Respiratory frequency is strongly associated with perceived exertion during time trials of different duration

Validity and Reliability of a New Wearable Chest Strap to Estimate Respiratory Frequency in Elite Soccer Athletes

Assessing respiratory frequency (fR) is practical in monitoring training progress in competitive athletes, especially during exercise. This study aimed to validate a new wearable chest strap (wCS) to estimate fR against ergospirometry as a criterion device in soccer players. A total of 26 elite professional soccer players (mean [standard deviation]: 23.6 [4.8] years; 180.6 [5.7] cm; 77.2 [5.4] kg) from three Italian Serie A League teams participated in this cross-sectional study. The sample included attackers, midfielders, and defenders. fR was assessed during a maximal cardiopulmonary exercise test (CPET) on a treadmill using (i) a breath-by-breath gas exchange analyzer (Vyntus® CPX, Vyaire Medical) and (ii) a novel wCS with sensors designed to assess breath frequency following chest expansions. Pearson's correlation coefficient (r), adjusted coefficient of determination (aR2), Bland-Altman plot analysis, and Lin's concordance correlation coefficient (ρc) were used for comparative analysis (correlation and concordance) among the methods. The repeated measures correlation coefficient (rrm) was used to assess the strength of the linear association between the methods. The intraclass correlation coefficient (ICC) and the Finn coefficient (rF) were used for inter-rater reliability. All statistical analyses were performed within the R statistical computing environment, with 95% confidence intervals (95% CIs) reported and statistical significance set at p < 0.05. A total of 16529 comparisons were performed after collecting the CPET data. The robust time series analysis with Hodges-Lehmann estimation showed no significant differences between both methods (p > 0.05). Correlation among devices was statistically significant and very large (r [95% CI]: 0.970 [0.970, 0.971], p < 0.01; aR2 [95% CI]: 0.942 [0.942, 0.943], p < 0.01) with strong evidence supporting consistency of the new wCS (BF10 > 100). In addition, a high concordance was found (ρc [95% CI]: 0.970 [0.969, 0.971], bias correction factor: 0.999). VyntusTM CPX, as a standard criterion, showed moderate agreement with wCS after Bland-Altman analysis (bias [95% lower to the upper limit of agreement]; % agree: 0.170 [-4.582 to 4.923] breaths·min-1; 69.9%). A strong association between measurements (rrm [95% CI]: 0.960 [0.959, 0.961]), a high absolute agreement between methods (ICC [95% CI]: 0.970 [0.970, 0.971]), and high inter-rater reliability (rF: 0.947) were found. With an RMSE = 2.42 breaths·min-1, the new wCS seems to be an valid and reliable in-field method to evaluate fR compared to a breath-by-breath gas exchange analyzer. Notwithstanding, caution is advised if methods are used interchangeably while further external validation occurs.

The Effect of Duration on Performance and Perceived Fatigability During Acute High-Intensity Interval Exercise in Young, Healthy Males and Females

Few studies have explored the kinetics of performance and perceived fatigability during high-intensity interval training, despite its popularity. We aimed to characterize the kinetics of fatigability and recovery during an 8 × 4-min HIIT protocol, hypothesizing that most muscle function impairment would occur during the initial four intervals. Fifteen healthy males and females (mean ± standard deviation; age = 26 ± 5 years, V̇O2max = 46.8 ± 6.1 mL·kg-1·min-1) completed eight, 4-min intervals at 105% of critical power with 3 min of rest. Maximal voluntary knee extension contractions (MVCs) coupled with electrical nerve stimulation were performed at baseline and after the first, fourth, and eighth intervals. MVC, potentiated twitch force (Pt), and Db10:100 ratio all declined throughout HIIT (p < 0.05). MVC sharply declined after interval 1 (-15 ± 9% relative to baseline; p < 0.05) and had only further declined after interval 8 (-26 ± 11%; p < 0.05), but not interval 4 (-19 ± 13%; p > 0.05). Pt and Db10:100 also sharply declined after interval 1 (Pt: -18 ± 13%, Db10:100: -14 ± 20%; p < 0.05) and further declined after interval 4 (Pt: -35 ± 19%, Db10:100: -30 ± 20%; p < 0.05) but not interval 8 (Pt: -41 ± 19%; Db10:100: -32 ± 18%; p > 0.05). Voluntary activation did not significantly change across the HIIT protocol (p > 0.05). Evoked force recovery was significantly blunted as more intervals were completed: after interval 1, Pt recovered by 7 ± 11% compared to -6 ± 7% recovery after interval 8 (p < 0.05). Ratings of perceived effort, fatigue, and leg pain rose throughout the session (p < 0.05 for each) and were greater (effort and fatigue) for females (p < 0.05). Otherwise, males and females exhibited similar performance fatigability kinetics, with contractile function declines blunted in response to additional intervals.

Elevated muscle pain induced by a hypertonic saline injection reduces power output independent of physiological changes during fixed perceived effort cycling

Pain is a naturally occurring phenomenon that consistently inhibits exercise performance by imposing unconscious, neurophysiological alterations (e.g., corticospinal changes) as well as conscious, psychophysiological pressures (e.g., shared effort demands). Although several studies indicate that pain would elicit lower task outputs for a set intensity of perceived effort, no study has tested this. Therefore, this study investigated the impact of elevated muscle pain through a hypertonic saline injection on the power output, psychophysiological, cerebral oxygenation, and perceptual changes during fixed perceived effort exercise. Ten participants completed three visits (1 familiarization + 2 fixed perceived effort trials). Fixed perceived effort cycling corresponded to 15% above gas exchange threshold (GET) [mean rating of perceived effort (RPE) = 15 "hard"]. Before the 30-min fixed perceived effort exercise, participants received a randomized bilateral hypertonic or isotonic saline injection in the vastus lateralis. Power output, cardiorespiratory, cerebral oxygenation, and perceptual markers (e.g., affective valence) were recorded during exercise. Linear mixed-model regression assessed the condition and time effects and condition × time interactions. Significant condition effects showed that power output was significantly lower during hypertonic conditions [t107 = 208, P = 0.040, β = 4.77 W, 95% confidence interval (95% CI) [0.27 to 9.26 W]]. Meanwhile, all physiological variables (e.g., heart rate, oxygen uptake, minute ventilation) demonstrated no significant condition effects. Condition effects were observed for deoxyhemoglobin changes from baseline (t107 = -3.29, P = 0.001, β = -1.50 ΔμM, 95% CI [-2.40 to -0.61 ΔμM]) and affective valence (t127 = 6.12, P = 0.001, β = 0.93, 95% CI [0.63 to 1.23]). Results infer that pain impacts the self-regulation of fixed perceived effort exercise, as differences in power output mainly occurred when pain ratings were higher after hypertonic versus isotonic saline administration.NEW & NOTEWORTHY This study identifies that elevated muscle pain through a hypertonic saline injection causes significantly lower power output when pain is experienced but does not seem to affect exercise behavior in a residual manner. Results provide some evidence that pain operates on a psychophysiological level to alter the self-regulation of exercise behavior due to differences between conditions in cerebral deoxyhemoglobin and other perceptual parameters.

Cadence Modulation during Eccentric Cycling Affects Perception of Effort But Not Neuromuscular Alterations

INTRODUCTION

A recent study showed that cadence modulation during short eccentric cycling exercise affects oxygen consumption (V̇O 2 ), muscular activity (EMG), and perception of effort (PE). This study examined the effect of cadence on V̇O 2 , EMG, and PE during prolonged eccentric cycling and exercise-induced neuromuscular alterations.

METHODS

Twenty-two participants completed three sessions 2-3 wk apart: 1) determination of the maximal concentric peak power output, familiarization with eccentric cycling at two cadences (30 and 60 rpm at 60% peak power output), and neuromuscular testing procedure; 2) and 3) 30 min of eccentric cycling exercise at a cadence of 30 or 60 rpm. PE, cardiorespiratory parameters, and vastus lateralis and rectus femoris EMG were collected during exercise. The knee extensors' maximal voluntary contraction torque, the torque evoked by double stimulations at 100 Hz (Dt100) and 10 Hz (Dt10), and the voluntary activation level were evaluated before and after exercise.

RESULTS

V̇O 2 , EMG, and PE were greater at 30 than 60 rpm (all P < 0.05). Maximal voluntary contraction torque, evoked torque, and Dt10/Dt100 ratio decreased (all P < 0.01) without cadence effect (all P > 0.28). Voluntary activation level remained constant after both eccentric cycling exercises ( P = 0.87).

CONCLUSIONS

When performed at the same power output, eccentric cycling exercise at 30 rpm elicited a greater PE, EMG, and cardiorespiratory demands than pedaling at 60 rpm. Exercise-induced fatigability was similar in both eccentric cycling conditions without neural impairments, suggesting that eccentric cycling seemed to alter more specifically muscular function, such as the excitation-contraction coupling process. In a rehabilitation context, eccentric cycling at 60 rpm seems more appropriate because it will induce lower PE for similar strength loss compared with 30 rpm.

