The limit to exercise tolerance in humans: mind over muscle?

The impact of task (un)certainty on repeated grip force production

Many studies found that in physical tasks, reducing certainty regarding their endpoints hinders performance. However, the impact of reducing certainty regarding other aspects of physical tasks is unknown. Here we manipulated the certainty of the required effort on an unrelated, parallel task (i.e., off-task uncertainty) and examined how it impacts force production in two within-subject experiments (N = 79). In two sessions, subjects completed 20 repetitions composed of maximal forces using a gripper with their dominant hand. Between repetitions, participants applied either submaximal constant or varied grip forces, with their non-dominant arm, matched for total forces across repetitions. While we observed trivial differences in total forces between conditions, under the varied condition, participants produced a steeper decrease in forces, suggesting that off-task uncertainty impacted their effort allocation strategy. We speculate that this pattern can be attributed to cognitive overload and/or changes in motivation stemming from the imposed uncertainty.

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.

Enhancing endurance performance with combined imagined and actual physical practice

PURPOSE

The perception of effort exerts influence in determining task failure during endurance performance. Training interventions blending physical and cognitive tasks yielded promising results in enhancing performance. Motor imagery can decrease the perception of effort. Whether combining motor imagery and physical training improves endurance remains to be understood, and this was the aim of this study.

METHODS

Participants (24 ± 3 year) were assigned to a motor imagery (n = 16) or a control (n = 17) group. Both groups engaged in physical exercises targeting the knee extensors (i.e., wall squat, 12 training sessions, 14-days), with participants from the motor imagery group also performing motor imagery. Each participant visited the laboratory Pre and Post-training, during which we assessed endurance performance through a sustained submaximal isometric knee extension contraction until task failure, at either 20% or 40% of the maximal voluntary contraction peak torque. Perceptions of effort and muscle pain were measured during the exercise.

RESULTS

We reported no changes in endurance performance for the control group. Endurance performance in the motor imagery group exhibited significant improvements when the intensity of the sustained isometric exercise closely matched that used in training. These enhancements were less pronounced when considering the higher exercise intensity. No reduction in perception of effort was observed in both groups. There was a noticeable decrease in muscle pain perception within the motor imagery group Post training.

CONCLUSION

Combining motor imagery and physical training may offer a promising avenue for enhancing endurance performance and managing pain in various contexts.

The effects of sustained, low- and high-intensity isometric tasks on performance fatigability and the perceived responses that contributed to task termination

PURPOSE

The present study examined the effects of sustained, isometric low- versus high-intensity tasks on time to task failure (TTF), performance fatigability (PF), ratings of perceived exertion (RPE), and the perceived causes of task termination from a post-test questionnaire (PTQ).

METHODS

Ten men (mean ± SD: age = 21.1 ± 2.3 years; height = 180.2 ± 5.7 cm; body mass = 79.5 ± 8.8 kg) performed maximal voluntary isometric contractions (MVICs) before and after fatiguing, isometric forearm flexion tasks anchored to the torque corresponding to RPE values of 2 (TRQ2FT = 23.8 ± 7.1 N·m) and 8 (TRQ8FT = 60.9 ± 11.4 N·m). In addition, the subjects completed a PTQ which surveyed whether the perceived sensations of fatigue or pain, and/or the psychological factors of loss of focus and motivation contributed to the decision to terminate the task. Repeated measures ANOVAs, Wilcoxon-Signed Rank tests, and Spearman's Rank-Order Correlations were used to analyze the data.

RESULTS

Across the fatiguing tasks, there were similar decreases in MVIC torque (95.2 ± 20.3 vs. 68.9 ± 15.6 N·m; p < 0.001) and RPE values (p = 0.122) at task failure for TRQ2FT (7.4 ± 2.7) and TRQ8FT (8.9 ± 1.0), but a longer (p = 0.005) TTF for the TRQ2FT (245.0 ± 177.0 s) than TRQ8FT (36.8 ± 11.1 s).

CONCLUSIONS

Despite reaching task failure, the subjects were able to perform MVICs that were 100-300% greater than the target torque values within seconds of terminating the tasks. Thus, we hypothesized that task failure was not caused by an inability to produce sufficient torque to sustain the tasks, but rather an unwillingness to continue the task.

Menthol alleviates post-race elevations in muscle soreness and metabolic and respiratory stress during running

PURPOSE

We evaluated (1) whether participating in middle- and long-distance running races augments muscle soreness, oxygen cost, respiration, and exercise exertion during subsequent running, and (2) if post-race menthol application alleviates these responses in long-distance runners.

METHODS

Eleven long-distance runners completed a 1500-m race on day 1 and a 3000-m race on day 2. On day 3 (post-race day), either a 4% menthol solution (Post-race menthol) or a placebo solution (Post-race placebo) serving as a vehicle control, was applied to their lower leg skin, and their perceptual and physiological responses were evaluated. The identical assessment with the placebo solution was also conducted without race participation (No-race placebo).

RESULTS

The integrated muscle soreness index increased in the Post-race placebo compared to the No-race placebo (P < 0.001), but this response was absent in the Post-race menthol (P = 0.058). Oxygen uptake during treadmill running tended to be higher (4.3%) in the Post-race placebo vs. No-race placebo (P = 0.074). Oxygen uptake was 5.4% lower in the Post-race menthol compared to the Post-race placebo (P = 0.018). Minute ventilation during treadmill running was 6.7-7.6% higher in the Post-race placebo compared to No-race placebo, whereas it was 6.6-9.0% lower in the Post-race menthol vs. Post-race placebo (all P ≤ 0.001). The rate of perceived exertion was 7.0% lower in the Post-race menthol vs. Post-race placebo (P = 0.007).

CONCLUSIONS

Middle- and long-distance races can subsequently elevate muscle soreness and induce respiratory and metabolic stress, but post-race menthol application to the lower legs can mitigate these responses and reduce exercise exertion in long-distance runners.

Limits of Ultra: Towards an Interdisciplinary Understanding of Ultra-Endurance Running Performance

Ultra-endurance running (UER) poses extreme mental and physical challenges that present many barriers to completion, let alone performance. Despite these challenges, participation in UER events continues to increase. With the relative paucity of research into UER training and racing compared with traditional endurance running distance (e.g., marathon), it follows that there are sizable improvements still to be made in UER if the limitations of the sport are sufficiently understood. The purpose of this review is to summarise our current understanding of the major limitations in UER. We begin with an evolutionary perspective that provides the critical background for understanding how our capacities, abilities and limitations have come to be. Although we show that humans display evolutionary adaptations that may bestow an advantage for covering large distances on a daily basis, these often far exceed the levels of our ancestors, which exposes relative limitations. From that framework, we explore the physiological and psychological systems required for running UER events. In each system, the factors that limit performance are highlighted and some guidance for practitioners and future research are shared. Examined systems include thermoregulation, oxygen delivery and utilisation, running economy and biomechanics, fatigue, the digestive system, nutritional and psychological strategies. We show that minimising the cost of running, damage to lower limb tissue and muscle fatigability may become crucial in UER events. Maintaining a sustainable core body temperature is critical to performance, and an even pacing strategy, strategic heat acclimation and individually calculated hydration all contribute to sustained performance. Gastrointestinal issues affect almost every UER participant and can be due to a variety of factors. We present nutritional strategies for different event lengths and types, such as personalised and evidence-based approaches for varying types of carbohydrate, protein and fat intake in fluid or solid form, and how to avoid flavour fatigue. Psychology plays a vital role in UER performance, and we highlight the need to be able to cope with complex situations, and that specific long and short-term goal setting improves performance. Fatigue in UER is multi-factorial, both physical and mental, and the perceived effort or level of fatigue have a major impact on the ability to continue at a given pace. Understanding the complex interplay of these limitations will help prepare UER competitors for the different scenarios they are likely to face. Therefore, this review takes an interdisciplinary approach to synthesising and illuminating limitations in UER performance to assist practitioners and scientists in making informed decisions in practice and applicable research.

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

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

Physical Exercise to Redynamize Interoception in Substance use Disorders

Physical exercise is considered a promising medication-free and cost-effective adjunct treatment for substance use disorders (SUD). Nevertheless, evidence regarding the effectiveness of these interventions is currently limited, thereby signaling the need to better understand the mechanisms underlying their impact on SUD, in order to reframe and optimize them. Here we advance that physical exercise could be re-conceptualized as an "interoception booster", namely as a way to help people with SUD to better decode and interpret bodily-related signals associated with transient states of homeostatic imbalances that usually trigger consumption. We first discuss how mismatches between current and desired bodily states influence the formation of reward-seeking states in SUD, in light of the insular cortex brain networks. Next, we detail effort perception during physical exercise and discuss how it can be used as a relevant framework for re-dynamizing interoception in SUD. We conclude by providing perspectives and methodological considerations for applying the proposed approach to mixed-design neurocognitive research on SUD.

