Cardiometabolic and immune response to exercise training in patients with metabolic syndrome: retrospective analysis of two randomized clinical trials.

Background: Metabolic syndrome (MetS) is defined by the presence of central obesity plus ≥two metabolic/cardiovascular risk factors (RF), with inflammation being a major disease-driving mechanism. Structured endurance exercise training (ET) may positively affect these traits, as well as cardiorespiratory fitness (V̇O2peak). Aims: We explore individual ET-mediated improvements of MetS-associated RF in relation to improvements in V̇O2peak and inflammatory profile. Methods: MetS patients from two randomized controlled trials, ExMET (n = 24) and OptimEx (n = 34), had performed 4- or 3-months supervised ET programs according to the respective trial protocol. V̇O2peak, MetS-defining RFs (both RCTs), broad blood leukocyte profile, cytokines and plasma proteins (ExMET only) were assessed at baseline and follow-up. Intra-individual changes in RFs were analysed for both trials separately using non-parametric approaches. Associations between changes in each RF over the exercise period (n-fold of baseline values) were correlated using a non-parametrical approach (Spearman). RF clustering was explored by uniform manifold approximation and projection (UMAP) and changes in RF depending on other RF or exercise parameters were explored by recursive partitioning. Results: Four months of ET reduced circulating leukocyte counts (63.5% of baseline, P = 8.0e-6), especially effector subtypes. ET response of MetS-associated RFs differed depending on patients' individual RF constellation, but was not associated with individual change in V̇O2peak. Blood pressure lowering depended on cumulative exercise duration (ExMET: ≥102 min per week; OptimEx-MetS: ≥38 min per session) and baseline triglyceride levels (ExMET: <150 mg/dl; OptimEx-MetS: <174.8 mg/dl). Neuropilin-1 plasma levels were inversely associated with fasting plasma triglycerides (R: -0.4, P = 0.004) and changes of both parameters during the ET phase were inversely correlated (R: -0.7, P = 0.0001). Conclusions: ET significantly lowered effector leukocyte blood counts. The improvement of MetS-associated cardiovascular RFs depended on individual basal RF profile and exercise duration but was not associated with exercise-mediated increase in V̇O2peak. Neuropilin-1 may be linked to exercise-mediated triglyceride lowering.

Acute effects of high intensity training on cardiac function: a pilot study comparing subjects with type 2 diabetes to healthy controls.

This study evaluated acute cardiac stress after a high-intensity interval training session in patients with type 2 diabetes (T2D) versus healthy controls. High intensity aerobic exercise was performed by 4 × 4-min intervals (90-95% of maximal heart rate), followed by a ramp protocol to peak oxygen uptake. Echocardiography was performed before and 30 min after exercise. Holter electrocardiography monitored heart rhythms 24 h before, during, and 24 h after the exercise. Left atrial end-systolic volume, peak early diastolic mitral annular velocity, and the ratio of peak early to late diastolic mitral inflow velocity were reduced by approximately 18%, 15%, and 31%, respectively, after exercise across groups. Left ventricular end-diastolic wall thickness was the only echo parameter that significantly differed between groups in response to exercise. The T2D group had a rate of supraventricular extrasystoles per hour that was 265% greater than that of the controls before exercise, which remained higher after exercise. A single exhaustive exercise session impaired left ventricular diastolic function in both groups. The findings also indicated impaired right ventricular function in patients with T2D after exercise.ClinicalTrials.gov Identifier: NCT02998008.

Effect of Carbohydrate Content in a Pre-event Meal on Endurance Performance-Determining Factors: A Randomized Controlled Crossover-Trial.

The current study aimed to investigate the effect of the relative CHO content in a pre-event meal on time to exhaustion (TTE), peak oxygen uptake ( V ∙ O 2 peak ), the 2nd lactate threshold (LT2), onset of blood lactate accumulation (OBLA), and work economy (WE) and to compare responses between well-trained and recreationally trained individuals. Eleven well-trained and 10 recreationally trained men performed three trials in a randomized cross-over design, in which they performed exercise tests (1) after a high-CHO pre-event meal (3 g · kg-1), (2) a low-CHO pre-event meal (0.5 g · kg-1), or (3) in a fasted-state. The test protocol consisted of five submaximal 5-min constant-velocity bouts of increasing intensity and a graded exercise test (GXT) to measure TTE. A repeated measure ANOVA with a between-subjects factor (well-trained vs. recreational) was performed. A main effect of pre-event meal was found (p = 0.001), with TTE being 8.0% longer following the high-CHO meal compared to the fasted state (p = 0.009) and 7.2% longer compared to the low-CHO meal (p = 0.010). No significant effect of pre-event meal on V ∙ O 2 peak , LT2, OBLA, or WE (p ≥ 0.087) was found and no significant interaction effect between training status and pre-event CHO intake was found for TTE or any of the performance-determining variables (p ≥ 0.257). In conclusion, high-CHO content in the pre-event meal led to a longer TTE compared to a meal with a low-CHO content or exercising in a fasted state, both in well-trained and recreationally trained participants. However, the underlying physiological reason for the increased TTE is unclear, as no effect of pre-event meal on the main physiological performance-determining variables was found. Thus, pre-event CHO intake should be standardized when the goal is to assess endurance performance but seems to be of less importance when assessing the main performance-determining variables.

