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Effects of Long-Term Resistive Training on Mobility and Strength

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									Journal of Gerontology: MEDICAL SCIENCES                                                                                                             In the Public Domain
2003, Vol. 58A, No. 8, 740–745




       Effects of Long-Term Resistive Training on Mobility
           and Strength in Older Adults With Diabetes
               L. Jerome Brandon,1,2,3 Debbi A. Gaasch,1 Lisa W. Boyette,1 and Adrienne M. Lloyd1

                     1
                         Rehabilitation Research and Development Center, Veteran Affairs Medical Center, Decatur, Georgia.
                                       2
                                        Department of Kinesiology and Health, Georgia State University, Atlanta.
                                     3
                                      Department of Rehabilitation Medicine, Emory University, Atlanta, Georgia.


                      Background. Strength training has been shown to be beneficial in older adults. However, very little data exist on the
                   effects of strength training in older diabetics.

                     Methods. 31 community-dwelling older adults with diabetes (mean age ¼ 66.1 years) were randomly assigned to either
                   an exercise (EX) or control (CO) group. The EX group trained the plantar flexors, knee extensors, knee flexors, hip
                   extensors, and hip flexors muscle groups at 50%, 60%, and 70% of 1-repetition maximum, 2.6 days a week, for 24
                   months. Mobility tests included the timed up and go, 50-foot walk, and walking up and down 8 stairs. Strength and
                   mobility for both groups were evaluated at 6-month intervals.

                      Results. There was a group and time effect as the EX group increased 31.4% ( p , .001) in strength for all muscle
                   groups after the first 6 months of training, and the strength gains were retained for the duration of the training intervention.
                   There was also a group and time effect for mobility as performance increased 8.6% and 9.8% ( p ¼ .032 and p ¼ 0.031) for
                   the first 6 and 12 months, respectively, but decreased to 4.6% above baseline at the end of the intervention. There were
                   essentially no changes from baseline strength or mobility values for the CO group.

                      Conclusion. In conclusion, these data suggest that a moderate-intensity resistive-training program can improve
                   mobility and strength for the duration of a 24-month intervention in older adults with diabetes, thus potentially reducing
                   the rate of mobility loss during aging.




O     LDER adults with diabetes (especially type 2) have
      greater body weight (subcutaneous fat deposits), re-
duced muscular insulin sensitivity, altered thermogenesis,
                                                                                     and strength of the exercise (EX) group would increase
                                                                                     significantly when compared with a control (CO) group, and
                                                                                     the increases would last for the duration of the training.
and decreased peripheral neurological, muscular, and cir-
culatory functions (1–4). Andersen and colleagues (5) con-                           METHODS
cluded that diabetics experience up to 50% muscle weakness
compared with nondiabetics in knee extension and plantar                             Research Design and Subjects
flexion strength due to diabetes-related neuropathy. These                               A randomized repeated-measures controlled trial with 2
lower-extremity muscle groups are highly associated with                             groups (EX and CO) was used in this study. Subjects were
mobility and have the added issue of age-related decreases                           recruited from a Veterans Affairs Diabetic Clinic, a comput-
in older adults with diabetes, which results in greater frailty                      erized research center database, local diabetic clinics and
and falls incidence (6–8). Since older diabetics have altered                        senior centers, and by word of mouth, where participants
muscular function and excess fat weight that has to be sup-                          told friends of the study. Between 15% and 28% of the
ported and transported, they have a greater strength need than                       subjects were recruited from each site. Fifty-two of 442
nondiabetic older adults (6,9–11).                                                   (11.8%) of the older community-dwelling adults with
   Strength training has been reported as a safe and effective                       diabetes contacted to participate in this study volunteered
countermeasure to sarcopenia and age-related strength                                as subjects; however, 16 EX and 15 CO (mean 66.1 years)
decrements in older adults (1,3,12). Most existing strength-                         completed all assessments and are included in the analyses
training studies with older adults were designed to investi-                         (see Table 1). Many were involved in community activities
gate the effects of short duration (12 months or less) training                      such as various clubs, and walking, but were not actively
interventions and did not consider the effects of long-term                          involved in exercise programs. All of the volunteers were
strength training on mobility in older adults with diabetes                          taking either oral hypoglycemic medication or insulin.
(12–15). While some studies indicate that strength training                          Preexercise session blood glucose mean values ranged from
can increase strength and mobility in older adults (16,17),                          135 to 153 ml/dL and postexercise blood glucose means
the nature and duration of the training benefits need further                         ranges from 85 to 95 ml/dL during the 24-month training
clarification, and this is especially true for older adults                           intervention. Based on self-report, mild peripheral neurop-
with diabetes (14). This study was designed to determine                             athies were present in 12 of the EX group and 9 of the CO
the nature and duration of mobility and strength benefits                             group. Institutional human subject approval was obtained
associated with a 24-month strength-training intervention in                         for the study. All subjects signed informed consent forms,
older diabetics. The hypothesis evaluated was that mobility                          and obtained physician approval to participate in the study.

