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Arthur Alves Dos Santos, James Sorce, Alexandra Schonning and Grant Bevill

This study evaluated the performance of 6 commercially available hard hat designs—differentiated by shell design, number of suspension points, and suspension tightening system—in regard to their ability to attenuate accelerations during vertical impacts to the head. Tests were conducted with impactor materials of steel, wood, and lead shot (resembling commonly seen materials in a construction site), weighing 1.8 and 3.6 kg and dropped from 1.83 m onto a Hybrid III head/neck assembly. All hard hats appreciably reduced head acceleration to the unprotected condition. However, neither the addition of extra suspension points nor variations in suspension tightening mechanism appreciably influenced performance. Therefore, these results indicate that additional features available in current hard hat designs do not improve protective capacity as related to head acceleration metrics.

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Courtney M. Butowicz, Julian C. Acasio and Brad D. Hendershot

Altered trunk movements during gait in persons with lower-limb amputation are often associated with an increased risk for secondary health conditions; however, the postural control strategies underlying such alterations remain unclear. In this secondary analysis, the authors employed nonlinear measures of triplanar trunk accelerations via short-term Lyapunov exponents to investigate trunk local stability as well as spatiotemporal gait parameters to describe gait mechanics. The authors also evaluated the influence of a concurrent task on trunk local stability and gait mechanics to explore if competition for neuromuscular processing resources can assist in identifying unique strategies to control kinematic variability. Sixteen males with amputation—8 transtibial and 8 transfemoral—and 8 uninjured males (controls) walked on a treadmill at their self-selected speed (mean = 1.2 m/s ±10%) in 5 experimental conditions (8 min each): 4 while performing a concurrent task (2 walking and 2 seated) and 1 with no concurrent task. Individuals with amputation demonstrated significantly smaller Lyapunov exponents than controls in all 3 planes of motion, regardless of concurrent task or level of amputation (P < .0001). Individuals with transfemoral amputation walked with wider strides compared with individuals with transtibial amputation and controls (P < .0001). Individuals with amputation demonstrated more trunk kinematic variability in the presence of wider strides compared with individuals without amputation, and it appears that performing a concurrent cognitive task while walking did not change trunk or gait mechanics.

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Yumeng Li, Jupil Ko, Marika A. Walker, Cathleen N. Brown and Kathy J. Simpson

The purpose of the present study was to examine the effect of chronic ankle instability (CAI) on lower-extremity joint coordination and stiffness during landing. A total of 21 female participants with CAI and 21 pair-matched healthy controls participated in the study. Lower-extremity joint kinematics were collected using a 7-camera motion capture system, and ground reaction forces were collected using 2 force plates during drop landings. Coupling angles were computed based on the vector coding method to assess joint coordination. Coupling angles were compared between the CAI and control groups using circular Watson–Williams tests. Joint stiffness was compared between the groups using independent t tests. Participants with CAI exhibited strategies involving altered joint coordination including a knee flexion dominant pattern during 30% and 70% of their landing phase and a more in-phase motion pattern between the knee and hip joints during 30% and 40% and 90% and 100% of the landing phase. In addition, increased ankle inversion and knee flexion stiffness were observed in the CAI group. These altered joint coordination and stiffness could be considered as a protective strategy utilized to effectively absorb energy, stabilize the body and ankle, and prevent excessive ankle inversion. However, this strategy could result in greater mechanical demands on the knee joint.

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Matthew S. Briggs, Claire Spech, Rachel King, Mike McNally, Matthew Paponetti, Sharon Bout-Tabaku and Laura Schmitt

Obese (OB) youth demonstrate altered knee mechanics and worse lower-extremity performance compared with healthy weight (HW) youth. Our objectives were to compare sagittal plane knee landing mechanics between OB and HW youth and to examine the associations of knee and hip extension peak torque with landing mechanics in OB youth. Twenty-four OB and 24 age- and sex-matched HW youth participated. Peak torque was measured and normalized to leg lean mass. Peak knee flexion angle and peak internal knee extension moment were measured during a single-leg hop landing. Paired t tests, Pearson correlation coefficients, and Bonferroni corrections were used. OB youth demonstrated worse performance and lower knee extension (OB: 12.76 [1.38], HW: 14.03 [2.08], P = .03) and hip extension (OB: 8.59 [3.13], HW: 11.10 [2.89], P = .005) peak torque. Furthermore, OB youth demonstrated lower peak knee flexion angles (OB: 48.89 [45.41 to 52.37], HW: 56.07 [52.59 to 59.55], P = .02) and knee extension moments (OB: −1.73 [−1.89 to −1.57], HW: −2.21 [−2.37 to −2.05], P = .0001) during landing compared with HW youth. Peak torque measures were not correlated with peak knee flexion angle nor internal knee extension moment during landing in either group (P > .01). OB youth demonstrated altered landing mechanics compared with HW youth. However, no associations among peak torque measurements and knee landing mechanics were present.

