Subjective Perception Of Fatigue Research Articles

Neuromuscular and perceptual-cognitive response to 4v4 small-sided game in youth soccer players.

The physical and psychological load of small-sided games (SSGs) can affect players' neuromuscular and cognitive functions. Yet, little is known about the acute performance changes after such a specific exercise in young soccer players and their association with exercise load applied. This study investigates i) the neuromuscular and perceptual-cognitive response to the SSG exercise load, and ii) the relationship between pre- and post-SSG changes in variables of performance and the respective exercise load in youth soccer players. Sixteen participants (13.6 ± 0.5years) underwent a 30-min SSG 4v4 + GK protocol. Prior to and after the SSG they performed countermovement jump (CMJ), planned and reactive Y-shaped agility tests (PA, RA), and go/no-go task (GNG). Their subjective perception of fatigue was evaluated by visual analog scale. Fatigue induced by SSG (perception of fatigue increased by 41.56%, p = .001, g = 4.15) increased PA time (4.04%, p = .002, g = .97), RA time (6.45%, p = .003, g = 1.16), and number of errors in the response inhibition task (87.1%, p = .023, rc = .57), whilst decreased CMJ height (-6.65%, p = .014, g = .56). These performance deteriorations were not significantly associated with neither internal nor external load variables. However, a less pronounced drop in performance was related to external load variables, i.e., ∆CMJ height and ∆RA time correlated with very high-speed running (rs = .66, p = .006; rs = -.50, p = .022; respectively) and maximal speed (r = .54, p = .032; r = -.52, p = .037; respectively), whilst ∆PA time was associated with high-intensity accelerations (rs = -.76, p = .002). These findings indicate that fatigue induced by SSG affects both planned and reactive agility, decision-making in response inhibition task, and explosive strength in youth soccer players regardless of significant contribution of any robust internal or external load variables. Nonetheless, high-intensity actions within SSG partially compensate for the decrements in their agility performance and explosive strength. The load variables encountered during SSG do not fully reflect youth players' neuromuscular and perceptual-cognitive responses to sport-specific exercise.

Simulating Flight Crew Workload Settings to Mitigate Fatigue Risk in Flight Operations

In flight operations, the workload settings refer to the shift work, duty time, flight time, number of sectors, rest periods, time of day, duty patterns, number of time-zone transitions, number of consecutive duty days, and changes in the schedule. Workload factors, together with the biological mechanisms (the circadian rhythm, homeostatic sleep pressure, sleep inertia), can lead to the appearance of fatigue. Fatigue affects numerous tasks, such as performing inaccurate flight procedures, missing radio calls, missing or being too slow to pick up system warnings, forgetting or performing routine tasks inaccurately, and others. The focus of this paper is to determine which flight crew workload settings elements impact the appearance of fatigue. The process of collecting data regarding flight crew workload settings and fatigue is conducted on a sample of four airline pilots using an electronic CRD system of standardized chronometric cognitive tests and subjective self-assessment scales. Causal modeling tools of the IBM SPSS Statistics were used to detect correlations among flight crew workload settings, indicators of the subjective perception of fatigue, and measured fatigue indicators. In the final step, a set of simulations was created using simulation tools of the IBM SPSS Statistics to show how modifications of flight crew workload settings, such as modified duty time, number of days off, and others, can impact the level of fatigue. The obtained results can help improve the future planning of flight crew workload set-up and mitigate or prevent the appearance of fatigue in flight operations.

