Development and Validity of the Rating-of-Fatigue Scale

Wearable heart rate sensing and critical power-based whole-body fatigue monitoring in the field

Whole-body fatigue (WBF) presents a concerning risk to construction workers, which can impact function and ultimately lead to accidents and diminished productivity. This study proposes a new WBF monitoring technique by applying the Critical Power (CP) model, a bioenergetic model, with a wrist-worn heart rate sensor. The authors modified the CP model to calculate WBF from the percentage of heart rate reserve (%HRR) and generated a personalized model via WBF perception surveys. Data were collected for two days from 33 workers at four construction sites. The results showed that the proposed technique can monitor field workers' perceived WBF with a mean absolute error of 12.8% and Spearman correlation coefficient of 0.83. This study, therefore, demonstrates the viability of wearable WBF monitoring on construction sites to support programs aimed at improving workplace safety and productivity.

Acute psycho-physiological responses to submaximal constant-load cycling under intermittent hypoxia-hyperoxia vs. hypoxia-normoxia in young males

Background

Hypoxia and hyperoxia can affect the acute psycho-physiological response to exercise. Recording various perceptual responses to exercise is of particular importance for investigating behavioral changes to physical activity, given that the perception of exercise-induced pain, discomfort or unpleasure, and a low level of exercise enjoyment are commonly associated with a low adherence to physical activity. Therefore, this study aimed to compare the acute perceptual and physiological responses to aerobic exercise under intermittent hypoxia-hyperoxia (IHHT), hypoxia-normoxia (IHT), and sustained normoxia (NOR) in young, recreational active, healthy males.

Methods

Using a randomized, single-blinded, crossover design, 15 males (age: 24.5 ± 4.2 yrs) performed 40 min of submaximal constant-load cycling (at 60% peak oxygen uptake, 80 rpm) under IHHT (5 × 4 min hypoxia and hyperoxia), IHT (5 × 4 min hypoxia and normoxia), and NOR. Inspiratory fraction of oxygen during hypoxia and hyperoxia was set to 14% and 30%, respectively. Heart rate (HR), total hemoglobin (tHb) and muscle oxygen saturation (SmO2) of the right vastus lateralis muscle were continuously recorded during cycling. Participants' peripheral oxygen saturation (SpO2) and perceptual responses (i.e., perceived motor fatigue, effort perception, perceived physical strain, affective valence, arousal, motivation to exercise, and conflict to continue exercise) were surveyed prior, during (every 4 min), and after cycling. Prior to and after exercise, peripheral blood lactate concentration (BLC) was determined. Exercise enjoyment was ascertained after cycling. For statistical analysis, repeated measures analyses of variance were conducted.

Results

No differences in the acute perceptual responses were found between conditions (p ≥ 0.059, ηp 2 ≤ 0.18), while the physiological responses differed. Accordingly, SpO2 was higher during the hyperoxic periods during the IHHT compared to the normoxic periods during the IHT (p < 0.001, ηp 2 = 0.91). Moreover, HR (p = 0.005, ηp 2 = 0.33) and BLC (p = 0.033, ηp 2 = 0.28) were higher during IHT compared to NOR. No differences between conditions were found for changes in tHb (p = 0.684, ηp 2 = 0.03) and SmO2 (p = 0.093, ηp 2 = 0.16).

Conclusion

IHT was associated with a higher physiological response and metabolic stress, while IHHT did not lead to an increase in HR and BLC compared to NOR. In addition, compared to IHT, IHHT seems to improve reoxygenation indicated by a higher SpO2 during the hyperoxic periods. However, there were no differences in perceptual responses and ratings of exercise enjoyment between conditions. These results suggest that replacing normoxic by hyperoxic reoxygenation-periods during submaximal constant-load cycling under intermittent hypoxia reduced the exercise-related physiological stress but had no effect on perceptual responses and perceived exercise enjoyment in young recreational active healthy males.

The effect of fatigue on peak Achilles tendon force in Irish dancing-specific landing tasks

Achilles tendinopathy is prevalent among Irish dancers, believed to be due to aesthetic technical requirements and high-impact landing tasks. However, the peak Achilles tendon force during Irish dancing-specific landing tasks has not been quantified. Furthermore, the influence of fatigue is unclear. This study aimed to quantify the peak Achilles tendon force during three common Irish dancing landing tasks and investigate the effects of fatigue on this force. Twelve nationally competitive Irish dancers completed the landing tasks prior to and following a fatigue protocol. A Vicon motion analysis system and AMTI force plates were used to calculate sagittal plane ankle joint kinematics during landing to estimate peak Achilles tendon force. Three independent measures (Rating-of-Fatigue scale, Flight time: Contraction during a counter movement jump and jump height during the landing trials) were used to evaluate participant fatigue between conditions. Results revealed a significant difference in peak Achilles tendon force between the three landing tasks, however, no significant difference was observed between pre- and post-fatigue. Further research is required to investigate the effects of the landing technique used in Irish Dancing on peak Achilles tendon force with the aim to reduce peak Achilles tendon force and the risk of developing Achilles tendinopathy.

Hematological and performance adaptations to altitude training (2,320 m) in elite middle-distance and distance swimmers

Purpose

Elite swimmers often schedule altitude training camps ahead of major events in an attempt to maximize performance. However, the relationships between altitude-induced hematological changes, markers of training adaptation, and performance changes in such context are unclear. This study assessed hematological status, markers of daily adaptation, and swimming performance in elite middle-distance and distance swimmers during a 22-day altitude training camp at 2,320 m, 2 weeks prior to World Championship qualification competition.

Methods

Venous blood was obtained and total hemoglobin mass (tHbmass) measured (CO rebreathing) in 7 elite swimmers (4 females, 3 males) 8 days before and on day 22 of the altitude camp. Resting heart rate, peripheral oxygen saturation, urinary specific gravity, body mass, fatigue and self-reported sleep duration and quality were monitored daily during the altitude camp. Swimming performance was assessed through a standardized set (6 sets of 4 maximal repetitions of 100 m front crawl) on days 3, 10 and 17 of the camp, and at sea level competitions (200 m-1,500 m) immediately after the camp, and 2 weeks later.

Results

tHbmass (+5.6 ± 3.3%; range: 2.1%-11.0%; p < 0.05), red blood cell count, hemoglobin concentration, hematocrit increased at the end of the training camp (p < 0.05). Performance at altitude improved throughout the camp (+1.4 ± 0.4%; range: 0.7%-2.5%; p < 0.05). No significant relationship was noted between hematological changes, the change in altitude performance and any of the monitored daily markers of adaptation during the camp. Compared to the swimmers' previous personal best, competition performances did not improve immediately (2.5% ± 1.9% slower times) and 2 weeks after altitude (1.2% ± 1.4% slower times).

Conclusion

The 22-day altitude training camp at 2,320 m was beneficial for elite swimmers' tHbmass, hematological status and performance at altitude, but these benefits did not clearly translate into enhanced sea level performance immediately after or 2 weeks later. The present study confirms the large inter-individual variability in hematological responses to altitude training, and that the improvement in performance at altitude and sea level may depend on factors other than the increase in tHbmass alone.

Multicomponent Support Program for Secondary Prevention of Stroke Using Digital Health Technology: Co-Design Study With People Living With Stroke or Transient Ischemic Attack

BACKGROUND

Few individuals (<2%) who experience a stroke or transient ischemic attack (TIA) participate in secondary prevention lifestyle programs. Novel approaches that leverage digital health technology may provide a viable alternative to traditional interventions that support secondary prevention in people living with stroke or TIA. To be successful, these strategies should focus on user needs and preferences and be acceptable to clinicians and people living with stroke or TIA.

OBJECTIVE

This study aims to co-design, with people with lived experience of stroke or TIA (referred to as consumers) and clinicians, a multicomponent digital technology support program for secondary prevention of stroke.

METHODS

A consumer user needs survey (108 items) was distributed through the Australian Stroke Clinical Registry and the Stroke Association of Victoria. An invitation to a user needs survey (135 items) for clinicians was circulated via web-based professional forums and national organizations (eg, the Stroke Telehealth Community of Practice Microsoft Teams Channel) and the authors' research networks using Twitter (subsequently rebranded X, X Corp) and LinkedIn (LinkedIn Corp). Following the surveys, 2 rounds of user experience workshops (design and usability testing workshops) were completed with representatives from each end user group (consumers and clinicians). Feedback gathered after each round informed the final design of the digital health program.

RESULTS

Overall, 112 consumers (male individuals: n=63, 56.3%) and 54 clinicians (female individuals: n=43, 80%) responded to the survey; all items were completed by 75.8% (n=85) of consumers and 78% (n=42) of clinicians. Most clinicians (46/49, 94%) indicated the importance of monitoring health and lifestyle measures more frequently than current practice, particularly physical activity, weight, and sleep. Most consumers (87/96, 90%) and clinicians (41/49, 84%) agreed that providing alerts about potential deterioration in an individual's condition were important functions for a digital program. Intention to use a digital program for stroke prevention and discussing the data collected during face-to-face consultations was high (consumers: 79/99, 80%; clinicians 36/42, 86%). In addition, 7 consumers (male individuals: n=5, 71%) and 9 clinicians (female individuals: n=6, 67%) took part in the user experience workshops. Participants endorsed using a digital health program to help consumers manage stroke or TIA and discussed preferred functions and health measures in a digital solution for secondary prevention of stroke. They also noted the need for a mobile app that is easy to use. Clinician feedback highlighted the need for a customizable clinician portal that captures individual consumer goals.

CONCLUSIONS

Following an iterative co-design process, supported by evidence from user needs surveys and user experience workshops, a consumer-facing app that integrates wearable activity trackers and a clinician web portal were designed and developed to support secondary prevention of stroke. Feasibility testing is currently in progress to assess acceptability and use.

An Integrated Perspective of Effort and Perception of Effort

Effort and the perception of effort (PE) have been extensively studied across disciplines, resulting in multiple definitions. These inconsistencies block scientific progress by impeding effective communication between and within fields. Here, we present an integrated perspective of effort and PE that is applicable to both physical and cognitive activities. We define effort as the energy utilized to perform an action. This definition can be applied to biological entities performing various voluntary or involuntary activities, irrespective of whether the effort contributes to goal achievement. Then, we define PE as the instantaneous experience of utilizing energy to perform an action. This definition builds on that of effort without conflating it with other subjective experiences. We explore the nature of effort and PE as constructs and variables and highlight key considerations in their measurement. Our integrated perspective aims to facilitate a deeper understanding of these constructs, refine research methodologies, and promote interdisciplinary collaborations.

