Constant Workload Research Articles

Leaving the profession as a medical assistant: a qualitative study exploring the process, reasons and potential preventive measures

BackgroundWorldwide growing shortages among health care staff are observed. This also holds true for medical assistants in Germany. Medical assistants mainly work in outpatient care and are the first point of contact for patients while performing clinical and administrative tasks. We sought to explore profession turnover among medical assistants, that is, in terms of the underlying decision-making process, the reasons for leaving the medical assistant profession and potential retention measures from the perspective of former medical assistants.MethodsFor this qualitative study, we conducted semi-structured telephone interviews with 20 former medical assistants between August and November 2023. Eligible for participation were medical assistants who (i) were of legal age, (ii) completed medical assistant vocational training and ii) were formerly employed as a medical assistant, but currently employed in another profession. The interviews were recorded, transcribed verbatim and content-analyzed.ResultsFormer medical assistants expressed various, often interrelated reasons for leaving the profession. These were changes in priorities throughout their career (e.g., in terms of working hours and salary), a constant high workload, barriers to further training, poor career prospects, and poor interpersonal relationships particularly with supervisors, but also within the team and with patients as well as the perception of insufficient recognition by politics and society. Suggestions of former medical assistants to motivate medical assistants to stay in their profession included amongst others higher salaries, more flexible work structures, improved career prospects, and more recognition from supervisors, patients, and society.ConclusionOur study provides insights into the complex decision-making process underlying ultimate medical assistant profession turnover. In light of an already existing shortage of medical assistants, we suggest to further explore how the suggested interventions that aim at retention of working medical assistants can be implemented.

Combined Impact of Heart Rate Sensor Placements with Respiratory Rate and Minute Ventilation on Oxygen Uptake Prediction.

Oxygen uptake (V˙O2) is an essential metric for evaluating cardiopulmonary health and athletic performance, which can barely be directly measured. Heart rate (HR) is a prominent physiological indicator correlated with V˙O2 and is often used for indirect V˙O2 prediction. This study investigates the impact of HR placement on V˙O2 prediction accuracy by analyzing HR data combined with the respiratory rate (RESP) and minute ventilation (V˙E) from three anatomical locations: the chest; arm; and wrist. Twenty-eight healthy adults participated in incremental and constant workload cycling tests at various intensities. Data on V˙O2, RESP, V˙E, and HR were collected and used to develop a neural network model for V˙O2 prediction. The influence of HR position on prediction accuracy was assessed via Bland-Altman plots, and model performance was evaluated by mean absolute error (MAE), coefficient of determination (R2), and mean absolute percentage error (MAPE). Our findings indicate that HR combined with RESP and V˙E (V˙O2HR+RESP+V˙E) produces the most accurate V˙O2 predictions (MAE: 165 mL/min, R2: 0.87, MAPE: 15.91%). Notably, as exercise intensity increases, the accuracy of V˙O2 prediction decreases, particularly within high-intensity exercise. The substitution of HR with different anatomical sites significantly impacts V˙O2 prediction accuracy, with wrist placement showing a more profound effect compared to arm placement. In conclusion, this study underscores the importance of considering HR placement in V˙O2 prediction models, with RESP and V˙E serving as effective compensatory factors. These findings contribute to refining indirect V˙O2 estimation methods, enhancing their predictive capabilities across different exercise intensities and anatomical placements.

Impact of moderate-intensity aerobic exercise in combined hypoxic and hot conditions on endothelial function.

There is no study that has investigated the impact of exercise in a combined hypoxic and hot environment on endothelial function. Therefore, we tested whether aerobic exercise in a combined hypoxic and hot conditions induces further enhancement of endothelial function. Twelve healthy males cycled at a constant workload (50% of their maximal oxygen uptake under normoxic/thermoneutral conditions) for 30 min in four different environments: exercise under normoxic condition (NOR: fraction of inspiratory oxygen or FiO2 = 20.9%, 20°C), exercise under hypoxic condition (HYP: FiO2 = 14.5%, 20°C), exercise under hot condition (HOT: FiO2 = 20.9%, 30°C), and exercise under combined hypoxia and hot conditions (HH: FiO2 = 14.5%, 30°C). Before, during, and after exercise, cardiovascular variables (e.g., heart rate, blood flow, and shear rate), blood variables, and endothelial function evaluated by flow-mediated dilation (FMD) were assessed. Heart rates were significantly higher throughout the HH trial's experimental period than the other trials (p < 0.05). However, in the HH trial, brachial artery blood flow and shear rate did not differ from those in other trials after exercise. Plasma catecholamines (epinephrine, norepinephrine, and dopamine) elevations in response to exercise were significantly higher in the HH trial than in the other three trials (p < 0.05). No considerable differences were observed in FMD responses among trials before and after the exercise. In conclusion, aerobic exercise in a combined hot and hypoxic environment further activated sympathetic nervous activity but did not considerably enhance blood flow, shear rate, or endothelial function.

