of NBD. Data were collected at two locations during the 2019 NBD season. Surveys were collected before and after NBD events for 112 high school students from Montana and North Carolina. Paired pre- versus post-NBD surveys for the aggregate sample population suggest that students perceived biomechanics as more appealing (p = 0.050), exciting (p = 0.007), and important (p = 0.018) following the NBD events. Students did not report a change in whether they could see themselves in a biomechanics-related career (p = 0.49). These findings further support the ability for NBD events to positively impact students' perceptions toward biomechanics, although opportunities persist to increase student career interest in biomechanics. This paper presents and discusses the study's results, interpretations, limitations, and implications for future research on biomechanics outreach activities.

Evaluating the Spectrum of Cognitive-Motor Relationships During Dual-Task Jump Landing.

Cognitive function plays a role in understanding noncontact anterior cruciate ligament injuries, but the research into how cognitive function influences sport-specific movements is underdeveloped. The purpose of this study was to determine how various cognitive tasks influenced dual-task jump-landing performance along with how individuals' baseline cognitive ability mediated these relationships. Forty female recreational soccer and basketball players completed baseline cognitive function assessments and dual-task jump landings. The baseline cognitive assessments quantified individual processing speed, multitasking, attentional control, and primary memory ability. Dual-task conditions for the jump landing included unanticipated and anticipated jump performance, with and without concurrent working memory and captured visual attention tasks. Knee kinematics and kinetics were acquired through motion capture and ground reaction force data. Jumping conditions that directed visual attention away from the landing, whether anticipated or unanticipated, were associated with decreased peak knee flexion angle (P < .001). No interactions between cognitive function measures and jump-landing conditions were observed for any of the biomechanical variables, suggesting that injury-relevant cognitive-motor relationships may be specific to secondary task demands and movement requirements. This work provides insight into group- and subject-specific effects of established anticipatory and novel working memory dual-task paradigms on the neuromuscular control of a sport-specific movement.

Postural stability during visual-based cognitive and motor dual-tasks after ACLR.

OBJECTIVES: Determine the effect of visual-based motor and cognitive dual tasking on postural stability in those with anterior cruciate ligament reconstruction relative to matched controls. DESIGN: Cohort study. METHODS: Fourteen volunteers with history of anterior crucaite ligament reconstruction were matched with fourteen healthy controls. Participants performed single leg balance tasks under 4 conditions: (1) single leg balance with eyes-open, (2) single leg balance while catching a ball (dual-motor), (3) single leg balance while repeating a string of numbers in reverse order after viewing them (dual-cognitive) and (4) single leg balance with eyes-closed. Participants completed several patient-reported outcomes of knee function. Mixed effects models were used to identify group differences on the center of pressure measures of ellipse area and root-mean-squared excursion (medial-lateral and anterior-posterior). The mixed models included subject pair as a random factor and group (control, anterior cruciate liagement reconstruction), balance condition (eyes-open, eyes-closed, dual-cognitive, and dual-motor), and group*condition as fixed effects. Tukey post-hoc pairwise comparisons were performed for significant interaction and main effects with an α=0.05. RESULTS: A significant group by condition interaction was observed for ellipse area and medial-lateral root-mean-squared excursion. The anterior cruciate ligament reconstruction group had higher ellipse area (p=0.002, d=0.44) and medial-lateral root-mean-squared excursion (p<0.001, d=0.49). CONCLUSIONS: Postural stability is greatly impaired under eyes-closed and dual-motor conditions relative to eyes-open. Anterior cruciate ligament reconstructed individuals have greater postural instability during the dual-cognitive condition that may indicate unique neural processing deficits remain following anterior cruciate ligament reconstruction.

A new perspective on transient characteristics of quiet stance postural control.