Effects of acute simulated altitude on the maximal lactate steady state in humans

We sought to determine the effects of acute simulated altitude on the maximal lactate steady state (MLSS) and physiological responses to cycling at and 10 W above the MLSS-associated power output (PO) (MLSSp and MLSSp+10, respectively). Eleven (4 females) participants (means [SD]; 28 [4] yr; V̇o2max: 54.3 [6.9] mL·kg-1·min-1) acclimatized to ∼1,100 m performed 30-min constant PO trials in simulated altitudes of 0 m sea level (SL), 1,111 m mild altitude (MILD), and 2,222 m moderate altitude (MOD). MLSSp, defined as the highest PO with stable (<1 mM change) blood lactate concentration ([BLa]) between 10 and 30 min, was significantly lower in MOD (209 [54] W) compared with SL (230 [56] W; P < 0.001) and MILD (225 [58] W; P = 0.001), but MILD and SL were not different (P = 0.12). V̇o2 and V̇co2 decreased at higher simulated altitudes due to lower POs (P < 0.05), but other end-exercise physiological responses (e.g., [BLa], ventilation [V̇e], heart rate [HR]) were not different between conditions at MLSSp or MLSSp + 10 (P > 0.05). At the same absolute intensity (MLSSp for MILD), [BLa], HR, and V̇E and all perceptual variables were exacerbated in MOD compared with SL and MILD (P < 0.05). Maximum voluntary contraction, voluntary activation, and potentiated twitch forces were exacerbated at MLSSp + 10 relative to MLSSp within conditions (P < 0.05); however, condition did not affect performance fatiguability at the same relative or absolute intensity (P > 0.05). As MLSSp decreased in hypoxia, adjustments in PO are needed to ensure the same relative intensity across altitudes, but common indices of exercise intensity may facilitate exercise prescription and monitoring in hypoxia.NEW & NOTEWORTHY This study demonstrates the power output and metabolic rate associated with the maximal lactate steady-state (MLSS) decline in response to simulated altitude; however, common indices of exercise intensity remained unchanged when cycling was performed at the work rate associated with MLSS at each simulated altitude. These results support previous studies that investigated the effects of hypoxia on alternative measures of the critical intensity of exercise and will inform exercise prescription/monitoring across altitudes.

Fatigue and Performance Rates as Decision-Making Criteria in Pacing Control During CrossFit®

We investigated fatigue and performance rates as decision-making criteria in pacing control during CrossFit®. Thirteen male regional-level competitors completed conditions of all-out (maximum physical work from beginning to end) and controlled-split (controlled physical work in the first two rounds but maximum work in the third round) pacing throughout the Fight Gone Bad workout separated by one week. We assessed benchmarks, countermovement jumps and ratings of fatigue after each round. Benchmarks were lower in round 1 (99 vs. 114, p < .001) but higher in rounds 2 (98 vs. 80, p < .001) and 3 (97 vs. 80, p < .001) for controlled-split compared with all-out pacing. Reductions in countermovement jumps were higher after rounds 1 (-12.6% vs. 1.6%, p < .001) and 2 (-12.7% vs. -4.0%, p = .014) but similar after round 3 (-13.2% vs. -11.3%, p = .571) for all-out compared with controlled-split pacing. Ratings of fatigue were higher after rounds 1 (7 vs. 5 a.u., p < .001) and 2 (8 vs. 7 a.u, p = .023) but similar after round 3 (9 vs. 9 a.u., p = .737) for all-out compared with controlled-split pacing. During all-out pacing, countermovement jump reductions after round 2 correlated with benchmark drops across rounds 1 and 2 (r = .78, p = .002) and rounds 1 and 3 (r = -.77, p = .002) and with benchmark workout changes between pacing strategies (r = -.58, p = .036), suggesting that the larger the countermovement jump reductions the higher the benchmark drops across rounds and workouts. Therefore, benchmarks, countermovement jumps and ratings of fatigue may assess exercise-induced fatigue as decision-making criteria to improve pacing strategy during workouts performed for as many repetitions as possible.

First-Generation OTC Antihistamine Use and Voice Function in Individuals with Allergic Rhinitis: A Preliminary Report of Clinically Impactful Findings

PURPOSE

The primary goal of this investigation was to characterize the effect of the first-generation, over-the-counter antihistamine Chlor-Trimeton on laryngeal structure and function in a previously unstudied population - individuals diagnosed with allergic rhinitis who routinely take over-the-counter antihistamines and deny the experience or diagnosis of voice disorder.

STUDY DESIGN

Prospective within-participant multimodality repeated measures design.

METHODS

Eight consented participants (seven females, one male) previously diagnosed with allergic rhinitis and without history of voice disorder who routinely took over-the-counter antihistamines completed the study. Volunteers completed the following measures before and 2hours after antihistamine administration: perceptual vocal function measures, phonation threshold pressure (PTP), acoustic measures, and laryngeal imaging. All pre- and post-administration data were descriptively analyzed for clinically significant change.

RESULTS

No clinically significant differences were identified for any acoustic or aerodynamic measures taken. Analyses of laryngeal imaging data indicated that all participants had evidence of mucosal changes in one or more of the following parameters: increased vascularity, mucus in the anterior commissure, and vocal fold color changes, all of which are consistent with prior descriptions of allergy larynx.

CONCLUSIONS

Empirical study of laryngeal appearance in individuals diagnosed with allergic rhinitis, affirmed clinical observations of laryngeal tissue changes consistent with allergy larynx. Stable PTP suggests potential vocal fold cover adaptations from routine use of over-the-counter antihistamines that may buffer the typical desiccating effect on voice function observed in prior studies of healthy individuals.

Association between Mid-Term Functionality and Clinical Severity in Patients Hospitalized for Pulmonary Embolism

The aim of this study is to evaluate the relationship between clinical severity and functionality, occupational performance, and health-related quality of life in patients hospitalized with pulmonary embolism. Pulmonary embolism patients were grouped by clinical severity using the Pulmonary Embolism Severity Index. Those scoring ≥160 were in the high-severity group (HSG); those scoring < 160 in the low-moderate group (LMSG). The main variables were functionality assessed by the World Health Organization Disability Assessment Schedule (WHODAS), self-perception of occupational performance assessed by the Canadian Occupational Performance Measure (COPM), pain and fatigue assessed by a Visual Analogue Scale (VAS), and health-related quality of life assessed by the EuroQol-5Dimensions (EQ-5D). Patients were evaluated at hospital admission and at 1-month and 3-month follow-up. At admission, there were significant differences between groups in the WHODAS and health-related quality of life in favor of the LMSG. At 1-month and at 3-month follow-up, there were significant differences between the LMSG and HSG in WHODAS, COMP, NRS pain, fatigue and EQ-5D scores in favor of the LMSG. An association exists between clinical severity and mid-term functionality, self-perception of occupational performance, pain, fatigue, and health-related quality of life in PE patients.

The Autoregulation Rest-Redistribution Training Method Mitigates Sex Differences in Neuromuscular and Perceived Fatigue During Resistance Training

PURPOSE

To examine the sex differences in performance and perceived fatigue during resistance training prescribed using traditional (TRA) and autoregulation rest-redistribution training (ARRT) approaches.

METHODS

Twelve resistance-trained men and 12 women completed 2 sessions including the bench-press exercise matched for load (75% of 1-repetition maximum), volume (24 repetitions), and total rest (240 s). Sessions were performed in a counterbalanced randomized design with TRA consisting of 3 sets of 8 repetitions with 120-second interset rest and ARRT employing a personalized combination of clusters, repetitions per cluster, and between-clusters rest regulated with a 20% velocity-loss threshold. The effects of TRA and ARRT on velocity loss, unilateral isometric peak force, and rating of fatigue (ROF) were compared between sexes.

RESULTS

The velocity loss was generally lower during ARRT compared with TRA (-0.47% [0.11%]), with velocity loss being mitigated by ARRT to a greater extent among males compared with females (-0.37% [0.15%]). A smaller unilateral isometric peak force decline was observed after ARRT than TRA among males compared with females (-38.4 [8.4] N). Lower ROF after ARRT than TRA was found among males compared to females (-1.97 [0.55] AU). Additionally, males reported greater ROF than females across both conditions (1.92 [0.53] AU), and ARRT resulted in lower ROF than TRA overall (-0.83 [0.39] AU).

CONCLUSIONS

The ARRT approach resulted in decreased velocity loss, peak force impairment, and ROF compared with TRA in both sexes. However, male subjects exhibited more pronounced acute within-session benefits from the ARRT method.

Exploring sex differences in blood-based biomarkers following exhaustive exercise using bioinformatics analysis

This study examined the acute effects of exercise testing on immunology markers, established blood-based biomarkers, and questionnaires in endurance athletes, with a focus on biological sex differences. Twenty-four healthy endurance-trained participants (16 men, age: 29.2± 7.6 years, maximal oxygen uptake (V ˙ O 2 max ): 59.4 ± 7.5 ml · min-1 · kg-1; 8 women, age: 26.8 ± 6.1 years,V ˙ O 2 max : 52.9 ± 3.1 ml · min-1 · kg-1) completed an incremental submaximal exercise test and a ramp test. The study employed exploratory bioinformatics analysis: mixed ANOVA, k-means clustering, and uniform manifold approximation and projection, to assess the effects of exhaustive exercise on biomarkers and questionnaires. Significant increases in biomarkers (lymphocytes, platelets, procalcitonin, hemoglobin, hematocrit, red blood cells, cell-free DNA (cfDNA)) and fatigue were observed post-exercise. Furthermore, differences pre- to post-exercise were observed in cytokines, cfDNA, and other blood biomarkers between male and female participants. Three distinct groups of athletes with differing proportions of females (Cluster 1: 100% female, Cluster 2: 85% male, Cluster 3: 37.5% female and 65.5% male) were identified with k-means clustering. Specific biomarkers (e.g., interleukin-2 (IL-2), IL-10, and IL-13, as well as cfDNA) served as primary markers for each cluster, potentially informing individualized exercise responses. In conclusion, our study identified exercise-sensitive biomarkers and provides valuable insights into the relationships between biological sex and biomarker responses.

