Sweat gland density and response during high-intensity exercise in athletes with spinal cord injuries.

Sweat production is crucial for thermoregulation. However, sweating can be problematic for individuals with spinal cord injuries (SCI), as they display a blunting of sudomotor and vasomotor responses below the level of the injury. Sweat gland density and eccrine gland metabolism in SCI are not well understood. Consequently, this study examined sweat lactate (S-LA) (reflective of sweat gland metabolism), active sweat gland density (SGD), and sweat output per gland (S/G) in 7 SCI athletes and 8 able-bodied (AB) controls matched for arm ergometry VO2peak. A sweat collection device was positioned on the upper scapular and medial calf of each subject just prior to the beginning of the trial, with iodine sweat gland density patches positioned on the upper scapular and medial calf. Participants were tested on a ramp protocol (7 min per stage, 20 W increase per stage) in a common exercise environment (21±1°C, 45-65% relative humidity). An independent t-test revealed lower (p<0.05) SGD (upper scapular) for SCI (22.3 ±14.8 glands · cm(-2)) vs. AB. (41.0 ± 8.1 glands · cm(-2)). However, there was no significant difference for S/G between groups. S-LA was significantly greater (p<0.05) during the second exercise stage for SCI (11.5±10.9 mmol · l(-1)) vs. AB (26.8±11.07 mmol · l(-1)). These findings suggest that SCI athletes had less active sweat glands compared to the AB group, but the sweat response was similar (SLA, S/G) between AB and SCI athletes. The results suggest similar interglandular metabolic activity irrespective of overall sweat rate.

Hydration profile and influence of beverage contents on fluid intake by women during outdoor recreational walking.

This study examined hydration status, sweat losses, and the effects of flavoring and electrolytes on fluid intake for women (n = 27, age = 24 ± 4 years) walking at a self-selected pace for ~1 h on a 1 km outdoor path during summer mornings or evenings. Over five consecutive days, participants consumed ad libitum one non-caloric beverage containing: (1) water (W), (2) acidified water (AW), (3) acidified water with electrolytes (AWE), (4) acidified water with flavor (AWF), and (5) acidified water with flavor and electrolytes (AWFE) in a counter-balanced order during walks and a 1-h recovery period. Walk Wet bulb globe temperature (26.2 ± 1.8 °C) and pace (6.0 ± 0.5 km/h) did not differ among beverages (P > 0.05). Thirty-four percent of pre-walk urine specific gravity samples exceeded 1.020. Flavoring (AWF 700 ± 393 mL; AWFE 719 ± 405 mL) did not result in greater consumption (P > 0.05) over W (560 ± 315 mL), with all three beverages exceeding grand mean sweat losses (528 ± 208 mL). Addition of electrolytes did not influence (P > 0.05) the intake between AW versus AWE or AWF versus AWFE. The results of this study indicate that the majority of women will consume fluids in excess of their sweat losses within 1 h post-walk. Over half of consumption took place during walks, highlighting the importance of fluid availability during exercise. Great among-subjects variability in sweat losses and fluid intake support the need for promoting individualized hydration strategies based on the changes in body mass for athletic populations.

Evaluation of artificial sweat in athletes with spinal cord injuries.

Athletes with spinal cord injury often experience high heat storage due to reduced sweating capacity below the spinal injury. Spray bottle (SB) may be used to apply mist for evaporative cooling during breaks in competitions. This study examined the efficacy of SB during rest breaks. Seven participants, four female and three males, (mean +/- SD age 24 +/- 4.1 year, weight 56.2 +/- 7.0 kg, upper-body VO(2) peak 2.4 +/- 0.6 l/min) volunteered for the study. Participants were paraplegic athletes (T3-T12/L1) with both complete and incomplete lesions. Participants arm-cranked using a ramp protocol in an environment of 21 +/- 1.5 degrees C and 55 +/- 3% rh once using a SB during 1-min rest between 7-min stages of increasing intensity and once without the SB (CON). Mean total work was similar (p = 0.86) for the SB and CON (2495.7 +/- 914.6 vs. 2407.1 +/- 982.3 kJ, respectively). Likewise, the mean work times were similar between trials (27 +/- 6 and 26 +/- 7 min for SB and CON, respectively). Furthermore, there were no significant differences detected between trials for skin temperature, rectal temperature, esophageal temperature (p > 0.05). There were no statistically significant differences detected between trials for RPE (p > 0.05). In conclusion, the application of artificial sweat via SB was ineffective in attenuating the onset of uncompensable heat strain during high-intensity arm exercise in a comfortable environment.

