Relationship between maximal aerobic power with aerobic fitness as a function of signal-to-noise ratio

Sex differences in the effects of inorganic nitrate supplementation on exercise economy and endurance capacity in healthy young adults

Dietary nitrate (NO3-) is a widely used supplement purported to provide beneficial effects during exercise. Most studies to date include predominantly males. Therefore, the present study aimed to investigate if there is a sex-dependent effect of NO3- supplementation on exercise outcomes. We hypothesized that both sexes would exhibit improvements in exercise economy and exercise capacity following NO3- supplementation, but males would benefit to a greater extent. In a double-blind, randomized, crossover study, twelve females (24 ± 4 yr) and fourteen males (23 ± 4 yr) completed two 4-min moderate-intensity (MOD) exercise bouts followed by a time-to-exhaustion (TTE) task after following 3 days of NO3- supplementation (beetroot juice or BRJ) or NO3--depleted placebo (PL). Females were tested during the early follicular phase of the menstrual cycle. During MOD exercise, BRJ reduced the steady-state V̇o2 by ∼5% in males (M: Δ -87 ± 115 mL·min-1; P < 0.05) but not in females (F: Δ 6 ± 195 mL·min-1). Similarly, BRJ extended TTE by ∼15% in males (P < 0.05) but not in females. Dietary NO3- supplementation improved exercise economy during moderate-intensity exercise and exercise capacity during severe-intensity TTE in males but not in females. These differences could be related to estrogen levels, antioxidant capacity, nitrate-reducing bacteria, or a variety of known physiologic differences such as skeletal muscle calcium handling, and/or fiber type. Overall, our data suggests the ergogenic benefits of oral NO3- supplementation found in studies predominantly on male subjects may not be applicable to females.NEW & NOTEWORTHY While inorganic nitrate (NO3-) supplementation has increased in popularity as an ergogenic aid to improve exercise performance, the role of sex in NO3- supplementation on exercise outcomes is lacking despite known physiological differences during exercise between sex. This study revealed that males, but not females, improved exercise economy during submaximal exercise and exercise capacity during exercise within the severe-intensity domain following NO3- supplementation.

Toward characterizing cardiovascular fitness using machine learning based on unobtrusive data

Cardiopulmonary exercise testing (CPET) is a non-invasive approach to measure the maximum oxygen uptake ([Formula: see text]), which is an index to assess cardiovascular fitness (CF). However, CPET is not available to all populations and cannot be obtained continuously. Thus, wearable sensors are associated with machine learning (ML) algorithms to investigate CF. Therefore, this study aimed to predict CF by using ML algorithms using data obtained by wearable technologies. For this purpose, 43 volunteers with different levels of aerobic power, who wore a wearable device to collect unobtrusive data for 7 days, were evaluated by CPET. Eleven inputs (sex, age, weight, height, and body mass index, breathing rate, minute ventilation, total hip acceleration, walking cadence, heart rate, and tidal volume) were used to predict the [Formula: see text] by support vector regression (SVR). Afterward, the SHapley Additive exPlanations (SHAP) method was used to explain their results. SVR was able to predict the CF, and the SHAP method showed that the inputs related to hemodynamic and anthropometric domains were the most important ones to predict the CF. Therefore, we conclude that the cardiovascular fitness can be predicted by wearable technologies associated with machine learning during unsupervised activities of daily living.

Longitudinal assessment of cardiorespiratory fitness and body mass of young healthy adults during COVID-19 pandemic

Physical activity was reduced during the COVID-19 pandemic, especially when lockdowns were mandated; however, little is known about the impact of these lifestyle changes on objective measures of cardiorespiratory fitness. To address this knowledge gap, we evaluated the cardiorespiratory fitness of 14 young healthy adults (4 women, age: 27±6 yr) just prior to the pandemic and after ~1 year of public health measures being in place. During fitness assessments, participants performed submaximal pseudorandom cycling exercise to assess cardiorespiratory kinetics, and a 25 W·min^-1 ramp-incremental cycling test to determine peak oxygen uptake (V̇O₂). Cluster analysis identified two subgroups of participants: those who had reduced peak V̇O₂ at the 1-year follow-up (-0.50±0.17 L·min^-1) and those whose peak V̇O₂ was maintained (0.00±0.10 L·min^-1). Participants with reduced peak V̇O₂ also exhibited slower heart rate kinetics (interaction: p=0.01), reduced peak O₂ pulse (interaction: p<0.001), and lower peak work rate (interaction: p<0.001) after 1 year of the pandemic, whereas these variables were unchanged in the group of participants who maintained peak V̇O₂. Regardless of changes in peak V̇O₂, both subgroups of participants gained body mass (main effect: p=0.002), which was negatively correlated with participants' level of self-reported physical activity level at the follow-up assessment (mass: ρ=-0.59, p=0.03) These findings suggest that some young healthy individuals lost cardiorespiratory fitness during the pandemic, while others gained weight, but both changes could potentially increase the risk of adverse health outcomes and disease later in life if left unaddressed.