The effects of affect-guided interval training on pleasure, enjoyment, and autonomy: A registered report

This registered report tested the effects of a novel exercise protocol, namely affect-guided interval training, on motivationally relevant variables of remembered pleasure, forecasted pleasure, enjoyment, and autonomy. Affect-guided interval training (AIT) consisted of 60-s intervals that alternated between the highest pleasant intensity and lowest pleasant intensity for 20 min; this was intended to minimize the potential displeasure of traditional high-intensity interval training. The novel protocol was compared to self-selected exercise intensity (30 min) and high-intensity interval training (60-s intervals for 20 min). All sessions were, on average, vigorous in intensity (80-89% peak heart rate). Data indicate that the AIT session was experienced as the most pleasant, had the most pleasant slope of affect, was remembered as the most pleasant, resulted in the most positive affective forecasts, and was the most enjoyable. Both the affect-guided interval session and self-selected exercise session resulted in greater autonomy than high-intensity interval training. Several evaluative and motivationally relevant variables, including (a) remembered pleasure, (b) enjoyment, and (c) forecasted pleasure were predicted by (a) experienced pleasure, the (b) pleasure experienced at the end of exercise, and (c) the slope of pleasure experienced throughout the exercise session. Overall, this study suggests that affect-guided interval training is a feasible and positive alternative that can be included as a viable option for exercise programming.

Influence of voluntary isocapnic hyperpnoea on recovery after high-intensity exercise in elite short-track speedskaters - randomized controlled trial

Respiratory muscle training plays a significant role in reducing blood lactate concentration (bLa) and attenuating negative physiological stress reactions. Therefore, we investigated if voluntary isocapnic hyperpnoea (VIH) performed after a maximum anaerobic effort influences bLa and perceived fatigue level in well-trained speedskaters. 39 elite short-track speedskaters participated in a trial with two parallel groups: experimental and control. All the participants performed the Wingate Anaerobic Test (WAnT). The experimental group performed a VIH-based recovery protocol 20 min after exercise, the control group used passive recovery only. Blood samples were taken 3 and 30 min after the WAnT to measure bLa. Fatigue was self-appraised on a 0-10 perceived rating-of-fatigue (ROF) scale 3 and 30 min after the WAnT. Noteworthy, but not statistically significant changes between the experimental and control groups were observed for changes in bLa (p = 0.101). However, statistically significant changes between the groups were found for ROF (p = 0.003, ηp2 = 0.211, ω2 = 0.106). Moreover, statistically significant interactions between post-exercise bLa clearance and VO2max (p = 0.028) and inspiratory muscle strength (p = 0.040) were observed. Our findings provided preliminary insight that VIH may be an efficient recovery protocol after anaerobic exercise performed by elite athletes. The association between VO2max and post-exercise bLa clearance indicates the vital role of aerobic fitness in repeated-efforts ability in short-track speedskaters. The study was registered at ClinicalTrials.gov as NCT05994092 on 15th August 2023.

Oxygen therapy for exercise capacity in fibrotic interstitial lung disease: A systematic review and meta-analysis of randomised controlled trials

BACKGROUND

Fibrotic interstitial lung disease (fILD) is characterised primarily by impaired lung function and quality of life. The present study investigated whether oxygen therapy could improve exercise capacity among patients with fILD.

METHODS

Previously published randomised controlled trials (RCTs) were surveyed. A systematic review and meta-analysis was conducted to evaluate the effectiveness of oxygen therapy in improving the exertional capacity of patients with fILD. The primary outcome was peripheral oxygen saturation (SpO2) during exercise. The effects of oxygen therapy on fatigue, dyspnoea, heart rate, and exercise duration or distance were also analysed.

RESULTS

Fourteen RCTs involving 370 patients were included. Oxygen therapy improved SpO2 during exercise (mean difference, MD = 6.26 %), exercise duration (MD = 122.15 s), fatigue (standard mean difference, SMD = -0.30), and dyspnoea (MD = -0.75 Borg score units). High-flow oxygen systems tended to be more effective than low-flow systems in improving exercising SpO2, duration, fatigue, dyspnoea, and heart rate. High-flow nasal cannulas (HFNCs) yielded better outcomes regarding SpO2 and fatigue than did high-flow Venturi masks (MD = 1.60 % and MD = -1.19 Borg score units, respectively). No major adverse events were reported.

CONCLUSION

The evidence from RCTs supports the short-term use of oxygen supplementation to improve SpO2, exercise capacity, fatigue, and dyspnoea among patients with fILD. Further analyses demonstrates that HFNCs yield more favourable outcomes, yet not reaching statistical significance except for improving SpO2 and fatigue. However, the long-term effects of oxygen therapy on quality of life and mortality remain unclear.

Performance and perceived fatigability across the intensity spectrum: role of muscle mass during cycling

The role of muscle mass in modulating performance and perceived fatigability across the entire intensity spectrum during cycling remains unexplored. We hypothesized that at task failure (Tlim), muscle contractile function would decline more following single- (SL) versus double-leg (DL) cycling within severe and extreme intensities, but not moderate and heavy intensities. After DL and SL ramp-incremental tests, on separate days, 11 recreationally active males (V̇o2max: 49.5 ± 7.7 mL·kg-1·min-1) completed SL and DL cycling until Tlim within each intensity domain. Power output for SL trials was set at 60% of the corresponding DL trial. Before and immediately after Tlim, participants performed an isometric maximal voluntary contraction (MVC) coupled with one superimposed and three resting femoral nerve stimulations [100 Hz; 10 Hz; single twitch (Qtw)] to measure performance fatigability. Perceived fatigue, leg pain, dyspnea, and effort were collected during trials. Tlim within each intensity domain was not different between SL and DL (all P > 0.05). MVC declined more for SL versus DL following heavy- (-42 ± 16% vs. -30 ± 18%; P = 0.011) and severe-intensity cycling (-41 ± 12% vs. -31 ± 15%; P = 0.036). Similarly, peak Qtw force declined more for SL following heavy- (-31 ± 12% vs. -22 ± 10%; P = 0.007) and severe-intensity cycling (-49 ± 13% vs. -40 ± 7%; P = 0.048). Except for heavy intensity, voluntary activation reductions were similar between modes. Similarly, except for dyspnea, which was lower for SL versus DL across all domains, ratings of fatigue, pain, and effort were similar at Tlim between exercise modes. Thus, the amount of muscle mass modulates the extent of contractile function impairment in an intensity-dependent manner.NEW & NOTEWORTHY We investigated the modulatory role of muscle mass on performance and perceived fatigability across the entire intensity spectrum. Despite similar time-to-task failure, single-leg cycling resulted in greater impairments in muscle contractile function within the heavy- and severe-intensity domains, but not the moderate- and extreme-intensity domains. Perceived fatigue, pain, and effort were similar between cycling modes. This indicates that the modulatory role of muscle mass on the extent of performance fatigability is intensity domain-dependent.

Influence of running on incidental and integral vitality and fatigue: An intensive longitudinal intervention in young Women's daily life

Exercise intensity and perceived autonomy are important factors for the affective response toward exercise and adherence. Dual-mode theory suggests an inverted-J response curve of affect with increased exercise intensity, but little is known about how different running programs affect the affective response and subsequent incidental affect in daily life. This ambulatory assessment study examines the short- to long-term effects of two 8-week running interventions (affect-based vs. polarized-prescribed) on subjective vitality and perceived fatigue in young female novices. Participants engaged in 3 × 30 minute running sessions weekly in their natural environments and completed electronic diaries three times daily. Autoregressive multilevel models indicate small effects of training intensity on immediate affective subjective vitality (ß = -2.37; p = .03; f2 = 0.02) but negligible non-significant effects on fatigue (ß = 0.26; p = 0.12; f2 = 0.002). Novices experienced increased vitality throughout the day when their running was evaluated positively (ß = 0.23; p = .03; f2 = 0.04), with effects lasting over two days before returning to baseline (ß = -0.26; p < .001; f2 = 0.004). However, no significant long-term effects were observed over 8 weeks in vitality or fatigue. Results indicate between- and within-person variations, but limited sample power does not allow differentiating between programs. This study supports the dual-mode theory and highlights the importance of distinguishing affective response from incidental affect.

Acute anodal transcranial direct current stimulation improves the performance of professional rowers

Introduction

The aim of the present study was to evaluate the influence of acute transcranial direct current stimulation (tDCS) on physical and subjective responses in professional rowing during the 2,000-m time trial test.

Methods

Seven rowers (age 20.86 ± 4.49 years; weight 71.66 ± 7.97 kg) participated in this randomized triple-blind trial with a crossover experimental design. The protocol consists of 2 days with different conditions (anodal and sham). The tDCS anodic stimulation conducted was 2 mA for 20 min in the left temporal cortex (2.5 cm from the F7 zone and 2.5 cm from the T3 zone), targeting the left insular cortex. In the sham moment, the participants experienced 30 s of stimulation. Afterward, they performed a standardized progressive warm-up for 15 min, following the Brazilian Rowing Confederation's assessment protocols, and rested for 3 min before the test started. All procedures were made on an indoor rowing machine, which allowed the capture of performance variables such as time performed, power in watts (W), pace (m/min), and stroke rate (strokes/min). The ratings of perceived exertion [Borg scale (CR-20)] were recorded in each 2-min during the test.

Results

The results presented differences in power [Z: -2.371; p = 0.018; effect size (ES) = -0.896 (large)] and pace [Z: -2.371; p = 0.018; ES = -0.896 (large)] and time performance [Z: -1.612; p = 0.107; ES = -0.609 (large)] throughout the protocol for the anodal moment.

Discussion

However, no differences for the other variables were found. According to the results, the current tDCS with the present protocol improved the physical performance at the 2,000-m time trial Test providing ergogenic aid.

Validation of the Borg CR10 Scale for the evaluation of shoulder perceived fatigue during work-related tasks

Work-related upper extremity disorders (WRUEDs) are highly prevalent and costly. Development of fatigue is thought to be one of the causes of WRUEDs. Perceived fatigue can be assessed with the Borg CR Scale® (Borg CR10). The objective was to validate the Borg CR10 for the evaluation of shoulder perceived fatigue during lifting tasks. Seventy adults in working age performed three rhythmic lifting tasks with two loads (15% and 30% of maximal voluntary contraction). Using generalized repeated-measures ANOVA (Generalized Estimating Equations), statistically significant Task and Load effects (p < 0.001), as well as Task × Load interaction effects (p < 0.0001) were observed on Borg CR10, without any influence of sex. The Borg CR10 is a valid tool to assess shoulder perceived fatigue as it can discriminate between tasks of different difficulty levels in term of complexity, height, and resistance, regardless of sex.

