- Email: [email protected]
Eye-hand Coordination of Elderly People Who Practice Tai Chi Chuan
ORIGINAL ARTICLE
Eye-hand Coordination of Elderly People Who Practice Tai Chi Chuan Yu-Cheng Pei,1 Shih-Wei Chou,1 Pay-Shih Lin,2 Yin-Chou Lin,1 Tony H.C. Hsu,1 Alice M.K. Wong1* Background/Purpose: The objective of this study was to evaluate the effect of motor control from Tai Chi Chuan (TCC) on eye-hand coordination in the elderly. Methods: Forty-two elderly people were recruited into this study. People in the TCC group (n = 22) had been practicing TCC regularly for more than 3 years. The control group (n = 20) comprised healthy and active elderly people. Subjects were asked to stroke target sensors in a test device with computer recording. There were three different target sensor sizes (1 cm, 1.5 cm and 2 cm in diameter) for different tests. For each target stroking, the following were recorded and calculated: start and end positions, duration of movement, pause time, peak velocity, and the time to reach peak velocity. Results: The TCC group showed significantly better results in decrease of displacement (p = 0.003), movement time (p = 0.002), pause time (p < 0.001), number of submovements (p = 0.001), and better skewness coefficients (p < 0.001) than the control group. However, the difference in the peak velocity of the TCC and control groups did not reach statistical significance (p = 0.026). Conclusion: The elderly TCC group had better results on the eye-hand coordination test than the control elderly group. [J Formos Med Assoc 2008;107(2):103–110] Key Words: elderly, eye-hand coordination, motor control, Tai Chi, Tai Chi Chuan
people. The basic TCC exercise is practiced in a semi-squat posture with a series of continual motions, similar to the push-pull of an invisible rival at a very slow speed. During the practice of TCC, diaphragmatic breathing and mental concentration with the eyes following the graceful movements of the upper extremities (such as cloud hand form) are emphasized. Shadow boxing is used to describe this unique exercise pattern.3 In recent years, TCC has gradually become a popular exercise in the Western world and investigations are flourishing. There is evidence to show that the practice of TCC leads to improvements
Quality of life in the elderly is closely related to their physical fitness. Recent studies have shown that supervised exercises for the elderly that emphasize aerobic, strength, flexibility and balance training can improve their fitness.1,2 There are few vigorous exercises that are suitable for older people due to the effects of wear and tear with aging, such as joint degeneration, poor eyesight or poor balance. Low-velocity and low-impact coordination exercises that are of low cost and easily accessible are more suitable for older people.1,2 Tai Chi Chuan (TCC) is a traditional Chinese coordination exercise that is suitable for older
©2008 Elsevier & Formosan Medical Association .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1
Department of Physical Medicine and Rehabilitation, Chang Gung Memorial Hospital, and 2Department of Physical Therapy, Institute of Gerontology and Research Center, Chang Gung University, Taoyuan, Taiwan. Received: May 2, 2007 Revised: August 23, 2007 Accepted: October 2, 2007
J Formos Med Assoc | 2008 • Vol 107 • No 2
*Correspondence to: Dr Alice M.K. Wong, Department of Physical Medicine and Rehabilitation, Chang Gung Memorial Hospital, 5 Fu-Hsin Street, Kwei-Shan, Taoyuan 333, Taiwan. E-mail: [email protected]
103
Y.C. Pei, et al
Table 1. Demographic data of the Tai Chi Chuan (TCC) and control groups*
Sex (M/F) Age (yr) Body weight (kg) Body height (cm)
TCC (n = 22)
Control (n = 20)
p
8/14 67.8 ± 5.1 58.0 ± 5.1 156.6 ± 4.7
5/15 68.2 ± 5.2 56.8 ± 8.2 157.2 ± 4.4
0.420 0.845 0.403 0.620
*Data are presented as n or mean ± standard deviation.
in cardiovascular function, balance, flexibility, strength, kinesthetic senses and falls reduction.4–14 However, there are few reports that draw out the roles and benefits of motor control in the upper extremities, though TCC practitioners need delicate eye-hand coordination.15 Eye-hand coordination is essential to carry out daily activities and self care, especially in the elderly. They are insufficient to prepare their movement and have to control their movement through visual guidance.16 Elderly people generally need a longer time to initiate a movement and to guide their movements than young people.17,18 They are also more likely to stop and readjust their movements during what should be a smooth execution of movement.19 This study was therefore designed to investigate the performances of eye-hand coordination and motor control in the upper extremities of TCC practitioners, to determine whether or not TCC has beneficial effects.
Methods Subjects TCC subjects were recruited from a Tai Chi club and control subjects were recruited from volunteer groups at Chang Gung Memorial Hospital. All subjects were community dwellers and led an active lifestyle that consisted of regular exercise at least three times a week. None had a history of falls in the last 3 months. At the time of recruitment, TCC subjects had practiced TCC regularly for more than 3 years; they practiced TCC five to seven times a week for 1–2 hours each day according to the Yong style. 104
All subjects were healthy and examined by the same physician. Subjects who had a history of significant cardiovascular, pulmonary, metabolic, musculoskeletal (e.g. joint fracture, artificial joint replacement) or neurologic (e.g. stroke, Parkinson’s disease, dementia, poor vision) disease were excluded. Twenty-two TCC practitioners (8 men, 14 women; mean age, 67.8 ± 5.1 years) and 20 active non-TCC practitioners (5 men, 15 women; mean age, 68.2 ± 5.2 years) were recruited for this study. No significant differences were noted between groups with regard to sex, age, body weight and body height (Table 1).