Postural control provides insight into health concerns such as fall risk but remains relatively untapped as a vital sign of health. One understudied aspect of postural control involves transient responses within center of pressure (CoP) data to events such as vision occlusion. Such responses are masked by common whole-trial analyses. We hypothesized that the transient behavior of postural control would yield unique and clinically-relevant information for quiet stance compared to traditionally calculated whole-trial CoP estimates. Three experiments were conducted to test different aspects of this central hypothesis. To test whether transient, epoch-based characteristics of CoP estimates provide different information than traditional whole-trial estimates, we investigated correlations between these estimates for a population of young adults performing three 60-second trials of quiet stance with eyes closed. Next, to test if transient behavior is a result of sensory reweighting after eye closure, we compared transient characteristics between eyes closed and eyes open conditions. Finally, to test if there was an effect of age on transient behavior, we compared transient characteristics during eyes closed stance between populations of young and older adults. Negligible correlations were found between transient characteristics and whole-trial estimates (p>0.08), demonstrating limited overlap in information between them. Additionally, transient behavior was exaggerated during eyes closed stance relative to eyes open (p<0.044). Lastly, we found that transient characteristics were able to distinguish between younger and older adults, supporting their clinical relevance (p<0.029). An epoch-based approach captured unique and potentially clinically-relevant postural control information compared to whole-trial estimates. While longer trials may improve the reliability of whole-trial estimates, including a complementary assessment of the initial transient characteristics may provide a more comprehensive characterization of postural control.

Reducing Core Stability Influences Lower Extremity Biomechanics in Novice Runners.

PURPOSE: The role of core stability in running and its influence on injury risk in runners is not well understood. The purpose of this study was to investigate the effect of core stability (and core fatigue) on running mechanics. We hypothesized that decreasing core stability in novice runners would result in altered running mechanics previously associated with increased risk for common lower extremity running injuries. METHODS: Three-dimensional running kinematics and kinetics and seated postural sway on an unstable surface were collected on 25 healthy, novice runners before and after they performed a core stability knockdown protocol (CSKP), designed to temporarily reduce participants' core stability in a single testing session. RESULTS: Linear mixed models demonstrated that the CSKP resulted in an increased peak knee flexion moment (0.51%BW·ht increase, effect size = 0.49, P = 0.021) and a decreased vertical average loading rate (4.5 BW·s decrease, effect size = 0.44, P = 0.037) during running, but no significant changes in peak knee adduction moment, knee adduction impulse, hip adduction moment, hip adduction impulse, or peak vertical ground reaction force (all P > 0.05). Of 25 runners, 20 demonstrated a measurable decrement in their core stability as defined by their seated postural sway center of pressure excursion changing more than the standard error of measurement of 76 mm. CONCLUSIONS: An experimentally induced decrement in core stability in novice runners caused an increased peak knee flexion moment during stance, which has previously been associated with increased patellofemoral contact pressure during running. Therefore, these results demonstrate that insufficient core stability in novice runners may be a risk factor for developing patellofemoral pain. Other results did not support a role of core stability in other common overuse running injuries in this population.

Exploring the Roles of Central and Peripheral Nervous System Function in Gait Stability: Preliminary Insights from Cancer Survivors.

BACKGROUND: Impairments in central and/or peripheral nervous systems are known to be associated with altered gait; however, the interplay between cognitive function, peripheral sensation, and orbital gait stability remains largely unclear. Elucidating these relationships is expected to provide a clearer understanding of potential fall risk factors across various populations and targets for novel interventions. Many patients diagnosed with cancer are treated with chemotherapy agents known to be neurotoxic to the central and/or peripheral nervous systems that can contribute to movement deficiencies, making this population a novel model to investigate these relationships. RESEARCH QUESTION: The purpose of this exploratory study was to investigate how central and peripheral nervous system impairments associate with orbital stability during single- and dual-task gait. METHODS: Twenty cancer survivors were enrolled and separated into three groups: no prior chemotherapy exposure (CON, n = 6), and prior treatment with chemotherapy and having no/mild chemotherapy-induced peripheral neuropathy (CIPN) symptoms (-CIPN, n = 8) or moderate/severe CIPN symptoms (+CIPN, n = 6). Testing included single- and dual-task (i.e., serial sevens) treadmill walking as well as a computerized test of executive function. Maximum Floquet multipliers were calculated to assess orbital stability during gait. RESULTS: Worse executive function was associated with decreased orbital stability during the dual-task condition in the +CIPN group (Spearman's ρ = 0.94, P = 0.017). Additionally, decreased orbital stability during dual-task gait was observed for the -CIPN group compared to the CON group (ES = 1.96, P = 0.019). SIGNIFICANCE: Executive dysfunction was associated with decreased gait stability during challenging dual-task gait in survivors with sensory symptoms of CIPN. The association between combined central and peripheral nervous system impairments and decreased gait stability in cancer survivors provides a novel demonstration of potential compensatory strategies that accompany deficiencies in these functions. Future work is needed to confirm these relationships and whether they hold in other populations.

