Relation between resting spleen volume and apnea-induced increases in hemoglobin mass.

Introduction: Indigenous populations renowned for apneic diving have comparatively large spleen volumes. It has been proposed that a larger spleen translates to heightened apnea-induced splenic contraction and elevations in circulating hemoglobin mass (Hbmass), which, in theory, improves O2 carrying and/or CO2/pH buffering capacities. However, the relation between resting spleen volume and apnea- induced increases in Hbmass is unknown. Therefore, we tested the hypothesis that resting spleen volume is positively related to apnea-induced increases in total Hbmass. Methods: Fourteen healthy adults (six women; 29 ± 5 years) completed a two-minute carbon monoxide rebreathe procedure to measure pre-apneas Hbmass and blood volume. Spleen length, width, and thickness were measured pre-and post-five maximal apneas via ultrasound. Spleen volume was calculated via the Pilström equation (test-retest CV:2 ± 2%). Hemoglobin concentration ([Hb]; g/dl) and hematocrit (%) were measured pre- and post-apneas via capillary blood samples. Post-apneas Hbmass was estimated as post-apnea [Hb] x pre-apnea blood volume. Data are presented as mean ± SD. Results: Spleen volume decreased from pre- (247 ± 95 mL) to post- (200 ± 82 mL, p<0.01) apneas. [Hb] (14.6 ± 1.2 vs. 14.9 ± 1.2 g/dL, p<0.01), hematocrit (44 ± 3 vs. 45 ± 3%, p=0.04), and Hbmass (1025 ± 322 vs. 1046 ± 339 g, p=0.03) increased from pre- to post-apneas. Pre-apneas spleen volume was unrelated to post-apneas increases in Hbmass (r=-0.02, p=0.47). O2 (+28 ± 31 mL, p<0.01) and CO2 (+31 ± 35 mL, p<0.01) carrying capacities increased post-apneas. Conclusion: Larger spleen volume is not associated with a greater rise in apneas-induced increases in Hbmass in non-apnea-trained healthy adults.

Acute moderate normobaric hypoxia does not modify circulating thyroid hormone concentrations induced by 1 h of head-out cold-water immersion.

This study tested the hypothesis that acute moderate normobaric hypoxia augments circulating thyroid hormone concentrations during and following 1 h of cold head-out water immersion (HOWI), compared with when cold HOWI is completed during normobaric normoxia. In a randomized crossover single-blind design, 12 healthy adults (27 ± 2 yr, 2 women) completed 1 h of cold (22.0 ± 0.1°C) HOWI breathing either normobaric normoxia ([Formula: see text] = 0.21) or normobaric hypoxia ([Formula: see text] = 0.14). Free and total thyroxine (T3) and triiodothyronine (T4), and thyroid-stimulating hormone (TSH) concentrations were measured in venous blood samples obtained before (baseline), during (15-, 30-, and 60 min), and 15 min following HOWI (post-), and were corrected for changes in plasma volume. Arterial oxyhemoglobin saturation and core (rectal) temperature were measured continuously. Arterial oxyhemoglobin saturation was lower during hypoxia (90 ± 3%) compared with normoxia (98 ± 1%, P < 0.001). Core temperature fell from baseline (normoxia: 37.2 ± 0.4°C, hypoxia: 37.2 ± 0.4°C) to post-cold HOWI (normoxia: 36.4 ± 0.5°C, hypoxia: 36.3 ± 0.5°C, P < 0.001) in both conditions but did not change differently between conditions (condition × time: P = 0.552). Circulating TSH, total T3, free T4, total T3, and free T4 concentrations demonstrated significant main effects of time (all P ≤ 0.024), but these changes did not differ between normoxic and hypoxic conditions (condition × time: all P ≥ 0.163). These data indicate that acute moderate normobaric hypoxia does not modify the circulating thyroid hormone response during 1 h of cold HOWI.NEW & NOTEWORTHY Acute head-out cold (22°C) water immersion (HOWI) decreased core temperature and increased thermogenesis. This thermogenic response was paralleled by the activation of the hypothalamic-pituitary-thyroid axis, as evidenced by changes in thyroid hormones. However, cold HOWI in combination with moderate normobaric hypoxia did not modify the thermogenic nor the circulating thyroid hormone response. This finding suggests that hypoxia-induced alterations in thyroid hormone concentrations are unlikely to acutely contribute to adaptations resulting from repeated cold-water exposures.