Sentinel fall presenting to the emergency department (SeFallED) - protocol of a complex study including long-term observation of functional trajectories after a fall, exploration of specific fall risk factors, and patients' views on falls prevention

BACKGROUND

Falls are a leading cause for emergency department (ED) visits in older adults. As a fall is associated with a high risk of functional decline and further falls and many falls do not receive medical attention, the ED is ideal to initiate secondary prevention, an opportunity generally not taken. Data on trajectories to identify patients, who would profit the most form early intervention and to examine the impact of a fall event, are lacking. To tailor interventions to the individual's needs and preferences, and to address the whole scope of fall risks, we developed this longitudinal study using an extensive assessment battery including dynamic balance and aerobic fitness, but also sensor-based data. Additionally, participative research will contribute valuable qualitative data, and machine learning will be used to identify trips, slips, and falls in sensor data during daily life.

METHODS

This is a mixed-methods study consisting of four parts: (1) an observational prospective study, (2) a randomized controlled trial (RCT) to explore whether a diagnostic to measure reactive dynamic balance influences fall risk, (3) machine learning approaches and (4) a qualitative study to explore patients' and their caregivers' views. We will target a sample size of 450 adults of 60 years and older, who presented to the ED of the Klinikum Oldenburg after a fall and are not hospitalized. The participants will be followed up over 24 months (within four weeks after the ED, after 6, 12 and 24 months). We will assess functional abilities, fall risk factors, participation, quality of life, falls incidence, and physical activity using validated instruments, including sensor-data. Additionally, two thirds of the patients will undergo intensive testing in the gait laboratory and 72 participants will partake in focus group interviews.

DISCUSSION

The results of the SeFallED study will be used to identify risk factors with high predictive value for functional outcome after a sentinel fall. This will help to (1) establish a protocol adapted to the situation in the ED to identify patients at risk and (2) to initiate an appropriate care pathway, which will be developed based on the results of this study.

TRIAL REGISTRATION

DRKS (Deutsches Register für klinische Studien, DRKS00025949 ). Prospectively registered on 4^th November, 2021.

Reliability of spatial-temporal metrics used to assess collective behaviours in football: An in-silico experiment

The purpose of this study was to investigate the reliability of spatial-temporal measurements applied within collective behaviour research in football. In-silico experiments were conducted introducing positional errors (0.5, 2 and 4 m) representative of commercial tracking systems to match data from the 2020 European Championship qualifiers. Ratios of the natural variance ("signal") of spatial-temporal metrics obtained throughout sections of each game relative to the variance created by positional errors ("noise") were taken to calculate reliability. The effects of error magnitude and time of analysis (1, 5 and 15 mins; length of attack: <10, 10-20, >20 s) were assessed and compared using Cohen's f² effect size. Error magnitude was found to exert greater influence on reliability (f² = 0.15 to 0.81) compared with both standard time of analysis (f² = 0.03 to 0.08) and length of attacks (f² = 0.15 to 0.32). the results demonstrate that technologies generating positional errors of 0.5 m or less should be expected to produce spatial-temporal metrics with high reliability. However, technologies that generate errors of 2 m or greater may produce unreliable values, particularly when analyses are conducted over discrete events such as attacks, which although critical, are often short in duration.

Effects of dietary nitrate on the O2 cost of submaximal exercise: Accounting for "noise" in pulmonary gas exchange measurements

Dietary nitrate (NO₃^-) supplementation can reduce the oxygen cost of submaximal exercise, but this has not been reported consistently. We hypothesised that the number of step transitions to moderate-intensity exercise, and corresponding effects on the signal-to-noise ratio for pulmonary V˙ O₂, may be important in this regard. Twelve recreationally active participants were assigned in a randomised, double-blind, crossover design to supplement for 4 days in three conditions: 1) control (CON; water); 2); PL (NO₃^--depleted beetroot juice); and 3) BR (NO₃^--rich beetroot juice). On days 3 and 4, participants completed two 6-min step transitions to moderate-intensity cycle exercise. Breath-by-breath V˙ O₂ data were collected and V˙ O₂ kinetic responses were determined for a single transition and when the responses to 2, 3 and 4 transitions were ensemble-averaged. Steady-state V˙ O₂ was not different between PL and BR when the V˙ O₂ response to one-, two- or three-step transition was compared but was significantly lower in BR compared to PL when four-step transitions was considered (PL: 1.33 ± 0.34 vs. BR: 1.31 ± 0.34 L·min^-1, P < 0.05). There were no differences in pulmonary V˙ O₂ responses between CON and PL (P > 0.05). Multiple step transitions may be required to detect the influence of NO₃^- supplementation on steady-state V˙ O₂.

