Emerging Treatments and Technologies B R I E F
R E P O R T
Mobility Impairment in Type 2 Diabetes Association with muscle power and effect of Tai Chi intervention RHONDA ORR, MEXSPSC1 TRACEY TSANG, BAPPSC(EXSPSC)(HONS)1 PAUL LAM, MBBS2
ELIZABETH COMINO, PHD3 MARIA FIATARONE SINGH, MD1,4
T
QOL in older adults (6 –13), it has never been tested specifically in a diabetic cohort for benefits across multiple domains. If Tai Chi was shown to be effective for mobility and other health outcomes relevant to this cohort, it may present a viable alternative exercise modality. The aim of this study was to examine the physiologic impairments associated with mobility in older adults with type 2 diabetes and to investigate whether Tai Chi would improve mobility in this cohort relative to sham exercise.
he increasing prevalence of type 2 diabetes is a major health concern. Reducing the vascular complications of diabetes has been a primary focus of treatment. However, the lessrecognized complications of physical disability, cognitive impairment, and depression that impact on quality of life (QOL) are also important primary care considerations in older patients with diabetes. Diabetes has been associated with a greater risk of decline in function and increased prospect of severe disability (1,2). Studies have sought to identify relationships or causal pathways between the syndromes of mobility, disability, and neuropsychological function in adults with type 2 diabetes (1,3). Few have simultaneously examined these factors potentially modifiable by physical activity (4) across multiple domains or at more than one point in time. The dose of aerobic and resistance exercise necessary to achieve metabolic benefits in clinical trials has sometimes led to poor compliance (5). Older adults with diabetes, often characterized by longterm sedentariness, overweight/obesity, and multiple comorbidities, may demonstrate better adherence to a low-intensity, low-impact exercise, such as Tai Chi. Although Tai Chi has demonstrated improved balance, gait speed, muscle strength, cardiorespiratory fitness, and
RESEARCH DESIGN AND METHODS — We conducted a 16week single-blind, randomized, shamexercise controlled trial with an intentionto-treat design. Baseline outcomes assessment was blinded. The study was approved by human research ethics committees of the Universities of Sydney and New South Wales. Written informed consent was obtained by participants. We studied 38 type 2 diabetic patients (79% female). We excluded patients who were physically active, institutionalized, or cognitively impaired (Mini-Mental State Examination ⱕ24) (14) or had arthritic pain, unstable conditions, or disease precluding them from the planned exercises. Participants were randomly allocated to the Tai Chi or control groups, named Eastern or Western exercise, both presented as being poten-
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From the 1Exercise and Sport Science Department, University of Sydney, Sydney, Australia; the 2Family Medicine Department, University of New South Wales, New South Wales, Australia; the 3Health Equity Training Research and Evaluation Department, University of New South Wales, New South Wales, Australia; and the 4University of Sydney, Sydney, Australia, and Hebrew SeniorLife and Jean Mayer USDA Human Nutrition Center on Aging, Tufts University, Boston, Massachusetts. Address correspondence and reprint requests to Rhonda Orr, P.O. Box 170, Lidcombe, NSW, 1825, Australia. E-mail:
[email protected]. Received for publication 1 June 2006 and accepted in revised form 7 June 2006. P.L. was the creator of the Tai Chi for Diabetes form and producer of its video and is the founder of Tai Chi Productions, which distributes these videos and similar products and services. Abbreviations: %BF, total body fat; QOL, quality of life. A table elsewhere in this issue shows conventional and Syste`me International (SI) units and conversion factors for many substances. DOI: 10.2337/dc06-1130 © 2006 by the American Diabetes Association. