Intramuscular Oxygenation and Muscle Activity of Extensor Carpi Radialis Brevis During Piano Performance: An Observational Study.

BACKGROUND: Repetitive piano movements have been associated with playing-related musculoskeletal disorders (PRMDs) such as forearm myalgia and symptoms of lateral epicondylopathy. Despite the high prevalence of PRMDs among pianists, there is poor understanding regarding the underlying physiological mechanisms. Intramuscular oxygenation may play a role in the development of PRMDs. Therefore, this observational study aimed to explore the effect variability of playing piano repertoire on the oxygenation of the extensor carpi radialis brevis (ECRB). METHODS: Surface electromyography (EMG) activity and intramuscular oxygenation data (using near-infrared spectroscopy, NIRS) of the left and right ECRB were recorded in 13 conservatory piano students (8 female, 5 male, mean age 23.54 ± 3.24 years) while playing piano repertoire (virtuoso piece or études) for 20 minutes. From the oxygenation data, relative changes (in the percentage of the baseline measurements at rest) were calculated. RESULTS: For all participants, the oxygenated hemoglobin of the left ECRB over the piano play presented an averaged decline to the baseline resting value, with a sample mean for left ECRB of -7.48% and -11.88% for the right ECRB, ranging from -15.53% to -2.00% and -19.12% to -3.93%, respectively. The deoxygenated hemoglobin ranged in the left ECRB from -5.39% to 39.14% and from -9.37% to 54.01% in the right ECRB. The change in total hemoglobin ranged from -5.35% to 16.80% for the left ECRB and -12.10% to 10.37% for the right ECRB. EMG activity (in % maximal voluntary contraction) presented a mean of 16.85% (range 11.86 to 24.43) for the left ECRB and 23.65% (range 14.46 to 37.91) for the right ECRB. This pilot study presented a Pearson's r between the averaged oxygenated hemoglobin and EMG of -0.60 for the right ECRB and -0.48 for the left ECRB. CONCLUSION: Piano performance induced an average decline in oxygenated hemoglobin in the left and right ECRB, which differed largely between the specific pieces played. The EMG activity can partially explain these differences. Further research is needed to explore the impact of a 'dynamic index' reflecting the piece's dynamic characteristics and the individual oxygenation characteristics.

Local Heat Applications as a Treatment of Physical and Functional Parameters in Acute and Chronic Musculoskeletal Disorders or Pain.

OBJECTIVES: The aim of this systematic review and meta-analysis was to evaluate the effectiveness of local heat applications (LHAs) in individuals with acute or chronic musculoskeletal disorders. DATA SOURCES: An electronic search was conducted on MEDLINE, Cochrane Controlled Register of Trials, Current Nursing and Allied Health Literature, and the Physiotherapy Evidence databases up to December 2019. STUDY SELECTION: Studies incorporating adults with any kind of musculoskeletal issues treated by LHA compared with any treatment other than heat were included. DATA EXTRACTION: Two authors independently performed the methodological quality assessment using the Cochrane Risk of Bias tool. DATA SYNTHESIS: LHA showed beneficial immediate effects to reduce pain vs no treatment (P<.001), standard therapy (P=.020), pharmacologic therapy (P<.001), and placebo/sham (P=.044). Physical function was restored after LHA compared with no treatment (P=.025) and standard therapy (P=.006), whereas disability improved directly after LHA compared with pharmacologic therapy (P=.003) and placebo/sham (P<.028). Quality of life was improved directly after LHA treatment compared with exercise therapy (P<.021). Range of motion increased and stiffness decreased after LHA treatment compared with pharmacologic therapy (P=.009, P<.001) and placebo/sham (P<.001, P=.023). The immediate superior effects of LHA on muscular strength could be observed compared with no treatment (P<.001), cold (P<.001), and placebo/sham (P=.023). CONCLUSIONS: Individuals with acute musculoskeletal disorders might benefit from using LHA as an adjunct therapy. However, the studies included in this meta-analysis demonstrated a high heterogeneity and mostly an unclear risk of bias.

Effects of Rehearsal Time and Repertoire Speed on Upper Trapezius Activity in Conservatory Piano Students.