Effects of High-Intensity Interval Training After Stroke (The HIIT Stroke Study) on Physical and Cognitive Function: A Multicenter Randomized Controlled Trial.

OBJECTIVE: To assess the effects of high-intensity interval training (HIIT) on physical, mental, and cognitive functioning after stroke. DESIGN: The HIIT Stroke Study was a single-blind, multicenter, parallel-group randomized controlled trial. SETTING: Specialized rehabilitation units at 3 Norwegian hospitals. PARTICIPANTS: Adult stroke survivors (N=70) 3 months to 5 years after a first-ever stroke. Mean age was 57.6±9.2 years and 58.7±9.2 years in the intervention and control groups, respectively. INTERVENTIONS: Participants were randomized to standard care in combination with 4×4 minutes of treadmill HIIT at 85%-95% of peak heart rate or standard care only. OUTCOMES: Outcomes were measured using physical, mental, and cognitive tests and the FIM and Stroke Impact Scale. Linear mixed models were used to analyze differences between groups at posttest and 12-month follow-up. RESULTS: The intervention group showed a significant treatment effect (95% confidence interval [CI]) from baseline to posttest on a 6-minute walk test of 28.3 (CI, 2.80-53.77) meters (P=.030); Berg Balance Scale 1.27 (CI, 0.17-2.28) points (P=.025); and Trail Making Test Part B (TMT-B; -24.16 [CI, -46.35 to -1.98] s, P=.033). The intervention group showed significantly greater improvement on TMT-B at the 12-month follow-up (25.44 [CI, -49.01 to -1.87] s, P=.035). The control group showed significantly greater improvement in total Functional Independence Measure score with a treatment effect of -2.37 (CI, -4.30 to -0.44) points (P=.016) at 12-month follow-up. No significant differences were identified between groups on other outcomes at any time point. CONCLUSIONS: HIIT combined with standard care improved walking distance, balance, and executive function immediately after the intervention compared with standard care only. However, only TMT-B remained significant at the 12-month follow-up.

The Inclusion of Sprints in Low-Intensity Sessions During the Transition Period of Elite Cyclists Improves Endurance Performance 6 Weeks Into the Subsequent Preparatory Period.

PURPOSE: To investigate the effects of including repeated sprints in a weekly low-intensity (LIT) session during a 3-week transition period on cycling performance 6 weeks into the subsequent preparatory period (PREP) in elite cyclists. METHODS: Eleven elite male cyclists (age = 22.0 [3.8] y, body mass = 73.0 [5.8] kg, height = 186 [7] cm, maximal oxygen uptake [VO2max] = 5469 [384] mL·min-1) reduced their training load by 64% and performed only LIT sessions (CON, n = 6) or included 3 sets of 3 × 30-second maximal sprints in a weekly LIT session (SPR, n = 5) during a 3-week transition period. There was no difference in the reduction in training load during the transition period between groups. Physiological and performance measures were compared between the end of the competitive period and 6 weeks into the PREP. RESULTS: SPR demonstrated a 7.3% (7.2%) improvement in mean power output during a 20-minute all-out test at PREP, which was greater than CON (-1.3% [4.6%]) (P = .048). SPR had a corresponding 7.0% (3.6%) improvement in average VO2 during the 20-minute all-out test, which was larger than the 0.7% (6.0%) change in CON (P = .042). No change in VO2max, gross efficiency, or power output at blood lactate concentration of 4 mmol·L-1 from competitive period to PREP occurred in either group. CONCLUSION: Including sprints in a weekly LIT session during the transition period of elite cyclists provided a performance advantage 6 weeks into the subsequent PREP, which coincided with a higher performance VO2.

The Effect of Exercise Intensity and Volume on Metabolic Phenotype in Patients with Metabolic Syndrome: A Randomized Controlled Trial.

