An investigation into the optimal wear time criteria necessary to reliably estimate physical activity and sedentary behaviour from ActiGraph wGT3X+ accelerometer data in older care home residents.

BACKGROUND: Research protocols regarding the use of ActiGraph wGT3X+ accelerometers in care home residents are yet to be established. The purpose of this study was to identify the minimal wear time criteria required to achieve reliable estimates of physical activity (PA) and sedentary behaviour (SB) in older care home residents. METHODS: Ninety-four older adults from 14 care homes wore an ActiGraph wGT3X+ accelerometer on the right hip for 7 consecutive days. A pragmatic, staged approach was adopted in order to explore the effect of: monitoring day; minimum daily wear time and number of wear days on estimates of four outcomes derived from the accelerometer data: counts.day- 1, counts.minute- 1, PA time and SB time. RESULTS: Data from 91 participants (mean age: 84 ± 9 years, 34% male) was included in the analysis. No effect of monitoring day was observed. Lowering the daily wear time to ≥ 8 h (compared to ≥10 h) had no effect on the outcomes of interest. Four days of monitoring was sufficient to provide reliable estimates of all four outcomes. CONCLUSION: In this study, a minimum wear time criterion of ≥ 8 h on any 4 days was required to derive reliable estimates of PA and SB from ActiGraph wGT3X+ accelerometer data in older care home residents.

Omega-3 polyunsaturated fatty acid supplementation versus placebo on vascular health, glycaemic control, and metabolic parameters in people with type 1 diabetes: a randomised controlled preliminary trial.

BACKGROUND: The role of omega-3 polyunsaturated fatty acids (n-3PUFA), and the potential impact of n-3PUFA supplementation, in the treatment and management of type 1 diabetes (T1D) remains unclear and controversial. Therefore, this study aimed to examine the efficacy of daily high-dose-bolus n-3PUFA supplementation on vascular health, glycaemic control, and metabolic parameters in subjects with T1D. METHODS: Twenty-seven adults with T1D were recruited to a 6-month randomised, double-blind, placebo-controlled trial. Subjects received either 3.3 g/day of encapsulated n-3PUFA or encapsulated 3.0 g/day corn oil placebo (PLA) for 6-months, with follow-up at 9-months after 3-month washout. Erythrocyte fatty acid composition was determined via gas chromatography. Endpoints included inflammation-associated endothelial biomarkers (vascular cell adhesion molecule-1 [VCAM-1], intercellular adhesion molecule-1 [ICAM-1], E-selectin, P-selectin, pentraxin-3, vascular endothelial growth factor [VEGF]), and their mediator tumor necrosis factor alpha [TNFα] analysed via immunoassay, vascular structure (carotid intima-media thickness [CIMT]) and function (brachial artery flow mediated dilation [FMD]) determined via ultrasound technique, blood pressure, glycosylated haemoglobin (HbA1c), fasting plasma glucose (FPG), and postprandial metabolism. RESULTS: Twenty subjects completed the trial in full. In the n-3PUFA group, the mean ± SD baseline n-3PUFA index of 4.93 ± 0.94% increased to 7.67 ± 1.86% (P < 0.001) after 3-months, and 8.29 ± 1.45% (P < 0.001) after 6-months. Total exposure to n-3PUFA over the 6-months (area under the curve) was 14.27 ± 3.05% per month under n-3PUFA, and 9.11 ± 2.74% per month under PLA (P < 0.001). VCAM-1, ICAM-1, E-selectin, P-selectin, pentraxin-3, VEGF, TNFα, CIMT, FMD, blood pressure, HbA1c, FPG, and postprandial metabolism did not differ between or within groups after treatment (P > 0.05). CONCLUSIONS: This study indicates that daily high-dose-bolus of n-3PUFA supplementation for 6-months does not improve vascular health, glucose homeostasis, or metabolic parameters in subjects with T1D. The findings from this preliminary RCT do not support the use of therapeutic n-3PUFA supplementation in the treatment and management of T1D and its associated complications. Trial Registration ISRCTN, ISRCTN40811115. Registered 27 June 2017, http://www.isrctn.com/ISRCTN40811115 .

Blood Orange Juice Consumption Increases Flow-Mediated Dilation in Adults with Overweight and Obesity: A Randomized Controlled Trial.

