Low-load Resistance Exercise with Perceptually Primed Practical Blood Flow Restriction Induces Similar Motor Performance Fatigue, Physiological Changes, and Perceptual Responses Compared to Traditional Blood Flow Restriction in Males and Females.

In the recent past, practical blood flow restriction (pBFR) using non-pneumatic, usually elastic cuffs has been established as a cost-effective alternative to traditional blood flow restriction (BFR) using pneumatic cuffs, especially for training in large groups. This study investigated whether low-load resistance exercise with perceptually primed pBFR using an elastic knee wrap is suitable to induce similar motor performance fatigue as well as physiological and perceptual responses compared to traditional BFR using a pneumatic nylon cuff in males and females. In a randomized, counterbalanced cross-over study, 30 healthy subjects performed 4 sets (30-15-15-15 repetitions) of unilateral knee extensions at 20% of their one-repetition-maximum. In the pBFR condition, each individual was perceptually primed to a BFR pressure corresponding to 60% of their arterial occlusion pressure. Before and after exercise, maximal voluntary torque, maximal muscle activity, and cuff pressure-induced discomfort were assessed. Moreover, physiological (i.e., muscle activity, muscle oxygenation) and perceptual responses (i.e., effort and exercise-induced leg muscle pain) were recorded during exercise. Moderate correlations with no differences between pBFR and BFR were found regarding the decline in maximal voluntary torque and maximal muscle activity. Furthermore, no to very strong correlations between conditions, with no differences, were observed for muscle activity, muscle oxygenation, and perceptual responses during exercise sets. However, cuff pressure-induced discomfort was lower in the pBFR compared to the BFR condition. These results indicate that low-load resistance exercise combined with perceptually primed pBFR is a convenient and less discomfort inducing alternative to traditional BFR. This is especially relevant for BFR training with people who have a low cuff-induced discomfort tolerance.

Antinociceptive role of the thalamic dopamine D3 receptor in descending modulation of intramuscular formalin-induced muscle nociception in a rat model of Parkinson's disease.

Pain in Parkinson's disease (PD) has been validated as one of the major non-motor dysfunctions affecting the quality of life and subsequent rehabilitation. In the present study, we investigated the role of the dopamine D3 receptor in the thalamic mediodorsal (MD) and ventromedial (VM) nuclei mediated descending control of nociception and intramuscular (i.m.) 2.5% formalin-induced persistent muscle nociception. Paw withdrawal reflexes were measured in naive rats and rats subjected to PD induced by unilateral microinjection of 6 µg 6-OHDA into the rat striatum. Formalin-induced muscle nociception in phase 1, inter-phase, and phase 2 was significantly greater in PD rats compared to naive and vehicle-treated rats (P ˂ 0.001). PD rats exhibited bilaterally mechanical hyperalgesia and heat hypoalgesia in formalin-induced muscle nociception. Microinjection of SK609, a dopamine D3 receptor agonist, at various doses (2.5-7.5 nmol/0.5 µl) into the thalamic VM nucleus dose-dependently prolonged heat-evoked paw withdrawal latencies in both naive and PD rats. Administration of SK609 to either the MD or VM nuclei had no effect on noxious mechanically evoked paw withdrawal reflexes. Pre-treatment of the thalamic MD nucleus with SK609 significantly attenuated formalin-induced nociception, and reversed mechanical hyperalgesia, but not heat hypoalgesia. Pre-treatment of the thalamic VM nucleus with SK609 inhibited formalin-induced nociception in the late phase of phase 2 (30-75 min) and heat hypoalgesia, but not mechanical hyperalgesia (P < 0.05). It is suggested that the dopamine D3 receptors in the thalamus play an antinociceptive role in the descending modulation of nociception. Activation of D3 receptors within the thalamic MD and VM nuclei attenuates descending facilitation and enhances descending inhibition in rats during PD.

Elevated muscle pain induced by a hypertonic saline injection reduces power output independent of physiological changes during fixed perceived effort cycling.