Analysing experienced and inexperienced cyclists' attentional focus and self-regulatory strategies during varying intensities of fixed perceived effort cycling: A mixed method study

Using a think aloud approach during fixed perceived effort exercise is a unique method to explore the decision-making processes that guide the self-regulation of perceived effort during endurance-based activity. In a two-part study, authors investigated the attentional focus and self-regulatory strategies associated with: Part A - perceived effort corresponding to (RPEGET) and above gas exchange threshold (RPE+15%GET); Part B - between experienced and inexperienced cyclists during fixed perceived effort cycling tasks. Eighteen (15 male, 3 female) healthy, active individuals completed three visits (visit 1 - ramped incremental test and familiarisation, visit 2 and 3-30-min fixed perceived effort cycling). During which, power output, heart rate, lactate, think aloud, and perceptual markers were taken. Random-intercepts linear mixed-effects models assessed the condition, time, and condition × time interactions on all dependent variables. Power output, heart rate, lactate and instances of internal sensory monitoring (t195=2.57,p=.011,β=0.95[0.23,1.68]) and self-regulation (t195=4.14,p=.001,β=1.69[0.89,2.49]) were significantly higher in the RPE+15%GET versus RPEGET trial. No significant differences between inexperienced and experienced cyclists for internal sensory monitoring (t196=-1.78,p=.095,β=-1.73[-3.64,0.18]) or self-regulatory thoughts (t196=-0.39,p=.699,β=-1.06[-6.32,4.21]) were noted but there were significant condition × time interactions for internal monitoring (t196=2.02,p=.045,β=0.44[0.01,0.87]) and self-regulation (t196=3.45,p=.001,β=0.85[0.37,1.33]). Seemingly, experienced athletes associatively attended to internal psychophysiological state and subsequently self-regulate their psychophysiological state at earlier stages of exercise than inexperienced athletes. This is the first study to exhibit the differences in attentional focus and self-regulatory strategies that are activated based on perceived effort intensity and experience level in cyclists.

Improvement of the aerobic performance in endurance athletes presenting nasal valve compromise with the application of an internal nasal dilator

PURPOSE

We investigated the effects of an internal nasal dilator on nasal airflow and cardio-respiratory capacity in adult endurance athletes, while performing controlled exhaustive physical exercise.

METHODS

Prospective observational study. Participants were 38 adult endurance athletes, 23 with and 15 without nasal valve compromise. Nasal patency was objectively evaluated with anterior rhinomanometry, acoustic rhinometry and peak nasal inspiratory flow (PNIF). Maximum oxygen uptake (VO2max), maximum pulmonary ventilation, time to exhaustion and total time of nasal respiration were recorded during a submaximal treadmill test. Dyspnea intensity and fatigue perception were evaluated using a labeled visual analog scale. All assessments were performed with and without the application of the internal nasal dilator.

RESULTS

All the parameters related to aerobic capacity were significantly reduced in the group of athletes with nasal valve compromise (p. <0.05 for all variables). The internal nasal dilator improved statistically significantly the nasal patency (p. <0.001), VO2max and aerobic performance and self-rating of dyspnea and fatigue (p. <0.05 for all parameters) only in athletes with nasal obstruction. PNIF correlated significantly with VO2max (rho = 0.4, p. <0.05).

CONCLUSIONS

Internal nasal dilation improves nasal patency and aerobic performance during submaximal exercise in adult endurance athletes with nasal obstruction symptoms due to nasal valve compromise.

Fatigue Resistance Is Altered during the High-Hormone Phase of Eumenorrheic Females but Not Oral Contraceptive Users

PURPOSE

This study aimed to examine the effect of ovarian hormones and their synthetic equivalents on substrate utilization and fatigue resistance during a race-specific cycling protocol.

METHODS

Seventeen well-trained female cyclists (nine eumenorrheic females, eight oral contraceptive users) completed two experimental trials, in a randomized order, in their low- (follicular/sugar pill) and high-hormone (luteal/active pill) phases. Each 91-min trial consisted of a 45-min moderate-intensity component (submaximal cycling, or SMC) followed by 6 min of high-intensity (HIT) and then a fatigue resistance test (FRT): 6 × 1-min all-out efforts with 1-min active recovery. Meals, comprising carbohydrate (CHO) intake of 8 g·kg -1 body mass, were standardized 24-h pretrial. An electrolyte-only solution was provided ad libitum during each trial.

RESULTS

In eumenorrheic females, a large reduction in average power during FRT was observed in the luteal phase (277 ± 31 vs 287 ± 33 W; P = 0.032). Greater CHO ox (~ 4%, P = 0.020) during SMC and ventilatory inefficiencies during SMC and HIT (~7%, P < 0.001) were also observed in the luteal phase. In contraceptive users, despite some phasal changes in cardiorespiratory and metabolic data in SMC (~6% higher blood glucose and ~2% higher minute ventilation in active pill phase), none of the performance parameters in the FRT were different.

CONCLUSIONS

Fatigue resistance was compromised only in high-hormone phase of the menstrual cycle, with eumenorrheic females likely susceptible because of increased CHO utilization during SMC. Hormone-induced ventilatory inefficiencies may also have increased metabolic demand. These findings emphasize the need to maintain CHO availability for power production, particularly in high-hormone phases.

Ventilation and perceived exertion are sensitive to changes in exercise tolerance: arm+leg cycling vs. leg cycling

Purpose: Growing evidence suggests that respiratory frequency (f R) is a marker of physical effort and a variable sensitive to changes in exercise tolerance. The comparison between arm+leg cycling (Arm+leg) and leg cycling (Leg) has the potential to further test this notion because a greater exercise tolerance is expected in the Arm+leg modality. We systematically compared Arm+leg vs. Leg using different performance tests. Methods: Twelve males underwent six performance tests in separate, randomized visits. Three tests were performed in each of the two exercise modalities, i.e. an incremental test and two time-to-exhaustion (TTE) tests performed at 90% or 75% of the peak power output reached in the Leg incremental test (PPOLeg). Exercise tolerance, perceived exertion, and cardiorespiratory variables were recorded during all the tests. Results: A greater exercise tolerance (p < 0.001) was found for Arm+leg in the incremental test (337 ± 32 W vs. 292 ± 28 W), in the TTE test at 90% of PPOLeg (638 ± 154 s vs. 307 ± 67 s), and in the TTE test at 75% of PPOLeg (1,675 ± 525 s vs. 880 ± 363 s). Unlike V ˙ O2 and heart rate, both f R and minute ventilation were lower (p < 0.003) at isotime in all the Arm+leg tests vs. Leg tests. Furthermore, a lower perceived exertion was observed in the Arm+leg tests, especially during the TTE tests (p < 0.001). Conclusion: Minute ventilation, f R and perceived exertion are sensitive to the improvements in exercise tolerance observed when comparing Arm+leg vs. Leg, unlike V ˙ O2 and heart rate.

Wearable and Non-Invasive Sensors for Rock Climbing Applications: Science-Based Training and Performance Optimization

Rock climbing has evolved from a method for alpine mountaineering into a popular recreational activity and competitive sport. Advances in safety equipment and the rapid growth of indoor climbing facilities has enabled climbers to focus on the physical and technical movements needed to elevate performance. Through improved training methods, climbers can now achieve ascents of extreme difficulty. A critical aspect to further improve performance is the ability to continuously measure body movement and physiologic responses while ascending the climbing wall. However, traditional measurement devices (e.g., dynamometer) limit data collection during climbing. Advances in wearable and non-invasive sensor technologies have enabled new applications for climbing. This paper presents an overview and critical analysis of the scientific literature on sensors used during climbing. We focus on the several highlighted sensors with the ability to provide continuous measurements during climbing. These selected sensors consist of five main types (body movement, respiration, heart activity, eye gazing, skeletal muscle characterization) that demonstrate their capabilities and potential climbing applications. This review will facilitate the selection of these types of sensors in support of climbing training and strategies.

Deployed Veterans exhibit distinct respiratory patterns and greater dyspnea during maximal cardiopulmonary exercise: A case-control study

BACKGROUND

Exertional dyspnea and exercise intolerance are frequently endorsed in Veterans of post 9/11 conflicts in Southwest Asia (SWA). Studying the dynamic behavior of ventilation during exercise may provide mechanistic insight into these symptoms. Using maximal cardiopulmonary exercise testing (CPET) to experimentally induce exertional symptoms, we aimed to identify potential physiological differences between deployed Veterans and non-deployed controls.

MATERIALS AND METHODS

Deployed (n = 31) and non-deployed (n = 17) participants performed a maximal effort CPET via the Bruce treadmill protocol. Indirect calorimetry and perceptual rating scales were used to measure rate of oxygen consumption ([Formula: see text]), rate of carbon dioxide production ([Formula: see text]), respiratory frequency (f R), tidal volume (VT), minute ventilation ([Formula: see text]), heart rate (HR), perceived exertion (RPE; 6-20 scale), and dyspnea (Borg Breathlessness Scale; 0-10 scale). A repeated measures analysis of variance (RM-ANOVA) model (2 groups: deployed vs non-deployed X 6 timepoints: 0%, 20%, 40%, 60%, 80%, and 100% [Formula: see text]) was conducted for participants meeting valid effort criteria (deployed = 25; non-deployed = 11).

RESULTS

Significant group (η2partial = 0.26) and interaction (η2partial = 0.10) effects were observed such that deployed Veterans exhibited reduced f R and a greater change over time relative to non-deployed controls. There was also a significant group effect for dyspnea ratings (η2partial = 0.18) showing higher values in deployed participants. Exploratory correlational analyses revealed significant associations between dyspnea ratings and fR at 80% (R2 = 0.34) and 100% (R2 = 0.17) of [Formula: see text], but only in deployed Veterans.

CONCLUSION

Relative to non-deployed controls, Veterans deployed to SWA exhibited reduced fR and greater dyspnea during maximal exercise. Further, associations between these parameters occurred only in deployed Veterans. These findings support an association between SWA deployment and affected respiratory health, and also highlight the utility of CPET in the clinical evaluation of deployment-related dyspnea in Veterans.

