Closure of outpatient cardiac rehabilitation during the first COVID-19 lockdown in Austria in spring 2020 resulted in deteriorating physical exercise capacity: a mixed-methods study

Background Group-based cardiac rehabilitation (CR) has inevitably been disrupted by COVID-19-related public health measures, increasing the risk of deterioration in modifiable risk factors for patients with cardiovascular disease (CVD). Purpose To examine the impact of CR closure during the first COVID-19-related national lockdown in Austria in spring 2020 on patients' maintenance of physical activity, physical fitness levels, and cardiovascular risk profile; and to describe the patient experience of lack of group-based CR training due to COVID-19. Methods This mixed-methods study recruited patients from an outpatient CR centre in Austria during summer 2020. Eligibility criteria were regular attendance at weekly group-based exercise training at the centre until the COVID-19-related lockdown in March 2020; pre-lockdown completion of a maximal cycle ergometer test; no contraindications for maximal exercise testing; and no new complaints limiting exercise performance. Participants underwent post-lockdown quantitative assessment of physical fitness (maximal cycle ergometer testing, submaximal cycle ergometer training session at individual pre-lockdown settings) and cardiovascular risk status. These were compared with pre-lockdown data from medical records. Participants gave qualitative interviews about their experience of maintaining exercise during lockdown. Interviews were audio-recorded, transcribed, coded, and interpreted using framework analysis. Results Twenty-eight (57%) of 49 eligible patients were recruited, 1 withdrew, and 27 completed all study procedures. Two participants were excluded from analysis of physical fitness data, due to subsequent diagnosis of new complaints limiting exercise performance. Mean (SD) age was 69 (7.4) years. Six (22%) were female. Median (IQR) time since first CVD event was 8 (5.5, 9) years. In maximal ergometer testing, 14 (56%) had deteriorated, 10 (40%) were unchanged, and 1 (4%) had improved post-lockdown. At group level, power was significantly reduced (maximal ergometer testing, submaximal ergometer training), whereas CVD risk factors remained unchanged from pre- to post-lockdown (table 1). Qualitative analysis corroborated the negative impact of the closure of CR classes (table 2). Conclusions This patient cohort was heterogeneous with respect to physical activity levels and exercise capacity, yet overall motivated and experienced in exercise training, having regularly attended training sessions at the centre before the lockdown. Despite individually seeking out alternative exercise options during lockdown, group average exercise capacity deteriorated even in this motivated and exercise-conscious group. This highlights the importance of providing group-based opportunities for supervised high intensity training for patients who engage well in such a setting, and the detrimental impact of disruption to this type of CR service. FUNDunding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Ludwig Boltzmann Gesellschaft COVID-19 Support Measure: Open Innovation in Science (OIS) Research Enrichment Fund

Thermodynamic Efficiency Maximum of Simple Organic Rankine Cycles

The increase of the maximal cycle temperature is considered as one of the best tools to increase cycle efficiency for all thermodynamic cycles, including Organic Rankine Cycles (ORC). Technically, this can be done in various ways, but probably the best solution is the use of hybrid systems, i.e., using an added high-temperature heat source to the existing low-temperature heat source. Obviously, this kind of improvement has technical difficulties and added costs; therefore, the increase of efficiency by increasing the maximal temperature sometimes has technical and/or financial limits. In this paper, we would like to show that for an ideal, simple-layout ORC system, a thermodynamic efficiency-maximum can also exist. It means that for several working fluids, the thermodynamic efficiency vs. maximal cycle temperature function has a maximum, located in the sub-critical temperature range. A proof will be given by comparing ORC efficiencies with TFC (Trilateral Flash Cycle) efficiencies; for wet working fluids, further theoretical evidence can be given. The group of working fluids with this kind of maximum will be defined. Generalization for normal (steam) Rankine cycles and CO2 subcritical Rankine cycles will also be shown. Based on these results, one can conclude that the increase of the maximal cycle temperature is not always a useful tool for efficiency-increase; this result can be especially important for hybrid systems.

Estimate of the maximal cycle length in the graph of polynomial transformation of Galois–Eisenstein ring

The paper is concerned with polynomial transformations of a finite commutative local principal ideal of a ring (a finite commutative uniserial ring, a Galois–Eisenstein ring). It is shown that in the class of Galois–Eisenstein rings with equal cardinalities and nilpotency indexes over Galois rings there exist polynomial generators for which the period of the output sequence exceeds those of the output sequences of polynomial generators over other rings.

