The physiological and biomechanical effects of forwards and reverse sports wheelchair propulsion.

OBJECTIVE: To explore the physiological and biomechanical differences between forwards (FOR) and reverse (REV) sports wheelchair propulsion. DESIGN: Fourteen able-bodied males with previous wheelchair propulsion experience pushed a sports wheelchair on a single-roller ergometer in a FOR and REV direction at three sub-maximal speeds (4, 6, and 8 km/hour). Each trial lasted 3 minutes, and during the final minute physiological and biomechanical measures was collected. RESULTS: The physiological results revealed that oxygen uptake (1.51 ± 0.29 vs. 1.38 ± 0.26 L/minute, P = 0.005) and heart rate (121 ± 19 vs. 109 ± 14 beats/minute, P < 0.0005) were significantly greater during REV than FOR only during the 8 km/hour trials. From a biomechanical perspective, push frequencies were similar between FOR and REV across all speeds (P > 0.05). However, greater mean resultant forces were applied during FOR (P < 0.0005) at 4 km/hour (66.7 ± 19.5 vs. 49.2 ± 10.3 N), 6 km/hour (90.7 ± 21.9 vs. 65.3 ± 18.6 N), and 8 km/hour (102.5 ± 17.6 vs. 68.7 ± 13.5 N) compared to REV. Alternatively, push times and push angles were significantly lower (P ≤ 0.001) during FOR at each speed. CONCLUSIONS: The current study demonstrated that at higher speeds physiological demand becomes elevated during REV. This was likely to be associated with an inability to apply sufficient force to the wheels, thus requiring kinematic adaptations in order to maintain constant speeds in REV.

The verification phase and reliability of physiological parameters in peak testing of elite wheelchair athletes.

The purpose of this study was (1) to examine the value of a verification phase (VER) in a peak testing protocol and (2) to assess the reliability of peak physiological variables in wheelchair athletes. On two separate days, eight tetraplegic (TETRA), eight paraplegic (PARA) and eight non-spinal cord-injured (NON-SCI) athletes performed treadmill ergometry, consisting of a graded exercise test to exhaustion (GXT) followed by a VER. Peak oxygen uptake (.VO2peak) was compared (1) between GXT and VER and (2) between test days. .VO2peak did not differ between GXT and VER (P = 0.27), and coefficients of variation between GXT and VER were in the range of 2.9 and 6.4 % for all subgroups. Coefficients of variation of .VO2peak between test days were 9.3 % (TETRA), 4.5 % (PARA) and 3.3 % (NON-SCI). It is therefore concluded that whilst a VER can be used for a more robust determination of .VO2peak, a deviation of up to ~6 % between GXT and VER should be considered as acceptable. For between-day analyses, relatively large changes in .VO2peak are required to confirm "true" differences, especially in TETRA athletes. This may be due to their lower aerobic capacity, which results in a larger relative variation compared with the other subgroups.

Criterion validity and accuracy of global positioning satellite and data logging devices for wheelchair tennis court movement.

PURPOSE: To compare the criterion validity and accuracy of a 1 Hz non-differential global positioning system (GPS) and data logger device (DL) for the measurement of wheelchair tennis court movement variables. METHODS: Initial validation of the DL device was performed. GPS and DL were fitted to the wheelchair and used to record distance (m) and speed (m/second) during (a) tennis field (b) linear track, and (c) match-play test scenarios. Fifteen participants were monitored at the Wheelchair British Tennis Open. RESULTS: Data logging validation showed underestimations for distance in right (DLR) and left (DLL) logging devices at speeds >2.5 m/second. In tennis-field tests, GPS underestimated distance in five drills. DLL was lower than both (a) criterion and (b) DLR in drills moving forward. Reversing drill direction showed that DLR was lower than (a) criterion and (b) DLL. GPS values for distance and average speed for match play were significantly lower than equivalent values obtained by DL (distance: 2816 (844) vs. 3952 (1109) m, P = 0.0001; average speed: 0.7 (0.2) vs. 1.0 (0.2) m/second, P = 0.0001). Higher peak speeds were observed in DL (3.4 (0.4) vs. 3.1 (0.5) m/second, P = 0.004) during tennis match play. CONCLUSIONS: Sampling frequencies of 1 Hz are too low to accurately measure distance and speed during wheelchair tennis. GPS units with a higher sampling rate should be advocated in further studies. Modifications to existing DL devices may be required to increase measurement precision. Further research into the validity of movement devices during match play will further inform the demands and movement patterns associated with wheelchair tennis.

Practice improves court mobility and self-efficacy in tennis-specific wheelchair propulsion.