Arterial oxygen desaturation during moderate hypoxia hinders sensorimotor performance.

INTRODUCTION: Moderate hypoxia may impact cognitive and sensorimotor performance prior to self-recognized impairments. Therefore, rapid and objective assessment tools to identify people at risk of impaired function during moderate hypoxia is needed. PURPOSE: Test the hypothesis that reductions in arterial oxygen saturation during moderate normobaric hypoxia (FiO2 = 14%) decreases gamified sensorimotor performance as measured by alterations of motor acuity. METHODS: Following three consecutive days of practice, thirty healthy adults (25 ± 5 y, 10 females) completed three bouts of the tablet-based gamified assessment (Statespace Labs, Inc.) of motor acuity at Baseline and 60 and 90 min after exposure to 13.8 ± 0.2% (hypoxia) and 20.1 ± 0.4% (normoxia) oxygen. The gamified assessment involved moving the tablet to aim and shoot at targets. Both conditions were completed on the same day and were administered in a single-blind, block randomized manner. Performance metrics included shot time and shot variability. Arterial oxyhemoglobin saturation estimated via forehead pulse oximetry (SpO2). Data were analyzed using linear mixed effects models. RESULTS: Compared to normoxia (99±1%), SpO2 was lower (p<0.001) at 60 (89±3%) and 90 (90±2%) min of hypoxia. Shot time was unaffected by decreases in SpO2 (0.012, p = 0.19). Nor was shot time affected by the interaction between SpO2 decrease and baseline performance (0.006, p = 0.46). Shot variability was greater (i.e., less precision, worse performance) with decreases in SpO2 (0.023, p = 0.02) and depended on the interaction between SpO2 decrease and baseline performance (0.029, p< 0.01). CONCLUSION: Decreases in SpO2 during moderate hypoxic exposure hinders sensorimotor performance via decreased motor acuity, i.e., greater variability (less precision) with no change in speed with differing decreases in SpO2. Thus, personnel who are exposed to moderate hypoxia and have greater decreases in SpO2 exhibit lower motor acuity, i.e., less precise movements even though decision time and movement speed are unaffected.

Gamified assessment of cognitive performance during moderate hypoxia.

INTRODUCTION: There is a need for rapid and objective assessment tools to identify people at risk of impaired cognitive function during hypoxia. PURPOSE: To test the hypotheses that performance on gamified cognitive tests examining the cognitive domains of executive function (Gridshot), working memory (Capacity) and spatial tracking (Multitracker) will be reduced during normobaric exposure to moderate normobaric hypoxia. METHODS: Following three consecutive days of practice, twenty-one healthy adults (27 ± 5 y, 9 females) completed five 1-min rounds of the tablet-based games Gridshot, Capacity, and Multitracker (Statespace Labs, Inc.) at Baseline and 60 and 90 min after exposure to 14.0 ± 0.2% (hypoxia) and 20.6 ± 0.3% (normoxia) oxygen. Both conditions were completed on the same day and were administered in a single-blind, block randomized manner. Arterial oxyhemoglobin saturation was estimated via forehead pulse oximetry (SpO2). Data were analyzed using ANCOVA with a covariate of Baseline. RESULTS: Compared to normoxia (98 ± 1%), SpO2 was lower (p < 0.001) at 60 (91 ± 3%) and 90 (91 ± 2%) min of hypoxia. No condition x time interaction effects were identified for any gamified cognitive tests (p ≥ 0.32). A main effect of condition was identified for Capacity (p = 0.05) and Multitracker (p = 0.04), but not Gridshot (p = 0.33). Post hoc analyses of the composite scores for both Capacity (p = 0.11) and Multitracker (p = 0.73) demonstrated no difference between conditions. CONCLUSION: Performance on gamified cognitive tests was not consistently affected by acute normobaric moderate hypoxic exposure.