740
                                                MOBILITY AND STRENGTH IN OLDER DIABETICS                                                     741



        Table 1. Subject Recruitment, Screening, and Dropouts                       muscle groups trained and tested in this study. The CO
Recruitment
                                                                                    group was evaluated for strength at baseline and at 6-month
(Reasons typically given for not volunteering                         Diabetics     intervals during the intervention.
   to participate in the study)                                     Contacted (%)      The mobility tests in this study were modified from
Not interested in study                                                     57
                                                                                    validated procedures in the literature and include the timed
Unwilling to make a 2-year commitment                                       21      up and go (TUG), 50-foot walk (walk), and walking up
Cardiovascular-related diseases, or believed that                                   (upstairs), and down (downstairs) 8 stairs (12,21,22). The
   exercise would not be good for them                                      10      TUG required the subject to rise from a chair, walk around
Had medical conditions or were taking medications                                   a cone 10 feet away, walk, back to the chair, and sit. The
   where exercise would have been contraindicative                                  walk test required the subjects to walk quickly and com-
   for them                                                                  6
Other reasons                                                                6
                                                                                    fortably 25 feet, turn, and walk back to the start. Upstairs
                                                                                    required the subjects to walk up a flight of 8 stairs carrying
Screening
                                                                                    a 2.3-kg weight, and downstairs required the subjects to
(8 subjects were excluded during screening;
   reasons listed below)                                              Number
                                                                                    walk down a flight of 8 stairs with a 2.3-kg weight. The
                                                                                    subjects were requested to perform the tasks quickly, but
Elevated blood glucose                                                       2
                                                                                    safely, as scoring was based on the time required to perform
Myocardial infarctions within the last 12 months                             2
Severe peripheral neuropathy                                                 1      the tasks.
Uncontrolled hypertension                                                    1         Procedures recommended by Lohman and colleagues (23)
Depression                                                                   1      were used to measure circumferences and skinfolds. Body
Altered cognition                                                            1      composition was estimated from skinfolds, as Jackson and
                                               Dropouts                             colleagues’ (24,25) equations were used to estimate body
                           Exercisers                         Comparisons
                                                                                    fat. The relationship between thigh skinfolds and thigh cir-
                                                                                    cumferences was used to estimate changes in muscle mass
                 Initial N ¼ 29 Final N ¼ 16 Initial N ¼ 23 Final N ¼ 15
                                                                                    during the 24-month training intervention.
Test Period         Dropouts         (%)        Dropouts         (%)
6 months               6                20.7              4             17.4
12 months              6                20.7              1              4.3
18 months              1                 3.4              2              8.7
                                                                                    Intervention
24 months              0                 0.0              1              4.3           To minimize injury risks, constant supervision, emer-
Total dropouts        13                44.8              8             34.7
                                                                                    gency equipment, and personnel were available during
                                                                                    the testing and training. The training sessions were held
                                                                                    Monday, Wednesday, and Friday during the first 6 months.
  Exclusion criteria included elevated blood glucose (.300                          After the first 6 months, the subjects were required to attend
mg/dL), depression (Beck’s Depression scale score .17)                              twice a week, but were allowed to attend all 3 sessions. Each
(18), altered cognitive function (Mini-Mental State Exam-                           subject was required to attend a minimum of 70% of the
ination score ,24) (19), and cardiovascular diseases, symp-                         training sessions (based on 3 days a week the first 6 months
toms, or risks, including myocardial infarctions, congestive                        and 2 days a week after the first 6 months) to be included in
heart failure, strokes, hypertension (SBP [systolic blood                           the data analyses.
pressure] 140 and DBP [diastolic blood pressure] 90),                                Strength training was completed on an 11-station Nautilus
and atherosclerosis (20) (see Table 1 for the number of                             machine. The subjects completed 3 sets of 8–12 repetitions
exclusions).                                                                        per exercise. The intensity was 50%, 60%, and 70% for sets
  Power calculations were based on mean strength and                                1, 2, and 3, respectively. Each 1-hour session consisted of
mobility values from a previously published study (12). A                           50 minutes of strength-training exercises and 10 minutes
power greater than 0.80 was obtained in this study, as 15                           of warm-up, flexibility, and cool-down exercises. Pre- and
subjects per cell provides a power of 0.81 with a sensitivity                       postexercise blood glucose levels were measured to ensure
of 1 standard deviation at an alpha level of 0.05.                                  appropriate response before and after exercise sessions.
                                                                                    Resting and recovery heart rates and blood pressures were
Strength and Mobility Testing                                                       measured each session to ensure appropriate physiological
   Strength was assessed by 1-repetition maximums (1RMs)                            responses to exercise. For safety reasons, if a participant’s
on 5 Nautilus (Atlanta, GA) stations and reported as relative                       blood pressure was above either 200 mmHg systolic or
strength (1RM/BW ¼ 1RM in kg divided by body weight in                              100 mmHg diastolic (20), the individual was not allowed
kg) (17). During the strength assessments, 1.1 and 2.3 kg                           to exercise that session unless the pressure dropped below
add-on weights were used to increase the accuracy of the                            these values after a 30-minute rest. This occurred in 8 EX
assessment. Strap-down belts were used to stabilize the hip                         subjects during the 24-month training intervention.
area and enhance hip flexion and extension assessments.
Strength and mobility of the EX group were evaluated every
6 months during the 24-month intervention. The 6-month                              Analyses
assessments were used to update training prescriptions and                            Means and standard deviations were calculated on all
for the analyses in this study. Plantar flexors, knee exten-                         of the data. To evaluate overall lower body strength and
sors, and flexors (lower extremity—legs measured simulta-                            mobility, composite strength and mobility (means of the
neously), and hip flexors and extensors (trunk) were the                             individual strength and mobility variables, respectively)
742                                                                       BRANDON ET AL.



