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Three-Dimensional Kinematic Analysis of Racing Wheelchair Propulsion

Thomas J. O'Connor, Rick N. Robertson, Rory A. Cooper, Dept. Rehab. Science & Technology, University of Pittsburgh, Pittsburgh, PA. 15261 Human Engineering Research Laboratories, Highland Drive VA Medical Center, Pittsburgh, PA. 15206

ABSTRACT

This paper studied three-dimensional kinematic variables of racing wheelchair propulsion, and how they might improve the efficiency of racing wheelchair propulsion. Kinematic and physiological variables were collected on 6 male wheelchair athletes during 2 trial speeds maintained for 3 minutes. Significant results showed that the high group (HG) had a smaller elbow angle on hand contact (HC), was in contact with the pushrim for a shorter period of time, and had a higher wrist linear velocity on HC. The HG significantly increased their wrist and elbow linear velocities when speed was increased. The results of this study show that as wheelchair velocity increases the more efficient wheelchair propulsion technique incorporates less HC time with the pushrim and increases the wrist and elbow linear velocities which correlates to the `punching' of the pushrim technique.

BACKGROUND

Athletes with disabilities train just as hard or perhaps even harder than ambulatory athletes. The athletes with disabilities are looking for new and improved ways to train and/or analyze their propulsion technique so that they may improve their performance. The racing times and distances are improving; such that, small increments of improvement could lead to a world record. These athletes are looking for improvements in technology and training techniques in order to improve their performance. The upper extremities have a smaller muscle mass that can make it difficult to develop large forces. van der Woude et al.'s (1) research demonstrated that the gross mechanical efficiency ranged from 2 to 8% for normal daily activities. Grandjean (2) reported that normal walking was 27% efficient. Research has shown that daily wheelchair propulsion is far less efficient than walking (3), but the research of Cooper and Bedi (4) showed that wheelchair racers had a gross mechanical efficiency of over 30%. Assuming that manual wheelchair propulsion might not be efficient for everyday activity, how efficient is wheelchair propulsion for athletic competition? This study investigated kinematic and physiological variables for different efficiency groups to determine which mechanical variables are related to an improved efficiency in racing wheelchair propulsion.

METHODS

Six experienced male wheelchair athletes were used in this study. The kinematic data were collected by using three-dimensional camera view, and then the video was digitized with a motion analysis system (Peak5, Peak Performance Technologies Inc.). The resultant vectors of the wrist and elbow linear velocities were generated by the Pesk5 Analysis System for data analysis. The physiological data were collected simultaneously with the kinematic data using a cardio-pulmonary system (Q-Plex I Cardio-Pulmonary System, Quinton Instrument Co.). The physiological data were used to divide the subjects into high (HG) and low (LG) groups. Table 1 represents the medium (MED) and maximum (MAX) speeds used by the groups for the two trials. Each trial interval was performed for three minutes; however, the last trial continued until the athlete could no longer maintain that speed. The cameras were synchronized one minute into each trial, and this is where the digitization process was started.

MED MAX
LG 14 mph 18 mph
HG 16 mph 20 mph

Table 1.

RESULTS

The results of the kinematic data showed that, during the preparatory phase, the HG and LG had similar wrist linear velocity during the MED speed, but the HG increased the wrist linear velocity significantly (p<0.0001) for the MAX speed (Figure 1). There was a significant difference (p<0.05) between the MED and MAX speeds for both groups.

Figure 1. Wrist Velocity During the Preparatory Phase (meters/second)

The elbow linear velocity was significantly different (p<0.0001) for both groups between the MED and MAX speeds. The HG's elbow linear velocity was less then the LG's for the MED speed, but significantly increased (p<0.0001) for the MAX speed (Figure 2).

Figure 2. Elbow Velocity During the Preparatory Phase (meters/second)

The time of HC with the pushrim was significantly different (p<0.05) between the MED and MAX speeds for the two groups (Figure 3). The HG's HC time period was significantly less (p<0.0001) then the LG's during the MAX speed trial. There was a significant difference between the two speeds for the groups.

