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William Anderst, Shaquille Charles, Milad Zarei, Ashika Mani, Naomi Frankston, Elliott Hammersley, Gehui Zhang, MaCalus Hogan, and Robert T. Krafty

Studies of human movement usually collect data from multiple repetitions of a task and use the average of all movement trials to approximate the typical kinematics or kinetics pattern for each individual. Few studies report the expected accuracy of these estimated mean kinematics or kinetics waveforms for each individual. The purpose of this study is to demonstrate how simultaneous confidence bands, which is an approach to quantify uncertainty across an entire waveform based on limited data, can be used to calculate margin of error (MOE) for waveforms. Bilateral plantar pressure data were collected from 70 participants as they walked over 4 surfaces for an average of at least 300 steps per surface. The relationship between MOE and the number of steps included in the analysis was calculated using simultaneous confidence bands, and 3 methods commonly used for pointwise estimates: intraclass correlation, sequential averaging, and T-based MOE. The conventional pointwise approaches underestimated the number of trials required to estimate biomechanical waveforms within a desired MOE. Simultaneous confidence bands are an objective approach to more accurately estimate the relationship between the number of trials collected and the MOE in estimating typical biomechanical waveforms.

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Tim L.A. Doyle, AuraLea C. Fain, Jodie A. Wills, Daniel Cooper, Kevin Toonen, and Benjamin Kamphius

The diverse and grueling nature of activities undertaken during Special Forces selection makes it difficult to develop physical training to improve performance and reduce injury risk. It is generally accepted that increased strength is protective against injury, but it is unclear if this is evident in a Special Forces selection environment. This study investigated the effect of the rigors of a Special Forces selection course has on performance of the isometric mid-thigh pull, countermovement jump, squat jump, drop landing, elastic utilization ratio (EUR), and injury occurrence. Throughout the course, 26% of participants sustained a preventable lower limb injury, with 65% of these occurring at the knee. The uninjured had higher values of absolute strength as measured by isometric mid-thigh pull peak absolute force (3399 [371] N, 3146 [307] N; P = .022) and lower EUR (0.94 [0.08], 1.01 [0.09]; P = .025) compared to the injured. Preventable knee injury was significantly correlated with isometric mid-thigh pull (r = −.245, P = .031) and EUR (r = .227, P = .044). The selection course altered EUR for uninjured individuals only (P = .004). Findings indicate that individuals with higher strength levels may be at a lower risk of injury than their weaker counterparts.

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Seong-won Han, Andrew Sawatsky, and Walter Herzog

The purpose of this study was to quantify the contribution of the individual quadriceps muscles to patellar tracking. The individual and/or combined quadriceps muscles were activated in rabbits (n = 6) during computer-controlled flexion/extension of the knee. Three-dimensional patellar tracking was measured for the vastus lateralis, vastus medialis, and rectus femoris when activated alone and when activated simultaneously at different frequencies, producing a range of knee extensor torques. Patellar tracking changed substantially as a function of knee extensor torque and differed between muscles. Specifically, when all quadriceps muscles were activated simultaneously, the patella shifted more medially and proximally and rotated and tilted more medially compared with when vastus lateralis and rectus femoris were activated alone (P < .05), whereas vastus medialis activation alone produced a similar tracking pattern to that observed when all quadriceps muscles were activated simultaneously. Furthermore, patellar tracking for a given muscle condition shifted more medially and proximally and rotated and tilted more medially with increasing knee extensor torques across the entire range of knee joint angles. The authors conclude that patellar tracking depends crucially on knee extensor force/torque and that vastus medialis affects patellar tracking in a distinctly different way than vastus lateralis and rectus femoris, which produce similar tracking patterns.

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Ewa Szczerbik, Malgorzata Kalinowska, and Malgorzata Syczewska

The purpose of the study was to investigate which changes in kinematics and muscle activity in healthy, middle-aged women are introduced to maintain balance on an unstable platform. Biodex Balance System tests were used in stable and unstable modes (sudden with eyes open/closed and gradual with eyes open). Simultaneously, lower-extremity kinematics and surface electromyography of back and legs muscles were captured. The dependence between balance scores, movement ranges, and root mean square of electromyography was assessed with multiple regression to evaluate the strategy used. The results showed multisegmental movements in sudden instability, and activity of at least one of the following muscles: gluteus maximus, erector spinae, and soleus in all conditions. Best balance scores were achieved when movements appeared in pelvis in transverse, and hip in frontal planes, worst when in pelvis in frontal, hip, and ankle in sagittal planes, and when mentioned muscles were activated. Further research is needed to identify the determinants of strategy choice.

