To examine the longitudinal associations between different physical activity (PA) intensities and cardiometabolic risk factors among a sample of Canadian youth.
The findings are based on a 2-year ...prospective cohort study in a convenience sample of 315 youth aged 9-15 years at baseline from rural and urban schools in Alberta, Canada. Different intensities (light, moderate and vigorous) of PA were objectively assessed with Actical accelerometers. The main outcome measures were body mass index (BMI) z-score, waist circumference, cardiorespiratory fitness and systolic blood pressure at 2-year-follow-up and conditional BMI z-score velocity. A series of linear regression models were conducted to investigate the associations after adjusting for potential confounders.
At follow-up, cardiorespiratory fitness increased (quartile 1 vs quartile 4=43.3 vs 50.2; P(trend)<0.01) and waist circumference decreased (quartile 1 vs quartile 4=79.0 vs 72.6; P(trend)=0.04; boys only) in a dose-response manner across quartiles of baseline vigorous-intensity PA. A similar trend was observed for systolic blood pressure (quartile 1 vs quartile 4=121.8 vs 115.3; P(trend)=0.07; boys only). Compared with quartile 1 of vigorous-intensity PA, BMI z-score at follow-up and conditional BMI z-score velocity were significantly lower in the quartile 2 and 3 (P<0.05). Waist circumference at follow-up also decreased (quartile 1 vs quartile 4=75.3 vs 73.8; P(trend)=0.04) across quartiles of baseline moderate-intensity PA.
Time spent in vigorous-intensity PA was associated with several positive health outcomes 2 years later. These findings suggest that high-intensity activities in youth help to reduce the risk for several chronic diseases.
Aims/hypothesis The Diabetes Aerobic and Resistance Exercise (DARE) study showed that aerobic and resistance exercise training each improved glycaemic control and that a combination of both was ...superior to either type alone in patients with type 2 diabetes mellitus. Here we report effects on patient-reported health status and well-being in the DARE Trial. Methods We randomised 218 inactive participants with type 2 diabetes mellitus in parallel to 22 weeks of aerobic exercise (n = 51), resistance exercise (n = 58), combined aerobic and resistance exercise (n = 57) or no exercise (control; n = 52). Intervention allocation was managed by a central office. Outcomes included health status as assessed by the physical and mental component scores of the Medical Outcomes Trust Short-Form 36-item version (SF-36) and well-being as measured by the Well-Being Questionnaire 12-item version (WBQ-12); these were measured at the Ottawa Hospital. Results Using a p value of 0.0125 for statistical significance due to multiple comparisons, mixed model analyses indicated that resistance exercise led to clinically but not statistically significant improvements in the SF-36 physical component score compared with aerobic exercise (Δ = 2.7 points; p = 0.048) and control (i.e. no exercise; Δ = 3.3 points; p = 0.015). For mental component scores, there were clinically important improvements favouring no (control) compared with resistance (Δ = 7.6 points; p < 0.001) and combined (Δ = 7.2 points; p < 0.001) exercise. No effects on WBQ-12 scores were noted. Overall, 59/218 (27%) of participants included in this analysis sustained an adverse event during the course of the study, including 16 participants in the combined exercise group, 19 participants in the resistance exercise group, 16 participants in the aerobic exercise group, and eight participants in the control group. All participants were included in the intent-to-treat analyses. The trial is now closed to follow-up. Conclusions/interpretation Resistance exercise was better than aerobic or no exercise for improving physical health status in these patients. No exercise was superior to resistance or combined exercise for improving mental health status. Well-being was unchanged by intervention. Trial registration: ClinicalTrials.gov NCT00195884 Funding: This study was funded by the Canadian Institutes of Health Research (grant MCT-44155) and the Canadian Diabetes Association (The Lillian Hollefriend Grant).
Low cardiorespiratory fitness is a powerful and independent predictor of mortality in people with diabetes. Several studies have examined the effects of exercise on cardiorespiratory fitness in Type ...2 diabetic individuals. However, these studies had relatively small sample sizes and highly variable results. Therefore the aim of this study was to systematically review and quantify the effects of exercise on cardiorespiratory fitness in Type 2 diabetic individuals.
MEDLINE, EMBASE, and four other databases were searched up to March 2002 for randomized, controlled trials evaluating effects of structured aerobic exercise interventions of 8 weeks or more on cardiorespiratory fitness in adults with Type 2 diabetes. Cardiorespiratory fitness was defined as maximal oxygen uptake (VO(2max)) during a maximal exercise test.
