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Purpose This study investigated the effect of ischemic preconditioning (IP) on metaboreflex activation following dynamic leg extension exercise in a group of healthy participants. Method Seventeen healthy participants were recruited. IP and SHAM treatments (3 × 5 min cuff occlusion at 220 mmHg or 20 mmHg, respectively) were administered in a randomized order to the upper part of exercising leg’s thigh only. Muscle pain intensity (MP) and pain pressure threshold (PPT) were monitored while administrating IP and SHAM treatments. After 3 min of leg extension exercise at 70% of the maximal workload, a post-exercise muscle ischemia (PEMI) was performed to monitor the discharge group III/IV muscle afferents via metaboreflex activation. Hemodynamics were continuously recorded. MP was monitored during exercise and PEMI. Results IP significantly reduced mean arterial pressure compared to SHAM during metaboreflex activation (mean ± SD, 109.52 ± 7.25 vs. 102.36 ± 7.89 mmHg) which was probably the consequence of a reduced end diastolic volume (mean ± SD, 113.09 ± 14.25 vs. 102.42 ± 9.38 ml). MP was significantly higher during the IP compared to SHAM treatment, while no significant differences in PPT were found. MP did not change during exercise, but it was significantly lower during the PEMI following IP (5.10 ± 1.29 vs. 4.00 ± 1.54). Conclusion Our study demonstrated that IP reduces hemodynamic response during metaboreflex activation, while no effect on MP and PPT were found. The reduction in hemodynamic response was likely the consequence of a blunted venous return.

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The dorsolateral prefrontal cortex (DLPFC) is a crucial brain region for inhibitory control, an executive function essential for behavioral self-regulation. Recently, inhibitory control has been shown to be important for endurance performance. Improvement in inhibitory control was found following transcranial direct current stimulation (tDCS) applied over the left DLPFC (L-DLPFC). This study examined the effect tDCS on both an inhibitory control and endurance performance in a group of healthy individuals. Twelve participants received either real tDCS (Real-tDCS) or placebo tDCS (Sham-tDCS) in randomized order. The anodal electrode was placed over the L-DLPFC while the cathodal electrode was placed above Fp2. Stimulation lasted 30 min with current intensity set at 2 mA. A Stroop test was administered to assess inhibitory control. Heart rate (HR), ratings of perceived exertion (RPE), and leg muscle pain (PAIN) were monitored during the cycling time to exhaustion (TTE) test, while blood lactate accumulation (∆B[La−]) was measured at exhaustion. Stroop task performance was improved after Real-tDCS as demonstrated by a lower number of errors for incongruent stimuli (p = 0.012). TTE was significantly longer following Real-tDCS compared to Sham-tDCS (p = 0.029, 17 ± 8 vs 15 ± 8 min), with significantly lower HR (p = 0.002) and RPE (p < 0.001), while no significant difference was found for PAIN (p > 0.224). ∆B[La−] was significantly higher at exhaustion in Real-tDCS (p = 0.040). Our findings provide preliminary evidence that tDCS with the anodal electrode over the L-DLPFC can improve both inhibitory control and endurance cycling performance in healthy individuals.

Purpose The aim of this study was to test the hypothesis that subjective thermal strain can reduce endurance performance independently from the general physiological strain normally associated with impaired endurance performance in the heat. Methods In 20 °C and 44% relative humidity, 12 endurance-trained athletes (1♀ 11♂; mean ± SD; age: 27 ± 6 y; VO2max: 61 ± 6 ml/kg/min) performed a time to exhaustion (TTE) test in two different experimental conditions: with an electric heat pad applied to the subjects' upper back (HP) and control (CON: without heat pad). In both conditions, subjects cycled to volitional exhaustion at 70% of their VO2max. Cardiorespiratory, metabolic, thermoregulatory and perceptual responses were measured throughout the TTE test and compared at 0%, 50% and 100% isotime and at exhaustion. Results TTE was reduced by 9% in HP (2092 ± 305 s) compared to CON (2292 ± 344 s; p = .023). The main effect of condition on thermal discomfort at isotime (p = .002), the effect of condition on thermal sensation at 0% isotime (p = .004) and the condition by isotime interaction on rating of perceived exertion (p = .036) indicated higher subjective thermal strain in HP compared to CON. None of the measured cardiorespiratory, metabolic and thermoregulatory variables differed significantly between conditions. Conclusion Our novel experimental manipulation (HP) was able to induce significant subjective thermal strain and reduce endurance performance in a temperate environment without inducing the general physiological strain normally associated with impaired endurance performance in the heat. These results suggest that subjective thermal strain is an important and independent mediator of the heat-induced impairment in endurance performance.

Purpose It is well established that mental fatigue impairs performance during lab-based endurance tests lasting less than 45 min. However, the effects of mental fatigue on longer duration endurance events and in field settings are unknown. The aim of this study was to investigate the effect of mental fatigue on performance during a half-marathon race. Methods Forty-six male amateur runners (means ± SD: age 43.8 ± 8.6 years, $$\dot V{O_{2peak}}$$ V ˙ O 2 p e a k 46.0 ± 4.1 ml/kg/min) completed a half-marathon after being randomly allocated to performing a 50-min mentally fatiguing task (mental fatigue group) or reading magazines for 50 min (control group). Running speed, heart rate, and perceived effort were measured during the race. Results Runners in the mental fatigue group completed the half-marathon approximately 4 min slower (106.2 ± 12.4 min) than those in the control group (102.4 ± 10.2 min), but this difference was not statistically significant (Cohen’s d = 0.333; p = 0.265). However, equivalence was not established [t(40.88) = 0.239, p = 0.594] and equivalence testing analysis excluded a beneficial effect of mental fatigue on half-marathon performance. Conclusion Due to its posttest-only design and the achievable sample size, the study did not have enough power to provide evidence that the observed 4-min increase in half-marathon time is statistically significant. However, equivalence testing suggests that mental fatigue has no beneficial effect on half-marathon performance in male amateur runners, and a harmful effect cannot be excluded. Overall, it seems prudent for endurance athletes to avoid mentally fatiguing tasks before competitions.

Background and Aims: People with type 1 diabetes (T1D) experience higher rates of sleep disturbances than those without diabetes, and this can have negative implications for glycemic control. Sleep is critical for optimal athletic performance and recovery so it is important to have an understanding of factors that can influence sleep in athletes with T1D. This study investigated whether there is a relationship between i) daily training load and ii) time in glycemic ranges on sleep time of professional cyclists with T1D. Methods: Sixteen professional cyclists from Team Novo Nordisk (age 27 ± 4 y; HbA1c 6.8 ± 0.5%) used a wrist-worn actigraph device (Actiwatch Spectrum Plus, Philips Respironics, Murrysville, PA) to monitor sleep-wake activity over a 10-day training camp. Training variables (distance (km), elevation (m), work (kJ)) were used to determine a training stress score (TSS) for each day of the camp and glycemia was recorded using Dexcom, G6 (San Diego, CA). Summary statistics and correlations were run over the measured variables. Results: On average, riders spent 8.6 ± 1 h in bed with a total sleep time of 7 ± 1.3 h (6.0 ÷ 7.8). The riders cycled 115 ± 26 km with 1849 ± 1086 m of elevation gain per day, corresponding to a mean TSS of 221 ± 142. Total sleep time was negatively associated with TSS (-0.29, p=0.01). Greater time in range (4-10 mmol/l) was positively associated with sleep time (r=0.21, p=0.03), with hyperglycemia, particularly level 2 (>14 mmol/l), being negatively associated with sleep time (-0.21, p=0.03). Conclusions: We provide preliminary evidence that a greater TSS is negatively associated with total sleep time in professional athletes with T1D. Second, greater time spent in euglycemia is associated with greater sleep time, with time above target having a negative association with sleep. Further data should be collected longitudinally to strengthen these results to serve as a basis to promote better sleep hygiene practices to overcome the effects of higher training loads. Disclosure S.N. Scott: None. F.Y. Fontana: None. B. Martinez-Gonzalez: None. C.A. Hayes: Other Relationship; Self; Novo Nordisk A/S. P.H. Lagrou: None. S. Marcora: None. T. Zueger: None. C. Stettler: None.

