Relation between risk of falling and postural sway complexity in diabetes.

For older individuals with diabetes, any decline in balance control can be especially problematic since it is often a precursor to an increased risk of falling. This study was designed to evaluate differences in postural motion dynamics and falls risk for older individuals with type 2 diabetes (T2DM) classified as fallers/non-fallers and, to assess what impact exercise has on balance and falls risk. The results demonstrated that the risk of falling is greater for those older individuals with multiple risk factors including diabetes and a previous falls history. The postural motion features of the high-risk individuals (T2DM-fallers) were also different, being characterized by increased variability and complexity, increased AP-ML coupling, less overall COP motion and increased velocity. One suggestion is that these individuals evoked a stiffening strategy during the more challenging postural tasks. Following training, a decline in falls risk was observed for all groups, with this effect being most pronounced for the T2DM-fallers. Interestingly, the COP motion of this group became more similar to controls, exhibiting decreased complexity and variability, and decreased velocity. The reciprocal changes in COP complexity support the broader view that age/disease-related changes in physiological complexity are bi-directional. Overall, these results show that, even for older T2DM individuals at greater risk of falling, targeted interventions can positively enhance their postural dynamics. Further, the finding that the pattern of postural motion variability and complexity was altered highlights that a decline in physiological complexity may not always be negatively associated with aging and/or disease.

Use of clinical practice recommendations for exercise by individuals with type 1 diabetes.

PURPOSE: The purposes of this study were to determine the extent to which physically active individuals with type 1 diabetes actually follow exercise recommendations and to compare their use of current with previous recommendations. METHODS: A questionnaire was developed consisting of the American Diabetes Association's current clinical practice recommendations for exercise and some previous recommendations. The questionnaire was mailed to approximately 1700 members of the International Diabetic Athletes Association; responses from 238 questionnaires were included in the results. Respondents indicated to what extent they currently use all of these recommendations and any modifications that they employ. RESULTS: The responses indicated that individuals with type 1 diabetes closely followed the majority of the current clinical exercise recommendations and did so to a greater extent than previous ones. Individuals' specific modifications to the current recommendations are summarized. CONCLUSIONS: The current clinical practice recommendations are used by exercisers with diabetes and are followed more closely than previous ones. The significant number of reported modifications made by individuals indicates, however, that a substantial need still exists to modify and individualize the recommendations.

Exercise and diabetes control: a winning combination.

It is becoming evident that in many individuals, diabetes of all types can be precipitated or exacerbated by inactivity. Exercise is a cornerstone in diabetes management and conveys many health benefits. Different forms of exercise can have varying effects on the blood sugar response, especially in individuals using insulin. Appropriate exercise for effective management of blood sugar levels and published clinical exercise recommendations for individuals with type 1 and type 2 diabetes include additional blood glucose monitoring, modified insulin doses, and supplemental carbohydrate intake. Physicians who treat exercising patients with diabetes should tailor programs to meet individual requirements.

Utilization of glycogen but not plasma glucose is reduced in individuals with NIDDM during mild-intensity exercise.

To test the hypothesis that substrate utilization during mild-intensity exercise differs in non-insulin-dependent diabetes mellitus (NIDDM) compared with nondiabetic subjects, seven lean healthy subjects (L), seven obese healthy subjects (O), and seven individuals with NIDDM were studied during 40 min of mild-intensity cycling (40% of peak O2 uptake). Systemic utilization of plasma glucose (Glc Rd) was determined by using isotope dilution methods. Gas exchange was measured to determine rates of carbohydrate (CHO) and lipid oxidation. During exercise, when CHO oxidation was greater than Glc Rd, the net oxidation of glycogen was calculated as the difference: CHO oxidation - Glc Rd. During mild-intensity cycling, the respiratory exchange ratio was similar across groups (0.87 +/- 0.02, 0.85 +/- 0.02, and 0.86 +/- 0.01 in L, O, and NIDDM subjects, respectively), and CHO oxidation accounted for one-half of total energy expenditure during exercise. Glc Rd increased during exercise and was greatest in subjects with NIDDM (3.0 +/- 0.2, 2.9 +/- 0.2, and 4.5 +/- 0.4 ml.kg-1.min-1 in L, O, and NIDDM subjects, respectively, P < 0.05), yet Glc Rd was less than CHO oxidation during exercise, indicating net oxidation of glycogen. Glycogen oxidation was greater in L and O than in NIDDM subjects (3.4 +/- 1.0, 2.5 +/- 0.9, and 1.7 +/- 0.8 ml.kg-1.min-1; P < 0.05). In summary, during mild-intensity exercise, NIDDM subjects have an increased Glc Rd and a decreased oxidation of muscle glycogen.

Metabolite and hormonal response in smokers during rest and sustained exercise.

To evaluate the effects of acute and chronic smoking on blood glucose homeostasis, concentrations of metabolites, and hormonal responses at rest and during submaximal exercise, seven male smokers and seven similar nonsmokers were studied after an overnight fast. Nonsmokers (NS) and chronic smokers, abstaining from smoking (CS), were tested during rest and 60 min of cycle ergometry exercise at 49.7 +/- 0.8% of VO2peak. Smokers were restudied after acutely smoking (AS) two cigarettes prior to rest and one prior to exercise. Blood glucose levels were similar among NS, CS, and AS at all times. Lactate levels were elevated in AS compared with NS during exercise (2.32 +/- 0.22 mM vs 1.81 +/- 0.11; P < 0.05), with no differences in alanine. Free fatty acid levels were initially lower at rest in CS (0.45 +/- 0.04 mM) than in either AS (0.77 +/- 0.11) or NS (0.64 +/- 0.06; p < 0.05), but no other differences were found. During exercise, CS had lower glycerol levels (0.31 +/- 0.02 mM) than either AS (0.38 +/- 0.02) or NS (0.41 +/- 0.02; P < 0.05). Nevertheless, respiratory exchange ratio values were not significantly different during steady-state rest or exercise; and insulin, glucagon, and norepinephrine levels were also similar. Smokers effectively maintained normal blood glucose levels with only minor changes in some metabolite and hormone concentrations during rest and sustained exercise.

