Induction Of Fatigue Research Articles

Effects of previous carbohydrate supplementation on muscular fatigue: double-blind, randomized, placebo-controlled crossover study

Abstract AIMS The aim of this study was to examine the effects of previous carbohydrate supplementation on high-volume resistance exercise performance METHODS Twenty males physically independent adults aged ≥18 years participated in a double-blind randomized placebo-controlled crossover study. Sixty minutes before the experimental protocol, each participant ingested 0,6 g.kg of body mass-1 of carbohydrate supplementation or placebo. Maximum voluntary isometric contraction tests were performed before and after the dynamic fatigue induction protocol consisting of 10 sets of 8 repetitions of right leg knee extensors at 120o s-1. RESULTS Lower decrement of the isometric peak torque (p<0,001) and of the rate of torque development (p<0,001) was observed in carbohydrate supplementation after the dynamic protocol. Both concentric and eccentric peak torque differed significantly (p<0,001) between carbohydrate supplementation and placebo treatments from the second set, although the slope of the force-repetitions curve was not different between them. Additionally, the carbohydrate supplementation resulted in a lower session rating of perceived exertion (p<0,05). CONCLUSIONS Previous carbohydrate supplementation attenuates muscle fatigue and internal load exercise in a high-volume isokinetic leg protocol.

PO-056 Endocannabinoid CB1 receptor-mediated abnormal enhancement of rat corticostriatal glutamatergic pathway participates in exercise fatigue Regulation

Objective By monitoring the expression of CB1 receptor protein and key regulatory protein RGS4 in the endocannabinoid system (eCBs), and the changes in the transmission efficiency of Corticostriatal glutamatergic pathway and movement ability after microinjection of CB1 receptor agonist WIN 55212-2 into the lateral ventricles in rats, this study investigates the possible mechanism of striatal eCBs regulation of exercise fatigue. The results may provide experimental basis for further improving the theory of exercise fatigue and indicate new targets for the regulation of exercise fatigue.&#x0D; Methods 74 adult male Wistar rats were randomly divided into control group (Control) and 1-day fatigue group (1 FG), 3-day fatigue group (3FG) and 7-day fatigue group (7FG) after 3 days rearing. The Control group was in a quiet state and the exercise fatigue group performed exhaustive exercise for 1 day, 3 days and 7 days, respectively. After the induction of exercise fatigue, the expression of CB1 receptor and RGS4 in rat striatum was determined by Western blotting technique. WIN 55212-2 (2mM,5μL) microinjection into the lateral ventricle plus the stimulation-induced electrophysiological technique was used to determine the effect of CB1 receptor activation on the evoked spike discharges in striatal MSNs . &#x0D; Results （1）The results of Western blotting showed that there was no significant change in the expression of CB1 receptor and RGS4 protein in the striatum of rats in 1FG compared with Control group (P＞0.05). But the expression of CB1 receptor and RGS4 in the striatum was significantly increased in both FG and 7FG compared with Control group(P＜0.01).&#x0D; （2）The results of stimulation-induced electrophysiological experiment plus microinjection of lateral ventricle showed that the evoked spike frequency of MSNs in striatum of Control group (2.35±0.66Hz) at 1h after injection of WIN55N212-2 was not significantly different from that before injection (2.43±0.49Hz) (P＞0.05), that the evoked discharge frequency of MSNs in striatum of rats in 1FG（2.63±0.54Hz）was decreased at 10～20min after injection of WIN55N212-2（2.16±0.43Hz）, but no significant difference was found (P＞0.05), that the evoked discharge frequency of MSNs in the striatum of rats in 3FG was decreased at 10～20min after injection of WIN55N212-2（2.16±0.43Hz）, that the evoked discharge frequency of MSNs in the striatum of 3FG（10.57±2.12Hz）was significantly decreased at 10～20min（7.05±1.84Hz）after injection (P＜0.01), and it was basically restored to the pre-injection level by the time of 50～60min injection（10.47±2.83Hz）, and that the evoked discharge frequency of MSNs in the striatum of 7FG（21.7±3.28Hz）was significantly decreased at 10～20min after injection（15.14±1.94Hz）(P＜0.01), and it was basically recovered at 50～60min after injection (19.12±2.89Hz) (P＞0.05).&#x0D; （3）The experimental results of exercise fatigue showed that the time of exercise to fatigue in 7FG group after microinjection of WIN 55-212-2 in lateral ventricle （138.91±8.76min）was significantly longer than that in artificial cerebrospinal fluid (aCSF) group（127.51±9.45min）(P＜0.05), the time of exercise to fatigue in the 1FG group (105.33±8.99min) was not significantly different from that in the aCSF injection group (105.59±10.34min)（P＞0.05）, the time of exercise to fatigue in 3FG group(118.16±7.99min) was longer than that in aCSF injection group (107.5±10.31min), but there was no statistical significance（P＞0.05）.&#x0D; Conclusions Exercise-induced fatigue could increase the expression of CB1 receptor protein and key regulatory protein RGS4 in the striatum and decrease the function of eCBs , which mediated the abnormal enhancement of the transmission efficiency of the corticostriatal glutamatergic pathway and participated in the central regulation of exercise-induced fatigue, and showed an obvious fatigue accumulating effect. The enhancement of the function of eCBs in the striatum of exercise fatigue rats could inhibit the transmission efficiency of rat corticostriatal glutamatergic pathway, and to a certain extent played a role in delaying exercise fatigue. Striatal eCBs may be a new target for central regulation of exercise fatigue.