Characterizing the Exponential Profile of W' Recovery Following Partial Depletion.

The aim of this study was to characterize W' recovery kinetics in response to a partial W' depletion. We hypothesized that W' recovery following a partial depletion would be better described by a biexponential than by a monoexponential model. Nine healthy men performed a ramp incremental exercise test, three to five constant load trials to determine critical power and W', and 10 experimental trials to quantify W' depletion. Each experimental trial consisted of two constant load work bouts (WB1 and WB2) interspersed by a recovery interval. WB1 was designed to evoke a 25% or 75% W' depletion (DEP 25% and DEP 75% ). Subsequently, participants recovered for 30, 60, 120, 300, or 600 s and then performed WB2 to exhaustion to calculate the observed W' recovery (W' OBS ). W' OBS data were fitted using monoexponential and biexponential models, both with a variable and with a fixed model amplitude. Root mean square error and Akaike information criterion (AIC c ) were calculated to evaluate the models' goodness-of-fit. The biexponential model fits were associated with overall lower root mean square error values (0.4% to 5.0%) when compared with the monoexponential models (2.9% to 8.0%). However, ΔAIC c resulted in negative values (-15.5 and -23.3) for the model fits where the amplitude was kept free, thereby favoring the use of a monoexponential model for both depletion conditions. For the model fits where the amplitude was fixed at 100%, ΔAIC c was negative for DEP 25% (-15.0) but positive for DEP 75% (11.2). W' OBS values were strongly correlated between both depletion conditions ( r = 0.92) and positively associated with V̇O 2peak , critical power, and gas exchange threshold ( r = 0.67 to 0.77). The present study results did not provide evidence in favor of a biexponential modeling technique to characterize W' recovery following a partial depletion. Moreover, we demonstrated that fixed time constants were insufficient to model W' recovery across different depletion levels, and that W' recovery was positively associated with aerobic fitness. These findings underline the importance of employing variable and individualized time constants in future predictive W' models.

Quantifying in vivo Mitochondrial Effciency at Rest and during Exercise in Human Skeletal Muscle

Introduction: Mitochondrial effciency provides an additional mechanism to fine-tune oxidative phosphorylation rate to match ATP demand in skeletal muscle with far-reaching consequences on exercise tolerance. However, the direct measurement of both oxygen consumption (VO2) and ATP production from the same region of the contracting muscle in vivo remains a technical challenge. Purpose: Using an innovative approach combining noninvasive phosphorus and proton magnetic resonance spectroscopy (31P/1H-MRS), the present study aimed to characterize skeletal muscle ATP synthesis rate and muscle VO2 at rest and during a graded dynamic plantar flexion exercise to determine mitochondrial effciency in the gastrocnemius muscle. Method: We assessed mitochondrial effciency in the gastrocnemius muscles of 12 healthy adults (21± 1 yrs.). 31P and 1H magnetic resonance spectroscopy (MRS) was performed using a whole-body 3T MR system (Skyra, Siemens) at rest and during a series of constant workloads coupled to brief transient ischemia to quantify both oxidative ATP synthesis (ATPox) rate and myoglobin-derived oxygen consumption (Mb-derived VO2). The MRS data were acquired with a dual-tuned 31P/1H surface coil with linear polarization positioned over the gastrocnemius muscle. Results: As expected, the end-exercise PCr concentration decreased from 29 ± 2 mM of WRmax to 18 ± 1 mM with increasing workload. Likewise, the end-exercise Mb oxygenation level declined linearly with increasing workload. As the exercise workload increased, the ATPox synthesis rate increased linearly (r2 = 0.45), whereas there was no significant change in Mb-derived VO2. At rest, the estimated P/O ratio in the gastrocnemius muscle was 1.95 ± 0.68, whereas non-physiological values were obtained during exercise. Conclusion: During exercise, Mb-derived VO2 was likely limited by O2 availability with the methodology employed (30-sec occlusion, spectrum time resolution of 10 sec), which precluded the accurate quantification of mitochondrial effciency. However, mitochondrial effciency calculated at rest is in agreement with previously documented values ex vivo and thus provides an additional parameter to evaluate mitochondrial function in vivo. This work was funded in part by National Heart, Lung, and Blood Institute Grant R00HL125756. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Personalized Hydration Strategy to Improve Fluid Balance and Intermittent Exercise Performance in the Heat.