Background: Moderate intensity continuous training (MICT) ameliorates dysmetabolism in patients with metabolic syndrome (MetS). The impact of low- (1HIIT) versus high-volume high-intensity interval training (4HIIT) versus MICT on central adiposity, insulin resistance, and atherogenic dyslipidemia in patients with MetS has not yet been reported. Methods: Twenty-nine patients with MetS according to International Diabetes Federation criteria (nine females, age 61 ± 5 years, body mass index 31.1 ± 3.7 kg/m2, waist circumference (WC) ♀ 102.2 ± 10.6 cm, ♂ 108.5 ± 8.6 cm) were randomized (1:1:1) to 16 weeks of (1) MICT (5 × 30 min/week, 35%-50% heart rate reserve (HRR), (2) 1HIIT (3 × 17 min/week incl. 4 min @80%-90% HRR), and (3) 4HIIT (3 × 38 min/week incl. 4 × 4 min @80%-90% HRR). Peak oxygen uptake (V̇O2peak), WC and anthropometric/metabolic indices indicative of MetS, fasting glucose/insulin, Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), dyslipidemia, and respiratory exchange ratio (RER) at warm-up were quantified at baseline and study completion. Analysis of variance and paired t tests were used for statistical analysis. Analyses were performed after checking for parametric distribution. Results: There were no significant differences between groups in waist-to-height ratio (♀: Δ -0.10 ± -0.05, ♂: Δ -0.08 ± -0.06, P = 0.916), WC (♀: Δ -1.4 ± -0.1 cm, ♂: Δ 0.1 ± 0.9 cm, P = 0.590), fasting glucose (Δ -1.18 ± 16.7 µU/mL, P = 0.773), fasting insulin (Δ 0.76 ± 13.4 µU/mL, P = 0.509), HOMA-IR (Δ 0.55 ± 4.1, P = 0.158), atherogenic dyslipidemia [triglycerides (TAG) Δ -10.1 ± 46.9 mg/dL, P = 0.468, high-density lipoprotein cholesterol (HDL-C) Δ 1.5 ± 5.4, P = 0.665, TAG/HDL-C -0.19 ± 1.3, P = 0.502], V̇O2peak (P = 0.999), or RER (P = 0.842). In the entire group, waist-to-height-ratio and V̇O2peak significantly improved by a clinically meaningful amount (Δ 2.7 ± 0.9 mL/min/kg; P < 0.001) and RER at warm-up significantly decreased (Δ -0.03 ± 0.06, P = 0.039). Conclusion: In patients with MetS, there was no significant difference between HIIT, irrespective of volume, to MICT for improving exercise capacity or metabolic health.

Effects of High-Intensity Interval Training After Stroke (the HIIT-Stroke Study): A Multicenter Randomized Controlled Trial.

OBJECTIVE: To examine if 8 weeks of high-intensity interval training (HIIT) in addition to standard care would increase and maintain peak oxygen uptake (Vo2peak) more than standard care alone in patients with stroke. DESIGN: This was a single-blind, multicenter, parallel group, randomized controlled trial. SETTING: Specialized rehabilitation units at 3 Norwegian hospitals. PARTICIPANTS: Participants (N=70), 3 months to 5 years after first-ever stroke, were randomly assigned to the intervention group (n=36) or the control group (n=34); 42% were women, mean age was 57.6±9.3 years, mean time post stroke was 26.4±14.5 months. INTERVENTION: The intervention was 8 weeks: 3 times a week with HIIT treadmill training with work periods of 4 × 4 minutes at 85%-95% of peak heart rate interspersed with 3 minutes of active recovery at 50%-70% of peak heart rate. The control group received standard care according to national guidelines. OUTCOMES: The primary outcome, analyzed by intention-to-treat, was Vo2peak measured as liters per minute 12 months after inclusion. Secondary outcome measures were blood pressure and blood profile. RESULTS: Mean baseline Vo2peak was 2.63±1.08 L·min-1 vs 2.87±0.71 L·min-1, while at 12 months Vo2peak was 2.70±1.00 L·min-1 vs 2.67±0.76 L·min-1 (P=.068) in the intervention and control groups, respectively. There was a significant and greater improvement in the intervention group compared with the control group at 12 months in 3 of 6 secondary outcomes from the peak test but no significant differences for blood pressure or blood profile. CONCLUSIONS: The HIIT intervention, which was well-tolerated in this sample of well-functioning survivors of stroke, was not superior to standard care in improving and maintaining Vo2peak at the 12-month follow-up. However, secondary results from the peak test showed a significant improvement from before to immediately after the intervention.

ß2 adrenergic interaction and cardiac autonomic function: effects of aerobic training in overweight/obese individuals.

