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Background: Type 1 diabetic patients and non-diabetic patients were referred for evaluation for chronic exertional compartment syndrome (CECS) based on clinical examination and complaints of activity-related leg pain in the region of the tibialis anterior muscle. Previous studies using near-infrared spectroscopy (NIRS) showed greater deoxygenation during exercise for CECS patients versus healthy controls; however, this comparison has not been done for diabetic CECS patients., Methods: We used NIRS to test for differences in oxygenation kinetics for Type 1 diabetic patients diagnosed with (CECS-diabetics, n = 9) versus diabetic patients without (CON-diabetics, n = 10) leg anterior chronic exertional compartment syndrome. Comparisons were also made between non-diabetic CECS patients (n = 11) and healthy controls (CON, n = 10). The experimental protocol consisted of thigh arterial cuff occlusion (AO, 1-minute duration), and treadmill running to reproduce symptoms. NIRS variables generated were resting StO2%, and oxygen recovery following AO. Also, during and following treadmill running the magnitude of deoxygenation and oxygen recovery, respectively, were determined., Results: There was no difference in resting StO2% between CECS-diabetics (78.2±12.6%) vs. CON-diabetics (69.1±20.8%), or between CECS (69.3±16.2) vs. CON (75.9±11.2%). However, oxygen recovery following AO was significantly slower for CECS (1.8±0.8%/sec) vs. CON (3.8±1.7%/sec) (P = 0.002); these data were not different between the diabetic groups. StO2% during exercise was lower (greater deoxygenation) for CECS-diabetics (6.3±8.6%) vs. CON-diabetics (40.4±22.0%), and for CECS (11.3±16.8%) vs. CON (34.1±21.2%) (P<0.05 for both). The rate of oxygen recovery post exercise was faster for CECS-diabetics (3.5±2.6%/sec) vs. CON-diabetics (1.4±0.8%/sec) (P = 0.04), and there was a tendency of difference for CECS (3.1±1.4%/sec) vs. CON (1.9±1.3%/sec) (P = 0.05)., Conclusion: The greater deoxygenation during treadmill running for the CECS-diabetics group (vs. CON-diabetics) is in line with previous studies (and with the present study) that compared non-diabetic CECS patients with healthy controls. Our findings could suggest that NIRS may be useful as a diagnostic tool for assessing Type 1 diabetic patients suspected of CECS.

Patients suffering from work-related muscle pain (WRMP) fatigue earlier during exercise than healthy controls. Inadequate oxygen consumption and/or inadequate blood supply can influence the ability of the muscles to withstand fatigue. However, it remains unknown if oxygenation and hemodynamics are associated with early fatigue in muscles of WRMP patients. In the present study we applied near-infrared spectroscopy (NIRS) on the extensor carpi radialis (ECR) and trapezius (TD) muscles of patients with WRMP (n = 18) and healthy controls (n = 17). Our objective was to determine if there were group differences in endurance times for a low-level contraction of 15% maximal voluntary contraction (MVC)--sustained for 12-13 min, and to see if these differences were associated with differences in muscle oxygenation and hemodynamics. At baseline, oxygen saturation (StO2%) was similar between groups for the ECR, but StO2% was significantly lower for TD for the WRMP patients (76%) compared to controls (85%) (P<0.01). Also, baseline ECR blood flow was similar in the two groups. For both muscles there were a larger number of patients, compared to controls, that did not maintain the 15% MVC for the allotted time. Consequently, the endurance times were significantly shorter for the WRMP patients than controls (medians, ECR: 347 s vs. 582 s; TD: 430 s vs. 723 s respectively). Responses in StO2% during the contractions were not significantly different between groups for either muscle, i.e. no apparent difference in oxygen consumption. Overall, we interpret our findings to indicate that the early fatigue for our WRMP patients was not associated with muscle oxygenation and hemodynamics.