Correlations among Fatigue Indicators, Subjective Perception of Fatigue, and Workload Settings in Flight Operations

Conducting flight operations at the pace of air traffic relies on shift work, overtime work, work at night, work in different and numerous time zones, and unbalanced flight crew schedules. Such working hours and workload settings can cause disturbances of the circadian rhythm and sleep disorders among flight crew members; this can result in fatigue and can have an impact on the safety of flight operations. Fatigue impacts many cognitive abilities such as vigilance, memory, spatial orientation, learning, problem solving, and decision making. In aviation, fatigue has been identified as a hazard to the safety of flight operations. This paper describes objectivation methods for data collecting processes regarding flight crew fatigue, using an electronic system of standardized chronometric cognitive tests and subjective self-assessment surveys on the subjective perception of fatigue. The data collected were analyzed using statistical methods to identify and quantify elements that affect the appearance of fatigue. Finally, causal modeling methods were used to determine correlations among the measured flight crew fatigue indicators, the subjective perception of fatigue, and the defined workload settings. The results of this research reveal which elements strongly impact flight crew fatigue. The detected correlations can help define improved measures for the mitigation of fatigue risk in future flight operations.

Effect of Mental Task on Sex Differences in Muscle Fatigability: A Review.

Previous research demonstrated that there are observable sex differences in developing muscle fatigue when mental task during fatiguing activity is present; however, there is no available review on this matter. Therefore, this review aimed to summarize the findings of previous studies investigating the effect of mental task on muscle fatigue in men and women. To conduct the review, we utilized searches using the electronic databases Web of Science, PubMed, Scopus, and EBSCO Cinahl Ultimate. The studies included had no limited publication date and examined the effects of mental task on muscle fatigue in a healthy adult population of any age. The evaluation was performed using the following criteria: time to failure, or subjective scale in various modifications (visual analog scale—VAS, rate of perceived effort—RPE, rate of perceived fatigue—RPF, rate of perceived discomfort—RPD). A total of seven studies met the set criteria, which were subsequently analyzed. Heavy mental task (more demanding math tasks) can reduce the time to failure for both men and women, with the reduction being more pronounced for women than for men. For light mental task (simple math tasks), no reduction in time to failure was observed to a great extent. The mental task in any of the included studies did not affect the subjective perception of fatigue, effort, discomfort, or pain. Although the studies investigating the effect of mental task on sex differences in muscle fatigability are limited, based on our findings we can assume that in jobs requiring heavier mental task, women may be more prone to the faster development of muscle fatigue; thus, employers might consider paying attention to the possibility of adequate rest.

The fatigue illusion: the physical effects of mindlessness

Attitudes that are blindly adopted, termed premature cognitive commitments, can place unnecessary limitations on how we perceive and engage in the world around us, including how we perceive fatigue. Fatigue is still widely treated as a somatic reaction, caused by physical limitations. In contrast to this, our hypothesis, based on Langer’s mind/body unity theory, states that people perceive fatigue at proportional milestones during a task, regardless of how long it is, how strenuous it is, or whether it is physical or cognitive, and that fatigue can be manipulated psychologically. Five studies were designed to investigate (a) whether or not proportional perceptions of fatigue, or fatigue milestones, exists, rendering fatigue an illusion and (b) whether perceptions of fatigue are malleable by way of Langerian mindfulness, offering individuals control in the management of fatigue. Study 1 introduced a fatigue scale and used retrospective perceptions about travel-fatigue. Study 2 added an objective measure of physical fatigue in a cognitive task. Study 3 tested the illusion of fatigue on an athlete population in a physical task. Study 4 included the Langer Mindfulness Scale to further study subjective perceptions of fatigue in physical tasks. Study 5 tested mindful interventions on fatigue. The findings indicate that (a) an illusion of fatigue exists, with proportional set-in and peak milestones, what we label the fatigue illusion and (b) constructs of Langerian mindfulness offer individuals control over the timing, amount, and even the experience of fatigue.

The Effect of Music Tempo on Fatigue Perception at Different Exercise Intensities.