Effects of carbohydrate availability on cycling endurance at the maximal lactate steady state

The impacts of carbohydrate (CHO) availability on time to task failure (TTF) and physiological responses to exercise at the maximal lactate steady state (MLSS) have not been studied. Ten participants (3 females, 7 males) completed this double-blinded, placebo-controlled study that involved a ramp incremental test, MLSS determination, and four TTF trials at MLSS, all performed on a cycle ergometer. With the use of a combination of nutritional (CHO, 7 g/kg, and placebo, PLA, 0 g/kg drinks) and exercise interventions [no exercise (REST) and glycogen-reducing exercise (EX)], the four conditions were expected to differ in preexercise CHO availability (RESTCHO > RESTPLA > EXCHO > EXPLA). TTF at MLSS was not improved by CHO loading, as RESTCHO (57.1 [16.6] min) and RESTPLA (57.1 [15.6] min) were not different (P = 1.00); however, TTF was ∼50% shorter in EX conditions compared with REST conditions on average (P < 0.05), with EXCHO (39.1 [9.2] min) ∼90% longer than EXPLA (20.6 [6.9] min; P < 0.001). There were effects of condition for all perceptual and cardiometabolic variables when compared at isotime (P < 0.05) and task failure (TF; P < 0.05), except for ventilation, perceptual responses, and neuromuscular function measures, which were not different at TF (P > 0.05). Blood lactate concentration was stable in all conditions for participants who completed 30 min of exercise. These findings indicate that TTF at MLSS is not enhanced by preexercise CHO supplementation, but recent intense exercise decreases TTF at MLSS even with CHO supplementation. Extreme fluctuations in diet and strenuous exercise that reduce CHO availability should be avoided before MLSS determination.NEW & NOTEWORTHY Carbohydrate (CHO) loading did not increase participants' ability to cycle at their maximal lactate steady state (MLSS); however, performing a glycogen depletion task the evening before cycling at MLSS reduced the time to task failure, even when paired with a high dose of CHO. These diet and exercise interventions influenced blood lactate concentration ([BLa]) but not the stability of [BLa]. Activities that reduce CHO availability should be avoided before MLSS determination.

Immediate crossover fatigue after unilateral submaximal eccentric contractions of the knee flexors involves peripheral alterations and increased global perceived fatigue

After a unilateral muscle exercise, the performance of the non-exercised contralateral limb muscle can be also impaired. This crossover fatigue phenomenon is still debated in the literature and very few studies have investigated the influence of eccentric contractions. This study was designed to assess neuromuscular adaptations involved in the crossover fatigue of the non-exercised contralateral knee flexor muscles. Seventeen healthy young men performed a unilateral submaximal eccentric exercise of the right knee flexors until a 20% reduction in maximal voluntary isometric contraction torque was attained in the exercised limb. Before (PRE), immediately after exercise cessation (POST) and 24 hours later (POST24), neuromuscular function and perceived muscle soreness were measured in both the exercised limb and non-exercised limb. In addition, global perceived fatigue was assessed at each measurement time. At POST, significant reductions in maximal voluntary isometric contraction were observed in the exercised limb (-28.1%, p < 0.001) and in the non-exercised limb (-8.5%, p < 0.05), evidencing crossover fatigue. At POST, voluntary activation decreased in the exercised limb only (-6.0%, p < 0.001), while electrically evoked potentiated doublet torque was impaired in both the exercised limb and the non-exercised limb (-11.6%, p = 0.001). In addition, global perceived fatigue significantly increased at POST (p < 0.001). At POST24, all measured variables returned to PRE values, except for perceived muscle soreness scores exhibiting greater values than PRE (p < 0.05). A possible cumulative interaction between peripheral alterations and global perceived fatigue may account for the immediate crossover fatigue observed in the non-exercised limb.

Effects of Acute Physical Fatigue on Gaze Behavior in Expert Badminton Players

Perceptual cognitive skills in real game settings, under conditions of fatigue, such as the ability to gather relevant visual information, are key factors in achieving motor goals in sports. The objectives were to evaluate the effects of acute physical fatigue on gaze behavior during a badminton game (Study 1) and in an unfavorable force ratio situation (Study 2). Six international-level badminton players played two sets and unfavorable force ratio situations while wearing eye-tracking glasses before and after a fatiguing task. During the set, fatiguing physical exercise led to fewer fixations per exchange and more fixations on one area of interest. During unfavorable force ratio situations, fatiguing physical exercise led to shorter fixation durations per exchange, shorter fixation durations on two areas of interest, and longer fixation durations on one area of interest. The results showed that gaze behaviors were adapted in acute physical fatigue conditions to maintain performance.

Thoracic-Worn Accelerometers Detect Fatigue-Related Changes in Vertical Stiffness During Sprinting

ABSTRACT

Horsley, BJ, Tofari, PJ, Halson, SL, Kemp, JG, Johnston, RD, and Cormack, SJ. Thoracic-worn accelerometers detect fatigue-related changes in vertical stiffness during sprinting. J Strength Cond Res 38(2): 283-289, 2024-Thoracic-mounted accelerometers are valid and reliable for analyzing gait characteristics and may provide the opportunity to assess running-related neuromuscular fatigue (NMF) during training and competition without the need for additional tests, such as a countermovement jump (CMJ). However, their sensitivity for detecting fatigue-related changes in gait across different speeds is unclear. We, therefore, assessed the changes in accelerometer-derived gait characteristics, including vertical stiffness (K vert ), following a repeated sprint protocol (RSP). Sixteen recreationally active subjects performed single and repeated CMJs on a force plate and 40 m run throughs overground at 3-4, 5-6, and 7-8 m·s -1 pre-post a 12 × 40 m RSP. Gait characteristics (contact time, step frequency, step length, K vert , etc.) were derived from an accelerometer contained within a global navigation satellite system unit on the thoracic spine using a validated algorithm. Changes in running gait and CMJ performance were assessed using a linear mixed-effects model (95% confidence interval [95% CI]; effect size [ES]). Significance was set at p < 0.05. A significant reduction in K vert occurred at 7-8 m·s -1 following the RSP (-8.51 kN·m -1 [-13.9, -3.11]; p = 0.007; ES [95% CI] = -0.39 [-0.62, -0.15]) which coincided with a decreased jump height (-0.03 m [-0.04, -0.01]; p = 0.002; ES [95% CI] = -0.87 [-1.41, -0.30]). However, all other gait characteristics were not significantly different irrespective of speed. Thoracic-worn accelerometers can detect changes in K vert at 7-8 m·s -1 which may be useful for monitoring NMF during sprinting. However, a RSP does not result in altered gait mechanics in subsequent running at lower speeds.

Effect of sportswear on performance and physiological heat strain during prolonged running in moderately hot conditions

INTRODUCTION

This study examined the impact of different upper-torso sportswear technologies on the performance and physiological heat strain of well-trained and national-level athletes during prolonged running in moderately hot conditions.

METHODS

A randomized crossover design was employed in which 20 well-trained (n = 16) and national-level (n = 4) athletes completed four experimental trials in moderately hot conditions (35°C, 30% relative humidity). In each trial, participants ran at 70% of their peak oxygen uptake (70% V̇O2peak ) for 60 min, while wearing a different upper-body garment: cotton t-shirt, t-shirt with sweat-wicking fabric, compression t-shirt, and t-shirt with aluminum dots lining the inside of the upper back of the garment. Running speed was adjusted to elicit the predetermined oxygen consumption associated with 70% V̇O2peak . Physiological (core and skin temperatures, total body water loss, and urine specific gravity) and perceptual (thermal comfort and sensation, ratings of perceived exertion, and garment cooling functionality) parameters along with running speed at 70% V̇O2peak were continuously recorded.

RESULTS

No significant differences were observed between the four garments for running speed at 70% V̇O2peak , physiological heat strain, and perceptual responses (all p > 0.05). The tested athletes reported larger areas of perceived suboptimal cooling functionality in the cotton t-shirt and the t-shirt with aluminum dots relative to the sweat-wicking and compression t-shirts (d: 0.43-0.52).

CONCLUSION

There were not differences among the tested garments regarding running speed at 70% V̇O2peak , physiological heat strain, and perceptual responses in well-trained and national-level endurance athletes exercising in moderate heat.

Thermoregulatory and perceptual implications of varying torso soft armour coverage during treadmill walking in dry heat

Modular armour allows soldiers to adjust the level of coverage according to the threat level. We hypothesized that armour configurations with lower levels of torso soft armour coverage attenuate physiological and perceptual responses during exercise in the heat. Fifteen adults (5 females/10 males, 26 ± 5 years) walked (5 km/h, 1% incline, 1h) in dry heat (38 °C, 20% humidity) while wearing body armour that provided; i) high coverage (HC: 0.57 ± 0.09 m2, 18.5 ± 0.3 kg), ii) moderate coverage (MC: 0.44 ± 0.07 m2, 18.1 ± 0.3 kg), iii) low coverage (LC1: 0.21 ± 0.03 m2, 17.4 ± 0.1 kg), or iv) low coverage with weight equalization (LC2: 0.21 ± 0.03 m2, 18.6 ± 0.2 kg). Core temperature (Tcore), heart rate (HR), metabolic heat production (M-W), whole-body sweat rate (WBSR), and perceptual responses were measured. M-W during exercise (629 ± 126 W) did not differ between configurations (p = 0.30). The change in Tcore (HC: 0.88 ± 0.37 °C, MC: 0.85 ± 0.32 °C, LC1: 0.91 ± 0.38 °C, LC2: 0.89 ± 0.42 °C, p = 0.93), HR (HC: 97 ± 14 bpm, MC: 103 ± 16 bpm, LC1: 96 ± 15 bpm, LC2: 97 ± 20 bpm, p = 0.08), and WBSR (HC: 10.2 ± 3.4 g/min, MC: 10.3 ± 4.3 g/min, LC1: 9.9 ± 4.7 g/min, LC2: 10.4 ± 4.5 g/min, p = 0.84) did not differ between configurations. Perceptual responses did not differ between configurations (all p ≥ 0.15). Reducing torso soft armour coverage, with minimal reductions in armour load, does not reduce physiological or perceptual strain during walking in dry heat.

The effect of transcutaneous auricular vagus nerve stimulation on cycling ergometry and recovery in healthy young individuals

BACKGROUND

It is aimed to examine the potential benefits and effects of the use of transcutaneous auricular vagus nerve stimulation (VNS) for sporting purposes on recovery, fatigue, and sportive performance level.