BACKGROUND: Epidemiological studies have indicated an inverse association between citrus fruit consumption and cardiovascular disease (CVD) risk. There is, however, a paucity of data concerning effects of blood orange juice (BOJ) intake on endothelial function and cardiovascular risk biomarkers. OBJECTIVES: We examined short-term effects of BOJ on endothelial function, blood pressure, lipid profile, and inflammatory markers in healthy participants of European origin who were overweight or obese. METHODS: In a randomized, controlled, single-blind, crossover trial, 15 men and women (age: 28.7 ± 6.5 y; BMI: 28.3 ± 3.1 kg/m2) consumed BOJ or a sugar-matched control drink (CD) (200 mL twice daily) for 2 wk with a washout period of 1 wk. Endothelial function, measured as flow-mediated dilation (FMD) (primary outcome), and the secondary outcomes blood pressure, anthropometric measures, lipid profile, inflammatory markers, markers of vasodilation and vasoconstriction, and urinary flavanone metabolites were evaluated prior to and at the end of each treatment period following an overnight fast. Changes between treatments over time were assessed using repeated-measures ANOVA. RESULTS: The results demonstrate a significant increase in FMD following BOJ consumption (pre: 8.15% ± 2.92%; post: 10.2% ± 3.31%; P = 0.002) compared with CD (pre: 8.11% ± 2.52%; post: 7.77% ± 2.43%; time × treatment interaction: P = 0.001). Concurrent significant increases in urinary hesperetin-3'-glucuronide and hesperetin-7-glucuronide were observed following BOJ supplementation only (time × treatment interaction: P ≤ 0.01). Baseline blood pressure, lipid profile, high-sensitivity C-reactive protein, and endothelin-1 were generally within healthy ranges and unaffected by the intervention. CONCLUSIONS: A 2-wk consumption of BOJ exerted favorable effects on endothelial function in healthy women and men who were overweight or obese, which is likely mediated by the combined actions of anthocyanin and flavanone metabolites on mechanisms that contribute to enhancing NO bioavailability. This trial was registered at clinicaltrials.gov as NCT03611114.

Omega-3 polyunsaturated fatty acids favourably modulate cardiometabolic biomarkers in type 2 diabetes: a meta-analysis and meta-regression of randomized controlled trials.

BACKGROUND: Randomized controlled trials (RCTs) suggest that supplementation with omega-3 polyunsaturated fatty acids (n-3PUFAs) may favourably modify cardiometabolic biomarkers in type 2 diabetes (T2DM). Previous meta-analyses are limited by insufficient sample sizes and omission of meta-regression techniques, and a large number of RCTs have subsequently been published since the last comprehensive meta-analysis. Updated information regarding the impact of dosage, duration or an interaction between these two factors is therefore warranted. The objective was to comprehensively assess the effect of n-3PUFAs supplementation on cardiometabolic biomarkers including lipid profiles, inflammatory parameters, blood pressure, and indices of glycaemic control, in people with T2DM, and identify whether treatment dosage, duration or an interaction thereof modify these effects. METHODS: Databases including PubMed and MEDLINE were searched until 13th July 2017 for RCTs investigating the effect of n-3PUFAs supplementation on lipid profiles, inflammatory parameters, blood pressure, and indices of glycaemic control. Data were pooled using random-effects meta-analysis and presented as standardised mean difference (Hedges g) with 95% confidence intervals (95% CI). Meta-regression analysis was performed to investigate the effects of duration of supplementation and total dosage of n-3PUFAs as moderator variables where appropriate. RESULTS: A total of 45 RCTs were identified, involving 2674 people with T2DM. n-3PUFAs supplementation was associated with significant reductions in LDL [ES: - 0.10, (95% CI - 0.17, - 0.03); p = 0.007], VLDL (ES: - 0.26 (- 0.51, - 0.01); p = 0.044], triglycerides (ES: - 0.39 (- 0.55, - 0.24; p ≤ 0.001] and HbA1c (ES: - 0.27 (- 0.48, - 0.06); p = 0.010]. Moreover, n-3PUFAs supplementation was associated with reduction in plasma levels of TNF-α [ES: - 0.59 (- 1.17, - 0.01); p = 0.045] and IL-6 (ES: - 1.67 (- 3.14, - 0.20); p = 0.026]. All other lipid markers, indices of glycaemic control, inflammatory parameters, and blood pressure remained unchanged (p > 0.05). CONCLUSIONS: n-3PUFAs supplementation produces favourable hypolipidemic effects, a reduction in pro-inflammatory cytokine levels and improvement in glycaemia. Neither duration nor dosage appear to explain the observed heterogeneity in response to n-3PUFAs. Trial registration This trial was registered at http://www.crd.york.ac.uk as CRD42016050802.

