Comparison of lower- vs. upper-body cooling during arm exercise in hot conditions

INTRODUCTION: Studies examining cooling strategies and exercise have generally employed lower-body exercise despite the fact that arm exercise is an important mode for many industrial tasks and disabled populations. The aim of this study was to determine the effects of two cooling strategies during arm exercise in the heat. METHODS: There were eight male subjects (mean +/- SD age 24.5 +/- 4.0 yr, weight 81.0 +/- 7.8 kg, upper-body VO2peak 3.13 +/- 0.50 L x min(-1)) who volunteered for this study. Subjects undertook arm crank exercise for 30 min (50% VO2peak) in a hot environment (40.2 +/- 0.4 degrees C, 38.7 +/- 7.4% RH) on three occasions (no cooling control, CON; lower-body cooling, LC; upper-body cooling, UC). RESULTS: No differences were observed between trials for oxygen consumption, respiratory exchange rate (RER), or blood lactate. Heart rate (HR) was greatest during CON (151 +/- 11 bpm) when compared with UC and LC (148 +/- 16 and 138 +/- 13 bpm; p < 0.05). Mean skin temperature was warmer during CON (36.3 +/- 0.5 degrees C) when compared with UC (31.2 +/- 1.4 degrees C, p < 0.05), which was warmer than during LC (28.5 +/- 1.3 degrees C, p < 0.05). No differences were observed for rectal or aural temperatures between trials. At the end of exercise, heat storage was hyperthermic (3.04 +/- 0.68 J x g(-1)), thermoneutral (0.18 +/- 1.21 J x g(-1)), and hypothermic (-2.37 +/- 0.81 J x g(-1)) during CON, UC, and LC, respectively (p < 0.05). Perceived exertion was lowest during LC and greatest during CON (p < 0.05). CONCLUSIONS: The results of this study suggest that cooling the lower body during arm exercise in hot conditions is more effective in reducing physiological and thermal strain than cooling the upper body.     

Hypercapnia effect on core cooling and shivering threshold during snow burial

INTRODUCTION: Hypercapnia during avalanche burial may increase core temperature cooling rate by decreasing the temperature threshold for shivering or by increasing respiratory heat loss. METHODS: We studied the effect of hypercapnia on rectal core temperature (T(re)) cooling rate, respiratory heat loss, heat production, and the T(re) shivering threshold during snow burial (mean snow temperature -3.2 + 2.7 degrees C) in 11 subjects. In a 60-min hypercapnic burial subjects breathed a 5% carbon dioxide and 21% oxygen inhaled gas mixture and in a separate 60-min normocapnic burial subjects breathed ambient air. After extrication from snow burial subjects were passively rewarmed in a 15 degrees C shelter and T(re) afterdrop was measured. RESULTS: The deltaT(re) over 1 h of burial in the hypercapnic study was 1.28 +/- 0.4 degrees C and in the normocapnic study was 0.97 +/- 0.4 degrees C (P = 0.045). Minute ventilation, respiratory heat loss, total metabolic rate, and metabolic rate of the respiratory muscles were greater during the hypercapnic burial. There was no difference in shivering threshold between the hypercapnic and normocapnic conditions. Afterdrop in the hypercapnic study (0.69 +/- 0.4 degrees C at 21 +/- 8.1 min after extrication) was not different than in the normocapnic study (0.86 +/- 0.3 degrees C at 23.1 +/- 5.3 min after extrication). In both the hypercapnic and normocapnic studies afterdrop cooling rate was significantly greater during extrication than during snow burial. DISCUSSION: Hypercapnia significantly increased T(re) cooling rate by increasing respiratory heat loss but did not suppress shivering. Afterdrop may significantly contribute to hypothermia during rescue of avalanche burial victims.     