Measurement equipment The test device was developed according to the concept of Fitts’ Law and Welford et al’s study.19,20 Figure 1A shows the test device and the arrangement of target sensors of various sizes that are embedded in the laboratory table during the repetitive hand function tests. Subjects were instructed to hold a pencil-like stick and asked to stroke the target sensors in a desired order with the stick (Figure 1B). The target sensors detected the sequence of strokes so as to calculate the movement time and to determine the accuracy of the movement sequences.
Procedure Before the experiment was begun, an explanatory statement and verbal explanation of what the task entailed were given to subjects. They were allowed to wear their glasses if needed. The experimenter also gave comprehensive demonstrations of how the task should be done. Preliminary practice at performing the task was permitted so J Formos Med Assoc | 2008 • Vol 107 • No 2
Effect of Tai Chi Chuan on eye-hand coordination
A
B 800
Z Y
700 Y axis
X
35
600 500 400
cm Marker
300 100
150
200
250
300
350
X axis Figure 1. (A) Set-up of a stroking hand movement projected on the horizontal plane. (B) The stroking movements are initiated at the left uppermost sensor to right uppermost sensor sequentially, and end at the left lowest sensor.
that subjects could familiarize themselves with the task. All subjects signed an informed consent form prior to participation. When the first task was presented, they were requested to adjust their sitting position with the adjustable chair to 90 degrees of hip and knee flexion with both feet on the ground. The table was also adjusted to elbow height (humerus and forearm in vertical position) during sitting position. Subjects were asked to perform at their fastest speed while stroking the center of each target in sequence along a route that was the shape of the letter “S” (Figure 1B). Twenty trials were completed at the fastest speed before the subject was presented with the next target arrangement. Total movement time was required to be within 10% of either side of the mean values determined from the pilot study. Trials were repeated only if accuracy was questionable or targets missing. The trial was excluded if the same target was stroked twice during the route or if targets were stroked out of sequence and not in accordance with the route. To test the intrasubject reliability of eyehand coordination parameters, each participant was repeatedly evaluated for each test condition 7–10 days later.
Data analysis In the first stage of the analysis, computer records of the timing of stroking the targets were identified at the beginning and end of each movement. J Formos Med Assoc | 2008 • Vol 107 • No 2
In the second stage, the features of interest were determined using automatic algorithms. Movement duration was based on the time spent in movement, and pause times were excluded. Stroked targets were determined from the computer records and each time the stick stroked the target was recorded. For each stroked target, the start and end positions, movement duration, pause time, peak velocity, time to reach peak velocity, and time to decelerate from peak velocity to zero were calculated. Pause time was defined as the time (ms) spent stationary at a target between two strokes (hypothesized to be an indication of the planning time between movements). Movement time was defined as the total time (ms) spent moving between targets in a trial, excluding all pause time. Movements were defined as the periods between points of zero velocity in the velocity profile, which correspond to the targets in the temporal profiles. While joining 11 targets should only require 10 movements, subjects occasionally made additional submovements between targets; these submovements were counted, analyzed separately, and then screened for further analysis. Subsequent analysis focused on the 10 primary movements, that is, the 10 movements with the greatest peak velocity (rather than any submovements). Features of interest in the velocity function of these selected movements were then entered into a database, where measures (of the time to peak 105
Y.C. Pei, et al
Table 2. Interclass correlation coefficients for each parameter Parameter Movement displacement Movement time Pause time Peak velocity
Large target
Medium target
Small target
0.820* 0.935* 0.880* 0.824*
0.836* 0.881* 0.876* 0.780*
0.808* 0.847* 0.833* 0.768*
*p < 0.05.
velocity and time from peak to zero velocity) were used to calculate a skewness coefficient (SC) that indicates the relative duration of the acceleration and deceleration phases of the movements. Submovements: the number of zero crossing in the velocity profile provides an indication of the number of submovements. The efficient performance of this stroking task requires only 10 movements, one for each stroke. The greater the number of submovements, the more inefficient the drawing strokes. The SC was used to measure the symmetry in movement control. An efficient movement (not involving terminal impact) minimizes jerk.21 The time to peak velocity relative to the time from peak to zero velocity was used as an index. A ratio greater than 1 suggests prolonged periods of acceleration and problems of force production, while a ratio < 1 indicates prolonged periods of deceleration and guidance.22,23 An efficient movement (not involving terminal impact) minimizes jerk and the ratio should be close to 1. Statistical analysis was performed using SPSS version 10.0 (SPSS Inc., Chicago, IL, USA). Interclass correlation coefficients (ICCs) were calculated for intrasubject reliability of eye-hand coordination parameters. Student’s t test was used to compare the differences in age, body weight, body height, and hand movement parameters between the TCC and control groups. Fisher’s exact test was used for sex distribution comparison. ANOVA for repeated measures (3 target sizes) was used to compare the hand movement parameters. Post hoc comparisons were made using the least significant difference test. Statistical significance was set at p < 0.05. 106
Results ICCs for the intrasubject reliability of eye-hand coordination parameters are shown in Table 2. All of the parameters, including movement displacement, movement time, pause time and peak velocity, were significantly reliable (p < 0.05). There were no significant differences with regard to age, sex, body weight and body height between the TCC and control groups. The hand reactive parameters in TCC and control subjects are shown in Table 3. The differences in movement displacement for large and small targets were significant between the two groups (p < 0.05), but the difference for mediumsized targets was not. For movement and pause times, there were significantly better results in the TCC group than in the control group for all three different target sizes (both p < 0.05). There were, however, no significant differences in peak velocity between the TCC and control groups for any of the three different target sizes. Overall, there were significant differences in movement displacement (p = 0.003), movement time (p = 0.002), pause time (p < 0.001) and peak velocity (p = 0.001) between the two groups. The significant differences in movement displacement and velocity between the two groups are illustrated in Figures 2 and 3. The comparison of submovements and skewness between the two groups are shown in Figure 4. There were significant differences in the number of submovements (p = 0.001) and SC (p < 0.001) between the two groups. A decrease in movement displacement, movement time and pause time, and an increase in SC J Formos Med Assoc | 2008 • Vol 107 • No 2