Sweat rate and electrolyte losses have a large inter-individual variability. A personalized approach to hydration can overcome this issue to meet an individual's needs. This study aimed to investigate the effects of a personalized hydration strategy (PHS) on fluid balance and intermittent exercise performance. Twelve participants conducted 11 laboratory visits including a VO2max test and two 5-day trial arms under normothermic (NOR) or hyperthermic (HYP) environmental conditions. Each arm began with three days of familiarization exercise followed by two random exercise trials with either a PHS or a control (CON). Then, participants crossed over to the second arm for: NOR+PHS, NOR+CON, HYP+PHS, or HYP+CON. The PHS was prescribed according to the participants' fluid and sweat sodium losses. CON drank ad libitum of commercially-available electrolyte solution. Exercise trials consisted of two phases: (1) 45 min constant workload; (2) high-intensity intermittent exercise (HIIT) until exhaustion. Fluids were only provided in phase 1. PHS had a significantly greater fluid intake (HYP+PHS: 831.7 ± 166.4 g; NOR+PHS: 734.2 ± 144.9 g) compared to CON (HYP+CON: 369.8 ± 221.7 g; NOR+CON: 272.3 ± 143.0 g), regardless of environmental conditions (p < 0.001). HYP+CON produced the lowest sweat sodium concentration (56.2 ± 9.0 mmol/L) compared to other trials (p < 0.001). HYP+PHS had a slower elevated thirst perception and a longer HIIT (765 ± 452 s) compared to HYP+CON (548 ± 283 s, p = 0.04). Thus, PHS reinforces fluid intake and successfully optimizes hydration status, regardless of environmental conditions. PHS may be or is an important factor in preventing negative physiological consequences during high-intensity exercise in the heat.

The Influence of Lung Function and Respiratory Muscle Strength on Quadriceps Muscle Fatigability in COPD Patients Under Long-term Oxygen Therapy

BackgroundThis research investigates quadriceps muscle fatigability (MF) in chronic obstructive pulmonary disease (COPD) patients with chronic respiratory failure (CRF) at different levels of lung obstruction [severe obstruction (SO)=FEV1 <50% and >30% versus very severe obstruction (VSO)=FEV1 ≤30%]. It explores the relationships between quadriceps MF and lung function, respiratory muscles, and oxygenation status. MethodsA post hoc cross-over analysis in 45 COPD patients (20 SO and 25 VSO) undergoing long-term oxygen therapy was performed. Delta change in quadriceps maximum voluntary contraction (MVC) (absolute value and percentage) before and after a constant workload was calculated. Associations between quadriceps MF and lung function, respiratory muscles, and gas exchange were examined using Pearson's correlation and multivariate linear regression analysis. ResultsSO patients experience a more substantial reduction in MVC compared to VSO (−15.15±9.13% vs −9.29±8.90%, p=0.0357), despite comparable resting MVC. Dyspnea is more pronounced in VSO at the beginning and end of the exercise. Correlations were found between MF and maximal inspiratory pressure (MIP) (r=−0.4412, p=0.0056), maximal expiratory pressure (MEP) (r=−0.3561, p=0.0282), and a tendency for FEV1% (r=−0.2931, p=0.0507). The regression model (R2=0.4719) indicates that lower MIP and FEV1 and high total lung capacity are significant factors in reducing quadriceps muscle fatigability after a fatiguing task. ConclusionCOPD patients with more severe pulmonary obstruction and hyperinflation and lower respiratory muscle strength have lower quadriceps MF but higher dyspnea both at rest and during exercise.

Resistance training status detection via local muscular endurance adaptation maximum repetition strategy

Aim: The strength-endurance maximum repetition strategy is local muscular endurance development via unprompted fatigue to voluntary contraction adaptation. Brief review aimed to maximum repetition developing on exercise selection and maximal repetition strategy of resistance training constant set workload. Multiple set and endurance maximum repetition strategy must be planned according to purposing resistance training science. Methods: The local muscular endurance periodic session and periodization detected to strength-endurance maximum repetition strategy including loading change and constant repetition set set-ups respectively, 102.3%, 90%, 85%, 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40% and 30%1RM. The population of resistance training formed on local muscular endurance adaptation to date below of 2023 yr. to trained or untrained resistance individuals obtained from PubMed and Web of Science databases, specifically in S&amp;C Journal investigation. Results: Primarily analysis of LME strategy used to absolute endurance and relative endurance performance uncommon without this critical literature search. Again, strength-endurance loading resistance session have been performed to develop absolute endurance provided high load low repetition strategy commonly used to performance detection and relative endurance detected low load high repetition strategy detected to neurofatigue detection using strength-endurance maximum repetition periodization in researches. Conclusion: Resistance training population may be detecting time-dependent strength and endurance maximum repetition periodic periodization session local muscular endurance adaptation to develop neuromuscular adaptation and strength gain. In conclusion, actual exercise and resistance training can be dependent to LME strategy.