Acceleration effects on neck muscle strength: pilots vs. non-pilots

BACKGROUND: Conditioning of neck muscles, if any, due to repeated exposures to +Gz forces has received little research attention. OBJECTIVE: This study was conducted to evaluate and compare the neck muscle strength of test volunteers representative of the general populations of fighter aircraft pilots and non-pilots. METHODS: The tests were performed using a special attachment device on a computerized dynamometer. Ten pilots and ten non-pilots volunteered as test subjects. Each individual's maximal isometric neck muscle strength was evaluated in the extension, flexion, and left and right lateral bending directions in a single day. Peak values from the measurements were used for data analysis. Overall neck strength was calculated as the mean values for the four directions in each group. RESULTS: The overall muscular strength of the necks of pilots did not differ significantly from that of non-pilots, nor did exposure to +Gz forces lead to specific changes in isometric muscle strength across any of the four principal directions. Neck muscle strength in the four measured directions pooled across the two subgroups were statistically significant. The widespread practice of adopting protective head-positioning strategies to minimize neck strains, coupled with results from this research study, suggest that the neck muscles are subjected to reduced in-flight strengthening workouts during exposures to +Gz forces. CONCLUSIONS: To maximize in-flight performance and minimize +Gz-induced neck injuries, fighter pilots should be encouraged to perform on-land neck muscle strengthening exercise and in-flight head-positioning techniques. More research is needed to fine-tune this countermeasure strategy against cervical spine injury.     

Modafinil vs. caffeine: effects on fatigue during sleep deprivation

INTRODUCTION: The extent to which modafinil and caffeine reverse fatigue effects (defined as performance decrements with time on task) during total sleep deprivation was investigated. METHODS: There were 50 healthy young adults who remained awake for 54.5 h (06:30 day 1 to 13:00 day 3). A 10-min vigilance test was administered bi-hourly from 08:00 day 1 until 22:00 day 2. At 23:55 day 2 (after 41.5 h awake), double-blind administration of one of five drug doses (placebo; modafinil 100, 200, or 400 mg; or caffeine 600 mg; n = 10 per group) was followed by hourly testing from 00:00 through 12:00 day 3. Response speed (reciprocal of reaction time) across the 10-min task (by 1-min block) was analyzed prior to and after drug administration. RESULTS: A fatigue effect (response speed degradation across the 10-min task) was exacerbated by sleep deprivation and circadian rhythmicity. Prior to the drug, this effect was maximal between 08:00 and 12:00 day 3 (24-28 h sleep deprivation). Modafinil 400 mg attenuated fatigue in a manner comparable to that seen with caffeine 600 mg; these effects were especially salient during the circadian nadir of performance (06:00 through 10:00); modafinil 200 mg also reversed fatigue, but for a shorter duration (3 min) than modafinil 400 mg (8 min) or caffeine 600 mg (6 min). DISCUSSION AND CONCLUSIONS: Time-on-task effects contributed to the performance degradation seen during sleep deprivation; effects which were reversed by caffeine and, at appropriate doses, by modafinil. Because the duration of efficacy for reversing time-on-task effects was shorter at lower drug dosages, the latter must be considered when determining the appropriate dose to use during sustained operations.     

Effect of a practical neck cooling device on core temperature during exercise

Previous studies have documented the effectiveness of combined head and neck cooling in reducing thermal stress during exercise. However, these studies investigated low intensity exercise and devices that are not practical for use on a widespread basis during recreational exercise. In the present study, we investigated the effect of a commercially available, practical neck cooling device on core temperature during strenuous exercise. In a randomized cross-over fashion, 10 male endurance athletes (age 29 +/- 2 yr) performed a 45-min submaximal run (Borg rating of perceived exertion approximately 15) at a constant speed, with and without neck cooling. Runs were conducted on an indoor track, where the ambient temperature was maintained at approximately 21 degrees C dry bulb and approximately 17 degrees C wet bulb. Exercise heart rates and subjective perception of effort were not significantly modified by neck cooling. In contrast, rectal temperature rises (by 0.21 degrees C or 9.5%, P less than 0.02) and sweat rates (by 92 ml.h-1 or 6.4%, P less than 0.02) were reduced by neck cooling. Our study therefore concludes that this practical neck cooling device is capable of inducing reductions in thermal stress during strenuous exercise that, although numerically small, are in a direction of potential benefit.     

Fear of flying treatment methods: virtual reality exposure vs. cognitive behavioral therapy