Elevations in sweat sodium concentration following ischemia-reperfusion injury during passive heat stress.

Renal ischemia-reperfusion (I/R) injury results in damage to the renal tubules and causes impairments in sodium [Na+] reabsorption. Given the inability to conduct mechanistic renal I/R injury studies in vivo in humans, eccrine sweat glands have been proposed as a surrogate model given the anatomical and physiological similarities. We tested the hypothesis that sweat Na+ concentration is elevated following I/R injury during passive heat stress. We also tested the hypothesis that I/R injury during heat stress will impair cutaneous microvascular function. Fifteen young healthy adults completed ∼160 min of passive heat stress using a water-perfused suit (50°C). At 60 min of whole body heating, one upper arm was occluded for 20 min followed by a 20-min reperfusion. Sweat was collected from each forearm via an absorbent patch pre- and post-I/R. Following the 20-min reperfusion, cutaneous microvascular function was measured via local heating protocol. Cutaneous vascular conductance (CVC) was calculated as red blood cell flux/mean arterial pressure and normalized to CVC during local heating to 44°C. Na+ concentration was log-transformed and data were reported as a mean change from pre-I/R (95% confidence interval). Changes in sweat sodium concentration from pre-I/R differed between arms post-I/R (experimental arm: +0.97 [+0.67 - 1.27] [LOG] Na+; control arm: +0.68 [+0.38 - 0.99] [LOG] Na+; P < 0.01). However, CVC during the local heating was not different between the experimental (80 ± 10%max) and control arms (78 ± 10%max; P = 0.59). In support of our hypothesis, Na+ concentration was elevated following I/R injury, but likely not accompanied by alterations in cutaneous microvascular function.NEW & NOTEWORTHY In the present study, we have demonstrated that sweat sodium concentration is elevated following ischemia-reperfusion injury during passive heat stress. This does not appear to be mediated by reductions in cutaneous microvascular function or active sweat glands, but may be related to alterations in local sweating responses during heat stress. This study demonstrates a potential use of eccrine sweat glands to understand sodium handling following ischemia-reperfusion injury, particularly given the challenges of in vivo studies of renal ischemia-reperfusion injury in humans.

Increased spleen volume provoked by temperate head-out-of-water immersion.

This study tested the hypotheses that 1) spleen volume increases during head-out-of-water immersion (HOWI) and returns to pre-HOWI values postdiuresis, and 2) the magnitude of apnea-induced spleen contraction increases when preapnea spleen volume is elevated. Spleen volume was measured before and after a set of five apneas in 12 healthy adults (28 ± 5 yr, 3 females) before, during (at 30 and 150 min), and 20 min after temperate temperature (36 ± 1°C) HOWI. At each time point, spleen length, width, and thickness were measured via ultrasound, and spleen volume was calculated using the Pilström equation. Compared with pre-HOWI (276 ± 88 mL), spleen volume was elevated at 30 (353 ± 94 mL, P < 0.01) and 150 (322 ± 87 mL, P < 0.01) min of HOWI but returned to pre-HOWI volume at post-HOWI (281 ± 90 mL, P = 0.58). Spleen volume decreased from pre- to postapnea bouts at each time point (P < 0.01). The magnitude of reduction in spleen volume from pre- to postapneas was elevated at 30 min of HOWI (-69 ± 24 mL) compared with pre-HOWI (-52 ± 20 mL, P = 0.04) but did not differ from pre-HOWI at 150 min of HOWI (-54 ± 16 mL, P = 0.99) and post-HOWI (-50 ± 18 mL, P = 0.87). Thus, spleen volume is increased throughout 180 min of HOWI, and whereas apnea-induced spleen contraction is augmented after 30 min of HOWI, the magnitude of spleen contraction is unaffected by HOWI thereafter.