Introduction: Mental fatigue is associated with a shift of electroencephalography (EEG) power towards low-frequency bands [theta, alpha(a)], which is suggested to be related to a decrease in the level of arousal. In addition a decrease in the amplitude of event related brain potentials like P2 (i.e. an index of activity engaged in selection of relevant information) is also observed with the occurrence of mental fatigue. In order to further elucidate the role of these brain alterations in the occurrence of mental fatigue we sought to prevent them with a caffeine-maltodextrin (CAF-MALT) mouth rinse intervention during a mentally fatiguing task. Methods: Ten active healthy males (age: 23±2y, physical activity: 7.3±4.3h/week), which were all low CAF users (101±97mg/day), performed two experimental trials in a randomized crossover order. In both trials participants first completed a baseline Flanker task (3min). Next they performed a 90-min mentally fatiguing task (Stroop task), that was immediately followed by aFlanker task. Before the start and after each 12.5% of the Stroop task (8 blocks of 11min) subjects received either a CAF-MALT mouth rinse (MR; 0.3g/25ml CAF; 1.6g/25ml MALT) or placebo (PLAC; 25ml artificial saliva). To measure mental fatigue, physiological and psychological measures were assessed. EEG (32 active electrodes) was applied throughout the experiment to record brain activity. Normality was checked, repeated measure ANOVAs were employed to observe interaction and/or main effects of condition and/or time. Follow up tests were performed where necessary (p

Since respiratory frequency (fR) has been proposed as a good marker of physical effort, furthering the understanding of how fR is regulated during exercise is of great importance. We manipulated recovery intensity and exercise duration during high-intensity interval training (HIIT) to test the hypothesis that fast inputs (including central command) contribute more than metabolic stimuli to fR regulation. Seven male cyclists performed an incremental test, a 10 min and a 20 min continuous time trial (TT) as preliminary tests. Subsequently, recovery intensity and exercise duration were manipulated during HIIT (30 s work and 30 s active recovery) by performing four 10 min and one 20 min trial (recovery intensities: 85%, 70%, 55% and 30% of the 10 min TT mean workload; 85% of the 20 min TT mean workload). The work intensity of the HIIT sessions was self-paced by participants to achieve the best performance possible. When manipulating recovery intensity, fR, but not tidal volume (VT), showed a fast response to the alternation of the work and recovery phases, proportional to the extent of workload variations. No association between fR and gas exchange responses was observed. When manipulating exercise duration, fR and Rating of Perceived Exertion (RPE) were dissociated from VT, VCO2 and VO2 responses. Overall, RPE was strongly correlated with fR (r = 0.87; P

Purpose: To investigate the impact of twice-daily inhalation of 100 µg of salmeterol (SAL) or 12 µg of formoterol (FOR) in addition to a strength- and power-training program over a 5-wk period on a 30-m sprint, strength, power, mood, stress, and skinfold thickness. Methods: In a randomized, single-blind study, 23 male and 15 female nonasthmatic, recreationally active individuals were recruited (mean [SD] age 26.3 [5.4] y, weight 76.2 [11.5] kg, height 176.9 [8.5] cm). Participants completed 3 standardized whole-body strength- and power-training sessions per week for 5 wk during which they were assigned to an SAL, FOR, or placebo group. Participants used their inhaler twice per day as instructed and completed assessments of sprint, strength, and power at baseline and 1 wk after cessation of the training program. The assessments included a 30-m sprint, vertical jump, 1-repetition-maximum (1RM) bench press, 1RM leg press, peak torque flexion and extension, anthropometric evaluation, and Rest-Q questionnaires. Results: After 5 wk of strength and power training, 30-m sprint time reduced in the FOR (0.29 [0.11] s, P = .049) and SAL (0.35 [0.05] s, P = .040) groups compared with placebo (+0.01 [0.11] s). No significant change was found in other assessments of strength, mood, or skinfold thickness. Conclusions: When strength and power training are combined with the inhalation of FOR or SAL over a 5-wk period, moderately trained individuals experience an improvement in 30-m sprint performance.

Background: Stimulation of the right and left anterior insular cortex, increases and decreases the cardiovascular response respectively, thus indicating the brain’s lateralization of the neural control of circulation. Previous experiments have demonstrated that transcranial direct current stimulation (tDCS) modulates the autonomic cardiovascular control when applied over the temporal cortex. Given the importance of neural control for a normal hemodynamic response, and the potential for the use of tDCS in the treatment of cardiovascular diseases, this study investigated whether tDCS was capable of modulating autonomic regulation.\ud \ud Methods: Cardiovascular response was monitored during a post-exercise muscle ischemia (PEMI) test, which is well-documented to increase sympathetic drive. A group of 12 healthy participants performed a PEMI test in a control (CON), sham (Sham) and two different experimental sessions where the anodal electrode was applied over the left temporal cortex and right temporal cortex with the cathodal electrode placed over the contralateral supraorbital area. Stimulation lasted 20 min at 2 mA. The hemodynamic profile was measured during a PEMI test. The cardiovascular parameters were continuously measured with a transthoracic bio-impedance device both during the PEMI test and during tDCS.\ud \ud Results: None of the subjects presented any side effects during or after tDCS stimulation. A consistent cardiovascular response during PEMI test was observed in all conditions. Statistical analysis did not find any significant interaction and any significant main effect of condition on cardiovascular parameters (all ps > 0.316) after tDCS. No statistical differences regarding the hemodynamic responses were found between conditions and time during tDCS stimulation (p > 0.05).\ud \ud Discussion: This is the first study comparing the cardiovascular response after tDCS stimulation of left and right TC both during exercise and at rest. The results of the current study suggest that anodal tDCS of the left and right TC does not affect functional cardiovascular response during exercise PEMI test and during tDCS. In light of the present and previous findings, the effect of tDCS on the cardiovascular response remains inconclusive.

The capacity to sustain high-intensity aerobic exercise is essential for endurance performance. Therefore, it is important to understand what is the factor limiting time to exhaustion (TTE) in healthy and fit adults. In Study 1, maximal voluntary cycling power (MVCP) was measured in 11 volunteers before and immediately after a high-intensity TTE test on cycle ergometer. Cadence was 60 rpm in both the MVCP and TTE tests. Despite a 35% loss in MVCP, power produced during the final MVCP test (mean ± SD 469 ± 111 W) was significantly higher than the power required by the TTE test (269 ± 55 W) (P < 0.001). In Study 2, 12 participants performed a cold pressor test (CPT) to the limit of tolerance followed by a high-intensity TTE test on cycle ergometer. Ratings of pain unpleasantness (RPU) during the TTE test were anchored to the unpleasantness of pain experienced during the CPT. On average, the RPU was 9.7 ± 0.4 at completion of the CPT and 5.0 ± 0.9 at exhaustion during the TTE test. The difference between these two ratings of pain unpleasantness was statistically significant (P < 0.001). In both Studies 1 and 2, the slope of the rating of perceived exertion (RPE) during the TTE test correlated significantly with TTE (r = –0.75 and –0.83, P < 0.01). Results of this two-part investigation suggest that perception of effort, rather than severe locomotor muscle fatigue or intolerably unpleasant muscle pain, is the cardinal exercise stopper during high-intensity aerobic exercise. © 2018 Elsevier B.V.