INTRODUCTION: Fear of flying (FOF) can be a serious problem for individuals who develop this condition and for military and civilian organizations that operate aircraft. The aim of this study was to compare the effectiveness of three treatments: bibliotherapy (BIB) without therapist contact; individualized virtual reality exposure therapy (VRE); and cognitive behavior therapy (CB). In addition, we evaluated the effect of following up VRE and CB with 2 d of group cognitive-behavioral training (GrCB). METHODS: There were 86 subjects suffering from FOF who entered the study; 19 BIB, 29 VRE, and 16 CB subjects completed the treatment protocols. The BIB subjects were then treated with VRE (n = 7) or CB (n = 12). There were 59 subjects who were then trained with GrCB. RESULTS: Treatment with VRE or CB was more effective than BIB. Both VRE and CB showed a decline in FOF on the two main outcome measures. There was no statistically significant difference between those two therapies. However, effect sizes were lower for VRE (small to moderate) than for CB (moderate) and the addition of GrCB had less effect for VRE than for CB. DISCUSSION: VRE holds promise as treatment for FOF, but in this trial CB followed by GrCB showed the largest decrease in subjective anxiety. The results suggest that future research should focus on comparing the effectiveness of VRE vs. VRE plus cognitive techniques or measure the effectiveness of each component of treatment. Moreover, the effectiveness of the GrCB as stand-alone treatment should be investigated, which might even be superior in cost-effectiveness.     

飞行员新型降温背心冷却效果的评定

目的评价一种以冰胶为制冷介质的降温背心的降温性能。方法试验环境温度为干球温度（Tdb）45℃，湿球温度（Twb）32℃（相对湿度50％）。受试者为6名男性青年。观察其加权平均皮肤温度（Ts）、躯干皮肤温度（Tt）、直肠温度、出汗量和综合热应激指数（CIHS），记录温度舒适性评价等级。结果对比受试者穿与不穿降温背心暴露热环境时的各项生理指标后，前者的各项生理指标均有显著和非常显著性降低，主观舒适性评分等级前者的也明显优于后者。但在使用降温背心过程中，存在受试者躯干局部皮肤温度偏低、感觉略凉的现象。结论该降温背心具有良好的降温性能。建议在重新设计时采取措施纠正躯干局部皮肤温度偏低的现象。     

Tetrahydrocannabinol vs. prochlorperazine. The effects of two antiemetics on patients undergoing radiotherapy

The authors tested the effectiveness of orally administered delta-9-tetrahydrocannabinol (THC) as compared to prochlorperazine for the alleviation of symptoms, such as vomiting and nausea, experienced by patients receiving radiotherapy. The test subjects rated the severity of their illness, as well as the extent of their subsequent moods, their level of concentration, their amount of physical activity, and their desire for social interaction. They chose the drug they preferred and recorded its side effects. The use of THC was slightly more beneficial than the use of prochlorperazine.     

Diagnostic potential of virtual cystoscopy of the bladder: MRI vs CT. Preliminary report

The aim of the study was to evaluate the diagnostic potential of the half-Fourier acquired single-shot turbo spin echo (HASTE) sequence for MRI cystoscopy compared with CT cystoscopy and the gold standard conventional cystoscopy. The MRI- and CT cystoscopy was performed in 29 patients with bladder tumors documented at cystoscopy and a control group using a 1.5-T unit (6-mm slice thickness) and a helical CT (3-mm collimation, pitch 1) after filling the bladder with air. Axial MRI and CT images were transferred to a workstation for application of virtual cystoscopy and compared with routine cystoscopy. Axial images and virtual cystoscopies were read by three readers for size and location of tumors. Forty-seven tumors were diagnosed at cystoscopy (12<1 cm, 35≥1 cm). The sensitivity for detection of tumors smaller than 1 cm was 88.9% at MRI cystoscopy and 100% for tumors of 1 cm or larger. These results were not statistically different from the other modalities. Three tumors smaller than 1 cm were not detected at CT cystoscopy, four not all identical at MRI cystoscopy. One tumor with a wall thickening was detected on axial CT and MR images and CT cystoscopy by all observers, but only by two at MRI cystoscopy. The MRI cystoscopy is a diagnostic modality with results comparable to conventional and CT cystoscopy. Electronic Publication     

Comparison of efficacy and safety of low-dose-rate vs. high-dose-rate intraluminal brachytherapy boost in patients with superficial esophageal cancer