Design and Testing of a Smart Facemask for Respiratory Monitoring during Cycling Exercise

Given the importance of respiratory frequency (f_R) as a valid marker of physical effort, there is a growing interest in developing wearable devices measuring f_R in applied exercise settings. Biosensors measuring chest wall movements are attracting attention as they can be integrated into textiles, but their susceptibility to motion artefacts may limit their use in some sporting activities. Hence, there is a need to exploit sensors with signals minimally affected by motion artefacts. We present the design and testing of a smart facemask embedding a temperature biosensor for f_R monitoring during cycling exercise. After laboratory bench tests, the proposed solution was tested on cyclists during a ramp incremental frequency test (RIFT) and high-intensity interval training (HIIT), both indoors and outdoors. A reference flowmeter was used to validate the f_R extracted from the temperature respiratory signal. The smart facemask showed good performance, both at a breath-by-breath level (MAPE = 2.56% and 1.64% during RIFT and HIIT, respectively) and on 30 s average f_R values (MAPE = 0.37% and 0.23% during RIFT and HIIT, respectively). Both accuracy and precision (MOD ± LOAs) were generally superior to those of other devices validated during exercise. These findings have important implications for exercise testing and management in different populations.

A closer look at yoga nidra- early randomized sleep lab investigations

OBJECTIVES

We aimed to examine trial feasibility plus physiological and psychological effects of a guided meditation practice, Yoga Nidra, in adults with self-reported insomnia.

METHODS

Twenty-two adults with self-reported insomnia were recruited to attend two visits at our research center. At Visit 1 (V1), participants were asked to lie quietly for ninety minutes. The primary outcome was change in electroencephalography (EEG). Heart rate variability (HRV), respiratory rate and self-reported mood and anxiety were also measured. At Visit 2 (V2), the same protocol was followed, except half of participants were randomized to practice Yoga Nidra for the first 30-min.

RESULTS

There were no between-group changes (V1-V2) in alpha EEG power at O1 (Intervention: 13 ± 70%; Control: -20 ± 40%), HRV or sleep onset latency in response to Yoga Nidra. Respiratory rate, however, showed statistically significant difference between groups (Yoga Nidra -1.4 breaths per minute (bpm) change during and - 2.1 bpm afterwards vs. Control +0.2 bpm during and + 0.4 bpm after; p = .03 for both during and after). The intervention displayed good acceptability (well-tolerated) and credibility (perceived benefit ratings) with implementation success (target sample size reached; 5% dropout rate).

CONCLUSIONS

This preliminary clinical trial provides early evidence that Yoga Nidra is a well-tolerated, feasible intervention for adults reporting insomnia. Decreased respiratory rate in response to Yoga Nidra needs to be confirmed in more definitive studies.

TRIAL REGISTRATION INFORMATION

This trial was registered on ClinicalTrials.gov as "A Closer Look at Yoga Nidra: Sleep Lab Analyses" (NCT#03685227).

Cardiorespiratory optimal point as a submaximal evaluation tool in endurance athletes: An exploratory study

Introduction: The cardiorespiratory optimal point (COP) represents the lowest minute ventilation to oxygen consumption ratio (VE/VO2) and can be estimated during a CPET at submaximal intensity when an exercise test until volitional fatigue is not always advisable (i.e., a conflict zone where you cannot be confident of the security because near-competition, off-season, among other). COP's physiological components have not been wholly described yet. Therefore, this study seeks to identify the determinants of COP in highly trained athletes and its influence on maximum and sub-maximum variables during CPET through principal c omponent analysis (PCA) (explains the dataset's variance). Methods: Female (n = 9; age, 17.4 ± 3.1 y; maximal VO2 [VO2max]), 46.2 ± 5.9 mL/kg/min) and male (n = 24; age, 19.7 ± 4.0 y; VO2max, 56.1 ± 7.6 mL/kg/min) athletes performed a CPET to determine the COP, ventilatory threshold 1 (VT1) and 2 (VT2), and VO2max. The PCA was used to determine the relationship between variables and COP, explaining their variance. Results: Our data revealed that females and males displayed different COP values. Indeed, males showed a significant diminished COP compared to the female group (22.6 ± 2.9 vs. 27.2 ±3.4 VE/VO2, respectively); nevertheless, COP was allocated before VT1 in both groups. Discussion: PC analysis revealed that the COP variance was mainly explained (75.6%) by PC1 (expired CO₂ at VO2max) and PC2 (VE at VT2), possibly influencing cardiorespiratory efficiency at VO2max and VT2. Our data suggest that COP could be used as a submaximal index to monitor and assess cardiorespiratory system efficiency in endurance athletes. The COP could be particularly useful during the offseason and competitive periods and the return to the sports continuum.

Differential control of respiratory frequency and tidal volume during exercise

The lack of a testable model explaining how ventilation is regulated in different exercise conditions has been repeatedly acknowledged in the field of exercise physiology. Yet, this issue contrasts with the abundance of insightful findings produced over the last century and calls for the adoption of new integrative perspectives. In this review, we provide a methodological approach supporting the importance of producing a set of evidence by evaluating different studies together-especially those conducted in 'real' exercise conditions-instead of single studies separately. We show how the collective assessment of findings from three domains and three levels of observation support the development of a simple model of ventilatory control which proves to be effective in different exercise protocols, populations and experimental interventions. The main feature of the model is the differential control of respiratory frequency (f_R) and tidal volume (V_T); f_R is primarily modulated by central command (especially during high-intensity exercise) and muscle afferent feedback (especially during moderate exercise) whereas V_T by metabolic inputs. Furthermore, V_T appears to be fine-tuned based on f_R levels to match alveolar ventilation with metabolic requirements in different intensity domains, and even at a breath-by-breath level. This model reconciles the classical neuro-humoral theory with apparently contrasting findings by leveraging on the emerging control properties of the behavioural (i.e. f_R) and metabolic (i.e. V_T) components of minute ventilation. The integrative approach presented is expected to help in the design and interpretation of future studies on the control of f_R and V_T during exercise.

Pharmacological Blockade of Muscle Afferents and Perception of Effort: A Systematic Review with Meta-analysis

BACKGROUND

The perception of effort provides information on task difficulty and influences physical exercise regulation and human behavior. This perception differs from other-exercise related perceptions such as pain. There is no consensus on the role of group III/IV muscle afferents as a signal processed by the brain to generate the perception of effort.

OBJECTIVE

The aim of this meta-analysis was to investigate the effect of pharmacologically blocking muscle afferents on the perception of effort.

METHODS

Six databases were searched to identify studies measuring the ratings of perceived effort during physical exercise, with and without pharmacological blockade of muscle afferents. Articles were coded based on the operational measurement used to distinguish studies in which perception of effort was assessed specifically (effort dissociated) or as a composite experience including other exercise-related perceptions (effort not dissociated). Articles that did not provide enough information for coding were assigned to the unclear group.

RESULTS

The effort dissociated group (n = 6) demonstrated a slight increase in ratings of perceived effort with reduced muscle afferent feedback (standard mean change raw, 0.39; 95% confidence interval 0.13-0.64). The group effort not dissociated (n = 2) did not reveal conclusive results (standard mean change raw, - 0.29; 95% confidence interval - 2.39 to 1.8). The group unclear (n = 8) revealed a slight ratings of perceived effort decrease with reduced muscle afferent feedback (standard mean change raw, - 0.27; 95% confidence interval - 0.50 to - 0.04).

CONCLUSIONS

The heterogeneity in results between groups reveals that the inclusion of perceptions other than effort in its rating influences the ratings of perceived effort reported by the participants. The absence of decreased ratings of perceived effort in the effort dissociated group suggests that muscle afferent feedback is not a sensory signal for the perception of effort.

Restricted nasal-only breathing during self-selected low intensity training does not affect training intensity distribution

Introduction: Low-intensity endurance training is frequently performed at gradually higher training intensities than intended, resulting in a shift towards threshold training. By restricting oral breathing and only allowing for nasal breathing this shift might be reduced. Methods: Nineteen physically healthy adults (3 females, age: 26.5 ± 5.1 years; height: 1.77 ± 0.08 m; body mass: 77.3 ± 11.4 kg; VO₂peak: 53.4 ± 6.6 mL·kg^-1 min^-1) performed 60 min of self-selected, similar (144.7 ± 56.3 vs. 147.0 ± 54.2 W, p = 0.60) low-intensity cycling with breathing restriction (nasal-only breathing) and without restrictions (oro-nasal breathing). During these sessions heart rate, respiratory gas exchange data and power output data were recorded continuously. Results: Total ventilation (p < 0.001, η_p ² = 0.45), carbon dioxide release (p = 0.02, η_p ² = 0.28), oxygen uptake (p = 0.03, η_p ² = 0.23), and breathing frequency (p = 0.01, η_p ² = 0.35) were lower during nasal-only breathing. Furthermore, lower capillary blood lactate concentrations were found towards the end of the training session during nasal-only breathing (time x condition-interaction effect: p = 0.02, η_p ² = 0.17). Even though discomfort was rated marginally higher during nasal-only breathing (p = 0.03, η_p ² = 0.24), ratings of perceived effort did not differ between the two conditions (p ≥ 0.06, η_p ² = 0.01). No significant "condition" differences were found for intensity distribution (time spent in training zone quantified by power output and heart rate) (p ≥ 0.24, η_p ² ≤ 0.07). Conclusion: Nasal-only breathing seems to be associated with possible physiological changes that may help to maintain physical health in endurance athletes during low intensity endurance training. However, it did not prevent participants from performing low-intensity training at higher intensities than intended. Longitudinal studies are warranted to evaluate longitudinal responses of changes in breathing patterns.