Purpose: Transcranial direct current stimulation (tDCS) provides a new exciting means to investigate the role of the brain during exercise. However, this technique is not widely used in exercise science, with little known regarding effective electrode montages. This study investigated whether tDCS of the motor cortex (M1) would elicit an analgesic response to exercise-induced pain (EIP). Methods: Nine participants completed a VO2max test and three time to exhaustion (TTE) tasks on separate days following either 10 min 2 mA tDCS of the M1, a sham or a control. Additionally, seven participants completed 3 cold pressor tests (CPT) following the same experimental conditions (tDCS, SHAM, CON). Using a well-established tDCS protocol, tDCS was delivered by placing the anodal electrode above the left M1 with the cathodal electrode above dorsolateral right prefrontal cortex. Gas exchange, blood lactate, EIP and ratings of perceived exertion (RPE) were monitored during the TTE test. Perceived pain was recorded during the CPT. Results: During the TTE, no significant differences in time to exhaustion, RPE or EIP were found between conditions. However, during the CPT, perceived pain was significantly (P

Purpose Time to exhaustion (TTE) tests used in the determination of critical power (CP) and curvature constant (W′) of the power–duration relationship are strongly influenced by the perception of effort (PE). This study aimed to investigate whether manipulation of the PE alters the CP and W′. Methods Eleven trained cyclists completed a series of TTE tests to establish CP and W′ under two conditions, following a mentally fatiguing (MF), or a control (CON) task. Both cognitive tasks lasted 30 min followed by a TTE test. Ratings of PE and heart rate (HR) were measured during each TTE. Blood lactate was taken pre and post each TTE test. Ratings of perceived mental and physical fatigue were taken pre- and post-cognitive task, and following each TTE test. Results Perceived MF significantly increased as a result of the MF task compared to baseline and the CON task (P P > 0.05). PE was significantly higher during TTE in the MF condition (P P P > 0.05). Neither cognitive task induced any change in CP (MF 253 ± 51 vs. CON 247 ± 58W; P > 0.05), although W′ was significantly reduced in the MF condition (MF 22.8 ± 4.5 vs. CON 29.3 ± 6.3 kJ; P Conclusion MF has no effect of CP, but reduces the W′ in trained cyclists. Lower lactate accumulation during TTE tests following MF suggests that cyclists were not able to fully expend W′ even though they exercised to volitional exhaustion.

Background: Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity. It has recently been suggested that mental fatigue can affect physical performance. Objective: Our objective was to evaluate the literature on impairment of physical performance due to mental fatigue and to create an overview of the potential factors underlying this effect. Methods: Two electronic databases, PubMed and Web of Science (until 28 April 2016), were searched for studies designed to test whether mental fatigue influenced performance of a physical task or influenced physiological and/or perceptual responses during the physical task. Studies using short (

Purpose Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity and has been observed to decrease time trial (TT) endurance performance by ∼3.5% in normal ambient temperatures. Recently, it has been suggested that heat may augment the negative effect of mental fatigue on cognitive performance, raising the question whether it may also amplify the effect of mental fatigue on TT performance. Methods In 30°C and 30% relative humidity, 10 endurance-trained male athletes (mean ± SD; age = 22 ± 3 yr, W max = 332 ± 41 W) completed two experimental conditions: intervention (I; 45-min Stroop task) and control (C; 45-min documentary). Pre- and postintervention/control, cognitive performance was followed up with a 5-min Flanker task. Thereafter, subjects cycled for 45 min at a fixed pace equal to 60% W max, immediately followed by a self-paced TT in which they had to produce a fixed amount of work (equal to cycling 15 min at 80% W max) as fast as possible. Results Self-reported mental fatigue was significantly higher after I compared with C (P < 0.05). Moreover EEG measures also indicated the occurrence of mental fatigue during the Stroop (P < 0.05). TT did not differ between conditions (I = 906 ± 30 s, C = 916 ± 29 s). Throughout exercise, physiological (HR, blood lactate, core, and skin temperature) and perceptual measures (perception of effort and thermal sensation) were not affected by mental fatigue. Conclusion No negative effects of mild mental fatigue were observed on performance and the physiological and perceptual responses to endurance exercise in the heat. Most plausibly, mild mental fatigue does not reduce endurance performance when the brain is already stressed by a hot environment. © 2017 by the American College of Sports Medicine.

PURPOSE: The aim of this study was to test the hypotheses that prolonged mental exertion (i) reduces maximal muscle activation and (ii) increases the extent of central fatigue induced by subsequent endurance exercise. METHODS: The neuromuscular function of the knee extensor muscles was assessed in 10 male subjects in two different conditions: (i) before and after prolonged mental exertion leading to mental fatigue and (ii) before and after an easy cognitive task (control). Both cognitive tasks lasted 90 min and were followed by submaximal isometric knee extensor exercise until exhaustion (endurance task), and a third assessment of neuromuscular function. RESULTS: Time to exhaustion was 13% ± 4% shorter in the mental fatigue condition (230 ± 22 s) compared with the control condition (266 ± 26 s) (P < 0.01). Prolonged mental exertion did not have any significant effect on maximal voluntary contraction torque, voluntary activation level, and peripheral parameters of neuromuscular function. A similar significant decrease in maximal voluntary contraction torque (mental fatigue condition: -26.7% ± 5.7%; control condition: -27.6% ± 3.3%, P < 0.001), voluntary activation level (mental fatigue: - 10.6% ± 4.3%; control condition: - 11.2% ± 5.2%, P < 0.05), and peripheral parameters of neuromuscular function occurred in both conditions after the endurance task. However, mentally fatigued subjects rated perceived exertion significantly higher during the endurance task compared with the control condition (P < 0.05). CONCLUSIONS: These findings provide the first experimental evidence that prolonged mental exertion (i) does not reduce maximal muscle activation and (ii) does not increase the extent of central fatigue induced by subsequent endurance exercise. The negative effect of mental fatigue on endurance performance seems to be mediated by the higher perception of effort rather than impaired neuromuscular function. Copyright © 2013 by the American College of Sports Medicine.