Cardiorespiratory kinetics in exercise physiology: estimates and predictions using randomized changes in work rate

Purpose

Kinetics of cardiorespiratory parameters (CRP) in response to work rate (WR) changes are evaluated by pseudo-random binary sequences (PRBS testing). In this study, two algorithms were applied to convert responses from PRBS testing into appropriate impulse responses to predict steady states values and responses to incremental increases in exercise intensity.

Methods

13 individuals (age: 41 ± 9 years, BMI: 23.8 ± 3.7 kg m⁻²), completing an exercise test protocol, comprising a section of randomized changes of 30 W and 80 W (PRBS), two phases of constant WR at 30 W and 80 W and incremental WR until subjective fatigue, were included in the analysis. Ventilation (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}_{{\text{E}}}$$\end{document}V˙E), O₂ uptake (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{2}$$\end{document}V˙O2), CO₂ output (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{CO}}_{2}$$\end{document}V˙CO2) and heart rate (HR) were monitored. Impulse responses were calculated in the time domain and in the frequency domain from the cross-correlations of WR and the respective CRP.

Results

The algorithm in the time domain allows better prediction for \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{2}$$\end{document}V˙O2 and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{CO}}_{2}$$\end{document}V˙CO2, whereas for \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}_{{\text{E}}}$$\end{document}V˙E and HR the results were similar for both algorithms. Best predictions were found for \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{2}$$\end{document}V˙O2 and HR with higher (3–4%) 30 W steady states and lower (1–4%) values for 80 W. Tendencies were found in the residuals between predicted and measured data.

Conclusion

The CRP kinetics, resulting from PRBS testing, are qualified to assess steady states within the applied WR range. Below the ventilatory threshold, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{2}$$\end{document}V˙O2 and HR responses to incrementally increasing exercise intensities can be sufficiently predicted.

Influence of the fitting window on the O2 uptake kinetics at the onset of moderate intensity exercise

The O₂ uptake (V̇o₂) data at the onset of an exercise are usually fitted with a mono-exponential function, after removal of the data pertaining to a conventional initial time period (ΔTr) lasting ∼20 s. We performed a thorough quantitative analysis on the effects of removing data pertaining to different ΔTr, aiming at identifying an objective method to establish the appropriate ΔTr. Breath-by-breath O₂ uptake responses, acquired from 25 healthy adults performing a step moderate-intensity exercise, and 10⁴ simulated biexponential responses, were analyzed. For all the responses, the kinetic parameters of a mono-exponential function and the corresponding asymptotic standard errors (ASEs) were estimated by nonlinear regression, removing the data pertaining to progressively longer initial periods (1 s each) up to 60 s. Four methods to establish objectively ΔTr were compared. The minimum estimated τ was obtained for ΔTr ≅ 35 s in both the V̇o₂ and simulated data, that was about 30% lower compared with that obtained for ΔTr ≅ 0s. The average ASE values remained quite constant up to ΔTr ≅ 35 s, thereafter they increased remarkably. The τ used to generate the simulated response fell within the confidence intervals of the estimated τ in ∼85% of cases for ΔTr = 20 s ("20 s-w" method); this percentage increased to ∼92% of cases when ΔTr was established according to both the minimum τ and its narrowest confidence interval ("Mixed" method). In conclusion, the effects of removing V̇o₂ data pertaining to different ΔTr are remarkable. The "Mixed" method provided estimated parameters close to those used to generate the simulated responses and is thus endorsed.NEW & NOTEWORTHY We propose a method to objectively establish the initial time period to be removed from the fitting window when, using a mono-exponential model, the kinetics of the fundamental component is determined on breath-by-breath O₂ uptake data collected at the onset of a moderate-intensity exercise. Innovative statistical parameters ("Coverage" and "Concordance_5%," applicable on simulated responses) were used to compare its performance with that of other three methods. The proposed method yielded the best "Coverage" and "Concordance_5%."