Seven studies, presenting data for nine randomized trials comparing exercise and control groups (overall n=266), met the inclusion criteria. Mean exercise characteristics were as follows: 3.4 sessions per week, 49 min per session for 20 weeks. Exercise intensity ranged from 50% to 75% of VO(2max). There was an 11.8% increase in VO(2max) in the exercise group and a 1.0% decrease in the control group (post intervention standardized mean difference =0.53, p<0.003). Studies with higher exercise intensities tended to produce larger improvements in VO(2max). Exercise intensity predicted post-intervention weighted mean difference in HbA(1c) (r=-0.91, p=0.002) to a larger extent than did exercise volume (r=-0.46, p=0.26).
Regular exercise has a statistically and clinically significant effect on VO(2max) in Type 2 diabetic individuals. Higher intensity exercise could have additional benefits on cardiorespiratory fitness and HbA(1c).
CONTEXT Exercise is widely perceived to be beneficial for glycemic control and
weight loss in patients with type 2 diabetes. However, clinical trials on
the effects of exercise in patients with type ...2 diabetes have had small sample
sizes and conflicting results. OBJECTIVE To systematically review and quantify the effect of exercise on glycosylated
hemoglobin (HbA1c) and body mass in patients with type 2 diabetes. DATA SOURCES Database searches of MEDLINE, EMBASE, Sport Discuss, Health Star, Dissertation
Abstracts, and the Cochrane Controlled Trials Register for the period up to
and including December 2000. Additional data sources included bibliographies
of textbooks and articles identified by the database searches. STUDY SELECTION We selected studies that evaluated the effects of exercise interventions
(duration ≥8 weeks) in adults with type 2 diabetes. Fourteen (11 randomized
and 3 nonrandomized) controlled trials were included. Studies that included
drug cointerventions were excluded. DATA EXTRACTION Two reviewers independently extracted baseline and postintervention
means and SDs for the intervention and control groups. The characteristics
of the exercise interventions and the methodological quality of the trials
were also extracted. DATA SYNTHESIS Twelve aerobic training studies (mean SD, 3.4 0.9 times/week for
18 15 weeks) and 2 resistance training studies (mean SD, 10 0.7 exercises,
2.5 0.7 sets, 13 0.7 repetitions, 2.5 0.4 times/week for 15 10 weeks)
were included in the analyses. The weighted mean postintervention HbA1c was lower in the exercise groups compared with the control groups
(7.65% vs 8.31%; weighted mean difference, −0.66%; P<.001). The difference in postintervention body mass between exercise
groups and control groups was not significant (83.02 kg vs 82.48 kg; weighted
mean difference, 0.54; P = .76). CONCLUSION Exercise training reduces HbA1c by an amount that should
decrease the risk of diabetic complications, but no significantly greater
change in body mass was found when exercise groups were compared with control
groups.
Aim/hypothesis In people with type 2 diabetes, exercise improves glucose control (as reflected in HbA₁c) and physical fitness, but it is not clear to what extent these exercise-induced improvements ...are correlated with one another. We hypothesised that reductions in HbA₁c would be related: (1) to increases in aerobic fitness and strength respectively in patients performing aerobic training or resistance training; and (2) to changes in strength and aerobic fitness in patients performing aerobic and resistance training. Methods We randomly allocated 251 type 2 diabetes patients to aerobic, resistance, or aerobic plus resistance training, or to a sedentary control group. Peak oxygen consumption ( graphic removed ), workload, treadmill time and ventilatory threshold measurements from maximal treadmill exercise testing were measured at baseline and 6 months. Muscular strength was measured as the maximum weight that could be lifted eight times on the leg press, bench press and seated row exercises. Results With aerobic training, significant associations were found between changes in both graphic removed (p = 0.040) and workload (p = 0.022), and changes in HbA₁c. With combined training, improvements in graphic removed (p = 0.008), workload (p = 0.034) and ventilatory threshold (p = 0.003) were significantly associated with changes in HbA₁c. Increases in strength on the seated row (p = 0.006) and in mid-thigh muscle cross-sectional area (p = 0.030) were significantly associated with changes in HbA₁c after resistance exercise, whereas the association between increases in muscle cross-sectional area and HbA₁c in participants doing aerobic plus resistance exercise (p = 0.059) was of borderline significance. Conclusions/interpretation There appears to be a link between changes in fitness and HbA₁c. The improvements in cardiorespiratory fitness with aerobic training may be a better predictor of changes in HbA₁c than improvements in strength.