Estimation of Respiratory Frequency in Women and Men by Kubios HRV Software Using the Polar H10 or Movesense Medical ECG Sensor during an Exercise Ramp

Monitoring of the physiologic metric, respiratory frequency (RF), has been shown to be of value in health, disease, and exercise science. Both heart rate (HR) and variability (HRV), as represented by variation in RR interval timing, as well as analysis of ECG waveform variability, have shown potential in its measurement. Validation of RF accuracy using newer consumer hardware and software applications have been sparse. The intent of this report is to assess the precision of the RF derived using Kubios HRV Premium software version 3.5 with the Movesense Medical sensor single-channel ECG (MS ECG) and the Polar H10 (H10) HR monitor. Gas exchange data (GE), RR intervals (H10), and continuous ECG (MS ECG) were recorded from 21 participants performing an incremental cycling ramp to failure. Results showed high correlations between the reference GE and both the H10 (r = 0.85, SEE = 4.2) and MS ECG (r = 0.95, SEE = 2.6). Although median values were statistically different via Wilcoxon testing, adjusted median differences were clinically small for the H10 (RF about 1 breaths/min) and trivial for the MS ECG (RF about 0.1 breaths/min). ECG based measurement with the MS ECG showed reduced bias, limits of agreement (maximal bias, -2.0 breaths/min, maximal LoA, 6.1 to -10.0 breaths/min) compared to the H10 (maximal bias, -3.9 breaths/min, maximal LoA, 8.2 to -16.0 breaths/min). In conclusion, RF derived from the combination of the MS ECG sensor with Kubios HRV Premium software, tracked closely to the reference device through an exercise ramp, illustrates the potential for this system to be of practical usage during endurance exercise.

Low- to Moderate-intensity Blood Flow Restricted Walking is not an Acute Equivalent for Unrestricted Jogging in Young Active Adults

This study investigated whether walking with blood flow restriction (BFR) increases acute cardio-respiratory demands to the point that it can be considered an alternative for jogging. Sixteen physically active adults completed five experimental sessions (order randomised), comprising 10 min of treadmill exercise. Two sessions included unrestricted walking, two sessions required walking with BFR cuffs positioned on the lower limbs inflated to 60% of individualised arterial occlusion pressure, and one session was conducted at a jogging pace. Comfortable walking and jogging speeds were calculated during the familiarisation session. Walking speeds were individualised to either 100% (speed: 6.0 ± 0.3km·h^-1[low-intensity]) or 120% (speed: 7.2 ± 0.3km·h^-1[moderate-intensity]) of comfortable walking speed. The jogging session was unrestricted (speed: 9.1 ± 0.7km·h^-1). Initial analysis compared walking conditions across heart rate, left cardiac work index, systolic blood pressure, relative oxygen consumption, minute ventilation, rating of perceived exertion and limb discomfort. Secondary analysis compared the walking session with the highest cardio-respiratory demands to jogging. Initial analysis identified that moderate-intensity with BFR induced the highest cardio-respiratory and perceptual responses compared with any other walking sessions (p < 0.01). Secondary analysis revealed that all cardio-respiratory measures were higher during jogging when compared with moderate-intensity with BFR (p < 0.01), except systolic blood pressure (p = 0.10). All perceptual measures were higher during moderate-intensity with BFR (p < 0.01) compared with jogging. Low- to moderate-intensity BFR-walking produces lower acute cardio-respiratory responses at higher ratings of perceived exertion and discomfort compared with jogging. Overall, BFR-walking does not seem to provide an equivalent exercise modality for unrestricted jogging in physically active adults.

Virtual reality-based distraction on pain, performance, and anxiety during and after moderate-vigorous intensity cycling

PURPOSE

To determine whether increased visual perceptual load (PL) within an immersive virtual environment may help explain previously shown pain-relieving effects of virtual reality (VR) during high intensity cycling.

METHODS

Using a within-subjects design, participants cycled at a perceptually "hard" intensity for 10 min on three separate occasions. The first session did not use VR (i.e., no perceptual load - NPL). Subsequent sessions employed VR during cycling with either a low or high perceptual load (LPL or HPL). Quadriceps pain intensity (PI) was reported by participants throughout cycling.

RESULTS

Data were analyzed for 43 healthy participants (20 females, mean age 21  [SD 1.4]). For PI, ANOVA showed there were significant main effects of condition (F = 13.458, df =1.579, 66.334, p<0.001) and time (F = 113.045, df =1.618, 227.683, p<0.001). At every time point, t-tests revealed mean PI was significantly lower in the NPL than in the LPL condition (t(42)=4.737, p<0.001, d = 0.472) and HPL condition (t(42)=3.380, p = 0.002, d = 0.391). Dependent t-tests showed that more work (kilojoules) was performed during the LPL condition than the NPL (t(42)=2.992, p = 0.005) and HPL (t(42)=5.810, p<0.001) conditions.

CONCLUSIONS

Compared to a traditional 10-minute bout of cycle ergometry (NPL), individuals who cycled in the LPL condition chose to exercise at a higher intensity despite greater PI. Those who cycled in the HPL condition did not change their exercise intensity, but did report higher PI, possibly, because of the greater mental effort/energy requirement.

Breath Tools: A Synthesis of Evidence-Based Breathing Strategies to Enhance Human Running

Running is among the most popular sporting hobbies and often chosen specifically for intrinsic psychological benefits. However, up to 40% of runners may experience exercise-induced dyspnoea as a result of cascading physiological phenomena, possibly causing negative psychological states or barriers to participation. Breathing techniques such as slow, deep breathing have proven benefits at rest, but it is unclear if they can be used during exercise to address respiratory limitations or improve performance. While direct experimental evidence is limited, diverse findings from exercise physiology and sports science combined with anecdotal knowledge from Yoga, meditation, and breathwork suggest that many aspects of breathing could be improved via purposeful strategies. Hence, we sought to synthesize these disparate sources to create a new theoretical framework called “Breath Tools” proposing breathing strategies for use during running to improve tolerance, performance, and lower barriers to long-term enjoyment.

Influence of oral contraceptive phase on cardiorespiratory response to exercise in endurance-trained athletes

OBJECTIVE

The aim of the study was to analyse the cardiorespiratory response to exercise during an oral contraceptive (OC) cycle in endurance-trained women.

METHODS

Sixteen low-dose monophasic OC pill (OCP) users performed an interval-running protocol. The protocol consisted of eight 3 min bouts at 85% of participants' maximal aerobic speed (vV̇o_2peak) with a 90s recovery at 30% vV̇o_2peak in two OC phases: a withdrawal phase (WP) and an active pill phase (APP). The non-parametric Wilcoxon test was applied to analyse differences (p < 0.05) in performance variables between OC cycle phases.

RESULTS

Throughout the high-intensity intervals, higher ventilation (WP 80.90 ± 11.49 L/min, APP 83.10 ± 13.33 L/min; p < 0.001) and relative perceived exertion (WP 14.51 ± 2.58, APP 15.11 ± 3.11; p = 0.001) during the APP were found, whereas carbon dioxide production (WP 2040.92 ± 262.93 mL/min, APP 2010.25 ± 305.68 mL/min; p = 0.003) was higher in the WP. During the active recovery intervals, ventilation (WP 65.78 ± 9.90 L/min, APP 67.88 ± 12.66 L/min; p < 0.001) was higher in the APP, while heart rate (WP 159.93 ± 10.26 bpm, APP 159.74 ± 12.83 bpm; p = 0.029) was higher in the WP.

CONCLUSION

An increase in ventilation occurs during the APP, which is accompanied by higher perceived exertion. Therefore, coaches and athletes should be aware of these variations, especially perceived exertion, in regard to women's training programmes, in order to improve their performance, wellness and adherence to physical activity.

Type of self-talk matters: Its effects on perceived exertion, cardiorespiratory, and cortisol responses during an iso-metabolic endurance exercise

Self-talk is an effective mental training technique that has been shown to facilitate or debilitate an athlete's performance, depending on its valence. Although the effects of self-talk have been supported by observing change in sport performance, little is known about how self-talk can induce physiological changes. Specifically, it is important to understand if the type of self-talk (positive, neutral, or negative) and can influence stress-related parameters, such as perceived exertion, cardiorespiratory, and cortisol responses. The study's objective was therefore to investigate the top-down effect of positive and negative self-talk compared to a dissociative activity during an iso-metabolic running exercise on autonomic regulation of cardiorespiratory function. Twenty-nine well-trained male runners [38 ± 13 years, 177 ± 7 cm and 73 ± 7 kg] volunteered to participate in a randomized-group design study that included a negative self-talk (NST), a positive self-talk, and a dissociative group (DG). First, participants underwent an incremental running test on a treadmill to determine the maximal oxygen uptake (V̇O_2max ). Next, participants received a mental training session on self-talk and created three positive and three negative self-talk statements. Finally, participants underwent a 60-min steady-state running exercise on a treadmill at 70% of V̇O_2max , during which they were cued at 20-, 35-, and 50-min with their personal self-created positive or negative self-talk statements while the DG listened to a documentary. Cardiorespiratory parameters and rate of perceived exertion (RPE) were recorded throughout the 60-min endurance exercise. In addition, salivary cortisol samples were obtained at waking and after treatment. Although oxygen uptake, carbon dioxide production, RPE, and heart rate significantly changed overtime during the 60-min steady-state running exercise, no significant main treatment effect was found. However, RPE scores, minute ventilation, breathing frequency, and salivary cortisol were significantly higher in the NST group compared to the two other groups. These data suggest that NST [emotion-induced stress, as reflected by elevated cortisol] altered the breathing frequency response. In conclusion, manipulating self-talk alters hormonal response patterns, modulates cardiorespiratory function, and influences perceived exertion.