Visual-Spatial Memory Deficits Are Related to Increased Knee Valgus Angle During a Sport-Specific Sidestep Cut.

BACKGROUND: Identifying athletes at an increased risk of injury is a promising approach to improve the effect of injury prevention interventions; however, it requires first identifying the potential athlete-specific risk factors. Cognitive ability was recently shown to correlate with noncontact anterior cruciate ligament injury rates and lower extremity mechanics, marking an underexplored area. A better understanding of how individuals' cognitive ability is associated with neuromuscular control during sport-specific tasks may improve injury prevention. HYPOTHESIS: Athletes with lower cognitive performance on a standardized cognitive assessment would demonstrate greater increases in knee valgus angle and moment when performing a sidestep cut with soccer ball dribbling versus without. Visual-spatial memory was expected to demonstrate stronger relationships than reaction time or processing speed. STUDY DESIGN: Descriptive laboratory study. METHODS: Fifteen male collegiate club soccer players participated (mean ± SD: 20.7 ± 2.0 years, 1.78 ± 0.07 m, 76.5 ± 8.9 kg). Participants performed anticipated 45° run-to-cut trials with and without a dual task of dribbling a soccer ball. Peak early-stance knee valgus angle and moment for the plant limb were calculated. Participants also completed a cognitive assessment to evaluate visual memory, verbal memory, reaction time, and processing speed. These composite scores were entered as candidate predictors for a stepwise regression analysis on the dual-task change scores in lower extremity biomechanical parameters (ie, ball handling - non-ball handling). RESULTS: Visual memory composite score (a measure of visual-spatial memory) was the only cognitive outcome significantly associated with the change in biomechanical parameters. Each unit decrease in the visual memory composite score was associated with an increase of 0.21°± 0.05° in peak knee valgus angle during the ball-handling task as compared with the non-ball handling task ( R2 = 52%, P = .003). CONCLUSION: Visual-spatial memory was associated with neuromuscular control during a sidestep cutting task during soccer ball dribbling, with deficits in this cognitive domain being associated with increased peak knee valgus angle. CLINICAL RELEVANCE: Assessing visual-spatial memory ability may provide useful information to better understand conditions associated with impaired neuromuscular control and to potentially identify athletes at an elevated risk for musculoskeletal injury.

Impaired Postural Control and Altered Sensory Organization During Quiet Stance Following Neurotoxic Chemotherapy: A Preliminary Study.

Individuals diagnosed with chemotherapy-induced peripheral neuropathy (CIPN) demonstrate impaired balance and carry an increased risk of falling. However, prior investigations of postural instability have only compared these individuals against healthy controls, limiting the understanding of impairments associated with CIPN. Therefore, the purpose of this study was to better isolate postural control impairments that are associated with CIPN. Twenty cancer survivors previously diagnosed with breast or colorectal cancer participated. Participants were separated into 3 groups: no prior chemotherapy exposure (CON, n = 6), and recent treatment with taxane- or oxaliplatin-based chemotherapy with no/mild symptoms of CIPN (-CIPN, n = 8) or moderate/severe symptoms of CIPN (+CIPN, n = 6). Postural control was assessed by measuring center of pressure during standing balance conditions that systematically interfered with somatosensory, visual, and/or vestibular information. The presence of CIPN sensory symptoms was associated with impaired postural control, particularly during eyes-closed balance conditions ( P < .05). Additionally, medial-lateral postural instability was more pronounced in the +CIPN group compared with the -CIPN group and CON participants ( P < .05). Greater postural instability during eyes-closed balance in individuals with CIPN is consistent with impaired peripheral sensation. Balance impairments in cancer survivors with CIPN demonstrate the unique challenges in this population and motivate the need for targeted efforts to mitigate postural control deficits that have previously been associated with fall risk.