PURPOSE: To verify the influence of different volumes and intensities of aerobic exercise on cardiac autonomic function (CAF) through heart rate variability (HRV) analysis as well the influence of ß2 adrenergic receptor (ADRB2) variants in overweight/obese individuals. METHODS: 70 physically inactive adults were randomly allocated into the following 16-week training: 1-high-intensity interval training (HIIT) (n = 25, 1 × 4 min bout at 85-95%HR peak, 3×/week), 4-HIIT (n = 26, 4 × 4 min bouts at 85-95%HR peak, interspersed with 3 min of recovery at 50-70%HR peak, 3×/week), and moderate continuous training (MCT) (n = 19, 30 min at 60-70%HR peak, 5×/week). Before and after the exercise training, anthropometric, BP, cardiorespiratory fitness, and HRV measures were evaluated. R-R intervals recorded for 10 min in a supine position at pre- and post-intervention were used to analyze HRV in the plot-Poincare indexes (SD1, SD2), and frequency-domain (LF, HF, LF/HF). Full blood samples were used for genotyping. RESULTS: 4-HIIT and MCT showed positive outcomes for almost all variables while 1-HIIT had a positive influence only on SBP and SD2 index. No associations were observed between isolated ADRB2 variants and changes in HRV. In the analysis of the interaction genotypes, all groups responded positively for the SD1 index of HRV and only the H1 (GG and CC) and H2 (GG and CG + GG) groups presented increases in the RMSSD index. Furthermore, there was an increase in the LF index only in the H3 (CC and AA + AG) and H4 (AA + AG and CG + GG) groups. CONCLUSIONS: ADRB2 variants and aerobic exercise training are important interacting variables to improve autonomic function and other health variables outcomes in overweight or obese individuals.

Comparison of Mitochondrial Respiration in M. triceps brachii and M. vastus lateralis Between Elite Cross-Country Skiers and Physically Active Controls.

RATIONALE: The main purposes of this study were to compare mitochondrial respiration in M. triceps brachii and M. vastus lateralis between elite cross-country (XC) skiers and physically active controls (CON), and to explore the associations between mitochondrial respiration in these muscles and peak oxygen uptake ( V ˙ O2peak) in arm- and leg-dominant exercise modes. METHODS: Thirteen male elite XC skiers (age: 25 ± 4; peak oxygen uptake ( V ˙ O2peak): 75.5 ± 4.2 mL⋅kg-1⋅min-1) and twelve CON (age: 26 ± 3; V ˙ O2peak: 57.2 ± 6.4 mL⋅kg-1⋅min-1) had microbiopsies taken from M. vastus lateralis and M. triceps brachii, which were analyzed for various measures of mitochondrial respiration using high-resolution respirometry. Thereafter, all participants tested V ˙ O2peak in both running (RUN) and upper body poling (UBP). RESULTS: XC skiers had generally higher mitochondrial respiration in M. triceps brachii compared to CON (P < 0.001), whereas no significant group-differences in mitochondrial respiration in M. vastus lateralis were revealed. XC skiers had higher mitochondrial respiration in M. triceps brachii compared to M. vastus lateralis (P = 0.005-0.058), whereas in CON, most mitochondrial respiration measures were higher in M. vastus lateralis than in M. triceps brachii (P < 0.01). When all athletes were pooled, there was a strong positive correlation between V ˙ O2peak in UBP and mitochondrial respiration in M. triceps brachii on several measures (P < 0.01), whereas no correlation was found for RUN. CONCLUSION: The higher mitochondrial respiration found in M. triceps brachii compared to M. vastus lateralis among our elite XC skiers demonstrates the potential for the arm muscles to adapt to aerobic endurance training. The opposite pattern found in CON, clearly showed lower mitochondrial respiration in M. triceps brachii compared to XC skiers, whereas respiration in M. vastus lateralis did not differ between groups. The strong positive correlation between mitochondrial respiration in M. triceps brachii and V ˙ O2peak in UBP indicate that arm muscles' respiratory function may be a limiting factor for V ˙ O2peak in arm-dominant exercise modes.

EX-MET study: exercise in prevention on of metabolic syndrome - a randomized multicenter trial: rational and design.

BACKGROUND: Metabolic syndrome substantially increases risk of cardiovascular events. It is therefore imperative to develop or optimize ways to prevent or attenuate this condition. Exercise training has been long recognized as a corner-stone therapy for reducing individual cardiovascular risk factors constituting the metabolic syndrome. However, the optimal exercise dose and its feasibility in a real world setting has yet to be established. The primary objective of this randomized trial is to investigate the effects of different volumes of aerobic interval training (AIT) compared to the current exercise guideline of moderate-intensity continuous training (MICT) on the composite number of cardiovascular disease risk factors constituting the metabolic syndrome after a 16 week, 1-year, and 3-year follow-up. METHODS: This is a randomized international multi-center trial including men and women aged ≥30 years diagnosed with the metabolic syndrome according to the International Diabetes Federation criteria. Recruitment began in August 2012 and concluded in December 2016. This trial consists of supervised and unsupervised phases to evaluate the efficacy and feasibility of different exercise doses on the metabolic syndrome in a real world setting. This study aims to include and randomize 465 participants to 3 years of one of the following training groups: i) 3 times/week of 4 × 4 min AIT at 85-95% peak heart rate (HRpeak); ii) 3 times/week of 1 × 4 min AIT at 85-95% HRpeak; or iii) 5-7 times/week of ≥30 min MICT at 60-70% HRpeak. Clinical examinations, physical tests and questionnaires are administered to all participants during all testing time points (baseline, 16 weeks and after 1-, and 3-years). DISCUSSION: This multi-center international trial indeed aims to ease the burden in healthcare/economic cost arising from treating end-stage CVD related conditions such as stroke and myocardial infarction, that could eventually emerge from the metabolic syndrome condition. TRIAL REGISTRATION: Clinical registration number: NCT01676870 , ClinicalTrials.gov (August 31, 2012).