Influence of Recovery Mode on the Maximum Number of Intervals Until Exhaustion During an Aerobic Interval Training Session

ABSTRACT

Varela-Sanz, A, Sánchez-Otero, T, Tuimil, JL, Boullosa, D, and Iglesias-Soler, E. Influence of recovery mode on the maximum number of intervals until exhaustion during an aerobic interval training session. J Strength Cond Res 37(9): e510-e520, 2023-We analyzed work capacity, cardiometabolic, perceptual, and neuromuscular responses to an aerobic interval training (AIT) running session until exhaustion, with active (AR) vs. passive recovery (PR). Eight well-trained male endurance runners (36.88 ± 7.14 years, 58.22 ± 3.39 ml·kg -1 ·minute -1 ) randomly completed, after familiarizations and the University of Montreal Track Test (UMTT), 2 AIT track running sessions until exhaustion consisting in 2-minute bouts at 100% of maximum aerobic speed (MAS), with 2 minutes of recovery at 80% of the velocity associated to the second ventilatory threshold (vVT 2 ) (i.e., AR), or no exercise (i.e., PR). Oxygen consumption (V̇O 2 ), heart rate (HR), blood lactate [La], rating of perceived exertion (RPE), and countermovement jump (CMJ) were continuously monitored during sessions. The level of statistical significance was set at p ≤ 0.05. PR resulted in longer time to exhaustion during sessions (13.9 vs. 11.6 bouts, p = 0.045), but lower HR ( p < 0.01) when compared with AR. Time spent over 90% of maximum oxygen consumption (V̇O 2max ), blood lactate concentrations, neuromuscular performance, and RPE did not differ between AR and PR ( p > 0.05). Thus, PR allowed runners to perform more work intervals and, therefore, to accumulate a greater volume. On the other hand, when training goals are focused on reaching a higher chronotropic stress (i.e., higher HR) during the training session, athletes would obtain more benefits from AR. This study also demonstrates that the current volume recommendations for AIT are far below (54-64.5%) the maximum training capacity of well-trained runners.

Conventional methods to prescribe exercise intensity are ineffective for exhaustive interval training

PURPOSE

To compare methods of relative intensity prescription for their ability to normalise performance (i.e., time to exhaustion), physiological, and perceptual responses to high-intensity interval training (HIIT) between individuals.

METHODS

Sixteen male and two female cyclists (age: 38 ± 11 years, height: 177 ± 7 cm, body mass: 71.6 ± 7.9 kg, maximal oxygen uptake ([Formula: see text]O2max): 54.3 ± 8.9 ml·kg-1 min-1) initially undertook an incremental test to exhaustion, a 3 min all-out test, and a 20 min time-trial to determine prescription benchmarks. Then, four HIIT sessions (4 min on, 2 min off) were each performed to exhaustion at: the work rate associated with the gas exchange threshold ([Formula: see text]GET) plus 70% of the difference between [Formula: see text]GET and the work rate associated with [Formula: see text]O2max; 85% of the maximal work rate of the incremental test (85%[Formula: see text]max); 120% of the mean work rate of the 20 min time-trial (120%TT); and the work rate predicted to expend, in 4 min, 80% of the work capacity above critical power. Acute HIIT responses were modelled with participant as a random effect to provide estimates of inter-individual variability.

RESULTS

For all dependent variables, the magnitude of inter-individual variability was high, and confidence intervals overlapped substantially, indicating that the relative intensity normalisation methods were similarly poor. Inter-individual coefficients of variation for time to exhaustion varied from 44.2% (85%[Formula: see text]max) to 59.1% (120%TT), making it difficult to predict acute HIIT responses for an individual.

CONCLUSION

The present study suggests that the methods of intensity prescription investigated do not normalise acute responses to HIIT between individuals.

Sodium Bicarbonate and Time-to-Exhaustion Cycling Performance: A Retrospective Analysis Exploring the Mediating Role of Expectation

BACKGROUND

Research has shown that ingesting 0.3 g·kg^-1 body mass sodium bicarbonate (NaHCO₃) can improve time-to-exhaustion (TTE) cycling performance, but the influence of psychophysiological mechanisms on ergogenic effects is not yet understood.

OBJECTIVE

This study retrospectively examined whether changes in TTE cycling performance are mediated by positive expectations of receiving NaHCO₃ and/or the decline in blood bicarbonate during exercise.

METHODS

In a randomised, crossover, counterbalanced, double-blind, placebo-controlled design, 12 recreationally trained cyclists (maximal oxygen consumption, 54.4 ± 5.7 mL·kg·min^-1) performed four TTE cycling tests 90 min after consuming: (1) 0.3 g·kg^-1 body mass NaHCO₃ in 5 mL·kg^-1 body mass solution, (2) 0.03 g·kg^-1 body mass sodium chloride in solution (placebo), (3) 0.3 g·kg^-1 body mass NaHCO₃ in capsules and (4) cornflour in capsules (placebo). Prior to exercise, participants rated on 1-5 Likert type scales how much they expected the treatment they believe had been given would improve performance. Capillary blood samples were measured for acid-base balance at baseline, pre-exercise and post-exercise.

RESULTS

Administering NaHCO₃ in solution and capsules improved TTE compared with their respective placebos (solution: 27.0 ± 21.9 s, p = 0.001; capsules: 23.0 ± 28.1 s, p = 0.016). Compared to capsules, NaHCO₃ administered via solution resulted in a higher expectancy about the benefits on TTE cycling performance (Median: 3.5 vs. 2.5, Z = 2.135, p = 0.033). Decline in blood bicarbonate during exercise was higher for NaHCO₃ given in solution compared to capsules (2.7 ± 2.1 mmol·L^-1, p = 0.001). Mediation analyses showed that improvements in TTE cycling were indirectly related to expectancy and decline in blood bicarbonate when NaHCO₃ was administered in solution but not capsules.

CONCLUSIONS

Participants' higher expectations when NaHCO₃ is administered in solution could result in them exerting themselves harder during TTE cycling, which subsequently leads to a greater decline in blood bicarbonate and larger improvements in performance.

KEY POINTS

Ingesting 0.3 g·kg^-1 body mass sodium bicarbonate in solution and capsules improved time-to-exhaustion cycling performance Positive expectancy about the benefits of sodium bicarbonate and decline in blood bicarbonate were higher when sodium bicarbonate was administered in solution compared with capsules Improvements in time-to-exhaustion cycling performance for sodium bicarbonate administered in solution were related to expectancy and the enhanced extracellular buffering response.

The Effect of Skeletal Muscle Oxygenation on Hemodynamics, Cerebral Oxygenation and Activation, and Exercise Performance during Incremental Exercise to Exhaustion in Male Cyclists

This study aimed to elucidate whether muscle blood flow restriction during maximal exercise is associated with alterations in hemodynamics, cerebral oxygenation, cerebral activation, and deterioration of exercise performance in male participants. Thirteen healthy males, cyclists (age 33 ± 2 yrs., body mass: 78.6 ± 2.5 kg, and body mass index: 25.57 ± 0.91 kg·m^-1), performed a maximal incremental exercise test on a bicycle ergometer in two experimental conditions: (a) with muscle blood flow restriction through the application of thigh cuffs inflated at 120 mmHg (with cuffs, WC) and (b) without restriction (no cuffs, NC). Exercise performance significantly deteriorated with muscle blood flow restriction, as evidenced by the reductions in V˙O_2max (-17 ± 2%, p < 0.001), peak power output (-28 ± 2%, p < 0.001), and time to exhaustion (-28 ± 2%, p < 0.001). Muscle oxygenated hemoglobin (Δ[O₂Hb]) during exercise declined more in the NC condition (p < 0.01); however, at exhaustion, the magnitude of muscle oxygenation and muscle deoxygenation were similar between conditions (p > 0.05). At maximal effort, lower cerebral deoxygenated hemoglobin (Δ[HHb]) and cerebral total hemoglobin (Δ[THb]) were observed in WC (p < 0.001), accompanied by a lower cardiac output, heart rate, and stroke volume vs. the NC condition (p < 0.01), whereas systolic blood pressure, rating of perceived exertion, and cerebral activation (as assessed by electroencephalography (EEG) activity) were similar (p > 0.05) between conditions at task failure, despite marked differences in exercise duration, maximal aerobic power output, and V˙O_2max. In conclusion, in trained cyclists, muscle blood flow restriction during an incremental cycling exercise test significantly limited exercise performance. Exercise intolerance with muscle blood flow restriction was mainly associated with attenuated cardiac responses, despite cerebral activation reaching similar maximal levels as without muscle blood flow restriction.

Impact of physical and mental fatigue on construction workers' unsafe behavior based on physiological measurement

INTRODUCTION

Construction worker fatigue is an important factor leading to unsafe behavior, a major cause of construction accidents. Uncovering the impact mechanism of fatigue on workers' unsafe behavior can prevent construction accidents. However, it is difficult to effectively measure workers' fatigue onsite and analyze the impact of worker fatigue on their unsafe behavior.

METHOD

This research analyzes the relationship between the physical and mental fatigue of construction workers and their unsafe behavior via physiological measurement based on a simulated experiment on handling tasks.

RESULTS

It is found that: (a) both physical fatigue and mental fatigue have negative effects on workers' cognitive ability and motion ability, and the negative effects are more serious under the combination of the two types of fatigue; (b) mental fatigue can easily change workers' risk propensity, making them more willing to face risks, and in a state of the two types of fatigue, they are more likely to make choices with less pay and higher risk; (c) the number of signal identification errors is positively correlated with LF (low frequency)/HF (high frequency), and negatively correlated with the standard deviation of normal-to-normal intervals (SDNN), while the number of footstep control errors is negatively correlated with the time elapsed between two successive R waves (RR interval) and skin temperature (SKT).