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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tially beneficial. The same exercise physiologist conducted both group exercise sessions (10 min warm-up and cooldown, 45 min exercise) twice weekly. The Tai Chi group performed Tai Chi for Diabetes (15), a 12-movement hybrid from Sun and Yang styles. Control subjects performed sham exercise (e.g., seated calisthenics, stretching) (16). All testing was conducted by the exercise physiologist before randomization and after completing 32 sessions (within 5 months of randomization). Mobility impairment was determined from measures of balance and gait speed (habitual and maximal). Static balance (timed single-leg stance with eyes open and closed), dynamic balance (3-m forward tandem walk), and balance index (summary score of static balance and postural control performance on a Chattecx balance platform) (17) were measured. Physiological capacity assessments included knee extensor strength (one repetition maximum), peak power, peak contraction velocity, and endurance (18) and overall exercise capacity (6-min walk) (19). Health status included number of comorbidities, body composition (waist circumference, total body fat [%BF]) (20), fasting blood glucose, cognition (14), QOL (21), and attitude toward diabetes (22). Statistical analyses were performed using Statview 5.0. Values are reported as means ⫾ SD or median (range). Groups were compared using t tests or 2. The effect of time and group-by-time interactions were analyzed with repeated-measures ANOVA. Variables, different between groups and their baseline values, were used as covariates in ANCOVA models. Relationships between variables of interest were analyzed with multiple and forward stepwise linear regression or Spearman rank-order correlation. Statistical significance was accepted at P ⱕ 0.05. RESULTS — Participant characteristics and performance data are presented in Table 1. Participants were obese (63%), displayed metabolic syndrome (82%), had one or more diabetes complications (40%), had comorbidities (predominantly osteoarthritis [84%] and hyperten-
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Orr and Associates
% change
Baseline
Follow-up
% change
Sham exercise (control) (n ⫽ 18)
Follow-up
Change over time P value
Group effect P value
0.3 0.7 0.9 0.2 0.2
Baseline
0.2 0.1 0.4 0.9 0.9
0.5 0.4 0.2 0.8 0.7 0.9
⫺0.1 ⫾ 1.9 ⫺1.0 ⫾ 2.8 0.4 ⫾ 2.8 ⫺3.2 ⫾ 20.4 9.0 ⫾ 5.9
0.03* 0.6 0.2 0.2 0.053 0.005¶
0.5 0.5 0.3 0.5 0.6
80.6 ⫾ 16.2 36.8 ⫾ 9.1 98.7 ⫾ 12.5 7.4 (5.4⫺15.4) 6.8 ⫾ 4.0
5.8 ⫾ 12.6 0 (⫺100 to 407) ⫺23.1 (⫺100 to 730) ⫺5.3 ⫾ 23.4 7.9 ⫾ 26.6 5.9 ⫾ 12.8
0.3 1.0 1.0 0.5 0.06
64.9 ⫾ 8.1 9.0 (0.7–50) 6.1 ⫾ 8.8 27 (23–30) 80.7 ⫾ 16.1 37.3 ⫾ 8.4 98.4 ⫾ 12.6 7.9 (5.6⫺13.9) 6.4 ⫾ 3.8
104.1 ⫾ 22.2 24.2 (0⫺30) 2.0 (0⫺8.3) 17.2 ⫾ 6.2 1.2 ⫾ 0.3 1.7 ⫾ 0.3 90.7 ⫾ 33.8 217.4 ⫾ 74.5 2.8 ⫾ 0.6 3 (0⫺14) 470.1 ⫾ 118.2
4.9 ⫾ 28.1 ⫺0.4 ⫾ 16.7 15.5 ⫾ 46.0 ⫺36.6 (⫺100 to 200) 3.6 ⫾ 8.2
⫺1.1 ⫾ 3.0 ⫺0.6 ⫾ 3.4 0.5 ⫾ 3.4 7.7 ⫾ 28.8 ⫺4.6 ⫾ 19.7
89.7 ⫾ 30.3 221.7 ⫾ 74.5 2.6 ⫾ 0.8 4 (2⫺11) 456.6 ⫾ 117.8
88.1 ⫾ 12.3 42.7 ⫾ 5.7 108.2 ⫾ 13.2 7.5 (5.7⫺12.5) 8.2 ⫾ 4.4
12.9 ⫾ 28.9 4.8 ⫾ 18.1 0.8 ⫾ 34.1 0 (⫺100 to 450) 1.7 ⫾ 7.4
65.9 ⫾ 7.4 8.5 (0–25) 6.9 ⫾ 6.7 28 (25–30) 87.5 ⫾ 13.7 43.0 ⫾ 4.8 106.1 ⫾ 14.6 7.6 (3.9⫺15.6) 7.5 ⫾ 4.0
97.8 ⫾ 24.8 220.9 ⫾ 64.9 2.6 ⫾ 0.7 5.5 (0⫺14) 481.8 ⫾ 83.0
111.5 ⫾ 22.2 30 (1.3⫺30) 2.2 (0.6⫺6.0) 18.5 ⫾ 6.3 1.1 ⫾ 0.2 1.6 ⫾ 0.3 91.3 ⫾ 31.5 215.9 ⫾ 75.4 2.7 ⫾ 0.8 4 (2⫺13) 474.0 ⫾ 76.1
111.1 ⫾ 23.1 107.3 ⫾ 23.1 2.5 ⫾ 14.9 8.96 (0.4⫺30) 17.9 (0.6⫺30) 47.7 (⫺79.2 to 3,473.2) 3.9 (0.4⫺19.6) 2.8 (0.1⫺14.0) ⫺22.6 (93.6 to 190.9) 19.1 ⫾ 7.0 18.1 ⫾ 8.3 ⫺4.7 ⫾ 27.6 1.0 ⫾ 0.2 1.1 ⫾ 0.2 12.3 ⫾ 27.4 1.6 ⫾ 0.3 1.7 ⫾ 0.3 6.6 ⫾ 10.3
Tai Chi (n ⫽17)
Table 1—Baseline characteristics of participants and outcomes after Tai Chi and sham exercise
Characteristic Age (years) Duration of diagnosed type 2 diabetes (years) Number of comorbidities Cognition (0–30)*† Weight (kg) %BF†‡ Waist circumference (cm)†‡ Blood glucose (mmol/l) Daily medications (n) Mobility Balance index (§) Single leg stance, eyes open (s) Single leg stance, eyes closed (s) Tandem walk score储 Habitual gait speed (m/s) Maximal gait speed (m/s) Physiological capacity Muscle strength (nmol/l) Peak muscle power (W) Peak muscle velocity (rad/s) Muscle endurance (number of repetitions) 6-min walk distance (m)