METHODS

In this study, 90 people between the ages of 18-23 were participated. They were randomly divided into three groups as bilateral sham, unilateral left, and bilateral VNS. A 4-day protocol was applied to the participants. Cycling exercise was performed with maximum performance for 30 min under the same watt load. Pulse, systolic and diastolic blood pressure, distance, pain, fatigue, lactic acid level, and autonomic nervous system were evaluated.

RESULTS

Within the groups, there was a statistically significant difference between the data (p < .05) except for the distance covered parameter. When we compare the groups, in addition to the distance traveled in all groups, there is no statistically significant difference in the 1st day 1st measurement and 2nd measurement data of all parameters (p > .05 When we compared the data according to days, there was a statistically significant difference between bilateral stimulation (BS) and unilateral stimulation, only pain and fatigue levels (p < .05).

CONCLUSION

In our study, we saw that BS application gave positive results in reducing pain and fatigue due to cycling exercise compared to other applications. Similar results were obtained when we evaluated the data on a daily basis. We believe that VNS will be beneficial in reducing pain and fatigue, especially during and after the competition halftime.

The influence of skeletal muscle mitochondria and sex on critical torque and performance fatiguability in humans

Critical torque (CT) represents the highest oxidative steady state for intermittent knee extensor exercise, but the extent to which it is influenced by skeletal muscle mitochondria and sex is unclear. Vastus lateralis muscle biopsy samples were collected from 12 females and 12 males -matched for relative maximal oxygen uptake normalized to fat-free mass (FFM) (F: 57.3 (7.5) ml (kg FFM)-1  min-1 ; M: 56.8 (7.6) ml (kg FFM)-1  min-1 ; P = 0.856) - prior to CT determination and performance fatiguability trials. Males had a lower proportion of myosin heavy chain (MHC) I isoform (40.6 (18.4)%) compared to females (59.5 (18.9)%; P = 0.021), but MHC IIa and IIx isoform distributions and protein markers of mitochondrial content were not different between sexes (P > 0.05). When normalized to maximum voluntary contraction (MVC), the relative CT (F: 42.9 (8.3)%; M: 37.9 (9.0)%; P = 0.172) and curvature constant, W' (F: 26.6 (11.0) N m s (N m)-1 ; M: 26.4 (6.5) N m s (N m)-1 ; P = 0.962) were not significantly different between sexes. All protein biomarkers of skeletal muscle mitochondrial content, as well as the proportion of MHC I isoform, positively correlated with relative CT (0.48 < r < 0.70; P < 0.05), and the proportion of MHC IIx isoform correlated positively with relative W' (r = 0.57; P = 0.007). Indices of performance fatiguability were not different between males and females for MVC- and CT-controlled trials (P > 0.05). Greater mitochondrial protein abundance was associated with attenuated declines in potentiated twitch torque for exercise at 60% MVC (P < 0.05); however, the influence of mitochondrial protein abundance on performance fatiguability was reduced when exercise was prescribed relative to CT. Whether these findings translate to whole-body exercise requires additional research. KEY POINTS: The quadriceps critical torque represents the highest intensity of intermittent knee extensor exercise for which an oxidative steady state is attainable, but its relationship with skeletal muscle mitochondrial protein abundance is unknown. Matching males and females for maximal oxygen uptake relative to fat-free mass facilitates investigations of sex differences in exercise physiology, but studies that have compared critical torque and performance fatiguability during intermittent knee extensor exercise have not ensured equal aerobic fitness between sexes. Skeletal muscle mitochondrial protein abundance was correlated with critical torque and fatigue resistance for exercise prescribed relative to maximum voluntary contraction but not for exercise performed relative to the critical torque. Differences between sexes in critical torque, skeletal muscle mitochondrial protein abundance and performance fatiguability were not statistically significant. Our results suggest that skeletal muscle mitochondrial protein abundance may contribute to fatigue resistance by influencing the critical intensity of exercise.

Sodium Bicarbonate Ingestion in a Fasted State Improves 16.1-km Cycling Time-Trial Performance

PURPOSE

The use of sodium bicarbonate (SB) as a preexercise ergogenic aid has been extensively studied in short-duration high-intensity exercise. Very few studies have considered the effects of SB ingestion before prolonged high-intensity exercise. The aim of the present study was to determine the effects of a 0.3 g·kg -1 body mass dose of SB ingested before the start of a 16.1-km cycling time trial in cyclists.

METHOD

Ten trained male cyclists (age, 31.1 ± 9 yr; height, 1.84 ± 0.05 m; body mass, 82.8 ± 8.5 kg; and V̇O 2peak , 60.4 ± 3.1 mL·kg -1 ·min -1 ) completed this study. Participants ingested 0.3 g·kg -1 in gelatine (SB-G) and enteric capsules (SB-E) 1 wk apart to determine individualized time-to-peak alkalosis for each ingestion form. Using a randomized crossover design, participants then performed simulated 16.1-km time trials after ingestion of SB-G, SB-E, or a placebo.

RESULTS

There were significant differences in performance between the SB and placebo ingestion strategies ( f = 5.50, P = 0.014, p η2 = 0.38). Performance time was significantly improved by SB ingestion (mean improvement: 34.4 ± 42.6 s ( P = 0.031) and 40.4 ± 45.5 s ( P = 0.020) for SB-G and SB-E, respectively) compared with the placebo. Gastrointestinal symptoms were lower after SB-E compared with SB-G (36.3 ± 4.5 vs 5.6 ± 3.1 AU, P < 0.001, g = 7.09).

CONCLUSIONS

This study demonstrates that increased buffering capacity after acute preexercise SB ingestion can improve endurance cycling time-trial performances. The use of SB could be considered for use in 16.1-km cycling time trials, but further work is required to establish these effects after a preexercise meal.

Development and validation of the pandemic fatigue scale

The existence and nature of pandemic fatigue-defined as a gradually emerging subjective state of weariness and exhaustion from, and a general demotivation towards, following recommended health-protective behaviors, including keeping oneself informed during a pandemic-has been debated. Herein, we introduce the Pandemic Fatigue Scale and show how pandemic fatigue evolved during the COVID-19 pandemic, using data from one panel survey and two repeated cross-sectional surveys in Denmark and Germany (overall N = 34,582). We map the correlates of pandemic fatigue and show that pandemic fatigue is negatively related to people's self-reported adherence to recommended health-protective behaviors. Manipulating the (de)motivational aspect of pandemic fatigue in a preregistered online experiment (N = 1584), we further show that pandemic fatigue negatively affects people's intention to adhere to recommended health-protective behaviors. Combined, these findings provide evidence not only for the existence of pandemic fatigue, but also its psychological and behavioral associations.

Effects of different cluster-set rest intervals during plyometric-jump training on measures of physical fitness: A randomized trial

The optimal intra-set rest for cluster sets (CLS) during plyometric-jump training (PJT) to improve physical fitness remains unclear. The objective of this quasi-experimental study was to compare the effects of PJT with traditional (TRS) vs. CLS structures, using different intra-set rests, on the physical fitness of healthy participants. Forty-seven recreationally active young men performed 3-5 sets of 10-12 repetitions of upper- and lower-body PJT exercises twice a week for six weeks using different set configurations: TRS group (no intra-set rest), and the CLS10, CLS20 and CLS30 groups with 10, 20 and 30 s of intra-set rest, respectively, while the total rest period was equated. Pretest-posttest measurements were carried out 48 h before and after the intervention and the rating of fatigue (ROF) was also assessed using a numerical scale (0-10 points) 20 min after the first and last (i.e., 12th) session. There was no significant difference in the mean energy intake between groups (p > 0.05). The repeated measures ANOVA revealed that all groups showed similar improvements (p < 0.05) in body mass, body mass index, fat-free mass, one repetition maximum (dynamic strength) and repetitions to failure (muscular endurance) in back squat and chest press, handgrip strength, standing long jump, 20 m sprint, 9-m shuttle run (change of direction speed), and ROF. Of note, the ROF was lower for the CLS20 and CLS30 groups, independent from the training effect. The physical fitness of recreationally active young men improved after 6 weeks of PJT involving intra-set rest intervals of 0 s, 10 s, 20 s, or 30 s. However, an intra-set rest of 20 s and 30 s seems to induce lower exercise-induced fatigue perception.

Beyond the Lungs: O 2 Supplementation Improves Cerebral Oxygenation and Fatigue during Exercise in Interstitial Lung Disease

PURPOSE

Cerebral hypoxia may exacerbate the perception of fatigue. We previously demonstrated that exercise-related hypoxemia, a hallmark of fibrotic interstitial lung disease ( f -ILD), dose dependently impairs cerebral oxygenation in these patients. It is unknown whether normalizing cerebral oxygenation with O 2 supplementation would be associated with positive changes in a relevant patient-centered outcome during exercise in f -ILD, such as improved perceived fatigue.

METHODS

Fourteen patients (12 males, 72 ± 8 yr, 8 with idiopathic pulmonary fibrosis, lung diffusing capacity for carbon monoxide = 44% ± 13% predicted) performed a constant-load (60% peak work rate) cycle test to symptom limitation (Tlim) breathing medical air. Fourteen controls cycled up to Tlim of an age- and sex-matched patient. Patients repeated the test on supplemental O 2 (fraction of inspired O 2 = 0.41 ± 0.08) for the same duration. Near-infrared spectroscopy and the rating-of-fatigue (ROF) scale assessed prefrontal cortex oxygenation and perceived fatigue, respectively.

RESULTS

Patients showed severe exertional hypoxemia (Tlim O 2 saturation by pulse oximetry = 80% ± 8%); they had poorer cerebral oxygenation (e.g., oxy-deoxyhemoglobin difference [HbDiff] = -3.5 ± 4.7 [range = -17.6 to +1.9] vs +1.9 ± 1.7 μmol from rest) and greater fatigue (ROF = 6.2 ± 2.0 vs 2.6 ± 2.3) versus controls under air ( P < 0.001). Reversal of exertional hypoxemia with supplemental O 2 led to improved HbDiff (+1.7 ± 2.4 μmol from rest; no longer differing from controls) and lower ROF scores (3.7 ± 1.2, P < 0.001 vs air) in patients. There was a significant correlation between O 2 -induced changes in HbDiff and ROF scores throughout exercise in f -ILD ( rrepeated-measures correlation = -0.51, P < 0.001).