Pain is a naturally occurring phenomenon that consistently inhibits exercise performance by imposing unconscious, neurophysiological alterations (e.g., corticospinal changes) as well as conscious, psychophysiological pressures (e.g., shared effort demands). Although several studies indicate that pain would elicit lower task outputs for a set intensity of perceived effort, no study has tested this. Therefore, this study investigated the impact of elevated muscle pain through a hypertonic saline injection on the power output, psychophysiological, cerebral oxygenation, and perceptual changes during fixed perceived effort exercise. Ten participants completed three visits (1 familiarization + 2 fixed perceived effort trials). Fixed perceived effort cycling corresponded to 15% above gas exchange threshold (GET) [mean rating of perceived effort (RPE) = 15 "hard"]. Before the 30-min fixed perceived effort exercise, participants received a randomized bilateral hypertonic or isotonic saline injection in the vastus lateralis. Power output, cardiorespiratory, cerebral oxygenation, and perceptual markers (e.g., affective valence) were recorded during exercise. Linear mixed-model regression assessed the condition and time effects and condition × time interactions. Significant condition effects showed that power output was significantly lower during hypertonic conditions [t107 = 208, P = 0.040, ß = 4.77 W, 95% confidence interval (95% CI) [0.27 to 9.26 W]]. Meanwhile, all physiological variables (e.g., heart rate, oxygen uptake, minute ventilation) demonstrated no significant condition effects. Condition effects were observed for deoxyhemoglobin changes from baseline (t107 = -3.29, P = 0.001, ß = -1.50 ΔµM, 95% CI [-2.40 to -0.61 ΔµM]) and affective valence (t127 = 6.12, P = 0.001, ß = 0.93, 95% CI [0.63 to 1.23]). Results infer that pain impacts the self-regulation of fixed perceived effort exercise, as differences in power output mainly occurred when pain ratings were higher after hypertonic versus isotonic saline administration.NEW & NOTEWORTHY This study identifies that elevated muscle pain through a hypertonic saline injection causes significantly lower power output when pain is experienced but does not seem to affect exercise behavior in a residual manner. Results provide some evidence that pain operates on a psychophysiological level to alter the self-regulation of exercise behavior due to differences between conditions in cerebral deoxyhemoglobin and other perceptual parameters.

The influence of vibratory massage after physical exertion on selected psychological processes.

Good mental preparation of an athlete plays an important role in achieving optimal sports results. An athlete who enters a competition should not feel fatigue resulting from intense physical exercise. Therefore, new and effective methods are being sought that could help accelerate the process of both physical and mental regeneration. Vibrotherapy is one of them. The aim of the study was to determine the optimal frequency of vibration, its duration and the position in which the subjects were placed during the treatments, in relation to the reduction of subjectively perceived exertion muscle pain, mental discomfort, emotional states and the level of cognitive processes that were disturbed by intense physical activity. Sixteen healthy male volunteers were involved in this study. The participants were assessed for their aerobic and anaerobic capacity. Each of the subjects performed a set of intensive physical exercises and then underwent vibrotherapy treatment. In random order, each of the men tested the effectiveness of eight combinations of frequency, duration, and body position. Psychological tests were conducted for each combination: frequency, duration of treatment, and position during treatment, in four stages: (1) before the start of the experiment (baseline POMS measurements), (2) immediately after the exercise (VAS scale, scale examining psychological discomfort and STROOP test), (3) immediately after the vibration treatment (POMS measurements, VAS scale, scale examining psychological discomfort and STROOP test), (4) 24 h after the vibration treatment (VAS scale examining subjective assessment of perceived pain and psychological discomfort). Based on the results, it was concluded that all the studied variables improved significantly over time (after the vibration treatment and 24 h after training). In addition, a statistically significant interaction measurement × frequency was noted for vigor scale (52HZ favored greater improvement in this state), and a statistically significant interaction was found for measurement × time for the VAS scale (p < 0.05) - the lower pain value was indicated 24 h after the 10-min vibration treatment. The type of frequency used, position, and duration of the treatment did not play a statistically significant role in changing STROOP test results and severity of psychological discomfort (p > 0.05).