BACKGROUND: Repetitive piano play may overload neck and shoulder muscles and tendons, leading to playing-related musculoskeletal disorders (PRMDs). METHODS: In this pilot study (EMG data of the extensor carpi radialis have been published separately), surface electromyography (sEMG) activity of the upper trapezius (UT) was captured in 10 conservatory piano students while playing a fast and a slow music score selected from the individual's repertoire, each 3 minutes long. Measurements were made at baseline and again after 2 hrs and 4 hrs of rehearsal time of the piano études. The amplitude of the sEMG signal was processed by a smoothing algorithm, and the frequency component with a non-orthogonal wavelets procedure. Amplitude of the sEMG was expressed in percent of maximal voluntary contraction (%MVC) at baseline, and the frequency component using median frequency based on the frequency band powers. Statistical analysis encompassed repeated measures ANOVAs for the amplitude and frequency components of the sEMG signal (set at 5%). The students also rated the intensity of rehearsals using a visual analog scale (VAS). RESULTS: The median values for the %MVC presented a global mean for the left trapezius of 5.86 (CI90% 4.71, 6.97) and 5.83 for the right trapezius (CI90% 4.64, 7.05). The rehearsals at moderate intensity increased the amplitude of %MVC of the upper trapezius by around 50% and decreased the median frequency. CONCLUSIONS: Playing faster presented higher magnitudes of activity of the upper trapezius. The decrease in the median frequency in response to long rehearsals may be a sign of muscle fatigue.

Assessment of neuropathic pain after spinal cord injury using quantitative pain drawings.

STUDY DESIGN: Clinimetric cross-sectional cohort study in adults with paraplegic spinal cord injury (SCI) and neuropathic pain (NP). OBJECTIVE: To assess the reliability of standardized quantitative pain drawings in patients with NP following SCI. SETTING: Hospital-based research facility at the Spinal Cord Injury Center, Balgrist University Hospital, Zurich, Switzerland. METHODS: Twenty individuals with chronic thoracic spinal cord injury and neuropathic pain were recruited from a national and local SCI registry. A thorough clinical examination and pain assessments were performed. Pain drawings were acquired at subsequent timepoints, 13 days (IQR 7.8-14.8) apart, in order to assess test-retest reliability. RESULTS: The average extent [%] and intensity [NRS 0-10] of spontaneous NP were 11.3% (IQR 4.9-35.8) and 5 (IQR 3-7), respectively. Pain extent showed excellent inter-session reliability (intraclass correlation coefficient 0.96). Sensory loss quantified by light touch and pinprick sensation was associated with larger pain extent (rpinprick = -0.47, p = 0.04; rlight touch = -0.64, p < 0.01). CONCLUSION: Assessing pain extent using quantitative pain drawings is readily feasible and reliable in human SCI. Relating information of sensory deficits to the presence of pain may provide distinct insights into the interaction of sensory deafferentation and the development of neuropathic pain after SCI.

Partial-body cryotherapy (-135°C) and cold-water immersion (10°C) after muscle damage in females.

This randomized controlled trial examined the effects of cold-water immersion (CWI), partial-body cryotherapy (PBC), or a passive control (CON) on physiological and recovery variables following exercise-induced muscle damage (EIMD, 5 × 20 drop jumps) in females. Twenty-eight females were allocated to PBC (30 seconds at -60°C, 2 minutes at -135°C), CWI (10 minutes at 10°C), or CON (10 minutes resting). Muscle oxygen saturation (SmO2 ), cutaneous vascular conductance (CVC), mean arterial pressure (MAP), and local skin temperature were assessed at baseline and through 60 minutes (10-minute intervals), while delayed onset of muscle soreness (DOMS), muscle swelling, maximum voluntary isometric contraction (MVIC), and vertical jump performance (VJP) were assessed up to 72 hours (24-hour intervals) following treatments. SmO2 was lower in PBC (Δ-2.77 ± 13.08%) and CWI (Δ-5.91 ± 11.80%) compared with CON (Δ18.96 ± 1.46%) throughout the 60-minute follow-up period (P < .001). CVC was lower from PBC (92.7 ± 25.0%, 90.5 ± 23.4%) and CWI (90.3 ± 23.5%, 88.1 ± 22.9%) compared with CON (119.0 ± 5.1 and 116.1 ± 6.6%, respectively) between 20 and 30 minutes (P < .05). Mean skin temperature was lower from CWI vs PBC (between 10 and 40 minutes, P < .05). Mean skin temperature was higher in CON compared with CWI up to 60 minutes and compared with PBC up to 30 minutes (P < .05). DOMS was lower following both PBC and CWI compared with CON through 72-hour (P < .05), with no difference between groups. No main group differences for swelling, MVIC, and VJP were observed. In conclusion, CWI elicited generally greater physiological effects compared with PBC while both interventions were more effective than CON in reducing DOMS in females, but had no effect on functional measures or swelling.