CONCLUSIONS

Supplemental O 2 improved cerebral oxygenation during exercise in f -ILD, which was moderately associated with lower ratings of perceived fatigue. Reversing cerebral hypoxia with O 2 supplementation may thus have positive effects on patients' disablement beyond those expected from lower ventilation and dyspnea in this patient population.

Intermittent blood flow occlusion modulates neuromuscular, perceptual, and cardiorespiratory determinants of exercise tolerance during cycling

PURPOSE

Constant blood flow occlusion (BFO) superimposed on aerobic exercise can impair muscle function and exercise tolerance; however, no study has investigated the effect of intermittent BFO on the associated responses. Fourteen participants (n = 7 females) were recruited to compare neuromuscular, perceptual, and cardiorespiratory responses to shorter (5:15s, occlusion-to-release) and longer (10:30s) BFO applied during cycling to task failure.

METHODS

In randomized order, participants cycled to task failure (task failure 1) at 70% of peak power output with (i) shorter BFO, (ii) longer BFO, and (iii) no BFO (Control). Upon task failure in the BFO conditions, BFO was removed, and participants continued cycling until a second task failure (task failure 2). Maximum voluntary isometric knee contractions (MVC) and femoral nerve stimuli were performed along with perceptual measures at baseline, task failure 1, and task failure 2. Cardiorespiratory measures were recorded continuously across the exercises.

RESULTS

Task failure 1 was longer in Control than 5:15s and 10:30s (P < 0.001), with no differences between the BFO conditions. At task failure 1, 10:30s elicited a greater decline in twitch force compared to 5:15s and Control (P < 0.001). At task failure 2, twitch force remained lower in 10:30s than Control (P = 0.002). Low-frequency fatigue developed to a greater extent in 10:30s compared to Control and 5:15s (P < 0.047). Dyspnea and Fatigue were greater for Control than 5:15s and 10:30s at the end of task failure 1 (P < 0.002).

CONCLUSION

Exercise tolerance during BFO is primarily dictated by the decline in muscle contractility and accelerated development of effort and pain.

Tai Chi for the prophylaxis of episodic migraine: protocol of a non-inferiority randomized controlled trial with mechanism exploration

BACKGROUND

Migraine is a complex neurovascular disorder with considerable clinical, social and economic issues. Tai chi has the potential to be an alternative prophylactic treatment for migraine with high safety since the adverse effects and limited efficacy of available medications.

AIMS

The proposed study aims to compare the prophylaxis efficacy of 24-week Tai Chi training on migraine attacks with the standard prophylactic medication; and to explore the mechanism of Tai Chi in preventing migraine attacks by analyzing the associations between changes of migraine attacks and changes of neurovascular functions and inflammatory makers.

METHOD

This is a two-arm parallel non-inferiority randomized controlled trial. In total 220 Hong Kong Chinese women aged 18-65 years with diagnosis of episodic migraine will be recruited and randomized to either the Tai Chi training group or the standard prophylactic medication group with 1:1 ratio, and receive the 24 weeks of modified 33-short form Yang-style Tai Chi training and the standard prophylactic medications, respectively. A 24-week follow-up will be implemented for both groups. For efficacy examination, the primary outcome was the frequency of migraine attacks measured by the migraine diary; and for the mechanism exploration, the primary outcome was the volume and number of white matter hyperintensity (WMH) measured by magnetic resonance imaging (MRI). The measurements will be conducted at the baseline, 24th weeks, and 48th weeks. Linear mixed model will be adopted to comprehensively analyze the changes of variables within and between groups.

DISCUSSION

Given the importance of reducing disease burden and financial cost of migraine attacks, the findings of this study will provide new insights regarding the role of Tai Chi in alleviating migraine burden and further shed light on the mechanism action of Tai Chi on preventing headache attacks.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05690737. Registered on January 28, 2023.

Is foam rolling as effective as its popularity suggests? A randomised crossover study exploring post-match recovery in female basketball

This study aimed to assess the effectiveness of foam rolling as a post-match recovery tool in basketball. Using a crossover design, 13 female players completed two simulated matches, followed by foam rolling (FR) or placebo (CON). Countermovement jump height (CMJ), heart rate variability (Ln-rMSSD), muscle soreness (VAS), perceived recovery (TQR) and fatigue (Rating-of-Fatigue) were recorded at pre-match, post-match, post-recovery and 24 h post-match. No significant effect of time*intervention and intervention were found for any variable (p > 0.05), while a significant effect of time (p < 0.01) was reported for all variables. Post-hoc analyses revealed lower CMJ and Ln-rMSSD at post-match compared with all other time points (p < 0.001), increases in pre-match VAS scores at all subsequent time points (p < 0.01), and worse TQR and Rating-of-Fatigue scores from pre-to-post-match and pre-match-to-post-recovery (p < 0.01), except for unchanged TQR values from pre-match-to-post-recovery in FR (p > 0.05). Overall, the present data suggest that foam rolling was generally ineffective for improving post-exercise recovery in female basketball players after a single match. Future research investigating the effectiveness of foam rolling in players of different sex, age and/or competitive level is warranted to provide further insight on the topic.

Environmental heat stress offsets adaptation associated with carbohydrate periodization in trained male triathletes

PURPOSE

Carbohydrate (CHO) intake periodization via the sleep low train low (SL-TL) diet-exercise model increases fat oxidation during exercise and may enhance endurance-training adaptation and performance. Conversely, training under environmental heat stress increases CHO oxidation, but the potential of combined SL-TL and heat stress to enhance metabolic and performance outcomes is unknown.

METHODS

Twenty-three endurance-trained males were randomly assigned to either control (n = 7, CON), SL-TL (n = 8, SLTemp ) or SL-TL + heat stress (n = 8, SLHeat ) groups and prescribed identical 2-week cycling training interventions. CON and SLTemp completed all sessions at 20°C, but SLHeat at 35°C. All groups consumed matched CHO intake (6 g·kg-1 ·day-1 ) but timed differently to promote low CHO availability overnight and during morning exercise in both SL groups. Submaximal substrate utilization was assessed (at 20°C), and 30-min performance tests (at 20 and 35°C) were performed Pre-, Post-, and 1-week post-intervention (Post+1).

RESULTS

SLTemp improved fat oxidation rates at 60% MAP (~66% VO2peak ) at Post+1 compared with CON (p < 0.01). Compared with SLTemp , fat oxidation rates were significantly lower in SLHeat at Post (p = 0.02) and Post+1 (p < 0.05). Compared with CON, performance was improved at Post in SLTemp in temperate conditions. Performance was not different between any groups or time points in hot conditions.

CONCLUSION

SL-TL enhanced metabolic adaptation and performance compared with CON and combined SL-TL and heat stress. Additional environmental heat stress may impair positive adaptations associated with SL-TL.

Conflicts hurt: social stress predicts elevated pain and sadness after mild inflammatory increases

ABSTRACT

Individuals respond differently to inflammation. Pain, sadness, and fatigue are common correlates of inflammation among breast cancer survivors. Stress may predict response intensity. This study tested whether breast cancer survivors with greater exposure to acute or chronic social or nonsocial stress had larger increases in pain, sadness, and fatigue during an acute inflammatory response. In total, 156 postmenopausal breast cancer survivors (ages 36-78 years, stage I-IIIA, 1-9 years posttreatment) were randomized to either a typhoid vaccine/saline placebo or the placebo/vaccine sequence, which they received at 2 separate visits at least 1 month apart. Survivors had their blood drawn every 90 minutes for the next 8 hours postinjection to assess levels of interleukin-6 and interleukin-1 receptor antagonist (IL-1Ra). Shortly after each blood draw, they rated their current levels of pain, sadness, and fatigue. Women also completed the Test of Negative Social Exchange to assess chronic social stress and the Trier Inventory of Chronic Stressors screen to index chronic general stress. At each visit, a trained experimenter administered the Daily Inventory of Stressful Events to assess social and nonsocial stress exposure within the past 24 hours. After statistical adjustment for relevant demographic and behavioral covariates, the most consistent results were that survivors who reported more chronic social stress reported more pain and sadness in response to IL-1Ra increases. Frequent and ongoing social stress may sensitize the nervous system to the effects of inflammation, with potential implications for chronic pain and depression risk among breast cancer survivors.

The Effect of Extremely Low-Frequency Electromagnetic Fields on Inflammation and Performance-Related Indices in Trained Athletes: A Double-Blinded Crossover Study

Previous investigations have demonstrated the therapeutic advantages of extremely low-frequency electromagnetic fields (ELF-EMFs) in mitigating inflammation and influencing biological processes. We aimed to shed light on the effects of ELF-EMF on recovery rate following high-intensity exercise. Nine male athletes (26.7 ± 6.0 years; 69.6 ± 7.7 kg, VO2peak 57.3 ± 6.8 mL/kg/min) completed five visits in a double-blinded crossover design, performing two consecutive testing days, following a ventilatory thresholds assessment. Following 62 min of high-intensity cycling, participants lay on an ELF-EMF mattress under active (A) and non-active (NA) conditions, immediately post protocol and during the night. Physical performance and blood markers were assessed at baseline and at 60 min (60 P) and 24 h (24 H) post-protocol. The A-condition demonstrated a notable reduction in interleukin-10 (IL-10) concentrations (mean difference = -88%, p = 0.032) and maximal isometric strength of the quadriceps muscles (mean difference = ~8%, p = 0.045) compared to the NA-condition between 60 P and 24 H. In a sensitivity analysis, the A-condition revealed that younger athletes who possessed lower fat mass experienced attenuated inflammation and biochemical responses and improved physical performance. In conclusion, ELF-EMF showed no significant overall effects on performance and inflammation after intense cycling among athletes. Post-hoc analysis revealed modest benefits of ELF-MLF, suggesting a context-dependent impact. Further research with a larger sample size and multiple sessions is needed to confirm the recovery potential of ELF-EMF.