PurposeLocomotor muscle fatigue impairs exercise performance during time to exhaustion tests. However, its effect on self-regulation of power output (pacing) is unknown. The primary aim of this study was to investigate the effects of locomotor muscle fatigue on pacing and time trial performance.MethodsTen healthy recreationally active men completed a 15-min time trial on a cycle ergometer 30 min after undergoing an eccentric fatiguing protocol designed to induce a substantial strength loss in the knee extensor muscles without inducing significant metabolic stress. This fatigue condition was compared with a control condition, using a randomly counterbalanced AB/BA crossover design.ResultsTotal work completed during the 15-min cycling time trial was significantly reduced by 4.8 % in the fatigue condition compared with the control condition. This was caused by a significant reduction in power output. Rating of perceived exertion was significantly higher in the fatigue condition compared with the control condition only during the first 3 min of the time trial. Heart rate and vastus lateralis integrated electromyogram were not significantly different between the two conditions.ConclusionThe results show that participants with fatigued locomotor muscles reduce their pace but do not change their pacing strategy. As a result, there was a significant reduction in time trial performance. As predicted by the psychobiological model of exercise performance, a slower pace may be a behavioral response to compensate for the significant increase in perception of effort induced by locomotor muscle fatigue.Keywords: Perception of effort, Cycling exercise, Eccentric fatigue, Pacing strategy, Exercise tolerance, Electromyography

The V.O2 slow component (V.O2sc) that develops during high-intensity aerobic exercise is thought to be strongly associated with locomotor muscle fatigue. We sought to experimentally test this hypothesis by pre-fatiguing the locomotor muscles used during subsequent high-intensity cycling exercise. Over two separate visits, eight healthy male participants were asked to either perform a non-metabolically stressful 100 intermittent drop-jumps protocol (pre-fatigue condition) or rest for 33 min (control condition) according to a random and counterbalanced order. Locomotor muscle fatigue was quantified with 6-s maximal sprints at a fixed pedaling cadence of 90 rev·min-1. Oxygen kinetics and other responses (heart rate, capillary blood lactate concentration and rating of perceived exertion, RPE) were measured during two subsequent bouts of 6 min cycling exercise at 50% of the delta between the lactate threshold and V.O2max determined during a preliminary incremental exercise test. All tests were performed on the same cycle ergometer. Despite significant locomotor muscle fatigue (P = 0.03), the V.O2sc was not significantly different between the pre-fatigue (464 ± 301 mL·min-1) and the control (556 ± 223 mL·min-1) condition (P = 0.50). Blood lactate response was not significantly different between conditions (P = 0.48) but RPE was significantly higher following the pre-fatiguing exercise protocol compared with the control condition (P < 0.01) suggesting higher muscle recruitment. These results demonstrate experimentally that locomotor muscle fatigue does not significantly alter the V.O2 kinetic response to high intensity aerobic exercise, and challenge the hypothesis that the V.O2sc is strongly associated with locomotor muscle fatigue. © 2016 Hopker, Caporaso, Azzalin, Carpenter and Marcora.

We recently developed a high intensity one leg dynamic exercise (OLDE) protocol to measure muscle endurance and investigate the central and peripheral mechanisms of muscle fatigue. The aims of the present study were to establish the reliability of this novel protocol and describe the isokinetic muscle fatigue induced by high intensity OLDE and its recovery. Eight subjects performed the OLDE protocol (time to exhaustion test of the right leg at 85% of peak power output) three times over a week period. Isokinetic maximal voluntary contraction torque at 60 (MVC60), 100 (MVC100) and 140 (MVC140) deg/s was measured preexercise, shortly after exhaustion (13 ± 4 s), 20 s (P20) and 40 s (P40) post±exercise. Electromyographic (EMG) signal was analyzed via the root mean square (RMS) for all three superficial knee extensors. Mean time to exhaustion was 5.96 ± 1.40 min, coefficient of variation was 8.42 ± 6.24%, typical error of measurement was 0.30 min and intraclass correlation was 0.795. MVC torque decreased shortly after exhaustion for all angular velocities (all P < 0.001). MVC60 and MVC100 recovered between P20 (P < 0.05) and exhaustion and then plateaued. MVC140 recovered only at P40 (P < 0.05). High intensity OLDE did not alter maximal EMG RMS of the three superficial knee extensors during MVC. The results of this study demonstrate that this novel high intensity OLDE protocol could be reliably used to measure muscle endurance, and that muscle fatigue induced by high intensity OLDE should be examined within ∼ 30 s following exhaustion. © 2016 Pageaux et al.This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Objectives: To investigate the effects of a Mediterranean type diet on patients with osteoarthritis (OA). Participants: Ninety-nine volunteers with OA (aged 31 - 90 years) completed the study (83% female). Setting: Southeast of England, UK. Design: Participants were randomly allocated to the dietary intervention (DIET, n = 50) or control (CON, n = 49). The DIET group were asked to follow a Mediterranean type diet for 16 weeks whereas the CON group were asked to follow their normal diet. Measurements: All participants completed an Arthritis Impact Measurement Scale (AIMS2) pre-, mid- and post- study period. A subset of participants attended a clinic at the start and end of the study for assessment of joint range of motion, ROM (DIET = 33, CON = 28), and to provide blood samples (DIET = 29, CON = 25) for biomarker analysis (including serum cartilage oligomeric matrix protein (sCOMP) (a marker of cartilage degradation) and a panel of other relevant biomarkers including pro- and anti-inflammatory cytokines). Results: There were no differences between groups in the response of any AIMS2 components and most biomarkers (p > 0.05), except the pro-inflammatory cytokine IL-1α, which decreased in the DIET group (~47%, p = 0.010). sCOMP decreased in the DIET group by 1 U/L (~8%, p = 0.014). There was a significant improvement in knee flexion and hip rotation ROM in the DIET group (p < 0.05). Conclusions: The average reduction in sCOMP in the DIET group (1 U/L) represents a meaningful change, but the longer term effects require further study. © 2016, The Author(s).

Purpose: Given the important role of the brain in regulating endurance performance, this comparative study sought to determine whether professional road cyclists have superior inhibitory control and resistance to mental fatigue compared to recreational road cyclists. Methods: After preliminary testing and familiarization, eleven professional and nine recreational road cyclists visited the lab on two occasions to complete a modified incongruent colour-word Stroop task (a cognitive task requiring inhibitory control) for 30 min (mental exertion condition), or an easy cognitive task for 10 min (control condition) in a randomized, counterbalanced cross-over order. After each cognitive task, participants completed a 20-min time trial on a cycle ergometer. During the time trial, heart rate, blood lactate concentration, and rating of perceived exertion (RPE) were recorded. Results: The professional cyclists completed more correct responses during the Stroop task than the recreational cyclists (705±68 vs 576±74, p = 0.001). During the time trial, the recreational cyclists produced a lower mean power output in the mental exertion condition compared to the control condition (216±33 vs 226±25 W, p = 0.014). There was no difference between conditions for the professional cyclists (323±42 vs 326±35 W, p = 0.502). Heart rate, blood lactate concentration, and RPE were not significantly different between the mental exertion and control conditions in both groups. Conclusion: The professional cyclists exhibited superior performance during the Stroop task which is indicative of stronger inhibitory control than the recreational cyclists. The professional cyclists also displayed a greater resistance to the negative effects of mental fatigue as demonstrated by no significant differences in perception of effort and time trial performance between the mental exertion and control conditions. These findings suggest that inhibitory control and resistance to mental fatigue may contribute to successful road cycling performance. These psychobiological characteristics may be either genetic and/or developed through the training and lifestyle of professional road cyclists. © 2016 Martin et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

It is thought that perception of effort during physical tasks is the conscious awareness of the central motor command sent to the active muscles. The aim of this study was to directly test this hypothesis by experimentally varying perception of effort and measuring movement-related cortical potential (MRCP). Sixteen healthy, recreationally active men made unilateral dynamic elbow flexions to lift a light (20% one repetition maximum, 1RM) and a heavier (35% 1RM) weight with a fatigued arm and a nonfatigued arm while rating of perceived effort (RPE), biceps brachii electromyogram (EMG), and MRCP were recorded. RPE, EMG amplitude, and MRCP amplitude at Cz during weight raising increased with weight and with muscle fatigue. There was a significant correlation between RPE and MRCP amplitude at the vertex during the weight raising epoch. This study provides direct neurophysiological evidence that perception of effort correlates with central motor command during movement execution.

