Effect of low-volume combined aerobic and resistance high-intensity interval training on vascular health in people with type 2 diabetes: a randomised controlled trial.

PURPOSE: We compared the effects of low-volume combined aerobic and resistance high-intensity interval training (C-HIIT), combined moderate-intensity continuous training (C-MICT) and waitlist control (CON) on vascular health after 8-weeks of supervised training, and an additional 10-months of self-directed training, in adults with type 2 diabetes (T2D). METHODS: Sixty-nine low active adults with T2D were randomised to 8-weeks of supervised C-HIIT (3 times/week, 78-min/week), C-MICT (current exercise guidelines, 4 times/week, 210-min/week) or CON. CON underwent usual care for 8-weeks before being re-randomised to C-HIIT or C-MICT. This was followed by 10-months of self-directed training for participants in C-HIIT and C-MICT. Vascular outcomes were evaluated at baseline, 8-weeks, and 12-months. RESULTS: After 8-weeks, supervised C-HIIT significantly improved relative flow-mediated dilation (FMD) compared with CON (mean difference [MD] 0.8% [0.1, 1.4], p = 0.025). Although not significantly different from CON, the magnitude of change in relative FMD following 8-weeks of supervised C-MICT was similar (MD 0.8% [-0.1, 1.7], p = 0.080). There were no differences in haemodynamic indices, carotid-femoral pulse wave velocity (cfPWV), or aortic reservoir pressure between groups at 8-weeks. After 12-months, there was a significant reduction in haemodynamic indices (time effect, p < 0.05) for both C-HIIT and C-MICT, with no between-group difference. The reduction in cfPWV over 12-months was significantly greater in C-MICT than C-HIIT (group × time effect, p = 0.018). There was no difference in FMD over time or between groups at 12-months. CONCLUSIONS: Short-term supervised C-HIIT and C-MICT both increased brachial artery FMD compared with CON. Long-term C-HIIT and C-MICT were beneficial for improving haemodynamic indices, but not brachial artery FMD. C-MICT was superior to C-HIIT for improving cfPWV at 12-months. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry Identifier ACTRN12615000475549.

Genome wide association study of response to interval and continuous exercise training: the Predict-HIIT study.

BACKGROUND: Low cardiorespiratory fitness (V̇O2peak) is highly associated with chronic disease and mortality from all causes. Whilst exercise training is recommended in health guidelines to improve V̇O2peak, there is considerable inter-individual variability in the V̇O2peak response to the same dose of exercise. Understanding how genetic factors contribute to V̇O2peak training response may improve personalisation of exercise programs. The aim of this study was to identify genetic variants that are associated with the magnitude of V̇O2peak response following exercise training. METHODS: Participant change in objectively measured V̇O2peak from 18 different interventions was obtained from a multi-centre study (Predict-HIIT). A genome-wide association study was completed (n = 507), and a polygenic predictor score (PPS) was developed using alleles from single nucleotide polymorphisms (SNPs) significantly associated (P < 1 × 10-5) with the magnitude of V̇O2peak response. Findings were tested in an independent validation study (n = 39) and compared to previous research. RESULTS: No variants at the genome-wide significance level were found after adjusting for key covariates (baseline V̇O2peak, individual study, principal components which were significantly associated with the trait). A Quantile-Quantile plot indicates there was minor inflation in the study. Twelve novel loci showed a trend of association with V̇O2peak response that reached suggestive significance (P < 1 × 10-5). The strongest association was found near the membrane associated guanylate kinase, WW and PDZ domain containing 2 (MAGI2) gene (rs6959961, P = 2.61 × 10-7). A PPS created from the 12 lead SNPs was unable to predict V̇O2peak response in a tenfold cross validation, or in an independent (n = 39) validation study (P > 0.1). Significant correlations were found for beta coefficients of variants in the Predict-HIIT (P < 1 × 10-4) and the validation study (P < × 10-6), indicating that general effects of the loci exist, and that with a higher statistical power, more significant genetic associations may become apparent. CONCLUSIONS: Ongoing research and validation of current and previous findings is needed to determine if genetics does play a large role in V̇O2peak response variance, and whether genomic predictors for V̇O2peak response trainability can inform evidence-based clinical practice. Trial registration Australian New Zealand Clinical Trials Registry (ANZCTR), Trial Id: ACTRN12618000501246, Date Registered: 06/04/2018, http://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=374601&isReview=true .

