The influence of lower-limb prostheses technology on Paracanoeing time-trial performance

Within the Paracanoeing discipline, it is important to ensure that appropriate control is achieved by a paddler with a disability. However, this Paralympic Games discipline has seen very little attention to date. The aims of this study were to understand the kinematic impact to a paracanoeist when not utilizing the use of a prosthetic lower-limb. A kayaker with a uni-lateral transfemoral amputation completed several 200?m maximal efforts both with and without their prosthesis. When the prosthetic limb was removed, there were significant differences found in stroke rate, stroke speed, stroke length and overall power output. Sagittal and frontal video analysis demonstrated the residual limb movements when paddling and indicated where support would be required to improve the kayak’s control. It is recommended that those with lower-limb absence wishing to paddle a kayak competitively utilize the use of a prostheses designed for the kayaking environment that supports the residual limb at both the upper and inner thigh and the distal end.

• Implications for rehabilitation

• This paper is the first study to investigate both biomechanical and assistive technology-related issues in the new Paralympic Games sport of Paracanoeing.

• For participants possessing lower-limb absence, a prosthetic limb that is designed specifically for the kayaking environment is recommended when Paracanoeing to maximize efficient propulsion.

• Use of an ergometer and multiple 2D cameras provides practitioners the ability to optimize both the comfort and fit of a prosthetic limb.

• Use of an ergometer and multiple 2D cameras provides both athletes and practitioners the ability to optimize the points of human contact within a kayak to ensure comfort and control.

     

Validation of the virtual elevation field test method when assessing the aerodynamics of para-cyclists with a uni-lateral trans-tibial amputation

Lower-limb amputees typically require some form of prosthetic limb to ride a bicycle for recreation or when competing. At elite-level racing speeds, aerodynamic drag can represent the majority of the resistance acting against a cyclists’ forward motion. As a result, the reduction of such resistance is beneficial to an amputee whereby the form and function of the prosthetic limb can be optimized through engineering. To measure the performance of such limbs, field testing provides a cost-effective and context-specific method of aerodynamic drag measurement. However, few methods have been formally validated and none have been applied to amputees with lower-limb amputations. In this paper, an elite level para-cyclist wore two different prosthetic limb designs and had their total aerodynamic drag of a wind tunnel reference method statistically correlated against a velodrome-based virtual elevation field test method. The calculated coefficient of variation was in the range of 0.7–0.9% for the wind tunnel method and 2–3% for the virtual elevation method. A 0.03?m² difference was identified in the absolute values recorded between the two methods. Ultimately, both methods exhibited high levels of precision, yet relative results to each other. The virtual elevation method is proposed as a suitable technique to assess the aerodynamic drag of amputee para-cyclists.

• Implications for rehabilitation

• This assessment method will provide practitioners a reliable means of assessing the impact of changes made to prosthetics design for cyclists with limb absence.

• The proposed method offers a low cost and geographically accessible solution compared to others proposed in the past.

• This assessment method has significant potential for impact among prosthetic limb users looking to improve their cycling performance whereas previous attention in this field has been extremely limited.

     

Skin involvement in juvenile dermatomyositis is associated with loss of end row nailfold capillary loops

OBJECTIVE: To determine associations of dermatological findings in children with juvenile dermatomyositis (JDM) with specific nailfold capillary (NFC) structural abnormalities. METHODS: Sixty newly diagnosed, previously untreated children who met the Bohan-Peter criteria for definite JDM were seen between 1993 and 2002. They were classified by duration of untreated disease and by a disease activity score (DAS) composed of separate subscores for dermatological (DAS skin) and musculoskeletal (DAS muscle) findings. Routine NFC measurements yielded the number of end row loops, arboreal (bushy), and dilated capillary loops. Laboratory testing included muscle enzymes, von Willebrand Factor Antigen, and neopterin. RESULTS: DAS skin, but not DAS muscle, was associated with NFC end row capillary loss (rs = -0.394, p = 0.008). End row capillary loss (reflecting avascularity), arboreal (bushy), and dilated capillary loops (reflecting change in vascular morphology) were each associated with longer untreated symptom duration (rs = -0.401, rs = 0.534, rs = 0.371). CONCLUSION: End row capillary loss measured by NFC was associated with the dermatological, but not musculoskeletal manifestations of JDM, suggesting that damage to skin and muscle may each have distinct disease pathophysiology. In JDM, skin involvement indicates a vasculopathy that progresses with increasing duration of untreated disease and is not revealed by standard serological laboratory tests. We propose that the cutaneous manifestations of JDM are associated with vascular disease and warrant aggressive therapy.     

