The aim of this study was to investigate the influence of body fat distribution on postural balance and lower-limb muscle quality in women aged 60 years and over. Two hundred and twenty-two volunteers took part in this cross-sectional analysis. Participants underwent body fat distribution assessment using dual-energy x-ray absorptiometry and were classified as nonobese, gynoid obese, or android obese. Postural balance was assessed during quiet standing, with and without vision restriction, using a force platform. Specific torque was defined as the ratio of knee extensors peak torque (evaluated by an isokinetic dynamometer) to the lean mass of the same limb (evaluated by dual-energy x-ray absorptiometry). Compared with nonobese participants, both obese groups exhibited higher range of postural sway along the anteroposterior and mediolateral axes (P < .05). However, there were no differences between participants with gynoid and android obesity. The android obese group exhibited greater speed of postural sway in the condition without vision restriction than both nonobese (P = .040) and gynoid obese (P = .004) groups. Regarding muscle quality, only participants with gynoid obesity (P = .004) presented lower specific torque than their nonobese peers. These results may be clinically useful when designing falls prevention exercises targeting the obese population.
Silvia G.R. Neri, Juscelia Cristina Pereira, Ana Cristina de David, and Ricardo M. Lima
Manuel J. Escalona, Daniel Bourbonnais, Michel Goyette, Damien Le Flem, Cyril Duclos, and Dany H. Gagnon
The effects of walking speeds on lower-extremity muscle synergies (MSs) were investigated among 20 adults who walked 20 m at SLOW (0.6 ± 0.2 m/s), natural (NAT; 1.4 ± 0.1 m/s), and FAST (1.9 ± 0.1 m/s) speeds. Surface electromyography of eight lower-extremity muscles was recorded before extracting MSs using a nonnegative matrix factorization algorithm. Increasing walking speed tended to merge MSs associated with weight acceptance and limb deceleration, whereas reducing walking speed does not change the number and composition of MSs. Varying gait speed, particularly decreasing speed, may represent a gait training strategy needing additional attention given its effects on MSs.
Stephan G. Bodkin, Jay Hertel, and Joseph M. Hart
Context: Individuals following anterior cruciate ligament reconstruction (ACLR) demonstrate altered postural stability and functional movement patterns. It is hypothesized that individuals following ACLR may compensate with sensory adaptations with greater reliance on visual mechanisms during activities. It is unknown if visual compensatory strategies are implemented to maintain postural stability during functional tasks. Objective: To examine visual gaze accuracy during a single-leg balance task in individuals following ACLR compared with healthy, active controls. Design: Case control. Setting: Controlled laboratory. Participants: A total of 20 individuals (10 ACLR and 10 healthy controls) participated in the study. Data Collection and Analysis: Visual gaze patterns were obtained during 20-second single-leg balance trials while participants were instructed to look at presented targets. During the Stationary Target Task, the visual target was presented in a central location for the duration of the trial. The Moving Target Task included a visual target that randomly moved to 1 of 9 target locations for a period of 2 seconds. Targets were stratified into superior, middle, and inferior levels for the Moving Target Task. Results: The Stationary Target Task demonstrated no differences in visual error between groups (P = .89). The Moving Target Task demonstrated a significant interaction between group and target level (F 2,36 = 3.76, P = .033). Individuals following ACLR demonstrated greater visual error for the superior targets (ACLR = .70 [.44] m, healthy = .41 [.21] m, Cohen d = 0.83 [0.06 to 1.60]) and inferior targets (ACLR = .68 [.25] m, healthy = .33 [.16] m, Cohen d = 1.67 [0.81 to 2.52]). Conclusion: Individuals following ACLR demonstrate greater visual error during settings of high or low visual stimuli compared with healthy individuals to maintain single-limb postural stability. This population may rely on visual input to compensate for the somatosensory changes following injury.