Physical activity and metformin are often used concomitantly in the treatment of diabetes, even though little is known about possible interactions between these treatment modalities. This study was ...designed to examine the acute effect of metformin on oxygen consumption and lactate concentration during exercise. Eleven healthy, active men mean ± s.d.: age = 29.9 ± 3.7 years; body mass index = 25.2 ± 2.8 kg/m²; maximal oxygen consumption (VO₂max) = 53.5 ± 8.9 ml/kg/min completed a randomized, double-blind, placebo-controlled, crossover study. The testing protocol consisted of a standardized breakfast with metformin (1000 mg) or placebo. Three hours after breakfast, participants underwent a graded maximal exercise test on a cycle ergometer. Approximately 30 min after this exercise test, participants cycled continuously at an intensity below their ventilatory threshold for 45 min (mean exercise intensity = 69 ± 5.5% of VO₂max). During the graded exercise test, average oxygen consumption was higher for the metformin condition (2.9 vs. 2.8 l/min, p = 0.04); however, there was no treatment effect on VO₂max or ventilatory threshold. During continuous exercise, lactate was lower for the metformin condition (4.7 vs. 5.4 mmol/l, p = 0.05). Following a standardized lunch, glucose concentrations were lower in the metformin compared with the placebo condition (5.8 vs. 6.4 mmol/l, p = 0.04). A single dose of metformin does not acutely influence maximal oxygen consumption or ventilatory threshold in healthy active males. The lower lactate concentration observed during continuous exercise with metformin was an unexpected finding considering that, in the resting state, metformin has been previously associated with a modest increase in lactate concentrations.
Effects of Exercise Training on Glucose Homeostasis
The HERITAGE Family Study
Normand G. Boulé , MA 1 ,
S. John Weisnagel , MD 1 2 ,
Timo A. Lakka , MD, PHD 3 4 ,
Angelo Tremblay , PHD 1 ,
Richard N. ...Bergman , PHD 5 ,
Tuomo Rankinen , PHD 3 ,
Arthur S. Leon , MD 6 ,
James S. Skinner , PHD 7 ,
Jack H. Wilmore , PHD 8 ,
D.C. Rao , PHD 9 and
Claude Bouchard , PHD 3
1 Division of Kinesiology, Laval University, Ste-Foy, Québec, Canada
2 Diabetes Research Unit, Centre de Recherche sur les Maladies Lipidiques, Laval University, Ste-Foy, Québec, Canada
3 Human Genomics Laboratory, Pennington Biomedical Research Center, Louisiana State University, Baton Rouge, Louisiana
4 Kuopio Research Institute of Exercise Medicine and the Department of Physiology, University of Kuopio, Kuopio, Finland
5 Keck School of Medicine, University of Southern California, Los Angeles, California
6 Laboratory of Physiological Hygiene and Exercise Science, Division of Kinesiology, University of Minnesota, Minneapolis, Minnesota
7 Department of Kinesiology, Indiana University, Bloomington, Indiana
8 Department of Health and Kinesiology, Texas A&M University, College Station, Texas
9 Departments of Genetics and Psychiatry, Division of Biostatistics, Washington University School of Medicine, St. Louis, Missouri
Address correspondence and reprint requests to S. John Weisnagel, MD, FRCPC, Diabetes Research Unit, S-27, Centre Hospitalier
Université Laval, Laval University, 2705 Boulevard Laurier Sainte-Foy, Québec, Canada, G1V 4G2. E-mail: john.weisnagel{at}kin.msp.ulaval.ca
Abstract
OBJECTIVE —To determine the effect of a 20-week endurance training program in healthy, previously sedentary participants on measures
derived from an intravenous glucose tolerance test (IVGTT).
RESEARCH DESIGN AND METHODS —An IVGTT was performed before and after a standardized training program in 316 women and 280 men (173 blacks and 423 whites).
Participants exercised on cycle ergometers 3 days per week for 60 sessions. The exercise intensity was progressively increased
from 55% V o 2max for 30 min per session to 75% V o 2max for 50 min per session.
RESULTS —Mean insulin sensitivity increased by 10% ( P < 0.001) following the intervention, but the variability in the changes was high. Men had larger improvements than women
( P = 0.02). Improvements in fasting insulin were transitory, disappearing 72 h after the last bout of exercise. There were also
significant mean increases in the glucose disappearance index (3%, P = 0.02) and in glucose effectiveness (11%, P < 0.001), measures of glucose tolerance and of the capacity of glucose to mediate its own disposal, respectively. The acute
insulin response to glucose, a measure of insulin secretion, increased by 7% in the quartile with the lowest baseline glucose
tolerance and decreased by 14% in the quartile with the highest baseline glucose tolerance ( P < 0.001). The glucose area below fasting levels during the IVGTT was reduced by 7% ( P = 0.02).