PURPOSE: Wheelchair tennis (WT) propulsion is uniquely characterized by the requirement for racket holding coupled with effective hand-rim contact. Thus, investigations involving strategies to enhance chair mobility skills are merited. The aim was to examine the effects of organized practice on WT match play responses and the impact of racket holding during practice. MATERIALS AND METHODS: Following physiological profiling involving graded and peak exercise testing, 16 able-bodied (AB) participants performed bouts of WT match play interspersed with practice involving wheelchair mobility drills completed with (R) or without (NR) a tennis racket. A data logger recorded distance and speed. Self-efficacy was reported. RESULTS AND CONCLUSIONS: Significant main effects for match revealed higher post-practice overall and forwards distances (p < 0.05), peak (p < 0.005) and average (p < 0.05) speeds and self-efficacy (SE) (p = 0.001) were attained. During practice, lower distances and speeds were achieved with R, with a lower physiological cost than NR. Practice increases court movement and SE with no associated increases in physiological cost. Changes represent enhanced court mobility. Differences between practice characteristics provide options for skill development and optimization of health outcomes.IMPLICATIONS FOR REHABILITATIONWheelchair tennis participation is likely to confer positive health effects in those with a disability or physical impairment.As chair propulsion combined with racket holding represents a complex skill challenge, novices may find the sport challenging to play.Tennis-specific mobility drills improve confidence and chair propulsion skill with likely crossover into tennis match play competence and ability.

Measuring Handrim Wheelchair Propulsion in the Lab: A Critical Analysis of Stationary Ergometers.

There are many ways to simulate handrim wheelchair propulsion in the laboratory. Ideally, these would be able to, at least mechanically, simulate field conditions. This narrative review provides an overview of the lab-based equipment used in published research and critically assesses their ability to simulate and measure wheelchair propulsion performance. A close connection to the field can only be achieved if the instrument can adequately simulate frictional losses and inertia of real-life handrim wheelchair propulsion, while maintaining the ergonomic properties of the wheelchair-user interface. Lab-based testing is either performed on a treadmill or a wheelchair ergometer (WCE). For this study WCEs were divided into three categories: roller, flywheel, and integrated ergometers. In general, treadmills are mechanically realistic, but cannot simulate air drag and acceleration tasks cannot be performed; roller ergometers allow the use of the personal wheelchair, but calibration can be troublesome; flywheel ergometers can be built with commercially-available parts, but inertia is fixed and the personal wheelchair cannot be used; integrated ergometers do not employ the personal wheelchair, but are suited for the implementation of different simulation models and detailed measurements. Lab-based equipment is heterogeneous and there appears to be little consensus on how to simulate field conditions.

Spinal cord injury level and the circulating cytokine response to strenuous exercise.

PURPOSE: A complete spinal cord injury (SCI) above the sixth thoracic vertebra (T6) results in the loss of sympathetic innervation of the adrenal medulla. This study examined the effect of a complete SCI above and below T6 on plasma concentrations of epinephrine, circulating interleukin 6 (IL-6) and other inflammatory cytokines in response to acute strenuous exercise. METHODS: Twenty-six elite male wheelchair athletes (8 = C6-C7 tetraplegic [TETRA], 10 = T6-L1 paraplegic [PARA], and 8 = non-spinal-cord-injured controls [NON-SCI]) performed a submaximal exercise test followed by a graded exercise to exhaustion on a motorized treadmill. Blood samples were taken preexercise, postexercise, and 30 min postexercise and analyzed for concentrations of IL-6, IL-10, IL-1 receptor antagonist (IL-1ra), tumor necrosis factor α (TNF-α), epinephrine, and cortisol. RESULTS: The circulating IL-6 concentration was significantly elevated at postexercise and 30 min postexercise (post30; approximately fivefold) in NON-SCI and PARA (P = 0.003), whereas concentrations in TETRA did not change significantly from preexercise values. IL-10, IL-1ra, and TNF-α were unaffected by exercise in all groups; however, both SCI groups presented elevated concentrations of IL-10 compared with NON-SCI (P = 0.001). At postexercise, epinephrine concentrations were significantly higher than preexercise and post30 concentrations in NON-SCI (approximately threefold) and PARA (approximately twofold) (P = 0.02). Plasma epinephrine concentrations were unchanged in TETRA throughout exercise; concentrations were significantly lower than NON-SCI and PARA at all time points. Plasma cortisol concentrations were significantly elevated in all groups at postexercise and post30 compared with preexercise (P < 0.001). Total exercise time was similar between groups (NON-SCI = 38 ± 6; PARA = 35 ± 5; TETRA = 36 ± 5 min). CONCLUSIONS: These findings suggest that the sympathetic nervous system plays an important regulatory role in the circulating IL-6 response to exercise and has implications for the metabolic and inflammatory responses to exercise in individuals with injuries above T6.

Wheelchair tennis match-play demands: effect of player rank and result.