Comparison of two skin temperature assessment methods after the application of topical revulsive products: Conductive iButton data logger system vs contact-free infrared thermometry.

BACKGROUND: Skin temperature assessments comprise conductive and contact-free techniques. Comparison between conductive data loggers and contact-free thermometry after the application of revulsive products is scarce. This study aimed to compare iButton data loggers with an infrared thermometer after the application of two revulsive products. Secondly, the relation between skin temperature kinetics with skin's perfusion of microcirculation was investigated. MATERIALS AND METHODS: Healthy females (n = 25) were randomly allocated to two groups, representing the products A and B. Skin temperature was measured with "iButtons" and an infrared pistol at baseline and up to 1 hour after application. Skin's perfusion of microcirculation was monitored with a laser speckle contrast imager. RESULTS: Baseline "iButton" temperature values were significantly lower compared with infrared pistol values in both groups. After application of the products, skin temperature decreased as recorded with both devices followed by an increase to baseline values when measured with the pistol. The results obtained by the "iButtons" reached values above baseline in both products towards the end of the follow-up period. A moderate correlation was found between infrared pistol and "iButton" system in product A, with a weak negative correlation between skin's perfusion of microcirculation and temperature devices. For product B, the correlation between the devices was moderate and between skin's perfusion and temperature devices weak and positive. CONCLUSION: Both devices produced similar kinetics, except at baseline, where they may differ as metallic loggers have been insufficiently adapted to skin temperature. Skin's perfusion of microcirculation could not explain skin temperature changes.

Effects of Rehearsal Time and Repertoire Speed on Extensor Carpi Radialis EMG in Conservatory Piano Students.

BACKGROUND: Repetitive actions while playing piano may overload forearm muscles and tendons, leading to playing-related musculoskeletal disorders (PRMDs), including lateral epicondylitis. METHODS: In this pilot study, surface electromyography (sEMG) activity of the extensor carpi radialis (ECR) was captured in 10 conservatory piano students while playing a fast and a slow music score selected from the individual's repertoire, each 3 minutes long. Measurements were made at baseline and again after 2 hrs and 4 hrs of rehearsal time of the piano études. The amplitude of the sEMG signal was processed by a smoothing algorithm, and the frequency component with a non-orthogonal wavelets procedure. Amplitude of the sEMG was expressed in percent of maximal voluntary contraction (%MVC) at baseline. Statistical analysis encompassed 2-way repeated measures ANOVAs for the amplitude and frequency components of the sEMG signal (a set at 5%). The students also rated the intensity of rehearsals using a VAS. RESULTS: The ECR presented with a mean amplitude of 23%MVC for the slow scores, which increased significantly to 36%MVC for the fast scores. The sEMG signal presented a significant though small decrease of 1.9%MVC in amplitude between baseline and 4 hrs of rehearsal time and no shift in frequency, which may indicate that the rehearsals were held at a physiological steady-state and suggesting optimization or complementary muscle loading. CONCLUSIONS: These data accentuated that the loading of the ECR (as reflected in the amplitude component) was higher than that seen for computer keyboard workers. The augmented loading of the ECR and reduced blood flow to forearm muscles may be a factor in the development of PRMDs in pianists.

Perfusion of the skin's microcirculation after cold-water immersion (10°C) and partial-body cryotherapy (-135°C).