To investigate whether myofascial reorganization® in the trapezius muscle (MRT) improves peripheral muscle oxygenation and pain tolerance and decreases neck disability index (NDI) scores in individuals with and without nonspecific neck pain (NP) using a double-blind randomized controlled trial. Seventy-five subjects were equally and randomly assigned to three groups: the intervention groups (experimental [EG] and sham sSG]) and the control group (CG). Several inclusion criteria were applied to the intervention groups: male or female, aged 18–32 years, self-reported NP in the last 3 months without a defined cause; at least "soft" pain in session 1 of the NDI, and at least a score of 1 on the Visual Analogue Scale (VAS). The CG was required to have NDI and VAS scores of 0 at recruitment. Intervention: The EG underwent MRT for 10 min, once a week for 6 weeks. Patients with NP in the SG underwent classical massage for the same duration and frequency. Patients in the CG had no pain and underwent no intervention. Data collection was performed using the NDI Questionnaire, a pressure algometer for pain evaluation, and near-infrared spectroscopy for muscle oxygenation measurements. It was registered as NCT03882515 at ClinicalTrials.gov. The NDI score in both the EG (p<0.001) and SG (p<0.001) decreased after 6 weeks of intervention compared to the CG. The CG demonstrated a lower basal tissue saturation (TSI) index than the EG (p<0.001) and SG (p = 0.02). The EG demonstrated higher oxyhemoglobin values than the SG (p<0.001) and CG (p = 0.03). The CG had higher pain tolerance than the EG (p = 0.01) and SG (p<0.001) post-intervention. MRT increased trapezius muscle oxygenation after 6 weeks of intervention. [ABSTRACT FROM AUTHOR]

Purpose: This study examined changes in circulating levels of inflammatory cytokines [IL-6, sIL-6R, TNF-α, and calprotectin], skeletal muscle morphology, and muscle strength following a 50km race in non-elite athletes. Methods: Eleven individuals (8 men; 3 women) underwent pre-race assessments of rectus femoris muscle thickness (resting and contracted) using ultrasound, isometric knee extensor torque, and plasma cytokines. Measures were repeated after 10km of running, the 50km finish (post-race), and again 24-hrs post-race. Results: Compared with baseline values, Δ muscle thickness (resting to contracted) increased significantly 24 hrs post-race (11 ± 11% vs. 22 ± 8%; P = 0.01). Knee extensor torque was significantly reduced immediately post-race (151 ± 46 vs. 134 ± 43 Nm; P = 0.047) but remained similar to post-race values at 24 hrs post-race (P = 0.613). Compared with pre-race levels, IL-6 and calprotectin concentrations increased 302% and 50% after 10km, respectively (P<0.017 for both), peaked post-race (2598% vs. pre-race for IL-6 and 68% vs. pre-race for calprotectin; P = 0.018 for both), and returned to pre-race levels at 24-hrs post-race (P>0.05 for both). Creatine kinase levels rose steadily during and after the race, peaking 24-hrs post-race (184 ± 113 U/L pre-race vs. 1508 ± 1815 U/L 24-hrs post-race; P = 0.005). Conclusion: This is the first report of delayed increases in Δ muscle thickness at 24 hrs post-50km, which are preceded by reductions in knee extensor torque and elevations in plasma IL-6, and calprotectin. Recreational athletes should consider the acute muscle inflammatory response when determining training and recovery strategies for 50km participation. [ABSTRACT FROM AUTHOR]

Somatic symptom disorder, illness anxiety disorder, and functional syndromes are characterized by burdensome preoccupation with somatic symptoms. Etiological models propose either increased interoceptive accuracy through hypervigilance to the body, or decreased and biased interoception through top-down predictions about sensory events. This systematic review and meta-analysis summarizes findings of 68 studies examining interoceptive accuracy and 8 studies examining response biases in clinical or non-clinical groups. Analyses yielded a medium population effect size for decreased interoceptive accuracy in functional syndromes, but no observable effect in somatic symptom disorder and illness anxiety disorder. The overall effect size was highly heterogeneous. Regarding response bias, there was a small significant effect in somatic symptom disorder and illness anxiety disorder. Our findings strengthen the notion of top-down factors that result in biased rather than accurate perception of body signals in somatic symptom disorder and illness anxiety disorder. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this review was to (1) characterize the time-course of markers of exercise-induced muscle damage (EIMD) based on the level of maximal voluntary contraction torque loss at 24-48h post-exercise (MVCloss24-48h), (2) identify factors (e.g., exercise and population characteristics) affecting the level of MVCloss24-48h, and (3) evaluate the appropriateness of EIMD markers as indicators of MVCloss24-48h. Methods: Magnitude of change of each EIMD markers was normalized using the standardized mean differences method to compare the results from different studies. Time-course of EIMD markers were characterized according to three levels of MVCloss24-48h based on a clustering analysis of the 141 studies included. Association between MVCloss24-48h levels and participant´s characteristics or exercise type/modalities were assessed. Meta-regressions were performed to investigate the associations between MVCloss24-48h and EIMD markers changes at <6h, 24h, 48h, 72h and >96h after exercise. Results: Time-course of EIMD markers recovery differs between levels of MVCloss24-48h. Training status and exercise type/modality were associated with MVCloss24-48h level (p<0.05). MVCloss24-48h was correlated to changes in myoglobin concentration (<6h), jump height (24h) and range of motion (48h) (p<0.001). Conclusion: As the exercise could differently affect markers as function of the EIMD severity (i.e., MVCloss24-48h levels), different markers should be used as function of the timing of measurement. Mb concentration should be used during the first hours after the exercise (<6h), whereas jump height (24h) and range of motion (48h) could be used as surrogate for maximal voluntary contraction later. Moreover, training status and exercise type/modality could influence the magnitude of MVCloss24-48h. [ABSTRACT FROM AUTHOR]

