Effect of push frequency and strategy variations on economy and perceived exertion during wheelchair propulsion
ABSTRACT Wheelchair locomotion is a cyclical activity and participants are free to select any push frequency-propulsion strategy combination that suits their needs at a given power output. The aim of the study was to examine the physiological effects of varying push frequency and strategy on pushing economy. Twelve male, able-bodied participants completed four, randomly assigned, 5-min bouts of submaximal exercise at 32 W on a wheelchair ergometer. Each bout of exercise combined two different push frequencies (40 and 70 push min(-1)), with one of two different push strategies [synchronous (SYN): both arms pushing together, and asynchronous: one arm applying force to the wheel at a time). Physiological measures included oxygen uptake ( VO(2)), heart rate (HR) and blood lactate [La](b )concentration. Differentiated ratings of perceived exertion (RPE) were also recorded (overall, local and central). Separate ANOVA were used for VO(2), HR, [La](b) and RPE as the dependent variables. Where significant differences were identified, a Bonferroni post hoc test was used. The main effect for push frequency by strategy was significant for VO(2) ( P<0.01). Scrutiny of the HR values showed that the SYN 40 condition was significantly less stressful than all other frequency-strategy combinations ( P<0.01). RPE data supported these findings although they were found to be non-significant. When looking at [La](b,) both of the main effects were also significant showing the concentration was lower on average when the push rate was 40 as opposed to 70 (1.65 vs 2.14 mmol l(-1); P<0.01). This study provides further evidence that a low push frequency provides the most economical form of wheelchair propulsion especially when combined with a SYN strategy.
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ABSTRACT: Abstract Purpose: This study aimed to first investigate synchronous (SYN) versus asynchronous (ASY) mode of propulsion and, second, investigate the wheel camber effects on sprinting performance as well as temporal parameters. Method: Seven wheelchair basketball players performed four maximal eight-second sprints on a wheelchair ergometer. They repeated the test according to two modes of propulsion (SYN and ASY) and two wheel cambers (9° and 15°). Results: The mean maximal velocity and push power output was greater in the synchronous mode compared to the asynchronous mode for both camber angles. However, the fluctuation in the velocity profile is inferior for ASY versus SYN mode for both camber angles. Greater push time/cycle time (Pt/Ct) and arm frequency (AF) for synchronous mode versus asynchronous mode and inversely, lesser Ct and rest time (Rt) values for the synchronous mode, for which greater velocity were observed. Conclusions: SYN mode leads to better performance than ASY mode in terms of maximal propulsion velocity. However, ASY propulsion allows greater continuity of the hand-rim force application, reducing fluctuations in the velocity profile. The camber angle had no effect on ASY and SYN mean maximal velocity and push power output. Implications for Rehabilitation The study of wheelchair propulsion strategies is important for better understanding physiological and biomechanical impacts of wheelchair propulsion for individuals with disabilities. From a kinematical point of view, this study highlights synchronous mode of propulsion to be more efficient, with regards to mean maximal velocity reaching during maximal sprinting exercises. Even if this study focuses on well-trained wheelchair athletes, results from this study could complement the knowledge on the physiological and biomechanical adaptations to wheelchair propulsion and therefore, might be interesting for wheelchair modifications for purposes of rehabilitation.Disability and rehabilitation. Assistive technology 01/2013; DOI:10.3109/17483107.2012.756947
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ABSTRACT: Optimizing mobility performance in wheelchair court sports (basketball, rugby and tennis) is dependent on a combination of factors associated with the user, the wheelchair and the interfacing between the two. Substantial research has been attributed to the wheelchair athlete yet very little has focused on the role of the wheelchair and the wheelchair-user combination. This article aims to review relevant scientific literature that has investigated the effects of wheelchair configuration on aspects of mobility performance from an ergonomics perspective. Optimizing performance from an ergonomics perspective requires a multidisciplinary approach. This has resulted in laboratory-based investigations incorporating a combination of physiological and biomechanical analyses to assess the efficiency, health/safety and comfort of various wheelchair configurations. To a lesser extent, field-based testing has also been incorporated to determine the effects of wheelchair configuration on aspects of mobility performance specific to the wheelchair court sports. The available literature has demonstrated that areas of seat positioning, rear wheel camber, wheel size and hand-rim configurations can all influence the ergonomics of wheelchair performance. Certain configurations have been found to elevate the physiological demand of wheelchair propulsion, others have been associated with an increased risk of injury and some have demonstrated favourable performance on court. A consideration of all these factors is required to identify optimal wheelchair configurations. Unfortunately, a wide variety of different methodologies have immerged between studies, many of which are accompanied by limitations, thus making the identification of optimal configurations problematic. When investigating an area of wheelchair configuration, many studies have failed to adequately standardize other areas, which has prevented reliable cause and effect relationships being established. In addition, a large number of studies have explored the effects of wheelchair configuration in either able-bodied populations or in daily life or racing wheelchairs. As such, the findings are not specific and transferable to athletes competing in the wheelchair court sports. This review presents evidence about the effects of wheelchair configuration on aspects of mobility performance specific to the wheelchair court sports to better inform athletes, coaches and manufacturers about the consequences of their selections. It also provides researchers with guidance on the design of future investigations into areas of wheelchair configuration, which are essential.Sports Medicine 01/2013; 43(1):23-38. DOI:10.1007/s40279-012-0005-x · 5.32 Impact Factor
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ABSTRACT: Introduction. – Individualised exercise training programs in spinal cord injury (SCI) individuals are considered highly effective for improving and maintaining capacity for physical activity, as well as for reducing cardiovascular risk. However, no consensus exists on the type, intensity, and frequency of the training programs for SCI.Objective. – To review the literature about training program characteristics for SCI and describe their efficacy, limits, and results, with the aim of proposing specific recommendations.Methods. – Query using Medline and Embase databases. Ninety-nine references were found, including the following: Clinical studies examining physical endurance capacity of individuals with SCI, physiological responses to maximal exercise, or cardiovascular differences between sedentary and wheelchair-trained subjects; Articles? investigating the effects of training programmes for SCI.Results. – Various combinations of training intensity, duration, frequency, type, and ergometers have been proposed for SCI. Whatever the characteristics of the training program, a review of 25 cardiorespiratory training studies involving SCI subjects revealed an average improvement of 9% to 99% in VO2max, 19% to 118% in power output, and a decrease in submaximal values after 4 to 36 weeks of training.Discussion – Conclusion. – Wheelchair ergometers seems to be interesting for SCI because it mimics closely the daily motor tasks of wheelchair users and allows for adjustment of the wheelchair. Both continuous and interval training programmes are appropriate, but intermittent exercise intensities may be more beneficial since they mimic the intermittent nature of daily activity patterns. Furthermore, on the basis of the results of these studies, we recommend that training at or above 70% of maximum heart rate, for 30 minutes of rhythmic exercise, three days per week during eight weeks, will provide a sound of basis for design of an endurance exercise programme for people with SCI.Annales de Réadaptation et de Médecine Physique 06/2005; 48(5):259-269. DOI:10.1016/j.annrmp.2004.12.004