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Jereme B. Outerleys, Michael J. Dunbar, Glen Richardson, Cheryl L. Hubley-Kozey and Janie L. Astephen Wilson

Total knee arthroplasty (TKA) surgery improves knee joint kinematics and kinetics during gait for most patients, but a lack of evidence exists for the level and incidence of improvement that is achieved. The objective of this study was to quantify patient-specific improvements in knee biomechanics relative to osteoarthritis (OA) severity levels. Seventy-two patients underwent 3-dimensional (3D) gait analysis before and 1 year after TKA surgery, as well as 72 asymptomatic adults and 72 with moderate knee OA. A combination of principal component analysis and discriminant analyses were used to categorize knee joint biomechanics for patients before and after surgery relative to asymptomatic, moderate, and severe OA. Post-TKA, 63% were categorized with knee biomechanics consistent with moderate OA, 29% with severe OA, and 8% asymptomatic. The magnitude and pattern of the knee adduction moment and angle (frontal plane features) were the most significant contributors in discriminating between pre-TKA and post-TKA knee biomechanics. Standard of care TKA improves knee biomechanics during gait to levels most consistent with moderate knee OA and predominately targets frontal plane features. These results provide evidence for the level of improvement in knee biomechanics that can be expected following surgery and highlight the biomechanics most targeted by surgery.

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Samantha M. Ross, Ellen Smit, Joonkoo Yun, Kathleen R. Bogart, Bridget E. Hatfield and Samuel W. Logan

A secondary data analysis of 33,093 children and adolescents age 6–17 years (12% with disabilities) from a 2016–2017 National Survey of Children’s Health nonrepresentative sample aimed to identify (a) unique clusters of sociodemographic characteristics and (b) the relative importance of disability status in predicting participation in daily physical activity (PA) and sports. Exploratory classification tree analyses identified hierarchical predictors of daily PA and sport participation separately. Disability status was not a primary predictor of daily PA. Instead, it emerged in the fifth level after age, sex, body mass index, and income, highlighting the dynamic intersection of disability with sociodemographic factors influencing PA levels. In comparison, disability status was a second-level predictor for sport participation, suggesting that unique factors influencing PA level are likely experienced by disabled children and adolescents. The authors employ an intersectionality lens to critically discuss implications for research in adapted PA.

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Cagla Ozkul, Arzu Guclu-Gunduz, Kader Eldemir, Yasemin Apaydin, Cagri Gulsen, Gokhan Yazici, Fatih Soke and Ceyla Irkec

This study aimed to investigate the dual-task cost of both motor and cognitive performances in patients with multiple sclerosis (PwMS) and in healthy controls and to determine their relationships with clinical features in PwMS. The participants performed motor tasks (postural stability, walking, and manual dexterity) and cognitive tasks (mental tracking and verbal fluency) under single- and dual-task conditions. The results showed that postural stability under dual-task conditions did not change, whereas walking and manual dexterity deteriorated, regardless of the concurrent cognitive task, in PwMS (median Expanded Disability Status Scale score: 1) and the healthy controls. Verbal fluency decreased during postural stability, whereas it increased during walking, and it was maintained during manual dexterity in both groups. Mental tracking did not change during walking; it declined during manual dexterity in both groups. Mental tracking during postural stability deteriorated in PwMS, while it did not change in the healthy controls. In general, dual-task costs were associated with baseline performances of tasks rather than clinical features. Therefore, baseline performances of both tasks should be increased for improving dual-task performance in PwMS.

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Julie Freedman, Sally Hage and Paula A. Quatromoni

Male athletes are underrepresented in eating disorders research. This phenomenological study investigated the experiences of male athletes who self-identified as having an eating disorder, disordered eating, or compulsive exercise behaviors. Eight male collegiate athletes were interviewed, and qualitative analysis identified factors associated with the onset and maintenance of disordered behaviors. Among the novel findings was the salient influence of social media as a driver of body dissatisfaction and disordered behaviors. The participants described a perceived sense of control and feeling of pride associated with the use of behaviors, cultural norms in a male sport environment that sustained these behaviors, and a shared belief that, until they experienced a loss of control over their use of behaviors, they would not likely ask for help or seek treatment. These findings have implications for additional research, as well as individual and systems-level strategies for the prevention, screening, and treatment of eating and exercise disorders in male sport.

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Matthew D. Bird, Eadie E. Simons and Patricia C. Jackman

Mental toughness has been associated with factors related to psychological well-being, but little is known about its relationship with stigma toward mental health and mental health help-seeking. This study investigated the relationship between mental toughness, sport-related well-being, and personal stigma toward mental health in a sample of 154 National Collegiate Athletic Association Division I student-athletes. The moderating effect of mental toughness on the relationship between public stigma and self-stigma toward mental health help-seeking was also explored. Mental toughness was significantly and positively associated with sport-related well-being, but not significantly related to personal stigma toward mental health. Moderation analysis indicated that mental toughness was not a significant moderator of the relationship between public stigma and self-stigma, but higher levels of mental toughness were significantly associated with lower levels of stigma toward mental health help-seeking. Building mental toughness may be a way to increase well-being and to reduce stigma toward help-seeking in student-athletes.