Background: The purpose of this review was to systematically analyze the evidence regarding the occurrence of muscle damage (changes in muscle damage markers) after resistance training with blood flow restriction sessions. Materials and methods: This systematic review was conducted in accordance with the PRISMA recommendations. Two researchers independently and blindly searched the following electronic databases: PubMed, Scopus, Web of Science, CINAHL, LILACS and SPORTdicus. Randomized and non-randomized clinical trials which analyzed the effect of resistance training with blood flow restriction on muscle damage markers in humans were included. The risk of bias assessment was performed by two blinded and independent researchers using the RoB2 tool. Results: A total of 21 studies involving 352 healthy participants (men, n = 301; women, n = 51) were eligible for this review. The samples in 66.6% of the studies (n = 14) were composed of untrained individuals. All included studies analyzed muscle damage using indirect markers. Most studies had more than one muscle damage marker and Delayed Onset Muscle Soreness was the measure most frequently used. The results for the occurrence of significant changes in muscle damage markers after low-load resistance training with blood flow restriction sessions were contrasting, and the use of a pre-defined repetition scheme versus muscle failure seems to be the determining point for this divergence, mainly in untrained individuals. Conclusions: In summary, the use of sets until failure is seen to be determinant for the occurrence of significant changes in muscle damage markers after low-load resistance training with blood flow restriction sessions, especially in individuals not used to resistance exercise. Trial registration: Register number: PROSPERO number: CRD42020177119. [ABSTRACT FROM AUTHOR]

Current literature suggests that greater than 50% of survivors of a stroke cannot accurately perceive where their upper extremity is positioned. Our recent work demonstrates that the extent to which this perception is affected can depend on how the task is performed. For example, individuals with stroke who have a deficit in mirroring the position of their passively-placed paretic forearm during a between-arms task may accurately reproduce the position of their actively-controlled paretic forearm during a single-arm task. Moreover, the ability of individuals with various types of unilateral lesions to locate their thumb can depend on whether they reach for their paretic thumb or non-paretic thumb. Consequently, we investigated to what extent the accuracy of individuals post-hemiparetic stroke in mirroring forearm positions on a between-arms task is influenced by various conditions. Eighteen participants with hemiparetic stroke rotated their reference forearm to a target position, and then rotated their opposite forearm to concurrently mirror the position of their reference forearm. This task was performed when participants referenced each forearm (paretic, non-paretic) at two target positions (extension, flexion) for two modes of limb control (passive, active). We quantified for every testing scenario of each participant their position-mirroring error. The number of times for which participants were classified as having a deficit was least when mirroring forearm positions at the flexed position when referencing their non-paretic forearm. Additionally, the difference in the magnitude of errors when participants referenced each arm was greater during active than passive movements. Findings from this study provide further evidence that the accuracy with which individuals post stroke perceive the position of their limbs can depend on how a task is performed. Factors to consider include whether movements are active versus passive, which limb is referenced, and where the limb is positioned. [ABSTRACT FROM AUTHOR]