PurposeTo compare the efficacy and the incidence of complications of high-dose-rate (HDR) and low-dose-rate (LDR) intraluminal brachytherapy (IBT) boost after external beam radiation therapy in patients with superficial esophageal cancer.Methods and MaterialsFifty-four consecutive patients with Stage I thoracic esophageal squamous cell carcinoma who were treated with definitive radiotherapy using IBT between 1991 and 2007 were studied retrospectively. LDR-IBT and HDR-IBT were performed for 19 and 35 patients, respectively. After external beam radiation therapy of 56–60 Gy with a conventional fractionation, LDR-IBT (5 Gy × 2) or HDR-IBT (3 Gy × 3) was given within 2 weeks. The median follow-up was 47 months (7–151 months).ResultsOverall, the 5-year overall survival, cause-specific survival (CSS), and locoregional control (LRC) rates were 61%, 86%, and 79%, respectively. The 5-year overall survival, CCS, and LRC rates did not differ significantly between the LDR-IBT and HDR-IBT groups (68% vs. 58% (p = 0.50), 83% vs. 85% (p = 0.63), and 84% vs. 75% (p = 0.42), respectively). Salvage treatment was given in 8 locally recurrent patients, and 6 patients were rescued. The Grade ≥2 late morbidities of esophagus and heart/lung were observed in 5 patients (4 in the LDR-IBT group and 1 in the HDR-IBT group) and 2 patients (one from each group), respectively.ConclusionsIn view of the safety profile and effectiveness, our results encourage the continued adoption of HDR-IBT as radiation boost in medically inoperable or elderly superficial esophageal cancer patients undergoing definitive radiotherapy.     

Long-term effects of low-dose proton radiation on immunity in mice: shielded vs. unshielded

BACKGROUND: Outside the protection of the terrestrial environment, astronauts on any long-term missions will unavoidably be exposed to fields of charged particle radiation dominated by protons. These fields and their biological risks are modified in complex ways by the presence of protective shielding. METHODS: To examine the long-term effects of space-like proton exposures on immune status, we treated female C57BL/6 mice with 3 or 4 Gy of 250 MeV monoenergetic protons or the complex space-like radiation field produced after 250 MeV protons are transported through 15 g x cm(-2) aluminum shielding. The animals were euthanized 122 d post-irradiation and lymphocyte phenotypes, hematological parameters, and lymphocyte blastogenesis were characterized. RESULTS: There were significant dose-dependent decreases in macrophage, CD3+/CD8+ T, NK, platelet, and red blood cell populations, as well as low hematocrit and hemoglobin levels. In contrast, dose-dependent increases in spontaneous, but not mitogen-induced, blastogenesis were noted. The differences in dose composition between pristine and shielded proton fields did not lead to significant effects in most measures, but did result in significant changes in monocyte and macrophage populations and spontaneous blastogenesis in the spleen. CONCLUSIONS: The data indicate that whole body exposure to proton radiation at doses of the order of large solar particle events or clinical treatment fractions may have long-term effects on immune system status.     

The effects of roll vs. pitch rotation in humans under orthostatic stress.

BACKGROUND: It has been known since 1953 that pre-exposure to less than +1 Gz will reduce subsequent +Gz-tolerance. With few exceptions, during operational flying, the transition from hypogravity to hypergravity involves roll as well as pitch rotation. We examined the effect of roll vs. pitch rotation while undergoing transition from hypogravity to +1 Gz on a tilt table. METHODS: Twelve subjects (28-47 yr old) were rotated at 45 degrees x s(-1) from head-up (HU) at 15 degrees relative to gravitational vertical to 135 degrees head-down (HD) and back to the HU position after different HD dwell times. HD dwell times were set at 7, 15, and 30 s. The subject was rotated about the interaural axis (pitch) and about the naso-occipital axis (roll). Both the HD dwell times and axes of rotation were randomized within and across subjects. BP and heart rate were recorded during the HU-HD-HU maneuver. RESULTS: Analysis of variance, repeated measure design revealed that the rate and magnitude of BP decrease induced by the HD to HU maneuver is significantly higher (p < 0.01) in roll than in pitch during all HD dwell times. The decrease of BP at 7s is significantly (p < 0.01) higher than at 15s and 30s. Heart rate increases significantly higher (p < 0.01) in pitch than in roll at 7s-dwell time. CONCLUSION: Our results suggest that the compensatory mechanism to orthostatic stress is more efficient in response to pitch than roll rotation. This is reflected from the findings that the mean magnitude of OH (orthostatic hypotension) and the rate of BP decrease induced by the HD-HU maneuver is significantly greater in roll rotation than pitch rotation. The mean HR increase post HD-HU rotation is significantly higher in the pitch than the roll rotation. The significant rate of BP decrease during HD-HU roll rotation could have important implications for maintaining G-tolerance and spatial orientation during subsequent exposure to hypergravity.     