Moderate and heavy metabolic stress interval training improve arterial stiffness and heart rate dynamics in humans.

Traditional continuous aerobic exercise training attenuates age-related increases of arterial stiffness, however, training studies have not determined whether metabolic stress impacts these favourable effects. Twenty untrained healthy participants (n = 11 heavy metabolic stress interval training, n = 9 moderate metabolic stress interval training) completed 6 weeks of moderate or heavy intensity interval training matched for total work and exercise duration. Carotid artery stiffness, blood pressure contour analysis, and linear and non-linear heart rate variability were assessed before and following training. Overall, carotid arterial stiffness was reduced (p < 0.01), but metabolic stress-specific alterations were not apparent. There was a trend for increased absolute high-frequency (HF) power (p = 0.10) whereas both absolute low-frequency (LF) power (p = 0.05) and overall power (p = 0.02) were increased to a similar degree following both training programmes. Non-linear heart rate dynamics such as detrended fluctuation analysis [Formula: see text] also improved (p > 0.05). This study demonstrates the effectiveness of interval training at improving arterial stiffness and autonomic function, however, the metabolic stress was not a mediator of this effect. In addition, these changes were also independent of improvements in aerobic capacity, which were only induced by training that involved a high metabolic stress.

Physical activity promotion interventions in chronic airways disease: a systematic review and meta-analysis.

Physical inactivity is common in people with chronic airways disease (pwCAD) and associated with worse clinical outcomes and impaired quality of life. We conducted a systematic review and meta-analysis to characterise and evaluate the effectiveness of interventions promoting step-based physical activity (PA) in pwCAD. We searched for studies that included a form of PA promotion and step-count outcome measure. A random-effects model was used to determine the overall effect size using post-intervention values. 38 studies (n=32 COPD; n=5 asthma; n=1 bronchiectasis; study population: n=3777) were included. Overall, implementing a form of PA promotion resulted in a significant increase in step-count: median (IQR) 705 (183-1210) when compared with usual standard care: -64 (-597-229), standardised mean difference (SMD) 0.24 (95% CI: 0.12-0.36), p<0.01. To explore the impact of specific interventions, studies were stratified into subgroups: PA promotion+wearable activity monitor-based interventions (n=17) (SMD 0.37, p<0.01); PA promotion+step-count as an outcome measure (n=9) (SMD 0.18, p=0.09); technology-based interventions (n=12) (SMD 0.16, p=0.01). Interventions promoting PA, particularly those that incorporate wearable activity monitors, result in a significant and clinically meaningful improvement in daily step-count in pwCAD.

Heavy and moderate interval exercise training alters low-flow-mediated constriction but does not increase circulating progenitor cells in healthy humans.

Moderate-intensity endurance exercise training improves vascular endothelial vasomotor function; however, the impact of high-intensity exercise training has been equivocal. Thus, the effect of the physiological stress of the exercise remains poorly understood. Furthermore, enhanced vascular repair mediated by circulating progenitor cells may also be improved. To address whether the physiological stress of exercise training is an important factor contributing to these adaptations, 20 healthy participants trained for 6 weeks. Training involved either moderate (MSIT; n = 9) or heavy metabolic stress (HSIT; n = 11) interval exercise training programmes matched for total work and duration of exercise. Before and after training, flow-mediated dilatation, low-flow-mediated constriction and total vessel reactivity were measured at the brachial artery using Doppler ultrasound. Circulating progenitor cells (CD34(+), CD133(+) and CD309/KDR(+)) were measured by flow cytometry (means ± SD). Relative (MSIT pre- 5.5 ± 3.4 versus post-training 6.6 ± 2.5%; HSIT pre- 6.6 ± 4.1 versus post-training 7.0 ± 3.4%, P = 0.33) and normalized (P = 0.16) flow-mediated dilatation did not increase with either training programme. However, low-flow-mediated constriction was greater after training in both groups (MSIT pre- -0.5 ± 3.2 versus post-training -1.9 ± 3.1%; HSIT pre- -1.0 ± 1.7 versus post-training -2.9 ± 3.0%, P = 0.04) and contributed to greater total vessel reactivity (MSIT pre- 7.4 ± 3.3 versus post-training 10.1 ± 3.7%; HSIT pre- 10.9 ± 5.9 versus post-training 12.7 ± 6.2%, P = 0.01). Peak reactive hyperaemia and the area under the shear rate curve were not different between groups, either before or after training. Although circulating progenitor cell numbers increased following heavy-intensity interval exercise training, variability was great amongst participants [MSIT pre- 16 ± 18 versus post-training 14 ± 12 cells (ml whole blood)(-1); HSIT pre- 8 ± 6 versus post-training 19 ± 23 cells (ml whole blood)(-1), P = 0.50]. Overall, vasoconstrictor function may be augmented by moderate- and heavy-intensity interval exercise training in young adults. However, circulating progenitor cell numbers were not increased, suggesting that these cells are not likely to be upregulated as a result of training.