Effect of foam roller, kinesiotaping and dynamic stretching on gait parameters with induced ankle muscle fatigue

Objective: The purpose of this study was to investigate the effects of foam roller (FR) stretching, kinesiotaping (KT), and dynamic stretching (DS) on gait parameters after inducing muscle fatigue in the ankle joint. Design: Cross-sectional study. Methods: The subjects were thirty healthy young adults between the ages of 20 and 31 years at Baekseok University who voluntarily participated in this study. The participants were randomly assigned to either the FR group, KT group, or the DS group after inducing muscle fatigue of the ankle joint. Fatigue induction of the ankle joint muscles was performed by alternating a heel up and down exercise with the standing posture on the ground. The speed was maintained at 40 beats/minute using a metronome. Subsequently, the respective intervention was applied to each group. Gait parameters were measured before and after ankle muscle fatigue induction, and after intervention using the GAITRite system. One-way ANOVA was used to compare gait parameters among groups, while repeated measures ANOVA was used to compare gait parameters within each intervention group. Results: The FR group increased significantly in velocity, step length, and stride length except for cadence after intervention compared to after ankle muscle fatigue induction (p<0.01). Furthermore, the KT group showed significant increases in velocity, cadence, step length, and stride length after intervention, especially in cadence group (p<0.05). All intervention groups showed significant increases in stride length after intervention, especially the DS group (p<0.05). Conclusions: Therefore, we suggest that KT, FR, and DS can be an effective intervention on gait parameters when the ankle joint is unstable and injured.

Administration of low-level laser on muscles of mastication following the induction of initial fatigue: protocol for a randomized, controlled, clinical trial.