Effect of Tai Chi Chuan on eye-hand coordination
Table 3. Hand reactive parameters for the Tai Chi Chuan (TCC) and control groups TCC
Control
p
Movement displacement (mm) Large target Medium target Small target p
405.2 ± 21.8 419.5 ± 24.1 423.2 ± 28.2 LS*
437.5 ± 22.6 439.5 ± 32.5 458.5 ± 36.0 LS*, MS*
0.008† 0.152 0.04*
Movement time (ms) Large target Medium target Small target p
630.0 ± 70.2 660.7 ± 77.8 678.5 ± 76.0 LM*, LS*
786.2 ± 82.8 824.0 ± 108.4 829.2 ± 128.2 NS
0.001† 0.003† 0.006†
Pause time (ms) Large target Medium target Small target p
102.5 ± 32.2 114.2 ± 33.5 131.7 ± 31.6 LS†, MS*
158.2 ± 25.6 184.5 ± 34.5 198.8 ± 33.8 LM*, LS*
0.002† 0.001† 0.001†
1109.5 ± 127.4 1134.5 ± 107.3 1142.1 ± 143.3 NS
982.5 ± 145.5 1033.1 ± 166.8 1054.0 ± 159.7 LM*, LS*
0.065 0.138 0.150
Peak velocity (mm/s) Large target Medium target Small target p
800
1500
700
1000 Velocity (mm/s)
Displacement (mm)
*p < 0.05; †p < 0.01. LS = comparison between large and small targets; MS = comparison between medium and small targets; LM = comparison between large and medium targets; NS = not significant.
600 500 400
500 0 −500
−1000 −1500
300 0
1
2
3 4 5 Time (sec)
6
7
0
1
2
3 4 5 Time (sec)
6
7
Figure 2. Sample displacement and velocity functions for a Tai Chi Chuan subject’s movement with a large target, indicating a relatively efficient movement.
were noted for all three target sizes in both groups, but there was no difference in peak velocity (Table 3).
Discussion Fitt’s Law implies an inverse relationship between the difference in a movement and the speed with J Formos Med Assoc | 2008 • Vol 107 • No 2
which it can be performed.19 Movement time varies with distance to be traveled and accuracy of the movement. It has also been reported that target size affects movement time.20 The test device used in this study was developed by our laboratory according to these concepts, because the conventional devices for eye-hand coordination could not measure these comprehensive parameters within one test. 107
Y.C. Pei, et al
1200 800
700
Velocity (mm/s)
Displacement (mm)
800
600 500 400 300
400 0 −400 −800
−1200
200 0
1
2
3
4
5 6 7 Time (sec)
8
0
9 10 11
1
2
3
4
5 6 7 8 Time (sec)
9 10 11 12
Figure 3. Sample displacement and velocity functions for a control subject’s movement with a large target, indicating a relatively inefficient movement.
B 16 14 12 10 8 6 4 2 0
TCC
Control
2 Prolonged acceleration
Skewness coefficient
Number of submovements
A
*
TCC
Control
† 1.5 1 0.5
Prolonged deceleration
Large target
Medium target
Small target
0
Large target
Medium target
Small target
Figure 4. (A) Number of submovements and (B) skewness coefficients for the three target sizes in the Tai Chi Chuan (TCC) and control groups. *p < 0.01; †p < 0.05.
Therefore, in this study, we used three different stroke target sizes (1 mm, 1.5 mm and 2 mm in diameter) in a random sequence of tests. Kinematic techniques enable the fluency and efficiency of movement to be quantified. The relationship between target size and the control of movement among the two groups were also indicated.22 Central mechanisms of the elderly have some deficits that affect the preparation of movement and control with visual guidance.20 A longer period of time is required to initiate the movement and to guide the movement in elderly compared to young people.19 A number of irregularities in the kinematics of movement have also been reported in older people.18 Systematic age differences in movement-to-target reaction times were found. The deleterious effects of age in eye-hand coordination and motor control of the upper extremities may reduce functional capacity, physical activity, and self care in the elderly. 108
In this study, significantly better results with regard to motor control of the upper extremities through eye-hand coordination were found in elderly TCC practioners compared to healthy and active non-TCC practitioners. A decrease in movement displacement, movement time and pause time, and an increase in SC were noted for all three target sizes in both groups, but there was no difference for peak velocity. Jacobson et al reported that a 12-week TCC program could increase participants’ shoulder kinesthetic sense at 60º.12 An 8-week TCC program also significantly reduces movement force variability in manual aim task.10 These might indicate that the deterioration in the stability and precision of movement of the upper extremities are delayed in elderly people who practice TCC. This may be due to TCC practitioners needing to perform spiral movements of the upper extremities with a push-pull motion J Formos Med Assoc | 2008 • Vol 107 • No 2
Effect of Tai Chi Chuan on eye-hand coordination
in coordination with squatting leg movements at a very low speed and with mental concentration. TCC also emphasizes that the eyes should follow the hand, thus enhancing eye-hand coordination. Previous studies have found that elderly people who regularly practice TCC show better postural stability in the more challenging conditions than those who do not (e.g. conditions with simultaneous disturbance of vision and proprioception).8,23–25 In Lan et al’s study, TCC was found to increase muscle strength, endurance and flexibility.7 Postural stability to anticipation depends on multi-muscle synergies including lower extremities, trunk and upper extremities.26 However, there has been no research to show that TCC could also improve the delicate motor control of the upper extremities.11,15 In this study, TCC practitioners demonstrated better results on both the precise motor control of hand and eye-hand coordination tests. Combined with our previous study that TCC practitioners also had better postural and balance control,4 it may be suggested that the motor control system of the upper extremities and that for balance share the same common neurologic pathways during the coordination exercise. Although the movements of TCC are slow and graceful, with low impact to the musculoskeletal system, TCC improves motor control and physical fitness, which is very important for the promotion of the activities of daily living and the prevention of falls in the elderly. Since the limitation of this study was its crosssectional investigation, we are in the midst of another longitudinal study to evaluate the motor control of elderly TCC practitioners from the beginning of TCC learning to long-term followup. The fitness and frequency of falls in all study and control subjects will be recorded for further investigation. It may reflect the effect of TCC on motor control of the upper extremities and postural balance in prevention of falls in the future. In addition to the general effect of exercise on fitness, TCC is a coordination exercise that involves the feet, legs, arms and trunk, with mental concentration. Our data suggest that elderly people J Formos Med Assoc | 2008 • Vol 107 • No 2
who regularly practice TCC show better eye-hand coordination and movement control of the upper extremities than those who do not, which might be of benefit in preventing deterioration in self care.