Intraobserver reliability of two-dimensional ultrasound derived strain imaging in the assessment of the left ventricle, right ventricle, and left atrium of healthy human hearts.

AIMS: To determine the intraobserver reproducibility of peak and temporal values for myocardial strain (ɛ) and strain rate (SR) using a speckle tracking technique in the left ventricle (LV), right ventricle (RV), and left atrium (LA). METHODS AND RESULTS: Myocardial speckle tracking echocardiograms of the LV, RV, and LA were obtained on 20 healthy adults to provide indices of longitudinal, radial, circumferential ɛ, and SR as well as LV rotation and twist. Each participant had two separate acquisitions approximately 30 minutes apart. No systematic bias was present in ɛ data. LV ɛ across all planes provided "good" to "very good" intraclass correlation coefficient (ICC) values (0.714-0.807), however radial ɛ was inferior in terms of coefficients of variation (CoV) (19%). SR data were more variable than ɛ with LV radial SR performing least favorably. RV and LA ɛ demonstrated excellent reproducibility (ICCs of 0.834, 0.959, and CoVs of 7% and 6%, respectively). RV and LA SR were again more variable but generally acceptable ICC > 0.6 and CoV < 15%. Peak basal and apical rotation demonstrated quite high variability while derived torsion had low variability and excellent agreement (ICC = 0.940, CoV = 10%). Time-to-peak values demonstrated acceptable agreement with the exception of systolic SR from all chambers. CONCLUSION: Good reproducibility was obtained for peak ɛ indices although radial ɛ performs less favorably. Intraobserver variation of peak ɛ appears superior to values obtained for peak SR. Time-to-peak values demonstrate very good intraobserver reproducibility across all planes of contraction with exception of (time-to-peak) systolic strain rate (SRS).

Efficacy of interval exercise training to improve vascular health in sedentary postmenopausal females.

BACKGROUND: Menopause represents a turning point where vascular damage begins to outweigh reparative processes, leading to increased cardiovascular disease (CVD) risk. Exercise training reduces CVD risk in postmenopausal females via improvements in traditional risk factors and direct changes to the vasculature. We assessed the effect of moderate (MODERATE-IT) versus heavy (HEAVY-IT) intensity interval exercise training upon markers of cardiovascular health and vascular repair in postmenopausal females. METHODS: Twenty-seven healthy postmenopausal females (56 ± 4 yr) were assigned to 12 weeks of either MODERATE-IT or HEAVY-IT, twice per week. MODERATE-IT consisted of 10s work, and 10s active recovery repeated for 30 min. HEAVY-IT comprised 30s work, and 30s active recovery repeated for 21 ± 2 min. Endothelial function (flow-mediated dilation), arterial stiffness (pulse wave velocity), and V̇O2peak were assessed pre-training and post-training. Blood samples were obtained pre-training and post-training for enumeration of circulating angiogenic cells (CACs), culture of CACs, and lipoprotein profile. RESULTS: V̇O2peak increased 2.4 ± 2.8 ml/kg/min following HEAVY-IT only (p < 0.05). Brachial blood pressure and endothelial function were unchanged with exercise training (p > 0.05). Peripheral pulse wave velocity reduced 8% with exercise training, irrespective of intensity (p < 0.05). Exercise training had no effect on lipoprotein profile or endothelin-1 (p > 0.05). CAC adhesion to vascular smooth muscle cells (VSMC) increased 30 min post plating following MODERATE-IT only (p < 0.05). CONCLUSIONS: HEAVY-IT was more effective at increasing V̇O2peak in postmenopausal females. The ability of CACs to adhere to VSMC improved following MODERATE-IT but not HEAVY-IT. Interval training had the same effect on endothelial function (no change) and arterial stiffness (reduced), regardless of exercise intensity.

Atrial fibrillation and risk of progressive heart failure in patients with preserved ejection fraction heart failure.