Characterizing within-subject variability in quantified measures of balance control: A cohort study.

BACKGROUND: To longitudinally assess individuals using quantified measures, we must characterize within-subject variability (WSV) of the measures. RESEARCH QUESTION: What is the natural within-subject variability (WSV) that can be expected in postural control over 3+ days? METHODS: Thirteen individuals without orthopedic or neurologic impairment (mean(SD) = 55 (9) years; 76 (18) kg; 11 females/2 males) were recruited from a community workplace and consented to participate. Participants stood quietly with eyes closed (QEC) on a force platform (5 x 1 min x 6 days) in two stances: comfortable and narrow. We recorded center of pressure (COP) and calculated COP-based balance parameters. To analyze variance components, we applied a linear mixed model for repeated measures, calculating within-subject standard deviation (SDws) from the pooled variance not attributable to between-subject variability. To estimate WSV, we scaled SDws by a confidence interval (CI) factor (e.g. WSV at the 95%CI = WSV95 = SDws * 1.96) and report WSV95 for a range of conditions previously reported in the literature and the following measures previously found sensitive to or predictive of health: (primary) WSV95 of root-mean square amplitude of medial-lateral COP during QEC (RMSml); (secondary) WSV95 of COP ellipse area (COPa); (secondary) WSV95 of mean medial-lateral COP velocity (COPvml) during QEC. RESULTS: WSV95 was estimated at RMSml = 0.8 mm, COPa = 99mm2, and COPvml = 1.1 mm/s among healthy, middle-aged participants standing comfortably for one recommended data duration (4 × 30 s trials). A look up table provides values for alternate protocols that have been suggested in the literature and might prove relevant for clinical translation. SIGNIFICANCE: This work advances longitudinal assessment of individuals using quantified measures of postural control. Results enable practitioners/researchers to assess an individual's progress, maintenance, or decline relative to WSV at a defined CI level.

Gait, balance, and patient-reported outcomes during taxane-based chemotherapy in early-stage breast cancer patients.

BACKGROUND: Chemotherapy-induced peripheral neuropathy (CIPN) is a dose-limiting toxicity of several commonly used chemotherapy drugs including taxanes, vinca alkaloids, and platinum compounds. Development of CIPN is highly variable, both in self-reported symptoms and functional consequences, and can be severe enough to alter dose intensity. PURPOSE: To describe the natural histories of both patient-reported symptoms of CIPN and functional impairments in breast cancer patients undergoing taxane-based chemotherapy. METHODS: Thirty-three breast cancer patients (32 female/1 male; 47.8 ± 11.2 years; n = 17 stage II/n = 16 stage III) were enrolled. Patients completed self-reports of symptoms and function (e.g., EORTC QLQ-CIPN20) and objective measures of physical function (i.e., balance and gait testing) in an outpatient oncology clinic at five timepoints: (1) baseline-prior to starting chemotherapy, (2-4) before starting subsequent chemotherapy cycles, and (5) 1-3 months after receiving their last taxane infusion. RESULTS: Significant negative changes in both patient-reported outcomes and objective functional measures were observed. Decreased balance was observed after the first chemotherapy cycle (28% increase in medial-lateral excursion of the center of pressure, p = 0.016) and progressed with cumulative exposure (43% increase, p < 0.001). Patients also demonstrated slower walking speeds (5% decrease, p = 0.003) as they progressed through treatment. These functional deficits were mirrored with increased patient-reported symptom severity for all EORTC QLQ-CIPN20 subscales (all p < 0.05). CONCLUSION: This study longitudinally assessed patient-reported outcomes concurrently with balance and gait testing in patients undergoing taxane therapy. Taxane treatment was associated with the development of clinically relevant problems in both CIPN symptoms and patient function.