Acknowledgments This project was supported by research funding from the National Science Council of Taiwan (NSC 93-2314-B-182A-044).
References 1. King AC, Rejeski WJ, Buchner DM. Physical activity interventions targeting old adults. A critical review and recommendations. Am J Prev Med 1998;15:316–33. 2. Dempsey JA, Seals DR. Aging, exercise, and cardiopulmonary function. In: Lamb RR, ed. Perspectives in Exercise Science and Sports Medicine: Exercise in Older Adults. MI Copper Publishing Group, 1995;8:237–304. 3. China Sports. Simplified “Taijiquan”, 2nd edition. Beijing: China Publications Center, 1983:991–5. 4. Wong MK, Lai JC, Lan C. Investigation of the effect of Chinese shadow-boxing on physical performance. J Rehabil Med Assoc Taiwan 1990;18:92–8. 5. Tse SK, Bailey DM. T’ai chi and postural control in the well elderly. Am J Occup Ther 1992;46:295–300. 6. Wolf SL, Kutner NG, Green RC, et al. The Atlanta FICSIT study: two exercise interventions to reduce frailty in elders. J Am Geriatr Soc 1993;41:329–32. 7. Lan C, Lai JS, Wong MK, et al. Cardiorespiratory function, flexibility, and body composition among geriatric Tai Chi Chuan practitioners. Arch Phys Med Rehabil 1996;77: 612–6. 8. Wong AM, Lin YC, Chou SW, et al. Coordination exercise and postural stability in elderly people: effect of Tai Chi Chuan. Arch Phys Med Rehabil 2001;82:608–12. 9. Wolf SL, Barnhart HX, Ellison GL, et al. The effect of Tai Chi Quan and computerized balance training on postural stability in older subjects. Atlanta FICSIT Group. Frailty and injuries: cooperative studies on intervention techniques. Phys Ther 1997;77:371–81. 10. Hong Y, Li JX, Robinson PD. Balance control, flexibility, and cardiorespiratory fitness among older Tai Chi practitioners. Br J Sports Med 2000;34:29–34. 11. Lan C, Lai JS, Chen SY. Tai Chi Chuan: an ancient wisdom on exercise and health promotion. Sports Med 2002; 32:217–24. 12. Jacobson BH, Chen HC, Cashel C, et al. The effect of T’ai Chi Chuan training on balance, kinesthetic sense, and strength. Percept Mot Skills 1997;84:27–33.
109
Y.C. Pei, et al
13. Joyner MJ. Physiological limiting factors and distance running: influence of gender and age on record performances. Exerc Sport Sci Rev 1993;21:103–33. 14. Xu D, Hong Y, Li J, et al. Effect of Tai Chi exercise on proprioception of ankle and knee joints in old people. Br J Sports Med 2004;38:50–4. 15. Klein PJ, Adams WD. Comprehensive therapeutic benefits of Taigi—a critical review. Am J Phys Med Rehabil 2004; 83:735–45. 16. Warabi T, Noda H, Kato T. Effect of aging on sensorimotor functions of eye and hand movements. Exp Neurol 1986; 92:686–97. 17. Goggin NL, Stelmach GE. Age-related differences in the kinematic analysis of precued movements. Can J Aging 1990;9:371–85. 18. Morgan M, Phillips JG, Bradshaw JL, et al. Age-related motor slowness: simply strategic? J Gerontol 1994;49: 133–9. 19. Fitts PM. The information capacity of the human motor system in controlling the amplitude of movement. Exp Psychol 1992;121:262–9.
110
20. Welford AT, Norris AH, Shock NW. Speed and accuracy of movement and their changes with age. Acta Psychol (Amist) 1969;30:3–15. 21. Hogan N, Flash T. Moving gracefully: quantitative theories of motor coordination. Trend Neurosci 1987;10:170–4. 22. Bock O, Arnold K. Motor control prior to movement onset: preparatory mechanisms for pointing at visual targets. Exp Brain Res 1992;90:209–16. 23. Tsang WW, Wong VS, Fu SU, et al. Tai Chi improves standing balance control under reduced or conflicting sensory conditions. Arch Phys Med Rehabil 2004;85: 129–37. 24. Muller F, Stelmach GE. Prehension movements in Parkinson’s disease. Adv Psychol 1992;87:307–19. 25. Tsang WW, Hui-Chan CW. Standing balance after vestibular stimulation in Tai Chi practicing and non practicing healthy older adults. Arch Phys Med Rehabil 2006;87: 546–53. 26. Maciaszek J, Osinski W, Szeklicki R, et al. Effect of Tai Chi on body balance: randomized control trial in men with osteopenia or osteoporosis. Am J Chin Med 2007;35:1–9.