Background:Orofacial pain encompasses painful conditions, such as temporomandibular disorder (TMD). Multidisciplinary health teams seek to control such musculoskeletal disorders to improve the quality and functional capacity of the muscles of mastication. The aim of the proposed study is to evaluate the effect of low-level laser therapy as a form of treatment for the prevention of initial fatigue of the muscles of mastication (masseter and anterior temporal muscles) as well as the recovery of these muscles after induced exhaustion (caused by isometric contraction) in young adults.Methods:The participants will be 78 healthy male and female volunteers between 18 and 34 years of age. The volunteers will be randomly allocated to a laser group (n = 26), sham group (n = 26), and control group (n = 26). All participants will be submitted to a clinical evaluation to record mandibular movements, bite force, muscle sensitivity to palpation, and initial muscle fatigue. Initial fatigue will be induced by isometric contraction of the jaws. Maximum voluntary contraction will be performed to record the time until initial exhaustion of the masseter muscle (determined by electromyography). The groups will then be submitted to the interventions: active laser therapy (wavelength: 780 nm; fluence: 134 J/cm2; power: 50 mW; irradiance: 1.675 W/cm2; exposure time: 80 seconds per point) on 3 points of the masseter and 1 point on the anterior temporal muscles on each side; sham laser (placebo effect); or no intervention (control). Maximum voluntary contraction will be performed again after the interventions to record the time until initial exhaustion of the masseter muscle (determined by electromyography). Differences in individual time until exhaustion between the pre- and postintervention evaluations will be measured to determine the effect of low-level laser therapy.Discussion:Although studies have been made with the use of low-level laser therapy in TMDs and on the effect of photobiomodulation on fatigue, this the first study to test this therapy in the prevention of fatigue in this region. The clinical relevance lies in the fact that longer dental procedures could take place if the patients are less prone to fatigue.

Effect of Phototherapy on Masseter and Anterior Temporal Muscles Before Induction of Fatigue: A Randomized, Sham-Controlled, Blind Clinical Trial.

This is a randomized, sham-controlled, blind clinical trial that aimed to evaluate the effect of phototherapy on bite force, mandibular range of motion, sensitivity to palpation, and fatigue in the masseter and anterior temporal muscles of young patients when administered before the induction of fatigue. Fifty-two healthy volunteers aged 18-23 years were randomly allocated to a laser group and sham group. Both groups were submitted to a clinical evaluation to record mandibular range of motion, bite force, muscle sensitivity to palpation, and muscle fatigue. The laser group was then submitted to phototherapy (780 nm, 25 J/cm2, 50 mW, 20 sec, and 1 J per point) on three points of the masseter and one point of the anterior temporal muscle on each side. The sham group was submitted to the same procedure, but with the device switched off. The volunteers were then instructed to chew two pieces of gum (one on each side) for 6 min, with the pace set by a metronome calibrated to 80 bpm, followed by the reevaluation of all variables. The results were submitted to t-test and Wilcoxon test. A significance level of 5% (p < 0.05) was considered in all analyses. No statistically significant intergroup or intragroup differences were found for the variables analyzed. With the proposed protocol, phototherapy administered before the induction of fatigue did not lead to any changes in bite force and mandibular range of motion, indicating that further studies are needed with different phototherapy dosimetric parameters.

Respiratory Muscle Fatigue Limits Upper‐Body Exercise Tolerance in Collegiate Cross‐Country Skiers