BACKGROUND: Investigations of the perfusion of the skin's microcirculation with laser speckle contrast imaging (LSCI) after cold treatments are rare. Therefore, the aim of this study was to compare the effects between cold-water immersion (CWI) conduction and partial-body cryotherapy (PBC) convection on perfusion of the microcirculation and skin temperature on the thigh. MATERIALS AND METHODS: Twenty healthy males were randomly allocated to CWI (10°C for 10 minutes) or PBC (-60°C for 30 seconds, -135°C for 2 minutes). Perfusion and skin temperature measurements were conducted on the anterior thigh region up to 60 minutes post-treatment. RESULTS: Cold-water immersion decreased perfusion of the microcirculation significantly compared to baseline values between 10 minutes (P = 0.003) and 30 minutes (P = 0.01) post-treatment. PBC increased perfusion of the microcirculation and decreased skin temperature only at the first measurement interval (0 minute, both P = 0.01) post-treatment. Additionally, local skin temperature was significantly decreased compared to baseline values only after CWI up to 30 minutes (P = 0.04) post-treatment. CONCLUSION: Cold-water immersion reduced local skin microcirculation and skin temperature while PBC only slightly increased the perfusion of the microcirculation immediately after the treatment. For cooling purposes, the conduction method seems superior compared to the convection method, assessed with a LSCI device.

Acute Injuries in Male Elite and Amateur Mountain Bikers: Results of a Survey.

Together with the growing popularity of mountain biking, the number of riders at risk for an acute injury has increased. A cross-sectional observational study was performed to describe the prevalence of acute injuries among elite and amateur riders and to determine predictive factors leading to a severe injury. A retrospective questionnaire was created comprising questions aiming on demographics, training volume, injury events and wearing of protective gear items. The survey was conducted during the Swiss Epic Mountain Bike Event in 2017. Complete data sets of male mountain bikers were used to determine prevalence. To evaluate injury related factors, only data sets reporting one or more injuries were included in the final analysis. Ninety-nine questionnaires were included to calculate the injury prevalence of 74% for elites and 69% for amateurs (p = 0.607). For the analysis of injury related factors 56 questionnaires were processed. Elites were significantly younger (p = 0.004) and had a significantly higher exposure time per year as amateurs (p < 0.001). The groups did not differ in number of injuries (p = 0.437) and number of severe injuries (p = 0.225). No predictive factors for a severe injury event were found. Both groups wore an equal amount of protective gear items (p = 0.846). A significant medium, respectively small correlation was found in both groups for mean hours of training per week and number of races per year (elites: r = 0.597, p = 0.023; amateurs: r = 0.428, p = 0.005). An equal prevalence of acute injuries was found in elite and amateur mountain bikers. Elites are at higher risk for an injury event due to their exposure time but do not suffer more or more severe injuries than amateurs.

Changes in balance coordination and transfer to an unlearned balance task after slackline training: a self-organizing map analysis.

How humans maintain balance and change postural control due to age, injury, immobility or training is one of the basic questions in motor control. One of the problems in understanding postural control is the large set of degrees of freedom in the human motor system. Therefore, a self-organizing map (SOM), a type of artificial neural network, was used in the present study to extract and visualize information about high-dimensional balance strategies before and after a 6-week slackline training intervention. Thirteen subjects performed a flamingo and slackline balance task before and after the training while full body kinematics were measured. Range of motion, velocity and frequency of the center of mass and joint angles from the pelvis, trunk and lower leg (45 variables) were calculated and subsequently analyzed with an SOM. Subjects increased their standing time significantly on the flamingo (average +2.93 s, Cohen's d = 1.04) and slackline (+9.55 s, d = 3.28) tasks, but the effect size was more than three times larger in the slackline. The SOM analysis, followed by a k-means clustering and marginal homogeneity test, showed that the balance coordination pattern was significantly different between pre- and post-test for the slackline task only (χ 2 = 82.247; p < 0.001). The shift in balance coordination on the slackline could be characterized by an increase in range of motion and a decrease in velocity and frequency in nearly all degrees of freedom simultaneously. The observation of low transfer of coordination strategies to the flamingo task adds further evidence for the task-specificity principle of balance training, meaning that slackline training alone will be insufficient to increase postural control in other challenging situations.

The effect of local skin cooling before a sustained, submaximal isometric contraction on fatigue and isometric quadriceps femoris performance: A randomized controlled trial.