                                        Table 2. Baseline Physical Characteristics of the Subjects Based on Gender
                                       Males                                                Females                                                         Total
                      EX N ¼ 11                       CO ¼ 10                EX N ¼ 5                    CO N ¼ 5                       EX N ¼ 16                     CO N ¼ 15
Variable             X           SD               X             SD           X           SD            X                SD             X             SD              X           SD
Age (y)              65.7        7.5             65.9           7.5        66.7        7.9             66.9             5.6            65.8           7.6            66.3         6.8
Height (cm)         176.1        9.0            172.2           6.1       163.2*       6.4            159.3             5.4           171.5           8.1           168.1         5.4
Weight (kg)          97.2       18.1             93.7          21.3        76.3*      13.0             80.3            14.6            89.9          16.3            88.8        19.9
   Note: *Group means different at p , .01 based on gender. EX ¼ exercisers; CO ¼ controls; X ¼ mean; SD ¼ standard deviation.



were calculated. Percent change was computed from the                                      illness; their spouse became ill and they had to care for
means. Mobility and strength responses were evaluated for                                  them; or they relocated to another city.
differences between the EX and CO groups over time using                                      There were no differences in baseline physical character-
repeated measures analysis of variance (ANOVA) and                                         istics between the EX and CO groups (Table 2). The thigh
       ´
Scheffe post hoc tests. Subjects with complete data sets for                               circumferences of the EX subjects did not change over time,
a test period were included in data analyses. Variables with                               but thigh skinfold thickness decreased at 24 months ( p ¼
missing values were omitted from analyses.                                                 .045; Table 3). This suggests that the thigh muscle mass of
                                                                                           the EX subjects increased during training, but there were no
RESULTS                                                                                    changes for the CO subjects.
   There was over an 85% training and retesting adherence                                     Since the training response patterns were similar for both
rate for the EX subjects and a similar retesting rate for                                  absolute (1RM) and relative (1RM/BW) strength, and
the CO subjects included in the data analyses. There was                                   support of body weight is important for mobility tasks,
a cumulative 45% and 35% dropout rate among the EX                                         1RM/BW values were used in this study. Relative strength
and CO subjects, respectively, over the 24-month study                                     expressions normalized the data for body weight, as baseline
(Table 1), but baseline individual and composite strength                                  strength values for the EX and CO groups were not different
and mobility were not different between the completers                                     for any of the variables, except the CO group had higher hip
and dropouts. These were relatively high dropout rates, but                                flexor values. Repeated measures ANOVA analyses re-
appeared to reflect the difficulty of getting diabetics com-                                 vealed significant ( p . .001) group and time effects for all
mitted to long-term exercise programs. Reasons for drop-                                                                       ´
                                                                                           individual muscle groups. Scheffe post hoc tests showed