J Formos Med Assoc | 2008 • Vol 107 • No 2
Eye-hand Coordination of Elderly People Who Practice Tai Chi Chuan Yu-Cheng Pei,1 Shih-Wei Chou,1 Pay-Shih Lin,2 Yin-Chou Lin,1 Tony H.C. Hsu,1 Alice M.K. Wong1* Background/Purpose: The objective of this study was to evaluate the effect of motor control from Tai Chi Chuan (TCC) on eye-hand coordination in the elderly. Methods: Forty-two elderly people were recruited into this study. People in the TCC group (n = 22) had been practicing TCC regularly for more than 3 years. The control group (n = 20) comprised healthy and active elderly people. Subjects were asked to stroke target sensors in a test device with computer recording. There were three different target sensor sizes (1 cm, 1.5 cm and 2 cm in diameter) for different tests. For each target stroking, the following were recorded and calculated: start and end positions, duration of movement, pause time, peak velocity, and the time to reach peak velocity. Results: The TCC group showed significantly better results in decrease of displacement (p = 0.003), movement time (p = 0.002), pause time (p < 0.001), number of submovements (p = 0.001), and better skewness coefficients (p < 0.001) than the control group. However, the difference in the peak velocity of the TCC and control groups did not reach statistical significance (p = 0.026). Conclusion: The elderly TCC group had better results on the eye-hand coordination test than the control elderly group. [J Formos Med Assoc 2008;107(2):103–110] Key Words: elderly, eye-hand coordination, motor control, Tai Chi, Tai Chi Chuan
people. The basic TCC exercise is practiced in a semi-squat posture with a series of continual motions, similar to the push-pull of an invisible rival at a very slow speed. During the practice of TCC, diaphragmatic breathing and mental concentration with the eyes following the graceful movements of the upper extremities (such as cloud hand form) are emphasized. Shadow boxing is used to describe this unique exercise pattern.3 In recent years, TCC has gradually become a popular exercise in the Western world and investigations are flourishing. There is evidence to show that the practice of TCC leads to improvements
Quality of life in the elderly is closely related to their physical fitness. Recent studies have shown that supervised exercises for the elderly that emphasize aerobic, strength, flexibility and balance training can improve their fitness.1,2 There are few vigorous exercises that are suitable for older people due to the effects of wear and tear with aging, such as joint degeneration, poor eyesight or poor balance. Low-velocity and low-impact coordination exercises that are of low cost and easily accessible are more suitable for older people.1,2 Tai Chi Chuan (TCC) is a traditional Chinese coordination exercise that is suitable for older
©2008 Elsevier & Formosan Medical Association .
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1
Department of Physical Medicine and Rehabilitation, Chang Gung Memorial Hospital, and 2Department of Physical Therapy, Institute of Gerontology and Research Center, Chang Gung University, Taoyuan, Taiwan. Received: May 2, 2007 Revised: August 23, 2007 Accepted: October 2, 2007
J Formos Med Assoc | 2008 • Vol 107 • No 2
*Correspondence to: Dr Alice M.K. Wong, Department of Physical Medicine and Rehabilitation, Chang Gung Memorial Hospital, 5 Fu-Hsin Street, Kwei-Shan, Taoyuan 333, Taiwan. E-mail: [email protected]
103
Y.C. Pei, et al
Table 1. Demographic data of the Tai Chi Chuan (TCC) and control groups*
Sex (M/F) Age (yr) Body weight (kg) Body height (cm)
TCC (n = 22)
Control (n = 20)
p
8/14 67.8 ± 5.1 58.0 ± 5.1 156.6 ± 4.7
5/15 68.2 ± 5.2 56.8 ± 8.2 157.2 ± 4.4
0.420 0.845 0.403 0.620
*Data are presented as n or mean ± standard deviation.
in cardiovascular function, balance, flexibility, strength, kinesthetic senses and falls reduction.4–14 However, there are few reports that draw out the roles and benefits of motor control in the upper extremities, though TCC practitioners need delicate eye-hand coordination.15 Eye-hand coordination is essential to carry out daily activities and self care, especially in the elderly. They are insufficient to prepare their movement and have to control their movement through visual guidance.16 Elderly people generally need a longer time to initiate a movement and to guide their movements than young people.17,18 They are also more likely to stop and readjust their movements during what should be a smooth execution of movement.19 This study was therefore designed to investigate the performances of eye-hand coordination and motor control in the upper extremities of TCC practitioners, to determine whether or not TCC has beneficial effects.
Methods Subjects TCC subjects were recruited from a Tai Chi club and control subjects were recruited from volunteer groups at Chang Gung Memorial Hospital. All subjects were community dwellers and led an active lifestyle that consisted of regular exercise at least three times a week. None had a history of falls in the last 3 months. At the time of recruitment, TCC subjects had practiced TCC regularly for more than 3 years; they practiced TCC five to seven times a week for 1–2 hours each day according to the Yong style. 104
All subjects were healthy and examined by the same physician. Subjects who had a history of significant cardiovascular, pulmonary, metabolic, musculoskeletal (e.g. joint fracture, artificial joint replacement) or neurologic (e.g. stroke, Parkinson’s disease, dementia, poor vision) disease were excluded. Twenty-two TCC practitioners (8 men, 14 women; mean age, 67.8 ± 5.1 years) and 20 active non-TCC practitioners (5 men, 15 women; mean age, 68.2 ± 5.2 years) were recruited for this study. No significant differences were noted between groups with regard to sex, age, body weight and body height (Table 1).
Measurement equipment The test device was developed according to the concept of Fitts’ Law and Welford et al’s study.19,20 Figure 1A shows the test device and the arrangement of target sensors of various sizes that are embedded in the laboratory table during the repetitive hand function tests. Subjects were instructed to hold a pencil-like stick and asked to stroke the target sensors in a desired order with the stick (Figure 1B). The target sensors detected the sequence of strokes so as to calculate the movement time and to determine the accuracy of the movement sequences.