Background: Upper body motor function and swallowing may be affected after curative treatment for head and neck cancer. The aims of this study are to compare maximum mouth opening (MMO), temporomandibular dysfunction (TMD), cervical and shoulder active range of motion (AROM) and strength, and swallowing difficulty between survivors of head and neck cancer (sHNC) and healthy matched controls (HMC) and to examine the correlations between these outcomes in sHNC. Methods: Thirty-two sHNC and 32 HMC participated on the study. MMO, TMD, cervical and shoulder AROM, cervical and shoulder strength, the SPADI shoulder pain and disability indices, the Eating Assessment Tool (EAT-10) score, swallowing difficulty as determined using a visual analogue scale (VAS), and the location of disturbances in swallowing, were recorded. Results: MMO and cervical and shoulder AROM and strength were significantly lower in sHNC, whereas FAI, SPADI score, EAT-10 and VAS were higher. The MMO, TMD, cervical and shoulder AROM, and cervical shoulder strength values showed significant correlations (some direct, others inverse) with one another. Swallowing difficulty was inversely associated with the MMO, cervical AROM and shoulder strength. Conclusion: Compared with controls, sHNC present smaller MMO, lower cervical and shoulder AROM, lower cervical and shoulder strength and higher perception of TMD, shoulder pain and disability and swallowing difficulty. sHNC suffer impaired swallowing related to lower MMO, presence of TMD, cervical AROM and shoulder strength values. Improving these variables via physiotherapy may reduce the difficulty in swallowing experienced by some sHNC. [ABSTRACT FROM AUTHOR]

Proper ankle motor control is critical for balance in the human body during functional activities such as standing, walking, and running. Different exercise modalities are often performed during the same training session where earlier activities may influence later ones. The purpose of the current study was to determine the acute effects of different exercise modalities on ankle force sense. Seventeen subjects performed four different intervention protocols (static stretching, balance task, concentric contractions, and control) in random order. Each session comprised measurements before and after the intervention protocol of the force sense of the ankle plantar flexors (PF) and dorsal flexors (DF) at 10% and 30% of maximal voluntary isometric contraction (MVC). Absolute errors (AE) were calculated separately for each force level and muscle group. An overall PF error (PF-SUM = PF at 10%MVC + PF at 30%MVC), DF error (DF-SUM = DF at 10%MVC + DF at 30%MVC) and ankle error (PF-DF-SUM = PF-SUM + DF-SUM) were also calculated. The main effect of time generally revealed that ankle force sense was significantly reduced after static stretching (PF-DF-SUM: Pre: 6.11±2.17 Nm, Post: 8.03±3.28 Nm; p < 0.05), but no significant differences were observed for the concentric contractions (PF-DF-SUM: Pre: 6.01±1.97 Nm, Post: 6.50±2.28 Nm) and the balance task (PF-DF-SUM: Pre: 5.25±1.97 Nm, Post: 5.50±1.26 Nm). The only significant interaction was observed for the PF-DF-SUM (F = 4.48, p = 0.008) due to greater error scores after stretching (+31.4%) compared to the concentric (+8.2%), balance (+4.8%), and control (-3.5%) conditions. Based on these results, static stretching should not be performed before activities that require a high ankle force sense such as balance, coordination, and precision tasks. [ABSTRACT FROM AUTHOR]

Objective: We aimed to investigate the correlations between Upper Extremity Musculoskeletal Symptoms (MSD) and joint kinematics while playing the piano, as well as correlations between MSD and psychosocial, professional and personal habits, and bio-demographic risk factors of piano students. Method: This cross-sectional study included 15 piano students. The research tools included 3D motion capture, anthropometric measurements, and questionnaires for obtaining data about MSD, psychological, and personal factors. Results: The piano students recruited for this study experienced a variety of MSD during the past 12 months, with a particularly high prevalence of neck pain (80%). Extreme wrist extension and/or elbow flexion while playing the piano also correlated with MSD. Additionally, this study identified correlations between MSD and hand span (r = -.69, p≤.004) and number of playing hours per week (r = .58, p≤.024). Conclusions: Anthropometric factors and playing patterns should be considered together with well-known MSD risk factors, like extreme and repetitive movements. However, considering each joint singularly might not be sufficient to prevent the development of MSD when instructing the piano player; accordingly, joint synchronization should also be considered. [ABSTRACT FROM AUTHOR]