The development of respiratory muscle fatigue compromises lower‐body exercise performed to the limit of tolerance, especially in endurance athletes. It is unclear if respiratory muscle fatigue has a similar effect on upper‐body exercise tolerance where respiratory muscles have important respiratory, postural, and locomotor roles. The purpose of this study was to evaluate the effects of inspiratory muscle fatigue on upper‐body exercise tolerance. I hypothesized that high‐intensity arm cranking performed by upper‐body endurance trained athletes would induce considerable ventilator stress and reduce upper‐body exercise tolerance. Seven male Division I collegiate cross‐country skiers (20 ± 2 yrs, 183 ± 6 cm, 76 ± 6 kg, upper‐body VO2peak and Wpeak 50 ± 5 mL/kg/min, 197 ± 24 W, respectively) performed two upper‐body exercise trials. For the control exercise trial (CON‐EX), athletes performed arm‐cranking at ~85% of Wpeak (170 ± 20 W) until their limit of tolerance. For the inspiratory muscle fatigue exercise trial (IMF‐EX), athletes performed the same task while having pre‐existing fatigue in their inspiratory muscles (~20% reduction in maximal inspiratory pressure) induced through a threshold resistance breathing device. Physiological responses and the limit of tolerance were compared between trials. During CON‐EX, ventilatory demand was high as indicated by the high ventilation rates (137 ± 17 L/min). After CON‐EX, MIP decreased by 10 ± 8% (158 ± 30 vs. 136 ± 26 cm H2O) and remained reduced by 7 ± 7% for 11 min (P &lt; 0.05). Compared to CON‐EX, IMF‐EX limit of tolerance decreased by 33 ± 14% (14.2 ± 2.4 vs. 9.6 ± 2.7 min, P &lt; 0.01). During IMF‐EX, ventilation, breathing frequency, perceived exertion, and dyspnea increased whereas tidal volume decreased (all P &lt; 0.05). For these collegiate cross‐country skiers, high‐intensity arm‐cranking taxed their respiratory muscles and impaired their inspiratory muscle function. Further, artificial induction of inspiratory muscle fatigue decreased limit of tolerance and increased perceptual stress. Collectively, our results demonstrate the functional consequences of inspiratory muscle fatigue on upper‐body performances. Our findings of increased ventilatory stress and reduced upper‐body exercise tolerance in athletes who regularly performed upper‐body endurance exercise contrasts previous upper‐body research using untrained individuals. Thus, further research is needed to explore the impact of respiratory muscle fatigue has on upper‐body performance and the mechanisms behind it. These findings have implications for athletes performing upper‐body exercise, researchers, and clinicians who use arm‐cranking as an exercise and/or rehabilitation modality.Support or Funding InformationThis study was supported by the Portage Health Foundation, Michigan Space Grant Consortium, and American Physiology Society.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Influence of authoritarianism, vagal tone and mental fatigue on obedience to authority

ABSTRACTRecent research suggests that obedience in the Milgram paradigm is underpinned by stress vulnerability and inhibitory control over pain sharing. Because self-regulatory fatigue (SRF) induction is a suited method to investigate the influence of inhibitory control on behaviour, participants (n = 99) were randomly assigned to a High vs. Low self-regulatory condition. Heart rate variability (HRV, a biomarker of stress vulnerability) was collected during 5-min baseline and continuously during the experimental procedure. Prior to the experiment, participants completed an online survey assessing right-wing authoritarianism (RWA), a well-known predictor of obedience. Using the Immersive Video Milgram Obedience Experiment, we found (i) that lower resting HRV predicted higher destructive obedience, (ii) that low self-regulatory inhibition (induced by fatigue) reduced destructive obedience, (iii) that the well-established influence of RWA on destructive obedience was suppressed in the presence of SRF. Implications for future directions in obedience research are discussed.

The Future and the Will: Planning requires self-control, and ego depletion leads to planning aversion

Planning is a future-directed thought process that is highly beneficial, but it requires mental effort. Informed by the strength model of self-regulation, four studies (N = 546) tested the hypothesis that willingness to plan is linked to good self-control. A correlational study (N = 201) found that people high in trait self-control had done more planning than other people and also intended to make more plans during the upcoming week. A laboratory experiment (N = 105) induced a state of ego depletion (i.e., impaired self-control) by having some participants continuously break pre-established motoric habits, and afterward these participants were less willing to make plans for the next four weeks than control participants. A field experiment (N = 112) used a naturally occurring induction of decision fatigue (IKEA shopping) and again found that ego depletion reduced planning. Specifically, fatigued shoppers exiting the store expressed more reluctance to make long-term plans than shoppers who were just arriving at the store. A final laboratory experiment (N = 128) found that ego-depleted participants were only half as likely to choose a planning task as control participants, and identified effort avoidance as a mediator mechanism. Crucially, the three experimental manipulations were longer and stronger than the 5-min depletion tasks often used in previous research (24 min; 2 h; 30 min), and manipulation checks confirmed severe and significant ego depletion. Depletion had no effects on aspirational goals or the desire to relax. We conclude that wants and desires come easily, while planning requires mental work akin to self-control. Theoretical and methodological implications are discussed.

