Well‐Defined Imidazolium ABA Triblock Copolymers as Ionic‐Liquid‐Containing Electroactive Membranes

Nitroxide‐mediated polymerization (NMP) affords the synthesis of well‐defined ABA triblock copolymers with polystyrene external blocks and a charged poly(1‐methyl‐3‐(4‐vinylbenzyl)­imidazolium bis(trifluoromethane sulfonyl)imide central block. Aqueous size‐exclusion chromatography (SEC) and ¹H NMR spectroscopy studies confirm the control of the composition and block lengths for both the central and external blocks. Dynamic mechanical analysis (DMA) reveals a room temperature modulus suitable for fabricating these triblock copolymers into electroactive devices in the presence of an added ionic liquid. Dielectric relaxation spectroscopy (DRS) elucidates the ion‐transport properties of the ABA triblock copolymers with varied compositions. The ionic conductivity in these single‐ion conductors exhibits Vogel–Fulcher–Tammann (VFT) and Arrhenius temperature dependences, and electrode polarization (EP) analysis determines the number density of simultaneously conducting ions and their mobility. The actuators derived from these triblock copolymer membranes experience similar actuation speeds at an applied voltage of 4 V DC, as compared with benchmark Nafion membranes. These tailorable ABA block copolymers are promising candidates for ionic‐polymer device applications.

     

Classification of Lower Extremity Movement Patterns Based on Visual Assessment: Reliability and Correlation With 2-Dimensional Video Analysis

Context:

Abnormal movement patterns have been implicated in lower extremity injury. Reliable, valid, and easily implemented assessment methods are needed to examine existing musculoskeletal disorders and investigate predictive factors for lower extremity injury.

Objective:

To determine the reliability of experienced and novice testers in making visual assessments of lower extremity movement patterns and to characterize the construct validity of the visual assessments.

Design:

Cross-sectional study.

Setting:

University athletic department and research laboratory.

Patients or Other Participants:

Convenience sample of 30 undergraduate and graduate students who regularly participate in athletics (age = 19.3 ± 4.5 years). Testers were 2 experienced physical therapists and 1 novice postdoctoral fellow (nonclinician).

Main Outcome Measure(s):

We took videos of 30 athletes performing the single-legged squat. Three testers observed the videos on 2 occasions and classified the lower extremity movement as dynamic valgus, no change, or dynamic varus. The classification was based on the estimated change in frontal-plane projection angle (FPPA) of the knee from single-legged stance to maximum single-legged squat depth. The actual FPPA change was measured quantitatively. We used percentage agreement and weighted κ to examine tester reliability and to determine construct validity of the visual assessment.

Results:

The κ values for intratester and intertester reliability ranged from 0.75 to 0.90, indicating substantial to excellent reliability. Percentage agreement between the visual assessment and the quantitative FPPA change category was 90%, with a κ value of 0.85.

Conclusions:

Visual assessments were made reliably by experienced and novice testers. Additionally, movement-pattern categories based on visual assessments were in excellent agreement with objective methods to measure FPPA change. Therefore, visual assessments can be used in the clinic to assess movement patterns associated with musculoskeletal disorders and in large epidemiologic studies to assess the association between lower extremity movement patterns and musculoskeletal injury.Key Words: movement analysis, screening, athletic injuries, knee valgus

Key Points

• With training and the use of standardized techniques, both experienced and novice testers reliably classified lower extremity movement patterns based on visual assessment.
• Movement-pattern category-based visual assessments were in excellent agreement with objective methods to measure changes in frontal-plane projection angle.
• Visual assessment based on the methods described in this study may be used in the clinical setting, as well as in large epidemiologic studies and screening assessments for sport participation, to identify distinct categories of lower extremity movement patterns.