Background: According to between-arms assessments, more than 50% of individuals with stroke have an impaired position sense. Our previous work, which employed a clinical assessment and slightly differing tasks, indicates that individuals who have a deficit on a between-forearms position-localization task do not necessarily have a deficit on a single-forearm position-localization task. Objective: Our goal here was to, using robotics tools, determine whether individuals with stroke who have a deficit when matching forearm positions within an arm also have a deficit when mirroring forearm positions between arms, independent of the arm that leads the task. Methods: Eighteen participants with chronic hemiparetic stroke and nine controls completed a single-arm position-matching experiment and between-arms position-mirroring experiment. For each experiment, the reference forearm (left/right) passively rotated about the elbow joint to a reference target location (flexion/extension), and then the participant actively rotated their same/opposite forearm to match/mirror the reference forearm’s position. Participants with stroke were classified as having a position-matching/-mirroring deficit based on a quantitative threshold that was derived from the controls’ data. Results: On our single-arm task, one participant with stroke was classified as having a position-matching deficit with a mean magnitude of error greater than 10.7° when referencing their paretic arm. Position-matching ability did not significantly differ for the controls and the remaining seventeen participants with stroke. On our between-arms task, seven participants with stroke were classified as having a position-mirroring deficit with a mean magnitude of error greater than 10.1°. Position-mirroring accuracy was worse for these participants with stroke, when referencing their paretic arm, than the controls. Concluding remark: Findings underscore the need for assessing within-arm position-matching deficits, in addition to between-arms position-mirroring deficits when referencing each arm, to comprehensively evaluate an individual’s ability to locate their forearm(s). [ABSTRACT FROM AUTHOR]

The study aimed to compare the chronic eccentric-overload training effects of unilateral (lateral lunge) vs bilateral (half-squat) using an inertial device, on hypertrophy and physical performance. Twenty-seven young team sports male players performed a 4 sets of 7 repetitions of inertial eccentric overload training, biweekly for 6 weeks, distributed in unilateral lunge group (UG: age: 22.8 ± 2.9 years; body mass: 75.3 ± 8.8 kg; height: 177.3 ± 3.7 cm) and bilateral squat group (BG: age: 22.6 ± 2.7 years; body mass: 79.5 ± 12.8 kg; height: 164.2 ± 7 cm). Lower limb muscle volume, counter movement jump (CMJ), power with both (POWER), dominant (POWERd) and no-dominant leg (POWERnd), change of direction turn of 90° with dominant (COD90d) and no-dominant leg (COD90nd) and 180° (COD180d and COD180nd), and 10m sprint time (T-10m) were measured pre and post-intervention. The UG obtained an increase of adductor major (+11.1%) and vastus medialis (+12.6%) higher than BG. The BG obtained an increase of vastus lateralis (+9.9%) and lateral gastrocnemius (+9.1%) higher than UG. Both groups improved CMJ, POWER, POWERd, POWERnd, COD90 and DEC-COD90, without changes in T-10m. The UG decrease DEC-COD90nd (-21.1%) and BG increase POWER (+38.6%) substantially more than the other group. Six-weeks of unilateral / bilateral EO training induce substantial improvements in lower limbs muscle volume and functional performance, although unilateral training seems to be more effective in improving COD90 performance. [ABSTRACT FROM AUTHOR]

The purpose of the study was to examine the acute effects of different dynamic exercise interventions on hamstring muscle performance. Thirty-six young men with poor hamstring flexibility were randomly assigned to three intervention groups: jogging combined with dynamic open kinetic chain stretching (DS), jogging combined with dynamic closed kinetic chain stretching (lunge with eccentric hamstring windmills, LEC), and jogging only (CON) groups. Hamstring flexibility, muscle stiffness (area under the curve, AUC), joint position sense (JPS), maximal eccentric strength (ECC), and angle of peak torque (APT) were recorded before and immediately after the exercise interventions. The results showed that the hamstring flexibility increased in DS (p < 0.001); muscle stiffness decreased in DS and was lower than jogging (p < 0.001). Moreover, ECC increased in LEC and was higher than jogging and DS (p < 0.001). APT was different among 3 groups (p < 0.001). Decreased accuracy of JPS was found in DS and jogging (p < 0.001). In conclusion, the dynamic closed kinetic chain stretching (LEC) as compared to open kinetic chain stretching (DS) or jogging group, may be an effective technique to enhance muscle performance during the pre-competition warm-up routine. [ABSTRACT FROM AUTHOR]