Figure 3. Time Period for Hand Contact with the Pushrim (seconds)

Wrist speed at HC was comparable for the two groups during the MED speed, but the HG significantly increased (p<0.0001) their wrist linear velocity at HC compared to the LG for the MAX speed (Figure 4). There was a significant difference (p<0.05) for both groups between the MED and MAX speeds, and a significant difference (p<0.05) between the HG's speeds when compared to the LG's speeds.

Figure 4. Wrist Velocity on Hand Contact with the Pushrim (meters/second)

DISCUSSION

The arm stroke pattern of wheelchair propulsion was divided into five phases for data analysis: 1) drive hands forward and downward, 2) pushrim contact, 3) hand on pushrim, 4) `flick' hand off the pushrim, and 5) elbow drive to the top (Robertson et al., 1991). For this study, phase one was considered the preparatory phase, phase two and three were the propulsion phase, and phase four and five were the recovery phase.

During the preparatory phase of the MAX trial, the HG generated a larger velocity with the wrist and elbow to transfer to the pushrim for propulsion. The increased velocities during the preparatory phase helped the HG to have larger velocities on HC. The increased elbow linear velocity during the MAX speed for the HG would contribute to why the wrist speed was significantly increased. The increased velocities on HC and a shorter time period of HC emphasized the `punching' of the pushrim technique. Studies have shown that this techniqueis a more efficient technique of wheelchair propulsion (Cooper, 1990). The HG's trunk position was more horizontal which enabled them to use gravity to enhance the wrist and elbow velocities on their downward flight to the pushrim.

The high wrist speed on impact with the pushrim could cause a substantial impact spike and shoulder load. If the shoulder strength is insufficient to maintain shoulder stability, injury may occur. This may help explain the high incidence of shoulder injuries to racing wheelchair athletes. Developing a more efficient stroke or adjusting the biomechanical aspects of the racing wheelchair propulsion technique could help the athlete to avoid some injuries. Future studies might investigate the wrist trajectory angle in relationship to the trunk position. The time period of HC with the pushrim can be analyzed with the relationship between the hand trajectory and the trunk position.

REFERENCES

1. van der Woude, L. H., Veeger, H. E., Rozendal, R. H., Van Ingen Schenau, G. J., Rooth, F., & Van Nierop, P. (1988). Wheelchair racing: Effects of rim diameter and speed on physiology and technique. Medicine and Science in Sport and Exercise, 20(5), 492-500.

2. Brattgard, S. O., Grimby, G., & Hook, O. (1970). Energy expenditure and heart rate in driving a wheel-chair ergometer. Scandinavian Journal of Rehabilitative Medicine, 2, 143-148.

3. Veeger, H., Hadj Yahmed, M., van der Woude, L., & Charpentier, P. (1991). Peak oxygen uptake and maximal power output of Olympic wheelchair-dependent athletes. Medicine and Science in Sports and Exercise, 23(10), 1201-1209.

4. Cooper, R. A. & Bedi, J. F. (1990). Gross mechanical efficiency of trained wheelchair racers. Proceedings 12th Annual International Conference of the IEEE/EMBS, Pennysylvania, Vol. 12(5), pp. 2311-2312.

5. Robertson, R. N., Cooper, R. A., & Baldini, F. D. (1991). Kinematics of wheelchair propulsion. National Wheelchair Athletic Association Newsletter, Summer, 10-11.

6. Cooper, R. A. (1990). An exploratory study of racing wheelchair propulsion dynamics. Adapted Physical Activity Quarterly, 7, 74-85.

Acknowledgment

This work was partially supported by the US Department of Education, Rehabilitation Services Administration, Rehabilitation Engineering and Assitive Technology Training (H129E50008); Department of Health and Physical Education, Calf. State Univ., Sacramento; Wheelchair Sports USA, and United States Olympic Committee.

Thomas J. O'Connor Human Engineering Research Laboratories Veterans Affairs Medical Center 7180 Highland Drive, 151R-1 Pittsburgh, Pennsylvania 15206