The central- and peripheral mechanisms by which heat strain limits physical performance are not fully elucidated. Nevertheless, pre-cooling is often used in an attempt to improve subsequent performance. This study compared the effects of pre-cooling vs. a pre-thermoneutral application on central- and peripheral fatigue during 60% of isometric maximum voluntary contraction (MVC) of the right quadriceps femoris muscle. Furthermore, the effects between a pre-cooling and a pre-thermoneutral application on isometric MVC of the right quadriceps femoris muscle and subjective ratings of perceived exertion (RPE) were investigated. In this randomized controlled trial, 18 healthy adults voluntarily participated. The participants received either a cold (experimental) application (+8°C) or a thermoneutral (control) application (+32°C) for 20min on their right thigh (one cuff). After the application, central (fractal dimension - FD) and peripheral (muscle fiber conduction velocity - CV) fatigue was estimated using sEMG parameters during 60% of isometric MVC. Surface EMG signals were detected from the vastus medialis and lateralis using bidimensional arrays. Immediately after the submaximal contraction, isometric MVC and RPE were assessed. Participants receiving the cold application were able to maintain a 60% isometric MVC significantly longer when compared to the thermoneutral group (mean time: 78 vs. 46s; p=0.04). The thermoneutral application had no significant impact on central fatigue (p>0.05) compared to the cold application (p=0.03). However, signs of peripheral fatigue were significantly higher in the cold group compared to the thermoneutral group (p=0.008). Pre-cooling had no effect on isometric MVC of the right quadriceps muscle and ratings of perceived exertion. Pre-cooling attenuated central fatigue and led to significantly longer submaximal contraction times compared to the pre-thermoneutral application. These findings support the use of pre-cooling procedures prior to submaximal exercises of the quadriceps muscle compared to pre-thermoneutral applications.

Test-retest Reliability in Reporting the Pain Induced by a Pain Provocation Test: Further Validation of a Novel Approach for Pain Drawing Acquisition and Analysis.

BACKGROUND: Pain drawings (PD) are frequently used in research to illustrate the pain response to pain provocation tests. However, there is a lack of data on the reliability in defining the extent and location of pain. We investigated the test-retest reliability in reporting an acute painful sensation induced by a pain provocation test using a novel approach for PD acquisition and analysis in healthy volunteers. METHODS: Forty healthy volunteers participated. Each participant underwent 2 upper limb neurodynamic tests 1 (ULNT1), once to the point of pain onset (PO) and once until the point of submaximal pain (SP). After each ULNT1, participants completed 2 consecutive PD with an interval of 1 minute. Custom software was used to quantify the pain extent and analyze the pain overlap. The test-retest reliability of pain extent was examined using Intraclass Correlation Coefficient (ICC 2,1 ) and Bland-Altman plots. Pain location reliability was examined using the Jaccard similarity coefficient (JSC). RESULTS: The ICC values for PO and SP were 0.98 (95% CI: 0.96-0.99) and 0.97 (95% CI: 0.95-0.98), respectively. The mean difference and 95% limits of agreement (± 1.96 SD) in the Bland-Altman plots were 14 pixels (-1080;1110) for PO, and 145 (-1610;1900) for SP. The median JSCs (Q1;Q3) were 0.73 (0.64;0.80) for PO and 0.76 (0.65;0.79) for SP. CONCLUSIONS: Pain drawings is a reliable instrument to investigate pain extent and pain location in healthy individuals experiencing an acute painful sensation induced by a pain provocation test.

Prevalence of Myofascial Trigger Points in Spinal Disorders: A Systematic Review and Meta-Analysis.

OBJECTIVE: To retrieve, appraise, and synthesize the results of studies on the prevalence of active and latent myofascial trigger points (MTrPs) in subjects with spinal pain disorders. DATA SOURCES: The databases PubMed, Embase, and CINAHL were searched, with no date or language restrictions. Search terms included controlled and free-text terms for spinal disorders and MTrPs. Further searches were conducted in Google Scholar and by contacting 3 experts in the field. Citation tracking of eligible studies was performed. STUDY SELECTION: Two reviewers independently selected observational studies assessing the prevalence of active and/or latent MTrPs in at least 1 group of adults with a spinal disorder. Twelve studies met the eligibility criteria. DATA EXTRACTION: Methodologic quality was assessed by 2 reviewers independently using a modified version of the Downs and Black checklist. Two reviewers also used a customized form to extract studies and subjects' characteristics and the proportions of subjects with active and/or latent MTrPs in each muscle assessed. DATA SYNTHESIS: A meta-analysis was performed when there was sufficient clinical homogeneity in at least 2 studies for the same spinal disorder. The Grading of Recommendations Assessment, Development and Evaluation approach was used to rate the body of evidence in each meta-analysis. A qualitative description of the results of single studies was provided. Low-quality evidence underpinned pooled estimates of MTrPs in the upper-body muscles of subjects with chronic neck pain. The point prevalence of MTrPs in different muscles of other disorders (eg, whiplash-associated disorders, nonspecific low back pain) was extracted from single studies with low methodologic quality and small samples. Active MTrPs were found to be present in all assessed muscles of subjects diagnosed with different spinal pain disorders. Latent MTrPs were not consistently more prevalent in subjects with a spinal disorder than in healthy controls. CONCLUSIONS: The MTrPs point prevalence estimates in this review should be viewed with caution because future studies with large samples and high methodologic quality are likely to change them substantially.