Mental Fatigue Under the Thermoneutral Environment in Buildings: Effects of the Constant and Altered Workload Sequences

In order to explore the effects of constant and altered workload sequences on mental fatigue in a thermoneutral environment, experiments and surveys were carried out in this study. n‐back tasks were used to design different workload sequences. Fifteen healthy right‐handed males were required to experience three different workload sequences for 30 min, respectively, including a constant workload (2‐back task) and 2 altered workload sequences that contained an elevating workload sequence (1‐2‐3‐back tasks) and a reducing workload sequence (3‐2‐1‐back tasks). The PANAS, VAS‐F, and NASA‐TLX scales were selected to investigate changes in the mood, the perceived fatigue, and the perceived workload. Meanwhile, the skin temperature during these three workload sequences was continuously collected. Results from the NASA‐TLX scale indicated that no significant difference in total workload was observed among all three workload sequences. Meanwhile, results from the VAS‐F scale showed that no significant changes in self‐reported mental fatigue were observed among these three workload sequences, which meant that mental fatigue was only related to the total workload. However, self‐reported “energy” from the VAS‐F scale did not reduce significantly during the reducing workload sequence, which meant that the reducing workload sequence could conserve more “energy” than that of the elevating and constant workload sequences. Furthermore, both positive and negative moods changed significantly under the constant workload sequence (2‐back task), but they did not show much changes under altered workloads, which meant that the altered workload sequence could attenuate the mood deterioration. What is more, the mental demand, physical demand, temporal demand, effort, and the total workload increased significantly after both the constant workload and elevating workload sequence, but no significant changes in all these six items of the NASA‐TLX scale were observed under the reducing workload sequence. Finally, the mean skin temperature under the constant workload sequence was lower than that under the altered workload sequences (p &gt; 0.05), but significant changes in skin temperature at the left hand and neck were only observed between the constant and reducing workload sequences. In conclusion, constant and altered workload sequences contributed equally to the mental fatigue in a thermoneutral environment, but the differences in workload sequence produced some differences in mood, energy, and mental demand, which would affect the working performance. Findings of this study provided implications for the proper planning, assignment, and management of tasks in real working settings.

Impact of Acute Exercise Challenge on Airway Dynamics in Children and Young Adults with Sickle Cell Anemia

Background Sickle cell anemia (SCA) complications such as frequent pain, chronic anemia, and acute and chronic organ damage lead to reduced physical functioning and cardiopulmonary fitness in affected individuals. Limited data support the safety of maximal cardiopulmonary exercise testing (CPET) in SCA, yet the safety of submaximal, longer-duration exercise at moderate to high intensity in SCA is unclear. The Sickle Cell Pro-Inflammatory Response to Interval Testing Study (SPRINTS) was a multicenter, prospective study that evaluated the impact of longer, submaximal exercise, which mimics the physical activity patterns of children better than CPET, on the acute inflammatory response and airway dynamics in children and young adults with SCA. In this analysis, we defined the effect of moderate to vigorous exercise on forced expiratory volume in 1 second (FEV1) and acute bronchoconstriction. We hypothesized the risk of exercise-induced bronchoconstriction (EIB) in children with SCA is greater than in controls. Methods SPRINTS was approved by the Lurie Children's central Institutional Review Board. Subjects 10-21 years old with hemoglobin (Hb) SS or S/β0 thalassemia and race-matched controls without SCA or sickle cell trait were enrolled across 4 institutions. Subjects were excluded for 1) inability to perform exercise, 2) receiving chronic transfusions, 3) history of exercise-related arrhythmia/syncope, 4) physician-diagnosed asthma, 5) history of EIB, or 6) history of cardiac disease precluding exercise testing. Participants performed maximal CPET on a cycle ergometer using a standardized Godfrey protocol. At least 2 weeks later, participants performed a controlled intensity interval test (CIIT) consisting of 8 bouts of constant workload cycling randomized to either 50% (moderate intensity) or 70% (vigorous intensity) of peak workload achieved during CPET. Exercise bouts were 2 min each with 1-min rest intervals between bouts. Spirometry was performed pre/post (5, 10, 15, and 30 min) CPET and CIIT. EIB was defined as a drop in FEV1 ≥10% from baseline to the lowest FEV1 recorded. Bivariable comparisons were performed, and logistic regression models analyzed the association between EIB and covariables (age, sex, SCA status, max workload, exercise intensity (CIIT only), baseline FEV1 % predicted, FEV1/FVC % predicted) using IBM ® SPSS ® Statistics. Results Available data from 64 subjects (48% F, 73% on hydroxyurea, mean 13.8±2.8 years) and 40 controls (45% F, mean 15.4±2.9 years) were analyzed. Baseline Hb (8.5±1.2 vs. 13±1.4 g/dL, p &amp;lt; 0.001) and maximal workload achieved during CPET (85±26 vs. 135±45 watts, p &amp;lt; 0.001) were lower in subjects vs. controls. The percentage of participants who completed CIIT did not differ between subjects and controls, and no respiratory-related adverse events, including need for bronchodilator therapy, occurred. At baseline, FEV1 and FEV1 % predicted and other parameters (FVC and FVC % predicted, MMEF and MMEF % predicted) were significantly lower in subjects vs. controls (Table 1). However, there was no between-group difference in baseline FEV1/FVC % predicted. Post-exercise, the percentage of participants who met criteria for EIB did not differ between subjects and controls after CPET (21 vs. 26%, p = 0.537) or CIIT (32 vs. 17%, p = 0.126). There was also no significant between-group difference in the greatest drop in FEV1 from baseline to any post-exercise timepoint (mean value or as % of baseline) after CPET or CIIT. In logistic regression models, SCA status, age, sex, maximal workload during CPET, exercise intensity (CIIT only), baseline FEV1 % predicted and FEV1/FVC % predicted were not associated with EIB after CPET or CIIT (Table 2). Conclusion Compared to controls, children and young adults with SCA and no history of asthma or EIB had lower baseline values on all spirometry parameters except FEV1/FVC % predicted. EIB was not more common in subjects with SCA vs. controls after maximal CPET or a submaximal exercise challenge of longer duration at moderate or vigorous intensity. No independent factors were associated with development of EIB after acute exercise. Despite concerns that undiagnosed lower airways disease in children with SCA is common, our results suggest the risk of EIB in SCA is low and underscore the safety of moderate to vigorous exercise toward developing evidence-based exercise guidelines in non-asthmatic children and young adults with SCA.