Cardiorespiratory Fitness Is Inversely Associated With Aortic Arterial Stiffness in Firefighters.

OBJECTIVES: The aim of this study was to determine whether cardiorespiratory fitness (CRF), expressed as VO 2 max (mL/kg/min), is associated with resting AS (carotid-femoral pulse wave velocity [cf-PWV]) and the AS response to simulated fire suppression activities in firefighters. METHODS: In firefighters (n = 20, 34 ± 8 years), AS was determined using cf-PWV (m/s) before and after a fire simulation exercise. VO 2 max was determined using a standard treadmill protocol. Linear regression models, adjusted for body fat percentage, are reported as unstandardized (b) and standardized (ß) betas (effect sizes). RESULTS: H1: there was a moderate (ie, ß = 0.5-0.8), inverse association between cf-PWV and VO 2 max (b = -0.80; 95% confidence interval [CI], -0.14 to -0.02; ß = 0.71). H2: there was a moderate, positive association between ∆cf-PWV and VO 2 max (b = 0.05; 95% CI, 0.00-0.10; ß = 0.62). CONCLUSIONS: These findings indicate that CRF may protect against arterial stiffening in firefighters.

The Effect of Tactical Tasks and Gear on Muscle Activation of SWAT Officers.

ABSTRACT: Keeler, JM, Pohl, MB, Bergstrom, HC, Thomas, JM, and Abel, MG. The effect of tactical tasks and gear on muscle activation of SWAT officers. J Strength Cond Res 36(1): 238-244, 2022-Special Weapons and Tactics (SWAT) officers perform a variety of tactical operations while wearing tactical gear. Load carriage has been shown to alter muscle activation in the torso and is also associated with lower back pain, which is a prevalent musculoskeletal injury suffered by SWAT Officers. The purpose of this study was to quantify the effect of tactical gear on muscle activation of torso musculature while performing occupational tasks. Twenty male SWAT Officers (age: 34.7 ± 4.5 years; height: 1.79 ± 0.1 m; body mass: 91.5 ± 17.3 kg) performed 4 tasks (standing, rifle walk, sitting, and shield walk) with and without gear (mass of gear: 13.8 ± 1.9 kg). Mean electromyographic amplitude was evaluated bilaterally for the erector spinae, rectus abdominis, and external oblique muscles during the trials and expressed relative to maximal voluntary isometric contraction (MVIC). Addition of gear significantly increased erector spinae mean muscle activation during the rifle walk task (mean delta: +0.16%). However, no differences in muscle activation were identified for any other muscles between gear conditions (effect size ≤ 0.15). The shield walk produced the highest mean activation for each muscle during different tasks. The dynamic tasks yielded (0.24-4.18% MVIC) greater muscle activation levels than sitting and standing tasks. Despite minimal increases in muscle activation levels with the addition of gear, load carriage is known to increase the risk of acute and chronic injury. Collectively, these findings indicate that SWAT Officers should perform most skills without gear during tactical training to simulate task-specific movement patterns but reduce the risk of musculoskeletal injury.

Music Therapy and Family-Integrated Care in the NICU: Using Heartbeat-Music Interventions to Promote Mother-Infant Bonding.