Background: This study aimed to clarify the effect of music tempo on runners’ perception of fatigue at different exercise intensities and while listening to music of different tempos through running experiments. Methods: This study used a within-subject two-factor experimental design with music tempo (fast music, slow music, no music) and exercise intensity (high intensity, low intensity) as independent variables and the time to fatigue perception (TFP), the difference in heart rate (HR) and the difference in the median frequency (MF) of surface electromyography (sEMG) signals as observation indexes. Eighteen participants completed a total of 108 sets of running experiments. Results: (1) The main effect of music tempo on the TFP was significant (p < 0.001). (2) The main effect of exercise intensity on the TFP was significant (p < 0.001), and the main effect on the difference in HR was significant (p < 0.001). (3) The interaction effect of music tempo and exercise intensity on the TFP was significant (p < 0.05). Conclusions: Exercisers’ subjective perception of fatigue was affected by music tempo and the interaction between music tempo and exercise intensity, and exercisers’ objective fatigue perception was influenced mostly by exercise intensity. The findings of this study provide guidance for runners’ choice of music at different intensities of exercise. Whether it is low-intensity exercise or high-intensity exercise, listening to fast music while exercising can help runners perform better mentally and physically during their runs.

Prevention of work-related stress, fatigue, loss of cognitive function, improved attention and recovery of stamina with Robuvit® in professionals with increased oxidative stress.

The aim of this open, pilot supplement registry study was to evaluate the protective, preventive effects of Robuvit® on professional-related fatigue symptoms and on aspects of cognitive functions, professional attitudes and decision-making in healthy nurses under professional stress and with increased oxidative stress. In total, 40 subjects, aged 30-37, completed the 4-week registry study. A control group of 20 subjects used only the standard management (SM) and one group of 20 subjects took 300 mg Robuvit® in addition. Safety and tolerability of Robuvit® were optimal. The two registry groups were comparable at inclusion. The overall scores of the real daily life and tasks questionnaire after 4 weeks were significantly higher in the Robuvit® group (P<0.05) as compared to controls. It increased from 4.3±0.4 at baseline to 6.78±0.8 after 4 weeks of Robuvit® intake and from 4.2±0.5 to 5.12±1.0 in the control group. The supplementation significantly improved the subjective perception of fatigue in comparison with controls (P<0.05). A practical professional score evaluation provided an indication of professional attitude and stamina, in difficult, stressful working conditions under continuous pressure. The results showed that after 4-week supplementation, all assessed parameters improved significantly and the difference with controls was statistically significant (P<0.05). Furthermore, oxidative stress as plasma free radicals decreased significantly in the Robuvit® group (P<0.05) but not in the control group. Robuvit® supplementation appears to improve most symptoms related to work-induced fatigue, stress and cognitive function and supports stamina. Further evaluations need to be planned according to the concept of this pilot registry in a field that requires more attention.

Work fatigue and attention performance in remise and taxi drivers

Fatigue is considered a risk factor in traffic accidents, particularly in the case of professional drivers. In this population, extended working hours constitute one of the main precursors of fatigue. The objective of this work was to study the subjective perception of fatigue and the attentional performance in taxi / remise drivers at the beginning and end of a work day. Professional drivers (n = 30) were compared with a group of workers from different sectors (n = 30), matched by gender and age. A Fatigue severity scale, an Analogue visual fatigue scale, and a Conjunctive visual search task were administered. Overall, professional drivers showed higher scores in the fatigue severity scale. With regard to the attentional task, the ANOVA showed that professional drivers were less accurate in their performance. The practical implications of these findings are discussed.

Non-targeted metabolomics analyses by mass spectrometry to explore metabolic stress after six training weeks in high level swimmers.