We have recently demonstrated that electromyogram (EMG) amplitude of the frowning muscles correlates with perception of effort during leg-extension exercise. However, during aerobic exercise the relationship between facial EMG and perception of effort has never been investigated. The aim of the present study was to investigate whether facial EMG reflects perception of effort also during constant-workload cycling. We investigated the effects of exercise duration and exercise intensity on facial EMG of the corrugator supercilii muscles, rating of perceived effort, heart rate, and blood lactate concentration. Twenty recreationally active male and female volunteers performed a constant-workload time to exhaustion test on a cycle ergometer. Participants were randomly allocated to the heavy-intensity [63 ± 3% peak power output (Ppeak)], or the severe-intensity (80 ± 5% Ppeak) group. The results show that facial EMG can differentiatebetween two exercise intensities during constant-workload cycling. The effects of exercise duration are inconclusive. Facial EMG increased over time in the severe-intensity group, but not in the heavy-intensity group. Future studies testing a wider range of exercise intensities are required to establish a correlation between facial EMG and exercise intensity during aerobic exercise, and further investigations are needed to establish why there is a discrepancy between facial EMG and perception of effort during lower-intensity aerobic exercise. © 2011 Springer-Verlag.

Objective. To confirm, in a randomized controlled trial (RCT), the efficacy of high-intensity progressive resistance training (PRT) in restoring muscle mass and function in patients with rheumatoid arthritis (RA). Additionally, to investigate the role of the insulin-like growth factor (IGF) system in exercise-induced muscle hypertrophy in the context of RA. Methods. Twenty-eight patients with established, controlled RA were randomized to either 24 weeks of twice-weekly PRT (n = 13) or a range of movement home exercise control group (n = 15). Dual x-ray absorptiometry-assessed body composition (including lean body mass [LBM], appendicular lean mass [ALM], and fat mass); objective physical function; disease activity; and muscle IGFs were assessed at weeks 0 and 24. Results. Analyses of variance revealed that PRT increased LBM and ALM (P < 0.01); reduced trunk fat mass by 2.5 kg (not significant); and improved training-specific strength by 119%, chair stands by 30%, knee extensor strength by 25%, arm curls by 23%, and walk time by 17% (for objective function tests, P values ranged from 0.027 to 0.001 versus controls). In contrast, body composition and physical function remained unchanged in control patients. Changes in LBM and regional lean mass were associated with changes in objective function (P values ranged from 0.126 to

Thirteen healthy Labrador retrievers underwent a 5-stage incremental treadmill exercise test to assess its reliability. Blood lactate (BL), heart rate (HR), and body temperature (BT) were measured at rest, after each stage of exercise, and after a 20-min recovery. Reproducibility was assessed by repeating the test after 7 days. Two-way MANOVAs revealed significant differences between consecutive stages, and between values at rest and after recovery. There was also a significant reduction in physiological strain between the first and second trial (learning effect). Test reliability expressed as typical error (BL = 0.22 mmol/l, HR = 9.81 bpm, BT = 0.22°C), coefficient of variation (BL = 19.3%, HR = 7.9% and BT = 0.6%) and test-retest correlation (BL = 0.89, HR = 0.96, BT = 0.95) was good. Results support test reproducibility although the learning effect needs to be controlled when investigating the exercise-related problems commonly observed in this breed. © Springer-Verlag 2009.

PURPOSE: There is widespread misunderstanding about the ability of constant-power tests to quantify changes in endurance performance. We have therefore compared the sensitivity of a constant-power test with that of a time trial for the effects of arterial oxygenation on endurance performance. METHODS: Eight cyclists performed three constant-power rides to exhaustion and three 5-km time trials on a cycle ergometer in conditions of normoxia, hypoxia, and hyperoxia. After logarithmic transformation of performance times, sensitivity was calculated as the mean change in time divided by the error of measurement derived from the standard deviation of change scores. RESULTS: In normoxia, performance times were 488 ± 77 s for the constant-power test and 454 ± 16 s (mean ± SD) for the time trial. The mean and standard deviation of the change in performance time from normoxia to hypoxia were much larger in the constant-power test (-45% ± 13%) than in the time trial (5.7% ± 1.6%); there was a similar disparity in the change from normoxia to hyperoxia (123% ± 37% and -4.1% ± 1.4%, respectively). However, sensitivity for the normoxia-hypoxia change in performance in the constant-power test (6.3, 90% confidence interval 4.3-11.4) was similar to that in the time trial (4.5, 3.0-8.2); sensitivities were also similar for the normoxia-hyperoxia changes (3.2, 2.1-6.0; 3.8, 2.5-6.9, respectively). P values for mean performance changes (range, 0.0002-0.000002) reflected these sensitivities. CONCLUSIONS: Time to exhaustion has sensitivity similar to that of time-trial time for the effects of arterial oxygenation and presumably other factors affecting endurance performance. Sensitivity need not be a concern when using constant-power tests to quantify changes in endurance performance. ©2008The American College of Sports Medicine.

Exercise-induced muscle damage (EIMD) is known to decrease muscle strength and power but its effect on endurance performance is unclear. Thirty moderately trained adult runners (24 men and six women) were randomly assigned to EIMD or control. The EIMD group jumped 100 times from a 35 cm bench, while controls did not perform any muscle-damaging exercise. Before and 48 h after treatment, subjects were tested on markers of EIMD, steady-state cardiorespiratory, metabolic and perceptual responses during a constant speed submaximal run; distance ran in 30 min on a treadmill. There were significant changes in muscle soreness, creatine kinase, and knee extensors strength (P

No abstract

The aims of this investigation were to describe the central alterations of neuromuscular function induced by exhaustive high-intensity one-leg dynamic exercise (OLDE, study 1) and to indirectly quantify feedback from group III-IV muscle afferents via muscle occlusion (MO, study 2) in healthy adult male humans. We hypothesized that these central alterations and their recovery are associated with changes in afferent feedback. Both studies consisted of two time-to-exhaustion tests at 85% peak power output. In study 1, voluntary activation level (VAL), M-wave, cervicomedullary motor evoked potential (CMEP), motor evoked potential (MEP), and MEP cortical silent period (CSP) of the knee extensor muscles were measured. In study 2, mean arterial pressure (MAP) and leg muscle pain were measured during MO. Measurements were performed preexercise, at exhaustion, and after 3 min recovery. Compared with preexercise values, VAL was lower at exhaustion (−13 ± 13%, P < 0.05) and after 3 min of recovery (−6 ± 6%, P = 0.05). CMEParea/Marea was lower at exhaustion (−38 ± 13%, P < 0.01) and recovered after 3 min. MEParea/Marea was higher at exhaustion (+25 ± 27%, P < 0.01) and after 3 min of recovery (+17 ± 20%, P < 0.01). CSP was higher (+19 ± 9%, P < 0.01) only at exhaustion and recovered after 3 min. Markers of afferent feedback (MAP and leg muscle pain during MO) were significantly higher only at exhaustion. These findings suggest that the alterations in spinal excitability and CSP induced by high-intensity OLDE are associated with an increase in afferent feedback at exhaustion, whereas central fatigue does not fully recover even when significant afferent feedback is no longer present.