Real-time sonoelastography using an external reference material: test-retest reliability of healthy Achilles tendons.

OBJECTIVE: To establish the test-retest reliability of sonoelastography (SE) on healthy Achilles tendons in contracted and relaxed states using an external reference system. MATERIALS AND METHODS: Forty-eight Achilles tendons from 24 healthy volunteers were assessed using ultrasound and real-time SE with an external reference material. Tendons were analyzed under relaxed and contracted conditions. Strain ratios between the tendons and the reference material were calculated. The intraclass correlation coefficient (ICC2.k) and Bland-Altman plot were used to assess test-retest reliability. RESULTS: The reliability of SE measurements under relaxed conditions ranged from high to very high, with an ICC2.k of 0.84 (95 % CI: 0.64-0.92) for reference material, 0.91 (95 % CI: 0.83-0.95) for Achilles tendons and 0.95 (95 % CI: 0.91-0.97) for Kager fat pads (KFP). The ICC2.k value for skin was 0.30 (95 % CI: -0.26 to 0.61). Reliability for measurements in the contracted state ranged from high to very high, with an ICC2.k of 0.93 (95 % CI: 0.87-0.96) for reference material, 0.72 (95 % CI: 0.50-0.84) for skin, 0.93 (95 % CI: 0.87-0.96) for Achilles tendons, and 0.81 (95 % CI: 0.66-0.89) for KFP. Reliability of the strain ratio (tendon/reference) under relaxed conditions was high with an ICC2.k of 0.87 (95 % CI: 0.75-0.93), and in the contracted state, it was very high with an ICC2.k of 0.94 (95 % CI: 0.90-0.97). CONCLUSION: Sonoelastography using an external reference material is a reliable and simple technique for the assessment of the elasticity of healthy Achilles tendons. The use of an external material as a reference, along with strain ratios, could provide a quantitative measure of elasticity.

Short-term cutaneous vasodilatory and thermosensory effects of topical methyl salicylate.

Introduction: Methyl salicylate, the main compound of wintergreen oil, is widely used in topical applications. However, its vascular and thermosensory effects are not fully understood. The primary aim was to investigate the effects of topical methyl salicylate on skin temperature (Tskin), skin microcirculation (MCskin) and muscle oxygen saturation (SmO2) compared to a placebo gel. The secondary aim was to assess thermosensory responses (thermal sensation, thermal comfort) and to explore to which extent these sensations correspond to the physiological responses over time. Methods: 21 healthy women (22.2 ± 2.9 years) participated in this single-blind, randomized controlled trial. Custom-made natural wintergreen oil (12.9%), containing methyl salicylate (>99%) and a placebo gel, 1 g each, were applied simultaneously to two paravertebral skin areas (5 cm × 10 cm, Th4-Th7). Tskin (infrared thermal imaging), MCskin (laser speckle contrast imaging) and SmO2 (deep tissue oxygenation monitoring) and thermosensation (Likert scales) were assessed at baseline (BL) and at 5-min intervals during a 45 min post-application period (T0-T45). Results: Both gels caused an initial decrease in Tskin, with Tskin(min) at T5 for both methyl salicylate (BL-T5: Δ-3.36°C) and placebo (BL-T5: Δ-3.90°C), followed by a gradual increase (p < .001). Methyl salicylate gel resulted in significantly higher Tskin than placebo between T5 and T40 (p < .05). For methyl salicylate, MCskin increased, with MCskin(max) at T5 (BL-T5: Δ88.7%). For placebo, MCskin decreased (BL-T5: Δ-17.5%), with significantly lower values compared to methyl salicylate between T0 and T45 (p < .05). Both gels had minimal effects on SmO2, with no significant differences between methyl salicylate and placebo (p > .05). Thermal sensation responses to topical methyl salicylate ranged from "cool" to "hot", with more intense sensations reported at T5. Discussion: The findings indicate that topical methyl salicylate induces short-term cutaneous vasodilation, but it may not enhance skeletal muscle blood flow. This study highlights the complex sensory responses to its application, which may be based on the short-term modulation of thermosensitive transient receptor potential channels.

