Weight-Bearing Dorsiflexion Range of Motion and Landing Biomechanics in Individuals With Chronic Ankle Instability

Context

People with chronic ankle instability (CAI) exhibit less weight-bearing dorsiflexion range of motion (ROM) and less knee flexion during landing than people with stable ankles. Examining the relationship between dorsiflexion ROM and landing biomechanics may identify a modifiable factor associated with altered kinematics and kinetics during landing tasks.

Objective

To examine the relationship between weight-bearing dorsiflexion ROM and single-legged landing biomechanics in persons with CAI.

Design

Cross-sectional study.

Setting

Laboratory.

Patients or Other Participants

Fifteen physically active persons with CAI (5 men, 10 women; age = 21.9 ± 2.1 years, height = 168.7 ± 9.0 cm, mass = 69.4 ± 13.3 kg) participated.

Intervention(s)

Participants performed dorsiflexion ROM and single-legged landings from a 40-cm height. Sagittal-plane kinematics of the lower extremity and ground reaction forces (GRFs) were captured during landing.

Main Outcome Measure(s)

Static dorsiflexion was measured using the weight-bearing–lunge test. Kinematics of the ankle, knee, and hip were observed at initial contact, maximum angle, and sagittal displacement. Sagittal displacements of the ankle, knee, and hip were summed to examine overall sagittal displacement. Kinetic variables were maximum posterior and vertical GRFs normalized to body weight. We used Pearson product moment correlations to evaluate the relationships between dorsiflexion ROM and landing biomechanics. Correlations (r) were interpreted as weak (0.00–0.40), moderate (0.41–0.69), or strong (0.70–1.00). The coefficient of determination (r²) was used to determine the amount of explained variance among variables.

Results

Static dorsiflexion ROM was moderately correlated with maximum dorsiflexion (r = 0.49, r² = 0.24), ankle displacement (r = 0.47, r² = 0.22), and total displacement (r = 0.67, r² = 0.45) during landing. Dorsiflexion ROM measured statically and during landing demonstrated moderate to strong correlations with maximum knee (r = 0.69–0.74, r² = 0.47–0.55) and hip (r = 0.50–0.64, r² = 0.25–0.40) flexion, hip (r = 0.53–0.55, r² = 0.28–0.30) and knee (r = 0.53–0.70, r² = 0.28–0.49) displacement, and vertical GRF (−0.47– −0.50, r² = 0.22–0.25).

Conclusions

Dorsiflexion ROM was moderately to strongly related to sagittal-plane kinematics and maximum vertical GRF during single-legged landing in persons with CAI. Persons with less dorsiflexion ROM demonstrated a more erect landing posture and greater GRF.Key Words: ankle sprain, drop landing, neuromuscular control, kinematics, kinetics

Key Points

• During a single-legged landing, persons with chronic ankle instability demonstrated moderate to strong relationships between dorsiflexion range of motion (ROM) and sagittal-plane kinematics at the knee and hip and vertical ground reaction forces.
• Persons with less dorsiflexion ROM exhibited a less flexed landing strategy that attenuated ground reaction forces less efficiently.
• Identifying dorsiflexion deficits may enable clinicians to implement interventions to increase ROM and potentially modify the landing biomechanics that persons with chronic ankle instability exhibit.

