The effect of regular exercise on insulin sensitivity in type 2 diabetes mellitus: A systematic review and meta-analysis

The purpose of this study was to examine the effect of regular exercise training on insulin sensitivity in adults with type 2 diabetes mellitus ( T2DM ) using the pooled data available from randomised controlled trials. In addition, we sought to determine whether short-term periods of physical inactivity diminish the exercise-induced improvement in insulin sensitivity. Eligible trials included exercise interventions that involved ≥3 exercise sessions, and reported a dynamic measurement of insulin sensitivity. There was a significant pooled effect size ( ES ) for the effect of exercise on insulin sensitivity ( ES, –0.588; 95% confidence interval [CI], –0.816 to –0.359; P < 0.001 ). Of the 14 studies included for meta-analyses, nine studies reported the time of data collection from the last exercise bout. There was a significant improvement in insulin sensitivity in favour of exercise versus control between 48 and 72 hours after exercise ( ES, –0.702; 95% CI, –1.392 to –0.012; P=0.046 ); and this persisted when insulin sensitivity was measured more than 72 hours after the last exercise session ( ES, –0.890; 95% CI, –1.675 to –0.105; P=0.026 ). Regular exercise has a significant benefit on insulin sensitivity in adults with T2DM and this may persist beyond 72 hours after the last exercise session

The association between cardiorespiratory fitness, liver fat and insulin resistance in adults with or without type 2 diabetes : a cross-sectional analysis

Background: Exercise-induced improvements in cardiorespiratory fitness (CRF) often coincide with improvements in insulin sensitivity and reductions in liver fat content. However, there are limited data concerning the relationship between CRF and liver fat content in adults with varying degrees of metabolic dysfunction. Methods: The aim of this study was to examine the association between CRF, liver fat content, and insulin resistance in inactive adults with obesity and with or without type 2 diabetes (T2D), via cross-sectional analysis. CRF was determined via a graded exercise test. Liver fat content was assessed via proton magnetic resonance spectroscopy and insulin resistance was assessed via homeostatic model of insulin resistance (HOMA-IR). A partial correlation analysis, controlling for age and gender, was performed to determine the association between CRF, demographic, cardiometabolic, and anthropometric variables. Independent t tests were performed to compare cardiometabolic outcomes between participants with T2D and participants without T2D. Results: Seventy-two adults (46% male) with a mean age of 49.28 ± 10.8 years, BMI of 34.69 ± 4.87 kg/m2 , liver fat content of 8.37 ± 6.90%, HOMA-IR of 3.07 ± 2.33 and CRF of 21.52 ± 3.77 mL/kg/min participated in this study. CRF was inversely associated with liver fat content (r = − 0.28, p = 0.019) and HOMA-IR (r = − 0.40, p < 0.001). Participants with T2D had significantly higher liver fat content (+ 3.66%, p = 0.024) and HOMA-IR (+ 2.44, p < 0.001) than participants without T2D. Participants with T2D tended to have lower CRF than participants without T2D (− 1.5 ml/kg/min, p = 0.094). Conclusion: CRF was inversely associated with liver fat content and insulin resistance. Participants with T2D had lower CRF than those without T2D, however, the difference was not statistically significant. Further longitudinal studies are required to elucidate the relationship between CRF and the progression of obesity-related diseases such as T2D. Registration: ACTRN12614001220651 (retrospectively registered on the 19th November 2014) and ACTRN12614000723684 (prospectively registered on the 8th July 2014)

The efficacy of exercise training for cutaneous microvascular reactivity in the foot in people with diabetes and obesity : secondary analyses from a randomized controlled trial

It is unclear if cutaneous microvascular dysfunction associated with diabetes and obesity can be ameliorated with exercise. We investigated the effect of 12-weeks of exercise training on cutaneous microvascular reactivity in the foot. Thirty-three inactive adults with type 2 diabetes and obesity (55% male, 56.1 +/- 7.9 years, BMI: 35.8 +/- 5, diabetes duration: 7.9 +/- 6.3 years) were randomly allocated to 12-weeks of either (i) moderate-intensity continuous training [50-60% peak oxygen consumption (VO2peak), 30-45 min, 3 d/week], (ii) low-volume high-intensity interval training (90% VO2peak, 1-4 min, 3 d/week) or (iii) sham exercise placebo. Post-occlusive reactive hyperaemia at the hallux was determined by laser-Doppler fluxmetry. Though time to peak flux post-occlusion almost halved following moderate intensity exercise, no outcome measure reached statistical significance (p > 0.05). These secondary findings from a randomised controlled trial are the first data reporting the effect of exercise interventions on cutaneous microvascular reactivity in the foot in people with diabetes. A period of 12 weeks of moderate-intensity or low-volume high-intensity exercise may not be enough to elicit functional improvements in foot microvascular reactivity in adults with type 2 diabetes and obesity. Larger, sufficiently powered, prospective studies are necessary to determine if additional weight loss and/or higher exercise volume is required