Concentric versus eccentric cycling at equal power output or effort perception: Neuromuscular alterations and muscle pain

This study aimed to compare neuromuscular alterations and perceptions of effort and muscle pain induced by concentric and eccentric cycling performed at the same power output or effort perception. Fifteen participants completed three 30-min sessions: one in concentric at 60% peak power output (CON) and two in eccentric, at the same power output (ECC_POWER ) or same perceived effort (ECC_EFFORT ). Muscle pain, perception of effort, oxygen uptake as well as rectus femoris and vastus lateralis electromyographic activities were collected when pedaling. The knee extensors maximal voluntary contraction (MVC) torque, the torque evoked by double stimulations at 100 Hz and 10 Hz (Dt100; Dt10), and the voluntary activation level (VAL) were evaluated before and after exercise. Power output was higher in ECC_EFFORT than CON (89.1 ± 23.3% peak power). Muscle pain and effort perception were greater in CON than ECC_POWER (p < 0.03) while muscle pain was similar in CON and ECC_EFFORT (p > 0.43). MVC torque, Dt100, and VAL dropped in all conditions (p < 0.04). MVC torque (p < 0.001) and the Dt10/ Dt100 ratio declined further in ECC_EFFORT (p < 0.001). Eccentric cycling perceived as difficult as concentric cycling caused similar muscle pain but more MVC torque decrease. A given power output induced lower perceptions of pain and effort in eccentric than in concentric yet similar MVC torque decline. While neural impairments were similar in all conditions, eccentric cycling seemed to alter excitation-contraction coupling. Clinicians should thus be cautious when setting eccentric cycling intensity based on effort perception.

Non-Invasive Physiological Monitoring for Physical Exertion and Fatigue Assessment in Military Personnel: A Systematic Review

During operational activities, military personnel face extremely demanding circumstances, which when combined lead to severe fatigue, influencing both their well-being and performance. Physical exertion is the main condition leading to fatigue, and its continuous tracking would help prevent its effects. This review aimed to investigate the up-to-date progress on non-invasive physiological monitoring to evaluate situations of physical exertion as a pre-condition to fatigue in military populations, and determine the potential associations between physiological responses and fatigue, which can later result in decision-making indicators to prevent health-related consequences. Adhering to the PRISMA Statement, four databases (Scopus, Science Direct, Web of Science and PubMed) were used for a literature search based on combinations of keywords. The eligibility criteria focused on studies monitoring physiological variables through non-invasive objective measurements, with these measurements being developed in military field, combat, or training conditions. The review process led to the inclusion of 20 studies. The findings established the importance of multivariable assessments in a real-life context to accurately characterise the effects of military practices. A tendency for examining heart rate variables, thermal responses, and actigraphy measurements was also identified. The objectives and experimental protocols were diverse, but the effectiveness of non-invasive measurements in identifying the most fatigue-inducing periods was demonstrated. Nevertheless, no assessment system for standardised application was presented. Future work may include the development of assessment methods to translate physiological recordings into actionable information in real-time and mitigate the effects of fatigue on soldiers’ performance accurately.

Applying ubiquitous sensing to estimate perceived exertion based on cardiorespiratory features

Reliable monitoring of one’s response to exercise intensity is imperative to effectively plan and manage training, but not always practical in impact sports settings. This study aimed to evaluate if an inexpensive mobile cardio-respiratory monitoring system can achieve similar performance to a metabolic cart in estimating rated perceived exertion. Eight adult men volunteered to perform treadmill tests under different conditions. Cardiorespiratory data were collected using a metabolic cart and an instrumented oral-cavity device, as well as their ratings of perceived exertion. Pearson correlation corrected for repeated measurements and stepwise regression analysis were used to observe the relationship between the cardiorespiratory features and the ratings of perceived exertion and determine the proportion of the variance of exertion that could be explained by the measurements. Minute ventilation was found to be the most associated variable to perceived exertion, closely followed by a novel metric called the audio minute volume, which can be collected by the oral-cavity device. A generalised linear model combining minute ventilation, audio minute volume, heart rate and respiration rate accounted for 64% of the variance in perceived exertion, whilst a model with only audio minute volume accounted for 56%. Our study indicates that minute ventilation is key to estimating perceived exertion during indoor running exercises. Audio minute volume was also observed to perform comparably to a lab-based metabolic cart in estimating perceived exertion. This research indicates that mobile techniques offer the potential for real-world data collection of an athlete’s physiological load and estimation of perceived exertion.

On chip optofluidic low-pressure monitoring device

We present an on chip optofluidic surface deformable liquid Dove prism (LDP) based low-fluid flow pressure monitoring device. The unique design of the device in combination with liquid and soft solid enabled by the total internal reflection of light makes the sensor highly sensitive and compatible with the integration of a microfluidic and/or Lab-on-a-chip device. A layer-by-layer soft lithographic (LSL) and 3D printing technique are exploited to make the device. We have used Polydimethylsiloxane (PDMS) as the layer material and two variety of liquids (a) immersion oil (IO) and (b) di-iodomethane (DI) as refracting medium to construct the LDP sensor. Optical ray tracing simulation is performed to optimize the sensor. The pressure sensor shows sensitivity as high as ±28.5 mV per 50 Pa pressure with an error ± 2.5 mV and repeatability of ~99.56% at full scale. We have shown the applicability of the sensor by capturing and analyzing respiratory pressure signals of some human subjects at numerous conditions.

The effect of pedalling cadence on respiratory frequency: passive vs. active exercise of different intensities

PURPOSE

Pedalling cadence influences respiratory frequency (f_R) during exercise, with group III/IV muscle afferents possibly mediating its effect. However, it is unclear how exercise intensity affects the link between cadence and f_R. We aimed to test the hypothesis that the effect of cadence on f_R is moderated by exercise intensity, with interest in the underlying mechanisms.

METHODS

Ten male cyclists performed a preliminary ramp incremental test and three sinusoidal experimental tests on separate visits. The experimental tests consisted of 16 min of sinusoidal variations in cadence between 115 and 55 rpm (sinusoidal period of 4 min) performed during passive exercise (PE), moderate exercise (ME) and heavy exercise (HE). The amplitude (A) and phase lag (φ) of the dependent variables were calculated.

RESULTS

During PE, f_R changed in proportion to variations in cadence (r = 0.85, P < 0.001; A = 3.9 ± 1.4 breaths·min^-1; φ = - 5.3 ± 13.9 degrees). Conversely, the effect of cadence on f_R was reduced during ME (r = 0.73, P < 0.001; A = 2.6 ± 1.3 breaths·min^-1; φ = - 25.4 ± 26.3 degrees) and even more reduced during HE (r = 0.26, P < 0.001; A = 1.8 ± 1.0 breaths·min^-1; φ = - 70.1 ± 44.5 degrees). No entrainment was found in any of the sinusoidal tests.

CONCLUSION

The effect of pedalling cadence on f_R is moderated by exercise intensity-it decreases with the increase in work rate-and seems to be mediated primarily by group III/IV muscle afferents, at least during passive exercise.

The Importance of Respiratory Rate Monitoring: From Healthcare to Sport and Exercise

Respiratory rate is a fundamental vital sign that is sensitive to different pathological conditions (e.g., adverse cardiac events, pneumonia, and clinical deterioration) and stressors, including emotional stress, cognitive load, heat, cold, physical effort, and exercise-induced fatigue. The sensitivity of respiratory rate to these conditions is superior compared to that of most of the other vital signs, and the abundance of suitable technological solutions measuring respiratory rate has important implications for healthcare, occupational settings, and sport. However, respiratory rate is still too often not routinely monitored in these fields of use. This review presents a multidisciplinary approach to respiratory monitoring, with the aim to improve the development and efficacy of respiratory monitoring services. We have identified thirteen monitoring goals where the use of the respiratory rate is invaluable, and for each of them we have described suitable sensors and techniques to monitor respiratory rate in specific measurement scenarios. We have also provided a physiological rationale corroborating the importance of respiratory rate monitoring and an original multidisciplinary framework for the development of respiratory monitoring services. This review is expected to advance the field of respiratory monitoring and favor synergies between different disciplines to accomplish this goal.

Cycling Performance and Training Load: Effects of Intensity and Duration

PURPOSE

To examine the effect of cycling exercise intensity and duration on subsequent performance and to compare the resulting acute performance decrement (APD) with total work done (TWD) and corresponding training-load (TL) metrics.

METHODS

A total of 14 male cyclists performed a 5-minute time trial (TT) as a baseline and after 4 initial exercise bouts of varying exercise intensity and duration. The initial exercise bouts were performed in a random order and consisted of a 5- and a 20-minute TT and a 20- and a 40-minute submaximal ride. The resulting APD was calculated as the percentage change in 5-minute TT from baseline, and this was compared with the TWD and TL metrics for the corresponding initial exercise bout.