Oxygen uptake during functional activities after stroke-Reliability and validity of a portable ergospirometry system.

BACKGROUND: People with stroke have a low peak aerobic capacity and experience increased effort during performance of daily activities. The purpose of this study was to examine test-retest reliability of a portable ergospirometry system in people with stroke during performance of functional activities in a field-test. Secondary aims were to examine the proportion of oxygen consumed during the field-test in relation to the peak-test and to analyse the correlation between the oxygen uptake during the field-test and peak-test in order to support the validity of the field-test. METHODS: With simultaneous measurement of oxygen consumption, participants performed a standardized field-test consisting of five activities; walking over ground, stair walking, stepping over obstacles, walking slalom between cones and from a standing position lifting objects from one height to another. All activities were performed in self-selected speed. Prior to the field-test, a peak aerobic capacity test was performed. The field-test was repeated minimum 2 and maximum 14 days between the tests. ICC2,1 and Bland Altman tests (Limits of Agreement, LoA) were used to analyse test-retest reliability. RESULTS: In total 31 participants (39% women, mean (SD) age 54.5 (12.7) years and 21.1 (14.3) months' post-stroke) were included. The ICC2,1 was ≥ 0.80 for absolute V̇O2, relative V̇O2, minute ventilation, CO2, respiratory exchange ratio, heart rate and Borgs rating of perceived exertion. ICC2,1 for total time to complete the field-test was 0.99. Mean difference in steady state V̇O2 during Test 1 and Test 2 was -0.40 (2.12) The LoAs were -3.75 and 4.51. Participants spent 60.7% of their V̇O2peak performing functional activities. Correlation between field-test and peak-test was 0.689, p = 0.001 for absolute and 0.733, p = 0.001 for relative V̇O2. CONCLUSIONS: This study presents first evidence on reliability of oxygen uptake during performance of functional activities after stroke, showing very good test-retest reliability. The secondary analysis showed that the amount of energy spent during the field-test relative to the peak-test was high and the correlation between the two test was good, supporting the validity of this method.

Effects of exercise intensity and nutrition advice on myocardial function in obese children and adolescents: a multicentre randomised controlled trial study protocol.

INTRODUCTION: The prevalence of paediatric obesity is increasing, and with it, lifestyle-related diseases in children and adolescents. High-intensity interval training (HIIT) has recently been explored as an alternate to traditional moderate-intensity continuous training (MICT) in adults with chronic disease and has been shown to induce a rapid reversal of subclinical disease markers in obese children and adolescents. The primary aim of this study is to compare the effects of HIIT with MICT on myocardial function in obese children and adolescents. METHODS AND ANALYSIS: Multicentre randomised controlled trial of 100 obese children and adolescents in the cities of Trondheim (Norway) and Brisbane (Australia). The trial will examine the efficacy of HIIT to improve cardiometabolic outcomes in obese children and adolescents. Participants will be randomised to (1) HIIT and nutrition advice, (2) MICT and nutrition advice or (3) nutrition advice. Participants will partake in supervised exercise training and/or nutrition sessions for 3 months. Measurements for study end points will occur at baseline, 3 months (postintervention) and 12 months (follow-up). The primary end point is myocardial function (peak systolic tissue velocity). Secondary end points include vascular function (flow-mediated dilation assessment), quantity of visceral and subcutaneous adipose tissue, myocardial structure and function, body composition, cardiorespiratory fitness, autonomic function, blood biochemistry, physical activity and nutrition. Lean, healthy children and adolescents will complete measurements for all study end points at one time point for comparative cross-sectional analyses. ETHICS AND DISSEMINATION: This randomised controlled trial will generate substantial information regarding the effects of exercise intensity on paediatric obesity, specifically the cardiometabolic health of this at-risk population. It is expected that communication of results will allow for the development of more effective evidence-based exercise prescription guidelines in this population while investigating the benefits of HIIT on subclinical markers of disease. TRIAL REGISTRATION NUMBER: NCT01991106.

Aerobic Interval Training Reduces the Burden of Atrial Fibrillation in the Short Term: A Randomized Trial.