Reproducibility of computed tomography measurement of visceral adipose tissue area.

OBJECTIVE: The purpose of the current study is to examine the reproducibility of CT measurement of the cross-sectional area of abdominal adipose tissue. DESIGN: Sixteen healthy pre-menopausal women, ranging from lean to obese, underwent duplicate cross-sectional CT scans of the abdomen at the level of the 4th lumbar vertebral disc space. Subjects stood after the initial scan and were then re-positioned prior to repeat CT scanning. RESULTS: There was a high degree of reproducibility in measurement of overall cross-sectional adipose tissue (AT) and in the partitioning of this into subcutaneous and visceral AT. The excellent reproducibility is demonstrated by a high correlation between duplicate measurements (r = 0.99, P < 0.01), and by small precision errors; 1.2% of the mean value for total AT cross-sectional area, 1.9% for subcutaneous AT area, and 3.9% for visceral AT area. CONCLUSION: Measurement of abdominal AT area by cross-sectional CT scanning is not only an accurate determination of this adipose depot but can also be repeated with a high degree of precision.

Skeletal muscle utilization of free fatty acids in women with visceral obesity.

Visceral obesity is strongly associated with insulin resistance. One potential cause is increased availability of FFA. Alternatively, it has been proposed that there is impaired oxidation of lipid in individuals at risk for obesity. The extent to which either concept involves skeletal muscle is uncertain. To examine these opposing hypotheses, 17 healthy lean and obese premenopausal women, among whom cross-sectional area of visceral fat ranged from 18 to 180 cm2, participated in leg balance studies for measurement of FFA and glucose utilization during basal and insulin-stimulated conditions. A metabolic profile of skeletal muscle, based on enzyme activity, was determined in vastus lateralis muscle obtained by percutaneous biopsy. Visceral fat content was negatively correlated with insulin sensitivity (rates of leg glucose uptake and storage), but insulin resistance was not caused by glucose-FFA competition. During hyperinsulinemia, neither leg FFA uptake nor oxidation was increased in women with visceral obesity. During fasting conditions, however, rates of FFA uptake across the leg were negatively correlated with visceral adiposity as were activities of muscle carnitine palmitoyl transferase and citrate synthase. In summary, visceral adiposity is clearly associated with skeletal muscle insulin resistance but this is not due to glucose-FFA substrate competition. Instead, women with visceral obesity have reduced postabsorptive FFA utilization by muscle.

Skeletal muscle glycolytic and oxidative enzyme capacities are determinants of insulin sensitivity and muscle composition in obese women.

Regional fat distribution is an important determinant of insulin resistance in obesity. In the current study, the relationship between skeletal muscle insulin sensitivity, mid-thigh muscle composition, and the metabolic profile of muscle was investigated. Muscle composition was assessed by computed tomography of the mid-thigh, and by activities of marker enzymes of aerobic-oxidative and glycolytic pathways and muscle fiber typing using biopsies of the vastus lateralis muscle. Muscle with reduced Hounsfield attenuation on computed tomography scans was increased in proportion to obesity, and was strongly related to insulin resistance, reduced muscle oxidative capacity, and increased anaerobic and glycolytic capacities by muscle. These findings suggest that as part of its expression of insulin resistance, skeletal muscle of obese individuals is also poorly equipped for substrate oxidation and manifests increased storage of fat.

Increased dependence on blood glucose in smokers during rest and sustained exercise.

To evaluate the hypothesis that smoking increases the dependence on blood glucose as a fuel, seven male smokers [28.7 +/- 1.7 (SE) yr. 77.7 +/- 4.3 kg] and seven nonsmokers (NS; 29.1 +/- 0.9 yr, 78.7 +/- 5.3 kg) were studied in the postabsorptive condition. NS received a primed continuous infusion of [6,6-2H]glucose and [1-13C]glucose during 90 min of rest and 60 min of exercise at 49.7 +/- 0.8% of peak O2 consumption on one occasion; chronic smokers continued their overnight abstinence from smoking (CS) for one trial but, on another occasion, acutely smoked (AS) two cigarettes immediately before resting measurements and another cigarette before exercise. Plasma glucose levels were similar among all groups at all times during the trials; however, the glucose rates of appearance (Ra) at rest in CS (1.96 +/- 0.14 mg.kg-1 x min-1) and AS (2.02 +/- 0.14) were higher than in NS (1.41 +/- 0.15, P < 0.05). With exercise, the glucose Ra values rose in all groups above resting values but were significantly greater in CS (4.76 +/- 0.50) and AS (4.71 +/- 0.53) than in NS (3.31 +/- 0.16). Glucose oxidation during exercise was elevated in smokers (2.31 +/- 0.37 mg.kg-1 x min-1 in CS and 2.18 +/- 0.34 in AS) compared with NS (1.09 +/- 0.18, P < 0.05). Nicotine levels correlated with the glucose Ra in AS (r = 0.93, P < 0.01). In conclusion, the results indicate that long-term smoking, independent of acute smoking, increases the dependence on blood glucose as a fuel during rest and sustained submaximal exercise.