Louisa Beale

Why sprint interval training is inappropriate for a largely sedentary population.

Public health practitioners and researchers in behavioral medicine recognize the need to find effective physical activity interventions and prescriptions to curb the growth in inactivity and prevent chronic illness (Conn et al., 2009; Hagger, 2010; Hardcastle et al., 2012; Katzmarzyk and Lear, 2012). For example, researchers in exercise physiology have focused on the minimal dose of exercise needed to gain favorable physiological adaptations to cardiovascular and metabolic systems (Gibala et al., 2012). Efforts to identify a minimal dose of exercise are linked to the problem of exercise adherence with few people meeting current physical activity guidelines of 30 min per day of moderate intensity exercise. Given that time is the most commonly cited barrier to exercise (Trost et al., 2002; Sequeira et al., 2011), exercise professionals have focused attention on the development of time-efficient exercise interventions (Gibala, 2007). A recent development is the advocacy of Sprint Interval Training (SIT) as a means to attain substantial health benefits with a lower overall exercise volume. SIT is characterized by repeated, brief (4–6 × <30 s), intermittent bursts of all-out exercise, interspersed by periods (approximately 4.5 min) of active or passive recovery (Gibala et al., 2012). Research has consistently demonstrated that participation in SIT results in a host of physiological adaptations including improvements in health and fitness indicators (Burgomaster et al., 2006, 2008; Gibala et al., 2006, 2012; Rossow et al., 2010; Tong et al., 2011). In addition, these improvements have been reported to be equal or superior to traditional continuous aerobic training despite SIT involving a substantially lower total overall training volume (Rossow et al., 2010; Tong et al., 2011; Gibala et al., 2012; Cocks et al., 2013). Consequently, SIT is being advocated as a time-efficient alternative intervention for the achievement of fitness and health benefits through exercise (Gibala, 2007; Whyte et al., 2013).

Tissue Doppler–Derived Contractile Reserve Is a Simple and Strong Predictor of Cardiopulmonary Exercise Performance across a Range of Cardiac Diseases

Resting echocardiographic measures of cardiac function such as left ventricular ejection fraction correlate poorly with exercise capacity. Assessment during exercise using measures less dependent on hemodynamic loading conditions, such as tissue Doppler imaging (TDI), may more accurately characterize the relationship between cardiac function and exercise capacity.

Limitations to High Intensity Exercise Prescription in Chronic Heart Failure Patients

Background: Interval training is recommended for chronic heart failure patients (CHF), but specific guidelines on setting appropriate workloads have not been fully established. The aim of this study was to compare a traditional method of interval training prescription with a protocol specifically designed for CHF. Methods: Ten CHF and 7 healthy controls performed 2 maximal incremental cycle tests to determine interval training workload; a standard test (10 W min−1) and a steep test (25 W.10−s). Peak work rate and oxygen uptake (VO2peak) were determined. Training workloads were defined as 100% standard test and 50% steep test peak work rate. Results: Training workload determined from the standard test was higher than from the steep test in healthy controls (151 ± 17 W vs 118 ± 13 W; P < 0.01), whereas in CHF there was no significant difference between methods (88 ± 10 W vs 96 ± 9 W; P > 0.05). Steep test VO2peak reached 91 ± 5% of standard test VO2peak in controls, and 99 ± 4% in CHF, with no significant differences between tests in either group. Conclusion: Prescribing interval training from a standard test results in higher workloads than from a steep test in healthy individuals, but in CHF both methods prescribe similar workloads. However it should not be assumed that the two tests can be used interchangeably for CHF. This small-sized study raises issues about interval training prescription that may be hypothesis-generating for future larger-scale studies.

Prognostic importance of tissue velocity imaging during exercise echocardiography in patients with systolic heart failure.