Continuous laryngoscopy quantitates laryngeal behaviour in exercise and recovery

Exercise-induced laryngeal obstruction (E-ILO) causes exertional dyspnoea. There is no standardised methodology which characterises laryngeal obstruction in relation to exercise or links laryngeal obstruction and dyspnoea severity. Continuous laryngoscopy during exercise (CLE) may improve diagnostic sensitivity by enabling laryngeal visualisation at peak work capacity in patients with rapidly resolving obstruction. The time course of laryngeal obstruction across exercise and recovery has not been quantitated until this report.Adolescents and young adults referred for CLE were laryngoscopically monitored across rest, maximal cycle ergometry exercise, and recovery. Three reviewers, blinded to time sequencing, rated inspiratory glottic and supraglottic obstruction during 10 windows of 15-s corresponding to rest, 25%, 50%, 75%, 90% and 100% of individual symptom-limited peak work capacity (expressed in Watts), and four consecutive recovery windows.85 patients were screened and 71 included. Over 96% of time windows were interpretable. Laryngeal obstruction severity reached observed maximal levels at peak work capacity, and rapidly resolved. A spectrum of observed maximal obstruction was measured.CLE provides interpretable data demonstrating laryngeal obstruction in patients with suspected E-ILO that is more severe at peak work capacity than during rest, submaximal exercise, or recovery. Observed maximal obstruction was infrequently severe and rapidly resolved.

Comparison between parameters from maximal cycle ergometer test first without respiratory gas analysis and thereafter with respiratory gas analysis among healthy prepubertal children

It is important to distinguish true and clinically relevant changes and methodological noise from measure to measure. In the clinical practice, maximal cycle ergometer tests are typically performed first without respiratory gas analysis and thereafter, if needed, with respiratory gas analysis. Therefore, we report a comparison of parameters from maximal cycle ergometer exercise tests that were done first without respiratory gas analysis and thereafter with it in 38 prepubertal and healthy children (20 girls, 18 boys). The Bland–Altman method was used to assess agreement in maximal workload (WMAX), heart rate (HR), and systolic blood pressure (SBP) between rest and maximum. Girls achieved higher WMAX in the exercise tests with respiratory gas analysis compared with exercise tests without respiratory gas analysis (p = 0.016), whereas WMAX was similar in the tests among boys. Maximal HR (proportional offset, –1%; coefficients of variation, 3.3%) and highest SBP (proportional offset, 3%; coefficients of variation, 10.6%) were similar in the tests among children. Precision and agreement for HR improved and precision for SBP worsened with increasing exercise intensity. Heteroscedasticity was not observed for WMAX, HR, or SBP. We conclude that maximal cycle ergometer tests without and with respiratory gas analysis can be used consecutively because measurement of respiratory gases did not impair performance or have a significant effect on the maximality of the exercise tests. Our results suggest that similar references can be used for children who accept or refuse using a mask during a maximal exercise test.

Mechanisms underlying enhancements in muscle force and power output during maximal cycle ergometer exercise induced by chronic β2-adrenergic stimulation in men

The study was a randomized placebo-controlled trial investigating mechanisms by which chronic β2-adrenergic stimulation enhances muscle force and power output during maximal cycle ergometer exercise in young men. Eighteen trained men were assigned to an experimental group [oral terbutaline 5 mg/30 kg body weight (bw) twice daily (TER); n = 9] or a control group [placebo (PLA); n = 9] for a 4-wk intervention. No changes were observed with the intervention in PLA. Isometric muscle force of the quadriceps increased ( P ≤ 0.01) by 97 ± 29 N (means ± SE) with the intervention in TER compared with PLA. Peak and mean power output during 30 s of maximal cycling increased ( P ≤ 0.01) by 32 ± 8 and 25 ± 9 W, respectively, with the intervention in TER compared with PLA. Maximal oxygen consumption (V̇o2max) and time to fatigue during incremental cycling did not change with the intervention. Lean body mass increased by 1.95 ± 0.8 kg ( P ≤ 0.05) with the intervention in TER compared with PLA. Change in single fiber cross-sectional area of myosin heavy chain (MHC) I (1,205 ± 558 μm2; P ≤ 0.01) and MHC II fibers (1,277 ± 595 μm2; P ≤ 0.05) of the vastus lateralis muscle was higher for TER than PLA with the intervention, whereas no changes were observed in MHC isoform distribution. Expression of muscle proteins involved in growth, ion handling, lactate production, and clearance increased ( P ≤ 0.05) with the intervention in TER compared with PLA, with no change in oxidative enzymes. Our observations suggest that muscle hypertrophy is the primary mechanism underlying enhancements in muscle force and peak power during maximal cycling induced by chronic β2-adrenergic stimulation in humans.