ping out of the study: the study required too much time;                                   that the EX group experienced a significant increase
their disease got worse or they experienced some other                                     (average of 31.4%; Figures 1A and B) in trunk and lower

           Table 3. Mobility and Relative Strength Responses of Older Diabetic Adults During a 24-Month Resistive-Training Intervention
                                                             Exercisers (N ¼ 16)                                                           Controls (N ¼15)
                                           Baseline               6 Months           24 Months                      Baseline                  6 Months                   24 Months
Variable (kg)                          X              SD         X        SD         X          SD              X              SD             X           SD           X         SD
Body composition
   Weight (kg)                    89.9a           16.3         90.3a     18.3      90.6a       20.6           88.8a           19.9       88.5a         13.7         87.0a       17.6
   Body fat (%)                   34.7a            5.8         32.9a      6.1      32.4a        6.3           33.2a            7.2       33.2a          8.2         31.3a        8.2
   Thigh skinfolds (cm)           24.5a           10.5         23.1a     12.3      19.6b        8.7           20.9a           10.7       20.6a          9.6         21.5a       12.9
   Thigh circumference (cm)       52.5a            4.9         52.4a      4.2      51.7a        3.3           51.5a            4.3       50.8a          4.9         50.4a        3.9
Trunk
   Hip flexors                      0.32a*             0.08      0.39b     0.12      0.44b       0.12           0.37a*          0.11        0.39a          0.11       0.38a       0.07
   Hip extensors                   0.58a              0.17      0.77b     0.26      0.86b       0.31           0.60a           0.19        0.66a,b        0.14       0.68a,b     0.17
Lower extremities
   Knee extensors                  0.58a              0.22      0.79b     0.32      0.81b       0.29           0.57a           0.15        0.60a          0.16       0.63a       0.15
   Knee flexors                     0.40a              0.11      0.53b     0.16      0.35b       0.32           0.39a           0.08        0.40a          0.07       0.41a       0.09
   Plantar flexors                  0.63a              0.18      0.84b     0.30      0.83b       0.37           0.69a           0.19        0.68a          0.16       0.72a       0.16
Mobility tasks
   Timed up and go                 8.2a               2.1       8.0a      2.5       7.6a        1.8            8.1a            2.2        7.4a            1.4        8.3a        1.0
   Walk                           12.4a               2.6      11.8a      2.8      12.7a        2.6           12.4a            3.0       11.9a            2.3       13.0a        2.2
   Upstairs                        6.1a               1.9       5.8a      1.9       5.9a        1.0            5.4a            1.1        5.2a            0.9        5.7a        1.3
   Downstairs                      5.7a               3.2       5.2c      1.7       5.5a        1.5            4.9a            1.0        5.0a            1.5        5.8b        2.4
    Notes: Strength means within groups that have different letters (for examplea,b,c) are different at p , .001. When a mean has 2 letters(a,b), then that mean is
not different from other within-group means with the same letters. *Baseline hip strength for the Exercise and Control groups are different at p , .01. Mobility
mean different from baseline mean at p , .001b, p ¼ .031c. Timed up and go ¼ time required to rise from a chair walk 10 feet and walk back; Walk ¼ time re-
quired to walk 50 feet; Upstairs ¼ time required to walk up a flight of 8 stairs carrying a 2.3-kg weight; Downstairs ¼ time required to walk down 8 stairs with
a 2.3-kg weight. X ¼ mean; SD ¼ standard deviation.
                                               MOBILITY AND STRENGTH IN OLDER DIABETICS                                                                         743