Mental Fatigue Impairs Physical Performance in Young Swimmers.

This study aimed to investigate the impact of mental fatigue on heart rate variability, subjective measures of fatigue, and swimming performance in young athletes. Sixteen swimmers [15.45 (0.51) y old, 7.35 (2.20) y of swimming experience] performeda 1500-m time trial on 2 occasions separated by an interval of at least 72hours. The 1500-m swimming was preceded by a 30-minute treatment that consisted of performing the Stroop Color and Word test to induce mental fatigue (experimental trial) or watching an emotionally neutral video (control trial). Participants reported higher ratings of mental fatigue and mental effort following the Stroop test when compared with the control trial, but no differences in motivation were observed. The induction of mental fatigue impaired swimming performance, as evidenced by a slower time (1.2%) to complete the 1500-m trial. No intertrial differences were identified for rating of perceived exertion during the swimming test or in heart rate variability after the Stroop and swimming tests. The results indicate that induction of mental fatigue impairs 1500-m swimming performance without changing heart rate variability.

Optimization of Design Parameters of Bellows Using Taguchi Method

Bellows is one of the key sections in the expansion joint and has the ability to assimilate uniform and non-uniform expansion and contraction of the system. Bellows require high quality and incredible adaptability which can be accomplished by extraordinary design and fitting assembling methodology. Expansion joints are made to work in the elastic stress range. This may lead to induction of fatigue in bellows after a limited number of development cycles. The main objective of this paper is to find the optimal level of parameters and develop a regression model for the output variable. Taguchi’s L16 orthogonal array is applied for reducing the number of runs and time for experiment. Statistical techniques analysis of variance (ANOVA), signal-to-noise (S/N) ratio, graphical main effect and interaction plots have been used to study the effects of various parameters on the number of cycles. The optimum parametric condition is obtained using the Taguchi method.

Does photobiomodulation therapy is better than cryotherapy in muscle recovery after a high-intensity exercise? A randomized, double-blind, placebo-controlled clinical trial.

This study aimed to determine the effectiveness of photobiomodulation therapy (PBMT) and cryotherapy, in isolated and combined forms, as muscle recovery techniques after muscle fatigue-inducing protocol. Forty volunteers were randomly divided into five groups: a placebo group (PG); a PBMT group (PBMT); a cryotherapy group (CG); a cryotherapy-PBMT group (CPG); and a PBMT-cryotherapy group (PCG). All subjects performed four sessions at 24-h intervals, during which they submitted to isometric assessment (MVC) and blood collection in the pre-exercise period, and 5 and 60min post-exercise, while the muscle fatigue induction protocol occurred after the pre-exercise collections. In the remaining sessions performed 24, 48, and 72h later, only blood collections and MVCs were performed. A single treatment with PBMT and/or cryotherapy was applied after only 2min of completing the post-5-min MVC test at the first session. In the intragroup comparison, it was found that exercise led to a significant decrease (p < 0.05) in the production of MVC in all groups. Comparing the results of MVCs between groups, we observed significant increases in the MVC capacity of the PBMT, CPG, and PCG volunteers in comparison with both PG and CG (p < 0.05). We observed a significant decrease in the concentrations of the biochemical markers of oxidative damage (TBARS and PC) in all groups and muscle damage (creatine kinase-CK) in the PBMT, PCG, and CPG compared with the PG (p < 0.01). The clinical impact of these findings is clear because they demonstrate that the use of phototherapy is more effective than the use of cryotherapy for muscle recovery, additionally cryotherapy decreases PBMT efficacy.