Similar Morphological and Functional Training Adaptations Occur Between Continuous and Intermittent Blood Flow Restriction.

ABSTRACT: Davids, CJ, Raastad, T, James, L, Gajanand, T, Smith, E, Connick, M, McGorm, H, Keating, S, Coombes, JS, Peake, JM, and Roberts, LA. Similar morphological and functional training adaptations occur between continuous and intermittent blood flow restriction. J Strength Cond Res 35(7): 1784-1793, 2021-The aim of the study was to compare skeletal muscle morphological and functional outcomes after low-load resistance training using 2 differing blood flow restriction (BFR) protocols. Recreationally active men and women (n = 42 [f = 21], 24.4 ± 4.4 years) completed 21 sessions over 7 weeks of load-matched and volume-matched low-load resistance training (30% 1 repetition maximum [1RM]) with either (a) no BFR (CON), (b) continuous BFR (BFR-C, 60% arterial occlusion pressure [AOP]), or (c) intermittent BFR (BFR-I, 60% AOP). Muscle mass was assessed using peripheral quantitative computed tomography before and after training. Muscular strength, endurance, and power were determined before and after training by assessing isokinetic dynamometry, 1RM, and jump performance. Ratings of pain and effort were taken in the first and final training session. An alpha level of p < 0.05 was used to determine significance. There were no between-group differences for any of the morphological or functional variables. The muscle cross sectional area (CSA) increased pre-post training (p = 0.009; CON: 1.6%, BFR-C: 1.1%, BFR-I: 2.2%). Maximal isometric strength increased pre-post training (p < 0.001; CON: 9.6%, BFR-C: 14.3%, BFR-I: 19.3%). Total work performed during an isokinetic endurance task increased pre-post training (p < 0.001, CON: 3.6%, BFR-C: 9.6%, BFR-I: 11.3%). Perceptions of pain (p = 0.026) and effort (p = 0.033) during exercise were higher with BFR-C; however, these reduced with training (p = 0.005-0.034). Overall, these data suggest that when 30% 1RM loads are used with a frequency of 3 times per week, the addition of BFR does not confer superior morphological or functional adaptations in recreationally active individuals. Furthermore, the additional metabolic stress that is proposed to occur with a continuous BFR protocol does not seem to translate into proportionally greater training adaptations. The current findings promote the use of both intermittent BFR and low-load resistance training without BFR as suitable alternative training methods to continuous BFR. These approaches may be practically applicable for those less tolerable to pain and discomfort associated with ischemia during exercise.

Low-volume combined aerobic and resistance high-intensity interval training in type 2 diabetes: a randomised controlled trial.

Objective: The objective of this study was to compare the effects of novel, time-efficient, low-volume combined aerobic and resistance high-intensity interval training (C-HIIT), and current exercise guidelines (210 min/week of combined moderate-intensity continuous training (C-MICT)), with waitlist control (CON) on glycaemic control in people with type 2 diabetes mellitus (T2D). Methods: Sixty-nine low-active people with T2D were randomised to 8 weeks of supervised C-HIIT (78 min/week), supervised C-MICT (210 min/week), or waitlist CON. Those in waitlist CON were re-randomised to supervised C-HIIT/C-MICT at week 8. Following 8 weeks of supervised training, participants completed 10 months of self-directed exercise. Outcomes were assessed at baseline, week 8 and month 12. Participants in waitlist CON were only included in the exercise groups for the month 12 analysis. Analyses were completed using intention-to-treat analysis of covariance (n=69; week 8) and linear mixed modelling (n=63; month 12). Results: Compared with CON, at week 8, HbA1c decreased in C-HIIT (adjusted mean difference: -0.7% (95% CI -1.3, -0.2%)) and C-MICT (-1.2% (-1.9, -0.6%)). There were also improvements in C-HIIT and C-MICT versus CON at week 8 for fat mass (-1.9 (-3.1, -0.6) and -1.5 (-2.6, -0.4) kg, respectively), lean mass (1.5 (0.8, 2.3) and 0.9 (0.1, 1.7) kg), and exercise capacity (124 (77, 171) and 49 (5, 93) s). At month 12, adherence was low, and most measures returned to baseline. Conclusions: Low-volume C-HIIT (78 min/week) and C-MICT (210 min/week) improved glycaemic control, body composition and exercise capacity similarly over 8 weeks in people with T2D. However, at month 12, improvements were not maintained following self-directed exercise. Regardless, these data suggest that supervised low-volume C-HIIT is a time-efficient and effective strategy for improving outcomes in T2D.