Effects of 3-week repeated cold water immersion on leukocyte counts and cardiovascular factors: an exploratory study.

Aim: This exploratory study aimed to investigate the effects of a 3-week repeated cold water immersion (CWI) intervention on leukocyte counts and cardiovascular factors (mean arterial pressure [MAP], heart rate [HR]) in healthy men. Methods: A total of n = 12, non-cold-adapted men (age: 25.2 ± 4.0 years; height: 177.8 ± 5.6 cm; weight: 73.8 ± 6.5 kg) were randomly allocated to the CWI or control (CON) group. The CWI group underwent a 3-week repeated CWI intervention (12min at 7°C, 4x/week). The CON group did not receive any cold exposure or therapy. Total leukocyte numbers and proportions (neutrophils, basophils, eosinophils, monocytes, lymphocytes) and cardiovascular factors (MAP, HR) were assessed at baseline and after the 3-week intervention period. Results: Total leukocyte count decreased in CWI (p = 0.027, 95% CI -2.35 to -0.20 × 103/µL) and CON (p = 0.043, 95% CI -2.75 to -0.50 × 103/µL). CWI showed a decrease in neutrophil number (p = 0.028, 95% CI -1.55 to -0.25 × 103/µL) and proportion (p = 0.046, 95% CI -6.42 to 0.56%). In contrast, CON showed no significant change (p > 0.05). No differences were found for other leukocyte subtypes in CWI or CON (all p > 0.05). MAP (p = 0.028, 95% CI -17 to -8 mmHg) and HR (p = 0.027, 95% CI -7 to -2 bpm) were reduced in CWI, whereas CON showed no change (p > 0.05). Conclusion: The results suggest no relevant effects of 3-week repeated CWI on leukocyte counts in healthy men. Due to methodological limitations, the effects on the investigated cardiovascular factors remain unclear. Further studies with larger sample sizes are needed to examine the effects on immune function and cardiovascular health.

Hydration measurements of the stratum corneum: comparison between the capacitance method (digital version of the Corneometer CM 825®) and the impedance method (Skicon-200EX®).

BACKGROUND: Measurement of stratum corneum (SC) hydration often involves the use of commercial instruments. The aim of this study was to compare and validate two recent instruments: the Corneometer 825® (digital probe) and the Skicon-200 EX®. METHODS: In vitro calibration was carried out on filter pads using different solvents, measurements over different layers of plastic foils, and evaluation of desorption kinetics. In vivo measurements were carried out on skin sites covering a range of very dry to well-hydrated skin areas. RESULTS: Conductance measurements are influenced by electrolytes while capacitance measurements are not. Dielectric constant of the solvents influences the values of both instruments (r respectively 0.92 and 0.99). The capacitance method carries information from deeper layers (up to 45 µm) compared with the conductance instrument (up to 15 µm). Desorption experiments show a strong relation between the amount of water and respectively the capacitance and the conductance values. The in vivo experiments revealed a strong relation between the two methods (r = 0.97). Sensitivity of the capacitance method is limited for the highest hydration values. CONCLUSIONS: Both instruments allow a certain calibration and both give good estimates of the SC hydration.

Sex differences during a cold-stress test in normobaric and hypobaric hypoxia: A randomized controlled crossover study.

Cold and hypoxia are two stressors that are frequently combined and investigated in the scientific literature. Despite the growing literature regarding normobaric hypoxia (NH) and hypobaric hypoxia (HH), responses between females and males are less often evaluated. Therefore, this study aims to investigate the physiological sex differences following a cold-stress test under normoxia, normobaric- and hypobaric hypoxia. A total of n = 10 females (24.8 ± 5.1 years) and n = 10 males (30.3 ± 6.3 years) from a university population volunteered for this study. The cold-stress test (CST) of the right hand (15°C for 2 min) was performed using a randomised crossover design in normobaric normoxia, NH and HH. The change (∆) from baseline to post-CST up to 15 min was analysed for cutaneous vascular conductance (CVC) and the hands' skin temperature, whilst the mean values across time (post-CST up to 15 min) were assessed for peripheral oxygen saturation (SpO2), thermal sensation- and comfort. Pressure pain threshold (PPT) was assessed after the post-CST 15 min period. The hands' skin temperature drop was higher (p = 0.01) in the female group (∆3.3 ± 1.5°C) compared to the male group (∆1.9 ± 0.9°C) only in NH. Females (-0.9 ± 0.5) rated this temperature drop in NH to feel significantly colder (p = 0.02) compared to the males (-0.2 ± 0.7). No differences were observed between sexes in NN, NH, and HH for ∆CVC, SpO2, thermal comfort and PPT. In conclusion, females and males show similar reactions after a CST under normoxia and hypoxia. Sex differences were observed in the local skin temperature response and thermal sensation only in NH.