Enhancing endurance performance with combined imagined and actual physical practice.

PURPOSE: The perception of effort exerts influence in determining task failure during endurance performance. Training interventions blending physical and cognitive tasks yielded promising results in enhancing performance. Motor imagery can decrease the perception of effort. Whether combining motor imagery and physical training improves endurance remains to be understood, and this was the aim of this study. METHODS: Participants (24 ± 3 year) were assigned to a motor imagery (n = 16) or a control (n = 17) group. Both groups engaged in physical exercises targeting the knee extensors (i.e., wall squat, 12 training sessions, 14-days), with participants from the motor imagery group also performing motor imagery. Each participant visited the laboratory Pre and Post-training, during which we assessed endurance performance through a sustained submaximal isometric knee extension contraction until task failure, at either 20% or 40% of the maximal voluntary contraction peak torque. Perceptions of effort and muscle pain were measured during the exercise. RESULTS: We reported no changes in endurance performance for the control group. Endurance performance in the motor imagery group exhibited significant improvements when the intensity of the sustained isometric exercise closely matched that used in training. These enhancements were less pronounced when considering the higher exercise intensity. No reduction in perception of effort was observed in both groups. There was a noticeable decrease in muscle pain perception within the motor imagery group Post training. CONCLUSION: Combining motor imagery and physical training may offer a promising avenue for enhancing endurance performance and managing pain in various contexts.

Non-Skin Related Symptoms Are Common in Chronic Spontaneous Urticaria and Linked to Active and Uncontrolled Disease: Results From the Chronic Urticaria Registry.

BACKGROUND: Chronic spontaneous urticaria (CSU) can present with non-skin related symptoms (NSRS), including recurrent unexplained fever, joint, bone, or muscle pain (JBMP), and malaise, which also occur in other conditions that manifest with wheals (eg, urticarial vasculitis or autoinflammatory disorders) or without wheals (eg, infection). OBJECTIVE: We sought to determine the rate of patients with CSU affected by fever, JBMP, and malaise, their trigger factors, links with clinical and laboratory characteristics, and their impact on everyday life and treatment responses. METHODS: We analyzed baseline data from the Chronic Urticaria Registry of 2,521 patients with CSU who were aged 16 years or older. RESULTS: One third of CSU patients (31.2%; 786 of 2,521) had one or more NSRS, including recurrent fever (5.3%), JBMP (19.1%), and/or malaise (18.6%). In a multivariable analysis, having one or more of these NSRS correlated with food and infection as trigger factors of urticaria (adjusted odds ratio [aOR] = 1.7 and 1.5), wheals of 24 hours or greater duration (aOR = 2.5), sleep disturbance (aOR = 2.4), anxiety (aOR = 2.8), comorbid atopic dermatitis (aOR = 2.1), gastrointestinal disease (aOR = 1.8), elevated leukocytes (aOR = 1.7) and erythrocyte sedimentation rate (aOR = 1.5). In a bivariate analysis, these NSRS were additionally associated with higher disease activity (weekly Urticaria Activity Score, median: 21 vs 14; P = .009), longer disease duration (years, median: 2 vs 1; P = .001), the presence of angioedema (74.6% vs 58.7%; P < .001), worse quality of life (Chronic Urticaria Quality of Life Questionnaire, median: 42 vs 29; P < .001) and more frequent poor control of CSU (78% vs 69%; P < .001). CONCLUSIONS: The presence of NSRS in a subpopulation of patients with CSU points to the need for better control of the disease, exclusion of comorbid conditions, and/or exclusion of urticarial vasculitis and urticarial autoinflammatory diseases.

The 8:1:1 Supplementation of Branched-Chain Amino Acids in High-Intensity Training: A Case Study of the Protective Effect on Rhabdomyolysis.