CONCLUSIONS — We report for the first time the novel and robust relationships between muscle power and contraction velocity and mobility impairment in type 2 diabetes. Muscle contraction velocity was the single characteristic independently associated with poorer balance and gait in this cohort. After 4 months, Tai Chi provided modest significant improvements in mobility, although not different from sham exercise. The dose and/or movements of the Tai Chi for Diabetes program may not have been sufficient to elicit robust adaptations. Furthermore, the high prevalence of obesity and osteoarthritis may have compromised an optimal training style.
Values of normally distributed data are means ⫾ SD. Non–normally distributed data are median (range). *Cognition was assessed by the Mini-Mental State Examination, which uses a scale of 0-30, with scores ⬍24 indicating cognitive impairment (14). †Significant difference between groups at baseline (P ⫽ 0.02– 0.04). ‡%BF was determined using bioelectrical impedance analysis (20). §Balance index: a lower score indicates better overall balance performance (17). 储Tandem walk score equals time to complete course plus number of errors made during the test; a lower score indicates better balance. ¶P values were determined by factorial ANOVA. A P value of ⬍0.05 was accepted as statistically significant.
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sion [76%]), and were recurrent fallers (16%; two or more falls in the past year). At baseline, older age, more comorbidities, higher %BF, poorer cognition, QOL, exercise capacity and muscle power, and slower gait speed and muscle contraction velocity were related to poor balance (P ⫽ 0.043 to ⬍0.0001). Similarly, older age, poorer QOL, exercise capacity, balance and muscle power, and slower muscle contraction velocity were related to slower gait speed (P ⫽ 0.043 to ⬍0.0001). Forward stepwise regression models revealed that slower muscle contraction velocity was the sole common independent contributor to both balance and gait impairment at baseline. Balance (P ⫽ 0.03) and maximal gait speed (P ⫽ 0.005) improved significantly over time, but there were no group-bytime interactions. Habitual gait speed (P ⫽ 0.053) and 6-min walk (P ⫽ 0.06) showed a trend toward improvement over time. Physiological and health status did not significantly change after the intervention. Participants with poorer QOL improved balance the most (P ⫽ 0.023). By contrast, increased maximal gait speed was associated with better baseline health, muscle function, and exercise capacity. Following stepwise regression, lower baseline blood glucose and %BF independently predicted improved maximal gait speed (r ⫽ 0.71, P ⫽ 0.0001), accounting for 65% of the variance. Improvements in balance index (r ⫽ 0.34, P ⫽ 0.047) and gait speed (maximal gait speed: r ⫽ 0.46, P ⫽ 0.008; habitual gait speed: r ⫽ 0.44, P ⫽ 0.011) were significantly correlated with compliance but neither were related to each other (P ⫽ 0.90) nor could they be explained by changes in physiological or health status.
Diabetes: mobility impairment and Tai Chi Enhanced balance and gait speed were not related to each other. Compliance, however, was related to improved mobility, suggesting that the observed improvements cannot be solely considered a learning effect. Unmeasured aspects of group participation, such as changes in motor control, socialization, or neuropsychological function, may explain our results. In conclusion, mobility impairments in an older, obese cohort with type 2 diabetes are associated with low muscle power and may therefore respond more robustly to an exercise intervention specifically designed to improve muscle contraction velocity, such as explosive resistance (power) training. Acknowledgments — We thank Douglass Hanly Moir Pathology for their sponsorship, Keiser Sports Health for their donation of K400 Electronics for pneumatic-resistance machines, and the participants for their dedication.
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