Background: Tumor necrosis factor (TNF) is an important mediator of cachexia, and its blockade prevents catabolism in animal models. However, little evidence shows that anti-TNF therapy is effective in treating cachexia in humans. Objective: The main aim of this study was to investigate the effect of etanercept, a synthetic soluble TNF receptor, on body composition in patients with early rheumatoid arthritis (RA). Design: Twenty-six patients were randomly assigned to 24 wk of treatment with etanercept or methotrexate; the latter is the first-line therapy for RA. Body composition, physical function, disease activity, systemic inflammation, and the circulating insulin-like growth factor (IGF) system were measured at baseline (week 0) and at follow-up (weeks 12 and 24). Twelve patients in each treatment group (9 F, 3 M) completed the study. Results: Overall, no important changes in body composition were observed, despite a transient increase in IGF-I at week 12 (P < 0.01). However, the secondary analysis of those patients (6/treatment group) who gained weight during follow-up showed a significant effect of etanercept on the composition of the weight gained: 44% of weight gained in the etanercept group was fat-free mass, as compared with only 14% in the methotrexate group (P = 0.04). Etanercept and methotrexate were equally effective in controlling the disease and improving physical function. Conclusions: Anti-TNF therapy with etanercept is not superior to that with methotrexate for the treatment of rheumatoid cachexia over a period of 6 mo. However, TNF blockade seems to normalize the anabolic response to overfeeding and, if these findings are confirmed, may be useful in conditions characterized by anorexia and weight loss.

Background: Cystatin C (CysC) is an endogenous marker of glomerular filtration rate (GFR) that is claimed to be unaffected by body composition. In this study, we tested this speculation. Methods: In 77 patients with chronic kidney disease (mean age, 65.1 ± 11.9 [SD] years; mean indexed GFR, 45.7 ± 28.6 mL/min/1.73 m 2 [0.76 ± 0.48 mL/s]), we evaluated kidney function (GFR) by means of inulin clearance. CysC level was determined by using a particle-enhanced turbidimetric immunoassay. Total lean (LM) and fat masses were measured by means of dual-energy x-ray absorptiometry. Multiple regression was used to analyze relationships between absolute GFR, LM, fat mass, demographic and anthropometric variables (age, sex, height, and weight), and CysC levels. Then prediction equations were built that included only CysC level or CysC level and LM. Their performance to predict absolute GFR was evaluated in a subset of patients with extreme body composition (LM or fat mass > ±1 SD of the entire sample). Results: Only absolute GFR and LM significantly explained variance in CysC levels, and an equation including LM explained more variance in absolute GFR than an equation including CysC level alone. Consequently, the equation including LM performed better than the equation with only CysC level, especially in patients with extreme body composition, showing reduced bias and improved limits of agreement and accuracy (71.4% versus 51.4% of patients' predicted GFR did not deviate by >30% of GFR). Conclusion: LM is a previously unrecognized, but important, factor affecting CysC level, and GFR estimation improves when including LM. CysC level is not independent of body composition, as previously assumed, and hence accounting for body composition improves CysC-based GFR estimation.

Background. In this study (the first of two related papers), we report whether the relationship between the demographic and anthropometric variables (DA, i.e. age, gender, height and weight) employed in current creatinin (Cr)-based glomerular filtration rate (GFR) estimation equations and actual GFR is mediated by muscle mass. Methods. We studied 77 patients (mean age ± SD, 65.1 ± 11.9 years) with chronic kidney disease (mean GFR 45.7 ± 28.6 ml/ min/1.73 m2). Actual GFR was measured by the renal clearance of inulin (GFRinu). Appendicular lean mass (ALM) and its index (ALMI) by dual energy X-ray absorptiometry provided markers of muscle mass. Multiple regression analyses identified variables explaining variance in (i) GFR, (ii) ALM and (iii) Cr. Results. (i) The DA variables used in the abbreviated modification of diet in renal disease (MDRD) equation accounted for only 59.6% (P < 0.001) of the variance in GFRinu, whilst adding ALM explained an additional 10.4% variance (P < 0.001). If ALMI was entered first, the relationship between DA variables and GFRinu was reduced (for weight) or completely abolished (for age, gender and height). (ii) After inputting all the commonly used DA variables, 17.2% of the variance in ALM was unexplained. (iii) All the DA variables explained only 60.6% (P < 0.001) of the variance in Cr, whilst adding ALM explained an additional 4.2% variance (P < 0.005). Conclusions. Muscle mass explained more variance in GFRinu than MDRD DA variables and mediated the relationship between GFRinu and DA variables. Furthermore, DA variables failed to account for individual differences in muscle mass or Cr. Consequently, there is a need to validate simpler, clinically obtainable measures of muscle mass and determine whether these measures will improve GFR estimation. © Copyright 2006 Oxford University Press.

The aim of this study was to compare the effects of specific (small-sided games) vs. generic (running) aerobic interval training on physical fitness and objective measures of match performance in soccer. Forty junior players were randomly assigned to either generic (n = 20) or specific (n =20) interval training consisting of 4 bouts of 4 min at 90-95% of maximum heart rate with 3 min active rest periods, completed twice a week. The following outcomes were measured at baseline (Pre), after 4 weeks of pre-season training (Mid), and after a further 8 weeks of training during the regular season (Post): maximum oxygen uptake, lactate threshold (Tlac), running economy at Tlac, a soccer-specific endurance test (Ekblom's circuit), and indices of physical performance during soccer matches (total distance and time spent standing, walking, and at low- and high-intensity running speed). Training load, as quantified by heart rate and rating of perceived exertion, was recorded during all training sessions and was similar between groups. There were significant improvements in aerobic fitness and match performance in both groups of soccer players, especially in response to the first 4 weeks of pre-season training. However, no significant differences between specific and generic aerobic interval training were found in any of the measured variables including soccer specific tests. The results of this study showed that both small-sided games and running are equally effective modes of aerobic interval training in junior soccer players. © Georg Thieme Verlag KG.

Copyright © 2015 by the American College of Sports Medicine. Purpose: The purpose of the study was to investigate the effects of mental fatigue on intermittent running performance. Methods: Ten male intermittent team sports players performed two identical self-paced, intermittent running protocols. The two trials were separated by 7 d and preceded, in a randomized-counterbalanced order, by 90 min of either emotionally neutral documentaries (control) or the AX-continuous performance test (AX-CPT; mental fatigue). Subjective ratings of fatigue and vigor were measured before and after these treatments, and motivation was recorded before the intermittent running protocol. Velocity, heart rate, oxygen consumption, blood glucose and lactate concentrations, and ratings of perceived exertion (RPE) were measured throughout the 45-min intermittent running protocol. Session RPE was recorded 30 min after the intermittent running protocol. Results: Subjective ratings of fatigue were higher after the AX-CPT (P = 0.005). This mental fatigue significantly reduced velocity at low intensities (1.28 ± 0.18 m·s1 vs 1.31 ± 0.17 m·s-1; P = 0.037), whereas high-intensity running and peak velocities were not significantly affected. Running velocity at all intensities significantly declined over time in both conditions (P < 0.001). Oxygen consumption was significantly lower in the mental fatigue condition (P = 0.007). Other physiological variables, vigor and motivation, were not significantly affected. Ratings of perceived exertion during the intermittent running protocol were not significantly different between conditions despite lower overall velocity in the mental fatigue condition. Session RPE was significantly higher in the mental fatigue condition (P = 0.013). Conclusion: Mental fatigue impairs intermittent running performance. This negative effect of mental fatigue seems to be mediated by higher perception of effort.