Procedure Before the experiment was begun, an explanatory statement and verbal explanation of what the task entailed were given to subjects. They were allowed to wear their glasses if needed. The experimenter also gave comprehensive demonstrations of how the task should be done. Preliminary practice at performing the task was permitted so J Formos Med Assoc | 2008 • Vol 107 • No 2
Effect of Tai Chi Chuan on eye-hand coordination
A
B 800
Z Y
700 Y axis
X
35
600 500 400
cm Marker
300 100
150
200
250
300
350
X axis Figure 1. (A) Set-up of a stroking hand movement projected on the horizontal plane. (B) The stroking movements are initiated at the left uppermost sensor to right uppermost sensor sequentially, and end at the left lowest sensor.
that subjects could familiarize themselves with the task. All subjects signed an informed consent form prior to participation. When the first task was presented, they were requested to adjust their sitting position with the adjustable chair to 90 degrees of hip and knee flexion with both feet on the ground. The table was also adjusted to elbow height (humerus and forearm in vertical position) during sitting position. Subjects were asked to perform at their fastest speed while stroking the center of each target in sequence along a route that was the shape of the letter “S” (Figure 1B). Twenty trials were completed at the fastest speed before the subject was presented with the next target arrangement. Total movement time was required to be within 10% of either side of the mean values determined from the pilot study. Trials were repeated only if accuracy was questionable or targets missing. The trial was excluded if the same target was stroked twice during the route or if targets were stroked out of sequence and not in accordance with the route. To test the intrasubject reliability of eyehand coordination parameters, each participant was repeatedly evaluated for each test condition 7–10 days later.
Data analysis In the first stage of the analysis, computer records of the timing of stroking the targets were identified at the beginning and end of each movement. J Formos Med Assoc | 2008 • Vol 107 • No 2
In the second stage, the features of interest were determined using automatic algorithms. Movement duration was based on the time spent in movement, and pause times were excluded. Stroked targets were determined from the computer records and each time the stick stroked the target was recorded. For each stroked target, the start and end positions, movement duration, pause time, peak velocity, time to reach peak velocity, and time to decelerate from peak velocity to zero were calculated. Pause time was defined as the time (ms) spent stationary at a target between two strokes (hypothesized to be an indication of the planning time between movements). Movement time was defined as the total time (ms) spent moving between targets in a trial, excluding all pause time. Movements were defined as the periods between points of zero velocity in the velocity profile, which correspond to the targets in the temporal profiles. While joining 11 targets should only require 10 movements, subjects occasionally made additional submovements between targets; these submovements were counted, analyzed separately, and then screened for further analysis. Subsequent analysis focused on the 10 primary movements, that is, the 10 movements with the greatest peak velocity (rather than any submovements). Features of interest in the velocity function of these selected movements were then entered into a database, where measures (of the time to peak 105
Y.C. Pei, et al
Table 2. Interclass correlation coefficients for each parameter Parameter Movement displacement Movement time Pause time Peak velocity
Large target
Medium target
Small target
0.820* 0.935* 0.880* 0.824*
0.836* 0.881* 0.876* 0.780*
0.808* 0.847* 0.833* 0.768*
*p < 0.05.
velocity and time from peak to zero velocity) were used to calculate a skewness coefficient (SC) that indicates the relative duration of the acceleration and deceleration phases of the movements. Submovements: the number of zero crossing in the velocity profile provides an indication of the number of submovements. The efficient performance of this stroking task requires only 10 movements, one for each stroke. The greater the number of submovements, the more inefficient the drawing strokes. The SC was used to measure the symmetry in movement control. An efficient movement (not involving terminal impact) minimizes jerk.21 The time to peak velocity relative to the time from peak to zero velocity was used as an index. A ratio greater than 1 suggests prolonged periods of acceleration and problems of force production, while a ratio < 1 indicates prolonged periods of deceleration and guidance.22,23 An efficient movement (not involving terminal impact) minimizes jerk and the ratio should be close to 1. Statistical analysis was performed using SPSS version 10.0 (SPSS Inc., Chicago, IL, USA). Interclass correlation coefficients (ICCs) were calculated for intrasubject reliability of eye-hand coordination parameters. Student’s t test was used to compare the differences in age, body weight, body height, and hand movement parameters between the TCC and control groups. Fisher’s exact test was used for sex distribution comparison. ANOVA for repeated measures (3 target sizes) was used to compare the hand movement parameters. Post hoc comparisons were made using the least significant difference test. Statistical significance was set at p < 0.05. 106
Results ICCs for the intrasubject reliability of eye-hand coordination parameters are shown in Table 2. All of the parameters, including movement displacement, movement time, pause time and peak velocity, were significantly reliable (p < 0.05). There were no significant differences with regard to age, sex, body weight and body height between the TCC and control groups. The hand reactive parameters in TCC and control subjects are shown in Table 3. The differences in movement displacement for large and small targets were significant between the two groups (p < 0.05), but the difference for mediumsized targets was not. For movement and pause times, there were significantly better results in the TCC group than in the control group for all three different target sizes (both p < 0.05). There were, however, no significant differences in peak velocity between the TCC and control groups for any of the three different target sizes. Overall, there were significant differences in movement displacement (p = 0.003), movement time (p = 0.002), pause time (p < 0.001) and peak velocity (p = 0.001) between the two groups. The significant differences in movement displacement and velocity between the two groups are illustrated in Figures 2 and 3. The comparison of submovements and skewness between the two groups are shown in Figure 4. There were significant differences in the number of submovements (p = 0.001) and SC (p < 0.001) between the two groups. A decrease in movement displacement, movement time and pause time, and an increase in SC J Formos Med Assoc | 2008 • Vol 107 • No 2
Effect of Tai Chi Chuan on eye-hand coordination
Table 3. Hand reactive parameters for the Tai Chi Chuan (TCC) and control groups TCC
Control
p
Movement displacement (mm) Large target Medium target Small target p
405.2 ± 21.8 419.5 ± 24.1 423.2 ± 28.2 LS*
437.5 ± 22.6 439.5 ± 32.5 458.5 ± 36.0 LS*, MS*
0.008† 0.152 0.04*
Movement time (ms) Large target Medium target Small target p
630.0 ± 70.2 660.7 ± 77.8 678.5 ± 76.0 LM*, LS*
786.2 ± 82.8 824.0 ± 108.4 829.2 ± 128.2 NS
0.001† 0.003† 0.006†
Pause time (ms) Large target Medium target Small target p
102.5 ± 32.2 114.2 ± 33.5 131.7 ± 31.6 LS†, MS*
158.2 ± 25.6 184.5 ± 34.5 198.8 ± 33.8 LM*, LS*
0.002† 0.001† 0.001†
1109.5 ± 127.4 1134.5 ± 107.3 1142.1 ± 143.3 NS
982.5 ± 145.5 1033.1 ± 166.8 1054.0 ± 159.7 LM*, LS*
0.065 0.138 0.150
Peak velocity (mm/s) Large target Medium target Small target p
800
1500
700
1000 Velocity (mm/s)
Displacement (mm)
*p < 0.05; †p < 0.01. LS = comparison between large and small targets; MS = comparison between medium and small targets; LM = comparison between large and medium targets; NS = not significant.