BACKGROUND: Family-integrated care in the neonatal intensive care unit (NICU) is the criterion standard. Parent-infant bonding may be an indicator of successful family involvement. Music therapy (MT) is a growing service in the NICU, with interventions to support meaningful family involvement and improve bonding. PURPOSE: To study the effects of heartbeat-music interventions to support mother-infant bonding in the NICU and explore experiences of mothers participating in MT. METHODS: Parallel-group randomized trial (MT vs standard care) to compare Mother-to-Infant Bonding Scale (MIBS) scores from baseline to 1 week postenrollment. MT included 2 heartbeat-music interventions (recorded maternal lullaby and heartbeat for infants, and recorded infant heartbeat and preferred music for mothers). Five mothers were randomly asked to complete a survey regarding their experiences with MT services. RESULTS: One hundred mothers enrolled. In total, 44.3% completed the MIBS follow-up. Covarying out baseline MIBS, one-way analysis of covariance found no statistical difference between groups for MIBS 1-week follow-up (MT: mean = 0.64, SD = 1.6; standard care: mean = 0.57, SD = 1.5; P = .60) but underpowered in post hoc. Comforting, family cohesion, and personal growth and development themes emerged in qualitative analysis of survey responses. IMPLICATIONS FOR PRACTICE: MT remains a viable service for purposefully including parents in the care of their NICU infants. Nurses and music therapists must work closely to successfully implement meaningful interventions such as heartbeat-music. IMPLICATIONS FOR RESEARCH: Heartbeat-music interventions should be further studied for diverse applications, including family integration, family coping, and bereavement.

Predictors of Arterial Stiffness in Law Enforcement Officers.

BACKGROUND: Compare arterial stiffness among law enforcement officers (LEOs) versus general population normative values and identify predictors of arterial stiffness in LEOs. METHODS: Seventy male LEOs (age: 24-54 years) completed body composition, blood pressures, physical activity level, and carotid-femoral pulse wave velocity (cfPWV) measurements. T-tests and regression analyses were utilized to compare LEO data to normative data and predict cfPWV, respectively. RESULTS: Compared to similar age strata within the general population, cfPWV was lower among LEO's under 30-years (mean difference = -0.6 m·s-1), but higher among LEOs 50-55-years (mean difference = 1.1 m·s-1). Utilizing regression, age, relative body fat, and diastolic blood pressure explained the greatest variance in LEO's cfPWV (adj. R2 = 0.56, p < 0.001). CONCLUSION: This investigation demonstrated that arterial stiffness may progress more rapidly in LEOs and LEOs' relative body fat and blood pressure may primarily affect arterial stiffness and risk of CVD.

Cutaneous microvascular vasodilatory consequences of acute consumption of a caffeinated soft drink sweetened with high-fructose corn syrup.

This study tested the hypotheses that compared to drinking water, consumption of a caffeinated soft drink sweetened with high-fructose corn syrup (HFCS) attenuates the cutaneous vasodilatory response to local skin heating without (Protocol 1) and following ischemia-reperfusion injury (Protocol 2). In a randomized, counterbalanced crossover design, 14 healthy adults (25 ± 3 year, 6 women) consumed 500 ml of water (water) or a caffeinated soft drink sweetened with HFCS (Mtn. Dew, DEW). Thirty minutes following beverage consumption local skin heating commenced on the right forearm (Protocol 1), while on the left forearm ischemia-reperfusion commenced with 20 min of ischemia followed by 20 min of reperfusion and then local skin heating (Protocol 2). Local skin heating involved 40 min of heating to 39℃ followed by 20 min of heating to 44℃. Skin blood flow (SkBf, laser Doppler) data were normalized to mean arterial pressure and are presented as a cutaneous vascular conductance (CVC) and as percentage of the CVC response during heating to 44℃ (%CVCmax ). Protocol 1: During local heating at 39℃, no differences were observed in CVC (water: 2.0 ± 0.6 PU/mmHg; DEW: 2.0 ± 0.8 PU/mmHg, p = 0.83) or %CVCmax (water: 59 ± 14%; DEW 60 ± 15%, p = 0.84) between trials. Protocol 2: During local skin heating at 39℃, no differences were observed in CVC (water: 1.7 ± 0.5 PU/mmHg; DEW: 1.5 ± 0.5 PU/mmHg, p = 0.33) or %CVCmax (water: 64 ± 15%; DEW 61 ± 15% p = 0.62) between trials. The cutaneous microvascular vasodilator response to local heating with or without prior ischemia-reperfusion injury is not affected by acute consumption of a caffeinated soft drink sweetened with HFCS.

