BIOMECHANICS OF WHEELCHAIR RACING

An additional assistive device - such as a wheelchair or a prosthesis often forms an integral part of the disabled athlete and a functional prerequisite for mobility and sports participation. The use of such a tool in high performance sports situations sets typical demands to the performance capacity of the athlete. but also to the methods end techniques of biomechanical research. Apart from environmental f a e m research into the optimization of performance in wheelchair racing will have to focus on three areas of interest Firstly, the dynamics and design of wheelchairs should conform to the laws of (vehicle) mechanics. Rolling resistance, air drag and internal friction must be minimized, since these forces determine the e x m a 1 power output which the human engine will have to deliver at a certain speed. 'Lightweight' and 'high tech' an the keywords of contemporary racing wheelchairs. Their design is task-directed and - within this framework - tuned to the individual demands of the athlete. Secondly. work capacity and propulsion technique an major determinants in the performance of the human engine. Performance is primarily dependent upon the functional and training status of the upper body of the athlete. Understanding the detailed functional role of the upper body in wheelchair track performance requires a combined biomechanical and physiological study of arm work under realistic experimental conditions and in different groups of subjects. Thirdly, performance of the wheelchair-user combination is influenced by the interfacing between the wheelchair and the athlete. Development of fitting criteria with respect to geometry and mechanics of the wheelchair requires a combined biomechanical and physiological approach too. Wheelchair propulsion is frequently studied on a motor driven treadmill. 'Three-dimensional kinematics and electromyography arc combined in conjunction with overall physiology and prove to lead to a valuable description of same biomechanical aspects of wheeled mobility. To enable a more detailed biodynamic analysis of wheelchair propulsion a computer-controlled wheelchair ergo meter was designed. Through simulation of wheelchair propulsion force characteristics in all interfacing units of the wheelchair-user combination an studied: the seat. backrest and the rims. Thus torque production. efficacy of force generation and the net torque and power production over the different joints are studied under (sub-)maximal performance conditions and in conjunction with different aspects of the wheelchair-user interface. Within this framework special attention is dedicated to the functional anatomy and biomechanics of the shoulder mechanism, which is crucial in power production. Modelling of the shoulder mechanism - based on detailed dissection studies - will help clarify its role in propulsion technique and will help specify wheelchair fitting guidelines. This integrated anatomical. biomechanical and physiological approach may eventually help explain the human potential and limitations in arm work and the mechanisms which lead to overuse injuries in the arm-shoulder complex

Lipid, lipoprotein and apolipoprotein profiles in active and sedentary men with tetraplegia

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The effects of upper body exercise on the physical capacity of people with a spinal cord injury: a systematic review

OBJECTIVE: To describe the effects of upper body training on the physical capacity of people with a spinal cord injury. DATA SOURCES: The databases of PubMed, CINAHL, Sport Discus and Cochrane were searched from 1970 to May 2006. REVIEW METHODS: The keywords 'spinal cord injury', 'paraplegia', 'tetraplegia' and 'quadriplegia' were used in combination with 'training'. The methodological quality of the included articles (both randomized controlled trials and controlled clinical trials) was assessed with the modified 'van Tulder et al.' checklist. Studies were described with respect to population, test design, training protocol and mode of training. The training effects on physical capacity, reflected by peak power output (PO(peak)) and oxygen uptake (VO(2peak)), were summarized. RESULTS: Twenty-five studies were included with a mean score of 8.8 out of 17 items on the quality checklist. The methodological quality was quite low, mostly because of the absence of randomized controlled trials. Therefore no meta-analysis was possible. In the 14 articles of acceptable quality the mean (SD) increase in VO( 2peak) and PO(peak,) following a period of training, was 17.6 (11.2)% and 26.1 (15.6)%, respectively. CONCLUSIONS: Due to the overall low quality of studies it is not possible to draw definitive conclusions on training effects for different lesion groups or training modes. The results of the relatively few studies with an acceptable quality seem to support the view that upper body exercise may increase the physical capacity of people with spinal cord injury. The magnitude of improvement in PO( peak) and VO(2peak), however, varies considerably among studie

Saving money on the PBS: Ranibizumab or Bevacizumab for Neovascular Macular Degeneration?

Federal Health Minister Nicola Roxon recently met with an alliance of consumer, industry and other stakeholders to justify the government’s plan to indefinitely delay the listing of seven new medicines on the Pharmaceutical Benefits Scheme (PBS). She argued that, after considering the advice of the Pharmaceutical Benefits Advisory Committee (PBAC), it was the government’s responsibility to decide whether or not to list a new drug, taking into account other priorities across the health portfolio and current fiscal circumstances. 1 Clearly, the cost of the PBS must be sustainable. However, there are other ways of reducing its cost apart from delaying the listing of drugs recommended by PBAC as cost-effective. The treatment of macular degeneration provides an illustrative example

Comparison of muscle strength, sprint power and aerobic capacity in adults with and without cerebral palsy