Hemodialysis (HD) patients typically have reduced muscle mass and diminished functional capacity. The role of the muscle insulin-like growth factors (IGFs), a principal anabolic system that is involved in protein synthesis and that has downregulation that is implicated in muscle loss in animal models of uremia, has previously not been assessed in vivo in HD patients. Seventeen HD patients were compared cross-sectionally with 17 age-, sex-, and body mass index-matched healthy controls. Body composition was assessed by dual energy x-ray absorptiometry and bioelectrical impedance spectrometry; functional capacity by hand grip strength, quadriceps strength, and 30-second sit-to-stand test; systemic inflammation by tumor necrosis factor-α (TNF-α) and TNF receptor 1 (TNFR1); serum and muscle IGF-I and IGFBP-3 by radioimmunoassay; and fragmentation of serum IGFBP-3 by Western immunoblotting. Appendicular lean mass was significantly decreased in HD patients compared with controls (17.6 ± 0.9 versus 21.5 ± 1.5 kg, P

Purpose: The aim of this study was to test the effects of mental exertion involving response inhibition on pacing and endurance performance during a subsequent 5-km running time trial. Methods: After familiarization, 12 physically active subjects performed the time trial on a treadmill after two different cognitive tasks: (i) an incongruent Stroop task involving response inhibition (inhibition task) and (ii) a congruent Stroop task not involving response inhibition (control task). Both cognitive tasks were performed for 30 min. Results: Neither the inhibition nor the control task induced subjective feelings of mental fatigue. Nevertheless, time trial performance was impaired following the inhibition task (24.4 ± 4.9 min) compared to the control task (23.1 ± 3.8 min) because of a significant reduction in average running speed chosen by the subject. The response inhibition task did not affect pacing strategy, which was negative in both conditions. Heart rate and blood lactate responses to the time trial were not affected by the inhibition task, but subjects rated perceived exertion higher compared to the control condition (13.5 ± 1.3 vs 12.4 ± 1.3). Conclusion: These findings show for the first time that 30 min of mental exertion involving response inhibition reduces subsequent self-paced endurance performance despite no overt mental fatigue. The impairment in endurance performance observed after the incongruent Stroop task seems to be mediated by the higher perception of effort as predicted by the psychobiological model of endurance performance. © 2014 Springer-Verlag Berlin Heidelberg.

Since Noakes' controversial lecture on the central governor ([23][1]), brain regulation of endurance performance has been a hot topic in exercise physiology. In this series, Dr. Markus Amann argues that afferent feedback related to peripheral locomotor muscle fatigue is an important determinant of

Rheumatoid cachexia, a consequence of chronic inflammation, is a common feature of rheu‐ matoid arthritis (RA) [1]. It is characterised by reduced muscle mass and increased, predom‐ inantly truncal, adiposity, which in turn both contribute to physical weakness and disability [2,3]. Additionally, as in other catabolic conditions, these adverse changes in body compo‐ sition exacerbate risk of falls and fracturing, contribute to impaired physical disability and reduced quality of life, and increase morbidity and mortality [e.g. 4-6]. In RA, again as in other chronic conditions, these outcomes are most marked in severe forms of cachexia where there is frank weight loss with reductions in both lean and fat mass. This overt wasting has been estimated to occur in up to 10% of RA patients and is associated with a three-fold higher mortality [7].

Background: Fatigue is one of the most prevalent symptoms in chronic kidney disease (CKD). However, fatigue mechanisms are poorly understood due in part to nonspecific definitions. This study investigates exertional fatigue during simulated activities of daily living, focusing on oxygen delivery and utilization. Study Design: "Explanatory" matched-cohort study. Participants & Setting: 13 patients with CKD (stages 3b-4; mean age, 62 ± 13 [SD] years) and 13 healthy controls, mean matched for age, height, body mass and composition, and physical activity level. Participants completed an incremental cycle ergometer test to simulate energy expenditure of typical activities of daily living. Factor: 4 exercise intensities: 1, 1.8, 2.4, and 3.1 metabolic equivalent tasks (METs). Outcomes: The primary outcome was exertional fatigue by rating of perceived exertion (RPE) on a 6-20 scale. Measurements: Other multidimensional measures of fatigue: UK Short Form Health Survey 36 (UK SF-36) Vitality and Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) subscales. Physiologic measures of the oxygen transport and utilization chain (expired gas analysis, cardiac output, and arterial oxygen content) and blood lactate. Results: RPE was increased in patients compared with controls at 2.4 (10.5 [ie, light] ± 2.7 vs 8.7 [very light] ± 1.7 units) and 3.1 (12.5 [somewhat hard] ± 2.6 vs 10.2 [light] ± 1.7 units) METs (interaction P = 0.03), which was consistent with higher chronic fatigue in patients by both the UK SF-36 Vitality (P = 0.01) and FACIT-Fatigue (P = 0.004) subscales. Arterial oxygen content was decreased in patients (P = 0.001), but cardiac output and oxygen extraction ratio were unchanged, decreasing oxygen delivery (P = 0.04). Respiratory exchange ratio (P = 0.004) and blood lactate production (P = 0.002) were increased. Limitations: Those inherent to a matched-cohort study. Conclusions: Using a novel application of the outcome measure RPE, patients with non-dialysis-dependent CKD reported considerable exertional fatigue during simulated activities of daily living. Poor compensation for mild anemia contributed to this symptom. In addition to anemia, the entire oxygen transport chain needs to be targeted to treat fatigue in patients with CKD. © 2012 National Kidney Foundation, Inc.

Objective. Rheumatoid arthritis (RA) patients were reassessed for body composition and physical function mean - SD 39 - 6 months after commencing a randomized controlled trial involving 24 weeks of either high-intensity progressive resistance training (PRT) or low-intensity range of movement exercise (control) to determine whether the benefits of PRT (i.e., reduced fat mass [FM], increased lean mass [LM], and improved function) were retained. Methods. Nine PRT and 9 control subjects were reassessed for body composition (dual X-ray absorptiometry) and function (knee extensor strength, chair test, arm curl test, 50-foot walk) approximately 3 years after resuming normal activity following the exercise intervention. Results. At followup, PRT subjects remained significantly leaner than control subjects (P = 0.03), who conversely had accumulated considerable FM during the study period (approximately-1.0 kg versus +2.4 kg, PRT versus controls). PRT subjects also retained most of the improvement in walking speed gained from training (P = 0.03 versus controls at followup). In contrast, the PRT-induced gains in LM and strength-related function were completely lost. Data from the controls suggest that established and stable RA patients have similar rates of LM loss but elevated rates of FM accretion relative to age-matched sedentary non-RA controls. Conclusion. We found that long-term resumption of normal activity resulted in loss of PRT-induced improvements in LM and strength-related function, but substantial retention of the benefits in FM reduction and walking ability. The relatively long-term benefit of reduced adiposity, in particular, is likely to be clinically significant, as obesity is very prevalent among RA patients and is associated with their disability and exacerbated cardiovascular disease risk. © 2012, American College of Rheumatology.

to the editor: In their recent paper, Amann and colleagues ([1][1]) report an experiment in which they used a powerful analgesic, fentanyl, to block afferent feedback from Group III and IV neurons innervating the locomotor muscles. The authors investigated the effects of this experimental treatment