Predictors of Work Efficiency in Structural Firefighters.

OBJECTIVE: Develop a novel work efficiency (WE) metric to quantify firefighter physical ability and identify correlates of WE. METHODS: Physical fitness and anthropometric measurements were taken on 19 male firefighters. Firefighters performed a timed maximal effort simulated fireground test (SFGT). WE was quantified as: (1/[Air depletion × SFGT completion time]) × 10,000. Regression analyses were used to identify predictors of WE. RESULTS: WE was significantly correlated to age, relative body fat, fat mass, occupational experience, jump height, inverted row repetitions, relative bench press and squat strength, treadmill time to exhaustion, relative ventilatory threshold, and relative peak oxygen consumption. Treadmill time to exhaustion and relative lower body strength accounted for the greatest variance in WE (R2 = 0.72, root mean square error = 0.07). CONCLUSION: Aerobic endurance and relative lower body strength were related to an occupationally-specific assessment of firefighter physical ability.

Music therapy and retinopathy of prematurity screening: using recorded maternal singing and heartbeat for post exam recovery.

OBJECTIVE: Explore a music therapy (MT) intervention to support infant recovery post retinopathy of prematurity (ROP) exam. STUDY DESIGN: Prospective, double-masked, randomized, parallel group study of 100 preterm infants exposed to MT (recorded maternal singing/heartbeat) or standard care (SC). Premature Infant Pain Profile (PIPP) measured at: baseline, during the exam, and 1 and 5 min post exam. RESULTS: Recovery PIPP scores were less with MT vs. SC, but statistical significance not achieved (Mean ± sd: MT 1 min [5.81 ± 2.93] and 5 min [3.91 ± 1.73] vs. SC 1 min [6.40 ± 2.78] and 5 min [4.76 ± 2.07], p = 0.07). Recovery PIPP sores were significantly higher with SC compared to MT when eye exams were longer (p = 0.049) or when exams were more painful (p = 0.04). CONCLUSION: Recorded maternal singing and heartbeat can support recovery post ROP exam. For longer/more painful ROP exams, MT may be more effective than SC promoting recovery post exam.

Development and Deployment of Air-Launched Drifters from Small UAS.

Supercell thunderstorms can form extremely dangerous and destructive tornadoes. While high fidelity supercell simulations have increased the understanding of supercell mechanics to help determine how and when tornadoes form, there is a lack of targeted, in situ measurements taken aboveground in supercells to validate these simulations. Pseudo-Lagrangian drifters (PLDs) are atmospheric probes that can be used to attain thermodynamic measurements in areas that are difficult or dangerous to access, such as from within supercells. Of particular interest in understanding tornadogenesis is the rear-flank downdraft (RFD). However, strong outflow winds behind the rear-flank gust front (RFGF) make the RFD particularly difficult to access with balloon-borne sensors launched from the ground. A specific type of PLD, an air-launched drifter (ALD) that is released from unmanned aircraft systems (UAS), can be used to access RFD inflows, present at higher altitudes. Results from initial tests of ALDs are shown, along with results from a ground-released PLD test during a supercell intercept in the Oklahoma Panhandle on 12 June 2018. In characterization tests performed at the 2018 International Society for Atmospheric Research using Remotely piloted Aircraft (ISARRA) flight week, it was found that the ALD sensor system performs reasonably well against industry standards. However, improvements will be made to increase the aspiration of the sensor.

Effect of Load Carriage on Tactical Performance in Special Weapons and Tactics Operators.

