Lower Extremity Landing Biomechanics in Both Sexes After a Functional Exercise Protocol

Context

Sex differences in landing biomechanics play a role in increased rates of anterior cruciate ligament (ACL) injuries in female athletes. Exercising to various states of fatigue may negatively affect landing mechanics, resulting in a higher injury risk, but research is inconclusive regarding sex differences in response to fatigue.

Objective

To use the Landing Error Scoring System (LESS), a valid clinical movement-analysis tool, to determine the effects of exercise on the landing biomechanics of males and females.

Design

Cross-sectional study.

Setting

University laboratory.

Patients or Other Participants

Thirty-six (18 men, 18 women) healthy college-aged athletes (members of varsity, club, or intramural teams) with no history of ACL injury or prior participation in an ACL injury-prevention program.

Intervention(s)

Participants were videotaped performing 3 jump-landing trials before and after performance of a functional, sportlike exercise protocol consisting of repetitive sprinting, jumping, and cutting tasks.

Main Outcome Measure(s)

Landing technique was evaluated using the LESS. A higher LESS score indicates more errors. The mean of the 3 LESS scores in each condition (pre-exercise and postexercise) was used for statistical analysis.

Results

Women scored higher on the LESS (6.3 ± 1.9) than men (5.0 ± 2.3) regardless of time (P = .04). Postexercise scores (6.3 ± 2.1) were higher than preexercise scores (5.0 ± 2.1) for both sexes (P = .01), but women were not affected to a greater degree than men (P = .62).

Conclusions

As evidenced by their higher LESS scores, females demonstrated more errors in landing technique than males, which may contribute to their increased rate of ACL injury. Both sexes displayed poor technique after the exercise protocol, which may indicate that participants experience a higher risk of ACL injury in the presence of fatigue.Key Words: anterior cruciate ligament, fatigue, Landing Error Scoring System

Key Points

• Women consistently demonstrated higher Landing Error Scoring System scores than men, committing more errors in landing technique both before and after exercise.
• The Landing Error Scoring System scores for both sexes increased after exercise, indicating that both males and females were more likely to demonstrate high-risk landing mechanics when fatigued.
• A relatively short period of intense exercise was sufficient to cause detrimental changes in landing mechanics.