Continuous high glycemic load and inactivity challenge glucose homeostasis and fat oxidation. Hyperglycemia and high intramuscular glucose levels mediate insulin resistance, a precursor state of type 2 diabetes. The aim was to investigate whether a carbohydrate (CHO)-reduced diet combined with high-intensity interval training (HIIT) enhances the beneficial effects of the diet alone on insulin sensitivity and fat oxidation in obese individuals. Nineteen obese subjects underwent 14 days of CHO-reduced and energy-restricted diet. Ten of them combined the diet with HIIT (4 min bouts at 90% VO 2peak up to 10 times, 3 times a week). Oral glucose insulin sensitivity (OGIS) increased significantly in both groups; [diet-exercise (DE) group: pre 377 ± 70, post 396 ± 68 mL min-1 m -2; diet (D) group: pre 365 ± 91, post 404 ± 87 mL min-1 m-2; P < 0.001]. Fasting respiratory exchange ratio (RER) decreased significantly in both groups (DE group: pre 0.91 ± 0.06, post 0.88 ± 0.06; D group: pre 0.92 ± 0.07, post 0.86 ± 0.07; P = 0.002). VO2peak increased significantly in the DE group (pre 27 ± 5, post 32 ± 6 mL kg-1 min -1; P < 0.001), but not in the D group (pre 26 ± 9, post 26 ± 8 mL kg-1 min-1). Lean mass and resistin were preserved only in the DE group (P < 0.05). Fourteen days of CHO-reduced diet improved OGIS and fat oxidation (RER) in obese subjects. The energy-balanced HIIT did not further enhance these parameters, but increased aerobic capacity (VO2peak) and preserved lean mass and resistin. © 2010 Springer-Verlag.

In exercise physiology, it has been traditionally assumed that high-intensity aerobic exercise stops at the point commonly called exhaustion because fatigued subjects are no longer able to generate the power output required by the task despite their maximal voluntary eVort. We tested the validity of this assumption by measuring maximal voluntary cycling power before (mean ± SD, 1,075 ± 214 W) and immediately after (731 ± 206 W) (P < 0.001) exhaustive cycling exercise at 242 ± 24 W (80% of peak aerobic power measured during a preliminary incremental exercise test) in ten Wt male human subjects. Perceived exertion during exhaustive cycling exercise was strongly correlated (r = -0.82, P = 0.003) with time to exhaustion (10.5 ± 2.1 min). These results challenge the long-standing assumption that muscle fatigue causes exhaustion during high-intensity aerobic exercise, and suggest that exercise tolerance in highly motivated subjects is ultimately limited by perception of effort. Copyright © Springer-Verlag 2010.

perception of effort, also known as perceived exertion or sense of effort, is a major feature of fatigue ([7][1]), and it is widely used to monitor and prescribe exercise intensity ([18][2]). However, despite its importance, the neurophysiological bases of this atypical sensation are poorly

Purpose: Surface electromyographic (EMG) variables allow study of the electrical activity of motor units within active skeletal muscle. Recent methodological advances permit the estimation of muscle fiber-conduction velocity (MFCV) from EMG signals recorded during dynamic exercise. However, EMG responses to incremental and fatiguing cycling are poorly understood. Methods: Twenty males completed an incremental cycling protocol (20, 40, 60, and 80% of peak power output (PPO)) on two occasions separated by 5 d. The final stage was 6 min long, to induce muscle fatigue. EMG signals were recorded from the vastus lateralis and vastus medialis muscles, and root mean square (RMS) and MFCV values were estimated. Results: For incremental exercise, EMG data were reliable between trials, especially for MFCV in the vastus lateralis at 40, 60, and 80% PPO (e.g., coefficient of variation < 6.3%; bias < 0.4 m[middle dot]s-1; limits of agreement < 1.2 m[middle dot]s-1). Significant positive correlations were observed between RMS and MFCV (r = 0.79-0.83), as both measures increased with power output (repeated-measures analysis of variance all P = 0.001). For fatiguing exercise, many EMG variables showed systematic bias between trials. RMS (P = 0.009 to 0.051) but not MFCV (P = 0.236-0.578) significantly increased during fatiguing cycling. Conclusions: During dynamic cycle exercise, EMG variables are reliable and increase with power output. During fatiguing exercise, EMG variables may be sensitive to learning effects in the execution of the task. MFCV and RMS are correlated with varying power output in the nonfatigued muscle, but not during the development of fatigue

OBJECTIVE Patients with systemic lupus erythematosus (SLE) have poor physical fitness as measured by maximal oxygen uptake (VO(2max)), which is associated with disability and fatigue. The purpose of this study was to validate, in this population, the Siconolfi Step Test (SST) developed to predict VO(2max) in healthy individuals. METHODS Thirty patients with well-controlled SLE were tested on a cycle ergometer until volitional exhaustion, and 25 women and 4 men (mean +/- SD age 48 +/- 14 years, weight 71.5 +/- 13.7 kg) fulfilled the criteria for maximal effort. VO(2max) measured during this incremental test was compared with VO(2max) predicted by the SST using Bland and Altman 95% limits of agreement (LOA) and intraclass correlation coefficient (ICC). The SST was repeated twice to assess its reliability. RESULTS The ICC between predicted and measured VO(2max) (mean +/- SD 1.67 +/- 0.41 liters/minute versus 1.57 +/- 0.39 liters/minute) was moderately high (0.73, P < 0.001). Bland and Altman analysis revealed a trend for a positive bias (P = 0.083) and 95% LOA of +/-0.58 liters/minute. There was a very high ICC (0.97, P < 0.001) between VO(2max) predicted by the first and second SST (mean +/- SD 1.66 +/- 0.40 liters/minute versus 1.67 +/- 0.41 liters/minute), and no significant bias (P = 0.500). The 95% LOA were +/-0.20 liters/minute. CONCLUSION The results demonstrate that the SST is well tolerated, reasonably valid, and highly reliable in patients with well-controlled SLE. Therefore, this simple, submaximal exercise test might be useful for assessing physical fitness in clinical practice and epidemiologic studies.

PURPOSE: To establish the validity and reliability of a new vertical jump force test (VJFT) for the assessment of bilateral strength asymmetry in a total of 451 athletes. METHODS: The VJFT consists of countermovement jumps with both legs simultaneously: one on a single force platform, the other on a leveled wooden platform. Jumps with the right or the left leg on the force platform were alternated. Bilateral strength asymmetry was calculated as [(stronger leg - weaker leg)/stronger leg] × 100. A positive sign indicates a stronger right leg; a negative sign indicates a stronger left leg. Studies 1 (N = 59) and 2 (N = 41) examined the correlation between the VJFT and other tests of lower-limb bilateral strength asymmetry in male athletes. In study 3, VJFT reliability was assessed in 60 male athletes. In study 4, the effect of rehabilitation on bilateral strength asymmetry was examined in seven male and female athletes 8-12 wk after unilateral knee surgery. In study 5, normative data were determined in 313 male soccer players. RESULTS: Significant correlations were found between VJFT and both the isokinetic leg extension test (r = 0.48; 95% confidence interval, 0.26-0.66) and the isometric leg press test (r = 0.83; 0.70-0.91). VJFT test-retest intraclass correlation coefficient was 0.91 (0.85-0.94), and typical error was 2.4%. The change in mean [-0.40% (-1.25 to 0.46%)] was not substantial. Rehabilitation decreased bilateral strength asymmetry (mean ± SD) of the athletes recovering from unilateral knee surgery from 23 ± 3 to 10 ± 4% (P < 0.01). The range of normal bilateral strength asymmetry (2.5th to 97.5th percentiles) was -15 to 15%. CONCLUSIONS: The assessment of bilateral strength asymmetry with the VJFT is valid and reliable, and it may be useful in sports medicine. ©2007The American College of Sports Medicine.