James C. Baldi

A randomized controlled graded exercise trial for chronic fatigue syndrome: Outcomes and mechanisms of change

The aim of this study was to investigate the potential mechanisms underlying the efficacy of graded exercise therapy for chronic fatigue syndrome (CFS). Forty-nine CFS patients were randomized to a 12-week graded exercise programme or to standard medical care. At the end of treatment the exercise group rated themselves as significantly more improved and less fatigued than the control group. A decrease in symptom focusing rather than an increase in fitness mediated the treatment effect. Graded exercise appears to be an effective treatment for CFS and it operates in part by reducing the degree to which patients focus on their symptoms.

Exercise Training in Pregnancy Reduces Offspring Size without Changes in Maternal Insulin Sensitivity

CONTEXT Epidemiological studies have identified the importance of the in utero environment in providing a healthy start to life. Previous studies have suggested that the maternal environment, in particular a reduction in maternal insulin sensitivity, contributes significantly to fetal growth. Regular aerobic exercise, through an effect on maternal insulin sensitivity, may influence offspring size by regulating nutrient supply to the fetus. OBJECTIVE The aim of the study was to determine the effects of aerobic exercise training in the second half of pregnancy on maternal insulin sensitivity and neonatal outcomes. DESIGN AND SETTING We conducted a community-based, randomized, controlled trial of exercise in pregnancy. PARTICIPANTS Eighty-four healthy nulliparous women (mean +/- sd, age, 30 +/- 4 yr; body mass index, 25.5 +/- 4 kg/m(2)) participated in the study. INTERVENTION Subjects participated in a home-based stationary cycling program from 20 wk gestation to delivery. MAIN OUTCOME MEASURES Maternal insulin sensitivity, neonatal auxology, body composition, and growth-related peptides in cord blood were measured. RESULTS Offspring of exercisers had lower birth weight (sd score, control, 0.23 +/- 0.8; exercise, -0.19 +/- 0.9; P = 0.03) and body mass index at birth (sd score, control, 0.40 +/- 0.9; exercise, -0.01 +/- 0.09; P = 0.04). The reduction in maternal insulin sensitivity in late gestation was not affected by exercise (P = 0.45) and was unrelated to offspring size. Exercise offspring had lower cord serum IGF-I (P = 0.03) and IGF-II (P = 0.04). CONCLUSIONS Regular exercise was associated with lower birth weights and reduced cord concentrations of growth-related peptides, suggesting an influence of exercise on endocrine regulation of fetal growth. These effects on offspring growth were not associated with an exercise training effect on maternal insulin sensitivity.

Reduced leg blood flow during submaximal exercise in type 2 diabetes.

UNLABELLED It is unclear whether impaired cardiac and/or vascular function contribute to exercise intolerance in patients with type 2 diabetes. PURPOSE Magnetic resonance imaging (MRI) was used to determine whether reductions in cardiac output and/or femoral arterial blood flow contribute to reduced aerobic capacity in patients with type 2 diabetes. METHODS Cardiac and femoral arterial blood flow MRI scans were performed at rest and during low-intensity leg exercise in eight patients with type 2 diabetes and 11 healthy individuals. Maximal aerobic capacity VO(2 max) and maximal oxygen pulse were also determined in all participants. RESULTS V O(2 max) was 20% lower and maximal oxygen pulse was 16% lower in patients with type 2 diabetes (P < 0.05), whereas maximal heart rate was the same between groups. Low-intensity exercise induced a 20% increase in heart rate and cardiac output as well as a 60-70% increase in femoral blood flow in both groups (P < 0.05). Femoral arterial blood flow indexed to thigh lean mass was reduced during exercise in patients with type 2 diabetes compared with healthy individuals. Stroke volume indexed to fat-free mass was lower in patients with type 2 diabetes, but greater heart rate allowed cardiac output to be maintained during submaximal exercise. CONCLUSIONS These findings suggest that impaired femoral arterial blood flow, an indirect marker of muscle perfusion, affects low-intensity exercise performance in patients with type 2 diabetes. However, because of lower exercising stroke volume, we propose that femoral arterial blood flow and, possibly, cardiac output, limit V O(2 max) in patients with type 2 diabetes.