AIMS: Understanding of the pathophysiology of progressive heart failure (HF) in patients with heart failure with preserved ejection fraction (HFpEF) is incomplete. We sought to identify factors differentially associated with risk of progressive HF death and hospitalization in patients with HFpEF compared with patients with HF and reduced ejection fraction (HFrEF). METHODS AND RESULTS: Prospective cohort study of patients newly referred to secondary care with suspicion of HF, based on symptoms and signs of HF and elevated natriuretic peptides (NP), followed up for a minimum of 6 years. HFpEF and HFrEF were diagnosed according to the 2016 European Society of Cardiology guidelines. Of 960 patients referred, 467 had HFpEF (49%), 311 had HFrEF (32%), and 182 (19%) had neither. Atrial fibrillation (AF) was found in 37% of patients with HFpEF and 34% with HFrEF. During 6 years follow-up, 19% of HFrEF and 14% of HFpEF patients were hospitalized or died due to progressive HF, hazard ratio (HR) 0.67 (95% CI: 0.47-0.96; P = 0.028). AF was the only marker that was differentially associated with progressive HF death or hospitalization in patients with HFpEF HR 2.58 (95% CI: 1.59-4.21; P < 0.001) versus HFrEF HR 1.11 (95% CI: 0.65-1.89; P = 0.7). CONCLUSIONS: De novo patients diagnosed with HFrEF have greater risk of death or hospitalization due to progressive HF than patients with HFpEF. AF is associated with increased risk of progressive HF death or hospitalization in HFpEF but not HFrEF, raising the intriguing possibility that this may be a novel therapeutic target in this growing population.

Human exercise-induced circulating progenitor cell mobilization is nitric oxide-dependent and is blunted in South Asian men.

OBJECTIVE: Circulating progenitor cells (CPC) have emerged as potential mediators of vascular repair. In experimental models, CPC mobilization is critically dependent on nitric oxide (NO). South Asian ethnicity is associated with reduced CPC. We assessed CPC mobilization in response to exercise in Asian men and examined the role of NO in CPC mobilization per se. METHODS AND RESULTS: In 15 healthy, white European men and 15 matched South Asian men, CPC mobilization was assessed during moderate-intensity exercise. Brachial artery flow-mediated vasodilatation was used to assess NO bioavailability. To determine the role of NO in CPC mobilization, identical exercise studies were performed during intravenous separate infusions of saline, the NO synthase inhibitor L-NMMA, and norepinephrine. Flow-mediated vasodilatation (5.8%+/-0.4% vs 7.9%+/-0.5%; P=0.002) and CPC mobilization (CD34(+)/KDR(+) 53.2% vs 85.4%; P=0.001; CD133(+)/CD34(+)/KDR(+) 48.4% vs 73.9%; P=0.05; and CD34(+)/CD45(-) 49.3% vs 78.4; P=0.006) was blunted in the South Asian group. CPC mobilization correlated with flow-mediated vasodilatation and l-NMMA significantly reduced exercise-induced CPC mobilization (CD34(+)/KDR(+) -3.3% vs 68.4%; CD133(+)/CD34(+)/KDR(+) 0.7% vs 71.4%; and CD34(+)/CD45(-) -30.5% vs 77.8%; all P<0.001). CONCLUSIONS: In humans, NO is critical for CPC mobilization in response to exercise. Reduced NO bioavailability may contribute to imbalance between vascular damage and repair mechanisms in South Asian men.

Short-axis 2D strain from speckle tracking predicts echocardiographic response to cardiac resynchronization therapy.

AIMS: Two-dimensional (2D) strain imaging from speckle tracking is a Doppler independent technique allowing assessment of left ventricular (LV) strain (ɛ); systolic strain rate (SRs') and early diastolic strain rate (SRe') in the radial and circumferential planes. We set out to investigate whether (i) these parameters facilitated assessment of dyssynchronous contraction and (ii) these measures could predict response to cardiac resynchronization therapy (CRT). METHODS AND RESULTS: Forty-one patients with severe, symptomatic heart failure on optimal medical therapy were recruited. Thirty-two healthy subjects were used as controls. Time to peak ɛ, SRs', and SRe' of 6 LV segments were measured in the parasternal short axis prior to and 6 weeks post CRT implantation. Time delays between segments were then calculated and ANOVA assessed for prediction of response, classified as reduction in LV end systolic volume of >15%. 2D strain demonstrated significantly more dyssynchronous contraction in the heart failure population at baseline compared to healthy controls. Significant reduction in dyssynchrony was seen in ɛ and SRs' following CRT, largely confined to those with evidence of remodeling. The time delay between peak circumferential SRs' of opposing walls was the best predictor of reverse remodeling. CONCLUSION: 2D strain imaging appears to be a useful measure to predict response to CRT. The time to peak circumferential SR is a new predictor of response.