Effect of gender on fatigue and recovery following maximal intensity repeated sprint performance.

AIM: This study investigated the effects of gender on repeated, maximal-intensity intermittent sprint exercise following variable day-to-day recovery periods. METHODS: Sixteen volunteers (8 men, 8 women) performed four trials of high-intensity intermittent sprint exercise consisting of three bouts of eight 30 m sprints (total of 24 sprints). Following completion of the baseline trial, in repeated-measures design, participants were assigned, in counter-balanced order, variable recovery periods of 24, 48, and 72 h whereupon they repeated an identical exercise trial. RESULTS: Results from a series of 4 (trial) x 3 (bout) repeated measures ANOVAs revealed men produced significantly (P < 0.01) faster times throughout all bouts and trials of repeated sprint exercise. Additionally, women exhibited significantly lower (P < 0.05) blood lactate concentration and significantly lower (P < 0.05) decrement in performance, indicating increased resistance to fatigue during repeated exercise sessions. There were no significant differences (P > 0.05) between genders for heart rate or rating of perceived exertion during or following trials. There were no significant differences for overall sprint performance within either gender among trials. CONCLUSION: These results indicate men, while able to produce higher absolute power outputs (i.e., lower sprint time), demonstrate higher decrement scores within a trial compared to women, thus suggesting women may recover faster and fatigue less. Also, gender differences affecting recovery within in a trial were observed to be diminished between trials (i.e., day-to-day recovery) of maximal intermittent sprint work evidenced by the observed stability of performance between trials following various recovery durations.

Physiological and comfort effects of a commercial "cooling cap" worn under protective helmets.

Ballistic protective helmets can impair heat dissipation. A cooling device in the helmet (cooling pad, CP) could help prevent heat problems in military personnel and potentially enhance comfort. This study examined the effects of CP on rectal and skin temperatures, heart rate, percent change in plasma volume, urine specific gravity, rating of perceived exertion, and other subjective measures while performing light work in a hot environment. It was hypothesized that the CP would act as an insulator to the head, which would not positively affect any physiological variable but could positively affect wearer subjective comfort or temperature. Participants performed a work protocol for approximately 2 hr. A ballistic vest, slacks, short-sleeved button-up shirt, and a ballistic helmet (one trial with CP and one trial without) were worn. Repeated measures analysis of variance (ANOVA) showed no differences (p > 0.05) between wearing and not wearing the CP for any physiological parameter. However, participants perceived the CP as cooler (p = 0.002). Other trends in perceptual data such as thermal strain and helmet comfort indicated the CP felt cooler. However, based on forehead temperature and participant comments, the CP lost its cooling ability relatively quickly (within approximately 30 min).

Bacteroides ureolyticus (NTU) medium for the selective recovery of Bacteroides gracilis.

Bacteroides gracilis is a gram-negative anaerobic bacillus which requires formate and fumarate for growth; it has been implicated in periodontal disease and serious infections of the head and neck. In this study, Bacteroides ureolyticus (NTU) medium was tested for its ability to allow the growth of B. gracilis and other formate-fumarate requiring gram-negative anaerobes and to enable the recovery of these organisms from clinical specimens. All reference strains grew on NTU medium with the exception of Wolinella recta and formate-fumarate requiring organisms were isolated from 18 of 20 samples of subgingival dental plaque from patients with chronic periodontitis. B. gracilis was the commonest species isolated (14 of the 29 isolates); B. ureolyticus was not found.

An unclassified Eubacterium taxon in acute dento-alveolar abscess.

The microflora of pus samples aspirated from 50 acute dento-alveolar abscesses was examined. A total of 143 bacterial strains was isolated, consisting predominantly of Prevotella spp., alpha-haemolytic Streptococcus spp., Peptostreptococcus spp. and Eubacterium spp. An unclassified asaccharolytic Eubacterium taxon was encountered in 17 (34%) of the abscesses. This taxon was found to have a positive association with Fusobacterium spp. and a negative association with alpha-haemolytic Streptococcus spp.