PRACTICAL APPLICATIONS

These findings can enrich construction safety management theory from a perspective of quantified fatigue and facilitate safety management practices on construction sites, thus contributing to the body of knowledge and practices of construction safety management.

Acute Effects of New Zealand Blackcurrant Extract on Cycling Time-Trial Are Performance Dependent in Endurance-Trained Cyclists: A Home-Based Study

The intake of anthocyanin-rich New Zealand blackcurrant (NZBC) extract (300 mg per day) over a week enhanced 16.1 km cycling time trial (TT) performance in endurance-trained cyclists without acute performance effects. In the present study, the acute effects of an intake of 900 mg of NZBC extract 2 h before performing the 16.1 km cycling TT were examined. A total of 34 cyclists (26 males; 8 females) (age: 38 ± 7 years, V˙O_2max: 57 ± 5 mL·kg^-1·min^-1) completed 4 16.1 km TTs (2 familiarization and 2 experimental trials) over 4 mornings on a home turbo-trainer connected with the online training simulator ZWIFT. There was no difference in time to complete the 16.1 km TT between conditions (placebo: 1422 ± 104 s; NZBC extract: 1414 ± 93 s, p = 0.07). However, when participants were split between faster (<1400 s; 1 female; 16 males) and slower (>1400 s; 7 females; 10 males) cyclists based on average familiarization TTs, a difference in TT performance was observed only in the slower group (placebo: 1499 ± 91 s; NZBC extract: 1479 ± 83 s, p = 0.02). At 12 km (quartile analysis), power output (p = 0.04) and speed (p = 0.04) were higher compared to the placebo with no effects on heart rate and cadence. The acute effects of 900 mg of NZBC extract on a 16.1 km cycling time-trial may depend on the performance ability of male endurance-trained cyclists. More work is needed to address whether there is a sex-specific time-trial effect of NZBC extract independent of performance ability.

Qualitative and quantitative evidence of motivation states for physical activity, exercise and being sedentary from university student focus groups

Motivation for physical activity and sedentary behaviors (e.g., desires, urges, wants, cravings) varies from moment to moment. According to the WANT model, these motivation states may be affectively-charged (e.g., felt as tension), particularly after periods of maximal exercise or extended rest. The purpose of this study was to examine postulates of the WANT model utilizing a mixed-methods approach. We hypothesized that: (1) qualitative evidence would emerge from interviews to support this model, and (2) motivation states would quantitatively change over the course of an interview period. Seventeen undergraduate students (mean age = 18.6y, 13 women) engaged in focus groups where 12 structured questions were presented. Participants completed the "right now" version of the CRAVE scale before and after interviews. Qualitative data were analyzed with content analysis. A total of 410 unique lower-order themes were classified and grouped into 43 higher order themes (HOTs). From HOTs, six super higher order themes (SHOTs) were designated: (1) wants and aversions, (2) change and stability, (3) autonomy and automaticity, (4) objectives and impulses, (5) restraining and propelling forces, and (6) stress and boredom. Participants stated that they experienced desires to move and rest, including during the interview, but these states changed rapidly and varied both randomly as well as systematically across periods of minutes to months. Some also described a total absence of desire or even aversion to move and rest. Of note, strong urges and cravings for movement, typically from conditions of deprivation (e.g., sudden withdrawal from exercise training) were associated with physical and mental manifestations, such as fidgeting and feeling restless. Urges were often consummated with behavior (e.g., exercise sessions, naps), which commonly resulted in satiation and subsequent drop in desire. Importantly, stress was frequently described as both an inhibitor and instigator of motivation states. CRAVE-Move increased pre-to-post interviews (p < .01). CRAVE-Rest demonstrated a trend to decline (p = .057). Overall, qualitative and quantitative data largely corroborated postulates of the WANT model, demonstrating that people experience wants and cravings to move and rest, and that these states appear to fluctuate significantly, especially in the context of stress, boredom, satiety, and deprivation.

Utilizing the RPE-Clamp model to examine interactions among factors associated with perceived fatigability and performance fatigability in women and men

PURPOSE

The purpose of the present study was to examine the interactions between perceived fatigability and performance fatigability in women and men by utilizing the RPE-Clamp model to assess the fatigue-induced effects of a sustained, isometric forearm flexion task anchored to RPE = 8 on time to task failure (TTF), torque, and neuromuscular responses.

METHODS

Twenty adults (10 men and 10 women) performed two, 3 s forearm flexion maximal voluntary isometric contractions (MVICs) followed by a sustained, isometric forearm flexion task anchored to RPE = 8 using the OMNI-RES (0-10) scale at an elbow joint angle of 100°. Electromyographic amplitude (EMG AMP) was recorded from the biceps brachii. Torque and EMG AMP values resulting from the sustained task were normalized to the pretest MVIC. Neuromuscular efficiency was defined as NME = normalized torque/normalized EMG AMP. Mixed factorial ANOVAs and Bonferroni corrected dependent t tests and independent t tests were used to examine differences across time and between sex for torque and neuromuscular parameters.

RESULTS

There were no differences between the women and men for the fatigue-induced decreases in torque, EMG AMP, or NME, and the mean decreases (collapsed across sex) were 50.3 ± 8.6 to 2.8 ± 2.9% MVIC, 54.7 ± 12.0 to 19.6 ± 5.3% MVIC, and 0.94 ± 0.19 to 0.34 ± 0.16, respectively. Furthermore, there were no differences between the women and men for TTF (251.8 ± 74.1 vs. 258.7 ± 77.9 s).

CONCLUSION

The results suggested that the voluntary reductions in torque to maintain RPE and the decreases in NME were likely due to group III/IV afferent feedback from peripheral fatigue that resulted in excitation-contraction coupling failure.

Interindividual Variability in Mental Fatigue-Related Impairments in Endurance Performance: A Systematic Review and Multiple Meta-regression

BACKGROUND

The negative effect of mental fatigue (MF) on physical performance has recently been questioned. One reason behind this could lie in the interindividual differences in MF-susceptibility and the individual features influencing them. However, the range of individual differences in mental fatigue-susceptibility is not known, and there is no clear consensus on which individual features could be responsible for these differences.

OBJECTIVE

To give an overview of interindividual differences in the effects of MF on whole-body endurance performance, and individual features influencing this effect.

METHODS

The review was registered on the PROSPERO database (CRD42022293242). PubMed, Web of Science, SPORTDiscus and PsycINFO were searched until the 16th of June 2022 for studies detailing the effect of MF on dynamic maximal whole-body endurance performance. Studies needed to include healthy participants, describe at least one individual feature in participant characteristics, and apply at least one manipulation check. The Cochrane crossover risk of bias tool was used to assess risk of bias. The meta-analysis and regression were conducted in R.

RESULTS

Twenty-eight studies were included, with 23 added to the meta-analysis. Overall risk of bias of the included studies was high, with only three presenting an unclear or low rating. The meta-analysis shows the effect of MF on endurance performance was on average slightly negative (g = - 0.32, [95% CI - 0.46; - 0.18], p < 0.001). The multiple meta-regression showed no significant influences of the included features (i.e. age, sex, body mass index and physical fitness level) on MF-susceptibility.

CONCLUSIONS

The present review confirmed the negative impact of MF on endurance performance. However, no individual features influencing MF-susceptibility were identified. This can partially be explained by the multiple methodological limitations such as underreporting of participant characteristics, lack of standardization across studies, and the restricted inclusion of potentially relevant variables. Future research should include a rigorous description of multiple different individual features (e.g., performance level, diet, etc.) to further elucidate MF mechanisms.

Prior brain endurance training improves endurance exercise performance

Mental fatigue (MF) impairs endurance exercise performance. Brain endurance training (BET) describes the systematic repetition of mentally-fatiguing cognitive tasks designed to build resilience to MF and improve endurance performance. Evidence to date shows that mental training during physical training can benefit post-training exercise performance, however, this concurrent BET approach may not be practical for all settings. Therefore, the current study evaluated the effects of mental training before physical training (prior BET) on exercise performance. A randomised control trial design: pre-test, training (BET, control), post-test. During the pre-test and post-test sessions, participants performed a 5-min rhythmic handgrip task requiring the generation of as much force as possible, a 20-min 2-back working memory task, and another 5-min rhythmic handgrip task. Participants were randomly assigned to a BET (n = 12) or control group (n = 12). Both groups completed the same submaximal rhythmic handgrip training for five weeks (four sessions per week). The BET group also completed 20-min cognitive training (2-back working memory task, incongruent colour-word Stroop task) before each submaximal exercise training session. Endurance performance improved more (p < 0.05) following BET (24%) than physical training alone (12%). Compared to the control group, the BET group showed higher prefrontal oxygenation during the post-test exercise tasks (p < 0.05). Both groups were characterised by the same exertion, motivation, heart rate, and heart rate variability. Mental training before physical training improves endurance performance greater than physical training alone. The benefits of prior BET may be explained, at least in part, by improved prefrontal oxygenation. HighlightsThis study provides further evidence that brain endurance training (BET) improves performance over matched physical training.Prior BET (i.e. engaging in mentally demanding cognitive tasks before physical training) offers another option to enhance fatigue resilience, which expands the use of BET to more sports and potentially higher intensity training where concurrent BET will not be practical.The benefits of prior BET may be explained, at least in part, by improved prefrontal oxygenation.