RESULTS

Average power output was different for each of the 4 initial exercise bouts (ηp2=.971; P < .001), and all bouts resulted in an APD. But APD was only different when comparing maximal with submaximal bouts (ηp2=.862; P < .001). The APD contradicted TWD and TL metrics and was not different when comparing 5- and 20-minute maximal TTs or the 20- and 40-minute submaximal bouts. In contrast, TL metrics were different for all training sessions (ηp2=.970; P < .001).

CONCLUSION

An APD is found after initial exercise bouts consisting of 5- and 20-minute TTs and after 20- and 40-minute of submaximal exercise that is not consistent with the corresponding values for TWD or TL. This discrepancy highlights important shortcomings when using TWD and TL to compare exercise bouts of different intensity and duration.

Maximal Lactate Steady State Versus the 20-Minute Functional Threshold Power Test in Well-Trained Individuals: "Watts" the Big Deal?

PURPOSE

To (1) compare the power output (PO) for both the 20-minute functional threshold power (FTP20) field test and the calculated 95% (FTP95%) with PO at maximal lactate steady state (MLSS) and (2) evaluate the sensitivity of FTP95% and MLSS to training-induced changes.

METHODS

Eighteen participants (12 males: 37 [6] y and 6 females: 28 [6] y) performed a ramp-incremental cycling test to exhaustion, 2 to 3 constant-load MLSS trials, and an FTP20 test. A total of 10 participants returned to repeat the test series after 7 months of training.

RESULTS

The PO at FTP20 and FTP95% was greater than that at MLSS (P = .00), with the PO at MLSS representing 88.5% (4.8%) and 93.1% (5.1%) of FTP and FTP95%, respectively. MLSS was greater at POST compared with PRE training (12 [8] W) (P = .002). No increase was observed in mean PO at FTP20 and FTP95% (P = .75).

CONCLUSIONS

The results indicate that the PO at FTP95% is different to MLSS, and that changes in the PO at MLSS after training were not reflected by FTP95%. Even when using an adjusted percentage (ie, 88% rather than 95% of FTP20), the large variability in the data is such that it would not be advisable to use this as a representation of MLSS.

Respiratory Frequency as a Marker of Physical Effort During High-Intensity Interval Training in Soccer Players

PURPOSE

Variables currently used in soccer training monitoring fail to represent the physiological demand of the player during movements like accelerations, decelerations, and directional changes performed at high intensity. We tested the hypothesis that respiratory frequency (fR) is a marker of physical effort during soccer-related high-intensity exercise.

METHODS

A total of 12 male soccer players performed a preliminary intermittent incremental test and 2 shuttle-run high-intensity interval training (HIIT) protocols, in separate visits. The 2 HIIT protocols consisted of 12 repetitions over 9 minutes and differed in the work-to-recovery ratio (15:30 vs 30:15 s). Work rate was self-paced by participants to achieve the longest possible total distance in each HIIT protocol.

RESULTS

Work-phase average metabolic power was higher (P < .001) in the 15:30-second protocol (31.7 [3.0] W·kg-1) compared with the 30:15-second protocol (22.8 [2.0] W·kg-1). Unlike heart rate and oxygen uptake, fR showed a fast response to the work-recovery alternation during both HIIT protocols, resembling changes in metabolic power even at supramaximal intensities. Large correlations (P < .001) were observed between fR and rating of perceived exertion during both 15:30-second (r = .87) and 30:15-second protocols (r = .85).

CONCLUSIONS

Our findings suggest that fR is a good marker of physical effort during shuttle-run HIIT in soccer players. These findings have implications for monitoring training in soccer and other team sports.

Cardiorespiratory Responses to Endurance Exercise Over the Menstrual Cycle and With Oral Contraceptive Use

Barba-Moreno, L, Cupeiro, R, Romero-Parra, N, Janse de Jonge, XA, and Peinado, AB. Cardiorespiratory Responses to Endurance Exercise Over the Menstrual Cycle and With Oral Contraceptive Use. J Strength Cond Res XX(X): 000-000, 2019-Female steroid hormone fluctuations during the menstrual cycle and exogenous hormones from oral contraceptives may have potential effects on exercise performance. The aim of this study was to investigate the effects of these fluctuations on cardiorespiratory responses during steady-state exercise in women. Twenty-three healthy endurance-trained women performed 40 minutes of running at 75% of their maximal aerobic speed during different phases of the menstrual cycle (n = 15; early follicular phase, midfollicular phase, and luteal phase) or oral contraceptive cycle (n = 8; hormonal phase and nonhormonal phase). Ventilatory parameters and heart rate (HR) were measured. Data were analyzed using a mixed linear model. For the eumenorrheic group, significantly higher oxygen uptake (p = 0.049) and percentage of maximum oxygen uptake (p = 0.035) were observed during the midfollicular phase compared with the early follicular. Heart rate (p = 0.004), oxygen ventilatory equivalent (p = 0.042), carbon dioxide ventilatory equivalent (p = 0.017), and tidal volume (p = 0.024) increased during luteal phase in comparison with midfollicular. In oral contraceptive users, ventilation (p = 0.030), breathing frequency (p = 0.018), oxygen ventilatory equivalent (p = 0.032), and carbon dioxide ventilatory equivalent (p = 0.001) increased during the hormonal phase. No significant differences were found for the rest of the parameters or phases. Both the eumenorrheic group and oral contraceptive group showed a significant increase in some ventilatory parameters during luteal and hormonal phases, respectively, suggesting lower cardiorespiratory efficiency. However, the lack of clinical meaningfulness of these differences and the nondifferences of other physiological variables, indicate that the menstrual cycle had a small impact on submaximal exercise in the current study.

Veterans with Gulf War Illness exhibit distinct respiratory patterns during maximal cardiopulmonary exercise

INTRODUCTION

The components of minute ventilation, respiratory frequency and tidal volume, appear differentially regulated and thereby afford unique insight into the ventilatory response to exercise. However, respiratory frequency and tidal volume are infrequently reported, and have not previously been considered among military veterans with Gulf War Illness. Our purpose was to evaluate respiratory frequency and tidal volume in response to a maximal cardiopulmonary exercise test in individuals with and without Gulf War Illness.

MATERIALS AND METHODS

20 cases with Gulf War Illness and 14 controls participated in this study and performed maximal cardiopulmonary exercise test on a cycle ergometer. Ventilatory variables (minute ventilation, respiratory frequency and tidal volume) were obtained and normalized to peak exercise capacity. Using mixed-design analysis of variance models, with group and time as factors, we analyzed exercise ventilatory patterns for the entire sample and for 11 subjects from each group matched for race, age, sex, and height.

RESULTS

Despite similar minute ventilation (p = 0.57, η2p = 0.01), tidal volume was greater (p = 0.02, η2p = 0.16) and respiratory frequency was lower (p = 0.004, η2p = 0.24) in Veterans with Gulf War Illness than controls. The findings for respiratory frequency remained significant in the matched subgroup (p = 0.004, η2p = 0.35).

CONCLUSION

In our sample, veterans with Gulf War Illness adopt a unique exercise ventilatory pattern characterized by reduced respiratory frequency, despite similar ventilation relative to controls. Although the mechanism(s) by which this pattern is achieved remains unresolved, our findings suggest that the components of ventilation should be considered when evaluating clinical conditions with unexplained exertional symptoms.

Internal training load monitoring in professional football: a systematic review of methods using rating of perceived exertion

INTRODUCTION

The rate of perceived exertion (RPE) is widely adopted to quantify internal training load (ITL) in professional football. The aim of this study was to systematically review the use RPE-based methods in professional football.

EVIDENCE ACQUISITION

Observational studies conducted during training routines of professional football players over a minimum of one-week were selected based on the preferred reporting items for systematic reviews and meta-analyses statement.

EVIDENCE SYNTHESIS

Thirty-eight articles met the inclusion criteria (average qualitative score was 6.3 out of 10 [3 to 9]). The main deficiencies identified concerned the poor description of study design (~52% of the studies), and the non-quantification of match load (~44%). Ten studies complemented RPE-based ITL information with time-motion analysis (~26%) and seven studies added HR recordings (~18%). Nine studies collected RPE data after complementary training, separately to field sessions (~3%). Operational questions (e.g. How was your workout? ~71%) were preferred to instructions (e.g. Please rate the intensity of today's session; ~8%). Session-RPE (s-RPE; RPE multiplied by training duration) was more commonly adopted as measure of exercise intensity than isolated RPE (~76 vs. ~8%). RPE-derived variables calculated on weekly values included absolute week-to-week change, acute: chronic workload ratio, monotony and strain and were not frequently used (7 to 15%). Four studies (~11%) divided RPE in two components: respiratory and muscular.

CONCLUSIONS

There is a lack of consensus for the use of RPE in professional football and "good practices" are warranted. This review might help practitioners regarding procedures to adopt in RPE data collection and interpretation.

A comparison of different methods to analyse data collected during time-to-exhaustion tests

Purpose

Despite their widespread use in exercise physiology, time-to-exhaustion (TTE) tests present an often-overlooked challenge to researchers, which is how to computationally deal with between- and within-subject differences in exercise duration. We aimed to verify the best analysis method to overcome this problem.

Methods

Eleven cyclists performed an incremental test and three TTE tests differing in workload as preliminary tests. The TTEs were used to derive the individual power–duration relationship needed to set the workload (corresponding to an estimated TTE of 1200 s) for four identical experimental TTE tests. Within individuals, the four tests were subsequently rank ordered by performance. Physiological and psychological variables expected to change with performance were analysed using different methods, with the main aim being to compare the traditional “group isotime” method and a less-used “individual isotime” method.