INTRODUCTION: The increasing prevalence of high-intensity sports activities, notably the burgeoning popularity of CrossFit, underscores the contemporary significance of such physical pursuits. The discernible protective impact of branched-chain amino acids on muscle fatigue and injuries is emerging as a noteworthy area of investigation. Within the realm of sports, integrating BCAA supplementation into dietary practices holds promise for aiding athletes in their recovery, particularly in mitigating Delayed-Onset Muscle Soreness. METHODOLOGY: This study adopted an experimental pilot design with repeated measures, employing a controlled and randomized approach through double-blind procedures. The participant engaged in high-intensity activity, specifically the CrossFit Karen® test, which entailed executing 150 wall ball throws (9 kg) to a height of 3 m. The trial incorporated three randomized supplementation conditions: BCAAs in an 8:1:1 ratio or a 2:1:1 ratio or a placebo condition. The participant consumed 15 g daily for 7 days, commencing 72 h prior to the initial blood sample and the first Karen® test. RESULTS: In this study, BCAA supplementation at an 8:1:1 ratio demonstrated a discernible protective effect against muscular damage, as evidenced by creatine kinase values and ratings of perceived exertion.

Hydrogen-rich water supplementation promotes muscle recovery after two strenuous training sessions performed on the same day in elite fin swimmers: randomized, double-blind, placebo-controlled, crossover trial.

Purpose: Molecular hydrogen has been shown to possess antioxidant, anti-inflammatory, ergogenic, and recovery-enhancing effects. This study aimed to assess the effect of molecular hydrogen administration on muscle performance, damage, and perception of soreness up to 24 h of recovery after two strenuous training sessions performed on the same day in elite fin swimmers. Methods: Eight females (mean ± SD; age 21.5 ± 5.0 years, maximal oxygen consumption 45.0 ± 2.5 mL.kg-1.min-1) and four males (age 18.9 ± 1.3 years, maximal oxygen consumption 52.2 ± 1.7 mL.kg-1.min-1) performed 12 × 50 m sprints in the morning session and a 400 m competitive performance in the afternoon session. Participants consumed hydrogen-rich water (HRW) or placebo 3 days before the sessions (1,260 mL/day) and 2,520 mL on the experimental day. Muscle performance (countermovement jump), muscle damage (creatine kinase), and muscle soreness (100 mm visual analogue scale) were measured during the experimental day and at 12 and 24 h after the afternoon session. Results: HRW compared to placebo reduced blood activity of creatine kinase (156 ± 63 vs. 190 ± 64 U.L-1, p = 0.043), muscle soreness perception (34 ± 12 vs. 42 ± 12 mm, p = 0.045), and improved countermovement jump height (30.7 ± 5.5 cm vs. 29.8 ± 5.8 cm, p = 0.014) at 12 h after the afternoon session. Conclusion: Four days of HRW supplementation is a promising hydration strategy for promoting muscle recovery after two strenuous training sessions performed on the same day in elite fin swimmers. Clinical Trial Registration: clinicaltrials.gov, identifier NCT05799911.

A Case Report and Literature Review of Skeletal Muscle Metastasis of Non-small Cell Lung Cancer.

Non-small cell lung cancer metastasis to skeletal muscle is an uncommon occurrence. Lung cancers are more likely to spread to the brain, bone, liver, and adrenals. Here, we present a rare case of non-small cell lung cancer metastasis to the skeletal muscle in a 54-year-old male. In addition, we present a literature review on skeletal metastasis of non-small cell lung cancer. The most frequent presentation of skeletal muscle metastasis is muscular pain with or without swelling. The mechanism of metastasis to muscle is not well understood; it is theorized that hematogenous spread is the most likely route. As with our patient, the presence of skeletal muscle mass is considered an aggressive disease with poor survival, usually less than one year. The treatment for muscle metastasis is often palliative in the form of radiation therapy, chemotherapy, or surgical removal of the mass.

Mirror Therapy Reduces Pain and Preserves Corticomotor Excitability in Human Experimental Skeletal Muscle Pain.