Thomas, JM, Pohl, MB, Shapiro, R, Keeler, J, and Abel, MG. Effect of load carriage on tactical performance in special weapons and tactics operators. J Strength Cond Res 32(2): 554-564, 2018-Special weapons and tactics (SWAT) operators are specially trained personnel that are required to carry equipment to perform high-risk tasks. Given the need to carry this equipment, it is important to understand the potentially deleterious effect that the additional load may have on tactical performance. Furthermore, it is important to identify physical fitness characteristics that are associated with the potential decrement in performance. Therefore, the purpose of this study was to evaluate the effect of load carriage on tactical physical ability and marksmanship and to identify fitness characteristics associated with any decrement in performance. Twelve male SWAT operators were timed while performing a simulated tactical test (STT) on a live firing range with (loaded condition) and without equipment (unloaded condition). A battery of physical fitness assessments were used to assess anaerobic and aerobic power, muscular endurance, strength, agility, and flexibility. Paired-samples t-tests were used to identify differences between STT conditions, and bivariate correlations were used to determine relationships between STT and fitness outcomes. Time to complete the STT in the loaded condition increased by 7.8% compared with the unloaded condition (p < 0.001). Nine of the 13 STT tasks were performed significantly slower in the loaded condition. Fatigue index (r = 0.64) and V[Combining Dot Above]O2peak (r = -0.62) were associated with the decrement in the overall STT time. Marksmanship was not different between load carriage conditions (p = 0.816). These findings indicate that resistance to anaerobic fatigue and aerobic power are related to the decrement in tactical performance produced by load carriage.

The neurochemistry and social flow of singing: bonding and oxytocin.

Music is used in healthcare to promote physical and psychological well-being. As clinical applications of music continue to expand, there is a growing need to understand the biological mechanisms by which music influences health. Here we explore the neurochemistry and social flow of group singing. Four participants from a vocal jazz ensemble were conveniently sampled to sing together in two separate performances: pre-composed and improvised. Concentrations of plasma oxytocin and adrenocorticotropic hormone (ACTH) were measured before and after each singing condition to assess levels of social affiliation, engagement and arousal. A validated assessment of flow state was administered after each singing condition to assess participants' absorption in the task. The feasibility of the research methods were assessed and initial neurochemical data was generated on group singing. Mean scores of the flow state scale indicated that participants experienced flow in both the pre-composed (M = 37.06) and improvised singing conditions (M = 34.25), with no significant difference between conditions. ACTH concentrations decreased in both conditions, significantly so in the pre-composed singing condition, which may have contributed to the social flow experience. Mean plasma oxytocin levels increased only in response to improvised singing, with no significant difference between improvised and pre-composed singing conditions observed. The results indicate that group singing reduces stress and arousal, as measured by ACTH, and induces social flow in participants. The effects of pre-composed and improvised group singing on oxytocin are less clear. Higher levels of plasma oxytocin in the improvised condition may perhaps be attributed to the social effects of improvising musically with others. Further research with a larger sample size is warranted.

Absence of the fourth tendon of the flexor digitorum brevis muscle: a cadaveric study.

UNLABELLED: This study was undertaken to help confirm the percentages concerning the presence or absence of the flexor digitorum brevis muscle tendon to the fifth toe. We also hope to be able to determine the presence based on gender and nationality. It is known to be absent occasionally; however, there is no definitive study dedicated to its prevalence. Using a pool of 60 cadavers, 97 total feet were included in our analysis. Of these feet, 47 (48%) lacked a flexor digitorum brevis tendon to the fifth toe at all. Furthermore, 25 (26%) had notably small tendons to the fifth toe. The final 25 (26%) had what the researchers deemed present tendons. This information could be helpful in surgical planning, including tendon transfer techniques, and biomechanical evaluations. Further research would need to be conducted as this was a cadaveric study. LEVELS OF EVIDENCE: Cadaver/anatomy research, Level V.