Abnormal movement patterns of the lower extremity have been implicated in noncontact anterior cruciate ligament (ACL) injuries¹ and other musculoskeletal problems, such as patellofemoral pain^2–4 and acetabular labral tears.⁵ In addition, correcting these abnormal movement patterns has been shown to prevent ACL injury⁶ and is proposed to reduce symptoms in people with preexisting pain conditions.^5,7,8 Thus, assessment of lower extremity movement patterns may be a way to guide treatment of existing musculoskeletal pain problems and to identify people at risk for future injury or musculoskeletal pain. To facilitate the examination of existing musculoskeletal disorders and the investigation of predictive factors of lower extremity injury, reliable, valid, and feasible methods to assess lower extremity movement patterns are needed.One method to assess lower extremity movement patterns is the Landing Error Scoring System (LESS).^9–11 The LESS uses a standard technique to make visual assessments of movement patterns during a drop vertical jump. The LESS is reliable and valid^9–11; however, the drop vertical jump is a relatively high-level activity and may not be the best way to assess movement patterns in patients with existing injury or in athletes whose sports do not involve landing from a jump. In addition, the drop vertical jump is a bilateral activity that may allow the participant to use 1 limb to compensate for the other. Visual assessment of the single-legged squat (SLSquat), a unilateral limb task, may provide an alternative to the LESS.We have developed standardized methods using a visual assessment of the frontal-plane projection angle (FPPA) to classify the lower extremity movement pattern during an SLSquat. The FPPA is a 2-dimensional (2-D) representation of the lower extremity position¹² and has been used to identify differences between men and women¹² and between women with patellofemoral pain and control participants^4,13 and to detect change in movement patterns after specific training.¹⁴ We established specific criteria to define the categories of lower extremity movement pattern based on the change in FPPA (FPPA change) during motion. The tester observes the angle formed between a line that bisects the thigh and a line that bisects the lower leg. During movement tests, the tester compares the FPPA at the start position with the FPPA at the end position. For example, to assess an SLSquat, the examiner compares the FPPA during the start position of single-legged stance with the end position of maximum squat depth. The difference observed in FPPA from the start to the end position can then be classified as dynamic valgus (change in the valgus direction), no change, or dynamic varus (change in the varus direction). We have used this assessment extensively in the clinical setting, but we have not assessed the rater reliability or the construct validity of our visual assessments.The purpose of this study was to assess the intratester and intertester reliability of 3 testers (2 experienced, 1 novice) categorizing the lower extremity movement pattern demonstrated during an SLSquat. A standardized protocol was used to assess videos of healthy participants performing the SLSquat. We hypothesized that the testers, both experienced and novice, would demonstrate good to excellent reliability using the standardized methods. In addition, we used the objective measure of quantifying FPPA as described by Willson and Davis¹² to determine the construct validity of our visual assessments. We hypothesized that we would see good to excellent agreement between our visual assessments and the quantitative FPPA change.     

Effects of resveratrol in experimental and clinical non-alcoholic fatty liver disease

The prevalence of obesity and related conditions like non-alcoholic fatty liver disease(NAFLD) is increasing worldwide and therapeutic options are limited.Alternative treatment options are therefore intensively sought after.An interesting candidate is the natural polyphenol resveratrol(RSV) that activates adenosinmonophosphate-activated protein kinase(AMPK) and silent information regulation-2 homolog 1(SIRT1).In addition,RSV has known anti-oxidant and anti-inflammatory effects.Here,we review the current evidence for RSVmediated effects on NAFLD and address the different aspects of NAFLD and non-alcoholic steatohepatitis(NASH) pathogenesis with respect to free fatty acid(FFA) flux from adipose tissue,hepatic de novo lipogenesis,inadequate FFA β-oxidation and additional intra- and extrahepatic inflammatory and oxidant hits.We review the in vivo evidence from animal studies and clinical trials.The abundance of animal studies reports a decrease in hepatic triglyceride accumulation,liver weight and a general improvement in histological fatty liver changes,along with a reduction in circulating insulin,glucose and lipid levels.Some studies document AMPK or SIRT1 activation,and modulation of relevant markers of hepatic lipogenesis,inflammation and oxidation status.However,AMPK/SIRT1-independent actions are also likely.Clinical trials are scarce and have primarily been performed with a focus on overweight/obese participants without a focus on NAFLD/NASH and histological liver changes.Future clinical studies with appropriate design are needed to clarify the true impact of RSV treatment in NAFLD/NASH patients.