CONCLUSIONS —Although the effects of structured regular exercise were highly variable, there were improvements in virtually all IVGTT-derived
variables. In the absence of substantial weight loss, regular exercise is required for sustained improvements in glucose homeostasis.
AIRg, acute insulin response to glucose
IVGTT, intravenous glucose tolerance test
Footnotes
N.G.B. is currently affiliated with the Faculty of Physical Education and Recreation, University of Alberta, Edmonton, Alberta,
Canada.
N.G.B. and S.J.W. contributed equally as first authors to this article.
C.B. has been on advisory panels for Baylor Children’s Nutrition Research Center, the Boston Obesity & Nutrition Research
Center of the National Institutes of Health, the Institutes for Pharmaceutical Discovery, Mars, Sanofi-Synthelabo, the Cooper
Institute for Aerobic Research, and Weight Watchers International; has been on the board of directors for the Pennington Biomedical
Research Center; has received consulting fees from the Pennington Biomedical Research Center, the Almond Board of California,
and Bristol-Myers Squibb; and has received research/grant support from Bristol-Myers Squibb.
Accepted September 21, 2004.
Received April 27, 2004.
DIABETES CARE
OBJECTIVE: The main objective of the study was to examine the effect of early life malnutrition on the relation between insulin sensitivity and abdominal adiposity in adulthood. It was hypothesised ...that participants with early life malnutrition would display a more pronounced deterioration of insulin sensitivity in association with a gain in abdominal fat. DESIGN: As a first attempt to investigate this issue, we studied the effect of body fat gains in a cross-sectional context. SUBJECTS: A total of 26 young adult men with evidence of malnutrition during the first year of life and 27 control subjects were recruited for this study. Malnutrition status was determined from medical files of paediatric hospitals in the Mexico City metropolitan area. MEASUREMENTS: Insulin sensitivity was measured by hyperinsulinaemic euglycaemic clamp, and body composition was measured by anthropometrics, bioelectrical impedance and computed tomography. RESULTS: There was a negative correlation between total abdominal adipose tissue area and insulin sensitivity in the previously malnourished and control groups (r2=0.65 and 0.35, P<0.01, respectively). When matched for low amounts of abdominal fat (114 cm2), participants with and without early life malnutrition had similar insulin sensitivity (9.03 vs 8.88 mg kg-1 min-1). However, when matched for high amounts of abdominal fat (310 cm2) participants who were malnourished during the first year of life had lower insulin sensitivity (4.74 vs 6.85 mg kg-1 min-1, P<0.05). CONCLUSION: Higher levels of abdominal adipose tissue are more detrimental to insulin sensitivity in previously malnourished individuals.
Aim/hypothesis: In people with type 2 diabetes, exercise improves glucose control (as reflected in HbA sub(1c)) and physical fitness, but it is not clear to what extent these exercise-induced ...improvements are correlated with one another. We hypothesised that reductions in HbA sub(1c) would be related: (1) to increases in aerobic fitness and strength respectively in patients performing aerobic training or resistance training; and (2) to changes in strength and aerobic fitness in patients performing aerobic and resistance training. Methods: We randomly allocated 251 type 2 diabetes patients to aerobic, resistance, or aerobic plus resistance training, or to a sedentary control group. Peak oxygen consumption ( V limits times O 2 peak ), workload, treadmill time and ventilatory threshold measurements from maximal treadmill exercise testing were measured at baseline and 6months. Muscular strength was measured as the maximum weight that could be lifted eight times on the leg press, bench press and seated row exercises. Results: With aerobic training, significant associations were found between changes in both V limits times O 2 peak (p=0.040) and workload (p=0.022), and changes in HbA sub(1c.) With combined training, improvements in V limits times O 2 peak (p=0.008), workload (p=0.034) and ventilatory threshold (p=0.003) were significantly associated with changes in HbA sub(1c.) Increases in strength on the seated row (p=0.006) and in mid-thigh muscle cross-sectional area (p=0.030) were significantly associated with changes in HbA sub(1c) after resistance exercise, whereas the association between increases in muscle cross-sectional area and HbA sub(1c) in participants doing aerobic plus resistance exercise (p=0.059) was of borderline significance. Conclusions/interpretation: There appears to be a link between changes in fitness and HbA sub(1c). The improvements in cardiorespiratory fitness with aerobic training may be a better predictor of changes in HbA sub(1c) than improvements in strength.
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