Approaches to preserve corticomotor excitability (CE) are attracting interest as a treatment for pain-induced changes in neural plasticity. We determined the effects of mirror therapy (MT) on skeletal muscle pain. Fifteen healthy adults who received hypertonic saline injections (5.8% NaCl, 0.2 mL) into the first dorsal interosseous (FDI) muscle of the right hand to induce experimental skeletal muscle pain were assigned to either the "MT and injection" or "injection only" group. Post-injection, the "MT and injection" group observed their left index finger abducting and adducting for 4 min, creating the illusion that the right index finger was moving. The "injection only" group remained at rest. CE and pain were assessed by measuring motor-evoked potentials (MEPs) of the right FDI triggered by transcranial magnetic stimulation and the numerical rating scale (NRS), respectively. MEP amplitudes were significantly higher in the "MT and injection" group, a trend that persisted post-MT intervention (MT intervention; p < 0.01, post-1; p < 0.05). The time for the NRS score to reach 0 was notably shorter in the "MT and injection" group (p < 0.05). Our preliminary results suggested that MT decreases CE and pain in skeletal muscles, potentially preventing neural plasticity changes associated with skeletal muscle pain and providing early pain relief.

Decrypting the putative interrelation between sleep bruxism, masticatory muscle pain and sleep breathing disorders: Nosology and the role of hypoxia.

This commentary on sleep medicine explores whether the potential relationship between sleep bruxism (SB), masticatory muscle pain (MMP) and sleep breathing disorders (SBDs)contributes to improving the management of co-occurring conditions.The paper is divided into 2 sections: (1) reviewing the debate on SB nosology; and (2) based on the publications from the Martynowicz & Wieckiewicz research group, exploringthe role of intermittent hypoxia as a putative mechanism endotype that may link such co-occurrence among individuals for whom characteristics are not yet clear.

The Effect of Joint Hypermobility Syndrome on DOMS and Recovery Time.

Background: Previous research has reported that people with Joint Hypermobility Syndrome (JHS) and Ehlers-Danlos Syndrome (EDS) generally experience a high rate of muscular injury and pain. However, there is limited research comparing the recovery times and length of Delayed Onset Muscle Soreness (DOMS) in individuals with JHS to non-hypermobile individuals in response to exercise. Hypotheses/Purpose: The purpose of this study was to investigate JHS and its effects on DOMS and its recovery time. Study Design: Quasi-experimental, observational comparison. Methods: Two groups including a hypermobile group (score >4 on Beighton Scale) and a non-hypermobile group all took part in five-second long standing eccentric bicep curls based using their one- repetition maximum (1-RM) of their dominant arm to failure in order to induce DOMS. Visual analog pain scale (VAS), McGill pain scale, resting arm angle, girth, and the pressure pain threshold, all domains of DOMS, were measured over a five-day period. Results were analyzed using ANOVA with time as the repeated factor. Results: Both groups experienced DOMS following the eccentric exercise. However, VAS reporting was significantly greater in the hypermobile group compared to the non-hypermobile group and there was a significant difference over time. However, other variables did not reveal any other significant findings between groups. Conclusion: Individuals with JHS may experience greater DOMS and require more time to recover between treatment sessions. Therapists need to be aware that patients with hypermobility may experience higher pain levels related to exercise, and they need to adjust treatment parameters appropriately. Level of Evidence: 2b.

Inhibitory effect of acupoint electrostimulation with different layers and intensities on muscular inflammatory pain and spinal WDR neuron activity. / ç©´ä½ä¸åŒå±‚æ¬¡å’Œå¼ºåº¦ç”µåˆºæ¿€ç¼“è§£è‚Œè‚‰ç‚Žæ€§ç—›åŠå¯¹è„Šé«“èƒŒè§’å¹¿åŠ¨åŠ›ç¥žç»å ƒçš„æŠ‘åˆ¶ä½œç”¨.