Ankle sprains are one of the most common injuries associated with athletics.¹ In addition, up to 73% of athletes who sustain ankle sprains experience recurrent ankle sprains, and 59% report functional loss and residual symptoms that have affected athletic performance.² Residual symptoms resulting from ankle sprains are often associated with a condition known as chronic ankle instability (CAI). This condition is characterized by repetitive ankle-sprain injuries, frequent episodes of the ankle “giving way,” and decreased self-reported function stemming from an acute ankle sprain.³ Persons with CAI have reported diminished health-related quality of life and are at greater risk for developing posttraumatic ankle osteoarthritis.^4,5 Based on the number of persons who develop CAI and the long-term consequences of the condition, a better understanding of the contributing factors is warranted to improve clinical intervention strategies.Chronic ankle instability may be associated with several mechanical impairments in ankle function,³ including a deficit in ankle-joint dorsiflexion range of motion (ROM).^3,6 Whereas the exact prevalence of dorsiflexion ROM deficits has not been determined, 30% to 74% of persons with CAI have at least a 5° deficit in weight-bearing dorsiflexion ROM compared with the contralateral limb.^7,8 The exact origin of dorsiflexion ROM deficits is unclear, but it likely results from arthrokinematic alterations and adaptive shortening of the triceps surae muscle group.^9,10 More importantly, dorsiflexion deficits may limit the ability to fully achieve a closed-packed, stable position of the ankle during dynamic activities, such as gait and landing, which may promote the pathomechanics associated with ankle-sprain mechanisms.^9,11,12 Therefore, a cascade of structural impairments leading to decreased dorsiflexion ROM may affect the ability to execute functional activities and ultimately contribute to the repeated ankle sprains and episodes of giving way related to CAI.Dorsiflexion ROM plays a prominent role in the biomechanics of tasks that require landing.¹³ Greater passive open chain dorsiflexion ROM has been associated with greater hip and knee flexion and lower ground reaction forces (GRFs) during a jump-landing task in healthy persons.¹³ Those with greater dorsiflexion ROM land with a less erect posture by using greater sagittal-plane displacement, which allows the body to attenuate forces more efficiently.¹³ Therefore, the available amount of dorsiflexion ROM may influence function not only at the ankle but also at more proximal structures in the lower extremity. Persons with CAI have demonstrated less dorsiflexion ROM during gait^11,14 and less knee flexion during landing than persons without CAI, but these findings have not been consistent in the literature.^15,16 Furthermore, persons with CAI have shown greater energy dissipation at the ankle and less energy dissipation at the knee.¹⁷ Cumulatively, these observations suggest that alterations exist in the distal to proximal linkage of the kinetic chain of the lower extremity in persons with CAI.¹⁷ Further examining a potential connection between dorsiflexion ROM and landing biomechanics may provide additional insight into these findings.Persons who have CAI and less dorsiflexion ROM may also exhibit more erect landing postures and greater GRF, which may have implications for sustaining future lower extremity injuries or episodes of giving way.^18,19 Examining this relationship may further support integrating clinical intervention strategies that target dorsiflexion ROM into the rehabilitation of persons with CAI.⁹ Therefore, the purpose of our study was to examine the relationship between dorsiflexion ROM and single-legged landing biomechanics in persons with CAI. We examined dorsiflexion ROM statically, using the weight-bearing–lunge test, and dynamically, using motion capture, to determine its relationship to landing biomechanics. In addition, we focused on the sagittal-plane kinematics of the lower extremity and GRFs to explore how dorsiflexion ROM may influence force attenuation in persons with CAI. Kinematics were examined in the sagittal plane because it is primarily responsible for force attenuation during landing tasks.²⁰ We hypothesized that persons with less dorsiflexion ROM would exhibit less sagittal-plane motion throughout the lower extremity and greater GRF during a single-legged drop-landing task.     

Potential challenges facing distributed leadership in health care: evidence from the UK National Health Service

The discourse of leaderism in health care has been a subject of much academic and practical debate. Recently, distributed leadership (DL) has been adopted as a key strand of policy in the UK National Health Service (NHS). However, there is some confusion over the meaning of DL and uncertainty over its application to clinical and non‐clinical staff. This article examines the potential for DL in the NHS by drawing on qualitative data from three co‐located health‐care organisations that embraced DL as part of their organisational strategy. Recent theorising positions DL as a hybrid model combining focused and dispersed leadership; however, our data raise important challenges for policymakers and senior managers who are implementing such a leadership policy. We show that there are three distinct forms of disconnect and that these pose a significant problem for DL. However, we argue that instead of these disconnects posing a significant problem for the discourse of leaderism, they enable a fantasy of leadership that draws on and supports the discourse.     

Continuous inhibition of 11β‐hydroxysteroid dehydrogenase type I in adipose tissue leads to tachyphylaxis in humans and rats but not in mice

Background and Purpose

11β‐hydroxysteroid dehydrogenase type I (11β‐HSD1), a target for Type 2 diabetes mellitus, converts inactive glucocorticoids into bioactive forms, increasing tissue concentrations. We have compared the pharmacokinetic‐pharmacodynamic (PK/PD) relationship of target inhibition after acute and repeat administration of inhibitors of 11β‐HSD1 activity in human, rat and mouse adipose tissue (AT).

Experimental Approach

Studies included abdominally obese human volunteers, rats and mice. Two specific 11β‐HSD1 inhibitors (AZD8329 and COMPOUND‐20) were administered as single oral doses or repeat daily doses for 7–9 days. 11β‐HSD1 activity in AT was measured ex vivo by conversion of ³H‐cortisone to ³H‐cortisol.

Key Results

In human and rat AT, inhibition of 11β‐HSD1 activity was lost after repeat dosing of AZD8329, compared with acute administration. Similarly, in rat AT, there was loss of inhibition of 11β‐HSD1 activity after repeat dosing with COMPOUND‐20 with continuous drug cover, but effects were substantially reduced if a ‘drug holiday’ period was maintained daily. Inhibition of 11β‐HSD1 activity was not lost in mouse AT after continuous cover with COMPOUND‐20 for 7 days.

Conclusions and Implications

Human and rat AT, but not mouse AT, exhibited tachyphylaxis for inhibition of 11β‐HSD1 activity after repeat dosing. Translation of observed efficacy in murine disease models to human for 11β‐HSD1 inhibitors may be misleading. Investigators of the effects of 11β‐HSD1 inhibitors should confirm that desired levels of enzyme inhibition in AT can be maintained over time after repeat dosing and not rely on results following a single dose.