ABSTRACT The objective was to compare the metabolic responses of high-level national swimmers to threshold or polarised training. 22 swimmers (n = 12 males and 10 females) participated in a 28-week cross-over intervention study consisting of 2 × 6 period weeks of training. Swimmers were assigned randomly to either training group for the first period: polarised (POL) (81% in energetic zone 1: blood lactate [La]b ≤ 2 mmol.L−1; 4% in zone 2: 2 mmol.L−1 <[La]b ≤ 4 mmol.L−1; 15% in zone 3: [La]b > 4 mmol.L−1) or threshold (THR) (65%/25%/10%). Before and after each training period, urine samples were collected for non-targeted metabolomics analysis. Mixed model analysis was performed on metabolomics data including fatigue class factors and/or training and/or interaction. Ion intensities of 6-keto-decanoylcarnitine (+31%), pregnanediol-3-glucuronide (+81%), P-cresol sulphate (+18%) were higher in the threshold group (P < 0.05) indicating higher glycogenic depletion and inflammation without alteration of the neuroendocrine stress axis. 4-phenylbutanic acid sulphate was 200% higher in less fatigued swimmers (P < 0.01) linking the anti-inflammatory activity at the cell membrane level to the subjective perception of fatigue. This research suggests the importance of replenishing glycogen stores and reducing inflammation during high thresholds training loads.

Thirst perception exacerbates objective mental fatigue

Thirst is represented within the anterior cingulate and insular cortices, and may share some common neuroanatomical structures that are implicated with the regulation of mental fatigue. This novel study investigated whether thirst might modulate the subjective, behavioural, or neurophysiological representations of mental fatigue. In a crossover design, thirst was monitored in 15 males during 60 min of cycling in normothermic conditions. Participants either consumed water to the dictates of their thirst (sated), or fluid was withheld and replaced with periodic salt water mouth rinses (thirst). Following either satiety or thirst, a 60 min modified Stroop task was completed to evoke mental fatigue. Prefrontal cortex (PFC) haemodynamics were monitored throughout the prolonged task, and subjective perceptions of fatigue were reported through a visual analogue scale. Behavioural performance was quantified as the total number of Stroop task iterations completed in the mentally fatiguing task, and by collating response time and accuracy into the inverse efficiency score (IES) for each 5 min interval throughout the task. During thirst, fewer iterations were completed and poorer IES performance was evident toward the latter portion of the mentally fatiguing task. Compensatory elevations in PFC oxyhaemoglobin were produced in each condition, however, differed temporally, and were premature during thirst. A diminished capacity to sustain cognitive performance is likely the product of an inability to preserve the distribution of resources within the prefrontal cortex, due to heightened activation about thirst regulatory centres. These data provide novel insight into the relationship between thirst and mental fatigue, and suggest that drinking to the dictates of thirst may be a pertinent strategy to sustain prolonged cognitive performance.

Effect of pre-game photobiomodulation on muscle recovery in professional soccer players: study protocol for a randomized, cross-over, sham-controlled, triple-blind, clinical trial

Background: Photobiomodulation with low-level laser therapy (LLLT) has been widely used in clinical practice for diverse purposes, such as modulation of the inflammatory process, acceleration of the tissue repair process, pain relief and the enhancement of post-exercise recovery. Studies have demonstrated a beneficial interaction between photobiomodulation and the production of creatine kinase, with a reduction in the release of this marker of muscle damage when laser and/or LEDs is administered prior to high-intensity physical activity. Objective: The aim of the proposed study is to determine the influence of pre-exercise phototherapy on post-exercise muscle recovery. Methods: A randomized, cross-over, sham-controlled, double-blind, clinical trial is proposed. The participants will be healthy professional soccer players aged 15 to 20 years from the same team with a body mass index within the ideal range (20 to 25 kg/m2 ) and no history of lower limb musculoskeletal injuries or surgery or back surgery in the previous six months. The athletes will be allocated to two groups based on the previously calculated sample size and will be blinded to allocation. Creatine kinase will be measured and the subjective perception of fatigue will be determined for each participant. The volunteers will then be randomly allocated to Group A, which will receive active phototherapy, and Group B, which will receive sham phototherapy. The athletes will undergo reevaluations immediately after as well as 48 hours after a football match. The data will be submitted to statistical analysis and the level of significance will be set to 5%. This study is registered with Clinical Trials under protocol number: NCT03416998.