Is the Cooling Vest an Ergogenic Tool for Physically Active Individuals? Assessment of Perceptual Response, Thermo-Physiological Behavior, and Sports Performance: A Systematic Review and Meta-Analysis

Exercise capacity is limited by environmental heat stress because thermoregulatory systems are altered and cannot prevent the elevation of body temperature due to a complex interplay of physiological, physical, and perceptual alterations. Cooling is an effective strategy to attenuate the temperature rise. Based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and the PEDro scale for assessing methodological quality, we systematically reviewed studies indexed in Medline, Web of Science, EMBASE, Science Direct, Sportdiscus, and Scopus, to evaluate the effects of the cooling vest (CVs) on perceptual response, physiological behavior, and sports performance in adult physical activity practitioners under heat stress conditions. Among the 711 studies identified in the search, 10 studies for the systematic review and eight for the meta-analysis met the inclusion and exclusion criteria. Overall, the use of CVs showed improvements in certain sports performance indicators, being significant (p < 0.05) in test time and substantial in peak power that could be influenced directly by the significant reduction (p < 0.05) in skin temperature and indirectly by the significant improvement (p < 0.05) in thermal and exertional perceptual responses, without the involvement of core temperature. In conclusion, the use of CVs is a cooling technique that influences perceptual response, thermo-physiological behavior, and sports performance. However, further studies are needed to elucidate the relevance of its application to CVs.

Fatigue and Human Performance: An Updated Framework

Fatigue has been defined differently in the literature depending on the field of research. The inconsistent use of the term fatigue complicated scientific communication, thereby limiting progress towards a more in-depth understanding of the phenomenon. Therefore, Enoka and Duchateau (Med Sci Sports Exerc 48:2228-38, 2016, [3]) proposed a fatigue framework that distinguishes between trait fatigue (i.e., fatigue experienced by an individual over a longer period of time) and motor or cognitive task-induced state fatigue (i.e., self-reported disabling symptom derived from the two interdependent attributes performance fatigability and perceived fatigability). Thereby, performance fatigability describes a decrease in an objective performance measure, while perceived fatigability refers to the sensations that regulate the integrity of the performer. Although this framework served as a good starting point to unravel the psychophysiology of fatigue, several important aspects were not included and the interdependence of the mechanisms driving performance fatigability and perceived fatigability were not comprehensively discussed. Therefore, the present narrative review aimed to (1) update the fatigue framework suggested by Enoka and Duchateau (Med Sci Sports Exerc 48:2228-38, 2016, [3]) pertaining the taxonomy (i.e., cognitive performance fatigue and perceived cognitive fatigue were added) and important determinants that were not considered previously (e.g., effort perception, affective valence, self-regulation), (2) discuss the mechanisms underlying performance fatigue and perceived fatigue in response to motor and cognitive tasks as well as their interdependence, and (3) provide recommendations for future research on these interactions. We propose to define motor or cognitive task-induced state fatigue as a psychophysiological condition characterized by a decrease in motor or cognitive performance (i.e., motor or cognitive performance fatigue, respectively) and/or an increased perception of fatigue (i.e., perceived motor or cognitive fatigue). These dimensions are interdependent, hinge on different determinants, and depend on body homeostasis (e.g., wakefulness, core temperature) as well as several modulating factors (e.g., age, sex, diseases, characteristics of the motor or cognitive task). Consequently, there is no single factor primarily determining performance fatigue and perceived fatigue in response to motor or cognitive tasks. Instead, the relative weight of each determinant and their interaction are modulated by several factors.

Altered motivation states for physical activity and 'appetite' for movement as compensatory mechanisms limiting the efficacy of exercise training for weight loss

Weight loss is a major motive for engaging in exercise, despite substantial evidence that exercise training results in compensatory responses that inhibit significant weight loss. According to the Laws of Thermodynamics and the CICO (Calories in, Calories out) model, increased exercise-induced energy expenditure (EE), in the absence of any compensatory increase in energy intake, should result in an energy deficit leading to reductions of body mass. However, the expected negative energy balance is met with both volitional and non-volitional (metabolic and behavioral) compensatory responses. A commonly reported compensatory response to exercise is increased food intake (i.e., Calories in) due to increased hunger, increased desire for certain foods, and/or changes in health beliefs. On the other side of the CICO model, exercise training can instigate compensatory reductions in EE that resist the maintenance of an energy deficit. This may be due to decreases in non-exercise activity thermogenesis (NEAT), increases in sedentary behavior, or alterations in sleep. Related to this EE compensation, the motivational states associated with the desire to be active tend to be overlooked when considering compensatory changes in non-exercise activity. For example, exercise-induced alterations in the wanting of physical activity could be a mechanism promoting compensatory reductions in EE. Thus, one's desires, urges or cravings for movement-also known as "motivation states" or "appetence for activity"-are thought to be proximal instigators of movement. Motivation states for activity may be influenced by genetic, metabolic, and psychological drives for activity (and inactivity), and such states are susceptible to fatigue-or reward-induced responses, which may account for reductions in NEAT in response to exercise training. Further, although the current data are limited, recent investigations have demonstrated that motivation states for physical activity are dampened by exercise and increase after periods of sedentarism. Collectively, this evidence points to additional compensatory mechanisms, associated with motivational states, by which impositions in exercise-induced changes in energy balance may be met with resistance, thus resulting in attenuated weight loss.

Competition Between Desired Competitive Result, Tolerable Homeostatic Disturbance, and Psychophysiological Interpretation Determines Pacing Strategy

Scientific interest in pacing goes back >100 years. Contemporary interest, both as a feature of athletic competition and as a window into understanding fatigue, goes back >30 years. Pacing represents the pattern of energy use designed to produce a competitive result while managing fatigue of different origins. Pacing has been studied both against the clock and during head-to-head competition. Several models have been used to explain pacing, including the teleoanticipation model, the central governor model, the anticipatory-feedback-rating of perceived exertion model, the concept of a learned template, the affordance concept, the integrative governor theory, and as an explanation for "falling behind." Early studies, mostly using time-trial exercise, focused on the need to manage homeostatic disturbance. More recent studies, based on head-to-head competition, have focused on an improved understanding of how psychophysiology, beyond the gestalt concept of rating of perceived exertion, can be understood as a mediator of pacing and as an explanation for falling behind. More recent approaches to pacing have focused on the elements of decision making during sport and have expanded the role of psychophysiological responses including sensory-discriminatory, affective-motivational, and cognitive-evaluative dimensions. These approaches have expanded the understanding of variations in pacing, particularly during head-to-head competition.

Perceived discomfort and neuromuscular fatigue during long-duration real driving with different car seats

INTRODUCTION

Identification of the seat features that could improve driving experience is a main issue for automotive companies.

OBJECTIVE

Long duration real driving sessions were performed to assess the effect of three seats (soft-S1, firm-S2 and suspended-S3) on perceived discomfort and neuromuscular fatigue (NMF).

MATERIALS & METHODS

For each seat, the muscular activity of bilateral Trapezius Descendens (TD), Erector Spinae (ES) and Multifidus (MF) muscles of twenty-one participants was recorded during real driving sessions of 3-hours each lasting approximately 3 hours and following the same itinerary. During each driving session, participants were also regularly asked to self-evaluate their level of whole-body and local discomfort. In addition, an endurance static test (EST) was performed before (ESTpre) and after (ESTpost) each driving session to assess the seat effect on physical capacity.

RESULTS

Whole-body discomfort increased with driving time for all seats, but this increase became significant latter for S3. The highest scores of local discomfort occurred for neck and lower back. Contrary to S1 and S2, the duration of ESTpost was not significantly lower compared to ESTpre with the S3. Interestingly, muscular activity of S1 remained stable throughout the driving task which could be attributed to sustained muscular contraction, while muscular recruitment adjustments occurred for S2 and S3 from 1H00 of driving. This muscular compensation concerns mostly the right side for S2 and S3 but with different profiles. On the left side, the muscular adjustments concern only the MF with S2 and the ES with S3.

CONCLUSION

Overall, our results demonstrated that S3 could be considered as the most suitable seat to delay discomfort and NMF appearance.

Network Physiology of Exercise: Beyond Molecular and Omics Perspectives

Molecular Exercise Physiology and Omics approaches represent an important step toward synthesis and integration, the original essence of Physiology. Despite the significant progress they have introduced in Exercise Physiology (EP), some of their theoretical and methodological assumptions are still limiting the understanding of the complexity of sport-related phenomena. Based on general principles of biological evolution and supported by complex network science, this paper aims to contrast theoretical and methodological aspects of molecular and network-based approaches to EP. After explaining the main EP challenges and why sport-related phenomena cannot be understood if reduced to the molecular level, the paper proposes some methodological research advances related to the type of studied variables and measures, the data acquisition techniques, the type of data analysis and the assumed relations among physiological levels. Inspired by Network Physiology, Network Physiology of Exercise provides a new paradigm and formalism to quantify cross-communication among diverse systems across levels and time scales to improve our understanding of exercise-related phenomena and opens new horizons for exercise testing in health and disease.