600 500 400
500 0 −500
−1000 −1500
300 0
1
2
3 4 5 Time (sec)
6
7
0
1
2
3 4 5 Time (sec)
6
7
Figure 2. Sample displacement and velocity functions for a Tai Chi Chuan subject’s movement with a large target, indicating a relatively efficient movement.
were noted for all three target sizes in both groups, but there was no difference in peak velocity (Table 3).
Discussion Fitt’s Law implies an inverse relationship between the difference in a movement and the speed with J Formos Med Assoc | 2008 • Vol 107 • No 2
which it can be performed.19 Movement time varies with distance to be traveled and accuracy of the movement. It has also been reported that target size affects movement time.20 The test device used in this study was developed by our laboratory according to these concepts, because the conventional devices for eye-hand coordination could not measure these comprehensive parameters within one test. 107
Y.C. Pei, et al
1200 800
700
Velocity (mm/s)
Displacement (mm)
800
600 500 400 300
400 0 −400 −800
−1200
200 0
1
2
3
4
5 6 7 Time (sec)
8
0
9 10 11
1
2
3
4
5 6 7 8 Time (sec)
9 10 11 12
Figure 3. Sample displacement and velocity functions for a control subject’s movement with a large target, indicating a relatively inefficient movement.
B 16 14 12 10 8 6 4 2 0
TCC
Control
2 Prolonged acceleration
Skewness coefficient
Number of submovements
A
*
TCC
Control
† 1.5 1 0.5
Prolonged deceleration
Large target
Medium target
Small target
0
Large target
Medium target
Small target
Figure 4. (A) Number of submovements and (B) skewness coefficients for the three target sizes in the Tai Chi Chuan (TCC) and control groups. *p < 0.01; †p < 0.05.
Therefore, in this study, we used three different stroke target sizes (1 mm, 1.5 mm and 2 mm in diameter) in a random sequence of tests. Kinematic techniques enable the fluency and efficiency of movement to be quantified. The relationship between target size and the control of movement among the two groups were also indicated.22 Central mechanisms of the elderly have some deficits that affect the preparation of movement and control with visual guidance.20 A longer period of time is required to initiate the movement and to guide the movement in elderly compared to young people.19 A number of irregularities in the kinematics of movement have also been reported in older people.18 Systematic age differences in movement-to-target reaction times were found. The deleterious effects of age in eye-hand coordination and motor control of the upper extremities may reduce functional capacity, physical activity, and self care in the elderly. 108
In this study, significantly better results with regard to motor control of the upper extremities through eye-hand coordination were found in elderly TCC practioners compared to healthy and active non-TCC practitioners. A decrease in movement displacement, movement time and pause time, and an increase in SC were noted for all three target sizes in both groups, but there was no difference for peak velocity. Jacobson et al reported that a 12-week TCC program could increase participants’ shoulder kinesthetic sense at 60º.12 An 8-week TCC program also significantly reduces movement force variability in manual aim task.10 These might indicate that the deterioration in the stability and precision of movement of the upper extremities are delayed in elderly people who practice TCC. This may be due to TCC practitioners needing to perform spiral movements of the upper extremities with a push-pull motion J Formos Med Assoc | 2008 • Vol 107 • No 2
Effect of Tai Chi Chuan on eye-hand coordination
in coordination with squatting leg movements at a very low speed and with mental concentration. TCC also emphasizes that the eyes should follow the hand, thus enhancing eye-hand coordination. Previous studies have found that elderly people who regularly practice TCC show better postural stability in the more challenging conditions than those who do not (e.g. conditions with simultaneous disturbance of vision and proprioception).8,23–25 In Lan et al’s study, TCC was found to increase muscle strength, endurance and flexibility.7 Postural stability to anticipation depends on multi-muscle synergies including lower extremities, trunk and upper extremities.26 However, there has been no research to show that TCC could also improve the delicate motor control of the upper extremities.11,15 In this study, TCC practitioners demonstrated better results on both the precise motor control of hand and eye-hand coordination tests. Combined with our previous study that TCC practitioners also had better postural and balance control,4 it may be suggested that the motor control system of the upper extremities and that for balance share the same common neurologic pathways during the coordination exercise. Although the movements of TCC are slow and graceful, with low impact to the musculoskeletal system, TCC improves motor control and physical fitness, which is very important for the promotion of the activities of daily living and the prevention of falls in the elderly. Since the limitation of this study was its crosssectional investigation, we are in the midst of another longitudinal study to evaluate the motor control of elderly TCC practitioners from the beginning of TCC learning to long-term followup. The fitness and frequency of falls in all study and control subjects will be recorded for further investigation. It may reflect the effect of TCC on motor control of the upper extremities and postural balance in prevention of falls in the future. In addition to the general effect of exercise on fitness, TCC is a coordination exercise that involves the feet, legs, arms and trunk, with mental concentration. Our data suggest that elderly people J Formos Med Assoc | 2008 • Vol 107 • No 2
who regularly practice TCC show better eye-hand coordination and movement control of the upper extremities than those who do not, which might be of benefit in preventing deterioration in self care.