Efficacy of two doses of external counterpulsation (ECP) on glycemic control in people with type 2 diabetes mellitus: A randomized SHAM-controlled trial.

AIMS: To determine the efficacy of two doses of external counterpulsation (ECP) on glycemic control in people with type 2 diabetes mellitus (T2D), and any persistent benefits 7 weeks following treatment. METHODS: 50 participants with T2D were randomly assigned to either 1) 20x45-minute ECP sessions over 7 weeks (ECP45), 2) 20x30-minute ECP sessions over 7 weeks (ECP30) or 3) SHAM control. Outcomes were assessed at baseline, after 7 weeks of the intervention and 7 weeks after the interventions finished. Efficacy was determined from changes in HbA1c. RESULTS: After 7 weeks, there were significant between-group differences, with ECP45 lowering HbA1c compared to SHAM (mean [95% CI] -0.7 [-0.1 to -1.3] %; -7 [-1 to -15] mmol/mol). Within group changes were; ECP45 (mean ± SD -0.8 ± 0.8%; -8 ± 8 mmol/mol), ECP30 (-0.2 ± 0.5%; -2 ± 6 mmol/mol) and SHAM (-0.1 ± 0.9%; -1 ± 10 mmol/mol). HbA1c in the ECP45 group remained lower 7 weeks after completing the intervention; ECP45 (7.0 ± 1.1%; 53 ± 26 mmol/mol), ECP30 (7.7 ± 1.4%; 60 ± 16 mmol/mol) and SHAM (7.7 ± 1.0%; 60 ± 10 mmol/mol). CONCLUSIONS: In people with T2D, ECP45 for 7 weeks improved glycemic control when compared to ECP30 and a SHAM control group.

Effects of fitness and fatness on age-related arterial stiffening in people with type 2 diabetes.

People with type 2 diabetes (T2D) are at a greater risk of cardiovascular disease than the general population. Both non-modifiable (age) and modifiable (low aerobic fitness, high body fatness) factors are separately predictive of cardiovascular risk, although they often occur concomitantly. This study aimed to examine the (1) association between age and arterial stiffness, a subclinical marker of cardiovascular risk; and (2) effects of body fatness and aerobic fitness on age-related increases in arterial stiffness in people with T2D. Data from 64 individuals with T2D (age 59.8 ± 8.7 years, 40% female, HbA1c 8.4 ± 1.6%) were included in this cross-sectional analysis. Carotid-femoral pulse wave velocity (cfPWV) was used to quantify arterial stiffness. Aerobic fitness (relative V̇O2peak ) was determined via indirect calorimetry during maximal exercise testing. Central body fatness was determined using waist circumference. Data were analysed using hierarchical multiple regressions. After adjustment for sex and duration of T2D, each one standard deviation (SD) increase in age (8.68 years) was associated with a 0.63 m·s-1 increase in cfPWV (ß = 0.416, p = 0.001). Following adjustment for aerobic fitness and body fatness, the standardized ß was unchanged (0.417). A one SD increase in waist circumference (13.9 cm) and relative V̇O2peak (5.3 ml·kg-1 ·min-1 ) were associated with a similar magnitude of difference in cfPWV (0.47 m·s-1 and -0.44 m·s-1 , respectively). Therefore, age is a significant correlate of increased arterial stiffness in T2D, with higher aerobic fitness attenuating, and higher body fatness exacerbating, this increase. Interventions aimed at improving cardiovascular outcomes in people with T2D should target both increased aerobic fitness and reduced body fatness.

