Type 2 diabetes exaggerates exercise effort and impairs exercise performance in older women.

OBJECTIVE: Type 2 diabetes mellitus (T2DM) is associated with high levels of disability and mortality. Regular exercise prevents premature disability and mortality, but people with T2DM are generally sedentary for reasons that are not fully established. We previously observed that premenopausal women with T2DM report greater effort during exercise than their counterparts without diabetes, as measured by the Rating of Perceived Exertion (RPE) scale. We hypothesized that RPE is greater in older women with T2DM versus no T2DM. RESEARCH DESIGN AND METHODS: We enrolled overweight, sedentary women aged 50-75 years with (n=26) or without T2DM (n=28). Participants performed submaximal cycle ergometer exercise at 30 W and 35% of individually-measured peak oxygen consumption (35% VO2peak). We assessed exercise effort by RPE (self-report) and plasma lactate concentration. RESULTS: VO2peak was lower in T2DM versus controls (p=0.003). RPE was not significantly greater in T2DM versus controls (30 W: Control, 10.4±3.2, T2DM, 11.7±2.3, p=0.08; 35% VO2peak: Control, 11.1±0.5, T2DM, 12.1±0.5, p=0.21). However, lactate was greater in T2DM versus controls (p=0.004 at 30 W; p<0.05 at 35% VO2peak). Greater RPE was associated with higher lactate, higher heart rate, and a hypertension diagnosis (p<0.05 at 30 W and 35% VO2peak). CONCLUSIONS: Taken together, physiological measures of exercise effort were greater in older women with T2DM than controls. Exercise effort is a modifiable and thereby targetable end point. In order to facilitate regular exercise, methods to reduce exercise effort in T2DM should be sought. TRIAL NUMBER: NCT00785005.

Effects of exercise training on oxygen uptake kinetic responses in women with type 2 diabetes.

OBJECTIVE: Women with uncomplicated type 2 diabetes have both a decreased maximal oxygen consumption (VO2max) and slowed oxygen uptake (VO2) kinetics at the onset of exercise compared with nondiabetic women. These abnormalities are seen not only at maximal workloads, but also at the onset of low-level exercise. To evaluate the hypothesis that VO2max and VO2 kinetics would improve with exercise training in untrained people with type 2 diabetes, we measured these parameters in premenopausal sedentary women before and after 3 months of supervised exercise training. RESEARCH DESIGN AND METHODS: A total of 8 women with type 2 diabetes, 9 overweight nondiabetic women, and 10 lean nondiabetic women were studied. At baseline and after 3 months of exercise training, subjects underwent bicycle ergometer testing to obtain VO2max and VO2 kinetics data. RESULTS: On entry, women with type 2 diabetes had the lowest VO2max and slowest VO2 kinetics of the three groups. After exercise training, the women with type 2 diabetes improved their VO2max more than the lean and overweight control women: 28 vs. 5 and 8%, respectively (P < 0.05 for the diabetic group vs. both control groups). In the group with diabetes, VO2 kinetics improved by 39 and 22% at 20 and 30 W, respectively. For the control subjects, VO2 kinetics did not improve at any workload in either group. CONCLUSIONS: Despite beginning with the lowest VO2max and slowest VO2 kinetics, subjects with type 2 diabetes benefited more from an exercise training program than did control subjects. These findings suggest that in addition to its known metabolic effects, exercise training in individuals with type 2 diabetes may be an effective therapy to improve the cardiovascular response to exercise and to overcome low-level exercise impairment as reflected by improved VO2max and VO2 kinetics. If the ability to make circulatory adjustments at the beginning of exercise at low workloads is improved by an exercise training program, as suggested by the VO2 kinetics data, the clinical significance of exercise for people with type 2 diabetes is clear.

Oxygen uptake kinetics during exercise are slowed in patients with peripheral arterial disease.

Patients with peripheral arterial disease (PAD) have arterial occlusions that limit peripheral blood flow. This study evaluated the dynamic response in O(2) consumption (VO(2)) at the onset of constant-load exercise (VO(2) kinetics) in patients with PAD. Eight patients with bilateral PAD, seven patients with unilateral PAD, nine age-matched nonsmoking controls, and seven smoking controls performed graded treadmill exercise to assess peak VO(2). Subjects also performed constant-load exercise tests at 2.0 miles/h at 0 and 4% grade to determine VO(2) kinetics. Peak VO(2) was reduced 50% in patients with PAD compared with both control groups (P < 0.05). At 4% grade, phase 2 VO(2) kinetics were significantly slowed for the PAD groups compared with controls (60.1 +/- 15.7 and 58.7 +/- 8.3 s, unilateral and bilateral PAD groups, respectively; compared with 28. 4 +/- 19.3 and 27.9 +/- 8.1 s, nonsmoking and smoking controls, respectively; P < 0.05). No relationship was found between VO(2) kinetics and disease severity. These data demonstrate that VO(2) kinetics are markedly slowed in patients with PAD. The impairment in VO(2) kinetics is not related to smoking status or arterial disease severity and therefore may reflect altered control of skeletal muscle metabolism.