Objective: To compare: (i) muscle strength, sprint power and maximal aerobic capacity; and (ii) the correlations between these variables in adults with and without cerebral palsy. Design: Cross-sectional study. Subjects: Twenty adults with and 24 without cerebral palsy. Methods: Isometric and isokinetic knee extension strength, sprint power (mean power over the 30s (P30)), peak aerobic power output (POpeak) and oxygen uptake (VO2peak) were determined. Regression analysis was used to investigate correlations between parameters. Results: Adults with cerebral palsy had significantly lower strength (53-69%) and P30 (67%) than adults without cerebral palsy, but similar POpeak and VO2peak. In adults without cerebral palsy the only significant correlations, albeit weak, were between P30 and isometric (R-2=0.34) or isokinetic strength (R-2=0.20), as well as the correlation between P30 and VOpeak (R-2=0.26) or POpeak (R-2=0.36). Stronger correlations were found in the group with cerebral palsy between P30 and isometric (R-2=0.52) and isokinetic strength (R-2=0.71) and between P30 and VOpeak (R-2=0.75) or POpeak (R-2=0.94). Conclusion: In contrast to aerobic capacity, strength and P30 are reduced in (active) people with cerebral palsy. Stronger correlations were found between strength, P30 and POpeak in adults with cerebral palsy. Therefore, muscle strength may be the limiting factor in adults with cerebral palsy for activities involving the lower extremities, such as cycling

Complications following spinal cord injury: occurrence and risk factors in a longitudinal study during and after inpatient rehabilitation

Objective: To assess the occurrence and risk factors for complications following spinal cord injury during and after inpatient rehabilitation. Design: Multicentre longitudinal study. Subjects: A total of 212 persons with a spinal cord injury admitted to specialized rehabilitation centres. Methods: Assessments at the start of active rehabilitation (n = 212), 3 months later (n = 143), at discharge (n = 191) and 1 year after discharge (n = 143). Results: Multi-level random coefficient analyses revealed that complications were common following spinal cord injury. Most subjects reported neurogenic and musculoskeletal pain, or had spasticity at each assessment. During the year after discharge, complications remained common: urinary tract infections and pressure sores affected 49% and 36% of the population, respectively. The degree of pain decreased, whereas the degree of spasticity increased significantly during inpatient rehabilitation. Overall, increased age, increased body mass index, traumatic lesion, tetraplegia, and complete lesion all increased the risk of complications. Conclusion: Complications are common following spinal cord injury. They need specific attention after discharge from inpatient rehabilitation and within subpopulations. © 2007 Foundation of Rehabilitation Information

The Wheelchair Circuit: Construct Validity and Responsiveness of a Test to Assess Manual Wheelchair Mobility in Persons With Spinal Cord Injury

Kilkens OJ, Dallmeijer AJ, de Witte LP, van der Woude LH, Post MW. The Wheelchair Circuit: construct validity and responsiveness of a test to assess manual wheelchair mobility in persons with spinal cord injury. Arch Phys Med Rehabil 2004;85:424-31. Objective To assess the validity and responsiveness of the Wheelchair Circuit, a test to assess manual wheelchair mobility in persons with spinal cord injury (SCI). Design Longitudinal. Subjects performed the Wheelchair Circuit at the start (T1) and at the end (T3) of inpatient functional rehabilitation. Construct validity and responsiveness were assessed. Setting Eight rehabilitation centers in the Netherlands. Participants Seventy-four subjects with SCI admitted for inpatient rehabilitation. Interventions Not applicable. Main outcome measures The Wheelchair Circuit consists of 8 wheelchair skills and results in 3 test scores: ability, performance time, and physical strain. The construct validity of the Wheelchair Circuit was assessed by testing whether the test scores were significantly related to the subjects' functional status, physical capacity, lesion level, motor completeness of the lesion, and age. To prove the test's responsiveness, it was assessed whether the test scores had significantly improved between T1 and T3. Results For construct validity, 4 of the 5 hypotheses were confirmed. For test responsiveness, all 3 test scores had significantly improved during rehabilitation, and the standardized response mean values ranged from 0.6 to 0.9. Conclusions The Wheelchair Circuit is a valid and responsive instrument with which to measure manual wheelchair mobility in subjects with SCI. © 2004 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

Rapid and extensive arterial adaptations after spinal cord injury

Contains fulltext : 50350.pdf (publisher's version ) (Closed access)OBJECTIVE: To assess the time course of adaptations in leg vascular dimension and function within the first 6 weeks after a spinal cord injury (SCI). DESIGN: Longitudinal study design. SETTING: University medical center and rehabilitation clinic. PARTICIPANTS: Six men were studied serially at 1, 2, 3, 4, and 6 weeks after SCI. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Diameter, blood flow, and shear rate levels of the common femoral artery (CFA), superficial femoral artery (SFA), brachial artery, and carotid artery were measured with echo Doppler ultrasound (diameter, blood flow, shear rate). Endothelial function in the SFA was measured with flow-mediated dilation (FMD). In addition, leg volume and blood pressure measurements were performed. RESULTS: Femoral artery diameter (CFA, 25%; SFA, 16%; P<.01) and leg volume (22%, P<.01) decreased simultaneously, and these reductions were largely accomplished within 3 weeks postinjury. Significant increases were observed for basal shear rate levels (64% increase at week 3; 117% increase at week 6; P<.01), absolute FMD responses (8% increase at week 3, 23% increase at week 6; P<.05) and relative FMD responses (26% increase at week 3, 44% increase at week 6; P<.001). CONCLUSIONS: Our findings show a rapid onset of adaptations in arterial dimension and function to extreme inactivity in humans. Vascular adaptations include extensive reductions in femoral diameter and leg volume, as well as increased basal shear rate levels and FMD responses, which all appear to be largely accomplished within 3 weeks after an SCI