A Head-to-Head Comparison of an Isometric and a Concentric Fatigability Protocol and the Association With Fatigue and Walking in Persons With Multiple Sclerosis

Background. Fatigue is one of the most frequent symptoms in persons with multiple sclerosis (MS). Distinction is made between subjective perceptions of fatigue and objective measures of fatigability. Fatigability can be measured by different protocols. Yet no studies have compared isometric and concentric contraction protocols of the lower extremities head-to-head. Therefore, the purpose of the present study was to (1) compare 2 such protocols head-to-head and (2) to investigate the association between fatigability evoked by the 2 protocols and measures of fatigue and walking. Methods. A total of 45 patients with MS had their walking capacity measured objectively by the 6-minute walk test (6MWT) and subjectively by the 12-item Multiple Sclerosis Walking Scale (MSWS-12). Fatigue was measured by the Modified Fatigue Impact Scale (MFIS) and fatigability by 2 knee extension protocols: sustained isometric and concentric. Results. The sustained isometric protocol induced a higher degree of fatigability than the concentric protocol (P < .01). Regression analyses revealed that sustained isometric fatigability was not associated with either measures of fatigue or walking (all r2 = 0.00; P = .85-.99), whereas the concentric protocol was significantly associated with fatigue (r2 = 0.20; P < .01), 6MWT (r2 = 0.09; P < .05), and MSWS-12 (r2 = 0.16; P < .01). Furthermore, after adjusting for maximal strength and sex, concentric fatigability remained a strong and significant predictor of fatigue (β = 0.49) and walking (6MWT: β = −0.26; MSWS: β = 0.37). Conclusion. This study provides the first evidence that a lower-extremity concentric fatigability protocol provides superior reflection of both fatigue and walking when compared with a sustained isometric protocol. We suggest that concentric protocols should be the focus of future studies investigating fatigability.

Relationship between biomechanical and psychophysiological indicators and performance in a vertical mountain race

In order to know the relationship between biomechanical and psychophysiological indicators, as well as the possible pre-post psychophysiological differences and the use of poles in the uphill performance on mountain runners, we performed a prospective and descriptive study of one vertical mountain race. Thus, it was analysed biomechanical (speed and strength/power manifestations) and psychophysiological variables (lactate, heart rate and subjective perception of fatigue) with a total of nine (n = 9) experienced runners divided into groups to use (n = 4) or not (n = 5) poles during the race. Nonparametric analyses were performed to observe the correlations between variables, the differences between groups and the differences between the psychophysiological values before and after the test. The results do not present significant (p &lt; 0.05) differences or correlations of performance between those that used poles or not. There are significant differences between the psychophysiological variables pre and post, in addition they show correlations of performance (final time and relation of time with the first classified) with higher mean and maximum heart rate, as well as a lower lactate accumulation. It is concluded that a better performance in a mountain vertical race is associated to higher physiological efficiency but not to greater strength and power jump manifestations in trained runners.

Experimental principal component analysis of fatigue in cyclists who have taken an oral L-tryptophan supplement