The cardiovascular consequences of fatiguing expiratory muscle work in otherwise resting healthy humans.

In 11 healthy adults (25 ± 4 yr; 2 female, 9 male subjects), we investigated the effect of expiratory resistive loaded breathing [65% maximal expiratory mouth pressure (MEP), 15 breaths·min-1, duty cycle 0.5; ERLPm] on mean arterial pressure (MAP), leg vascular resistance (LVR), and leg blood flow ([Formula: see text]). On a separate day, a subset of five male subjects performed ERL targeting 65% of maximal expiratory gastric pressure (ERLPga). ERL-induced expiratory muscle fatigue was confirmed by a 17 ± 5% reduction in MEP (P < 0.05) and a 16 ± 12% reduction in the gastric twitch pressure response to magnetic nerve stimulation (P = 0.09) from before to after ERLPm and ERLPga, respectively. From rest to task failure in ERLPm and ERLPga, MAP increased (ERLPm = 31 ± 10 mmHg, ERLPga = 18 ± 9 mmHg, both P < 0.05), but group mean LVR and [Formula: see text] were unchanged (ERLPm: LVR = 0.78 ± 0.21 vs. 0.97 ± 0.36 mmHg·mL-1·min, [Formula: see text] = 133 ± 34 vs. 152 ± 74 mL·min-1; ERLPga: LVR = 0.70 ± 0.21 vs. 0.84 ± 0.33 mmHg·mL-1·min, [Formula: see text] = 160 ± 48 vs. 179 ± 110 mL·min-1) (all P ≥ 0.05). Interestingly, [Formula: see text] during ERLPga oscillated within each breath, increasing (∼66%) and decreasing (∼50%) relative to resting values during resisted expirations and unresisted inspirations, respectively. In conclusion, fatiguing expiratory muscle work did not affect group mean LVR or [Formula: see text] in otherwise resting humans. We speculate that any sympathetically mediated peripheral vasoconstriction was counteracted by transient mechanical effects of high intra-abdominal pressures during ERL.NEW & NOTEWORTHY Fatiguing expiratory muscle work in otherwise resting humans elicits an increase in sympathetic motor outflow; whether limb blood flow ([Formula: see text]) and leg vascular resistance (LVR) are affected remains unknown. We found that fatiguing expiratory resistive loaded breathing (ERL) did not affect group mean [Formula: see text] or LVR. However, within-breath oscillations in [Formula: see text] may reflect a sympathetically mediated vasoconstriction that was counteracted by transient increases in [Formula: see text] due to the mechanical effects of high intra-abdominal pressure during ERL.

Power Reserve at Intolerance in Ramp-Incremental Exercise Is Dependent on Incrementation Rate.

INTRODUCTION: The mechanism(s) of exercise intolerance at V˙O2max remain poorly understood. In health, standard ramp-incremental (RI) exercise is limited by fatigue-induced reductions in maximum voluntary cycling power. Whether neuromuscular fatigue also limits exercise when the RI rate is slow and RI peak power at intolerance is lower than standard RI exercise, is unknown. METHODS: In twelve healthy participants, maximal voluntary cycling power was measured during a short (~6 s) isokinetic effort at 80 rpm (Piso) at baseline and, using an instantaneous switch from cadence-independent to isokinetic cycling, immediately at the limit of RI exercise with RI rates of 50, 25, and 10 W·min-1 (RI-50, RI-25, and RI-10). Breath-by-breath pulmonary gas exchange was measured throughout. RESULTS: Baseline Piso was not different among RI rates (analysis of variance; P > 0.05). Tolerable duration increased with decreasing RI rate (RI-50, 411 ± 58 s vs RI-25, 732 ± 93 s vs RI-10, 1531 ± 288 s; P < 0.05). At intolerance, V˙O2peak was not different among RI rates (analysis of variance; P > 0.05), but RI peak power decreased with RI rate (RI-50, 361 ± 48 W vs RI-25, 323 ± 39 W vs RI-10, 275 ± 38 W; P < 0.05). Piso at intolerance was 346 ± 43 W, 353 ± 45 W, and 392 ± 69 W for RI-50, RI-25, and RI-10, respectively (P < 0.05 for RI-10 vs RI-50 and RI-25). At intolerance, in RI-50 and RI-25, Piso was not different from RI peak power (P > 0.05), thus there was no "power reserve." In RI-10, Piso was greater than RI peak power at intolerance (P < 0.001), that is, there was a "power reserve." CONCLUSIONS: In RI-50 and RI-25, the absence of a power reserve suggests the neuromuscular fatigue-induced reduction in Piso coincided with V˙O2max and limited the exercise. In RI-10, the power reserve suggests neuromuscular fatigue was insufficient to limit the exercise, and additional mechanisms contributed to intolerance at V˙O2max.