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Martha J. Anderson, Yvette Ingram, Linda Meyer, Thomas West, and Ellen West

Collegiate athletes have demonstrated a need for social support to help cope with their daily responsibilities. The purpose of this research was to explore National Collegiate Athletic Association Division II athletes’ perception of social support from friends, teammates, family, coaches, significant others, and athletic trainers following injury, illness, or other identified life stressors. There were 546 participants who completed a five-part survey using the University Stress Scale, the Multidimensional Scale of Perceived Social Support, the Athletic Multidimensional Scale of Perceived Social Support, the Perceived Stress Scale, and a demographic section. Of the participants, 352 (64.5%) stated that they experienced moderate stress levels, and all participants indicated experiencing an identified life stressor within the last 12 months. The results indicated statistically significant differences when comparing providers of social support: females preferred the support of friends, significant others, and athletic trainers, and freshmen and sophomores perceived more social support from friends than did juniors and seniors.

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Tsz Lun (Alan) Chu, Ellea Bachmeier, and Taylor Mair

Qualitative research has demonstrated the prevalence of gender inequity and sexism in sport-related careers, including those in sport psychology. To provide quantitative evidence, we examined the role of gender in Certified Mental Performance Consultants’ (CMPC) specialization and employment by extracting and coding the data (N = 576) from the CMPC Directory. Independent samples t tests showed that male CMPCs specialized in more masculine sports, less feminine sports, and a similar number of gender-neutral sports compared with female CMPCs. Chi-square tests of independence revealed a larger proportion of male than female CMPCs working in professional sport. No significant differences were found in other employment settings (college sport, military, and private practice), age-group specialization, and mental health licensure. These findings, which should be interpreted with caution before further investigation, suggest a need for collaboration between sport psychology professionals and sport organizations that might help mitigate internal and external barriers to gender equity.

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Rafael F. Escamilla, Naiquan Zheng, Toran D. MacLeod, Rodney Imamura, Shangcheng Wang, Kevin E. Wilk, Kyle Yamashiro, and Glenn S. Fleisig

The objective was to assess how patellofemoral loads (joint force and stress) change while lunging with step length and step height variations. Sixteen participants performed a forward lunge using short and long steps at ground level and up to a 10-cm platform. Electromyography, ground reaction force, and 3D motion were captured, and patellofemoral loads were calculated as a function of knee angle. Repeated-measures 2-way analysis of variance (P < .05) was employed. Patellofemoral loads in the lead knee were greater with long step at the beginning of landing (10°–30° knee angle) and the end of pushoff (10°–40°) and greater with short step during the deep knee flexion portion of the lunge (50°–100°). Patellofemoral loads were greater at ground level than 10-cm platform during lunge descent (50°–100°) and lunge ascent (40°–70°). Patellofemoral loads generally increased as knee flexion increased and decreased as knee flexion decreased. To gradually increase patellofemoral loads, perform forward lunge in the following sequence: (1) minimal knee flexion (0°–30°), (2) moderate knee flexion (0°–60°), (3) long step and deep knee flexion (0°–100°) up to a 10-cm platform, and (4) long step and deep knee flexion (0°–100°) at ground level.

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Morgan Cleveringa and E. Andrew Pitchford

Adults with intellectual disabilities have increasing life expectancy but may be susceptible to early aging-related conditions. The purpose of this study was to examine associations between the presence of low muscle strength, low bone mineral density, and high body mass index with age and sex in adult Special Olympics athletes. Grip strength (n = 6,477; 40.9% female), chair stand time (n = 6,444; 40.5% female), body mass index (n = 7,824; 43.7% female), and bone mineral density (n = 3,091; 43.2% female) measurements were provided by Special Olympics International. Poor grip strength, chair stand time, bone mineral density, and body mass index were identified in 43.8%, 46.2%, 28.7%, and 50.3% of each sample, respectively. Increasing age was a risk factor for all conditions (odds ratio = 1.30–10.89; p < .05). High rates of adverse health conditions were observed in a sample of adults with intellectual disabilities. Increased risk was observed as early as the fourth decade of life.