Resting echocardiography measurements are poor predictors of exercise capacity and symptoms in patients with heart failure (HF). Stress echocardiography may provide additional information and can be expressed using left ventricular ejection fraction (LVEF), or diastolic parameters (E/E′), but LVEF has some major limitations. Systolic annular velocity (S′) provides a measure of longitudinal systolic function, which is relatively easy to obtain and shows a good relationship with exercise capacity. The objective of this study was to investigate the relationship among S′, E/E′ and LVEF obtained during stress echocardiography and both mortality and hospitalisation. A secondary objective was to compare S′ measured using a simplified two-wall model. A total of 80 patients with stable HF underwent exercise stress echocardiography and simultaneous cardiopulmonary exercise testing. Volumetric and tissue velocity imaging (TVI) measurements were obtained, as was peak oxygen uptake (VO2 peak). Of the total number of patients, 11 died and 22 required cardiac hospitalisation. S′ at peak exertion was a powerful predictor for death and hospitalisation. Cut-off points of 5.3 cm/s for death and 5.7 cm/s for hospitalisation provided optimum sensitivity and specificity. This study suggests that, in patients with systolic HF, S′ at peak exertion calculated from the averaged spectral TVI systolic velocity of six myocardial segments, or using a simplified measure of two myocardial segments, is a powerful predictor of future events and stronger than LVEF, diastolic velocities at rest or exercise and VO2 peak. Results indicate that measuring S′ during exercise echocardiography might play an important role in understanding the likelihood of adverse clinical outcomes in patients with HF.

A Comparison of High Intensity Interval Training with Circuit Training in a Short-Term Cardiac Rehabilitation Programme for Patients with Chronic Heart Failure

High intensity interval exercise may be a more effective training method than moderate intensity exercise more commonly applied in cardiac rehabilitation. This randomized controlled trial compared the effects of high intensity interval training with moderate intensity circuit training on exercise tolerance and quality of life in patients with chronic heart failure. Twenty six patients with systolic heart failure (left ventricular ejection fraction 15-40%, New York Heart Association class II-III, age 62-87 years) were randomly assigned to circuit training (n=13) or high intensity interval training (n=13) during a 6 week cardiac rehabilitation programme. At baseline and on completion peak oxygen consumption (VO 2peak ), oxygen consumption at ventilatory threshold (VT), ventilatory efficiency and disease specific quality of life were assessed. There was a significant increase in VO 2peak after training in the circuit group only (0.97 ml.kg-1.min-1 P=0.021). Both groups showed significant improvements in VT (circuit 0.55 ml.kg -1.min-1 P=0.050; interval 1.70 ml.kg -1 .min -1 P=0.006) and in quality of life (circuit-7 points P=0.017; interval-5 points P=0.050). There were no significant differences between the two training methods. High intensity interval exercise offers an alternative training mode for improving sub maximal exercise tolerance and quality of life in patients with chronic heart failure. However, the improvements did not match those reported in studies using more frequent and longer duration training interventions.

132 The importance of contractile reserve when assessing asymptomatic patients with aortic stenosis

Asymptomatic patients may exhibit symptoms during objective exercise testing, but whether symptoms are due to the obstructivity of the valve (typified by the mean gradient) or underlying ventricular function remains unknown. While the mean gradient is an easy parameter to measure no consensus about the measurement of contractile reserve exists. Longitudinal abnormalities may occur in the presence of a normal ejection fraction and the augmentation of these parameters is poorly described. The aim of this study was to examine the echocardiographic predictors of exercise ability during cardiopulmonary exercise testing combined with stress echocardiography. 24 asymptomatic patients with moderate to severe or severe aortic stenosis and preserved ejection fraction underwent stress echocardiography with simultaneous cardiopulmonary exercise testing. The primary assessment of exercise ability was VO2peak. Echocardiography was measured at rest and during maximal exercise (defined as RER>1) VO2peak showed a poor relationship with conventional resting parameters of severity including peak velocity (rho=0.07; p=ns), mean pressure gradient (rho=0.3; p=ns), AVA (rho=0.4; p=ns), dimensionless index (rho=0.05; p=ns), resting systolic function (by EF (rho=−0.18; p=ns) and TDI (rho=0.39; p=ns). During exercise systolic augmentation had a good relationship with exercise ability (rho=0.77; p<0.0001) but the relationship with exercise mean gradient was weaker (rho=0.57; p=0.005) and there was no relationship with exercise LVEF (rho=0.18; p=ns). Longitudinal systolic function during peak exercise is the strongest predictor of exercise ability when compared to conventional measures of severity of aortic stenosis.