                                                                                        Figure 2. A, Percent change in composite strength during the 24-month
                                                                                     training intervention. Composite strength is the mean of hip flexors, hip
   Figure 1. A, Changes in trunk strength (kg/body weight in kg) during 24           extensors, knee extensors, knee flexors, and plantar flexors muscle groups. There
months of resistive training for older adults with diabetes. Trunk is the mean of    was a significant group and time effect as exercise percent change in strength
hip flexors and hip extensors. Strength values for months 6 through 24 are            was greater than baseline and control strength at p , .001 from months 6
different than baseline at p , .001, but are not different from each other. B,       through 24. B, Percent change in mobility during the 24-month training
Changes in lower extremity strength (kg/body weight in kg) during 24 months of       intervention. Mobility is the average time required to complete the walk, timed
resistive training for older adults with diabetes. Lower extremity strength is the   up and go, upstairs, and downstairs tests. There was a significant group and time
average of knee extensors, knee flexors, and plantar flexion. Strength values for      effect as exercise changes in mobility were greater than baseline and control
months 6 through 24 are different than baseline at p , .001, but are not different   mobility ( p , .01) at months 6 and 12.
from each other.

                                                                                     intervention. Based on post hoc assessments, the mobility
                                                                                     task performance of the EX subjects improved 8.6% at
extremity strength following the first 6 months of training,                          6 months ( p ¼ .032) and 9.8% at 12 months ( p ¼ .031), and
and the increased strength was maintained for the duration                           was significantly better than the CO group during these time
of the 24-month training intervention (Table 3). For the CO                          periods. Mobility performance declined gradually for the
group, there was no change from baseline in 1RM strength                             remainder of the training intervention, but remained 4.6%
for any of the muscle groups, except hip flexors strength was                         above baseline and 8.2% better than the CO group at the
higher than baseline at 18 months.                                                   conclusion of training. The CO group mobility had de-
   The only individual mobility test with a significant time                          creased to 3.6% below baseline (Figure 2B).
and group effect was downstairs. Downstairs mobility
performance improved ( p ¼ .031) only at 6 months for
the EX group. There was a trend toward improvement for                               DISCUSSION
upstairs, TUG, and the walk test for the EX group. There                                Results from this study demonstrate that a 24-month
were no changes for any of the individual mobility tasks for                         moderate-intensity resistive-training intervention improves
the CO group, except downstairs performance was poorer                               strength and mobility in older adults with diabetes for the
( p ¼ .034) at 24 months compared with baseline (Table 3).                           duration of the training intervention. The response patterns for
   Repeated measures ANOVAs showed significant time                                   mobility and strength in this study were different from each
and group effects in percent change for composite strength                           other, but relatively similar to respective patterns observed
and mobility. The illustration in Figure 2A shows that                               elsewhere (26,27,28). In a 5-year community based study that
strength for the EX subjects increased 31.4% following the                           included strength training, the authors reported that strength
first 6 months of training, and remained between 36% and                              increased during the first 12 months and stabilized from 12 to
39% above baseline and was significantly greater than                                 24 months. Physical performance in the 5-year study
the CO group ( p , .001) for the duration of the training                            increased the first 2 to 3 years, and declined gradually until
744                                                    BRANDON ET AL.



the conclusion of the study (28). Strength in the present study    ACKNOWLEDGMENTS
increased during the first 6 months, stabilized, and remained         Contract project number E721-4RA from the VA Medical Rehabilitation
constant at the elevated level for the remaining 18 months.        Research and Development supported this study. Special thanks to Dr. Joe
                                                                   Ouslander for his insightful review of this manuscript.
Mobility increased during the initial 6 months in the present
study and remained above baseline, although it declined from         Address Correspondence to L. Jerome Brandon, PhD, Department of
                                                                   Kinesiology and Health, Georgia State University, Atlanta, GA 30303.
12 months until the end of the study.                              E-mail: hprljb@langate.gsu.edu
   Compared with other studies in the literature, the baseline
strength of the muscle groups in this study indicates that the
subjects had relatively good muscular fitness (12). In this study
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