Submaximal fatiguing eccentric contractions of knee flexors alter leg extrapersonal representation

This study assessed the immediate and prolonged effects of eccentric-induced fatigue on position sense, utilizing position-pointing tasks, which had not been previously implemented for this purpose. Fifteen healthy adults underwent a fatiguing eccentric protocol that entailed sets of unilateral submaximal contractions of knee flexor muscles until reaching a 20% decrease in maximal isometric torque production. Evaluations of knee flexor neuromuscular function as well as position-pointing tasks at 40° and 70° of knee flexion were conducted prior to the fatiguing eccentric protocol, immediately after (POST), and 24 h after (POST24) exercise termination. To assess neuromuscular fatigue etiology, electrical myostimulations were administered during and after maximal voluntary isometric contractions. At POST, the voluntary activation level and evoked potentiated doublet amplitude at 100 Hz were significantly reduced. In addition, position-pointing errors exhibited a significant increase at POST regardless of the tested angle, with participants positioning the pointer in a more extended position compared to their hidden exercised limb. At POST24, neuromuscular function and position sense parameters had reverted to their baseline levels. The findings of this experiment demonstrate that position-pointing accuracy was impaired immediately after the fatiguing eccentric protocol, manifesting in the presence of both central and peripheral fatigue. As position-pointing accuracy relies heavily on extrapersonal representation of the body at the brain level, acute changes in exercised limb's extrapersonal representation might have resulted from central fatigue-related mechanisms altering the cognitive processes responsible for converting kinesthetic signals into extrapersonal coordinates.

Carbon Fiber Insoles Enhance Perception of Performance Despite Variable Objective Outcomes: Specific to the Moderately Active Individual

Carbon fiber insoles (CFIs) may benefit performance in elite athletes, however, their use in moderately active individuals has been adopted without evidence supporting such enhancements in this population. Fifteen male subjects performed vertical jump (VJ) and repeat treadmill sprint tests before and after a VO2peak while wearing 1) CFIs and 2) control insoles (CON). Subjects completed a subjective survey regarding their perceived performance abilities for both conditions. There were no significant differences between CFIs and CON in VJ height, sprint distance, heart rate following sprints; and rate of oxygen consumption, perceived fatigue, and perceived exertion at 85% of maximal speed (p > 0.05) during the VO2peak. At maximal speed, although there was no difference between conditions in peak rate of oxygen consumption (95%CI [-4.85, 0.21]) and respiratory exchange ratio (95%CI [-0.01, 0.03]), CFIs resulted in a reduced level of perceived fatigue (95%CI [-1, 0]) and perceived exertion (95%CI [-2, 0]) compared to CON. Subjects subjectively reported increased feelings of "propulsion or explosiveness" (p = 0.026) and being able to "perform better while jumping" (p = 0.029) while wearing CFIs. Heightened perceptions of performance enhancements when wearing CFIs indicate, in the moderately active, perceptual benefits could be more influential for determining CFI use.

Joint Hypermobility and Fatigue Are Associated With Injuries in a Group of Preprofessional Ballet Dancers

INTRODUCTION

Strenuous preprofessional ballet training places young students at an increased risk of injury. This represents a major concern for aspiring dancers since a link has been described between injury and dropping out. It is therefore important to identify physical and psychological factors related to injuries in dance for prevention purposes.

METHODS

In this cross-sectional study, we explored the frequency and characteristics of injuries, as well as their physical and psychological determinants in preprofessional ballet dancers. Seventy-three participants (women = 75.6%; mean age = 13.7; SD = 1.8) were evaluated with the Beighton criteria for joint hypermobility and self-questionnaires assessing injuries in the last 18 months, fatigue, fear of injury, and motivation.

RESULTS

Most of participants (61.6%) experienced injuries in the last 18 months, mainly in the lower limbs, and due to overuse. Multivariate analyses showed that joint hypermobility and fatigue predict injury status in this sample.

CONCLUSION

These results confirm previous reports suggesting that physical factors such as fatigue and joint hypermobility, that are frequent in ballet dancers, should be taken into account in order to prevent injuries.

Cooling vest improves surgeons' thermal comfort without affecting cognitive performance: a randomised cross-over trial

OBJECTIVES

Surgeons become uncomfortable while performing surgery because heat transfer and evaporative cooling are restricted by insulating surgical gowns. Consequently, perceptions of thermal discomfort during surgery may impair cognitive performance. We, therefore, aimed to evaluate surgeons' thermal comfort, cognitive performance, core and mean skin temperatures, perceptions of sweat-soaked clothing, fatigue and exertion with and without a CoolSource cooling vest (Cardinal Health, Dublin, Ohio, USA).

METHODS

Thirty orthopaedic surgeons participated in a randomised cross-over trial, each performing four total-joint arthroplasties with randomisation to one of four treatment sequences. The effects of cooling versus no cooling were measured using a repeated-measures linear model accounting for within-subject correlations.

RESULTS

The cooling vest improved thermal comfort by a mean (95% CI) of -2.1 (-2.7 to -1.6) points on a 0-10 scale, p<0.001, with no evidence of treatment-by-period interaction (p=0.94). In contrast, cooling had no perceptible effect on cognition, with an estimated mean difference (95% CI) in Cleveland Clinic Cognitive Battery (C3B) Processing Speed Test score of 0.03 (95% CI -2.44 to 2.51), p=0.98, or in C3B Visual Memory Test score with difference of 0.88 (95% CI -2.25 to 4.01), p=0.57. Core temperature was not lower with the cooling vest, with mean difference (95% CI) of -0.13 (-0.33°C to 0.07°C), p=0.19, while mean skin temperature was lower, with mean difference of -0.23 (95% CI -0.40°C to -0.06°C) lower, p=0.011. The cooling vest significantly reduced surgeons' perceptions of sweat-soaked clothing, fatigue and exertion.

CONCLUSIONS

A cooling vest worn during surgery lowered core and skin temperatures, improved thermal comfort, and decreased perceptions of sweating and fatigue, but did not improve cognition. Thermal discomfort during major orthopaedic surgery is thus largely preventable, but cooling does not affect cognition.

TRIAL REGISTRATION NUMBER

NCT04511208.

Assisted walking-in-place: Introducing assisted motion to walking-by-cycling in embodied virtual reality

In this paper, we investigate the use of a motorized bike to support the walk of a self-avatar in virtual reality (VR). While existing walking-in-place (WIP) techniques render compelling walking experiences, they can be judged repetitive and strenuous. Our approach consists in assisting a WIP technique so that the user does not have to actively move in order to reduce effort and fatigue. We chose to assist a technique called walking-by-cycling, which consists in mapping the cycling motion of a bike onto the walking of the user's self-avatar, by using a motorized bike. We expected that our approach could provide participants with a compelling walking experience while reducing the effort required to navigate. We conducted a within-subjects study where we compared "assisted walking-by-cycling" to a traditional active walking-by-cycling implementation, and to a standard condition where the user is static. In the study, we measured embodiment, including ownership and agency, walking sensation, perceived effort and fatigue. Results showed that assisted walking-by-cycling induced more ownership, agency, and walking sensation than the static simulation. Additionally, assisted walking-by-cycling induced levels of ownership and walking sensation similar to that of active walking-by-cycling, but it induced less perceived effort. Taken together, this work promotes the use of assisted walking-by-cycling in situations where users cannot or do not want to exert much effort while walking in embodied VR such as for injured or disabled users, for prolonged uses, medical rehabilitation, or virtual visits.

Impact loading in female runners with single and multiple bone stress injuries during fresh and exerted conditions

BACKGROUND

Bone stress injuries (BSIs) are common in female runners, and recurrent BSI rates are high. Previous work suggests an association between higher impact loading during running and tibial BSI. However, it is unknown whether impact loading and fatigue-related loading changes discriminate women with a history of multiple BSIs. This study compared impact variables at the beginning of a treadmill run to exertion and the changes in those variables with exertion among female runners with no history of BSI as well as among those with a history of single or multiple BSIs.

METHODS

We enrolled 45 female runners (aged 18-40 years) for this cross-sectional study: having no history of diagnosed lower extremity BSI (N-BSI, n = 14); a history of 1 lower extremity BSI (1-BSI, n = 16); and diagnosed by imaging, or a history of multiple (≥3) lower extremity BSIs (M-BSI, n = 15). Participants completed a 5-km race speed run on an instrumented treadmill while wearing an Inertial Measurement Unit. The vertical average loading rate (VALR), vertical instantaneous loading rate (VILR), vertical stiffness during impact via instrumented treadmill, and tibial shock determined as the peak positive tibial acceleration via Inertial Measurement Unit were measured at the beginning and the end of the run.

RESULTS

There were no differences between groups in VALR, VILR, vertical stiffness, or tibial shock in a fresh or exerted condition. However, compared to N-BSI, women with M-BSI had greater increase with exertion in VALR (-1.8% vs. 6.1%, p = 0.01) and VILR (1.5% vs. 4.8%, p = 0.03). Similarly, compared to N-BSI, vertical stiffness increased more with exertion among women with M-BSI (-0.9% vs. 7.3%, p = 0.006) and 1-BSI (-0.9% vs. 1.8%, p = 0.05). Finally, compared to N-BSI, the increase in tibial shock from fresh to exerted condition was greater among women with M-BSI (0.9% vs. 5.5%, p = 0.03) and 1-BSI (0.9% vs. 11.2%, p = 0.02).

CONCLUSION

Women with 1-BSI or M-BSIs experience greater exertion-related increases in impact loading than women with N-BSI. These observations imply that exertion-related changes in gait biomechanics may contribute to risk of BSI.

Physical Activity Effects on Muscle Fatigue in Sport in Active Adults with Long COVID-19: An Observational Study

Long COVID-19-related changes in physiology includes alterations in performing muscle work as fatigue. Data available do not allow us to define the usefulness of physical activity to attenuate long COVID-19 functional modifications. The present observational study investigates the effects of physical activity on the perception of fatigue, maximum power output, sleep, and cognitive modifications in subjects affected by long COVID-19, distinguishing between active and sedentary subjects. The data demonstrated the following: the perception of fatigue 1 year after the end of virus positivity was significantly reduced with respect to that observed after 6 months by more than 50% more in active subjects compared to sedentary ones; 6 months after the end of virus positivity, the force developed by active subjects was reduced (RM factor: p < 0.001, η2p = 0.527, post hoc: p < 0.001), but the reduction was more pronounced in sedentary ones (mean difference = 38.499 W); poor sleep quality and mild cognitive impairment were assessed in both active and sedentary subjects. In conclusion, the study suggests that the long COVID-19 fatigue was lower in active subjects respect to sedentary ones. A comparative analysis performed due to the overlap of functional alterations between long COVID-19 and ME/CFS showed that in a small percentage of the enrolled subjects (8%), the symptomatology reflected that of ME/CFS and was independent of the individual physical capacities.