Direct detection of Prevotella intermedia and P. nigrescens in suppurative oral infection by amplification of 16S rRNA gene.

A specific 16S rDNA PCR and subsequent hybridisation reaction was designed to discriminate between strains of Prevotella intermedia (n = 15) and P. nigrescens (n = 15). This technique was then used to detect the presence of these two bacterial species in acute suppurative oral infection. A total of 36 pus samples aspirated from 26 peri-apical abscesses, three root canals, three periodontal abscesses, two cases of refractory periodontitis, one cyst and one haematoma was examined. A portion of the pus sample was processed by PCR and the remainder of the specimen was subjected to routine culture. The PCR-based technique gave an identical pattern of detection of P. intermedia or P. nigrescens to that obtained by culture for 30 of the 36 specimens. Either P. intermedia or P. nigrescens was present in 14 samples and neither species was detected in 16 samples. In the remaining six samples the PCR method indicated the presence of one (n = 3) or both (n = 3) of the Prevotella species but neither or only one species was isolated by culture. It is concluded that the presence of P. intermedia and P. nigrescens in pus can be detected rapidly and specifically by direct PCR amplification of 16S rDNA. P. nigrescens was detected more frequently than P. intermedia in suppurative peri-apical infection both by culture and PCR.

Rebounding exercise. Are the training effects sufficient for cardiorespiratory fitness?

Additional research is needed in order to document the effects of rebound training. Efforts should focus on the factors that are necessary for standardising the intensity of exercise such as step height and frequency. In addition, attention may be given to alternative methods of increasing exercise intensity while rebounding. One such method may be to increase the total muscle mass involved by adding the pumping of handheld weights to the rebounding exercise. Data from our laboratory (Bishop et al. 1986) has demonstrated that the addition of pumping 1-, 2- and 3-pound (0.45, 0.91 and 1.36 kg) handheld weights, at 2- and 3-foot (30 and 45 cm) heights, to rebounding exercise will increase the oxygen requirement from 26 to 60%. Assessing these effects in a training study would necessitate testing for adaptation in the upper extremities. This type of training highlights the need for activity specific tests. More specifically, additional research is needed to: 1. Determine the energy cost of activities other than jogging/bouncing that may be possible on a mini-trampoline, such as those described by White (1984). 2. Determine the training response of subjects in studies in which the controllable factors affecting intensity are standardised. 3. Examine the effects of longer periods of rebound training. Because rebounding exercise is novel to most subjects, it would appear that the length of training should allow subjects to maintain a reasonable frequency, intensity, and duration of exercise above that needed for familiarization with the new activity. 4. Determine if the prolonged use of other training aids (limb weights) with rebounding is feasible and effective in long term training.(ABSTRACT TRUNCATED AT 250 WORDS)

Validation of body composition models for high school wrestlers.

This study investigates the utility of two equations for predicting minimum wrestling weight and three equations for predicting body density for the population of high school wrestlers. A sample of 54 wrestlers was assessed for body density by underwater weighing, residual volume by helium dilution, and selected anthropometric measures. The differences between observed and predicted responses were analyzed for the five models. Four statistical tests were used to validate the equations, including tests for the mean of differences, proportion of positive differences, equality of standard errors from regression, and equivalence of regression coefficients between original and second sample data. The Michael and Katch equation and two Forsyth and Sinning equations (FS1 and FS21) for body density did not predict as well as expected. The Michael and Katch equation tends to overpredict body density while FS1 underpredicts. The FS2 equation, consisting of a constant adjustment to FS1, predicts well near the mean but not at the ends of the sample range. The two Tcheng and Tipton equations produce estimates which slightly but consistently overpredict minimum wrestling weight, the long form equation by 2.5 pounds and the short form by 3.8 pounds. As a result the proportion of positive differences is less than would be expected. But based on the tests for the standard errors and regression coefficients, the evidence does not uniformly reject these two equations.

Rapid cooling techniques in joggers experiencing heat strain.