“I have to be always on” – managerial role and experience of work-life balance and regeneration practices during remote work

PurposeThe main aims of the paper were to explore the role of information and communication technology (ICT) in shaping the work-life balance of managers working remotely and to identify individual recovery strategies and organisational interventions to support digital managers. The theoretical background was based on the work-family border theory and the effort-recovery model.Design/methodology/approachA semi-structured individual in-depth interview (IDI) was used as the research method. The research group consisted of 13 managers from companies in Poland representing various industries. In all, 560 min of recordings and 201 pages of text were obtained and subsequently coded and categorised.FindingsThe results showed that remote managers struggle with the work-life imbalance and blurred boundaries between work and private roles, as well as difficulties in maintaining digital hygiene. The use of ICT enables high flexibility but contributes to work-life conflict. Managers who work from home experience a constant workload and suffer from impaired recovery. The use of ICT creates a need to recover and maintain digital hygiene. However, there are constraints that impede managers' recovery attempts. Many feel that their work does not allow to recover but requires to be “always on” to help their subordinates fulfil their responsibilities, even though they do not expect their subordinates to work after hours. Finally, managers perceive organisational support as insufficient or inappropriate for their needs. They admit that they do not participate in organisational interventions due to lack of time and do not believe that they help them to maintain or restore their well-being.Originality/valueThe role of ICT in blurring the boundaries between work and private roles was explored in depth, as was the “always on” phenomenon as a factor contributing to the tension between the need to recover and the inability to engage in recovery activities. The study has practical implications for integrating individual and organisational approaches to well-being and identifies solutions to encourage managers to maintain digital hygiene and mental health.

Heart Rate Reserve and VO2 Reserve Are Not Interchangeable During Prolonged Exercise

Abstract Background Percentages of heart rate reserve (%HRR) and oxygen consumption reserve (%VO2R) provide equivalent intensities during incremental exercise. These percentages increase during prolonged exercise at a constant workload, and it is unclear if they increase to a similar degree. In this study, we tested whether %HRR and %VO2R maintain equivalency during prolonged exercise at a constant workload. Methods Fifteen males and 12 females participated in an incremental cycle ergometer test to determine maximum VO2. They then performed 2 prolonged exercise trials, 1 for 30 min at a vigorous-intensity workload corresponding with 60% VO2R, and 1 for 60 min at a moderate-intensity workload of 40% VO2R. HR and VO2 were measured continuously, and %HRR and %VO2R were reported every 5 min. A fan and consumption of cold water were used to minimize heat stress. Results Both %HRR and %VO2R increased during constant-workload exercise (P &amp;lt; 0.001), and %HRR increased significantly more than %VO2R (P &amp;lt; 0.001). Females exhibited greater %HRR than %VO2R beginning at 10 min into both trials (P &amp;lt; 0.05), while %HRR exceeded %VO2R for males beginning at 15 min of the 30-min trial (P &amp;lt; 0.05) and at 30 min of the 60-min trial (P &amp;lt; 0.05). HRR values for females were significantly greater than those for males at most time points (P &amp;lt; 0.05). Conclusion: During prolonged, constant-workload exercise, cardiovascular drift results in a greater increase in %HRR than %VO2R, and this is more pronounced in females than males.

