Training principle of overload trial#

Insufficient progressive overload may be one of the reasons for the variability in CR outcomes, including a lack of improvement in CRF within UK programmes. We combined two of these principles into ‘progressive overload’ to examine the hypothesis that allied health professionals were not consistently applying the principle of progressive overload to cardiac patients undertaking a community-based Phase III CR programme. The accronym ‘SPORT’ can be used to describe the five main principles of training, including specificity, progression, overload, reversibility, and tedium. If these findings are generalisable to other UK CR centres, they may be in part responsible for previous reports highlighting significant variability in effectiveness of UK CR services and poor CRF improvements observed from several prior investigations. We found that average mean training intensity achieved over eight weeks was below the lower limit of the minimal exercise training intensity guidelines (<40% HRR) for a Phase III CR programme. This study was performed because we postulated that inadequate exercise dose may be partly responsible for emerging evidence that CR programmes may not be optimised for improving CRF in patients with CHD. Recently, in a detailed analysis of weekly CR training in one UK CR centre, we used digital technology to monitor and record week-by-week progression of individual training load. These findings indicated that a fixed percentage range approach may be inaccurate for prescribing exercise dose in a large proportion of patients undertaking CR. In the majority, the VAT occurred at an exercise intensity <40% HRR. In 112 referred cardiac patients, we found that VAT thresholds were identified outside of the 40–70% predicted HRR exercise training zone in 55% of patients. We recently showed that the fixed percentage method (%HRR) was poorly correlated with an objective, threshold-based approach incorporating the accurate determination of VAT. Training at or above the ventilatory anaerobic threshold (VAT) induces physiological adaptation leading to improved CRF and other cardiovascular risk factors. The 40% HRR threshold is cited as the lowest effective exercise intensity for improving CRF in patients undertaking CR. UK guidance indicates that patients should train at a fixed exercise intensity between 40–70% heart rate reserve (%HRR). Supervised CR programmes in the UK focus on an interval approach to training where patients’ training intensity toggles between cardiovascular (CV) training, and active recovery (AR) exercise. The above authors concluded that low exercise training volumes and small increases in CRF (0.52 metabolic equivalents) may partially explain the reported inefficacy of UK CR to improve patient mortality and morbidity. Earlier support for these findings was reported by Sandercock et al who conducted a UK-based multi-centre study to quantify changes in cardiorespiratory fitness (CRF) changes before and after CR. Their analysis indicated “conclusively” that the current approach to exercise-based CR has no effect on all-cause mortality or cardiovascular mortality, when compared to no-exercise control (p.1). They included 22 studies including 4,834 patients (mean age 59.5 years, 78.4% male). More recently, Powell and colleagues conducted a systematic review and meta-analysis to determine the effectiveness of exercise-based CR in terms of all-cause mortality, cardiovascular mortality, and hospital admissions from the year 2000 onwards, which include only trials which use a modern approach to medical management. On the basis of the findings, RAMIT investigators concluded that “the value of cardiac rehabilitation as practised in the UK is open to question” (p.637).

The study found that CR following myocardial infarction (MI) had no important effect on mortality, cardiac or psychological morbidity, risk factors, health-related quality of life, or physical activity levels.

Training principle of overload trial#

Initially, the RAMIT trial, a large multi-center randomised controlled trial based in representative hospitals in England and Wales, compared 1,813 patients referred to comprehensive CR, or discharged to 'usual care'. Studies emanating from the United Kingdom (UK) have cast doubts over the survival benefits of CR programmes. In 2016, an updated Cochrane review, synthesising 63 international studies, concluded that compared to no exercise control, exercise-based cardiac rehabilitation (CR) reduced the risk of subsequent cardiovascular mortality, but not total mortality.