Uri Gottlieb and Shmuel Springer
Context: Arthroscopic surgical repair of the shoulder is recommended when conservative treatment for shoulder instability (SI) fails. However, many patients undergoing this procedure do not return to same level of activity. Psychological factors and muscle strength have been shown to be associated with postoperative outcomes in other musculoskeletal conditions. Objective: To investigate the association between fear avoidance, muscle strength, and short-term function in patients after surgical SI repair. Methods: Twenty-five male patients who underwent shoulder surgery following at least one event of SI were included in this study. Evaluations of fear avoidance related to physical activity and disability were performed at baseline (during the first encounter with the physical therapist) and 7 to 8 weeks postsurgery. Fear avoidance beliefs were assessed using the Fear Avoidance Beliefs Questionnaire. Disability was assessed using the Disabilities of Arm, Shoulder, and Hand questionnaire and the Western Ontario SI index. The follow-up evaluation (weeks 7–8) included measurement of maximal isometric strength of the internal and external rotators. Nonparametric Kendall tau was used to determine the correlations between baseline fear avoidance, muscle strength, and disability at follow-up. Results: Disabilities of Arm, Shoulder, and Hand questionnaire at follow-up was significantly correlated with baseline Disabilities of Arm, Shoulder, and Hand questionnaire (τ = .520, P < .001), baseline fear avoidance (τ = .399, P = .008), and both internal rotator (τ = −.400, P = .005) and external rotator strength (τ = −.353, P = .014). Western Ontario SI index at follow-up was moderately correlated with baseline Western Ontario SI index (τ = .387, P = .007), internal rotator (τ = −.427, P = .003), and external rotator (τ = −.307, P = .032), but not with baseline Fear Avoidance Beliefs Questionnaire (τ = .22, P = .145). Conclusions: The results indicate a possible association between fear avoidance beliefs and short-term disability. Further studies are warranted to better explore and understand these relationships.
Andy Mitchell, Craig Holding, and Matt Greig
Context: Professional soccer players who have sustained a lower limb injury are up to 3× more likely to suffer a reinjury, often of increased severity. Previous injury has been shown to induce compensatory strategies during neuromuscular screening tests, which might mask deficits and lead to misinterpretation of readiness to play based on task outcome measures. Objective: To investigate the influence of previous injury in professional soccer players on countermovement jump (CMJ) performance and movement strategy. Design: Cross-sectional. Setting: Professional soccer club competing in the English Championship (tier 2). Patients (or Other Participants): Outfield players with a minimum of 6 years as a professional. Intervention(s): Players were categorized as previously injured (n = 10) or not injured (n = 10). All players completed double- and single-leg CMJ trials. Main Outcome Measures: CMJ performance was quantified as jump height and flight time:contraction time ratio. CMJ movement strategy was quantified as force–time history, differentiating eccentric and concentric phases and CMJ depth. Results: Double-leg CMJ was not sensitive to previous injury in performance or movement strategy. In contrast, single-leg CMJ performance was impaired in players with previous injury, who generated significantly lower eccentric and concentric peak force and rate of force development, and a deeper countermovement. Impaired single-leg CMJ performance was also evident in the nonaffected limb of previously injured players, suggesting cross-contamination. Hierarchical ordering revealed that the eccentric phase of the CMJ contributed little to performance in previously injured players. In noninjured players, the eccentric rate of force development and concentric peak force were able to account for up to 89% of the variation in CMJ performance. Conclusions: Single-leg CMJ is advocated for player profiling, being more sensitive to previous injury, and negating the opportunity for interlimb compensation strategies. Movement strategy deficits in previously injured players suggest rehabilitation foci specific to eccentric force development.
Zachary Y. Kerr, Julianna Prim, J.D. DeFreese, Leah C. Thomas, Janet E. Simon, Kevin A. Carneiro, Stephen W. Marshall, and Kevin M. Guskiewicz
Context: Little research has examined health-related quality of life in former National Football League (NFL) players. Objective: Examine the association of musculoskeletal injury history and current self-reported physical and mental health in former NFL players. Setting: Cross-sectional questionnaire. Patients or Other Participants: Historical cohort of 2,103 former NFL players that played at least one season between 1940 and 2001. Intervention: Players were grouped by self-reported professional career musculoskeletal injury history and whether injuries affected current health: (1) no musculoskeletal injury history; (2) musculoskeletal injury history, currently affected by injuries; and (3) musculoskeletal injury history, not currently affected by injuries. Main Outcome Measure: The Short Form 36 Measurement Model for Functional Assessment of Health and Well-Being (SF-36) yielded physical and mental health composite scores (PCS and MCS, respectively); higher scores indicated better health. Multivariable linear regression computed mean differences (MD) among injury groups. Covariates included demographics, playing history characteristics, surgical intervention for musculoskeletal injuries, and whether injury resulted in premature end to career. MD with 95% CI excluding 0.00 were deemed significant. Results: Overall, 90.3% reported at least one musculoskeletal injury during their professional football careers, of which 74.8% reported being affected by their injuries at time of survey completion. Adjusting for covariates, mean PCS in the “injury and affected” group was lower than the “no injury” (MD = −3.2; 95% CI: −4.8, −1.7) and “injury and not affected” groups (MD = −4.3; 95% CI: −5.4, −3.3); mean MCS did not differ. Conclusion: Many players reported musculoskeletal injuries, highlighting the need for developing and evaluating injury management interventions.