Effects of Sitting Recovery Protocols on Postexercise Heart Rate in Young Adults

Abstract Background We aimed to compare the effects of 3 different upright seated recovery protocols on heart rate recovery (HRR) after a submaximal ergometer exercise. Methods The study included 30 young adult volunteers (15 men and 15 women). Participants performed a submaximal cycle exercise test at a constant workload of 60 Watts until a steady HR was achieved. This was followed by 5 min of: (a) inactive, (b) active loadless, and (c) passive recovery protocols. The HRR was assessed as the difference between the peak exercise HR and the HR recorded following 1 min of recovery and as the percentage HR decline after 1 min postexercise. Abnormal HRR was defined as a reduction of 1-min HRR ≤12 b · min−1 or ≤15 b · min−1 or ≤18 b · min−1. Results In both sexes, HRR was faster during inactive recovery compared with active recovery. In males, HRR was faster during inactive recovery compared with passive recovery protocol. In females, HRR was faster during passive recovery compared with active recovery protocol. The prevalence of impaired HRR was greater in the active recovery compared with the passive and inactive recovery protocols in both sexes. Conclusion The present findings suggest that in both sexes, the postexercise HRR was mediated by a combined action of the central command and other inputs or stimuli arising from skeletal muscle activities. In addition, the active recovery protocol resulted to a slower HRR and elicited more abnormal postexercise HR responses compared with the other recovery protocols.

Comparing the reliability of muscle oxygen saturation with common performance and physiological markers across cycling exercise intensity.

Wearable near-infrared spectroscopy (NIRS) measurements of muscle oxygen saturation (SmO2) demonstrated good test-retest reliability at rest. We hypothesized SmO2 measured with the Moxy monitor at the vastus lateralis (VL) would demonstrate good reliability across intensities. For relative reliability, SmO2 will be lower than volume of oxygen consumption (V̇O2) and heart rate (HR), higher than concentration of blood lactate accumulation ([BLa]) and rating of perceived exertion (RPE). We aimed to estimate the reliability of SmO2 and common physiological measures across exercise intensities, as well as to quantify within-participant agreement between sessions. Twenty-one trained cyclists completed two trials of an incremental multi-stage cycling test with 5 min constant workload steps starting at 1.0 watt per kg bodyweight (W·kg-1) and increasing by 0.5 W kg-1 per step, separated by 1 min passive recovery intervals until maximal task tolerance. SmO2, HR, V̇O2, [BLa], and RPE were recorded for each stage. Continuous measures were averaged over the final 60 s of each stage. Relative reliability at the lowest, median, and highest work stages was quantified as intraclass correlation coefficient (ICC). Absolute reliability and within-subject agreement were quantified as standard error of the measurement (SEM) and minimum detectable change (MDC). Comparisons between trials showed no significant differences within each exercise intensity for all outcome variables. ICC for SmO2 was 0.81-0.90 across exercise intensity. ICC for HR, V̇O2, [BLa], and RPE were 0.87-0.92, 0.73-0.97, 0.44-0.74, 0.29-0.70, respectively. SEM (95% CI) for SmO2 was 5 (3-7), 6 (4-9), and 7 (5-10)%, and MDC was 12%, 16%, and 18%. Our results demonstrate good-to-excellent test-retest reliability for SmO2 across intensity during an incremental multi-stage cycling test. V̇O2 and HR had excellent reliability, higher than SmO2. [BLa] and RPE had lower reliability than SmO2. Muscle oxygen saturation measured by wearable NIRS was found to have similar reliability to V̇O2 and HR, and higher than [BLa] and RPE across exercise intensity, suggesting that it is appropriate for everyday use as a non-invasive method of monitoring internal load alongside other metrics.