Results

The four tests, ranked from the best to the worst, had a TTE of 1526 ± 332, 1425 ± 313, 1295 ± 325, and 1026 ± 265 s. Ratings of perceived exertion, minute ventilation, respiratory frequency, and affective valence were sensitive to changes in performance when their responses were analysed with the “individual isotime” method (P < 0.022, ηp2 > 0.144) but not when using the “group isotime” method, because the latter resulted in partial data loss.

Conclusions

The use of the “individual isotime” method is strongly encouraged to avoid the misinterpretation of the phenomenon under study. Important implications are not limited to constant-workload exercise, but extend to incremental exercise, which is another commonly used test of exercise tolerance.

A Sensor Platform for Athletes' Training Supervision: A Proof of Concept Study

One of the basic needs of professional athletes is the real-time and non-invasive monitoring of their activities. The use of these kind of data is necessary to develop strategies for specific tailored training in order to improve performances. The sensor system presented in this work has the aim to adopt a novel approach for the monitoring of physiological parameters, and athletes' performances, during their training. The anaerobic threshold is herein identified with the monitoring of the lactate concentration and the respiratory parameters. The data collected by the sensor are used to build a model using a supervised method (based on the partial least squares method, PLS) to predict the values of the parameters of interest. The sensor is able to measure the lactate concentration from a sample of saliva and it can estimate a respiratory parameter, such as maximal oxygen consumption, maximal carbon dioxide production and respiratory rate from a sample of exhaled breath. The main advantages of the device are the low power; the wireless communication; and the non-invasive sampling method, which allow its use in a real context of sport practice.

Treadmill running using an RPE-clamp model: mediators of perception and implications for exercise prescription

PURPOSE

The mediators of the perception of effort during exercise are still unclear. The aim of the present study was to examine physiological responses during runs using a rating of perceived exertion (RPE)-clamp model at the RPE corresponding to the gas exchange threshold (RPE_GET) and 15% above GET (RPE_GET+15%) to identify potential mediators and performance applications for RPE during treadmill running.

METHODS

Twenty-one runners ([Formula: see text]_max = 51.7 ± 8.3 ml kg^-1 min^-1) performed a graded exercise test to determine maximal oxygen consumption and the RPE associated with GET and GET + 15% followed by randomized 60 min RPE-clamp runs at RPE_GET and RPE_GET+15%. Mean differences for [Formula: see text], heart rate (HR), minute ventilation ([Formula: see text]), respiratory frequency ([Formula: see text], respiratory exchange ratio (RER), and velocity were compared across each run.

RESULTS

After minute 14, [Formula: see text], RER and velocity did not differ across conditions, but decreased across time (p < 0.05). There was a significant (p < 0.05) condition × time interaction for [Formula: see text], where values were significantly higher during RPE-clamp runs at RPE_GET+15% and decreased across time in both conditions. There were no differences across condition or time for HR, and only small difference between conditions for [Formula: see text].

CONCLUSIONS

HR and [Formula: see text] may play a role in mediating the perception of effort, while [Formula: see text], RER, and [Formula: see text] may not. Although HR and [Formula: see text] may mediate the maintenance of a perceptual intensity, they may not be sensitive to differentiate perceptual intensities at GET and GET + 15%. Thus, prescribing exercise using an RPE-clamp model may only reflect a sustainable [Formula: see text] within the moderate intensity domain.

Neuromuscular and Perceptual Responses to Sub-Maximal Eccentric Cycling

Objective

Eccentric (ECC) cycle-ergometers have recently become commercially-available, offering a novel method for rehabilitation training. Many studies have reported that ECC cycling enables the development of higher levels of muscular force at lower cardiorespiratory and metabolic loads, leading to greater force enhancements after a training period. However, fewer studies have focused on the specific perceptual and neuromuscular changes. As the two latter aspects are of major interest in clinical settings, this review aimed to present an overview of the current literature centered on the neuromuscular and perceptual responses to submaximal ECC cycling in comparison to concentric (CON) cycling.

Design

Narrative review of the literature.

Results

At a given mechanical workload, muscle activation is lower in ECC than in CON while the characteristics of the musculo-articular system (i.e., muscle-tendon unit, fascicle, and tendinous tissue length) are quite similar. At a given heart rate or oxygen consumption, ECC cycling training results in greater muscular hypertrophy and strength gains than CON cycling. On the contrary, CON cycling training seems to enhance more markers of muscle aerobic metabolism than ECC cycling performed at the same heart rate intensity. Data concerning perceptual responses, and neuromuscular mechanisms leading to a lower muscle activation (i.e., neural commands from cortex to muscular system) at a given mechanical workload are scarce.

Conclusion

Even though ECC cycling appears to be a very useful tool for rehabilitation purposes the perceptual and neural commands from cortex to muscular system during exercise need to be further studied.

Relationship between External Load and Perceptual Responses to Training in Professional Football: Effects of Quantification Method

We examined the within-player correlation between external training load (ETL) and perceptual responses to training in a professional male football team (n = 13 outfield players) over an eight-week competitive period. ETL was collected using 10-Hz GPS, whereas perceptual responses were accessed through rating of perceived exertion (RPE) questionnaires. Moderate-speed running (MSR), high-speed running (HSR) and sprinting were defined using arbitrary (fixed) and individualised speed zones (based on maximal aerobic speed and maximal sprinting speed). When ETL was expressed as actual distance covered within the training session, perceptual responses were moderately correlated to MSR and HSR quantified using the arbitrary method (p < 0.05; r = 0.53 to 0.59). However, the magnitude of correlations tended to increase when the individualised method was used (p < 0.05; r = 0.58 to 0.67). Distance covered by sprinting was moderately correlated to perceptual responses only when the individualised method was used (p < 0.05; 0.55 [0.05; 0.83] and 0.53 [0.02; 0.82]). Perceptual responses were largely correlated to the sum of distance covered within all three speed running zones, irrespective of the quantification method (p < 0.05; r = 0.58 to 0.68). When ETL was expressed as percentage of total distance covered within the training session, no significant correlations were observed (p > 0.05). Perceptual responses to training load seem to be better associated with ETL, when the latter is adjusted to individual fitness capacities. Moreover, reporting ETL as actual values of distance covered within the training session instead of percentual values inform better about players’ perceptual responses to training load.

The effect of severe and moderate hypoxia on exercise at a fixed level of perceived exertion

Purpose

The purpose of this study was to determine the primary cues regulating perceived effort and exercise performance using a fixed-RPE protocol in severe and moderate hypoxia.

Methods

Eight male participants (26 ± 6 years, 76.3 ± 8.6 kg, 178.5 ± 3.6 cm, 51.4 ± 8.0 mL kg^− 1 min^− 1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot {V}$$\end{document}V˙O_2max) completed three exercise trials in environmental conditions of severe hypoxia (F_IO₂ 0.114), moderate hypoxia (F_IO₂ 0.152), and normoxia (F_IO₂ 0.202). They were instructed to continually adjust their power output to maintain a perceived effort (RPE) of 16, exercising until power output declined to 80% of the peak 30-s power output achieved.

Results

Exercise time was reduced (severe hypoxia 428 ± 210 s; moderate hypoxia 1044 ± 384 s; normoxia 1550 ± 590 s) according to a reduction in F_IO₂ (P < 0.05). The rate of oxygen desaturation during the first 3 min of exercise was accelerated in severe hypoxia (− 5.3 ± 2.8% min^− 1) relative to moderate hypoxia (− 2.5 ± 1.0% min^− 1) and normoxia (− 0.7 ± 0.3% min^− 1). Muscle tissue oxygenation did not differ between conditions (P > 0.05). Minute ventilation increased at a faster rate according to a decrease in F_IO₂ (severe hypoxia 27.6 ± 6.6; moderate hypoxia 21.8 ± 3.9; normoxia 17.3 ± 3.9 L min^− 1). Moderate-to-strong correlations were identified between breathing frequency (r = − 0.718, P < 0.001), blood oxygen saturation (r = 0.611, P = 0.002), and exercise performance.

Conclusions

The primary cues for determining perceived effort relate to progressive arterial hypoxemia and increases in ventilation.

Contact-Based Methods for Measuring Respiratory Rate

There is an ever-growing demand for measuring respiratory variables during a variety of applications, including monitoring in clinical and occupational settings, and during sporting activities and exercise. Special attention is devoted to the monitoring of respiratory rate because it is a vital sign, which responds to a variety of stressors. There are different methods for measuring respiratory rate, which can be classed as contact-based or contactless. The present paper provides an overview of the currently available contact-based methods for measuring respiratory rate. For these methods, the sensing element (or part of the instrument containing it) is attached to the subject's body. Methods based upon the recording of respiratory airflow, sounds, air temperature, air humidity, air components, chest wall movements, and modulation of the cardiac activity are presented. Working principles, metrological characteristics, and applications in the respiratory monitoring field are presented to explore potential development and applicability for each method.