BACKGROUND: Exercise training is an effective treatment for important atrial fibrillation (AF) comorbidities. However, a high level of endurance exercise is associated with an increased AF prevalence. We assessed the effects of aerobic interval training (AIT) on time in AF, AF symptoms, cardiovascular health, and quality of life in AF patients. METHODS AND RESULTS: Fifty-one patients with nonpermanent AF were randomized to AIT (n=26) consisting of four 4-minute intervals at 85% to 95% of peak heart rate 3 times a week for 12 weeks or to a control group (n=25) continuing their regular exercise habits. An implanted loop recorder measured time in AF continuously from 4 weeks before to 4 weeks after the intervention period. Cardiac function, peak oxygen uptake (o2peak), lipid status, quality of life, and AF symptoms were evaluated before and after the 12-week intervention period. Mean time in AF increased from 10.4% to 14.6% in the control group and was reduced from 8.1% to 4.8% in the exercise group (P=0.001 between groups). AF symptom frequency (P=0.006) and AF symptom severity (P=0.009) were reduced after AIT. AIT improved o2peak, left atrial and ventricular ejection fraction, quality-of-life measures of general health and vitality, and lipid values compared with the control group. There was a trend toward fewer cardioversions and hospital admissions after AIT. CONCLUSIONS: AIT for 12 weeks reduces the time in AF in patients with nonpermanent AF. This is followed by a significant improvement in AF symptoms, o2peak, left atrial and ventricular function, lipid levels, and QoL. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT01325675.

High-intensity interval training improves obstructive sleep apnoea.

BACKGROUND: Three hours per week of vigorous physical activity is found to be associated with reduced odds of sleep-disordered breathing. AIM: To investigate whether 12 weeks of high-intensity interval training (HIIT) reduced the apnoea-hypopnea index (AHI) in obese subjects with moderate-to-severe obstructive sleep apnoea. METHODS: In a prospective randomised controlled exercise study, 30 (body mass index 37±6 kg/m2, age 51±9 years) patients with sleep apnoea (AHI 41.5±25.3 events/hour) were randomised 1:1 to control or 12 weeks of supervised HIIT (4×4 min of treadmill running or walking at 90%-95% of maximal heart rate two times per week). RESULTS: In the HIIT group, the AHI was reduced by 7.5±11.6 events/hour (within-group p<0.05), self-reported sleepiness (Epworth scale) improved from 10.0±3.6 to 7.3±3.7 (between-group p<0.05) and maximal oxygen uptake improved from 28.2±7.4 to 30.2±7.7 mL/kg/min (between-group p<0.05) from baseline to 12 weeks. The AHI, self-reported sleepiness and VO2maxwere unchanged from baseline to 12 weeks in controls (baseline AHI 50.3±25.5 events/hour, Epworth score 5.9±4.3, maximal oxygen uptake 27.0±6.8 mL/kg/min). Body weight remained unchanged in both groups. CONCLUSION: Twelve weeks of HIIT improved the AHI and self-reported daytime sleepiness in subjects with obese sleep apnoea without any change in the desaturation index and body weight.

The impact of high-intensity interval training versus moderate-intensity continuous training on vascular function: a systematic review and meta-analysis.

BACKGROUND: Vascular dysfunction is a precursor to the atherosclerotic cascade, significantly increasing susceptibility to cardiovascular events such as myocardial infarction or stroke. Previous studies have revealed a strong relationship between vascular function and cardiorespiratory fitness (CRF). Thus, since high-intensity interval training (HIIT) is a potent method of improving CRF, several small randomized trials have investigated the impact on vascular function of HIIT relative to moderate-intensity continuous training (MICT). OBJECTIVE: The aim of this study was to systematically review the evidence and quantify the impact on vascular function of HIIT compared with MICT. METHODS: Three electronic databases (PubMed, Embase, and MEDLINE) were searched (until May 2014) for randomized trials comparing the effect of at least 2 weeks of HIIT and MICT on vascular function. HIIT protocols involved predominantly aerobic exercise at a high intensity, interspersed with active or passive recovery periods. We performed a meta-analysis to compare the mean difference in the change in vascular function assessed via brachial artery flow-mediated dilation (FMD) from baseline to post-intervention between HIIT and MICT. The impact of HIIT versus MICT on CRF, traditional cardiovascular disease (CVD) risk factors, and biomarkers associated with vascular function (oxidative stress, inflammation, and insulin resistance) was also reviewed across included studies. RESULTS: Seven randomized trials, including 182 patients, met the eligibility criteria and were included in the meta-analysis. A commonly used HIIT prescription was four intervals of 4 min (4 × 4 HIIT) at 85-95% of maximum or peak heart rate (HRmax/peak), interspersed with 3 min of active recovery at 60-70% HRmax/peak, three times per week for 12-16 weeks. Brachial artery FMD improved by 4.31 and 2.15% following HIIT and MICT, respectively. This resulted in a significant (p < 0.05) mean difference of 2.26%. HIIT also had a greater tendency than MICT to induce positive effects on secondary outcome measures, including CRF, traditional CVD risk factors, oxidative stress, inflammation, and insulin sensitivity. CONCLUSION: HIIT is more effective at improving brachial artery vascular function than MICT, perhaps due to its tendency to positively influence CRF, traditional CVD risk factors, oxidative stress, inflammation, and insulin sensitivity. However, the variability in the secondary outcome measures, coupled with the small sample sizes in these studies, limits this finding. Nonetheless, this review suggests that 4 × 4 HIIT, three times per week for at least 12 weeks, is a powerful form of exercise to enhance vascular function.