Effects of Kinesio&lt;sup&gt;®&lt;/sup&gt; Taping on Dynamic Balance Following Fatigue: a Randomized Controlled Trial

The objective of the study was to determine the effects of Kinesio taping (KT) in inhibiting fatigue and preserving dynamic balance. Male recreational athletes were recruited to participate in this study. Participants were blinded from the group assignment and divided into four groups (Group A; KT and fatigue, Group B; no tape and fatigue, Group C; KT and no fatigue and Group D; no tape and no fatigue) using sequentially opaque, sealed envelopes. Pre and post measurements of Modified Star Excursion Balance Test (SEBT) composite score and normalized reach distance were used to measure dynamic balance. Adapted Functional Agility Short Term Fatigue Protocol (FAST-FP) was used to induce fatigue. KT was applied to rectus femoris, biceps femoris and medial gastrocnemius of the dominant leg. There was a significant change in the SEBT composite score between groups over time (p<0.05) and in time effect (p<0.05). The main effect comparing the SEBT composite score between the group was not significant (p=0.16). Group A (90.10±9.40) and Group B (86.14±10.50) attained lower mean for SEBT composite score compared to Group C (97.30±10.83) and Group D (98.13±9.47) suggests that fatigue have a diminishing effect on dynamic balance. KT application inhibit the effects of fatigue and preserved lateral and posterior direction of SEBT. KT application may lower the risk for injuries in the lateral and posterior directions following fatigue induction.

Effects of visual fatigue caused by smartphones on balance function in healthy adults.

[Purpose] The purpose of this study was to determine the effects of visual fatigue caused by smartphone use on balance function. [Subjects and Methods] The participants consisted of 22 healthy male and female adults. Their postural stability, limit of stability, and limit of stability running time were evaluated using a computerized posturography apparatus before and after inducing visual fatigue. Postural stability and the limit of stability were divided into static and dynamic conditions. [Results] There were significant differences between the dynamic postural stability, the static and dynamic limit of stability, and both the static and dynamic limit of stability running times after the induction of visual fatigue. [Conclusion] The results showed that visual fatigue caused by smartphone use has a negative effect on balance function. Therefore, reducing visual fatigue through proper rest is necessary.

Effects of caffeine ingestion on endurance performance in mentally fatigued individuals.

To examine the effects of caffeine ingestion on physiological and perceptual responses in mentally fatigued individuals. Eight male physically active subjects completed four cycling constant-workload tests in four experimental conditions at 80% of maximal power output: control (C), mental fatigue (MF), mental fatigue plus caffeine ingestion (5mg/kg) (MF-CAF), and mental fatigue plus placebo (MF-PLA). The mental fatigue was induced by a continuous performance task A-X version (AX-CPT). Before and after the AX-CPT, the profile of mood state (POMS) and blood samples for lactate measurement were collected. Oxygen consumption ([Formula: see text]), rating of perceived exertion (RPE), and electromyography (EMG) activity were measured during the cycling test. The time to exhaustion in C, MF, MF-PLA, and MF-CAF were 251±30, 222±23, 248±28, and 285±42s, respectively. Delta values (corrected by C condition) were higher in MF-CAF than MF (P=0.031). MF-CAF reported higher Vigor scores when compared with C (P=0.046) and MF (P=0.020). RPE at the first minute was significantly higher in MF-PLA than in C (P=0.050); at the second minute, RPE was higher in MF-PLA than in C (P=0.049) and MF-CAF (P=0.048). EMG activity was not different between the conditions. Caffeine ingestion increased approximately 14% endurance performance after the induction of mental fatigue. This effect was accompanied by a tendency to improvement in mood state (i.e., vigor). Therefore, caffeine ingestion can promote a beneficial effect on endurance performance in mentally fatigued individuals.

The Impact of Automation Reliability and Operator Fatigue on Performance and Reliance

Reliability of automation is known to influence operator reliance on automation. What is less understood is how the influence of reliability and the effects of operator fatigue might interact. The present study investigated the impact of automation reliability on accuracy and reliance and how this impact changes with level of fatigue during simulated multiple unmanned aerial vehicle (UAV) operation. Participants ( N = 131) completed a two-hour simulated multi-UAV mission assisted by an automated decision making aid of either high or low reliability. A decrease in subjective task engagement and performance over time marked the induction of passive fatigue by the mission. Participants were more trusting in the high reliability condition than in the low reliability condition. Finally, reliance decreased with time at any reliability, but a significant interaction between reliability and time on task indicated that the decrease was of smaller magnitude when the automation was reliable.