Effect of acute heat exposure on the determination of critical power and W′ in women and men

ABSTRACT The goal of this study was to investigate to what extent acute heat exposure would affect the parameters of the power-duration relationship, i.e. CP and W′, using multiple constant workload tests to task failure, in women and men. Twenty four young physically active participants (12 men, 12 women) performed 3-5 constant load tests to determine CP and W′, both in temperate (TEMP; 18°C) and hot (HOT; 36°C) environmental conditions. A repeated-measures ANOVA was executed to find differences between TEMP and HOT, and between women and men. In HOT, CP was reduced by 6.5% (227 ± 50 vs. 212 ± 47 W), while W′ increased 12.4% (16.4 ± 4.4 vs. 18.5 ± 5.6 kJ). No significant two-way sex × temperature interactions were observed, indicating that the environmental conditions did not have a different effect in men compared with women. The intersection of the average curvatures in TEMP and HOT occurred at 137 s and 280 W in women, and 153 s and 397 W in men. Acute heat exposure had an impact on the parameters CP and W′, i.e. CP decreased whereas W′ increased. The increase in W′ might be a consequence of the mathematical modelling for the used test methodology, rather than a physiological accurate value of W′ in HOT. No differences induced by heat exposure were observed between women and men.

Critical power, W' and W' reconstitution in women and men.

The aim of this study was to compare critical power (CP) and work capacity W', and W' reconstitution (W'REC) following repeated maximal exercise between women and men. Twelve women ([Formula: see text]O2PEAK: 2.53 ± 0.37 L·min-1) and 12 men ([Formula: see text]O2PEAK: 4.26 ± 0.30 L·min-1) performed a minimum of 3 constant workload tests, to determine CP and W', and 1 maximal exercise repetition test with three work bouts (WB) to failure, to quantify W'REC during 2 recovery periods, i.e., W'REC1 and W'REC2. An independent samples t test was used to compare CP and W' values between women and men, and a repeated-measures ANOVA was used to compare W'REC as fraction of W' expended during the first WB, absolute W'REC, and normalized to lean body mass (LBM). CP normalized to LBM was not different between women and men, respectively, 3.7 ± 0.5 vs. 4.1 ± 0.4 W·kgLBM-1, while W' normalized to LBM was lower in women 256 ± 29 vs. 305 ± 45J·kgLBM-1. Fractional W'REC1 was higher in women than in men, respectively, 74.0 ± 12.0% vs. 56.8 ± 9.5%. Women reconstituted less W' than men in absolute terms (8.7 ± 1.2 vs. 10.9 ± 2.0kJ) during W'REC1, while normalized to LBM no difference was observed between women and men (174 ± 23 vs. 167 ± 31J·kgLBM-1). W'REC2 was lower than W'REC1 both in women and men. Sex differences in W'REC (absolute women < men; fractional women > men) are eliminated when LBM is accounted for. Prediction models of W'REC might benefit from including LBM as a biological variable in the equation. This study confirms the occurrence of a slowing of W'REC during repeated maximal exercise.

Non-invasive ventilatory support accelerates the oxygen uptake and heart rate kinetics and improves muscle oxygenation dynamics in COPD-HF patients

BackgroundThe aim of this study was to explore the effects of non-invasive positive pressure ventilation (NIPPV) associated with high-intensity exercise on heart rate (HR) and oxygen uptake (V̇O2) recovery kinetics in in patients with coexistence of chronic obstructive pulmonary disease (COPD) and heart failure (HF). MethodsThis is a randomized, double blinded, sham-controlled study involving 14 HF-COPD patients, who underwent a lung function test and Doppler echocardiography. On two different days, patients performed incremental cardiopulmonary exercise testing (CPET) and two constant-work rate tests (80% of CPET peak) receiving Sham or NIPPV (bilevel mode - Astral 150) in a random order until the limit of tolerance (Tlim). During exercise, oxyhemoglobin and deoxyhemoglobin were assessed using near-infrared spectroscopy (Oxymon, Artinis Medical Systems, Einsteinweg, Netherland). ResultsThe kinetic variables of both V̇O2 and HR during the high-intensity constant workload protocol were significantly faster in the NIPPV protocol compared to Sham ventilation (P < 0.05). Also, there was a marked improvement in oxygenation and lower deoxygenation of both peripheral and respiratory musculature in TLim during NIPPV when contrasted with Sham ventilation. ConclusionsNIPPV applied during high-intensity dynamic exercise can effectively improve exercise tolerance, accelerate HR and V̇O2 kinetics, improve respiratory and peripheral muscle oxygenation in COPD-HF patients. These beneficial results from the effects of NIPPV may provide evidence and a basis for high-intensity physical training for these patients in cardiopulmonary rehabilitation programs.

The magnitude and time-course of physiological responses to 9 weeks of incremental ramp testing.