Alterations to neuromuscular properties of skeletal muscle are temporally dissociated from the oxygen uptake slow component.

To assess if the alteration of neuromuscular properties of knee extensors muscles during heavy exercise co-vary with the SCV ([Formula: see text] slow component), eleven healthy male participants completed an incremental ramp test to exhaustion and five constant heavy intensity cycling bouts of 2, 6, 10, 20 and 30 minutes. Neuromuscular testing of the knee extensor muscles were completed before and after exercise. Results showed a significant decline in maximal voluntary contraction (MVC) torque only after 30 minutes of exercise (-17.01% ± 13.09%; p < 0.05) while single twitch (PT), 10 Hz (P10), and 100 Hz (P100) doublet peak torque amplitudes were reduced after 20 and 30 minutes (p < 0.05). Voluntary activation (VA) and M-wave were not affected by exercise, but significant correlation was found between the SCV and PT, MVC, VA, P10, P100, and P10/P100 ratio, respectively (p < 0.015). Therefore, because the development of the SCV occurred mainly between 2-10 minutes, during which neuromuscular properties were relatively stable, and because PT, P10 and P100 were significantly reduced only after 20-30 minutes of exercise while SCV is stable, a temporal relationship between them does not appear to exist. These results suggest that the development of fatigue due to alterations of neuromuscular properties is not an essential requirement to elicit the SCV.

Effect of different exercise training intensities on musculoskeletal and neuropathic pain in inactive individuals with type 2 diabetes - Preliminary randomised controlled trial.

AIMS: People with type 2 diabetes (T2D) have a greater prevalence of musculoskeletal and neuropathic pain. This exploratory analysis investigated whether exercise of different intensities leads to changes in self-reported musculoskeletal pain or symptoms of diabetic neuropathy in inactive individuals with type 2 diabetes. METHODS: Thirty-two inactive adults with T2D (59% male, mean age 58.7 ± 9.1yrs, median HbA1c 7.8%) were randomised to usual care (CON), supervised combined aerobic and resistance moderate-intensity continuous training (C-MICT), or supervised combined high-intensity interval training (C-HIIT). At baseline and 8-weeks, musculoskeletal and neuropathic pain were evaluated using a modified Nordic Musculoskeletal Questionnaire and the Neuropathy Total Symptom Score-6 respectively. Quantitative sensory testing was used to determine thermal, mechanical and vibration detection thresholds, as well as pain pressure thresholds. Adverse events were recorded throughout the intervention. RESULTS: Compared to CON, reduction in musculoskeletal pain intensity was significantly greater for C-HIIT (MD -5.4, 95% CI [-10.6 to -0.2], p = 0.04) and non-significantly greater for C-MICT (MD -5.9 [-12.4 to 0.7], p = 0.08). Changes in neuropathy symptoms were not different between C-HIIT and CON (MD 1.0 [-0.9 to 2.8], p = 0.31), or C-MICT and CON (MD 0.2 [-3.1 to 3.6], p = 0.89). No differences in sensory function were observed between groups. Similar rates of adverse events were seen in both exercise interventions (19 C-HIIT; 17 C-MICT), all but one of which were mild. CONCLUSIONS: Preliminary data suggests 8-weeks of high-intensity combined aerobic and resistance exercise may be safely prescribed for inactive individuals with T2D and may reduce musculoskeletal pain but not neuropathic symptoms. TRIAL REGISTRATION: ACTRN12615000475549.

The metabolic profiles of different fiber type populations under the emergence of the slow component of oxygen uptake.