Effects of Fatigue Induction on Ground Reaction Force Components, Postural Stability, and Vertical Jump Performance in Taekwondo Athletes

Objective: The purpose of this study was to investigate the effect of fatigue induction on ground reactionforce (GRF) components, postural stability, and vertical jump performance in Taekwondo athletes.Method: Ten Taekwondo athletes (5 men, 5 women; mean age, 22.30 ± 2.62 years; mean height, 174.21 ±9.20 cm; mean body weight, 67.28 ± 12.56 kg) participated in this study. Fatigue was induced by a shortperiod of strenuous exercise performed on a motorized treadmill. The analyzed variables included verticaljump performance, static stability (mediolateral [ML], center of pressure [COP], anteroposterior [AP] COP,ΔCOPx, ΔCOPy, and COP area), postural stability index values (ML stability index [MLSI], AP stability index[APSI], vertical stability index [VSI], dynamic postural stability index [DPSI]), and GRF components (MLforce, AP force, peak vertical force [PVF], and loading rate). To analyze the variables measured in this study,PASW version 22.0 was used to calculate the mean and standard deviation, while a paired t-test was usedto evaluate the pre- versus post-fatigue results. Pearson``s correlation coefficients among variables were alsoanalyzed. The statistical significance level was set at α = .05.Results: Vertical jump performance decreased significantly after the induction of fatigue, while AP COP,ΔCOPx, COP area, APSI, VSI, and DPSI increased significantly. PVF and loading rate increased significantlyafter the induction of fatigue, while the postural stability variables (AP COP, ΔCOPy, COP area, APSI, VSI,DPSI) were similarly correlated with GRF components (PVF, loading rate) after fatigue was achieved (r= .600, R2 = 37%).Conclusion: These results suggest that the induction of fatigue can decrease postural stability and exerciseperformance of Taekwondo athletes during training and competition sessions.

EFFECTS OF KINESIO® TAPING ON DYNAMIC POSTURAL CONTROL FOLLOWING FATIGUE INDUCTION

This study aimed to determine the effects of Kinesio® taping (KT) on dynamic postural control following fatigue induction. It is hypothesized that the application of KT limits the effects of fatigue on dynamic postural control. This study used a randomized controlled trial recruited 32 male recreational athletes, randomized to one of the two groups (Group A: KT and fatigue and Group B: KT and no fatigue). Fatigue was induced using the adapted Functional Agility Short Term Fatigue Protocol (FAST-FP). The rectus femoris of quadriceps, biceps femoris of the hamstring and medial gastrocnemius of the dominant leg were taped. The dynamic postural control was assessed pre and post fatigue. A significant interaction was observed between the group and time for the anterior-posterior position (p=0.03, ηp2=0.21) while non-significant interaction was observed in the lateral symmetry (p=0.84, ηp2=0.001). A significant main effect of time was observed for anterior-posterior position (p&gt;0.05, ηp2=0.15) while non-significant for the lateral symmetry (p=0.65, ηp2=0.007). For the main effect of the two groups was not significant for the anterior-posterior position (p=0.42, ηp2=0.02) and lateral symmetry (p=0.73, ηp2=0.004). In conclusion, the diminishing effect of fatigue on the anterior-posterior position was observed. Moreover, KT application does not limit the effects of fatigue on the dynamic postural control.

