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 feasibility of implementing high-intensity interval training in cardiac rehabilitation settings: A retrospective analysis

Background: Cardiovascular disease is the leading cause of death worldwide. Notwithstanding the well-known benefits of cardiac rehabilitation (CR), adherence to CR remains low, particularly in women. High-intensity interval training (HIIT) has received specific attention as an emerging exercise-training paradigm that addresses frequently cited barriers to CR (i.e. lack of motivation/enjoyment and time, perceiving exercise regime as tiring/boring) and improves cardiovascular risk factors. Previous studies have examined the safety of HIIT in CR; there is little evidence on the feasibility of HIIT in CR. The aims of this study were to evaluate the feasibility of HIIT within a CR setting and examine the sex differences regarding the feasibility of such programming. Methods: Patients attended an on-site HIIT CR program (10-min warm-up, 25&thinsp;min of interspersed high-intensity [HI - 4&thinsp;min at 85&ndash;95% HRpeak] and lower intensity [LO - 3&thinsp;min at 60&ndash;70% HRpeak] intervals, 10-min cool-down) twice weekly for 10&thinsp;weeks. Heart rate (HR) and the Borg rating of perceived exertion (RPE) scale (6&ndash;20 points) were recorded at each session. Feasibility was assessed by: [1] attendance and compliance: the number of sessions attended and the compliance to the prescribed HI and LO HR ranges; [2] the patient experience: patients&rsquo; perceived effort, program difficulty, if the program was challenging and satisfying; and, [3] safety. Descriptive statistics were used to report the means and their variations. Mann-Whitney U tests and Chi-square analyses were performed to examine sex-differences. Results: A total of 151 patients (33% women, 57.5&thinsp;&plusmn;&thinsp;9.1&thinsp;years) attended the HIIT program and completed 16&thinsp;&plusmn;&thinsp;5 classes with a low attrition rate (11.3%). Most patients met or exceeded the prescribed target HR for the HI (80%) and LO (84%) intervals, respectively. Patients reported a &ldquo;somewhat hard&rdquo; RPE for HI (14&thinsp;&plusmn;&thinsp;2 points) and &ldquo;very light&rdquo; for LO (10&thinsp;&plusmn;&thinsp;2 points) intervals. All patients were satisfied with the program and found it challenging. Most patients found HIIT to be difficult (7&thinsp;&plusmn;&thinsp;2 points, scale range 0&ndash;10 points), yet safe (97%). Three vasovagal episodes occurred and more women dropped-out of the program than men (p&thinsp;&lt;&thinsp;0.01). Conclusions: HIIT is a feasible, safe and well-received exercise paradigm in a CR setting

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

Exercise Strategies For Targeting Central Arterial Stiffness, Central Haemodynamics And Cardiovascular Risk Factors In Diabetes

Chapter 1: reviews the literature regarding “traditional” cardiovascular risk factors, central arterial stiffness and central haemodynamics, and their cardiovascular health implications and assessment methods. The pathology of arterial stiffness and hypertension and the utility of exercise as a therapy for reducing arterial stiffness and central haemodynamics in adults is critically reviewed. Chapter 2: reports a systematic review and meta-analysis examing the effect of high intensity interval training (HIIT) and moderate intensity continuous training (MICT) on arterial stiffness and 24 h blood pressure. HIIT was superior to MICT for improving 24 h blood pressure outcomes. Chapter 3: presents the findings of an acute study on the effect of HIIT versus MICT versus control on central arterial stiffness and haemodynamics in adults with diabetes. A significant and near-significant group x time interaction was observed in central systolic blood pressure and arterial stiffness, respectively. Chapter 4: reports a systematic review and meta-analysis examining the effect of regular exercise versus control on arterial stiffness and vascular function in adults with T2D. Aerobic exercise significantly improves endothelium independent dilation and a near-significant reduction in pulse wave velocity. Chapter 5: presents the findings of an 12-week randomised, placebo-controlled trial on the efficacy of MICT and low volume HIIT compared to a sham-exercise placebo control on central arterial stiffness and central haemodynamics, as well as other cardiovascular risk factors in inactive, obese adults with type 2 diabetes. No significant changes were observed in central arterial stiffness and central haemodynamics. Chapter 6: summarises the key findings from all of the Chapters in this thesis. This chapter also addresses limitations of the thesis, proposes implications of these results for clinical practice, as well as future directions for research

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

Effects of Age and Playing Position on Field-Based Physical Fitness Measures in Adolescent Female Netball Players

This cross-sectional study investigated the impact of age and playing position, controlling for maturity, on physical fitness indicators in 303 adolescent female netball players aged 12.0 to 15.9 years. Assessments included estimated maximal oxygen uptake (VO2max) via the 20 m shuttle run test, 10 m and 20 m sprints, change of direction speed (CODS) using the 505 test, and muscle power via the medicine ball chest throw (MBCT) and countermovement vertical jump (CMJ). Participants were grouped by age (12 to 15 years) and playing position (non-circle and circle players), with age at peak height velocity as a covariate for maturity. Results revealed that, at 15 years, CMJ height was greater than at 12 years and 13 years (p 2 = 0.048). MBCT distance increased across age groups (p 2 = 0.323). Age had no impact on sprints, VO2max, or CODS. Non-circle players outperformed circle players in the 10 m sprint (p = 0.042, partial η2 = 0.016) and 20 m sprints (p = 0.010, partial η2 = 0.025) and displayed higher VO2max (p 2 = 0.036). Circle players were taller (p = 0.046, partial η2 = 0.014) and heavier (p 2 = 0.040) than non-circle players. Playing positions showed no differences in CMJ and MBCT. In adolescent female netball players, only muscle power is influenced by age, while non-circle players exhibit superior aerobic fitness and speed compared to circle players. Coaches may be able to utilize the distinct age and playing position traits of adolescent netballers to inform player selection and design targeted training programs