"Exercise-induced cardiac fatigue"--a review of the echocardiographic literature.

There is growing evidence to support the suggestion that prolonged strenuous exercise has a negative impact on left and right ventricular function during recovery. The main body of evidence covers a 20-year time window with many studies using transthoracic echocardiography to quantify cardiac function. Although studies have addressed different exercise modes and durations most work has been "field" based. During this time period echocardiographic instrumentation and techniques have evolved significantly and their application in the assessment of prolonged exercise has developed in tandem. The primary objective of this article is to provide reflective insight into the phenomenon of "exercise induced cardiac fatigue" by critically evaluating available literature in different competitive field studies or lab-based settings. We achieve this objective by introducing the empirical evidence in relation to echocardiographic modalities employed in developmental order including standard 2D, Doppler, tissue Doppler derived myocardial velocity and strain and myocardial speckle tracking echocardiography and by looking at different modes and duration of exercise. The insights provided by data based on each technique are critically reviewed, contradictory findings are explored and the potential for further work is identified. Furthermore the clinical implications and proposed mechanisms of "exercise-induced cardiac fatigue" are also explored.

UK cardiac rehabilitation fit for purpose? A community-based observational cohort study.

OBJECTIVES: This study aimed to characterise the exercise performed in UK cardiac rehabilitation (CR) and explore relationships between exercise dose and changes in physiological variables. DESIGN: Observational cohort study. SETTING: Outpatient community-based CR in Leeds, UK. Rehabilitation sessions were provided twice per week for 6 weeks. PARTICIPANTS: Sixty patients (45 male/15 female 33-86 years) were recruited following referral to local outpatient CR. OUTCOME MEASURES: The primary outcome was heart rate achieved during exercise sessions. Secondary outcomes were measured before and after CR and included incremental shuttle walk test (ISWT) distance and speed, blood pressure, brachial artery flow-mediated dilatation, carotid arterial stiffness and accelerometer-derived habitual physical activity behaviours. RESULTS: The mean % of heart rate reserve patients exercised at was low and variable at the start of CR (42%±16 %) and did not progress by the middle (48%±17 %) or end (48%±16 %) of the programme. ISWT performance increased following CR (440±150 m vs 633±217 m, p<0.001); however, blood pressure, body weight, endothelial function, arterial stiffness and habitual physical activity behaviours were unchanged following 6 weeks of CR (p>0.05). CONCLUSION: Patients in a UK CR cohort exercise at intensities that are variable but generally low. The exercise dose achieved using this CR format appears inadequate to impact markers of health. Attending CR had no effect on physical activity behaviours. Strategies to increase the dose of exercise patients achieve during CR and influence habitual physical activity behaviours may enhance the effectiveness of UK CR.

Feasibility and reproducibility of a cardiovascular magnetic resonance free-breathing, multi-shot, navigated image acquisition technique for ventricular volume quantification during continuous exercise.