Acknowledgments This project was supported by research funding from the National Science Council of Taiwan (NSC 93-2314-B-182A-044).
References 1. King AC, Rejeski WJ, Buchner DM. Physical activity interventions targeting old adults. A critical review and recommendations. Am J Prev Med 1998;15:316–33. 2. Dempsey JA, Seals DR. Aging, exercise, and cardiopulmonary function. In: Lamb RR, ed. Perspectives in Exercise Science and Sports Medicine: Exercise in Older Adults. MI Copper Publishing Group, 1995;8:237–304. 3. China Sports. Simplified “Taijiquan”, 2nd edition. Beijing: China Publications Center, 1983:991–5. 4. Wong MK, Lai JC, Lan C. Investigation of the effect of Chinese shadow-boxing on physical performance. J Rehabil Med Assoc Taiwan 1990;18:92–8. 5. Tse SK, Bailey DM. T’ai chi and postural control in the well elderly. Am J Occup Ther 1992;46:295–300. 6. Wolf SL, Kutner NG, Green RC, et al. The Atlanta FICSIT study: two exercise interventions to reduce frailty in elders. J Am Geriatr Soc 1993;41:329–32. 7. Lan C, Lai JS, Wong MK, et al. Cardiorespiratory function, flexibility, and body composition among geriatric Tai Chi Chuan practitioners. Arch Phys Med Rehabil 1996;77: 612–6. 8. Wong AM, Lin YC, Chou SW, et al. Coordination exercise and postural stability in elderly people: effect of Tai Chi Chuan. Arch Phys Med Rehabil 2001;82:608–12. 9. Wolf SL, Barnhart HX, Ellison GL, et al. The effect of Tai Chi Quan and computerized balance training on postural stability in older subjects. Atlanta FICSIT Group. Frailty and injuries: cooperative studies on intervention techniques. Phys Ther 1997;77:371–81. 10. Hong Y, Li JX, Robinson PD. Balance control, flexibility, and cardiorespiratory fitness among older Tai Chi practitioners. Br J Sports Med 2000;34:29–34. 11. Lan C, Lai JS, Chen SY. Tai Chi Chuan: an ancient wisdom on exercise and health promotion. Sports Med 2002; 32:217–24. 12. Jacobson BH, Chen HC, Cashel C, et al. The effect of T’ai Chi Chuan training on balance, kinesthetic sense, and strength. Percept Mot Skills 1997;84:27–33.
109
Y.C. Pei, et al
13. Joyner MJ. Physiological limiting factors and distance running: influence of gender and age on record performances. Exerc Sport Sci Rev 1993;21:103–33. 14. Xu D, Hong Y, Li J, et al. Effect of Tai Chi exercise on proprioception of ankle and knee joints in old people. Br J Sports Med 2004;38:50–4. 15. Klein PJ, Adams WD. Comprehensive therapeutic benefits of Taigi—a critical review. Am J Phys Med Rehabil 2004; 83:735–45. 16. Warabi T, Noda H, Kato T. Effect of aging on sensorimotor functions of eye and hand movements. Exp Neurol 1986; 92:686–97. 17. Goggin NL, Stelmach GE. Age-related differences in the kinematic analysis of precued movements. Can J Aging 1990;9:371–85. 18. Morgan M, Phillips JG, Bradshaw JL, et al. Age-related motor slowness: simply strategic? J Gerontol 1994;49: 133–9. 19. Fitts PM. The information capacity of the human motor system in controlling the amplitude of movement. Exp Psychol 1992;121:262–9.
110
20. Welford AT, Norris AH, Shock NW. Speed and accuracy of movement and their changes with age. Acta Psychol (Amist) 1969;30:3–15. 21. Hogan N, Flash T. Moving gracefully: quantitative theories of motor coordination. Trend Neurosci 1987;10:170–4. 22. Bock O, Arnold K. Motor control prior to movement onset: preparatory mechanisms for pointing at visual targets. Exp Brain Res 1992;90:209–16. 23. Tsang WW, Wong VS, Fu SU, et al. Tai Chi improves standing balance control under reduced or conflicting sensory conditions. Arch Phys Med Rehabil 2004;85: 129–37. 24. Muller F, Stelmach GE. Prehension movements in Parkinson’s disease. Adv Psychol 1992;87:307–19. 25. Tsang WW, Hui-Chan CW. Standing balance after vestibular stimulation in Tai Chi practicing and non practicing healthy older adults. Arch Phys Med Rehabil 2006;87: 546–53. 26. Maciaszek J, Osinski W, Szeklicki R, et al. Effect of Tai Chi on body balance: randomized control trial in men with osteopenia or osteoporosis. Am J Chin Med 2007;35:1–9.
J Formos Med Assoc | 2008 • Vol 107 • No 2