OBJECTIVES: To observe the analgesic effects of different levels and intensities of electrical stimulation on the local acupoints in the pain source area and their impact on wide dynamic range (WDR) neurons in the spinal dorsal horn, in order to provide a basis for selecting appropriate parameters for electroacupuncture (EA) stimulation. METHODS: Wistar rats were used in 3 parts of the experiment. Complete Freund's adjuvant was used to establish a model of inflammation-induced pain in the gastrocnemius muscle. After modeling, 6 rats were randomly selected for multi-channel extracellular electrophysiological recording of the electrical activity of WDR neurons, to determine the threshold for activating the A-component (Ta) and the C-component (Tc), which were used as the intervention intensities for skin transcutaneous electrical acupoint stimulation (TEAS) or EA. Thirty-six rats were randomly divided into normal , model , TEAS-Ta , TEAS-Tc, EA-Ta , and EA-Tc groups, with 6 rats in each group. In the pain source area , Ta or Tc intensity of TEAS or EA intervention at"Chengshan"(BL57) was performed for 30 min each time, once a day, for 3 consecutive days. A small animal pressure pain measurement instrument was used to measure the mechanical pressure pain threshold of the gastrocnemius muscle in rats, and the Von Frey filament was used to measure the mechanical pain threshold of the footpad. Thirteen rats were randomly selected to observe the immediate responsiveness of WDR neurons to Ta/Tc intensity of EA or TEAS in BL57. RESULTS: The thresholds of TEAS to activate WDR neuron A-component or C-component were (2.43±0.57) mA and (7.00±1.34) mA, respectively, while the thresholds for EA to activate muscle WDR neuron A-component or C-component were (0.72±0.34) mA and (1.58±0.35) mA, respectively. After injection of CFA into the gastrocnemius muscle, compared with the normal group both the mechanical pressure pain threshold of the gastrocnemius muscle and the mechanical pain threshold of the footpad of rats in the model group were significantly decreased (P<0.001). After TEAS-Ta, TEAS-Tc or EA-Ta intervention in the BL57, both the mechanical pressure pain threshold of the gastrocnemius muscle and the mechanical pain threshold of the footpad were significantly higher than those in the model group (P<0.05, P<0.001). Compared with the normal group, the electrical threshold for evoking WDR neuron C-component discharge was significantly decreased (P<0.001) in the model group, while increased after TEAS-Ta, TEAS-Tc, or EA-Ta intervention (P<0.01) compared with the model group. The evoked discharge frequency of muscle WDR neurons decreased significantly after immediate intervention with TEAS-Ta, TEAS-Tc, or EA-Ta (P<0.01, P<0.05). EA-Tc had no significant improvement on the evoked electrical activity of WDR neurons or pain behavior. CONCLUSIONS: TEAS-Ta, TEAS-Tc, or EA-Ta can all alleviate the local and footpad mechanical pain in rats with muscle inflammation and inhibit the responsiveness of WDR neurons, indicating that different intensities are required for analgesic effects at different levels of acupoints in the pain source area.

Neurochemical mechanism of muscular pain: Insight from the study on delayed onset muscle soreness.

We reviewed fundamental studies on muscular pain, encompassing the characteristics of primary afferent fibers and neurons, spinal and thalamic projections, several muscular pain models, and possible neurochemical mechanisms of muscle pain. Most parts of this review were based on data obtained from animal experiments, and some researches on humans were also introduced. We focused on delayed-onset muscle soreness (DOMS) induced by lengthening contractions (LC), suitable for studying myofascial pain syndromes. The muscular mechanical withdrawal threshold (MMWT) decreased 1-3 days after LC in rats. Changing the speed and range of stretching showed that muscle injury seldom occurred, except in extreme conditions, and that DOMS occurred in parameters without muscle damage. The B2 bradykinin receptor-nerve growth factor (NGF) route and COX-2-glial cell line-derived neurotrophic factor (GDNF) route were involved in the development of DOMS. The interactions between these routes occurred at two levels. A repeated-bout effect was observed in MMWT and NGF upregulation, and this study showed that adaptation possibly occurred before B2 bradykinin receptor activation. We have also briefly discussed the prevention and treatment of DOMS.

Hyperexcitability of muscle spindle afferents in jaw-closing muscles in experimental myalgia: Evidence for large primary afferents involvement in chronic pain.