Effects of exercise training on maternal hormonal changes in pregnancy

Context & Objective  A recent paper by our group reported that regular aerobic exercise during pregnancy led to lower foetal IGF‐I and IGF‐II concentrations and a modest reduction in offspring birth weight when compared with the offspring of nontraining control participants. Maternal hormonal alterations in response to exercise training may be associated with the regulation of nutrient availability for foetal growth through placental regulation of maternal metabolism.

Glycemic Status Affects Cardiopulmonary Exercise Response in Athletes with Type I Diabetes

PURPOSE This study aimed to (a) examine the influence of type I diabetes on the cardiopulmonary exercise response in trained subjects and (b) determine whether glycemic control affects these responses. METHODS The cardiopulmonary responses to maximal incremental cycle ergometry were compared in 12 Ironman triathletes with type I diabetes and 10 age- and sex-matched control subjects without diabetes. Athletes with type I diabetes were then stratified into low- (glycosylated hemoglobin (HbA1c) < 7%, n = 5) and high-HbA1c (HbA1c > 7%, n = 7) groups for comparison. Cardiac output, stroke volume, arterial blood pressure, and calculated systemic vascular resistance along with airway function were measured at rest and during steady-state exercise. RESULTS During peak exercise HR, stroke volume and cardiac output were not different between the groups with and without diabetes; however, forced expiratory flow at 50% of the forced vital capacity was lower in subjects with diabetes (P < 0.05). Within the group with diabetes, HbA1c was lower in the low-HbA1c versus high-HbA1c group (6.5 +/- 0.3 vs 7.8 +/- 0.4, respectively; P < 0.05), but training volume was not different. At rest, the low-HbA1c group had greater cardiac output and lower systemic vascular resistance than the high-HbA1c group, and all pulmonary function measurements were greater in the low-HbA1c group (P < 0.05). During peak exercise, the VO2, workload, HR, stroke volume, and cardiac output were greater in the low-HbA1c versus the high-HbA1c group (P < 0.05). In addition, all indices of pulmonary function were higher in the low-HbA1c group (P < 0.05). Finally, within the subjects with diabetes, there was a weak inverse correlation between HbA1c and exercise training volume (r2 = -0.352) and stroke volume (r2 = -0.339). These data suggest that highly trained individuals with type I diabetes can achieve the same cardiopulmonary exercise responses as trained subjects without diabetes, but these responses are reduced by poor glycemic control.

Structural and Functional Cardiac Abnormalities in Adolescent Girls with Poorly Controlled Type 2 Diabetes

OBJECTIVE Type 2 diabetes is associated with left ventricular hypertrophy (LVH) and diastolic dysfunction, which may eventually lead to clinical heart failure. We sought to determine the cardiovascular effects of adolescent-onset type 2 diabetes. RESEARCH DESIGN AND METHODS We recruited diabetic girls (8 with type 2 and 11 with type 1 diabetes) from a hospital diabetes service and nondiabetic control subjects (9 lean and 11 overweight) from the schools of the diabetic subjects. Echocardiography and measurements were performed by a single observer, blinded to subject group allocation, and included M-mode left ventricular dimensions, two-dimensional left ventricular mass, Doppler diastolic flows, estimation of left ventricular filling pressure, and systolic longitudinal motion. Left ventricular mass was indexed to height and fat-free body mass. ANOVA was used to compare the groups. RESULTS The groups were similar in age and height, but significant differences in body composition were observed. Subjects with type 2 diabetes had larger left ventricular dimensions and left ventricular mass, which persisted when indexed to height. Diastolic filling was impaired in both diabetic groups, and systolic longitudinal function was lower in the type 2 diabetic group. Half of the group with type 2 diabetes met the published criteria for LVH and left ventricular dilatation; 25% had evidence of elevated left ventricular filling pressure in association with structural abnormalities. CONCLUSIONS This study has demonstrated preclinical abnormalities of cardiac structure and function in adolescent girls with type 2 diabetes, despite the short duration of diabetes and highlights the potential high cardiovascular risk occurring in adolescent type 2 diabetes.