This study examined subjects that exercised on three occasions in a heated environment (WBGT = 39 degrees C] until they experienced heat strain. Since morbidity and mortality due to heat injury increase with the duration of elevated core temperature, it is important that techniques to lower core temperature be evaluated. Following three exercise sessions, subjects underwent each of three core cooling treatments in random order: 1) Torso immersion in cool water, 2) Hands and feet immersion in cool water, and 3) Sit-in-shade with a 1.5mph breeze provided. Subjects (n=5) consistently reached peak rectal temperatures of 38.8 (+/-0.1) degrees C following each exercise bout in the heated environment. Torso immersion produced a significantly (p<0.05) greater rate of decline in rectal temperature (0.25+/-0.10 degrees C/min) than the hands and feet immersion technique (0.16+/-0.05 degrees C/min) and the sit in the shade technique (0.11+/-0.04 degrees C/min). After only 10 minutes of cooling, the differences among cooling techniques were evident. Similar trends were observed for mean heart rate readings, albeit not significant (p>0.05). It was concluded that rectal temperatures can be reduced rapidly through the use of a cool water torso-immersion technique.

Strength, muscle symmetry, and flexibility in young female idiopathic scoliotics.

Application of previous findings regarding muscle strength and function in scoliotics suggests that curvature might result from unbalanced pull of spinal muscles oriented transversely. This study investigated the role of muscle strength and strength symmetry in 48 young female scoliotics and 48 age-matched controls. The subjects were divided into three age levels: 11 and 12, 13, and 14 and 15 years of age. Scoliotics were weaker than the nonscoliotics only for shoulder strength in the two older age levels. For all subjects combined, as well as each group and age level, the dominant versus nondominant strength differences were significantly greater than zero; however, the magnitudes of the differences were not different between any of the groups. Nonscoliotics displayed significantly greater trunk flexibility than scoliotics. J Orthop Sports Phys Ther 1991;14(4):144-148.

Limitations to the study of man in space in the U.S. space program.

Research on humans conducted during spaceflight is fraught both with great opportunities and great obstacles. The purpose of this paper is to review some of the limitations to research in space in the United States with hope that an informed scientific community may lead to more rapid and efficient solution of these problems. Limitations arise because opportunities to study the same astronauts in well-controlled situations on repeated spaceflights are practically non-existent. Human research opportunities are further limited by the necessity of avoiding simultaneous mutually-interfering experiments. Environmental factors, including diet and other physiological perturbations concomitant with spaceflight, also complicate research design and interpretation. Technical limitations to research methods and opportunities further restrict the development of the knowledge base. Finally, Earth analogues of space travel all suffer from inadequacies. Though all of these obstacles will eventually be overcome, creativity, diligence, and persistence are required to further our knowledge of humans in space.

Limitations to heavy work at 21 degrees C of personnel wearing the U.S. military chemical defense ensemble.

The purpose of this study was to determine the limitations to work of personnel performing heavy work at 21 degrees C (70 degrees F) while wearing the chemical defense ensemble (CDE) worn by all branches of the U.S. military. Male volunteers (N = 17) wearing the CDE performed an arm and leg work task yielding a time-weighted energy consumption rate of 450 W, under environmental conditions of 21 degrees C and 65-70% relative humidity. Each work bout was continued until one of the following limits occurred: volitional fatigue, rectal temperature (Tre) of 39 degrees C, or calculated heat storage (S) of 140 Wh. Subjects then rested until heat stored due to this work was lost, then repeated the work-rest cycles until refusal, or inability to restart work after a rest cycle. Over a total of 36 work cycles, subjects terminated work cycles for S on only two occasions, with the remainder almost equally divided between cumulative fatigue and high Tre. Intersubject variability was high for work and rest times, S, heat loss, and sweat production. U.S. Air Force Regulation (AFR) 355-8, which provides guidance for heat stress in the form of work/rest cycles, underestimated work tolerance under these study conditions.

Simulated shuttle egress: comparison of two Space Shuttle protective garments.

BACKGROUND: In a previous study from our laboratory, we observed carbon dioxide (CO2) accumulation in the helmet of the NASA Launch and Entry Suit (LES) during a simulated emergency egress from the Space Shuttle. Of 12 subjects, 8 were unable to complete the egress simulation with a G-suit inflation pressure of 1.5 psi. The purpose of this report was to compare CO2 accumulation and egress walking time in the new Advanced Crew Escape Suit (ACES) with that in the LES. METHODS: Four male subjects who previously were unable to complete the egress in the LES performed a simulated egress while wearing the ACES with the G-suit inflated to 1.5 psi. The egress simulation consisted of 6 min of seated rest, 2 min of standing, and 5 min of walking on a treadmill at 1.56 m x s(-1) (3.5 mph) and 0% grade. The helmet visor was closed with the subjects receiving 100% oxygen throughout the simulation. Inspired CO2 and walking time were measured. RESULTS: The rate of CO2 accumulation was significantly less (ACES: 0.53 +/- 0.03, LES: 1.07 +/- 0.15 %CO2 x min(-1); p = 0.05) and walk time was greater in the ACES (ACES: 5.0 +/- 0.0, LES: 2.7 +/- 0.2 min; p = 0.002). CONCLUSIONS: Changes in the design of the ACES from the LES resulted in a decreased rate of CO2 accumulation and an improved egress walking time compared with the LES.