Abnormal oxygen uptake kinetic responses in women with type II diabetes mellitus.

Persons with type II diabetes mellitus (DM), even without cardiovascular complications have a decreased maximal oxygen consumption (VO2 max) and submaximal oxygen consumption (VO2) during graded exercise compared with healthy controls. We evaluated the hypothesis that change in the rate of VO2 in response to the onset of constant-load exercise (measured by VO2-uptake kinetics) was slowed in persons with type II DM. Ten premenopausal women with uncomplicated type II DM, 10 overweight, nondiabetic women, and 10 lean, nondiabetic women had a VO2 max test. On two separate occasions, subjects performed 7-min bouts of constant-load bicycle exercise at workloads below and above the lactate threshold to enable measurements of VO2 kinetics and heart rate kinetics (measuring rate of heart rate rise). VO2 max was reduced in subjects with type II DM compared with both lean and overweight controls (P < 0.05). Subjects with type II DM had slower VO2 and heart rate kinetics than did controls at constant workloads below the lactate threshold. The data suggest a notable abnormality in the cardiopulmonary response at the onset of exercise in people with type II DM. The findings may reflect impaired cardiac responses to exercise, although an additional defect in skeletal muscle oxygen diffusion or mitochondrial oxygen utilization is also possible.

Vaginal misoprostol for term labor induction.

Misoprostol is an effective agent for cervical ripening and induction of labor. The use of oxytocin was significantly decreased in patients treated with misoprostol versus dinoprostone. It has been used to induce over 1000 women in reported studies and has demonstrated a safety profile comparable with that of endocervical and vaginal dinoprostone. Uterine hyperstimulation was a concern in earlier trials, but at a reduced dose of 25 micrograms, the incidence has decreased to a level that is comparable with the values reported for dinoprostone. Misoprostol tablets are stable at room temperature and are considerably less expensive than the dinoprostone alternatives. Two additional factors pertaining to misoprostol administration must be taken into account before the drug is selected for vaginal use. First, Cytotec tablets are currently available in two strengths, 100 and 200 micrograms. This can lead to confusion or error if the clinician orders a quarter or half tablet. The order should always identify the strength in micrograms (25 or 50 micrograms). Second, the 100-microgram tablet is not scored; therefore, the proper dose should be carefully prepared by a pharmacist using a pill cutter. Key members of the hospital staff must be trained about the proper use of misoprostol for labor induction before initiating therapy. One alternative to directly inserting the tablet is to pulverize it and mix with a gel such as hydroxyethylcellulose gel. However, such compounding introduces the same problems with stability and uniformity of dose as experienced with dinoprostone gels. Despite the success of misoprostol in clinical trials, it is not approved for this indication, and the manufacturer of Cytotec does not plan to pursue approval. Therefore, independent, large-scale studies are warranted to more accurately assess the efficacy and overall safety of using intravaginal alprostadil for cervical ripening and labor induction. Additional clinical experience should also help to determine the best regimen and method of administration. From the data currently available, it appears that either a 25- or 50-microgram dose (one-fourth or one-half of a 100-microgram tablet) inserted into the posterior vaginal fornix and repeated at 4-5-hour intervals if needed, is a clinically effective regimen, and is associated with the least amount of adverse effects and complications. As with all labor inductions, uterine contractions and fetal heart rate should be monitored carefully throughout the procedure.

Cycling cadence alters exercise hemodynamics.

Previous studies on cycling cadence have focused on the economy of the cadence, in search of the optimal pedal cadence. The purpose of this study was to determine the hemodynamic changes associated with varying pedal cadence at a constant workload. It was hypothesized that increased pedal cadence would enhance the skeletal muscle pump, resulting in elevation of cardiac output. Seven cyclists were enlisted to cycle at 200 watts at pedal cadences of 70, 90 and 110 rpm (random order). Oxygen uptake, heart rate, stroke volume, cardiac output, blood pressure, and vascular resistance were determined. As has been previously shown, oxygen uptake increased with increased cadence (70, 90, 110 rpm) at this workload. Heart rate, stroke volume, cardiac output and blood pressure were increased, and vascular resistance decreased, with increased cadence. Cardiac output increased (34%) in excess of the increase in oxygen uptake (15%) as shown by the decrease (-14.5%) in the arterial-venous oxygen difference occurring with increasing cadence. Apparently, even though the workload was constant, the increase in pedal cadence resulted in a more effective skeletal-muscle pump which increased muscle blood flow and venous return. It is not known if this might contribute to the natural selection of higher cadences by cycling athletes, even though there is reduced economy.