Pre-exercise LED phototherapy (638 nm) prevents grip strength loss in elderly women: A double-blind randomized controlled trial

BACKGROUND: LED phototherapy can attenuate muscle fatigue and accelerate muscle recovery in young persons, but little is known about photobiomodulation effects on muscle strength in the elderly. OBJECTIVE: To assess the effects of LED phototherapy on the grip strength and muscle fatigue of wrist flexors in elderly women. METHODS: Twenty-nine women were recruited and allocated to Placebo Group (PG) (n = 14) and LED Group (LG) (n = 15). Grip strength, number of resisted wrist flexion repetitions, and serum creatine kinase (CK) were measured. The subjects were irradiated with one diode (638 nm, 150 mW, 11.7 J/cm 2 , 4.5 J/point) at four points on the wrist flexor muscles, and fatigue was induced by exercise using 75% of one maximum repetition (1MR). When muscle fatigue was reached, grip strength and CK were reassessed. RESULTS: In the LG, there was no intra-group difference for grip strength (N), 217.7 ± 34.3 to 209.9 ± 35.3 (p = 0.063) whereas in the PG, there was decrease in strength from 203.0 ± 22.5 to 181.4 ± 21.6 ( p< 0.001). LED increased the number of repetitions by 22.0%. An increase in CK (U/L) was observed in PG in all post-fatigue periods (p = 0.003) but no difference was found in the LG (p = 0.972). CONCLUSIONS: A single application of LED before muscle fatigue induction may effectively maintain grip strength and reduce muscle fatigue and damage.

Neural mechanisms underlying the impact of daylong cognitive work on economic decisions

The ability to exert self-control is key to social insertion and professional success. An influential literature in psychology has developed the theory that self-control relies on a limited common resource, so that fatigue effects might carry over from one task to the next. However, the biological nature of the putative limited resource and the existence of carry-over effects have been matters of considerable controversy. Here, we targeted the activity of the lateral prefrontal cortex (LPFC) as a common substrate for cognitive control, and we prolonged the time scale of fatigue induction by an order of magnitude. Participants performed executive control tasks known to recruit the LPFC (working memory and task-switching) over more than 6 h (an approximate workday). Fatigue effects were probed regularly by measuring impulsivity in intertemporal choices, i.e., the propensity to favor immediate rewards, which has been found to increase under LPFC inhibition. Behavioral data showed that choice impulsivity increased in a group of participants who performed hard versions of executive tasks but not in control groups who performed easy versions or enjoyed some leisure time. Functional MRI data acquired at the start, middle, and end of the day confirmed that enhancement of choice impulsivity was related to a specific decrease in the activity of an LPFC region (in the left middle frontal gyrus) that was recruited by both executive and choice tasks. Our findings demonstrate a concept of focused neural fatigue that might be naturally induced in real-life situations and have important repercussions on economic decisions.

Sex differences in cardiovascular demands of refereeing during international basketball competition

ABSTRACTObjectives: The aim of this study was to investigate the impact of sex on cardiovascular responses of referees during elite international basketball competition.Methods: Twenty-seven elite referees (9 female; 18 male) officiated a random sample of 18 matches during the final round of the 2013 Women’s Eurobasket Championship. Continuous recordings of referees’ heart rate (HR) during matches were obtained and analyzed for average HR, relative exercise intensity (% maximum HR, HRmax) and proportion of time spent within different exercise-intensity categories.Results: During the championship, the average match HR was >150 bpm and approximated an exercise intensity of >85% HRmax for referees. Female referees exhibited lower average match HR (156.8 ± 10.2 vs. 163.6 ± 11.6 bpm, p<0.05) and exercise intensity (86.2 ± 5.5 vs. 89.5 ± 6.0% HRmax, p<0.05) compared to male referees. Referees spent most (>70%) of each match at a HR intensity of 70-89% HRmax with females experiencing more match time within the 55-69% HRmax category compared to males. Average HR and exercise intensity was greatest for all referees during the early part of the match (Quarter 1) that declined over the match.Conclusion: This study has demonstrated that sex significantly influences cardiovascular responses for elite basketball referees with lower responses for females potentially reflective of different movement patterns. Reductions in cardiovascular response noted during matches for all referees may reflect alterations in metabolism, match activities or induction of fatigue that should be considered in the development and training of elite referees for optimal match performance.