Proprioceptive signals from peripheral mechanoreceptors form the basis for bodily perception and are known to be essential for motor control. However we still have an incomplete understanding of how proprioception differs between joints, whether it differs among the various degrees-of-freedom (DoFs) within a particular joint, and how such differences affect motor control and learning. We here introduce a robot-aided method to objectively measure proprioceptive function: specifically, we systematically mapped wrist proprioceptive acuity across the three DoFs of the wrist/hand complex with the aim to characterize the wrist position sense. Thirty healthy young adults performed an ipsilateral active joint position matching task with their dominant wrist using a haptic robotic exoskeleton. Our results indicate that the active wrist position sense acuity is anisotropic across the joint, with the abduction/adduction DoF having the highest acuity (the error of acuity for flexion/extension is 4.64 ± 0.24°; abduction/adduction: 3.68 ± 0.32°; supination/pronation: 5.15 ± 0.37°) and they also revealed that proprioceptive acuity decreases for smaller joint displacements. We believe this knowledge is imperative in a clinical scenario when assessing proprioceptive deficits and for understanding how such sensory deficits relate to observable motor impairments. [ABSTRACT FROM AUTHOR]

Background: People with multiple sclerosis (MS) are encouraged to engage in exercise programs but an increased experience of fatigue may impede sustained participation in training sessions. A high number of movements is, however, needed for obtaining optimal improvements after rehabilitation. Methods: This cross-sectional study investigated whether people with MS show abnormal fatigability during a robot-mediated upper limb movement trial. Sixteen people with MS and sixteen healthy controls performed five times three minutes of repetitive shoulder anteflexion movements. Movement performance, maximal strength, subjective upper limb fatigue and surface electromyography (median frequency and root mean square of the amplitude of the electromyography (EMG) signal of the anterior deltoid) were recorded during or in-between these exercises. After fifteen minutes of rest, one extra movement bout was performed to investigate how rest influences performance. Results: A fifteen minutes upper limb movement protocol increased the perceived upper limb fatigue and induced muscle fatigue, given a decline in maximal anteflexion strength and changes of both the amplitude and the median frequency of EMG the anterior deltoid. In contrast, performance during the 3 minutes of anteflexion movements did not decline. There was no relation between changes in subjective fatigue and the changes in the amplitude and the median frequency of the anterior deltoid muscle, however, there was a correlation between the changes in subjective fatigue and changes in strength in people with MS. People with MS with upper limb weakness report more fatigue due to the repetitive movements, than people with MS with normal upper limb strength, who are comparable to healthy controls. The weak group could, however, keep up performance during the 15 minutes of repetitive movements. Discussion and Conclusion: Albeit a protocol of repetitive shoulder anteflexion movements did not elicit a performance decline, fatigue feelings clearly increased in both healthy controls and people with MS, with the largest increase in people with MS with upper limb weakness. Objective fatigability was present in both groups with a decline in the muscle strength and increase of muscle fatigue, shown by changes in the EMG parameters. However, although weak people with multiple sclerosis experienced more fatigue, the objective signs of fatigability were less obvious in weak people with MS, perhaps because this subgroup has central limiting factors, which influence performance from the start of the movements. [ABSTRACT FROM AUTHOR]

Purpose: Over the past decade, linear and non-linear surface electromyography descriptors for central and peripheral components of fatigue have been developed. In the current study, we tested fractal dimension (FD) and conduction velocity (CV) as myoelectric descriptors of central and peripheral fatigue, respectively. To this aim, we analyzed FD and CV slopes during sustained fatiguing contractions of the quadriceps femoris in healthy humans. Methods: A total of 29 recreationally active women (mean age±standard deviation: 24±4 years) and two female elite athletes (one power athlete, age 24 and one endurance athlete, age 30 years) performed two knee extensions: (1) at 20% maximal voluntary contraction (MVC) for 30 s, and (2) at 60% MVC held until exhaustion. Surface EMG signals were detected from the vastus lateralis and vastus medialis using bidimensional arrays. Results: Central and peripheral fatigue were described as decreases in FD and CV, respectively. A positive correlation between FD and CV (R=0.51, p<0.01) was found during the sustained 60% MVC, probably as a result of simultaneous motor unit synchronization and a decrease in muscle fiber CV during the fatiguing task. Conclusions: Central and peripheral fatigue can be described as changes in FD and CV, at least in young, healthy women. The significant correlation between FD and CV observed at 60% MVC suggests that a mutual interaction between central and peripheral fatigue can arise during submaximal isometric contractions. [ABSTRACT FROM AUTHOR]