Putative Role of Respiratory Muscle Training to Improve Endurance Performance in Hypoxia: A Review

Respiratory/inspiratory muscle training (RMT/IMT) has been proposed to improve the endurance performance of athletes in normoxia. In recent years, due to the increased use of hypoxic training method among athletes, the RMT applicability has also been tested as a method to minimize adverse effects since hyperventilation may cause respiratory muscle fatigue during prolonged exercise in hypoxia. We performed a review in order to determine factors potentially affecting the change in endurance performance in hypoxia after RMT in healthy subjects. A comprehensive search was done in the electronic databases MEDLINE and Google Scholar including keywords: “RMT/IMT,” and/or “endurance performance,” and/or “altitude” and/or “hypoxia.” Seven appropriate studies were found until April 2018. Analysis of the studies showed that two RMT methods were used in the protocols: respiratory muscle endurance (RME) (isocapnic hyperpnea: commonly 10–30′, 3–5 d/week) in three of the seven studies, and respiratory muscle strength (RMS) (Powerbreathe device: commonly 2 × 30 reps at 50% MIP (maximal inspiratory pressure), 5–7 d/week) in the remaining four studies. The duration of the protocols ranged from 4 to 8 weeks, and it was found in synthesis that during exercise in hypoxia, RMT promoted (1) reduced respiratory muscle fatigue, (2) delayed respiratory muscle metaboreflex activation, (3) better maintenance of SaO₂ and blood flow to locomotor muscles. In general, no increases of maximal oxygen uptake (VO_2max) were described. Ventilatory function improvements (maximal inspiratory pressure) achieved by using RMT fostered the capacity to adapt to hypoxia and minimized the impact of respiratory stress during the acclimatization stage in comparison with placebo/sham. In conclusion, RMT was found to elicit general positive effects mainly on respiratory efficiency and breathing patterns, lower dyspneic perceptions and improved physical performance in conditions of hypoxia. Thus, this method is recommended to be used as a pre-exposure tool for strengthening respiratory muscles and minimizing the adverse effects caused by hypoxia related hyperventilation. Future studies will assess these effects in elite athletes.

Respiratory frequency and tidal volume during exercise: differential control and unbalanced interdependence

Differentiating between respiratory frequency (fR ) and tidal volume (VT ) may improve our understanding of exercise hyperpnoea because fR and VT seem to be regulated by different inputs. We designed a series of exercise manipulations to improve our understanding of how fR and VT are regulated during exercise. Twelve cyclists performed an incremental test and three randomized experimental sessions in separate visits. In two of the three experimental visits, participants performed a moderate-intensity sinusoidal test followed, after recovery, by a moderate-to-severe-intensity sinusoidal test. These two visits differed in the period of the sinusoid (2 min vs. 8 min). In the third experimental visit, participants performed a trapezoidal test where the workload was self-paced in order to match a predefined trapezoidal template of rating of perceived exertion (RPE). The results collectively reveal that fR changes more with RPE than with workload, gas exchange, VT or the amount of muscle activation. However, fR dissociates from RPE during moderate exercise. Both VT and minute ventilation ( V ˙ E ) showed a similar time course and a large correlation with V ˙ CO 2 in all the tests. Nevertheless, V ˙ CO 2 was associated more with V ˙ E than with VT because VT seems to adjust continuously on the basis of fR levels to match V ˙ E with V ˙ CO 2 . The present findings provide novel insight into the differential control of fR and VT - and their unbalanced interdependence - during exercise. The emerging conceptual framework is expected to guide future research on the mechanisms underlying the long-debated issue of exercise hyperpnoea.

Determining day-to-day human variation in indirect calorimetry using Bayesian decision theory

NEW FINDINGS

What is the central question of this study? We sought to understand the day-to-day variability of human indirect calorimetry during rest and exercise. Previous work has been unable to separate human day-to-day variability from measurement error and within-trial human variability. We developed models accounting for different levels of human- and machine-level variance and compared the probability density functions using total variation distance. What is the main finding and its importance? After accounting for multiple levels of variance, the average human day-to-day variability of minute ventilation, CO₂ output and O₂ uptake is 4.0, 1.8 and 2.0%, respectively. This is a new method to understand human variability and directly enhances our understanding of human variance during indirect calorimetry.

ABSTRACT

One of the challenges of precision medicine is understanding when serial measurements taken across days are quantifiably different from each other. Previous work examining gas exchange measured by indirect calorimetry has been unable to separate differential measurement error, within-trial human variance and day-to-day human variance effectively in order to ascertain how variable humans are across testing sessions. We used previously published reliability data to construct models of indirect calorimetry variance and compare these models with methods arising from Bayesian decision theory. These models are conditional on the data upon which they are derived and assume that errors conform to a truncated normal distribution. A serial analysis of modelled probability density functions demonstrated that the average human day-to-day variance in minute ventilation ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub><mml:mover><mml:mi>V</mml:mi> <mml:mo>̇</mml:mo></mml:mover> <mml:mi>E</mml:mi></mml:msub> </mml:math> ), carbon dioxide output ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub><mml:mover><mml:mi>V</mml:mi> <mml:mo>̇</mml:mo></mml:mover> <mml:mrow><mml:mi>C</mml:mi> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> </mml:msub> </mml:math> ) and oxygen uptake ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub><mml:mover><mml:mi>V</mml:mi> <mml:mo>̇</mml:mo></mml:mover> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:msub> </mml:math> ) was 4.0, 1.8 and 2.0%, respectively. However, the average day-to-day variability masked a wide range of non-linear variance across flow rates, particularly for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub><mml:mover><mml:mi>V</mml:mi> <mml:mo>̇</mml:mo></mml:mover> <mml:mi>E</mml:mi></mml:msub> </mml:math> . This is the first report isolating day-to-day human variability in indirect calorimetry gas exchange from other sources of variability. This method can be extended to other physiological tools, and an extension of this work facilitates a statistical tool to examine within-trial <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub><mml:mover><mml:mi>V</mml:mi> <mml:mo>̇</mml:mo></mml:mover> <mml:msub><mml:mi>O</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:msub> </mml:math> differences, available in a graphical user interface.

The Effects of Sodium Phosphate Supplementation on Physiological Responses to Submaximal Exercise and 20 km Cycling Time-Trial Performance

The aim of this study was to examine the effects of sodium phosphate (SP) supplementation on physiological responses to submaximal exercise and 20 km cycling time-trial performance. Using a randomized, double-blind, crossover design, 20 endurance-trained male cyclists (age: 31 ± 6 years; height: 1.82 ± 0.07 m; body mass: 76.3 ± 7.0 kg; maximal oxygen uptake [V̇O_2max]: 57.9 ± 5.5 mL·kg^-1·min^-1) completed two supplementation trials separated by a 14-day washout period. The trials consisted of 10 minutes of cycling at 65% V̇O_2max followed by a 20 km time trial. Expired air was monitored throughout each trial for the evaluation of V̇O₂, minute ventilation (V̇_E), and respiratory exchange ratio (RER). Heart rate was monitored during each trial along with ratings of perceived exertion (RPE) and blood lactate concentration. For four days before each trial, participants ingested 50 mg·kg fat-free mass^-1·day^-1 of either SP or placebo. There were no effects (p ≥ .05) of supplementation on physiological responses during cycling at 65% V̇O_2max. There were also no effects of supplementation on time-trial performance (placebo: 32.8 ± 2.2 min; SP: 32.8 ± 2.3 min). Nevertheless, relative to placebo, SP increased V̇_E (mean difference: 3.81 L·min^-1; 95% confidence interval: [0.16, 7.46 L·min^-1]), RER (mean difference: 0.020; 95% confidence interval: [0.004, 0.036]), and RPE (mean difference: 0.39; 95% confidence interval: [0.04, 0.73]) during time trials, as well as post time-trial blood lactate concentration (mean difference: 1.06 mmol·L^-1; 95% confidence interval: [0.31, 1.80 mmol·L^-1]). In conclusion, SP supplementation has no significant effects on submaximal physiological responses or 20 km time-trial performance.

Effects of submaximal cycling at different exercise intensities on maximal isometric force output of the non-exercised elbow flexor muscles

The purpose of this study was to examine the effects of submaximal cycling at different exercise intensities on maximal isometric force output of the non-exercised elbow flexor muscles after the cycling. A total of 8 healthy young men performed multiple maximal voluntary contractions by the right elbow flexion before, immediately after, 5 min after, and 10 min after a 6-min submaximal cycling at ventilatory threshold (LI), 70% [Formula: see text] (MI), and 80% [Formula: see text] (HI) with both arms relaxed in the air. Force and surface electromyogram (EMG) of the right biceps brachii muscle during the multiple MVCs, blood lactate concentration ([La]), cardiorespiratory responses, and sensations of fatigue for legs (SEF-L) were measured before, immediately after, 5 min after, and 10 min after the submaximal cycling with the three different exercise intensities. Immediately after the submaximal cycling, [La], cardiorespiratory responses, and SEF-L were enhanced in proportion to an increase in exercise intensity of the cycling. Changes in force and EMG activity during the multiple MVCs were not significantly different across the three conditions. The findings imply that group III/IV muscle afferent feedback after the submaximal cycling does not determine the magnitude of MVC force loss of the non-exercised upper limb muscles.

A Wearable System for Real-Time Continuous Monitoring of Physical Activity

Over the last decades, wearable systems have gained interest for monitoring of physiological variables, promoting health, and improving exercise adherence in different populations ranging from elite athletes to patients. In this paper, we present a wearable system for the continuous real-time monitoring of respiratory frequency (f_R), heart rate (HR), and movement cadence during physical activity. The system has been experimentally tested in the laboratory (by simulating the breathing pattern with a mechanical ventilator) and by collecting data from one healthy volunteer. Results show the feasibility of the proposed device for real-time continuous monitoring of f_R, HR, and movement cadence both in resting condition and during activity. Finally, different synchronization techniques have been investigated to enable simultaneous data collection from different wearable modules.