Efficiency of Wheelchair Propulsion and Effects of Strategy

Sex differences in wheelchair propulsion biomechanics and mechanical efficiency in novice young able-bodied adults

An awareness of sex differences in gait can be beneficial for detecting the early stages of gait abnormalities that may lead to pathology. The same may be true for wheelchair propulsion. The aim of this study was to determine the effect of sex on wheelchair biomechanics and mechanical efficiency in novice young able-bodied wheelchair propulsion. Thirty men and 30 women received 12  min of familiarisation training. Subsequently, they performed two 10-m propulsion tests to evaluate comfortable speed (CS). Additionally, they performed a 4-min submaximal propulsion test on a treadmill at CS, 125% and 145% of CS. Propulsion kinetics (via Smart^wheel) and oxygen uptake were continuously measured in all tests and were used to determine gross mechanical efficiency (GE), net efficiency (NE) and fraction of effective force (FEF). Ratings of perceived exertion (RPE) were assessed directly after each trial. Results indicated that CS for men was faster (0.98 ± 0.24 m/s) compared to women (0.71 ± 0.18 m/s). A lower GE was found in women compared to men. Push percentage, push angle and local RPE were different across the three speeds and between men and women. NE and FEF were not different between groups. Thus, even though their CS was lower, women demonstrated a higher locally perceived exertion than men. The results suggest sex differences in propulsion characteristics and GE. These insights may aid in optimising wheelchair propulsion through proper training and advice to prevent injuries and improve performance. This is relevant in stimulating an active lifestyle for those with a disability.

Partitioning kinetic energy during freewheeling wheelchair maneuvers

This paper describes a systematic method to partition the kinetic energy (KE) of a free-wheeling wheelchair. An ultralightweight rigid frame wheelchair was instrumented with two axle-mounted encoders and data acquisition equipment to accurately measure the velocity of the drive wheels. A mathematical model was created combining physical specifications and geometry of the wheelchair and its components. Two able-bodied subjects propelled the wheelchair over four courses that involved straight and turning maneuvers at differing speeds. The KE of the wheelchair was divided into three components: translational, rotational, and turning energy. This technique was sensitive to the changing contributions of the three energy components across maneuvers. Translational energy represented the major component of total KE in all maneuvers except a zero radius turn in which turning energy was dominant. Both translational and rotational energies are directly related to wheelchair speed. Partitioning KE offers a useful means of investigating the dynamics of a moving wheelchair. The described technique permits analysis of KE imparted to the wheelchair during maneuvers involving changes in speed and direction, which are most representative of mobility in everyday life. This technique can be used to study the effort required to maneuver different types and configurations of wheelchairs.

Supporting the paralympic athlete: focus on wheeled sports

The complexity of wheelchair sports provides the scientist with a unique challenge. There are two major components that contribute towards 'wheeled sports' performance: the athlete and the chair. It is the interaction of these two components that enable wheelchair propulsion and the sporting movements required within a given sport. This article will describe three discrete case studies on how sport scientists have worked with Great Britain coaches and practitioners to help optimise training leading to a major competition through evidence base practise. A fourth area will describe on-going work designed to address the optimisation of wheelchair configurations for wheelchair court sports. It will focus on four sports: wheelchair racing, wheelchair tennis, wheelchair basketball and wheelchair rugby. The first topic will discuss the concept of pushing economy and mechanical efficiency of wheelchair propulsion. The second topic will show how technology assists the coaching process. The third topic will illustrate the concept of sports classification, and show how training volume 'in terms of basketball shooting' may need to be individually assigned and finally future research within wheelchair team sports and chair configurations will be examined.

Effects of 4-weeks of asynchronous hand-rim wheelchair practice on mechanical efficiency and timing

PURPOSE

To investigate the consequence on gross mechanical efficiency (GE), arm frequency and sub-maximal performance, of paced and unpaced practice during asynchronous hand-rim wheelchair propulsion.

METHODS

Twenty-five able-bodied participants performed five, 4-min exercise bouts at 1.7 m/s, at the freely chosen frequency (FCF) and four paced arm frequencies of 60, 80, 120 and 140% FCF. GE, arm frequency and measures of sub-maximal performance were determined. Participants were assigned to an unpaced (FCF, N = 9), paced (80% FCF, N = 8) or control (CON, N = 8) no practice group. The FCF and 80% FCF groups received 4-weeks (unpaced and paced, respectively) propulsion practice (three sessions·per wk, four 4 min/trials; 33-35 W) at 1.7 m/s on a wheelchair ergometer. Following practice, the pre-testing protocol was repeated.

RESULTS

Mean GE showed a relative increase in both experimental groups (21 and 17%; FCF and 80% FCF respectively; p = 0.001) compared to no change in CON (-1.5%). The FCF arm frequency decreased in both experimental groups (p = 0.001), with larger changes evident following FCF practice.

CONCLUSION

Four weeks of unpaced or paced practice had a beneficial effect on GE. This improvement seems to be associated with a reduction in arm frequency.