shows that the study participants were 63.0% women and 47.3% nonwhite, participants who were a mean (SD) age of 55.8 (8.7) years, had a body mass index of 34.9 (5.9), had HbA1c level of 7.7% (1.0%), and duration of diabetes of 7.1 (5.5) years. There were 97.3% taking diabetes medications with 18.3% taking insulin. Many participants had a history of comorbidities. Baseline systolic blood pressure and LDL cholesterol were well controlled, most likely because of the high percentage of patients taking medications.
Baseline Participant Characteristicsa
summarizes the exercise training data by month for individuals who met the per-protocol criteria. The aerobic and combination training groups performed their aerobic exercise at about 65% of maximum oxygen consumption. For both the aerobic and combination training groups the mean treadmill grade and METs progressively increased during the intervention period resulting in shorter exercise sessions over the course of the intervention. The total exercise dose ranged from 623.7 to 681.9 MET/min per week for the aerobic group and 532.0 to 572.8 MET/min per week in the combination training group. Taking into account the exercise intervention time and warm-up and cool-down time, we estimate that participants in the aerobic group typically spent mean 140 min/wk (range, 130-150 min/wk) on the treadmill, the resistance training group averaged 141 min/wk, and the combination training group spent a mean 110 min/wk (range, 100-120 min/wk) on the treadmill and between 30 and 40 min/wk lifting weights. There was no change in outside steps for any of the groups including the control group. The range in weekly steps for the control group was from 4180 to 4376. The mean change in kilocalories per day intake at follow-up was −93 (95% CI, −219 to 33) for the control, −162 (95% CI, −256 to −68) for the resistance training, −179 (95% CI−275 to −82) for the aerobic, and −127 (95% CI, −220 to −34) for the combination training groups, with no significant between-group differences.
Exercise Intervention Data for Individuals Who Met the Per-Protocol Criteria
depicts monthly HbA1c levels across the groups for the intention-to-treat and per-protocol analyses derived from a linear mixed model that included the covariates age, sex, race/ethnicity, diabetes duration, and baseline HbA1c. The group (P = .01) and month (P< .001) effects were statistically significant. Similar results were observed in the per-protocol analyses, which included all controls and only individuals in the exercise groups who obtained at least 70% adherence to their exercise prescription for at least 6 months.
Figure 2 Monthly Hemoglobin A1c Levels Monthly mean hemoglobin A1c (HbA1c) levels, derived from a mixed-linear model containing the covariates of age, sex, race/ethnicity, diabetes duration, and baseline HbA1c, are presented for group with the intention-to-treat (more ...)
summarizes results for baseline, follow-up and change in HbA1c across the groups. The absolute change in HbA1c in the combination training group vs the control group was −0.34% (95% CI, −0.64% to −0.03%; P=.03). In neither the resistance training (−0.16%, 95% CI, −0.46% to 0.15%; P=.32) nor the aerobic (−0.24%; 95% CI−0.55% to 0.07%; P=.14) groups were changes in HbA1c significant compared with those in the control group. In a subgroup analysis limited to participants with a baseline HbA1c 7.0% or higher, both the aerobic (−0.50%; 95% CI, −0.90% to −0.11%; P=.01) and combination training (−0.53%; 95% CI, −0.92% to −0.14%; P=.008) groups experienced significant reductions in HbA1c vs the control. In both analyses the intention-to-treat and per-protocol analyses produced similar results.
Baseline, Follow-up, and Change in Hemoglobin A1ca
summarizes results for fitness, strength, and body composition. The combination training group improved peak oxygen consumption per unit time compared with the control and the resistance training groups. All groups improved time on treadmill compared with the control group. Work per extension over 30 repetitions increased in the resistance training group compared with all other groups and in the combination training group compared with the control and aerobic groups. At follow-up, the combination training group had a decrease in mean weight compared with the control and resistance training group. Participants in the resistance training group had reduction in fat mass compared with the control, whereas the combination training group had a reduction in fat mass compared with the control and aerobic groups. The mean lean mass in the resistance training group increased compared with the aerobic group and combination groups. All exercise groups had reduction in waist circumferences compared with the control group. The findings from the per-protocol analysis closely matched the intent-to-treat analysis.
Change in Fitness, Body Composition, and Strength Variablesa
The prevalence of increases in hypoglycemic medications were 39% in the control, 32% in the resistance training, 22% in the aerobic, and 18% in the combination training groups with the Mantel-Haenszel test for linear association being significant (P=.005). The prevalence of decreases in hypoglycemic medications were 15% in the control, 22% in the resistance training, 19% in the aerobic, and 26% in the combination training groups (P=.20). The prevalence of individuals who achieved the composite outcome of either decreasing hypoglycemic medication or reducing HbA1c by 0.5% without increasing medications were 22% in the control group, 26% in the resistance training, 29% in the aerobic, and 41% in the combination training groups (Mantel-Haenszel χ2, P=.02). The odds ratio of achieving the composite outcome compared with the control group was 1.5 (95% CI, 0.6-3.8) for the resistance training, 1.8 (95% CI, 0.7-4.70) for the aerobic, and 2.9 (95% CI, 1.2-7.0) for the combination training groups.
Twenty-one events qualified as serious adverse events with the prevalence similar across groups (control, 3 events; resistance training, 8 events; aerobic, 6 events; and combination taring, 4 events). The nature of the adverse events was diverse and included diverticulitis, emergency hysterectomy, lung cancer, 5 cardiovascular disease events (all unrelated to intervention), blood clot, and others. No serious adverse event occurred during exercise training and only 1 was considered associated with exercise.