Shorter High-Intensity Cycling Intervals Reduce Performance and Perceived Fatigability at Work-Matched but Not Task Failure

INTRODUCTION

The intensity, duration, and distribution of work and recovery phases during high-intensity interval training (HIIT) modulate metabolic perturbations during exercise and subsequently influence the development of performance fatigability and exercise tolerance. This study aimed to characterize neuromuscular, perceptual, and cardiorespiratory responses to work-to-rest ratio-matched HIIT protocols differing in work and rest interval duration.

METHODS

Twelve healthy individuals (six women) first completed a ramp incremental test to determine 90% of peak power output, and then in three randomized visits, they completed three cycling protocols to task failure at 90% of peak power output: (i) 3- to 3-min work-to-passive rest ratio HIIT (HIIT 3min ), (ii) 1- to 1-min work-to-passive rest ratio HIIT (HIIT 1min ), and (iii) constant load (CL). Interpolated twitch technique, including maximal voluntary isometric knee extensions and femoral nerve electrical stimuli, was performed at baseline, every 6 min of work, and task failure. Perceptual and cardiorespiratory responses were recorded every 3 min and continuously across the exercises, respectively.

RESULTS

The work completed during HIIT 1min (8447 ± 5124 kJ) was considerably greater than HIIT 3min (1930 ± 712 kJ) and CL (1076 ± 356) ( P < 0.001). At work-matched, HIIT 1min resulted in a lesser decline in maximal voluntary contraction and twitch force compared with HIIT 3min and CL ( P < 0.001). Perceived effort, pain, and dyspnea were least in HIIT 1min and HIIT 3min compared with CL ( P < 0.001). At task failure, HIIT 1min resulted in less voluntary activation than HIIT 3min ( P = 0.010) and CL ( P = 0.043), and engendered less twitch force decline than CL ( P = 0.021).

CONCLUSIONS

Overall, the mitigated physiological and perceptual responses during shorter work periods (HIIT 1min ) enhance exercise tolerance in comparison to longer work intervals at the same intensity (HIIT 3min , CL).

Effect of Running-Induced Fatigue on Tibial Acceleration and the Role of Lower Limb Muscle Strength, Power, and Endurance

BACKGROUND

High-impact loads have been linked with running injuries. Fatigue has been proposed to increase impact loads, but this relationship has not been rigorously examined, including the associated role of muscle strength, power, and endurance.

PURPOSE

This study aimed to investigate the effect of fatigue on impact loading in runners and the role of muscle function in mediating changes in impact loading with fatigue.

METHODS

Twenty-eight trained endurance runners performed a fixed-intensity time to exhaustion test at 85% of V̇O 2max . Tibial accelerations were measured using leg-mounted inertial measurement units and sampled every minute until volitional exhaustion. Tests of lower limb muscle strength, power, and endurance included maximal isometric strength (soleus, knee extensors, and knee flexors), single leg hop for distance, and the one leg rise test. Changes in peak tibial acceleration (PTA, g ) were compared between time points throughout the run (0%, 25%, 50%, 75%, and 100%). Associations between the change in PTA and lower limb muscle function tests were assessed (Spearman's rho [ rs ]).

RESULTS

PTA increased over the duration of the fatiguing run. Compared with baseline (0%) (mean ± SD, 9.1 g ± 1.6 g ), there was a significant increase at 75% (9.9 g ± 1.7 g , P = 0.001) and 100% (10.1 g ± 1.8 g , P < 0.001), with no change at 25% (9.6 g ± 1.6 g , P = 0.142) or 50% (9.7 g ± 1.7 g , P = 0.053). Relationships between change in PTA and muscle function tests were weak and not statistically significant ( rs = -0.153 to 0.142, all P > 0.05).

CONCLUSIONS

Peak axial tibial acceleration increased throughout a fixed-intensity run to exhaustion. The change in PTA was not related to performance in lower limb muscle function tests.

Blood flow restriction during high-intensity interval cycling exacerbates psychophysiological responses to a greater extent in females than males

This study aimed to characterize neuromuscular, perceptual, and cardiorespiratory responses to high-intensity interval training (HIIT) with superimposed blood flow restriction in males and females. Twenty-four, healthy individuals (n = 12 females) completed two cycling HIIT protocols to task failure (1-min work phases at 90% of peak power output interspersed by 1-min rest phases). The blood flow restriction (BFR) and control (CON) protocols were identical except for the presence and absence of BFR during rest phases, respectively. The interpolated twitch technique, including maximal voluntary isometric knee extension (MVC) and femoral nerve electrical stimuli, was performed at baseline, every six intervals, and task failure. Perceptual and cardiorespiratory responses were recorded every three intervals and continuously during exercise, respectively. Bayesian inference was used to obtain the joint posterior distribution for all parameters and evidence of an effect was determined via the marginal posterior probability (PP). The BFR shortened task duration by 57.3% compared with CON (PP > 0.99), without a sex difference. The application of BFR exacerbated the rate of decline in neuromuscular measures (MVC and twitch force output), increase of perceptual responses (perceived effort, pain, dyspnea, fatigue), and development of cardiorespiratory parameters (minute ventilation and heart rate), compared with CON (PP > 0.95). In addition, BFR exacerbated the neuromuscular, perceptual, and cardiorespiratory responses to a greater extent in females than males (PP > 0.99). Our results suggest that superimposition of blood flow restriction exacerbates psychophysiological responses to a HIIT protocol to a greater extent in females than males.NEW & NOTEWORTHY To our knowledge, no study has explored sex differences in the neuromuscular, perceptual, and cardiorespiratory indices characterizing exercise tolerance during high-intensity interval training (HIIT) with blood flow restriction (BFR) applied only during rest periods. Our results suggest that BFR elicited a decline in exercise performance that could be attributed to integration of psychophysiological responses. However, this integration was sex-dependent where females demonstrated an exacerbated rate of change in these responses compared with males.

The relationship between ratings of perceived exertion (RPE) and relative strength for a fatiguing dynamic upper extremity task: A consideration of multiple cycles and conditions

The goal of this study was to evaluate the relationship between ratings of perceived exertion (RPE) and relative strength with respect to baseline for a fatiguing free dynamic task targeting the upper extremity, namely simulated order picking, and determine whether the relationship remains the same for different conditions (i.e., pace and weight) and with fatigue. Fourteen participants (seven males, seven females) performed four sessions that included two 45-min work periods separated by 15 min of rest. The work periods involved picking weighted bottles from shoulder height and packaging them at waist height for four combinations of bottle mass and picking rate: 2.5 kg-15 bottles per minute (bpm), 2.5 kg-10 bpm, 2.5 kg-5 bpm, and 1.5 kg-15 bpm. Participants reported their RPEs every 5 min and performed a maximum isometric shoulder flexion exertion every 9 min. Pearson product-moment correlation was used to evaluate the linear relationship between RPE and relative strength for each subject and work period. Then, the effects of condition and work period on the average relationship were assessed using a repeated-measures analysis of variance (ANOVA). For the first 45-min period, there were no significantly different correlations between RPE and relative strength across conditions (average r = -0.62 (standard deviation = 0.38); p = 0.57). There was a significant decrease in average correlation for the second work period (r = -0.39 (0.53)). These results suggest that individual subjective responses consistently increase while relative strength declines when starting from a non-fatigued state. However, correlations are weaker when re-engaging in work following incomplete recovery. Thus, starting fatigue levels should be accounted for when considering the expected relationship between RPE and relative strength.

Perceptions of fatigue and neuromuscular measures of performance fatigability during prolonged low-intensity elbow flexions

NEW FINDINGS

What is the central question of this study? What is the predictive relationship between self-reported scales to quantify perceptions of fatigue during exercise and gold standard measures used to quantify the development of neuromuscular fatigue? What is the main finding and its importance? No scale was determined to be substantively more effective than another. However, the number of ongoing contractions performed was shown to be a better predictor of fatigue in the motor system than any of the subjective scales.

ABSTRACT

The purpose of this study was to determine the relationship between transcranial magnetic stimulation (TMS) measures of performance fatigability and commonly used scales that quantify perceptions of fatigue during exercise. Twenty healthy participants (age 23 ± 3 years, 10 female) performed 10 submaximal isometric elbow flexions at 20% maximal voluntary contraction (MVC) for 2 min, separated by 45 s of rest. Biceps brachii muscle electromyography and elbow flexion torque responses to single-pulse TMS were obtained at the end of each contraction to assess central factors of performance fatigability. A rating of perceived exertion (RPE) scale, Omnibus Resistance scale, Likert scale, Rating of Fatigue scale and a visual analogue scale (VAS) were used to assess perceptions of fatigue at the end of each contraction. The RPE (root mean square error (RMSE) = 0.144) and Rating of Fatigue (RMSE = 0.145) scales were the best predictors of decline in MVC torque, whereas the Likert (RMSE= 0.266) and RPE (RMSE= 0.268) scales were the best predictors of electromyographic amplitude. Although the Likert (RMSE = 7.6) and Rating of Fatigue (RMSE = 7.6) scales were the best predictors of voluntary muscle activation of any scale, the number of contractions performed during the protocol was a better predictor (RMSE = 7.3). The ability of the scales to predict TMS measures of performance fatigability were in general similar. Interestingly, the number of contractions performed was a better predictor of TMS measures than the scales themselves.

Perspectives on Postmatch Fatigue From 300 Elite European Soccer Players

PURPOSE

To examine the general perspectives of elite soccer players on the time course of perceived postmatch fatigue and the influence of away matches on subjective perceptions.

METHODS

Adopting a cross-sectional study design, we invited 371 subjects from 14 top-division European clubs competing in the Belgian First Division A, English Premier League, French Ligue 1, Italian Serie A, Portuguese Primeira Liga, Russian Premier League, and Swiss Premier League to take part in a short survey on general issues relating to postmatch fatigue measurement and tracking in professional soccer.

RESULTS

Three hundred male professional soccer players completed the short questionnaire. For perceptions relevant to the time course of postmatch fatigue, two-thirds of respondents (67%) indicated higher postmatch fatigue perceived 2 days (48 h) after an official competition. Among these respondents, a higher proportion of answers was observed in wide midfielders (74%), attackers (74%), and central midfielders (68%). Approximately two-thirds of respondents (63%) indicated more than usual and much more than usual perceived postmatch fatigue following away matches.

CONCLUSIONS

For the first time, our investigation addressed practical aspects that remained unexplored and fundamental to the definition of an optimal player management process following a competition. From a practical standpoint, perspectives of individual elite soccer players substantiated the notion of implementing processes with dedicated recovery protocols within 48 hours postmatch and highlighted the need for differential strategies addressing the additional burden of away matches and travel.