The effect of acute aerobic exercise on central arterial stiffness, wave reflection and hemodynamics in adults with diabetes: a randomized cross-over design

Background: Individuals with diabetes have greater central arterial stiffness, wave reflections, and hemodynamics, all of which promote the accelerated cardiovascular pathology seen in this population. Acute aerobic exercise has been shown to be an effective strategy for reducing central arterial stiffness, wave reflections, and hemodynamics in healthy individuals; however, the effects of acute aerobic exercise in reducing these outcomes is not well established in people with diabetes. Recently, implementation of high-intensity interval exercise (HIIE) has shown superior improvements in cardiovascular health outcomes when compared to traditional aerobic exercise. Yet, the effect of HIIE on the aforementioned outcomes in people with diabetes is not known. The purpose of this study was to (i) describe the central arterial stiffness, wave reflections, and hemodynamic responses to a bout of HIIE and moderate-intensity continuous exercise (MICE) in adults with diabetes; and (ii) compare the effects of HIIE and MICE on the aforementioned outcomes. Methods: A total of 24 adult men and women (aged 29–59 years old) with type 1 (n = 12) and type 2 (n = 12) diabetes participated in a randomized cross-over study. All participants completed the following protocols: (i) HIIE: cycling for 4 × 4 min at 85%–95% of heart rate peak (HRpeak), interspersed with 3 min of active recovery at 60%–70%HRpeak; (ii) MICE: 33 min of continuous cycling at 60%–70%HRpeak; and (iii) control (CON): lying quietly in a supine position for 30 min. Results: A significant group × time effect was found for changes in central systolic blood pressure (F = 3.20, p = 0.01) with a transient reduction for the HIIE group but not for the MICE or CON groups. There was a significant group × time effect for changes in augmentation index at a heart rate of 75 beats/min (F = 2.32, p = 0.04) with a decrease following for HIIE and MICE but not for CON. For all other measures of central arterial stiffness and hemodynamics, no significant changes were observed (p > 0.05). Conclusion: A bout of HIIE appears to lead to a greater transient reduction in central systolic blood pressure than the reduction observed following MICE; however, both HIIE and MICE improved augmentation index at a heart rate of 75 beats/min in people with diabetes. There was no significant difference in response to HIIE and MICE in all outcomes. This provides preliminary evidence on the role of HIIE on such outcomes in people with diabetes

The effect of high intensity interval training versus moderate intensity continuous training on arterial stiffness and 24 h blood pressure responses : a systematic review and meta-analysis

Objectives: Greater arterial stiffness and poor 24 h blood pressure (BP) are recognized as indicators of poor cardiovascular health. Evidence has shown that high intensity interval training (HIIT) may be a superior alternative to moderate intensity continuous training (MICT) for improving cardiovascular disease risk factors such as cardiorespiratory fitness and vascular function. However, there are limited data comparing the effect of HIIT to MICT on central arterial stiffness and/or 24 h BP response. The purpose of this study was to compare HIIT versus MICT on central arterial stiffness and 24 h BP outcomes by systematic review and meta-analysis. Design: A systematic review and meta-analysis was conducted. Methods: Eligible studies were exercise training interventions (≥4 weeks) that included both HIIT and MICT and reported central arterial stiffness, as measured by pulse wave velocity and augmentation index and/or 24 h BP outcome measures. Results: HIIT was found to be superior to MICT for reducing night-time diastolic BP (ES: −0.456, 95% CI: −0.826 to −0.086 mmHg; P = 0.016). A near-significant greater reduction in daytime systolic (ES: −0.349, 95% CI: −0.740 to 0.041 mmHg; p = 0.079) and diastolic BP was observed with HIIT compared to MICT (ES: −0.349, 95% CI: −0.717 to 0.020 mmHg; p = 0.063). No significant difference was found for other BP responses or arterial stiffness outcomes. Conclusions: HIIT leads to a superior reduction in night-time diastolic BP compared to MICT. Furthermore, a near-significant greater reduction in daytime BP was found with HIIT compared to MICT. No significant difference was observed for changes to central arterial stiffness between HIIT and MICT

The association between cardiorespiratory fitness and NAFLD in overweight and obese adults