The aims of this study were to assess (1) the day-to-day variability in, and (2) the magnitude and time-course of adaptation of physiological parameters (i.e., maximal oxygen uptake [VO2 max], heart rate [HR], blood lactate concentration, respiratory exchange ratio [RER], ratings of perceived exertion [RPE], and time-to-exhaustion [TTE]) in response to an intervention involving three incremental ramp tests per week for 9 weeks. Twelve participants (25 ± 4yrs, VO2 max, 47.8± 5.2mL∙min-1 ∙kg-1 (means ± SD)) completed the entire experimental procedure. The tests comprised a 5-min constant workload to obtain submaximal parameters followed by an incremental protocol until exhaustion. The mean day-to-day variability for the maximal value of VO2 was 2.8%, 1.1% for HR, 18.1% for blood lactate concentration, 2.1% for RER, 1.1% for RPE, and 5.0% for TTE. The values for the corresponding submaximal variables were 3.8% for VO2 , 2.1% for HR, 15.6% for blood lactate concentration, 2.6% for RER and 6.0% for RPE. VO2 max (+4.7% ± 3.5%), TTE (+17.9% ± 8.6%), and submaximal HR (-3.2± 3.5%) improved significantly. Except for RPE (p< 0.01), there were no alterations in the coefficient of variation for any parameter. On the group level, the first changes greater than the day-to-day variability in VO2 max, TTE, and submaximal HR were observed after 21, 12, and 9 training sessions, respectively. Based on our findings, we recommend that training studies include assessment of the reliability of the measurements, for example, the CVs in the specific laboratory to be able to judge if the changes detected are actually physiological.

Feasibility of Cardiac Exercise Rehabilitation in Patients with Cardiac Amyloidosis

Objective: We aimed to determine if prescribed exercise programs in rehabilitation of patients with cardiac amyloidosis was feasible and beneficial. Methods: This prospective monocentric pilot study was proposed to all adult patients, diagnosed with cardiac amyloidosis, and referred to the cardiac rehabilitation centre at the Henri Mondor University hospital (Créteil, France) between 2011 to 2015. All patients had clinical evaluations, laboratory tests, and echocardiographic examinations upon recruitment to the study. The cardiac exercise rehabilitation programme, in this study, comprised a baseline incremental system-limited exercise test followed by 20 endurance training sessions at a constant workload intensity. Cardiac exercise rehabilitation was deemed feasible if the patient completed the baseline test and 10 sessions without an adverse event. Patients with a relative increase of 16% in VO2max and/or maximal workload were considered to have benefited from cardiac exercise rehabilitation. Results: Overall, 27 cardiac amyloidosis patients were recruited. Cardiac exercise rehabilitation was feasible in 19 (70%) and not feasible in 8 (30%). Of the 19 patients whom cardiac exercise rehabilitation was feasible, cardiac exercise rehabilitation benefited 9 (47%). This benefit was significantly associated with lower N-type pro-brain natriuretic peptide levels, lower creatinineamia, and higher left ventricular ejection fraction at baseline. Conclusion: Cardiac exercise rehabilitation is feasible and beneficial in selected patients with cardiac amyloidosis.

Reduced serum concentrations of reactive oxygen and nitrogen species following strenuous exercise in the heat are not associ-ated with an upregulation in serum antioxidative capacity

Introduction: Reactive oxygen and nitrogen species (RONS) are produced as a response to exercise and play a part in guiding the adaptive response to physical training. Exercise in the heat has been shown to further increase accumulation of RONS in systemic circulation; however, a high anti-oxidative response or heat acclimatization mechanisms could attenuate this response. In a previous study, we found reduced RONS concentrations in trained athletes following strenuous cycling in the heat. Therefore, this secondary analysis assessed whether these reduced RONS serum con-centrations are induced by an increased serum antioxidant capacity. Methods: Twelve male cyclists (V̇O2peak: 60 ± 4 ml ∙ kg-1 ∙ min-1) completed a 60-minute constant workload trial (55% peak power output, ambient temperature 30.4 ± 0.6°C) with and without ice vest in a randomized order. The core body temperature (Tcore) was measured by an ingestible capsule. Blood samples were col-lected before and after each trial to determine superoxide dismutase (SOD) and catalase (CAT) activity, total antioxidant capacity (TAC) and RONS. Due to the absence of between-group dif-ferences, data of both conditions were pooled. Results: Tcore statistically increased (p &lt; 0.001) over the experimental trials (+6.0 ± 1.6%, effect size (ES) = 5.6). Concentrations of RONS (-17.2 ± 15.5%, p &lt; 0.001, ES = 1.0) and TAC (-8.9 ± 22.9%, p = 0.04, ES = 0.7) statistically decreased, while the activity of CAT (+15.5 ± 84.0%, p = 0.90, ES = 0.04) and SOD (+9.2 ± 58.7%, p = 0.98, ES = 0.01) remained un-changed. Conclusions: Reduced serum RONS concentrations after strenuous cycling in the heat were not associated with upregulation of serum antioxidant capacity in trained athletes. The prooxidant-antioxidant balance may rather be regulated at a myocellular level and should be further assessed in future studies.