To investigate the influence of different metabolic muscle fiber profiles on the emergence of the slow component of oxygen uptake ([Formula: see text]SC), 12 habitually active males completed four sessions of different combinations of work-to-work transition exercises up to severe intensity. Each transition was modeled to analyze the different kinetic parameters. Using a new approach, combining Henneman's principle and superposition principle, a reconstructed kinetics was built by temporally aligning the start of each new transition and summing them. The primary phase time constant significantly slowed and the gain at the end (GainEnd) significantly increased when transitions started from a higher intensity (p < 0.001). Kinetic parameters from the reconstructed curve ([Formula: see text], time delay of primary phase, [Formula: see text]End and GainEnd) were not significantly different from one transition to severe exercise. These results suggest that the appearance of the [Formula: see text]SC is at least related to, if not the result of, the different metabolic properties of muscle fibers.

Comparing the Efficacy of Supervised and Unsupervised Exercise Training on Glycaemic Control in Type 2 Diabetes: A Systematic Review.

BACKGROUND: Exercise training is vital for glycaemic control in patients with type 2 diabetes mellitus (T2D). While the positive effects of supervised exercise training are well established, unsupervised training may offer an alternative and more sustainable means of realising the benefits of exercise away from a resource-heavy supervised setting. OBJECTIVE: To evaluate the available literature and compare the efficacy of supervised and unsupervised exercise training programs on glycemic control in patients with T2D. METHODS: CINAHL, MEDLINE, PubMed, and EMBASE, searched from inception to 20 July 2018. Only studies that included both supervised and unsupervised training were included. RESULTS: Four studies, involving 115 participants, were included. One compared supervised with unsupervised exercise training and three investigated the efficacy of unsupervised training following supervised training. While supervised training is effective for improving glycaemic control in patients with T2D, unsupervised training may not maintain these changes. Included studies lacked detail relating to the supervised and unsupervised training programs. CONCLUSIONS: Given that exercise is a critical component for maintenance of glycaemic control in patients with T2D, and because unsupervised training has been shown to be effective in improving clinical outcomes in other disease populations, further research is warranted to compare supervised and unsupervised exercise training in patients with T2D. It is important that future studies report standardised and detailed descriptions of key elements that form the basis of supervised and unsupervised exercise training groups.

A Multi-Center Comparison of O2peak Trainability Between Interval Training and Moderate Intensity Continuous Training.

There is heterogeneity in the observed O2peak response to similar exercise training, and different exercise approaches produce variable degrees of exercise response (trainability). The aim of this study was to combine data from different laboratories to compare O2peak trainability between various volumes of interval training and Moderate Intensity Continuous Training (MICT). For interval training, volumes were classified by the duration of total interval time. High-volume High Intensity Interval Training (HIIT) included studies that had participants complete more than 15 min of high intensity efforts per session. Low-volume HIIT/Sprint Interval Training (SIT) included studies using less than 15 min of high intensity efforts per session. In total, 677 participants across 18 aerobic exercise training interventions from eight different universities in five countries were included in the analysis. Participants had completed 3 weeks or more of either high-volume HIIT (n = 299), low-volume HIIT/SIT (n = 116), or MICT (n = 262) and were predominately men (n = 495) with a mix of healthy, elderly and clinical populations. Each training intervention improved mean O2peak at the group level (P < 0.001). After adjusting for covariates, high-volume HIIT had a significantly greater (P < 0.05) absolute O2peak increase (0.29 L/min) compared to MICT (0.20 L/min) and low-volume HIIT/SIT (0.18 L/min). Adjusted relative O2peak increase was also significantly greater (P < 0.01) in high-volume HIIT (3.3 ml/kg/min) than MICT (2.4 ml/kg/min) and insignificantly greater (P = 0.09) than low-volume HIIT/SIT (2.5 mL/kg/min). Based on a high threshold for a likely response (technical error of measurement plus the minimal clinically important difference), high-volume HIIT had significantly more (P < 0.01) likely responders (31%) compared to low-volume HIIT/SIT (16%) and MICT (21%). Covariates such as age, sex, the individual study, population group, sessions per week, study duration and the average between pre and post O2peak explained only 17.3% of the variance in O2peak trainability. In conclusion, high-volume HIIT had more likely responders to improvements in O2peak compared to low-volume HIIT/SIT and MICT.