Oxygen Cost of Recreational Horse-Riding in Females.

BACKGROUND The purpose of this study was to characterize the physiological demands of a riding session comprising different types of recreational horse riding in females. METHODS Sixteen female recreational riders (aged 17 to 54 years) completed an incremental cycle ergometer exercise test to determine peak oxygen consumption (VO₂peak) and a 45-minute riding session based upon a British Horse Society Stage 2 riding lesson (including walking, trotting, cantering and work without stirrups). Oxygen consumption (VO₂), from which metabolic equivalent (MET) and energy expenditure values were derived, was measured throughout. RESULTS The mean VO₂ requirement for trotting/cantering (18.4 ± 5.1 ml·kg⁻¹·min⁻¹; 52 ± 12% VO₂peak; 5.3 ± 1.1 METs) was similar to walking/trotting (17.4 ± 5.1 ml·kg⁻¹·min⁻¹; 48 ± 13% VO₂peak; 5.0 ± 1.5 METs) and significantly higher than for work without stirrups (14.2 ± 2.9 ml·kg⁻¹·min⁻¹; 41 ± 12% VO₂peak; 4.2 ± 0.8 METs) (P = .001). CONCLUSIONS The oxygen cost of different activities typically performed in a recreational horse riding session meets the criteria for moderate intensity exercise (3-6 METs) in females, and trotting combined with cantering imposes the highest metabolic demand. Regular riding could contribute to the achievement of the public health recommendations for physical activity in this population.

34 Can Exercise Induced Changes in Cardiac Synchrony Predict Response to CRT? – Primary Results from the Exert Trial

Introduction Cardiac resynchronisation therapy (CRT) improves symptoms of heart failure (HF) in the majority of patients but echocardiographic measures of selection have produced disappointing results. These measurements are often carried out at rest. Exercise can alter the magnitude and extent of ventricular dyssynchrony and dynamic changes vary between patients. The aim of this study was to determine whether changing dyssynchrony by exertion would predict a positive response to CRT. Method 38 patients with symptomatic heart failure were included in this study. All patients had a depressed LVEF (<35%) and were clinically selected for CRT therapy. Two comparator groups were formulated: Phasers – subjects whose total mechanical delay (normalised for RR interval) decreased with exercise, and dephasers – subjects whom normalised mechanical remained stable or increased. Mechanical delay was defined from spectral tissue Doppler imaging, time from R wave to onset of post isovolumic S’ at the lateral right and left ventricular annular and interventricular septum. The primary end point was VO2peak at 3 months post implant. Results The overall population showed significant improvements in NYHA class, quality of life, LVEF, resting S’, end diastolic and systolic volumes, and dimensions following CRT at 3 months. No significant improvements were observed for exercise parameters including VO2peak. 14 phasers and 24 dephasers were identified and no differences were found for VO2peak or for any other parameters obtained at 3 months (table 1). Conclusion All patients showed that CRT significantly improved echocardiographic and functional parameters, no improvements were observed for exercise parameters. Exercise dyssynchrony was unable to identify if patients responded positively to CRT therapy. Both phasers and dephasers responded in a similar way to CRT.

Defining Exercise Synchrony in Fit Young Adults: A Tissue Doppler Study

OBJECTIVE Exercise-induced changes in the synchrony of left ventricular contraction may be an important therapeutic target in heart failure. There are limited data to support the feasibility of exercise assessments. In addition, the effect of exercise on synchrony in healthy individuals is undetermined. METHODS Eleven healthy young men underwent tissue Doppler assessments before and immediately after maximal cardiopulmonary exercise. Left ventricular synchrony was assessed using pulsed wave tissue Doppler of the lateral, septal, inferior, and anterior walls. The maximal dispersion times between the walls for onset and peak systolic velocities were used as synchrony indices. RESULTS The proportion of the cardiac cycle taken between Q wave and time to onset or peak systolic motion was constant at rest and peak exercise. There was no significant exercise-induced change seen in either interventricular or intraventricular synchrony. CONCLUSION Exercise synchrony assessment is technically feasible. Synchronization of cardiac contraction is maintained after maximal exercise in healthy individuals.