Effect of reduced total blood volume on left ventricular volumes and kinetics in type 2 diabetes.

Aim:  Although impaired left ventricular (LV) diastolic function is commonly observed in patients with type 2 diabetes, it remains unclear whether the impairment is caused by altered LV relaxation or changes in LV preload. The purpose of this study was to examine the influence of LV function and LV loading conditions on stroke volume in men with type 2 diabetes.

Diastolic Function Is Reduced in Adolescents With Type 1 Diabetes in Response to Exercise

OBJECTIVE To determine whether adolescents with type 1 diabetes have left ventricular functional changes at rest and during acute exercise and whether these changes are affected by metabolic control and diabetes duration. RESEARCH DESIGN AND METHODS The study evaluated 53 adolescents with type 1 diabetes and 22 control adolescents. Baseline data included peak exercise capacity and body composition by dual-energy X-ray absorptiometry. Left ventricular functional parameters were obtained at rest and during acute exercise using magnetic resonance imaging. RESULTS Compared with nondiabetic control subjects, adolescents with type 1 diabetes had lower exercise capacity (44.7 ± 09 vs. 48.5 ± 1.4 mL/kg fat-free mass [FFM]/min; P < 0.05). Stroke volume was reduced in the diabetes group at rest (1.86 ± 0.04 vs. 2.05 ± 0.07 mL/kg FFM; P = 0.02) and during acute exercise (1.89 ± 0.04 vs. 2.17 ± 0.06 mL/kg FFM; P = 0.01). Diabetic adolescents also had reduced end-diastolic volume at rest (2.94 ± 0.06 vs. 3.26 ± 0.09 mL/kg FFM; P = 0.01) and during acute exercise (2.78 ± 0.05 vs. 3.09 ± 0.08 mL/kg FFM; P = 0.01). End-systolic volume was lower in the diabetic group at rest (1.08 ± 0.03 vs. 1.21 ± 0.04 mL/kg FFM; P = 0.01) but not during acute exercise. Exercise capacity and resting and exercise stroke volumes were correlated with glycemic control but not with diabetes duration. CONCLUSIONS Adolescents with type 1 diabetes have reduced exercise capacity and display alterations in cardiac function compared with nondiabetic control subjects, associated with reduced stroke volume during exercise.

Design and testing of an MRI-compatible cycle ergometer for non-invasive cardiac assessments during exercise

BackgroundMagnetic resonance imaging (MRI) is an important tool for cardiac research, and it is frequently used for resting cardiac assessments. However, research into non-pharmacological stress cardiac evaluation is limited.MethodsWe aimed to design a portable and relatively inexpensive MRI cycle ergometer capable of continuously measuring pedalling workload while patients exercise to maintain target heart rates.ResultsWe constructed and tested an MRI-compatible cycle ergometer for a 1.5 T MRI scanner. Resting and sub-maximal exercise images (at 110 beats per minute) were successfully obtained in 8 healthy adults.ConclusionsThe MRI-compatible cycle ergometer constructed by our research group enabled cardiac assessments at fixed heart rates, while continuously recording power output by directly measuring pedal force and crank rotation.

Does Careful Glycemic Control Improve Aerobic Capacity in Subjects with Type 1 Diabetes

Existing evidence shows that some, but not all, individuals with type 1 diabetes are capable of the same aerobic capacity as matched nondiabetic subjects. Poor glycemic control impairs pulmonary, cardiac, and vascular responses to exercise. This review examines how careful glycemic control affects these responses and may independently improve aerobic capacity.