BackgroundSince the 1980s the role of tryptophan in modulating fatigue has been the subject of debate. According to some models, tryptophan delays the onset of fatigue. Conversely, in other models, this amino acid is implicated in generating fatigue. This study attempts to shed some light on the debate. MethodTen elite (non-professional) road racing cyclists took part in a double-blind study employing paired data under standardised dietary and training conditions. Each volunteer did two trials, one with tryptophan supplementation (TRP) and the other with placebo (PLB). Various body fuel, plasma amino acid and renal function parameters were analysed in relation to fatigue data obtained using the Borg test. Blood pressure, pupil size and haematocrit values were also monitored. The parameters obtained were used to examine the principal components of fatigue in said test. ObjectiveTo confirm that, under test conditions, oral L-tryptophan supplementation has a favourable influence on fatigue perception during exercise. ResultsThe principal components of fatigue, as reflected by the Borg test in this study, fit the following model: Perception of fatigue attained=8.406050586+(0.126275247*% load intensity)−(0.031521537*cholesterol mg/dl)+(0.051002322*HDL cholesterol mg/dl)−(0.017130681*tryptophan mmol/ml)−(0.004545865*glycinemmol/ml)+(0.082894085*methioninemmol/ml). (Multiple correlation coefficient=0.90; coefficient of determination R2=0.82; adjusted R2=0.81; standard error: 1.82; observations: 75). Renal functionUrea: (TRP: 45.6±6.5mg/dl vs. PLB: 44.1±5.7; p<0.4); creatinine: (TRP: 90.4±12.0 vs. PLB: 88.4±11.8mg/dl; p<0.9); resting pupil size: (TRP: 0.38±0.07AU vs. PLB: 0.35±0.08AU; p<0.01); haematocrit: (TRP: 45.3%±1.5% vs. PLB: 46.1%±2.6%; p<0.40). ConclusionsHigher tryptophan levels reduced the increased subjective perception of fatigue (SPF). In the component analysis the impact of tryptophan was estimated as 4% in our model. Tryptophan supplementation did not affect renal function. Tryptophan supplementation altered pupil size. At the dose used, tryptophan supplementation proved effective for the first 2h following the last intake of the tryptophan supplement.

Train drivers’ subjective perceptions of their abilities to perceive and control fatigue

Issues about train driver fatigue are important in the safety of railway systems. This study investigates the subjective perception of fatigue of conventional railway system drivers. The multidimensional Rasch model was used to measure two subjective latent constructs, namely, perceived fatigue awareness and perceived fatigue control. Analytical results show that 21% of the train drivers are unable to control fatigue. Randomly assigned vehicles with various cabin control systems for work shifts is the most unlikely scenario for drivers to perceive and control fatigue. Our results demonstrate that a driver who is unmarried, holds a university degree and has limited driving experience exhibits a low perceived ability to control fatigue. Thus, segmented programs for fatigue risk mitigation should be developed for specific drivers. The findings of this study can help railway safety managers and government regulators in developing and evaluating a management system for driver fatigue risk.

No association of leg strength asymmetry with walking ability, fatigability, and fatigue in multiple sclerosis.

This cross-sectional study aims to determine whether leg strength asymmetries are associated with walking ability, objective measures of fatigability, or subjective perceptions of fatigue. Maximal knee extensor strength was assessed in 19 patients with multiple sclerosis (PwMS), and a symmetry index was calculated. Walking ability was determined through the total distance covered during a 6-min walk test (6MWT) and fatigability by calculating the change in distance covered between minutes 6 and 1. Perceptions of fatigue were assessed using the Fatigue Severity Scale and by obtaining ratings of perceived exertion during the first and final minute of the 6MWT. PwMS covered less distance (P=0.01) and perceived greater exertion (P<0.01) during minute 6 compared with minute 1. Knee extensor strength was asymmetric (P<0.01). The magnitude of asymmetry did not correlate with walking ability, fatigability, or measures of fatigue. Knee extensor strength asymmetry may not play an important role in prolonged walking performance in PwMS.

A Comprehensive Literature Review of COPD-Related Fatigue

Chronic Obstructive Pulmonary Disease (COPD) is a chronic disease and major cause of disability. COPD may be considered a systemic disease, which causes an array of symptoms, one of which is the subjective sensation of fatigue. In recent years, COPD-related fatigue (COPD-RF) has increasingly been recognised as an important area of research. The aim of this paper is to comprehensively review the literature concerning this topic and to summarise existing knowledge on the subjective perception of fatigue in people with COPD. This paper provides a narrative review of literature in this area. The search used the electronic databases of OVID MEDLINE and EMBASE included original studies from 1980 to December 2011. The databases were searched using the key MeSH terms COPD and Fatigue. In total 40 relevant publications were identified. This literature review covers the following areas identified by research studies: fatigue in COPD in comparison with healthy older people, gender differences, patients’ experience of fatigue, prevalence of fatigue reporting in COPD, pattern and frequency of fatigue in COPD, the impact of fatigue on an individual’s life, predictors of fatigue, coping and treatment strategies for the management of fatigue. Furthermore, this review identifies areas for further research and makes recommendations for clinical practice.