Cognitive tasks elicit mental fatigue and impair subsequent physical task endurance: Effects of task duration and type

Although mentally fatiguing cognitive tasks can impair subsequent physical endurance, the importance of cognitive task duration and the role of response inhibition remain unclear. This study compared the effects of a serial incongruent Stroop color-classification task (i.e., with response inhibition) and N-back memory updating task (i.e., without response inhibition) on mental fatigue and subsequent rhythmic handgrip exercise. Participants (N = 90) were randomly assigned to one of three cognitive task groups (Stroop, 2-back, control) and completed four 10-min blocks of one cognitive task followed by a 5-min physical endurance task (self-paced rhythmic handgrip exercise). Heart rate, heart rate variability, electromyographic forearm activity, and force were recorded throughout along with self-reported measures of fatigue, exertion, and motivation. From the start, the Stroop and 2-back tasks elicited higher heart rate and lower heart rate variability as well as greater fatigue, effort, and interest/enjoyment than the control task. From the second block onwards, the Stroop and 2-back groups produced less force than the control group. There were no group differences in forearm muscle activity. In sum, mental fatigue was induced after performing a cognitive task for 10 mins, whereas muscular endurance was impaired after performing a cognitive task for 20 mins. That these effects were observed for both types of cognitive task indicates that response inhibition is not a necessary condition. The cognitive task duration required to induce mental fatigue and impair rhythmic handgrip endurance performance lay between the durations reported previously for isometric (a few minutes) and whole-body (half an hour) endurance exercise.

Perceived Exertion: Revisiting the History and Updating the Neurophysiology and the Practical Applications

The perceived exertion construct creation is a landmark in exercise physiology and sport science. Obtaining perceived exertion is relatively easy, but practitioners often neglect some critical methodological issues in its assessment. Furthermore, the perceived exertion definition, neurophysiological basis, and practical applications have evolved since the perceived exertion construct's inception. Therefore, we revisit the careful work devoted by Gunnar Borg with psychophysical methods to develop the perceived exertion construct, which resulted in the creation of two scales: the rating of perceived exertion (RPE) and the category-ratio 10 (CR10). We discuss a contemporary definition that considers perceived exertion as a conscious perception of how hard, heavy, and strenuous the exercise is, according to the sense of effort to command the limbs and the feeling of heavy breathing (respiratory effort). Thus, other exercise-evoked sensations would not hinder the reported perceived exertion. We then describe the neurophysiological mechanisms involved in the perceived exertion genesis during exercise, including the influence of the peripheral feedback from the skeletal muscles and the cardiorespiratory system (i.e., afferent feedback) and the influence of efferent copies from the motor command and respiratory drive (i.e., corollary discharges), as well as the interaction between them. We highlight essential details practitioners should consider when using the RPE and CR10 scales, such as the perceived exertion definition, the original scales utilization, and the descriptors anchoring process. Finally, we present how practitioners can use perceived exertion to assess cardiorespiratory fitness, individualize exercise intensity prescription, predict endurance exercise performance, and monitor athletes' responses to physical training.

The soccer season: performance variations and evolutionary trends

The physiological demands of soccer challenge the entire spectrum of the response capacity of the biological systems and fitness requirements of the players. In this review we examined variations and evolutionary trends in body composition, neuromuscular and endurance-related parameters, as well as in game-related physical parameters of professional players. Further, we explore aspects relevant for training monitoring and we reference how different training stimulus and situational variables (e.g., competition exposure) affect the physiological and performance parameters of players. Generally, improvements of small magnitude in non- (non-CMJ) and countermovement-based jumps (CMJBased) and in the sprint acceleration (ACCPhase) and maximal velocity phase (MVPhase) are observed from start of preparation phase (PPS) to beginning of competition phase (BCP). A greater magnitude of increases is observed in physiological and endurance performance measures within this period; moderate magnitude in sub-maximal intensity exercise (velocity at fixed blood lactate concentrations; V2-4mmol/l) and large magnitude in VO2max, maximal aerobic speed (MAS) and intense intermittent exercise performance (IE). In the middle of competition phase (MCP), small (CMJBased and ACCPhase), moderate (non-CMJ; MVPhase; VO2max; sub-maximal exercise) and large (MAS and IE) improvements were observed compared to PPS. In the end of competition period (ECP), CMJBased and MVPhase improve to a small extent with non-CMJ, and ACCPhase, VO2max, MAS, sub-maximal intensity exercise and IE revealing moderate increments compared to PPS. Although less investigated, there are generally observed alterations of trivial magnitude in neuromuscular and endurance-related parameters between in-season assessments; only substantial alterations are examined for IE and sub-maximal exercise performance (decrease and increase of small magnitude, respectively) from BCP to MCP and in VO2max and IE (decrements of small magnitude) from MCP to ECP. Match performance may vary during the season. Although, the variability between studies is clear for TD, VHSR and sprint, all the studies observed substantial increments in HSR between MCP and ECP. Finally, studies examining evolutionary trends by means of exercise and competition performance measures suggests of a heightened importance of neuromuscular factors. In conclusion, during the preseason players "recover" body composition profile and neuromuscular and endurance competitive capacity. Within in-season, and more robustly towards ECP, alterations in neuromuscular performance seem to be force-velocity dependent, and in some cases, physiological determinants and endurance performance may be compromised when considering other in-season moments. Importantly, there is a substantial variability in team responses that can be observed during in-season. Consequently, this informs on the need to both provide a regular training stimulus and adequate monitorization throughout the season.

Prior Involvement of Central Motor Drive Does Not Impact Performance and Neuromuscular Fatigue in a Subsequent Endurance Task

PURPOSE

This study evaluated whether central motor drive during fatiguing exercise plays a role in determining performance and the development of neuromuscular fatigue during a subsequent endurance task.

METHODS

On separate days, 10 males completed three constant-load (80% peak power output), single-leg knee-extension trials to task failure in a randomized fashion. One trial was performed without preexisting quadriceps fatigue (CON), and two trials were performed with preexisting quadriceps fatigue induced either by voluntary (VOL; involving central motor drive) or electrically evoked (EVO; without central motor drive) quadriceps contractions (~20% maximal voluntary contraction (MVC)). Neuromuscular fatigue was assessed via pre-post changes in MVC, voluntary activation (VA), and quadriceps potentiated twitch force ( Qtw,pot ). Cardiorespiratory responses and rating of perceived exertion were also collected throughout the sessions. The two prefatiguing protocols were matched for peripheral fatigue and stopped when Qtw,pot declined by ~35%.

RESULTS

Time to exhaustion was shorter in EVO (4.3 ± 1.3 min) and VOL (4.7 ± 1.5 min) compared with CON (10.8 ± 3.6 min, P < 0.01) with no difference between EVO and VOL. ΔMVC (EVO: -47% ± 8%, VOL: -45% ± 8%, CON: -53% ± 8%), Δ Qtw,pot (EVO: -65% ± 7%, VOL: -59% ± 14%, CON: -64% ± 9%), and ΔVA (EVO: -9% ± 7%, VOL: -8% ± 5%, CON: -7% ± 5%) at the end of the dynamic task were not different between conditions (all P > 0.05). Compared with EVO (10.6 ± 1.7) and CON (6.8 ± 0.8), rating of perceived exertion was higher ( P = 0.05) at the beginning of VOL (12.2 ± 1.0).

CONCLUSIONS

These results suggest that central motor drive involvement during prior exercise plays a negligible role on the subsequent endurance performance. Therefore, our findings indicate that peripheral fatigue-mediated impairments are the primary determinants of high-intensity single-leg endurance performance.

Effectiveness of Nitrate Intake on Recovery from Exercise-Related Fatigue: A Systematic Review

BACKGROUND

Recovery between efforts is critical to achieving optimal physical and sports performance. In this sense, many nutritional supplements that have been proven to improve recovery and physical and physiological performance are widely used. Supplements such as nitrates (NO₃^-), including organic foods such as beets, promote muscle recovery and relieve fatigue. This study aimed to comprehensively summarise the available literature on the effect of NO₃^- consumption on exercise-related fatigue and muscle damage.

METHODS

A systematic search was carried out based on the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) using electronic databases (e.g., PubMed, Scopus, and Web of Science). From a total of 1634 studies identified, 15 studies were included in this review.

RESULTS

Based on the review, NO₃^- intake provokes physiological and metabolic responses that could potentially boost exercise-related recovery. NO₃^- could improve recovery indicators related to strength, pain, inflammation, and muscle damage.

CONCLUSIONS

Despite the relative proven effectiveness of NO₃^- on recovery after aerobic and anaerobic efforts, based on the heterogeneity of the procedures (e.g., dosage, chronic vs. acute intake, participants' characteristics, variables and outcomes), it could be premature to suggest its extended use in sports.