This study examined the effects of Sprint Interval Cycling (SIT) on muscle oxygenation kinetics and performance during the 30-15 intermittent fitness test (IFT). Twenty-five women hockey players of Olympic standard were randomly selected into an experimental group (EXP) and a control group (CON). The EXP group performed six additional SIT sessions over six weeks in addition to their normal training program. To explore the potential training-induced change, EXP subjects additionally completed 5 x 30s maximal intensity cycle testing before and after training. During these tests near-infrared spectroscopy (NIRS) measured parameters; oxyhaemoglobin + oxymyoglobin (HbO2+ MbO2), tissue deoxyhaemoglobin + deoxymyoglobin (HHb+HMb), total tissue haemoglobin (tHb) and tissue oxygenation (TSI %) were taken. In the EXP group (5.34±0.14 to 5.50±0.14m.s-1) but not the CON group (pre = 5.37±0.27 to 5.39±0.30m.s-1) significant changes were seen in the 30-15IFT performance. EXP group also displayed significant post-training increases during the sprint cycling: ΔTSI (−7.59±0.91 to −12.16±2.70%); ΔHHb+HMb (35.68±6.67 to 69.44±26.48μM.cm); and ΔHbO2+ MbO2 (−74.29±13.82 to −109.36±22.61μM.cm). No significant differences were seen in ΔtHb (−45.81±15.23 to −42.93±16.24). NIRS is able to detect positive peripheral muscle oxygenation changes when used during a SIT protocol which has been shown to be an effective training modality within elite athletes. [ABSTRACT FROM AUTHOR]

Experience of stress may lead to increased electromyography (EMG) activity in specific muscles compared to a non-stressful situation. The main aim of this study was to develop and validate a stress-EMG paradigm in which a single uncontrollable and unpredictable nociceptive stimulus was presented. EMG activity of the trapezius muscles was the response of interest. In addition to linear time effects, non-linear EMG time courses were also examined. Taking into account the hierarchical structure of the dataset, a multilevel random regression model was applied. The stress paradigm, executed in N = 70 subjects, consisted of a 3-minute baseline measurement, a 3-minute pre-stimulus stress period and a 2-minute post-stimulus phase. Subjects were unaware of the precise moment of stimulus delivery and its intensity level. EMG activity during the entire experiment was conform a priori expectations: the pre-stimulus phase showed a significantly higher mean EMG activity level compared to the other two phases, and an immediate EMG response to the stimulus was demonstrated. In addition, the analyses revealed significant non-linear EMG time courses in all three phases. Linear and quadratic EMG time courses were significantly modified by subjective anticipatory stress level, measured just before the start of the stress task. Linking subjective anticipatory stress to EMG stress reactivity revealed that subjects with a high anticipatory stress level responded with more EMG activity during the pre-stimulus stress phase, whereas subjects with a low stress level showed an inverse effect. Results suggest that the stress paradigm presented here is a valid test to quantify individual differences in stress susceptibility. Further studies with this paradigm are required to demonstrate its potential use in mechanistic clinical studies. [ABSTRACT FROM AUTHOR]

The prevalence of chronic trapezius myalgia is high in women with high exposure to awkward working positions, repetitive movements and movements with high precision demands. The mechanisms behind chronic trapezius myalgia are not fully understood. The purpose of this study was to explore the differences in protein content between healthy and myalgic trapezius muscle using proteomics. Muscle biopsies from 12 female cleaners with work-related trapezius myalgia and 12 pain free female cleaners were obtained from the descending part of the trapezius. Proteins were separated with two-dimensional differential gel electrophoresis (2D-DIGE) and selected proteins were identified with mass spectrometry. In order to discriminate the two groups, quantified proteins were fitted to a multivariate analysis: partial least square discriminate analysis. The model separated 28 unique proteins which were related to glycolysis, the tricaboxylic acid cycle, to the contractile apparatus, the cytoskeleton and to acute response proteins. The results suggest altered metabolism, a higher abundance of proteins related to inflammation in myalgic cleaners compared to healthy, and a possible alteration of the contractile apparatus. This explorative proteomic screening of proteins related to chronic pain in the trapezius muscle provides new important aspects of the pathophysiology behind chronic trapezius myalgia. [ABSTRACT FROM AUTHOR]

