The gas exchange threshold and the critical power demarcate discrete exercise intensity domains. For the first time, we show that the limit of tolerance during whole body exercise within these domains is characterized by distinct metabolic and neuromuscular responses. Fatigue development during exercise greater than critical power is associated with the attainment of consistent “limiting” values of muscle metabolites, whereas substrate availability and limitations to muscle activation may constrain performance at lower intensities.

These findings suggest that dietary NO3 (-) enhances repeated sprint performance and may attenuate the decline in cognitive function (and specifically reaction time) that may occur during prolonged intermittent exercise.

Cardiac rehabilitation is a complex intervention that includes exercise training, physical activity promotion, health education, cardiovascular risk management and psychological support, personalized to the individual needs of patients with diagnosed heart disease 1 (Fig. 1). In addition to secondary prevention and improvement in cardiovascular prognosis, a focus of modern cardiac rehabilitation has been the drive to improve patient wellbeing and health-related quality of life [2][3][4] .Introduced in the late 1960s, the recommendation for the provision of cardiac rehabilitation was, at that time, confined to low-risk patients who had survived an acute myocardial infarction (MI). With the development of an evidence base over the past two decades supporting the benefits of cardiac rehabilitation, contemporary clinical guidelines now routinely recommend the referral to comprehensive cardiac rehabilitation across a wider range of cardiac diagnoses, including acute coronary syndrome, heart failure with reduced ejection fraction (HFrEF) and coronary revascularization (percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG) surgery).An important emphasis of contemporary guidelines, including the 2020 position statement from the European Association of Preventive Cardiology (EAPC) 5 , the 2017 guidance from the British Association for Cardiovascular Prevention and Rehabilitation 6 and the 2020 position statement from the Secondary Prevention and Rehabilitation Section of EAPC, is the importance of quality assurance in cardiac rehabilitation delivery 7 (Box 1). Key quality assurance elements include the involvement of a multidisciplinary team (including cardiologists, general practitioners and physicians with special interest, nurse specialists, physiotherapists, dietitians and psychologists) trained in the core competencies and effective delivery of the various core elements of a comprehensive cardiac rehabilitation programme (that is, exercise training and promotion, risk factor and self-management education, and psychological support) 1,6 , following a detailed initial assessment of the patient. Initially, cardiac rehabilitation was primarily practised as an exercise training intervention alone 8 . Although exercise training remains a central component of cardiac rehabilitation, the comprehensive model

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Chlorhexidine-containing mouthwash (STRONG), which disturbs oral microflora, has been shown to diminish the rise in plasma nitrite concentration ([NO2-]) and attenuate the reduction in resting blood pressure (BP) typically seen after acute nitrate (NO3-) ingestion. We aimed to determine whether STRONG and weaker antiseptic agents attenuate the physiological effects of chronic NO3- supplementation using beetroot juice (BR). 12 healthy volunteers mouth-rinsed with STRONG, non-chlorhexidine mouthwash (WEAK) and deionised water (CON) 3 times a day, and ingested 70 mL BR (6.2 mmol NO3-), twice a day, for 6 days. BP (at rest and during 10 min of treadmill walking) and plasma and salivary [NO3-] and [NO2-] were measured prior to and on day 6 of supplementation. The change in salivary [NO3-] 4 h post final ingestion was higher (P<0.05) in STRONG (8.7±3.0 mM) compared to CON (6.3±0.9 mM) and WEAK (6.0±3.0 mM). In addition, the rise in plasma [NO2-] at 2 h was lower in STRONG compared with WEAK (by 89±112 nM) and CON (by 200±174 nM) and in WEAK compared with CON (all P<0.05). Changes in resting BP were not different between conditions (P>0.05). However, during treadmill walking, the increase in systolic and mean arterial BP was higher 4 h after the final nitrate bolus in STRONG compared with CON (P<0.05) but not WEAK. The results indicate that both strong and weak antibacterial agents suppress the rise in plasma [NO2-] observed following the consumption of a high NO3- diet and the former can influence the BP response during low-intensity exercise.

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We hypothesized that 4 wk of dietary nitrate supplementation would enhance exercise performance and muscle metabolic adaptations to sprint interval training (SIT). Thirty-six recreationally active subjects, matched on key variables at baseline, completed a series of exercise tests before and following a 4-wk period in which they were allocated to one of the following groups: ) SIT and [Formula: see text]-depleted beetroot juice as a placebo (SIT+PL);) SIT and [Formula: see text]-rich beetroot juice (~13 mmol [Formula: see text]/day; SIT+BR); or ) no training and [Formula: see text]-rich beetroot juice (NT+BR). During moderate-intensity exercise, pulmonary oxygen uptake was reduced by 4% following 4 wk of SIT+BR and NT+BR ( < 0.05) but not SIT+PL. The peak work rate attained during incremental exercise increased more in SIT+BR than in SIT+PL ( < 0.05) or NT+BR ( < 0.001). The reduction in muscle and blood [lactate] and the increase in muscle pH from preintervention to postintervention were greater at 3 min of severe-intensity exercise in SIT+BR compared with SIT+PL and NT+BR ( < 0.05). However, the change in severe-intensity exercise performance was not different between SIT+BR and SIT+PL ( > 0.05). The relative proportion of type IIx muscle fibers in the vastus lateralis muscle was reduced in SIT+BR only ( < 0.05). These findings suggest that BR supplementation may enhance some aspects of the physiological adaptations to SIT. We investigated the influence of nitrate-rich and nitrate-depleted beetroot juice on the muscle metabolic and physiological adaptations to 4 wk of sprint interval training. Compared with placebo, dietary nitrate supplementation reduced the O cost of submaximal exercise, resulted in greater improvement in incremental (but not severe-intensity) exercise performance, and augmented some muscle metabolic adaptations to training. Nitrate supplementation may facilitate some of the physiological responses to sprint interval training.