Influence of an Upper Limb Isometric Task in Perceived and Performance Fatigability of Elderly Subjects: A Quasi-Experimental Study

Isometric activity can be used as a strategy to improve health, fitness, and functional performance in the elderly population, but differences in fatigability may occur. This study aimed to understand fatigability behavior during an upper limb isometric task (ULIT) and the role of health status and physical activity in the fatigability of elderly participants. Thirty-two (32) elderly participants (72.5 ± 5.18 years) were instructed to perform ULIT. The Borg CR10 scale and task failure point (TTF) were used to measure perceived and performance fatigability. Self-reported measures were used to assess the quality of life and physical activity level. A significant relationship between perceived and performance fatigability was found only in the final phase of activity (p < 0.01). Significant correlations were found between perceived fatigability and the social functioning dimension (p < 0.05), and between performance fatigability (TTF) and BMI (p < 0.01), physical functioning (p < 0.01), and role functioning/physical (p < 0.05) dimensions. In conclusion, ULIT produces changes in fatigability of elderly people, which are positively related in the final stage of the activity. Changes in fatigability are negatively related to BMI. It is also negatively related to health, social functioning, physical functioning and role functioning/physical quality of life dimensions.

Predicting individual muscle fatigue tolerance by resting-state EEG brain network

OBJECTIVE

Exercise-induced muscle fatigue is a complex physiological phenomenon involving the central and peripheral nervous systems, and fatigue tolerance varies across individuals. Various studies have emphasized the close relationships between muscle fatigue and the brain. However, the relationships between the resting-state electroencephalogram (rsEEG) brain network and individual muscle fatigue tolerance remain unexplored.

APPROACH

Eighteen elite water polo athletes took part in our experiment. Five-minute before- and after-fatigue-exercise rsEEG and fatiguing task (i.e., elbow flexion and extension) electromyography (EMG) data were recorded. Based on the graph theory, we constructed the before- and after-task rsEEG coherence network and compared the network differences between them. Then, the correlation between the before-fatigue rsEEG network properties and the EMG fatigue indexes when a subject cannot keep on exercising anymore was profiled. Finally, a prediction model based on the before-fatigue rsEEG network properties was established to predict fatigue tolerance.

MAIN RESULTS

Results of this study revealed the significant differences between the before- and after-exercise rsEEG brain network and found significant high correlations between before-exercise rsEEG network properties in the beta band and individual muscle fatigue tolerance. Finally, an efficient support vector regression (SVR) model based on the before-exercise rsEEG network properties in the beta band was constructed and achieved the accurate prediction of individual fatigue tolerance. Similar results were also revealed on another thirty-subject swimmer data set further demonstrating the reliability of predicting fatigue tolerance based on the rsEEG network.

SIGNIFICANCE

Our study investigates the relationship between the rsEEG brain network and individual muscle fatigue tolerance and provides a potential objective physiological biomarker for tolerance prediction and the regulation of muscle fatigue.

Experimental study on the influence of mental fatigue on risk decision-making of miners

Mental fatigue increases risk-taking behavior. Using data collected between June 15 and August 6, 2020, this study investigates the impact of miners’ mental fatigue on risk decision-making to improve risk prevention and prediction abilities, and to reduce the occurrence of coal mine safety accidents. A total of 273 and 33 people participated in the preliminary and formal experiments, respectively. The participants, coal miners, visited a lab thrice to complete the pre-experiment, Balloon Analog Risk Task (BART), and Iowa Gambling Task (IGT). On the BART, mental fatigue displayed a significantly positive association with risk preference. On the IGT, as mental fatigue increased, net scores continuously decreased, while the frequency of making unfavorable decisions and the probability of taking risks increased. The BART value had no or weak correlations with the net score. Results suggest that mental fatigue leads to an increasing propensity to take risks. Therefore, regarding coal mine safety management, further attention is necessary concerning miners’ mental health, addressing mental fatigue, increasing rest time, and reducing night work. Furthermore, reasonable diet, improved working environments, and a positive attitude toward work should be promoted to reduce or eliminate mental fatigue and avoid decision-making errors that could cause accidents.

The evolution of human fatigue resistance

Humans differ from African great apes in numerous respects, but the chief initial difference setting hominins on their unique evolutionary trajectory was habitual bipedalism. The two most widely supported selective forces for this adaptation are increased efficiency of locomotion and improved ability to feed in upright contexts. By 4 million years ago, hominins had evolved the ability to walk long distances but extreme selection for endurance capabilities likely occurred later in the genus Homo to help them forage, power scavenge and persistence hunt in hot, arid conditions. In this review we explore the hypothesis that to be effective long-distance walkers and especially runners, there would also have been a strong selective benefit among Homo to resist fatigue. Our hypothesis is that since fatigue is an important factor that limits the ability to perform endurance-based activities, fatigue resistance was likely an important target for selection during human evolution for improved endurance capabilities. We review the trade-offs between strength, power, and stamina in apes and Homo and discuss three biological systems that we hypothesize humans evolved adaptations for fatigue resistance: neurological, metabolic and thermoregulatory. We conclude that the evolution of endurance at the cost of strength and power likely also involved the evolution of mechanisms to resist fatigue.

Non-invasive brain stimulation over the orbital prefrontal cortex maintains endurance performance in mentally fatigued swimmers

BACKGROUND

Using anodal transcranial direct current stimulation (a-tDCS) on frontal brain areas might be a promising strategy to mitigates mental fatigue and maintain endurance performance swimmers.

OBJECTIVE

The objective was to analyze the effect of a-tDCS over the orbital prefrontal cortex (oPFC) on endurance performance of mentally fatigued female amateur swimmer.

METHODS

Nineteen female amateur swimmers participated in this study. In two experimental visits, the swimmers completed the 3-min all-out tethered swimming after performing a 30-min Stroop test with a-tDCS or placebo (Sham) stimulation over the left-oPFC. The brain stimulation conditions (i.e., a-tDCS and Sham) were performed in a double-blinded and counterbalanced order.

RESULTS

It was found lower critical force, mean force, force minimum, fatigue index, and aerobic impulse for Sham than a-tDCS (p < 0.05). There was no main effect of condition for peak force (p >  0.05).

CONCLUSION

We concluded that a-tDCS applied over the left-oPFC in female amateur swimmers mentally fatigued maintained endurance performance. From a practical point of view, the use of a-tDCS should be considered to counteract harmful cognitive effects and maintain endurance performance during competitive race events.

Shorter constant work rate cycling tests as proxies for longer tests in highly trained cyclists

Severe-intensity constant work rate (CWR) cycling tests simulate the high-intensity competition environment and are useful for monitoring training progression and adaptation, yet impose significant physiological and psychological strain, require substantial recovery, and may disrupt athlete training or competition preparation. A brief, minimally fatiguing test providing comparable information is desirable. Purpose To determine whether physiological variables measured during, and functional decline in maximal power output immediately after, a 2-min CWR test can act as a proxy for 4-min test outcomes. Methods Physiological stress (V˙O2 kinetics, heart rate, blood lactate concentrations ([La^-]_b)) was monitored and performance fatigability was estimated (as pre-to-post-CWR changes in 10-s sprint power) during 2- and 4-min CWR tests in 16 high-level cyclists (V˙O2peak=64.4±6.0 ml∙kg^-1∙min^-1). The relationship between the 2- and 4-min CWR tests and the physiological variables that best relate to the performance fatigability were investigated. Results The 2-min CWR test evoked a smaller decline in sprint mechanical power (32% vs. 47%, p<0.001). Both the physiological variables (r = 0.66–0.96) and sprint mechanical power (r = 0.67–0.92) were independently and strongly correlated between 2- and 4-min tests. Differences in V˙O2peak and [La^-]_b in both CWR tests were strongly associated with the decline in sprint mechanical power. Conclusion Strong correlations between 2- and 4-min severe-intensity CWR test outcomes indicated that the shorter test can be used as a proxy for the longer test. A shorter test may be more practical within the elite performance environment due to lower physiological stress and performance fatigability and should have less impact on subsequent training and competition preparation.

Active vs. passive recovery during an aerobic interval training session in well-trained runners

Purpose

To compare cardio-metabolic, perceptual and neuromuscular responses to an aerobic interval training (AIT) running session, with active (AR) vs. passive recovery (PR).

Methods

Eleven well-trained male distance runners (36.63 ± 6.93 years, 59.26 ± 5.27 mL·kg⁻¹·min⁻¹, ⁓ 35 min in 10 km) completed the University of Montréal Track Test (UMTT) and 2 AIT sessions on track in random order, which consisted of 4 × 2 min at 100% of the maximum aerobic speed (MAS), with 2 min of AR at 80% of the velocity associated to the second ventilatory threshold (vVT₂), or no exercise (i.e., PR). During sessions, oxygen consumption (V̇O₂), heart rate (HR), blood lactate [La], rating of perceived exertion (RPE), and countermovement jump (CMJ) were continuously monitored.

Results

There were no differences in time spent in the “red zone” (i.e. > 90% V̇O_2max) between sessions (222 ± 73 s AR vs. 230 ± 104 s PR, p = 0.588), although the PR exhibited a greater time spent at peak V̇O₂ close to significance (117 ± 114 vs. 158 ± 109 s, p = 0.056). However, the AR elicited a higher mean V̇O₂ (49.62 ± 5.91 vs. 47.46 ± 4.20 mL·kg⁻¹·min⁻¹, p = 0.021). The AR favored a lower [La] after sessions (6.93 ± 2.22 vs. 6.24 ± 1.93 mmol·L⁻¹, p = 0.016) and a higher RPE during sessions (15 ± 0.45 vs. 14 ± 0.47, p = 0.045). Meanwhile, the CMJ was significantly potentiated during both sessions.