The results regarding the effects of unaccustomed eccentric exercise on muscle tissue are often conflicting and the aetiology of delayed onset muscle soreness (DOMS) induced by eccentric exercise is still unclear. This study aimed to re-evaluate the paradigm of muscular alterations with regard to muscle sarcolemma integrity and fibre swelling in human muscles after voluntary eccentric exercise leading to DOMS. Ten young males performed eccentric exercise by downstairs running. Biopsies from the soleus muscle were obtained from 6 non-exercising controls, 4 exercised subjects within 1 hour and 6 exercised subjects at 2–3 days and 7–8 days after the exercise. Muscle fibre sarcolemma integrity, infiltration of inflammatory cells and changes in fibre size and fibre phenotype composition as well as capillary supply were examined with specific antibodies using enzyme histochemistry and immunohistochemistry. Although all exercised subjects experienced DOMS which peaked between 1.5 to 2.5 days post exercise, no significant sarcolemma injury or inflammation was detected in any post exercise group. The results do not support the prevailing hypothesis that eccentric exercise causes an initial sarcolemma injury which leads to subsequent inflammation after eccentric exercise. The fibre size was 24% larger at 7–8 days than at 2–3 days post exercise (p<0.05). In contrast, the value of capillary number per fibre area tended to decrease from 2–3 days to 7–8 days post exercise (lower in 5 of the 6 subjects at 7–8 days than at 2–3 days; p<0.05). Thus, the increased fibre size at 7–8 days post exercise was interpreted to reflect fibre swelling. Because the fibre swelling did not appear at the time that DOMS peaked (between 1.5 to 2.5 days post exercise), we concluded that fibre swelling in the soleus muscle is not directly associated with the symptom of DOMS. [ABSTRACT FROM AUTHOR]

Background: N-acylethanolamines (NAEs) are endogenous compounds that regulate inflammation and pain. These include the cannabinoid ligand anandamide (AEA) and the peroxisome proliferator-activated receptor-α ligand palmitoylethanolamide (PEA). Little is known as to the levels of NAEs in pain states in human, particularly in the skeletal muscle. The aim of this study was to investigate the levels of these lipid mediators in muscle dialysate from women with chronic neck-/shoulder pain compared to healthy controls. Methods: Eleven women with chronic neck-/shoulder pain and eleven healthy women participated in this study. All participants went through microdialysis procedures in the trapezius muscle. Muscle dialysate samples were collected during four hours and analysed by nano liquid chromatography tandem mass spectrometry (nLC-MS/MS). Results: We were able to detect AEA, PEA, N-stearoylethanolamine (SEA) and 2-arachidonoylglycerol (2-AG) in a single chromatographic run. Of the NAEs studied, PEA and SEA were clearly detectable in the muscle microdialysate samples. The muscle dialysate levels of PEA and SEA were significantly higher in myalgic subjects compared to healthy controls. Conclusion: This study demonstrates that microdialysis in combination with mass spectrometry can be used for analysing NAE's in human muscle tissue regularly over time. Furthermore the significant group differences in the concentration of PEA and SEA in this study might fill an important gap in our knowledge of mechanisms in chronic myalgia in humans. In the long run this expanded understanding of nociceptive and anitinociceptive processes in the muscle may provide a base for ameliorating treatment and rehabilitation of pain. [ABSTRACT FROM AUTHOR]

Aquaporin-4 (AQP4) is a water channel expressed at the sarcolemma of fast-twitch skeletal muscle fibers, whose expression is altered in several forms of muscular dystrophies. However, little is known concerning the physiological role of AQP4 in skeletal muscle and its functional and structural interaction with skeletal muscle proteome. Using AQP4-null mice, we analyzed the effect of the absence of AQP4 on the morphology and protein composition of sarcolemma as well as on the whole skeletal muscle proteome. Immunofluorescence analysis showed that the absence of AQP4 did not perturb the expression and cellular localization of the dystrophin-glycoprotein complex proteins, aside from those belonging to the extracellular matrix, and no alteration was found in sarcolemma integrity by dye extravasation assay. With the use of a 2DEapproach (BN/SDS-PAGE), protein maps revealed that in quadriceps, out of 300 Coomassie-blue detected and matched spots, 19 proteins exhibited changed expression in AQP4-/- compared to WT mice. In particular, comparison of the protein profiles revealed 12 up- and 7 down-regulated protein spots in AQP42/2 muscle. Protein identification by MS revealed that the perturbed expression pattern belongs to proteins involved in energy metabolism (i.e. GAPDH, creatine kinase), as well as in Ca2+ handling (i.e. parvalbumin, SERCA1). Western blot analysis, performed on some significantly changed proteins, validated the 2D results. Together these findings suggest AQP4 as a novel determinant in the regulation of skeletal muscle metabolism and better define the role of this water channel in skeletal muscle physiology. [ABSTRACT FROM AUTHOR]