Applications of the Critical Power Model to Dynamic Constant External Resistance Exercise: A Brief Review of the Critical Load Test

The study and application of the critical power (CP) concept has spanned many decades. The CP test provides estimates of two distinct parameters, CP and W0 , that describe aerobic and anaerobic metabolic capacities, respectively. Various mathematical models have been used to estimate the CP and W0 parameters across exercise modalities. Recently, the CP model has been applied to dynamic constant external resistance (DCER) exercises. The same hyperbolic relationship that has been established across various continuous, whole-body, dynamic movements has also been demonstrated for upper-, lower-, and whole-body DCER exercises. The asymptote of the load versus repetition relationship is defined as the critical load (CL) and the curvature constant is L0 . The CL and L0 can be estimated from the same linear and non-linear mathematical models used to derive the CP. The aims of this review are to (1) provide an overview of the CP concept across continuous, dynamic exercise modalities; (2) describe the recent applications of the model to DCER exercise; (3) demonstrate how the mathematical modeling of DCER exercise can be applied to further our understanding of fatigue and individual performance capabilities; and (4) make initial recommendations regarding the methodology for estimating the parameters of the CL test

The effects of percutaneous branch pulmonary artery interventions in biventricular congenital heart disease:study protocol for a randomized controlled Dutch multicenter interventional trial

Background: Branch pulmonary artery (PA) stenosis is one of the most common indications for percutaneous interventions in patients with transposition of the great arteries (TGA), tetralogy of Fallot (ToF), and truncus arteriosus (TA). However, the effects of percutaneous branch PA interventions on exercise capacity remains largely unknown. In addition, there is no consensus about the optimal timing of the intervention for asymptomatic patients according to international guidelines. This trial aims to identify the effects of percutaneous interventions for branch PA stenosis on exercise capacity in patients with TGA, ToF, and TA. In addition, it aims to assess the effects on RV function and to define early markers for RV adaptation and RV dysfunction to improve timing of these interventions. Methods: This is a randomized multicenter interventional trial. TGA, ToF, and TA patients ≥ 8 years with a class IIa indication for percutaneous branch PA intervention according to international guidelines are eligible to participate. Patients will be randomized into the intervention group or the control group (conservative management for 6 months). All patients will undergo transthoracic echocardiography, cardiac magnetic resonance (CMR) imaging, and cardiopulmonary exercise testing at baseline, 6 months, and 2–4 years follow-up. Quality of life (QoL) questionnaires will be obtained at baseline, 2 weeks post intervention or a similar range for the control group, and 6 months follow-up. The primary outcome is exercise capacity expressed as maximum oxygen uptake (peak VO2 as percentage of predicted). A total of 56 patients (intervention group n = 28, control group n = 28) is required to demonstrate a 14% increase in maximum oxygen uptake (peak VO2 as percentage of predicted) in the interventional group compared to the control group (power 80%, overall type 1 error controlled at 5%). Secondary outcomes include various parameters for RV systolic function, RV functionality, RV remodeling, procedural success, complications, lung perfusion, and QoL. Discussion: This trial will investigate the effects of percutaneous branch PA interventions on exercise capacity in patients with TGA, ToF, and TA and will identify early markers for RV adaptation and RV dysfunction to improve timing of the interventions. Trial registration: ClinicalTrials.gov NCT05809310. Registered on March 15, 2023.</p

Haemodynamic and functional consequences of the iatrogenic atrial septal defect following Mitraclip therapy

Percutaneous MitraClip placement for treatment of severe mitral regurgitation in high surgical risk patients is a commonly performed procedure and requires a transseptal puncture to reach the left atrium. The resulting iatrogenic atrial septal defect (iASD) is not routinely closed, yet the haemodynamic and functional consequences of a persisting defect are not fully understood. Despite positive effects such as acute left atrial pressure relief, persisting iASDs are associated with negative consequences, namely significant bidirectional shunting and subsequent worse clinical outcome. Percutaneous closure of the iASD may therefore be desirable in selected cases. In this review we discuss the available literature on this matter

Case report: Dobutamine stress intracoronary physiology and imaging to examine the functional and dynamic properties of an apparent malignant intra-arterial right coronary artery

Background: We present a case concerning a 64-year-old female with complaints of palpitations, chest pain, and an anomalous right coronary artery (RCA) from the opposite sinus (R-ACAOS) with a suspected malignant trajectory on computed tomography. She was referred to our clinic for a second opinion to re-assess the suggested treatment of coronary surgery. Case summary: A coronary angiogram was performed demonstrating a RCA with a tapered ostium typical for an inter-arterial course. Dobutamine and adenosine stress test during simultaneous intracoronary flow, pressure, and ultrasound assessment, was performed to determine the functional significance. After 120 mcg adenosine, intracoronary baseline flow velocity increased from 14 cm/s to a peak flow velocity of 37 cm/s, demonstrating a sufficient coronary flow velocity reserve (CFVR) of 2.6. No intracoronary pressure drop during maximal hyperaemia was found. After maximum dobutamine stress, CFVR was measured 2.5. Fractional flow reserve measured 0.99. Cross-sectional area measurement through intravascular ultrasound demonstrated a diameter reduction from 14.6 mm2 to 8.5 mm2. Therefore, we concluded this aberrant trajectory was not of any functional relevance and should be considered non-malignant. Discussion: There are several anatomic coronary anomalies which may contribute to coronary compression during exercise and are therefore correlated with sudden cardiac death. Right coronary artery from the opposite sinus is correlated with a low mortality rate of 0.2% in comparison to left-ACAOS at 6.3% over 20 years in participants of competitive sport. Therefore, strong evidence of ischaemia must be present before opting for surgery. Our pragmatic approach provided in our opinion enough evidence for a conservative treatment strategy

Muscular Performance and Neuromuscular Fatigue are not Sex-Dependent During Low-Load Fatiguing Bilateral Leg Extension Exercise

Purpose. This study examined the sex-related differences in muscular performance and neuromuscular (electromyographic [EMG] and mechanomyographic [MMG] amplitude [AMP] and mean power frequency [MPF]) responses during fatiguing leg extension repetitions performed at the critical load (CL). Methods. Eleven men and nine women completed one-repetition maximum (1RM) testing, repetitions to failure at 50, 60, 70, and 80% 1RM to determine CL, and repetitions to failure at CL, on separate days. The EMG and MMG, AMP and MPF signals and number of repetitions completed were recorded. Results. There were no sex-dependent responses in the %1RM that corresponded to, the number of repetitions completed at, or the neuromuscular responses during repetitions performed to failure at CL. There were time-dependent responses in EMG AMP from 25-100% of total repetitions completed, respectively. The EMG MPF and MMG MPF demonstrated fatigue-induced decreases from 50-100% and at 100% of total repetitions completed, respectively. There was no change over time for MMG AMP. Conclusions. These findings indicated men and women responded similarly to leg extension exercise performed at the CL. Further, sex-dependent responses to fatiguing exercise may be related to the amount of active muscle mass engaged in exercise and the corresponding afferent feedback that influences peripheral fatigue and central drive during fatiguing tasks