Conclusion

Considering that PR elicited lower perceptual loading for a similar cardiorespiratory response, its use would be preferable, at least, for this type of AIT running sessions.

A 32-day long fieldwork in Antarctica improves heat tolerance during physical exercise

We evaluated the influence of a 32-day camping in Antarctica on physical performance and exercise-induced thermoregulatory responses. In Brazil, before and after the Antarctic camping, the volunteers performed an incremental exercise at temperate conditions and, two days later, an exercise heat stress protocol (45-min running at 60% of maximum aerobic speed, at 31°C and 60% of relative humidity). In Antarctica, core temperature was assessed on a day of fieldwork, and average values higher than 38.5°C were reported. At pre- and post-Antarctica, physiological (whole-body and local sweat rate, number of active sweat glands, sweat gland output, core and skin temperatures) and perceptual (thermal comfort and sensation) variables were measured. The Antarctic camping improved the participants' performance and induced heat-related adaptations, as evidenced by sweat redistribution (lower in the chest but higher in grouped data from the forehead, forearm, and thigh) and reduced skin temperatures in the forehead and chest during the exercise heat stress protocol. Notwithstanding the acclimatization, the participants did not report differences of the thermal sensation and comfort. In conclusion, staying in an Antarctic camp for 32 days improved physical performance and elicited physiological adaptations to heat due to the physical exertion-induced hyperthermia in the field.

The relationship between running distance and coaches' perception of team performance in professional soccer player during multiple seasons

This study analyzed how the physical movement profile of soccer matches evolved throughout a season by assessing the variability of different metrics depending on the season phase. In addition, the evolution of running distances was investigated in the relation to the team performance based on the coaches’ perception. Games from four consecutives Spanish LaLiga seasons (n = 1520) were recorded using an optical tracking system (i.e., ChyronHego). Total distance (TD), distance covered between 14 and 21 km h⁻¹ (MIRD), 21–24 km h⁻¹ (HIRD), and > 24 km h⁻¹ (VHIRD) were analyzed, as well as the number of efforts between 21 and 24 km h⁻¹ (Sp21) and > 24 km h⁻¹ (Sp24). Seasons were divided into four phases (P): P1 (matches 1–10), P2 (11–19), P3 (20–29), and P4 (30–38). Linear mixed models revealed that soccer players covered significantly greater distances and completed a higher number of sprints in P2 and P3. Also, team performance evaluated by soccer coaches was positively related to TD, HIRD, VHIRD and Sp21 in P1. A negative relationship was observed between team performance and distance covered at speeds below 21 km h⁻¹ in P2 and P3. Team performance was negatively related to TD, MIRD, and HIRD, and Sp21 in P4. As conclusion, the team performance perceived by coaches is related to the movement profile throughout a season, and it significantly influences the evolution of soccer players’ movement profiles. Specifically, it seems that the players of the best teams have the best physical performance at the beginning of the season with respect to the rest of the phases.

Determinants of whole-body maximal aerobic performance in young male and female athletes: The roles of lower extremity muscle size, strength and power

This study sought to determine whether lower extremity muscle size, power and strength could be a determinant of whole-body maximal aerobic performance in athletes. 20 male and 19 female young athletes (18 ± 4 years) from various sporting disciplines participated in this study. All athletes performed a continuous ramp-incremental cycling to exhaustion for the determination of peak oxygen uptake (V˙O2peak: the highest V˙O2 over a 15-s period) and maximal power output (MPO: power output corresponding to V˙O2peak). Axial scanning of the right leg was performed with magnetic resonance imaging, and anatomical cross-sectional areas (CSAs) of quadriceps femoris (QF) and hamstring muscles at 50% of thigh length were measured. Moreover, bilateral leg extension power and unilateral isometric knee extension and flexion torque were determined. All variables were normalised to body mass, and six independent variables (V˙O2peak, CSAs of thigh muscles, leg extension power and knee extension and flexion torque) were entered into a forward stepwise multiple regression model with MPO being dependent variable for males and females separately. In the males, V˙O2peak was chosen as the single predictor of MPO explaining 78% of the variance. In the females, MPO was attributed to, in the order of importance, V˙O2peak (p < 0.001) and the CSA of QF (p = 0.011) accounting for 84% of the variance. This study suggests that while oxygen transport capacity is the main determinant of MPO regardless of sex, thigh muscle size also has a role in whole-body maximal aerobic performance in female athletes.

Effect of the subjective intensity of fatigue and interoception on perceptual regulation and performance during sustained physical activity

Background

The subjective experience of fatigue impairs an individual’s ability to sustain physical endurance performance. However, precise understanding of the specific role perceived fatigue plays in the central regulation of performance remains unclear. Here, we examined whether the subjective intensity of a perceived state of fatigue, pre-induced through prior upper body activity, differentially impacted performance and altered perceived effort and affect experienced during a sustained, isometric contraction in lower body. We also explored whether (cardiac) interoception predicted the intensity of experienced perceptual and affective responses and moderated the relationships between constructs during physical activity.

Methods

Using a repeated-measures study design, thirty male participants completed three experimental conditions, with the intensity of a pre-induced state of fatigue manipulated to evoke moderate (MOD), severe (SEV) and minimal (control; CON) intensity of perceptions prior to performance of the sustained contraction.

Results

Performance of the sustained contraction was significantly impaired under a perceived state of fatigue, with reductions of 10% and 14% observed in the MOD and SEV conditions, respectively. Performance impairment was accompanied by greater perceived effort and more negative affective valence reported during the contraction. However, effects were limited to comparisons to CON, with no difference evident between the two experimental trials (i.e. MOD vs. SEV). Individuals’ awareness of their accuracy in judging resting heartbeats was shown to predict the subjective intensity of fatigue experienced during the endurance task. However, interoception did not moderate the relationships evident between fatigue and both perceived effort and affective valence.

Conclusions

A perceived state of fatigue limits endurance performance, influencing both how effortful activity is perceived to be and the affective experience of activity. Though awareness of interoceptive representations of bodily states may be important to the subjective experience of fatigue, interoception does not modulate the relationships between perceived fatigue and other perceptual (i.e. effort) and affective constructs.

Advances in modeling learning and decision-making in neuroscience

An organism's survival depends on its ability to learn about its environment and to make adaptive decisions in the service of achieving the best possible outcomes in that environment. To study the neural circuits that support these functions, researchers have increasingly relied on models that formalize the computations required to carry them out. Here, we review the recent history of computational modeling of learning and decision-making, and how these models have been used to advance understanding of prefrontal cortex function. We discuss how such models have advanced from their origins in basic algorithms of updating and action selection to increasingly account for complexities in the cognitive processes required for learning and decision-making, and the representations over which they operate. We further discuss how a deeper understanding of the real-world complexities in these computations has shed light on the fundamental constraints on optimal behavior, and on the complex interactions between corticostriatal pathways to determine such behavior. The continuing and rapid development of these models holds great promise for understanding the mechanisms by which animals adapt to their environments, and what leads to maladaptive forms of learning and decision-making within clinical populations.

Review article: The aetiology of fatigue in inflammatory bowel disease and potential therapeutic management strategies

BACKGROUND

Fatigue is the inability to achieve or maintain an expected work output resulting from central or peripheral mechanisms. The prevalence of inflammatory bowel disease (IBD) fatigue can reach 86% in active disease, persisting in 50%-52% of patients with mild to inactive disease. Fatigue is the commonest reason for work absence in IBD, and patients often report fatigue burden to be greater than that of primary disease symptoms. Relatively few evidence-based treatment options exist, and the aetiology is poorly understood.

AIM

To review the available data and suggest a possible aetiology of IBD fatigue and to consider the efficacy of existing management strategies and highlight potential future interventions.

METHODS

We reviewed fatigue-related literature in IBD using PubMed database.

RESULTS

Disease related factors such as inflammation and pharmacological treatments negatively impact skeletal muscle and brain physiology, likely contributing to fatigue symptoms. Secondary factors such as malnutrition, anaemia, sleep disturbance and psychological comorbidity are potential determinants. Immune profile, faecal microbiota composition and physical fitness differ significantly between fatigued and non-fatigued patients, suggesting these may be aetiological factors. Solution-focused therapy, high-dosage thiamine supplementation and biological therapy may reduce fatigue perception in IBD. The effect of physical activity interventions is inconclusive.

CONCLUSIONS

A multimodal approach is likely required to treat IBD fatigue. Established reversible factors like anaemia, micronutrient deficiencies and active disease should initially be resolved. Psychosocial intervention shows potential efficacy in reducing fatigue perception in quiescent disease. Restoring physical deconditioning by exercise training intervention may further improve fatigue burden.