The Methodological Quality of Studies Investigating the Acute Effects of Exercise During Hypoxia Over the Past 40 years: A Systematic Review.

Exercise under hypoxia and the physiological impact compared to normoxia or hypoxia has gained attention in the last decades. However, methodological quality assessment of articles in this area is lacking in the literature. Therefore, this article aimed to evaluate the methodologic quality of trials studying exercise under hypoxia. An electronic search was conducted until December 2021. The search was conducted in PubMed, CENTRAL, and PEDro using the PICO model. (P) Participants had to be healthy, (I) exercise under normobaric or hypobaric hypoxia had to be (C) compared to exercise in normoxia or hypoxia on (O) any physiological outcome. The 11-item PEDro scale was used to assess the methodological quality (internal validity) of the studies. A linear regression model was used to evaluate the evolution of trials in this area, using the total PEDro score of the rated trials. A total of n = 81 studies met the inclusion criteria and were processed in this study. With a mean score of 5.1 ± 0.9 between the years 1982 and 2021, the mean methodological quality can be described as "fair." Only one study reached the highest score of 8/10, and n = 2 studies reached the lowest observed value of 3/10. The linear regression showed an increase of the PEDro score of 0.1 points per decade. A positive and small tendency toward increased methodologic quality was observed. The current results demonstrate that a positive and small tendency can be seen for the increase in the methodological quality in the field of exercise science under hypoxia. A "good" methodological quality, reaching a PEDro score of 6 points can be expected in the year 2063, using a linear regression model analysis. To accelerate this process, future research should ensure that methodological quality criteria are already included during the planning phase of a study.

The effects of normobaric and hypobaric hypoxia on cognitive performance and physiological responses: A crossover study.

This partially randomised controlled, crossover study sought to investigate the effects of normobaric hypoxia (NH) and hypobaric hypoxia (HH) on cognitive performance, the physiological response at rest and after a 3-min step-test. Twenty healthy participants (10 females and 10 males, 27.6±6.2yrs, 73.6±13.7kg, 175.3±8.9cm) completed a cognitive performance test, followed by the modified Harvard-step protocol, in four environments: normobaric normoxia (NN; PiO2: 146.0±1.5mmHg), NH (PiO2: 100.9±1.3mmHg), HH at the first day of ascent (HH1: PiO2 = 105.6±0.4mmHg) and HH after an overnight stay (HH2: PiO2 = 106.0±0.5mmHg). At rest and/or exercise, SpO2, NIRS, and cardiovascular and perceptual data were collected. The cerebral tissue oxygenation index and the cognitive performance (throughput, accuracy, and reaction time) were not different between the hypoxic conditions (all p>0.05). In NH, SpO2 was higher compared to HH1 (ΔSpO2 NH vs HH1: 1.7±0.5%, p = 0.003) whilst heart rate (ΔHR NH vs HH2: 5.8±2.6 bpm, p = 0.03) and sympathetic activation (ΔSNSi NH vs HH2: 0.8±0.4, p = 0.03) were lower in NH compared to HH2. Heart rate (ΔHR HH1 vs HH2: 6.9±2.6 bpm, p = 0.01) and sympathetic action (ΔSNSi HH1 vs HH2: 0.9±0.4, p = 0.02) were both lower in HH1 compared to HH2. In conclusion, cognitive performance and cerebral oxygenation didn't differ between the hypoxic conditions. SpO2 was only higher in NH compared to HH1. In HH2, heart rate and sympathetic activation were higher compared to both NH and HH1. These conclusions account for a PiO2 between 100-106 mmHg.