The goals of this review are to improve understanding of the aetiology of chronic muscle pain and identify new targets for treatments. Muscle pain is usually associated with trigger points in syndromes such as fibromyalgia and myofascial syndrome, and with small spots associated with spontaneous electrical activity that seems to emanate from fibers inside muscle spindles in EMG studies. These observations, added to the reports that large-diameter primary afferents, such as those innervating muscle spindles, become hyperexcitable and develop spontaneous ectopic firing in conditions leading to neuropathic pain, suggest that changes in excitability of these afferents might make an important contribution to the development of pathological pain. Here, we review evidence that the muscle spindle afferents (MSAs) of the jaw-closing muscles become hyperexcitable in a model of chronic orofacial myalgia. In these afferents, as in other large-diameter primary afferents in dorsal root ganglia, firing emerges from fast membrane potential oscillations that are supported by a persistent sodium current (INaP ) mediated by Na+ channels containing the α-subunit NaV 1.6. The current flowing through NaV 1.6 channels increases when the extracellular Ca2+ concentration decreases, and studies have shown that INaP -driven firing is increased by S100ß, an astrocytic protein that chelates Ca2+ when released in the extracellular space. We review evidence of how astrocytes, which are known to be activated in pain conditions, might, through their regulation of extracellular Ca2+ , contribute to the generation of ectopic firing in MSAs. To explain how ectopic firing in MSAs might cause pain, we review evidence supporting the hypothesis that cross-talk between proprioceptive and nociceptive pathways might occur in the periphery, within the spindle capsule.

Pain quality patterns in delayed onset muscle soreness of the lower back suggest sensitization of fascia rather than muscle afferents: a secondary analysis study.

Delayed onset muscle soreness (DOMS) of the lower back is considered a surrogate for acute low back pain (aLBP) in experimental studies. Of note, it is often unquestioningly assumed to be muscle pain. To date, there has not been a study analyzing lumbar DOMS in terms of its pain origin, which was the aim of this study. Sixteen healthy individuals (L-DOMS) were enrolled for the present study and matched to participants from a previous study (n = 16, L-PAIN) who had undergone selective electrical stimulation of the thoracolumbar fascia and the multifidus muscle. DOMS was induced in the lower back of the L-DOMS group using eccentric trunk extensions performed until exhaustion. On subsequent days, pain on palpation (100-mm analogue scale), pressure pain threshold (PPT), and the Pain Sensation Scale (SES) were used to examine the sensory characteristics of DOMS. Pain on palpation showed a significant increase 24 and 48 h after eccentric training, whereas PPT was not affected (p > 0.05). Factor analysis of L-DOMS and L-PAIN sensory descriptors (SES) yielded a stable three-factor solution distinguishing superficial thermal ("heat pain ") from superficial mechanical pain ("sharp pain") and "deep pain." "Heat pain " and "deep pain" in L-DOMS were almost identical to sensory descriptors from electrical stimulation of fascial tissue (L-PAIN, all p > 0.679) but significantly different from muscle pain (all p < 0.029). The differences in sensory description patterns as well as in PPT and self-reported DOMS for palpation pain scores suggest that DOMS has a fascial rather than a muscular origin.

Effect of Botulinum Toxin on Masticatory Muscle Pain in Patients with Temporomandibular Disorders: A Randomized, Double-Blind, Placebo-Controlled Pilot Study.

This study aimed to evaluate the efficacy of botulinum toxin type A (BoNT/A) in patients with temporomandibular disorders (TMDs) associated with masticatory muscle pain (MMP) and headaches. This randomized, double-blind, placebo-controlled pilot study is the first clinical trial to evaluate both disorders simultaneously. Twenty-one patients with myogenous TMD were randomly assigned to two groups. The experimental and control groups received injections of either BoNT/A or saline into the sites showing tenderness after palpation of a total of 16 muscle areas, including each masseter, a temporalis, splenius capitis, sternocleidomastoid, and trapezius muscle. During each visit, the clinical effects, based on the intensity of orofacial pain (OVAS), headache (HVAS), number of tender points (TPs), maximum mouth opening (MMO), and headache frequency (HF), were evaluated at four time points, namely, pre-injection and 4, 8, and 12 weeks after the injection, in both groups. Friedman and Mann-Whitney tests were used for the analyses. In the experimental group, the reductions in OVAS, TP, HVAS, and HF showed significant differences over time, excluding MMO, whereas there was no significant difference in any of the variables in the control group. In addition, the decline in TPs was significantly different between the experimental and control groups at all time points, especially after 4 and 12 weeks, compared to that during pre-injection. In conclusion, treatment with BoNT/A was relatively effective for masticatory muscle pain caused by TMDs and headache compared to the saline placebo.

