Introduction: The overshoot of the respiratory exchange ratio (RER) after exercise is reduced in patients with heart failure. Aim: The present study aimed to investigate the presence of this phenomenon in young patients with congenital heart disease (CHD), who generally present reduced cardiorespiratory fitness. Methods: In this retrospective study, patients with CHD underwent a maximal cardiopulmonary exercise testing (CPET) assessing the RER recovery parameters: the RER at peak exercise, the maximum RER value reached during recovery, the magnitude of the RER overshoot and the linear slope of the RER increase after the end of the exercise. Results: In total, 117 patients were included in this study. Of these, there were 24 healthy age-matched control subjects and 93 young patients with CHD (transposition of great arteries, Fontan procedure, aortic coarctation and tetralogy of Fallot). All patients presented a RER overshoot during recovery. Patients with CHD showed reduced aerobic capacity and cardiorespiratory efficiency during exercise, as well as a lower RER overshoot when compared to controls. RER magnitude was higher in the controls and patients with aortic coarctation when compared to those with transposition of great arteries, previous Fontan procedure, and tetralogy of Fallot. The RER magnitude was found to be correlated with the most relevant cardiorespiratory fitness and efficiency indices. Conclusions: The present study proposes new recovery indices for functional evaluation in patients with CHD. Thus, the RER recovery overshoots analysis should be part of routine CPET evaluation to further improve prognostic risk stratifications in patients with CHD.

Introduction: Irisin is a myokine considered to be a potential mediator of exercise-induced energy metabolism and its secretion is known to promote the browning of beige fat cells in white adipose tissue. However, it is currently not known which exercise protocol is the best to enhance irisin concentration in patients with type 2 diabetes (T2D). Objective: The purpose of this study is to provide a review investigating the irisin response to different exercise training modalities and intensities in T2D. Methods: A systematic literature search was performed in May 2022. Results: After the selection process from 938 articles, six studies were included. Selected papers presented different exercise training interventions regarding intensity and modality. One study reported no significant differences in serum irisin levels after exercise training, whereas the other five showed a higher increase in serum irisin levels after exercise training with higher differences in irisin secretion after high-intensity training (HIT). No consideration was possible on exercise modalities. Conclusions: The impact of training intensity and modality was found to be partly discordant but data seem to suggest that HIT promotes greater irisin secretion. Despite the limited evidence, HIT, both in interval and continuous modalities, could be suggested as valid exercise training to increase circulating irisin in patients with T2D.

Funding Acknowledgements Type of funding sources: None. Background In recent years considerable new evidence has been added on the analysis of the recovery phase in patients with heart failure. Transient increases (overshoot) in respiratory gas variables have been observed during exercise recovery, but their clinical significance is not clearly understood. Respiratory Exchange Ratio (RER) at peak exercise (RER peak) is an objective index of exercise intensity. The overshoot phenomenon of the RER is commonly observed during recovery from maximal cardiopulmonary exercise testing (CPET) but initial studies have found a decreased RER-magnitude in patients with heart failure with reduced ejection fraction (HFrEF). Purpose To characterize the functional and prognostic significance of RER recovery kinetics in individuals with HFrEF. Methods This cross-sectional study included all patients with HFrEF who underwent functional evaluation with maximal CPET for the heart transplant checklist at the Sports and Exercise Medicine Division of the Padova University Hospital between January 2018 and December 2021. The presence of overshoot phenomena of different respiratory gas indices was evaluated during the recovery phase, focusing on the RER. The RER behaviour has been evaluated assessing the maximal value during recovery phase (RER max) and the magnitude of the RER overshoot (RER mag). Results 164 patients with HFrEF and 128 controls were included in the study. RER recovery parameters were significantly lower in patients with HFrEF compared to healthy subjects. The RER overshoot showed significant correlations with prognostically relevant CPET parameters and these RER metrics were significantly higher in patients presenting better ventilatory and Weber classes. 24 patients with HFrEF did not present a RER overshoot showing worse cardiorespiratory fitness and efficiency compared to patients with overshoot. Mean follow-up period was 2.57 years during which there were 55 first major cardiovascular events, 22 deaths, 21 heart transplants, and 9 ventricular assist device implantations. The absence of RER overshoot predicted major adverse cardiac events- and transplant-free survival in univariate and multivariate Cox regression analysis. Conclusions RER overshoot represents a new index to monitor respiratory gas kinetics during the recovery phase, since it is a feasible and reproducible parameter for clinical practice. A reduced overshoot or its absence are significantly associated with functional impairment, cardiorespiratory inefficiency and worse prognosis. Thus, the evaluation of the respiratory gas indices during recovery from maximal CPET should be included in routine test interpretation, particularly for patients with HFrEF.