The effects of protocol and test situation on maximal vs. submaximal cervical motion: medicolegal implications

The objectives of this study were to examine the influence of the measurement protocol on the range and consistency of cervical motion (CM) in maximal vs. feigned limitation of CM, to explore some cognitive aspects of the feigning performance and to assess the effect of imagined pain vs. financial gain as a stimulus for the submaximal performance. The directions of flexion, extension, right and left rotation and right and left lateral flexion were measured in 26 normal subjects. Four protocols were compared: performance of CM with eyes open vs. eyes closed and testing at either a repetitive (within direction) or random (among directions) order. In each direction three measurements were recorded. Subjects were initially asked to move the head maximally, they were then presented with a vignette describing a fictitious accident involving the neck and were told to feign CM limitation in order to achieve unlawful compensation. In the third part, subjects were instructed to limit CM due to an imagined severe pain applying the repetitive order-eyes open paradigm only. Maximal CM paradigms were associated with significantly larger range (p=0.0000) and higher consistency (p=0.0000) compared the feigning paradigms. The eyes open-repetitive order protocol best separated between maximal and feigned performance. It was also indicated that the majority of subjects used the sensation of tension in the neck region as a cue for feigning while attempting to be as consistent as possible. Compared to feigning motivated by financial gain, limitation due to imagined pain resulted in significantly greater CM reductions and lesser consistency. The findings suggest that while feigning of motion impairment is probably based on somato-sensory input, the preferred CM testing protocol should consist of within direction repetitive movements with eyes open.     

Separation of the effects of raised skin and core temperature on performance of a pursuit rotor task.

Performance of a pursuit rotor task was studied during induced cycles of core temperature between limits of 37.9 degrees C and 38.5 degrees C. At each level of core temperature tested (37.9 degrees C, 38.5 degrees C, and 38.5 degrees C) performance was significantly worse during heating, when skin temperatures were high, than during cooling. The observed decrements were 13.6% at 37.9 degrees C, 16.0% at 38.2 degrees C and 18.1% at 38.5 degrees C. While it may be true that the performance changes were caused by changes in the level of skin temperature, the direction and rate of change of both core and skin temperatures may be important determinants of performance. The results are discussed in relation to current arousal theory.     

Suppression of effects of gradient imperfections on imaging with alternate ascending/descending directional navigation

Alternate ascending/descending directional navigation (ALADDIN) is a new imaging technique that provides interslice perfusion‐weighted and magnetization transfer (MT) asymmetry images. In this article, we investigated the effects of gradient imperfections on ALADDIN MT asymmetry (MTA) signals. Subtraction artifacts increasing with readout offsets were detectable in ALADDIN MTA images from an agarose phantom but not from a water phantom. Slice‐select offsets had no significant effect on the artifacts in MTA. The artifacts were suppressed by averaging signals over the readout gradient polarities independent of scan parameters. All these results suggested that the subtraction artifacts were induced by readout eddy currents. With suppression of the artifacts, ALADDIN signals in human brain and skeletal muscle varied less with scan conditions. Percent signal changes of MTA in human skeletal muscle (0.51 ± 0.11%, N = 3) were about 30% of those in white matter. The new averaging scheme will allow for more accurate MTA imaging with ALADDIN, especially at off‐center positions. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.     

The effects of core proprioception on knee injury: a prospective biomechanical-epidemiological study

BACKGROUND: In sports involving pivoting and landing, female athletes suffer knee injury at a greater rate than male athletes. HYPOTHESES: Proprioceptive deficits in control of the body's core may affect dynamic stability of the knee. Female, but not male, athletes who suffered a knee injury during a 3-year follow-up period would demonstrate decreased core proprioception at baseline testing as compared with uninjured athletes. STUDY DESIGN: Cohort study (prognosis); Level of evidence, 2. METHODS: Study subjects were 277 collegiate athletes (140 female, 137 male) who were prospectively tested for core proprioception by active and passive proprioceptive repositioning. Athletes were monitored for injury for 3 years. An ANOVA and multivariate logistic regression were used to test whether core proprioception was related to knee injuries in athletes. RESULTS: Twenty-five athletes sustained knee injuries (11 women, 14 men). Deficits in active proprioceptive repositioning were observed in women with knee injuries (2.2 degrees ) and ligament/meniscal injuries (2.4 degrees ) compared with uninjured women (1.5 degrees , P or= .05). Uninjured women demonstrated significantly less average error in active proprioceptive repositioning than uninjured men (1.5 degrees vs 1.7 degrees , P 相似文献