Measurement of Travel Fatigue

Using both objective monitoring and subjective estimation, this paper investigates travel fatigue. Objective monitoring included an experiment designed to measure energy expenditure rates with a heart rate monitor while travelers walked on level ground, went up and down stairs, and rode on a bus and subway. Free modulus magnitude estimation was used to investigate travelers’ subjective perceptions of fatigue while traveling. The results of the two parts were compared to understand their relationship. The results showed that the energy expenditure rate was sensitive not only to travel mode, represented by running vehicle acceleration, but also to posture, carrying personal belongings, and in-vehicle crowding. According to participants’ subjective perceptions, the effect of in-vehicle crowding was greater than carrying a 3.8-kg burden; the fatigue rates of standing, both with and without a load, tended to be subjectively overestimated compared with normally transformed energy expenditure rates. Numerical results from a case study in Zhongshan, China, and an online survey of bigger cities in China showed that travel time is not the only issue. Travel fatigue must also be considered in planning urban transportation systems and in evaluating transit service quality and has great potential for predicting choice of travel mode.

Effects of oral administration of caffeine and D-ribose on mental fatigue

Objective We examined the effects of administering two different candidate antifatigue substances, caffeine and D-ribose, on mental fatigue. Methods In a double-blinded, placebo-controlled, three-way crossover design, 17 healthy volunteers were randomized to oral caffeine (200 mg/d), D-ribose (2000 mg/d), or placebo for 8 d. As fatigue-inducing mental tasks, subjects performed a 30-min Uchida-Kraepelin psychodiagnostic test and a 30-min advanced trail-making test on four occasions. Results During the tasks, the task performance of the caffeine group was better than that of the placebo group. However, after the fatigue-inducing tasks, although subjective perception of fatigue, motivation, or sleepiness was not significantly different, plasma branched-chain amino acid levels in the caffeine group were lower than those of the placebo group. Administration of D-ribose had no effect. Conclusion Because plasma branched-chain amino acid levels are decreased by mental fatigue, these results suggest that administration of caffeine improved task performance through the enhancement of central nervous system activity without increasing the sensation of fatigue. However, further decreases in branched-chain amino acid levels indicate that caffeine might promote deeper fatigue than placebo. Unfortunately, research subsequent to our study design has shown that D-ribose dosing higher than we used is needed to see a clinical effect and therefore no conclusions can be made from this study as to the efficacy of D-ribose.

Characterization of a laboratory model of computer mouse use—Applications for studying risk factors for musculoskeletal disorders

In the present study, we assessed the wrist kinetics (range of motion, mean position, velocity and mean power frequency in radial/ulnar deviation, flexion/extension, and pronation/supination) associated with performing a mouse-operated computerized task involving painting rectangles on a computer screen. Furthermore, we evaluated the effects of the painting task on subjective perception of fatigue and wrist position sense. The results showed that the painting task required constrained wrist movements, and repetitive movements of about the same magnitude as those performed in mouse-operated design tasks. In addition, the painting task induced a perception of muscle fatigue in the upper extremity (Borg CR-scale: 3.5, p<0.001) and caused a reduction in the position sense accuracy of the wrist (error before: 4.6°, error after: 5.6°, p<0.05). This standardized painting task appears suitable for studying relevant risk factors, and therefore it offers a potential for investigating the pathophysiological mechanisms behind musculoskeletal disorders related to computer mouse use.