Abbreviations

11β‐HSD1

11β‐hydroxysteroid dehydrogenase type I

PK/PD

pharmacokinetic‐pharmacodynamic

AT

adipose tissue

DIO

diet induced obese

IHC

International Conference on Harmonisation

GCP

Good Clinical Practice

b.i.d.

twice daily

u.i.d.

once daily

HPMC

hydroxypropylmethylcellulose

IC₇₀

concentration that delivers 70% of the maximum effect

IC₉₀

concentration that delivers 90% of the maximum effect

fu

fraction unbound

C_max

maximum achieved concentration

C_min

minimum or trough concentration

E₀

baseline

E_max

maximum effect

ANCOVA

analysis of covariance

     

Predictors of Energy Compensation during Exercise Interventions: A Systematic Review

Weight loss from exercise-induced energy deficits is usually less than expected. The objective of this systematic review was to investigate predictors of energy compensation, which is defined as body energy changes (fat mass and fat-free mass) over the total amount of exercise energy expenditure. A search was conducted in multiple databases without date limits. Of 4745 studies found, 61 were included in this systematic review with a total of 928 subjects. The overall mean energy compensation was 18% ± 93%. The analyses indicated that 48% of the variance of energy compensation is explained by the interaction between initial fat mass, age and duration of exercise interventions. Sex, frequency, intensity and dose of exercise energy expenditure were not significant predictors of energy compensation. The fitted model suggested that for a shorter study duration, lower energy compensation was observed in younger individuals with higher initial fat mass (FM). In contrast, higher energy compensation was noted for younger individuals with lower initial FM. From 25 weeks onward, energy compensation was no longer different for these predictors. For studies of longer duration (about 80 weeks), the energy compensation approached 84%. Lower energy compensation occurs with short-term exercise, and a much higher level of energy compensation accompanies long-term exercise interventions.     

Modifiable Failures in the Colorectal Cancer Screening Process and Their Association With Risk of Death

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Physical therapy and mobility 2 and 6 months after hip fracture

OBJECTIVES: To examine the relationship between early physical therapy (PT), later therapy, and mobility 2 and 6 months after hip fracture. DESIGN: Prospective, multisite observational study. SETTING: Four hospitals in the New York City area. PARTICIPANTS: Four hundred forty-three hospitalized older patients discharged after surgery for hip fracture in 1997-98. MEASUREMENTS: Patient demographics, fracture type, comorbidities, dementia, number of new impairments at discharge, amount of PT between day of surgery and postoperative day (POD) 3, amount of therapy between POD4 and 8 weeks later, and prefracture, 2-, and 6-month mobility measured using the Functional Independence Measure. RESULTS: More PT immediately after hip fracture surgery was associated with significantly better locomotion 2 months later. Each additional session from the day of surgery through POD3 was associated with an increase of 0.4 points (P=.032) on the 14-point locomotion scale, but the positive relationship between early PT and mobility was attenuated by 6 months postfracture. There was no association between later therapy and 2- or 6-month mobility. CONCLUSION: PT immediately after hip fracture surgery is beneficial. The effects of later therapy on mobility were difficult to assess because of limitations of the data. Well-designed randomized, controlled trials of the effect of varying schedules and amounts of therapy on functional status after hip fracture would be informative.     

Patient protection and risk selection

BACKGROUND: Individual physicians who are paid prospectively, as in capitated health plans, might tend to encourage patients to avoid or to join these plans according to the patient's health status. Though insurance risk selection has been well documented among organizations paid on a prospective basis, such physician-level risk selection has not been studied. OBJECTIVE: To assess physician reports of risk selection in capitated health plans and explore potentially related factors. DESIGN AND PARTICIPANTS: National mailed survey of primary care physicians in 1997-1998, oversampling physicians in areas with more capitated health plans. RESULTS: The response rate was 63% (787 of 1,252 eligible recipients). Overall, 44% of physicians reported encouraging patients either to join or to avoid capitated health plans according to the patients' health status: 40% encouraged more complex and ill patients to avoid capitated plans and 23% encouraged healthier patients to join capitated plans. In multivariable models, physicians with negative perceptions of capitated plan quality, with more negative experiences in capitated plans, and those who knew at each patient encounter how they were being compensated had higher odds of encouraging sicker patients to avoid capitated plans (odds ratios, 2.0, 2.2, and 2.0; all confidence intervals >1). CONCLUSIONS: Many primary care physicians report encouraging patients to join or avoid capitated plans according to the patient's health status. Although these physicians' recommendations might be associated primarily with concerns about quality, they can have the effect of insulating certain health plans from covering sicker and more expensive patients.