Functional reserve and sex differences during exercise to exhaustion revealed by post-exercise ischaemia and repeated supramaximal exercise

KEY POINTS

Females have lower fatigability than males during single limb isometric and dynamic contractions, but whether sex-differences exist during high-intensity whole-body exercise remains unknown. This study shows that males and females respond similarly to repeated supramaximal whole-body exercise, and that at task failure a large functional reserve remains in both sexes. Using post-exercise ischaemia with repeated exercise, we have shown that this functional reserve depends on the glycolytic component of substrate-level phosphorylation and is almost identical in both sexes. Metaboreflex activation during post-exercise ischaemia and the O₂ debt per kg of active lean mass are also similar in males and females after supramaximal exercise. Females have a greater capacity to extract oxygen during repeated supramaximal exercise and reach lower P ETC O 2 , experiencing a larger drop in brain oxygenation than males, without apparent negative repercussion on performance. Females had no faster recovery of performance after accounting for sex differences in lean mass.

ABSTRACT

The purpose of this study was to ascertain what mechanisms explain sex differences at task failure and to determine whether males and females have a functional reserve at exhaustion. Exercise performance, cardiorespiratory variables, oxygen deficit, and brain and muscle oxygenation were determined in 18 males and 18 females (21-36 years old) in two sessions consisting of three bouts of constant-power exercise at 120% of V ̇ O 2 max until exhaustion interspaced by 20 s recovery periods. In one of the two sessions, the circulation of both legs was occluded instantaneously (300 mmHg) during the recovery periods. Females had a higher muscle O₂ extraction during fatiguing supramaximal exercise than males. Metaboreflex activation, and lean mass-adjusted O₂ deficit and debt were similar in males and females. Compared to males, females reached lower P ETC O 2 and brain oxygenation during supramaximal exercise, without apparent negative consequences on performance. After the occlusions, males and females were able to restart exercising at 120% of V ̇ O 2 max , revealing a similar functional reserve, which depends on glycolytic component of substrate-level phosphorylation and its rate of utilization. After ischaemia, muscle O₂ extraction was increased, and muscle V ̇ O 2 was similarly reduced in males and females. The physiological response to repeated supramaximal exercise to exhaustion is remarkably similar in males and females when differences in lean mass are considered. Both sexes fatigue with a large functional reserve, which depends on the glycolytic energy supply, yet females have higher oxygen extraction capacity, but reduced P ETC O 2 and brain oxygenation.

The Theory of Effort Minimization in Physical Activity

Although the automatic attraction to effort minimization has been evidenced in multiple fields, its potential role in explaining the pandemic of physical inactivity has been overlooked. The theory of effort minimization in physical activity (TEMPA) fills this gap. TEMPA seeks to obtain a more accurate understanding of the neuropsychological determinants of movement-based behaviors.

Exercising muscle mass influences neuromuscular, cardiorespiratory, and perceptual responses during and following ramp-incremental cycling to task failure

Neuromuscular (NM), cardiorespiratory, and perceptual responses to maximal-graded exercise using different amounts of active muscle mass remain unclear. We hypothesized that during dynamic exercise, peripheral NM fatigue (declined twitch force) and muscle pain would be greater using smaller muscle mass, whereas central fatigue (declined voluntary activation) and ventilatory variables would be greater using larger muscle mass. Twelve males (29.8 ± 4.7 years) performed two ramp-incremental cycling tests until task failure: 1) single-leg (SL) with 10 W·min^-1 ramp and 2) double-leg (DL) with 20 W·min^-1 ramp. NM fatigue was assessed at baseline, task failure (post), and after 1, 4, and 8 min of recovery. Cardiorespiratory and perceptual variables [i.e., ratings of perceived exertion (RPE), pain, and dyspnea] were measured throughout cycling. Exercise duration was similar between sessions (SL: 857.7 ± 263.6 s; DL: 855.0 ± 218.8 s; P = 0.923), and higher absolute peak power output was attained in DL (SL: 163.2 ± 43.8 W; DL: 307.0 ± 72.0 W; P < 0.001). Although central fatigue did not differ between conditions (SL: -6.6 ± 6.5%; DL: -3.5 ± 4.8%; P = 0.091), maximal voluntary contraction (SL: -41.6 ± 10.9%; DL: -33.7 ± 8.5%; P = 0.032) and single twitch forces (SL: -59.4 ± 18.8%; DL: -46.2 ± 16.2%; P = 0.003) declined more following SL. DL elicited higher peak oxygen uptake (SL: 42.1 ± 10.0 mL·kg^-1·min^-1; DL: 50.3 ± 9.3 mL·kg^-1·min^-1; P < 0.001), ventilation (SL: 137.1 ± 38.1 L·min^-1; DL: 171.5 ± 33.2 L·min^-1; P < 0.001), and heart rate (SL: 167 ± 21 bpm; DL: 187 ± 8 bpm; P = 0.005). Dyspnea (P = 0.025) was higher in DL; however, RPE (P = 0.005) and pain (P < 0.001) were higher in SL. These results suggest that interplay between NM, cardiorespiratory, and perceptual determinants of exercise performance during ramp-incremental cycling to task failure is muscle mass dependent.

Chronic Ingestion of Bicarbonate-Rich Water Improves Anaerobic Performance in Hypohydrated Elite Judo Athletes: A Pilot Study

In combat sports, anaerobic power and anaerobic capacity determine sport performance and the dominant metabolic pathways. The decline in performance during exercise that is attributed to the cumulative effects of fatigue, including excessive accumulation of metabolites, depletion of energy substrates, and water and electrolyte disturbances, seems to be of greatest significance. In our experiment, we evaluated the effectiveness of three weeks of bicarbonate-rich water ingestion on anaerobic performance in a state of hydration and dehydration in elite judo athletes. Eight male, elite judo athletes participated in two single-blind, repeated-measures trials. They were assigned to two hydration protocols, ingesting low mineralized table water and bicarbonate-rich water. Anaerobic performance was evaluated by two 30 s Wingate tests for lower and upper limbs, respectively, under conditions of hydration as well as exercise-induced dehydration. Resting, post-ingestion, and post-exercise concentrations of bicarbonate (HCO₃), urine osmolality (U_OSM), urine specific gravity (U_GRAV), and lactate (La) were measured. The current investigation assessed two related factors that impair anaerobic performance-hypohydration and buffering capacity. High-bicarbonate water ingestion improved buffering capacity, and we demonstrated the potential role of this mechanism and its phenomenon in masking the adverse effects of dehydration in the context of repeated high-intensity anaerobic exercise (HIAE).

Aerodynamic analysis of uphill drafting in cycling

Some teams aiming for victory in a mountain stage in cycling take control in the uphill sections of the stage. While drafting, the team imposes a high speed at the front of the peloton defending their team leader from opponent’s attacks. Drafting is a well-known strategy on flat or descending sections and has been studied before in this context. However, there are no systematic and extensive studies in the scientific literature on the aerodynamic effect of uphill drafting. Some studies even suggested that for gradients above 7.2% the speeds drop to 17 km/h and the air resistance can be neglected. In this paper, uphill drafting is analyzed and quantified by means of drag reductions and power reductions obtained by computational fluid dynamics simulations validated with wind tunnel measurements. It is shown that even for gradients above 7.2%, drafting can yield substantial benefits. Drafting allows cyclists to save over 7% of power on a slope of 7.5% at a speed of 6 m/s. At a speed of 8 m/s, this reduction can exceed 16%. Sensitivity analyses indicate that significant power savings can be achieved, also with varying bicycle, cyclist, road and environmental characteristics.

Reliability of an adapted core strength endurance test battery in individuals with axial spondylarthritis

OBJECTIVES

To adapt the core strength endurance test battery (aCSE), previously used for testing athletes, to a target group of patients with axial spondylarthritis (axSpA), to evaluate its intra-tester reliability and its associations with disease-specific factors.

METHODS

A cross-sectional study was conducted at axSpA exercise therapy groups, including both axSpA patients and the physiotherapist group leaders (PTs). The aCSE was used to measure the isometric strength endurance of the ventral, lateral, and dorsal core muscle chains (measured in seconds), as well as to assess the disease-specific factors of functional status, self-reported pain, and perceived strength performance. The aCSE was repeated after 7-14 days to measure intra-tester reliability for the same rater (PT group leader). Reliability was calculated as an intra-class correlation coefficient (ICC) using a nested design. The associations between ventral, lateral, and dorsal strength endurance and the disease-specific factors were calculated using Pearson correlation coefficients.

RESULTS

Study participants were 13 PT group leaders and 62 axSpA patients. The latter were all capable of performing the aCSE, with the exception of one individual. A moderate to substantial intra-rater reliability (ICCs (95%CI)) was found for the ventral (0.54 (0.35, 0.74)), lateral (0.52 (0.33, 0.70)), and dorsal (0.71 (0.58, 0.86)) core muscle chains. None of the aCSE measures correlated with the disease-specific factors.

CONCLUSION

The aCSE was found to be a reliable test battery for assessing core strength endurance in axSpA patients. Interestingly, aCSE performance was not associated with any disease-specific factors. Key Points • The adapted core strength endurance test battery measures the isometric strength of the ventral, lateral and dorsal core muscle chains. • The adapted core strength endurance test battery showed a moderate to substantial intra-rater reliability for all three muscle chains tested in axSpA patients. • No correlations were found between the adapted core strength endurance test battery and the disease-specific factors of self-reported pain, functional status and perceived strength performance.