Sport-Specific Physiological Adaptations in Highly Trained Endurance Athletes.

PURPOSE: This study aims to compare maximal oxygen uptake (V˙O2max), blood volume (BV), hemoglobin mass (Hbmass), and brachial endothelial function, measured as flow-mediated dilatation (FMD), in international-level endurance athletes primarily exercising with the whole body (cross-country skiing), lower body (orienteering), or upper body (flatwater kayak). METHODS: Seventeen cross-country skiers, 15 orienteers, and 11 flatwater kayakers were tested for V˙O2max, BV, Hbmass, and FMD. Additionally, body composition and annual training (type, volume, and intensity of training) were analyzed. RESULTS: Absolute and body-mass-normalized V˙O2max values were 11.3% and 9.9% higher, respectively, in skiers (5.83 ± 0.60 L·min and 77.9 ± 4.2 mL·min·kg) compared to orienteers (5.24 ± 0.45 L·min and 70.9 ± 3.5 mL·min·kg) (P < 0.01), whereas kayakers (5.78 ± 0.56 L·min and 73.7 ± 6.3 mL·min·kg) did not differ from skiers. BV was 9.9%-11.8% higher in skiers and orienteers compared to kayakers when normalized for total body mass and fat-free mass, and skiers had 9.2% and 9.9% higher Hbmass normalized for total body mass and fat-free mass compared to kayakers (all P < 0.05). Arterial diameter was 11.8%-15.0% larger in kayakers (4.38 ± 0.63 mm) and skiers (4.22 ± 0.36 mm) compared to orienteers (3.81 ± 0.32 mm) (P < 0.05), whereas FMD did not differ between groups. CONCLUSIONS: This study indicates that higher V˙O2max in cross-country skiers and greater arterial diameters in the arms of skiers and kayakers are sport-specific physiological adaptations to chronic endurance training in whole-body and upper-body exercise modes. However, variations in these variables are not associated with BV or Hbmass.

Effects of acute supplementation of L-arginine and nitrate on endurance and sprint performance in elite athletes.

This study examined the effects of acute supplementation with L-arginine and nitrate on running economy, endurance and sprint performance in endurance-trained athletes. In a randomised cross-over, double-blinded design we compared the effects of combined supplementation with 6 g L-arginine and 614 mg nitrate against 614 mg nitrate alone and placebo in nine male elite cross-country skiers (age 18 ± 0 years, VO2max 69.3 ± 5.8 ml ⋅ min(-1) ⋅ kg(-1)). After a 48-hour standardisation of nutrition and exercise the athletes were tested for plasma nitrate and nitrite concentrations, blood pressure, submaximal running economy at 10 km ⋅ h(-1) and 14 km ⋅ h(-1) at 1% incline and 180 m as well as 5-km time-trial running performances. Plasma nitrite concentration following L-arginine + nitrate supplementation (319 ± 54 nmol ⋅ L(-1)) did not differ from nitrate alone (328 ± 107 nmol ⋅ L(-1)), and both were higher than placebo (149 ± 64 nmol ⋅ L(-1), p < 0.01). There were no differences in physiological responses during submaximal running or in 5-km performance between treatments. The plasma nitrite concentrations indicate greater nitric oxide availability both following acute supplementation of L-arginine + nitrate and with nitrate alone compared to placebo, but no additional effect was revealed when L-arginine was added to nitrate. Still, there were no effects of supplementation on exercise economy or endurance running performance in endurance-trained cross-country skiers.

Effect of 24 sessions of high-intensity aerobic interval training carried out at either high or moderate frequency, a randomized trial.