BACKGROUND: Cardiovascular magnetic resonance (CMR) image acquisition techniques during exercise typically requires either transient cessation of exercise or complex post-processing, potentially compromising clinical utility. We evaluated the feasibility and reproducibility of a navigated image acquisition method for ventricular volumes assessment during continuous physical exercise. METHODS: Ten healthy volunteers underwent supine cycle ergometer (Lode) exercise CMR on two separate occasions using a free-breathing, multi-shot, navigated, balanced steady-state free precession cine pulse sequence. Images were acquired at 3-stages, baseline and during steady-state exercise at 55% and 75% maximal heart rate (HRmax), based on a prior supine cardiopulmonary exercise test. Intra-and inter-observer variability and inter-scan reproducibility were derived. Clinical feasibility was tested in a separate cohort of patients with severe mitral regurgitation (n=6). RESULTS: End-diastolic volume (EDV) of both LV and RV decreased during exercise at 55% and 75% HRmax, although a reduction in RVEDV index was only observed at 75% HRmax. Ejection fractions (EF) for both ventricles were significantly higher at 75% HRmax compared to their respective baselines (LVEF 68%±3% vs. 58%±5%, P=0.001; RVEF 66%±4% vs. 58%±7%, P=0.02). Intra-observer and inter-observer reproducibility of LV parameters was excellent at all 3-stages. Although measurements of RVESV were more variable during exercise, the reproducibility of both RVEF and RV cardiac index was excellent (CV <10%). Inter-scan LV and RV ejection fraction were highly reproducible at all 3 stages, although inter-scan reproducibility of indexed RVESV was only moderate. The protocol was well tolerated by all patients. CONCLUSIONS: Exercise CMR using a free-breathing, multi-shot, navigated cine imaging method allows simultaneous assessment of left and right ventricular volumes during continuous exercise. Intra- and inter-observer reproducibility were excellent. Inter-scan LV and RV ejection fraction were also highly reproducible.

Magnetic-resonance-imaging-derived indices for the normalization of left ventricular morphology by body size.

Scaling left ventricular (LV) mass and other cardiac dimensions to account for individual body size is important. The traditional method of simple ratio scaling using, for example, body surface area (BSA) assumes a linear and proportional relationship and accurate measurement of both LV mass and BSA. These assumptions can be questioned; hence, we examined the appropriateness of methods and different indices using highly accurate magnetic resonance imaging scans. Cardiac and whole-body scans were performed in 172 young, healthy, male subjects (age range, 17-28 years) to assess LV mass, volume, linear dimensions, lean body mass and fat mass. Height, body mass and BSA were determined anthropometrically. Relationships were examined for linearity and closeness of fit using log-log least-squares linear regression to determine the slope exponent b (where 1.0 indicates linearity). The relationship between LV mass and lean body mass (b=.90+/-.15; r(2)=.66) was linear and geometrically consistent. This was also the case for LV end-diastolic volume (b=.70), although the confidence intervals were broader (+/-0.32) and the r(2) (.31) smaller. The relationships between LV mass, volume and other variables were generally not linear or geometrically consistent. LV linear dimensions did not demonstrate any linear relationships, and in particular, those with BSA were extremely poor (r(2)=.02-.09). In summary, the traditional scaling of LV measurements to BSA does not remove the influence of body size and other techniques should be considered. Lean body mass was the most appropriate variable for simple indexing of LV mass. No body size variable had a linear and proportional relationship with LV linear dimensions, and the use of simple ratio scaling for these is seriously questioned.

Interpretation of two-dimensional and tissue Doppler-derived strain (epsilon) and strain rate data: is there a need to normalize for individual variability in left ventricular morphology?

AIMS: This study examined the relationships between myocardial strain (epsilon) and strain rate (SR) data, derived from both two-dimensional (2D) speckle tracking and tissue Doppler imaging (TDI), and indices of left ventricular (LV) morphology to assess size-(in)dependence of these functional parameters. METHODS AND RESULTS: 2D speckle tracking and TDI echocardiograms were performed in 79 healthy adult male volunteers (age range: 22-76 years). 2D speckle tracking allowed the determination of myocardial epsilon and peak systolic and early diastolic SR in radial, circumferential, and longitudinal planes, whereas TDI provided longitudinal epsilon only. Mean circumferential and radial epsilon and SR were calculated from data collected at six basal myocardial regions, whereas mean longitudinal epsilon and SR derived from both 2D speckle tracking and TDI were calculated from the basal septum and basal lateral walls. Standard 2D echocardiography allowed the assessment of LV morphology including LV length, LV end-diastolic volume, LV end-diastolic diameter, mean wall thickness, and LV mass. The association of myocardial epsilon and SR data with relevant LV morphology indices was determined by adoption of the general, non-linear allometric model (y= ax(b)). The b exponent +/- 95% confidence intervals were reported. The relationships between the measures of LV morphology and myocardial epsilon and SR were highly variable and generally weak. Only two relationships displayed at least a moderate effect size (r > or = 0.30): (i) 2D circumferential peak systolic SR and LV end-diastolic dimension (b = -0.92; -1.35 to 0.5, r = 0.44) and (ii) TDI longitudinal peak systolic SR and LV length (b = -1.39; -2.11 to -0.66, r = 0.41). CONCLUSION: The empirical relationships derived in this cohort do not support the need to scale myocardial epsilon and SR derived from 2D speckle or TDI for any index of LV morphology.