Introduction: Cardiorespiratory fitness (CRF) is a known independent risk factor for morbidity and mortality (1). Furthermore, CRF and obesity have been shown to be associated with impaired fasting glucose (IFG) and type 2 diabetes (T2D) by similar magnitudes (2). Nonalcoholic fatty liver disease (NAFLD) is also associated with IFG and T2D, and increases in CRF has been shown to mitigate IFG and insulin resistance. The primary aim of this study was to explore the association between CRF and NAFLD in inactive adults with overweight and obesity. A secondary aim was to examine the possible association between CRF and NAFLD independent of known demographic and anthropometric risk factors. Methods: CRF, IHL, and other demographic, anthropometric and biochemical risk factors were assessed in 67 inactive, overweight and obese adults with and without diabetes. CRF was measured via a graded exercise test (Lode Corival cycle ergometer). NAFLD was assessed by grading participants’ liver fat concentration via proton magnetic spectroscopy (where a liver fat score >5.5% was classified as NAFLD positive). Bivariate regression and hierarchical multiple regression analyses were performed. RESULTS: CRF was not associated with NAFLD (p=0.49) nor liver fat concentration (p=0.09). CRF was associated with other cardiometabolic risk factors such as fasting blood glucose (p=0.02), fasting serum insulin (p=0.02) and systolic blood pressure (p=0.04), however these associations were not independent of BMI. Conclusion: Our findings showed that CRF was not associated with NAFLD in inactive, overweight and obese adults, with and without diabetes. Additional studies incorporating a greater variation in CRF are needed to further explore the relationship between CRF and liver fat

Sex differences in physical and mental health following high-intensity interval training in adults with cardiovascular disease who completed cardiac rehabilitation

This pre-post study examined sex-differences in peak aerobic power (V̇O2peak) and physical- and mental-health outcomes in adults with cardiovascular disease who completed high-intensity interval training (HIIT)-based cardiac rehabilitation. HIIT consisted of 25 minutes of alternating higher- (4 minutes 85-95% HRpeak) and lower- (3 minutes 60-70% HRpeak) intensity intervals twice weekly for 10 weeks. V̇O2peak estimated from a graded exercise test using the ACSM equation, body mass index (BMI), waist circumference, blood pressure, blood biomarkers and anxiety and depression were assessed at baseline and follow-up. Linear mixed-effects models for repeated measures were performed to examine differences over time between sexes. Of 140 participants (mean standard deviation: 589 years), 40 were female. Improvements in V̇O2peak did not differ between sexes (interaction: p=0.273, females: 28.46.4 to 30.97.6; males: 34.36.3 to 37.46.0 mL/kg/min). None of the time by sex interactions were significant. Significant main effects of time showed reductions in waist circumference, triglycerides, LDL, TC/HDL and anxiety, and increases in V̇O2peak and HDL from baseline to follow-up. Significant main effects of sex revealed smaller V̇O2peak, BMI and waist circumference, and higher LDL, TC and HDL in females than males. HIIT led to similar improvements in estimated V̇O2peak (females: 8.8%, males: 9.0%) and additional health outcomes between sexes. Novelty • HIIT-based CR led to similar improvements in estimated V̇O2peak and other physical and mental health outcomes between sexes. • The number of sessions attended was high (>70%) and did not differ by sex. • Both sexes showed good compliance with the exercise protocol (HR target).The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

The effect of exercise on visceral fat in type 2 diabetes

Introduction: It is widely acknowledged that obesity increases cardiovascular and metabolic morbidity and mortality, and that visceral adipose tissue (VAT) is a major contributor to adverse cardiometabolic health in obesity-related type 2 diabetes. Although it is increasingly recognised that regular exercise has little effect on long-term weight loss, numerous investigations have reported a multiplicity of other benefits, including a reduction in VAT. A systematic review and meta-analysis was performed to assess the efficacy of exercise interventions on VAT area/volume in overweight and obese adults with type 2 diabetes. Methods: Relevant databases were searched to February 2016. Inclusion criteria included randomised controlled studies in which aerobic exercise training (AEx) or progressive resistance training (PRT) was used exclusively, or in combination for a minimum period of 4 weeks. Studies were selected if computed tomography or magnetic resonance imagining were used for the quantification of VAT area/volume pre- and post-intervention. Results: The original search included 7,588 studies, of which 15 were selected based on the eligibility criteria. After the removal of outliers, a significant pooled effect size (ES) was found for the comparison between AEx and control (-0.23, 95%CI:-0.43 to –0.03; P=0.026), but not for the comparison between PRT and control (-0.13, 95%CI:-0.37 to 0.12; P=0.307) or combination therapy and control (-0.11, 95%CI:-0.36 to 0.13 P=0.374). Conclusion: When compared with a control intervention, AEx therapy is effective for lowering VAT. Conversely, when compared with control, PRT in isolation or in combination with AEx may not reduce VAT. These data suggest that AEx is more efficacious for reducing VAT in overweight/obese populations with type 2 diabetes. Due to the small sample size of multi-modal and resistance training interventions, further investigation is needed to determine the efficacy of these therapies for VAT benefit