Relationship between pain severity, satisfaction with life and the quality of sleep in Polish adults with temporomandibular disorders.

BACKGROUND: Temporomandibular disorders (TMD) pose a serious health problem that can have a negative effect on patients' lives, impair work performance, and result in work absences and restrictions in daily activities. OBJECTIVES: The aim of this observational, cross-sectional study was to evaluate the level of satisfaction with life among Polish patients with TMD and to assess the influence of pain severity on this parameter. A secondary goal was to investigate sleep quality within this patient group and explore its relationship with pain. MATERIAL AND METHODS: A total of 219 patients from the Outpatient Clinic for Temporomandibular Disorders at the University Dental Polyclinic in Wroclaw, Poland, participated in this study. These individuals underwent a clinical examination using the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) protocol and completed 2 validated questionnaires, namely the Satisfaction With Life Scale (SWLS) and the Pittsburgh Sleep Quality Index (PSQI). Furthermore, the patients were assessed for the severity of masseter muscle pain (MMP) and temporal muscle pain (TMP), and the average pain in these muscles (AMP) was calculated. Subsequently, a statistical analysis was performed on the collected data. RESULTS: The group of patients with average satisfaction with life exhibited significantly higher levels of MMP (p = 0.025) and AMP (p = 0.044) as compared to the high-satisfaction group. Regarding sleep quality, 50.23% of the patients experienced poor sleep quality. Poor sleep quality was found to be statistically associated with higher levels of TMP (p = 0.032) and AMP (p = 0.028). Moreover, women demonstrated significantly worse sleep quality as compared to men (p = 0.002). The findings indicate that PSQI has a greater impact on SWLS than vice versa. CONCLUSIONS: Due to a large number of TMD patients experiencing poor sleep quality and the associated reduced life satisfaction, these parameters should be considered as influential factors that modify the management of patients with TMD.

A case-control study on the effect of rhythmic masticatory muscle activity (RMMA) clusters on sleep fragmentation and severity of orofacial muscle pain in sleep bruxism.

Rhythmic masticatory muscle activity (RMMA) is a periodic muscle activity that characterises sleep bruxism (SB) events. These can occur as a single event, in pairs, or in clusters. Since RMMA episodes often occur in clusters and the relevance of this occurrence is unknown, we conducted a study to investigate the effect of RMMA clusters on sleep fragmentation and the severity of orofacial muscle pain. This study involved a secondary analysis using data from 184 adult subjects with orofacial muscle pain who underwent definitive polysomnography (PSG) for sleep bruxism diagnosis. Self-reported orofacial muscle pain (OFMP) was assessed using the numeric rating scale, and additional evaluation of side-to-side equivalence (symmetry) was described using a binary system. Among the 184 participants, 60.8% (n = 112) did not exhibit clusters and among the 72 participants with clusters, 36.1% (n = 26) and 63.9% (n = 46) were in the high and low RMMA frequency groups, respectively. The high SB group had significantly three times more phasic RMMA events than the noncluster group. A total of 89.67% (n = 165) of subjects reported orofacial muscle pain. While there was no difference in the severity of OFMP among groups, a significant decrease in symmetry between the severity of temporal muscle pain on the left and right sides was noted in the cluster group compared with the noncluster group. Clustering of RMMA events is associated with sleep fragmentation. The asymmetry of temporal muscle pain is related to the presence of RMMA clusters in sleep bruxism.