An anterior cruciate ligament (ACL) tear is a common and debilitating injury in the athletic population.¹ Approximately 70% of ACL injuries during athletic activities result from a noncontact mechanism involving a deceleration task such as cutting, pivoting, or landing.² Female athletes continue to have a substantially (4 to 6 times) higher risk of noncontact ACL injury than male athletes participating in the same sports.^1,3 In addition to posing a financial burden, ACL injury has multiple long-term health consequences, including functional limitations and a markedly increased risk of disability and osteoarthritis.⁴Researchers have established multiple intrinsic and extrinsic risk factors that may contribute to an individual''s sustaining an ACL injury. It is widely believed that altered movement strategies may be most relevant to females'' increased incidence of noncontact ACL injury.^2,5 Specific movement patterns commonly observed at the time of injury include increased knee valgus and tibial rotation in combination with decreased flexion at the knee, hip, and trunk.^2,5 Laboratory studies^6,7 and video analysis of actual ACL injuries in game situations^2,5 have shown that female athletes are more likely to demonstrate these potentially detrimental landing characteristics than their male counterparts. Individuals displaying these patterns are at greater risk of knee injury.^6,8 The Landing Error Scoring System (LESS) is a clinical movement-assessment tool that can be used to identify these patterns.^9,10An additional factor that may affect injury risk is neuromuscular fatigue.¹¹ Epidemiologic findings support the concept that fatigue may be a predisposing factor for injuries during athletic events.^12,13 Overall injury rates increase during the final minutes of competition^12,13 as well as in the later portions of the season¹² when the effects of fatigue are likely to become cumulative. Specifically, Hawkins and Fuller''s data¹³ indicated that a large percentage of noncontact knee injuries occurred in the last 15 minutes of the first half and the last 30 minutes of the second half of a soccer match. Fatigue has been hypothesized to alter neuromuscular-control factors associated with an increased risk of sustaining musculoskeletal injury. The combination of fatigue with an already high-risk movement pattern may further increase the chance of injury.^11,14,15 If females respond to fatigue differently than males do, this may be an additional risk factor for ACL injuries.¹⁶ However, the specific movement patterns affected remain largely unknown because designs and results vary among studies.Few authors have examined the potential for such changes within the context of an exercise protocol that effectively simulates the demands of sport participation.^11,15 Previous researchers have used exercise protocols that have been short in duration,^11,17–19 consisted only of open kinetic chain tasks,¹⁶ or required participants to repeat a single task such as parallel squats.^14,20 Investigators evaluating longer durations of exercise have used treadmill running or sprinting^18,21 rather than the multidirectional tasks inherent to most sports.The few studies that have incorporated functional tasks have produced various results due to differences in duration and design. After 4 minutes of step-up and bounding tasks, McLean et al¹¹ found changes in only the frontal plane. Both sexes demonstrated increases in knee internal-rotation and abduction motion after exercise, and females demonstrated higher peak abduction moments than males.¹¹ Similarly, after a protocol of repeated vertical jumps and sprints until volitional exhaustion, Chappell et al¹⁵ documented in both sexes an increase in knee-valgus moment and a decrease in knee-flexion angle. Although 4 minutes appears long enough to induce some alterations in landing mechanics, additional changes in sagittal-plane movement have occurred in a study with a slightly longer duration of exercise.¹⁹ After 6 minutes of soccer drills, female National Collegiate Athletic Association Division I soccer players landed with increased knee internal-rotation and decreased knee- and hip-flexion angle. Both a longer duration and incorporation of multidirectional tasks may be necessary to truly assess changes.Whereas such protocols may certainly have placed physical demands on the participants, they do not fully replicate the loading conditions sustained by the lower extremity during athletic activity. In order to obtain the most relevant findings and apply conclusions to the athletic population, we developed a functional exercise protocol consisting of a variety of multidirectional tasks and sought to extend the duration compared with that of previous studies.^11,15,19 To make our study as clinically relevant as possible, we chose the LESS to evaluate landing technique.⁹ It is a valid and reliable clinical movement-assessment tool that allows for efficient evaluation of high-risk movement patterns.⁹By using a sportlike protocol and the clinical assessment of a landing task, our exercise tasks and assessment tool are applicable to the athletic population and feasible for use by clinicians. Considering the relationship of landing mechanics to noncontact ACL injury, studying the effects of exercise on biomechanical characteristics while in a fatigued state may provide insight into injury risk.^{11,14,15,17,20} Therefore, the purpose of this study was to assess the effects of fatigue induced by a functional exercise protocol on the landing biomechanics of males and females. We hypothesized that females would commit more landing errors than males in both the preexercise and postexercise conditions. Furthermore, we hypothesized that the exercise protocol would have a detrimental effect on all participants'' landing biomechanics, causing them to commit more errors after the protocol. Last, we hypothesized that these exercise-induced changes would be more prominent in females than in males.     

Support of evidence-based guidelines for the annual physical examination: a survey of primary care providers

BACKGROUND: Current evidence does not support an annual screening physical examination for asymptomatic adults, but little is known about primary care provider (PCP) attitudes and practices regarding an annual physical examination. METHODS: We conducted a postal survey (32 items) of attitudes and practices regarding the annual physical examination (in asymptomatic patients 18 years or older) of a random sample of PCPs (specializing in internal medicine, family practice, and obstetrics/gynecology) from 3 geographic areas (Boston, Mass; Denver, Colo; and San Diego, Calif). RESULTS: Respondents included 783 (47%) of 1679 PCPs. Overall, 430 (65%) of 664 agreed that an annual physical examination is necessary. Three hundred ninety-three (55%) of 712 disagreed with the statement that national organizations do not recommend an annual physical examination, and 641 (88%) of 726 perform such examinations. Most PCPs agreed that an annual physical examination provides time to counsel patients about preventive health services (696/739 [94%]), improves patient-physician relationships (693/737 [94%]), and is desired by most patients (572/737 [78%]). Most also believe that an annual physical examination improves detection of subclinical illness (545/738 [74%]) and is of proven value (461/736 [63%]). Many believed that tests should be part of an annual physical examination, including mammography (44%), a lipid panel (48%), urinalysis (44%), testing of blood glucose level (46%), and complete blood cell count (39%). CONCLUSIONS: Despite contrary evidence, most PCPs believe an annual physical examination detects subclinical illness, and many report performing unproven screening laboratory tests. Primary care providers do not appear to accept recommendations that annual physical examinations be abandoned in favor of a more selective approach to preventing health problems.     