PURPOSE: To examine the heart-rate (HR) response and court-movement variables during wheelchair tennis match play for high- (HIGH) and low- (LOW) performance-ranked players. Analysis of physiological and movement-based responses during match play offers an insight into the demands of tennis, allowing practical recommendations to be made. METHODS: Fourteen male open-class players were monitored during tournament match play. A data logger was used to record distance and speed. HR was recorded during match play. RESULTS: Significant rank-by-result interactions revealed that HIGH winners covered more forward distance than HIGH losers (P < .05) and had higher average (P < .05) and minimum (P < .01) HRs than LOW winners. LOW losers had higher average (P < .01) and minimum (P < .001) HRs than LOW winners. Independent of result, a significant main effect for rank was identified for maximum (P < .001) and average (P < .001) speed and total (P < .001), reverse (P < .001), and forward-to-reverse (P < .001) distance, with higher values for HIGH. Independent of rank, losing players experienced higher minimum HRs (P < .05). Main effects for maximum HR and actual playing time were not significant. Average playing time was 52.0 (9.1) min. CONCLUSIONS: These data suggest that independent of rank, tennis players were active for sufficient time to confer health-enhancing effects. While the relative playing intensity is similar, HIGH players push faster and farther than LOW players. HIGH players are therefore more capable of responding to ball movement and the challenges of competitive match play. Adjustments to the sport may be required to encourage skill developmental in LOW players, who move at significantly lower speeds and cover less distance.

Effects of wheel and hand-rim size on submaximal propulsion in wheelchair athletes.

PURPOSE: This study aimed to investigate the effects of fixed gear ratio wheel sizes on the physiological and biomechanical responses to submaximal wheelchair propulsion. METHODS: Highly trained wheelchair basketball players (N = 13) propelled an adjustable sports wheelchair in three different wheel sizes (24, 25, and 26 inches) on a motor-driven treadmill. Each wheel was equipped with force-sensing hand-rims (SMARTWheel), which collected kinetic and temporal data. Oxygen uptake (V˙O2) and HR responses were measured with high-speed video footage collected to determine three-dimensional upper body joint kinematics. RESULTS: Mean power output and work per cycle decreased progressively with increasing wheel size (P < 0.0005). Increasing wheel size also reduced the physiological demand with reductions in VO2 for 25-inch (0.90 ± 0.20 L · min(-1), P = 0.01) and 26-inch wheels (0.87 ± 0.16 L · min(-1), P = 0.001) compared with 24-inch wheels (0.98 ± 0.20 L · min(-1)). In addition, reductions in HR were observed for 26-inch wheels (99 ± 6 beats · min(-1)) compared with 25-inch (103 ± 8 beats · min(-1), P = 0.018) and 24-inch wheels (105 ± 9 beats · min(-1), P = 0.004). Mean resultant forces also decreased progressively with increasing wheel size (P < 0.0005). However, no changes in temporal or upper body joint kinematics existed between wheel sizes. CONCLUSIONS: A greater power requirement owing to a greater rolling resistance in 24-inch wheels increased the physiological demand and magnitude of force application during submaximal wheelchair propulsion.

Wheelchair propulsion: effects of experience and push strategy on efficiency and perceived exertion.

The purpose of this study was to examine the role of wheeling experience on efficiency, metabolic cost, and differentiated ratings of perceived exertion (RPEs) during synchronous and asynchronous hand-rim propulsion with varying arm frequencies. Fourteen able-bodied (AB) male participants and 8 male wheelchair sportsmen (WS) performed tests of peak oxygen consumption for both propulsion modes. Subsequently, 2 series of five 4-min sub-maximal exercise bouts were completed at an individualized velocity (60% of peak oxygen consumption). Arm frequencies consisted of the freely chosen frequency (FCF), followed by 4 counter-balanced paced trials pushing at 60%, 80%, 120%, and 140% of the FCF. Efficiency indices (gross, GE; work, WE) were determined and peripheral (RPE-P), central (RPE-C), and overall (RPE-O) RPEs were recorded. The GE (6.4% vs. 8.4%) and WE (11.3% vs. 15.1%) were significantly higher in WS than in AB (p = 0.001). Trends in the oxygen consumption, GE, and WE data were similar in both groups, propulsion mode, and arm frequency. Data suggest that 80% FCF resulted in improved efficiency for both propulsion mode and group, although the differences between those arm frequencies immediately above and below were non-significant. Lower RPE scores corresponded with higher efficiency values. Regardless of group there were significant differences (p = 0.001) between the differentiated RPE measures, whereby RPE-P was on average always the highest score (13.1) and RPE-C the lowest (11.1; RPE-O was 12.2). In conclusion, despite the anticipated differences in efficiency between the WS and AB participants, this study confirmed that psycho-physiological measures produce similar trends to physiological measures with manipulations of both arm frequency and propulsion mode.

A comparison between intermittent and constant wheelchair propulsion strategies.

The purpose of this study was to investigate the effect of different synchronous push strategies on physiological parameters and temporal timing characteristics. Eight novice male able-bodied participants completed four counter-balanced conditions: two push strategies (constant pushing) and intermittent pushing (INT) at two push frequencies (40 and 70 pushes/min) at 27 W. The ANOVA main effects for frequency indicated that regardless of push strategy, oxygen cost and mechanical efficiency increased with an increase in push frequency (p < 0.01). The INT40 strategy resulted in the lowest heart rate (115 +/- 19 beats/min). With increased frequency the push angle was reduced (91 degrees vs. 78 degrees respectively) and the push was initiated at a more anterior position of the wheel (p < 0.05). The results suggest that regardless of push strategy, the over-riding factor that influences both the physiological and timing parameters measured was push frequency.