Effect on luteinizing hormone secretion of GABA receptor modulation in the medial preoptic area at the time of proestrous luteinizing hormone surge.

Using a bilateral medial preoptic area (MPOA) infusion system in conscious female rats we have investigated the role of the GABA system in this area on the proestrous luteinizing hormone (LH) surge. Fifteen-minute blood samples for LH estimation were taken throughout the afternoon of proestrus from female rats exhibiting 4-day oestrous cycles and implanted at least 2 weeks prior with cerebral guide cannulae. Between 15:00 and 17:00 h rats received an infusion (1 microliter/30 min) of artificial cerebrospinal fluid (n = 7), 10 microM GABA (n = 6) or 10 microM bicuculline methiodide (BMI, n = 6). Animals infused with GABA failed to exhibit an LH surge, while BMI-treated animals displayed an LH surge which was not significantly different to controls. These data show that on the afternoon of proestrus, there are no tonic modulatory actions of the GABA system, acting through the GABAA receptor, on neural elements controlling the LH surge in the MPOA. If, however, GABA levels are elevated in the MPOA at this time then the LH surge is blocked. In conjunction with data from correlative studies showing a decrease in endogenous GABA release prior to the LH surge, we suggest that this fall in activity is an essential component of the LH surge mechanism.     

Preparation and properties of brush-border membrane vesicles from human small intestine

This study describes a simple and rapid method for the preparation of brush-border membrane vesicles from intestinal biopsies. The specific activities of sucrase, amino peptidase N, and alkaline phosphatase in these vesicles were the same as those in vesicles prepared from intestinal segments. The vesicles from all the regions of the small intestine can transport D-glucose in an Na+-dependent manner. The rates of transport of D-glucose presented here are far higher than previously reported. The method should have a wide applicability to studies of transport mechanisms and the distribution of transport processes within the intestine.     

Noninvasive Methods for Determining Pulmonary Vascular Function in Children with Pulmonary Arterial Hypertension: Application of a Mechanical Oscillator Model

Objective. Noninvasive diagnostics for pulmonary arterial hypertension (PAH) have traditionally sought to predict main pulmonary artery pressure from qualitative or direct quantitative measures of the flow velocity pattern obtained from spectral Doppler ultrasound examination of the main pulmonary artery. A more detailed quantification of flow velocity patterns in the systemic circuit has been obtained by parameterizing the flow trace with a simple dynamic system model. Here, we investigate such a model's utility as a noninvasive predictor of total right heart afterload and right heart function. Design. Flow velocity and pressure was measured within the main pulmonary artery during right heart catheterization of patients with normal hemodynamics (19 subjects, 20 conditions) and those with PAH undergoing reactivity evaluation (34 patients, 69 conditions). Our model parameters were obtained by least‐squares fitting the model velocity to the measured flow velocity. Results. Five parameter means displayed significant (P < .05) differences between normotensive and hypertensive groups. The model stiffness parameter correlated to actual pulmonary vascular resistance (r = 0.4924), pulmonary vascular stiffness (r = 0.6811), pulmonary flow (r = 0.6963), and stroke work (r = 0.7017), while the model initial displacement parameter had good correlation to stiffness (r = 0.6943) and flow (r = 0.6958). Conclusions. As predictors of total right heart afterload (resistance and stiffness) and right ventricle work, the model parameters of stiffness and initial displacement offer more comprehensive measures of the disease state than previous noninvasive methods and may be useful in routine diagnostic monitoring of patients with PAH.     

Trophic cascades in a complex terrestrial community

To test for direct and indirect effects of a top predator on three lower trophic levels, we conducted two multiyear predator addition experiments in a tropical wet forest. Periodic additions of a top predator (predatory clerid beetle) to a wet forest understory shrub caused a reduction in the predatory beetle's prey (a predatory ant), increased herbivory, and reduced leaf area of the plant. These effects occurred whether beetles were added to naturally occurring shrubs or to reproductive fragments, suggesting fitness effects of top predators through three trophic levels. A correlational study showed that trophic effects of top predators also cascaded to nearby conspecifics in the forest understory. We use trends from understory plant surveys to suggest mechanisms by which these cascades could ultimately affect species diversity in the local plant community.