An Online Needs Assessment of a Virtual Community: What Men Who Use the Internet to Seek Sex with Men Want in Internet-Based HIV Prevention

As part of a study to develop effective Internet-based HIV prevention interventions for Men who use the Internet to seek Sex with Men (MISM), we sought information from the target population on; (a) acceptability of sexually explicit media; (b) interest in specific content areas; and (c) identification of credible sources of information. A cross-sectional stratified Internet-based survey design was employed. Between September and November 2005, we recruited 2,716 MISM through Gay.com stratified across race/ethnicity to ensure adequate racial/ethnic diversity. Sixteen Likert-type items assessed acceptability of sexual explicitness, 24 items identified topics for inclusion, and two assessed sources of information. There was near universal acceptability for highly sexually explicit education. Over 75% reported high interest in 10 sexual health topics. HIV positive MISM and MISM engaged in unprotected anal sex with multiple male partners reported significantly less interest in HIV prevention specific content. Differences across age, race/ethnicity and education were identified. Idiosyncratic searches and gay sites were frequently cited sources of information; however blogs, government, and media sites were not. It is acceptable for web-based HIV prevention for MISM to be highly sexually explicit and to provide detailed content relevant to men’s sexual health. Since demographic differences in acceptability and content were minor, it is appropriate for interventions to target across demographics. Interventions to re-engage men engaging in high risk and HIV + MISM should be considered. Leading health agencies should review whether their web information is retrievable, credible and useful to those most at risk.     

Is thyroid hormone suppression therapy prothrombotic?

The purpose of this study was to determine whether chronic thyroid hormone suppression therapy (THST) is prothrombotic.We obtained blood samples from 14 thyroid cancer patients while on THST and after they had become hypothyroid for radioiodine whole-body scanning and therapy. Prothrombin fragment 1 + 2, fibrinogen, factor VIII, antithrombin, tissue plasminogen activator antigen (tPA), plasminogen activator inhibitor 1 (PAI-1), PAI-1/tPA, and C-reactive protein were significantly (P < 0.05) higher in the hyper- than in the hypothyroid state, whereas protein C and plasmin-antiplasmin complexes were significantly lower during the hyperthyroid period. When the 10 female patients were hyperthyroid, their levels of prothrombin fragment 1 + 2, fibrinogen, protein S, antithrombin, tPA, PAI-1, and PAI-1/tPA were significantly higher (P 相似文献   

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Purpose

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Methods

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Results

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Conclusions

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The psychology of fear of flying (part I): a critical evaluation of current perspectives on the nature, prevalence and etiology of fear of flying

Fear of flying, its nature, prevalence, etiology and treatment, has been the subject of a substantial quantity of research over the past 30 years. With the exception of a dated review of treatment methods however, there has been no evaluation of this expanding body of evidence, its contribution to theory and influence on clinical practice. Published research has also generally failed to apply developments in the understanding and treatment of anxiety disorders generally to fear of flying. This review provides a critical evaluation of the existing literature and what it reveals about theory and practice. It does this from the perspective of Cognitive Behavioural Therapy. The evidence reviewed demonstrates that fear of flying is a heterogeneous phenomenon which is acquired under the influence of complex psychological, social and physiological factors unique to each affected individual. Effective psychological interventions must therefore be founded on a comprehensive functional assessment of each individual, a finding which is considered in detail in the second part of this review.     

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