PURPOSE: The training response of an intensified period of high-intensity exercise is not clear. Therefore, we compared the cardiovascular adaptations of completing 24 high-intensity aerobic interval training sessions carried out for either three or eight weeks, respectively. METHODS: Twenty-one healthy subjects (23.0±2.1 years, 10 females) completed 24 high-intensity training sessions throughout a time-period of either eight weeks (moderate frequency, MF) or three weeks (high frequency, HF) followed by a detraining period of nine weeks without any training. In both groups, maximal oxygen uptake (VO2max) was evaluated before training, at the 9(th) and 17(th) session and four days after the final 24(th) training session. In the detraining phase VO2max was evaluated after 12 days and thereafter every second week for eight weeks. Left ventricular echocardiography, carbon monoxide lung diffusion transfer factor, brachial artery flow mediated dilatation and vastus lateralis citrate maximal synthase activity was tested before and after training. RESULTS: The cardiovascular adaptation after HF training was delayed compared to training with MF. Four days after ending training the HF group showed no improvement (+3.0%, p = 0.126), whereas the MF group reached their highest VO2max with a 10.7% improvement (p<0.001: group difference p = 0.035). The HF group reached their highest VO2max (6.1% increase, p = 0.026) twelve days into the detraining period, compared to a concomitant reduction to 7.9% of VO2max (p<0.001) above baseline in the MF group (group difference p = 0.609). CONCLUSION: Both HF and MF training of high-intensity aerobic exercise improves VO2max. The cardiovascular adaptation following a HF programme of high-intensity exercise is however delayed compared to MF training. TRIAL REGISTRATION: ClinicalTrials.gov NCT00733941.

Low- and high-volume of intensive endurance training significantly improves maximal oxygen uptake after 10-weeks of training in healthy men.

UNLABELLED: Regular exercise training improves maximal oxygen uptake (VO2max), but the optimal intensity and volume necessary to obtain maximal benefit remains to be defined. A growing body of evidence suggests that exercise training with low-volume but high-intensity may be a time-efficient means to achieve health benefits. In the present study, we measured changes in VO2max and traditional cardiovascular risk factors after a 10 wk. training protocol that involved three weekly high-intensity interval sessions. One group followed a protocol which consisted of 4×4 min at 90% of maximal heart rate (HRmax) interspersed with 3 min active recovery at 70% HRmax (4-AIT), the other group performed a single bout protocol that consisted of 1×4 min at 90% HRmax (1-AIT). Twenty-six inactive but otherwise healthy overweight men (BMI: 25-30, age: 35-45 y) were randomized to either 1-AIT (n = 11) or 4-AIT (n = 13). After training, VO2max increased by 10% (∼5.0 mL⋅kg(-1)⋅min(-1)) and 13% (∼6.5 mL⋅kg(-1)⋅min(-1)) after 1-AIT and 4-AIT, respectively (group difference, p = 0.08). Oxygen cost during running at a sub-maximal workload was reduced by 14% and 13% after 1-AIT and 4-AIT, respectively. Systolic blood pressure decreased by 7.1 and 2.6 mmHg after 1-AIT and 4-AIT respectively, while diastolic pressure decreased by 7.7 and 6.1 mmHg (group difference, p = 0.84). Both groups had a similar ∼5% decrease in fasting glucose. Body fat, total cholesterol, LDL-cholesterol, and ox-LDL cholesterol only were significantly reduced after 4-AIT. Our data suggest that a single bout of AIT performed three times per week may be a time-efficient strategy to improve VO2max and reduce blood pressure and fasting glucose in previously inactive but otherwise healthy middle-aged individuals. The 1-AIT type of exercise training may be readily implemented as part of activities of daily living and could easily be translated into programs designed to improve public health. TRIAL REGISTRATION: ClinicalTrials.govNCT00839579.

Aerobic exercise training improves right- and left ventricular systolic function in patients with COPD.

OBJECTIVE: The aim of this study was to investigate the effects of moderate continuous training (MCT) and high intensity aerobic interval training (AIT) on systolic ventricular function and aerobic capacity in COPD patients. METHODS: Seventeen patients with COPD (64 ± 8 years, 12 men) with FEV1 of 52.8 ± 11% of predicted, were randomly assigned to isocaloric programs of MCT at 70% of max heart rate (HR) for 47 minutes) or AIT (~90% of max HR for 4×4 minutes) three times per week for 10 weeks. Baseline cardiac function was compared with 17 age- and sex-matched healthy individuals. Peak oxygen uptake (VO(2-peak)) and left (LV) and right ventricular (RV) function examined by echocardiography, were measured at baseline and after 10 weeks of training. RESULTS: At baseline, the COPD patients had reduced systolic function compared to healthy controls (p < 0.05). After the training, AIT and MCT increased VO(2-peak) by 8% and 9% and work economy by 7% and 10%, respectively (all p < 0.05). LV and RV systolic function both improved (p < 0.05), with no difference between the groups after the two modes of exercise training. Stroke volume increased by 17% and 20%, LV systolic tissue Doppler velocity (S') by 18% and 17% and RV S' by 15% after AIT and MCT, respectively (p < 0.05). CONCLUSION: Systolic cardiac function is reduced in COPD. Both AIT and MCT improved systolic cardiac function. In contrast to other patient groups studied, higher exercise intensity does not seem to have additional effects on cardiac function or aerobic capacity in COPD patients.