Simulated shuttle egress: role of helmet visor position during approach and landing.

BACKGROUND: We previously reported that carbon dioxide (CO2) rapidly accumulates in the helmet of the NASA Launch and Entry Suit (LES) during a simulated egress from the Space Shuttle following 6 min of visor-closed seated rest to simulate approach and landing. The purpose of this study was to determine if CO2 accumulation and walking time in the LES would be improved by helmet visor-open rather than visor-closed seated rest prior to the performance of the simulated egress. METHODS: Wearing the LES, 12 male subjects performed 4 laboratory egress simulations consisting of 6-min seated rest, 2-min stand, and 5-min walk at 1.56 m x s(-1) (3.5 mph). During seated rest, subjects sat either with the visor open, breathing room air until the visor was closed on standing, or with the visor closed for the duration of the simulation. For all visor-closed operations 100%, O2 was supplied. The G-suit was either deflated (0.0 psi) or inflated to 1.5 psi. Inspired CO2 and walking time were measured. Data were analyzed at the end of seated rest, standing, and after 5 min of walking at 0.0 psi or after 2 min of walking at 1.5 psi (>90% of data available). RESULTS: Walk time was not different following visor-open (0.0 psi: 5.0 +/- 0.0; 1.5 psi: 3.4 +/- 0.3 min) or visor-closed (0.0 psi: 4.8 +/- 0.2; 1.5 psi: 3.5 +/- 0.4 min) seated rest at either G-suit pressure. Inspired CO2 levels were not different between the two conditions during walking at 5 min at 0.0 psi (p = 0.50; Open: 4.39 +/- 0.14; Closed: 4.48 +/- 0.18%) or at 2 min at 1.5 psi (p = 0.53; Open: 3.59 +/- 0.12; Closed: 3.65 + 0.21%). CONCLUSIONS: Visor position during seated rest immediately preceding the egress walk had no effect on inspired CO2 or walking time.

Carbon dioxide accumulation, walking performance, and metabolic cost in the NASA launch and entry suit.

BACKGROUND: In the event of an emergency on landing, Space Shuttle crewmembers while wearing the Launch and Entry Suit (LES) must stand, move to the hatch, exit the spacecraft with the helmet visor closed breathing 100% O2, and walk or run unassisted to a distance of 380 m upwind from the vehicle. The purpose of this study was to characterize the inspired CO2 and metabolic requirements during a simulated unaided egress from the Space Shuttle in healthy subjects wearing the LES. METHODS: As a simulation of a Shuttle landing with an unaided egress, 12 male subjects completed a 6-min seated pre-breathe with 100% O2 followed by a 2-min stand and 5-min walking at 1.56 m x s(-1) (5.6 km x h(-1), 3.5 mph) with the helmet visor closed. During walks with four different G-suit pressures (0.0, 0.5, 1.0, 1.5 psi; 3.4, 6.9, 10.3 kPa), inspired CO2 and walking time were measured. After a 10-min seated recovery, subjects repeated the 5-min walk with the same G-suit pressure and the helmet visor open for the measurement of metabolic rate (VO2). RESULTS: When G-suit inflation levels were 1.0 or 1.5 psi, only one-third of our subjects were able to complete the 5-min visor-closed walk after a 6-min pre-breathe. Inspired CO2 levels measured at the mouth were routinely greater than 4% (30 mmHg) during walking. The metabolic cost at the 1.5 psi G-suit inflation was over 135% of the metabolic cost at 0.0 psi inflation. CONCLUSION: During unaided egress, G-suit inflation pressures of 1.0 and 1.5 psi resulted in elevated CO2 in the LES helmet and increased metabolic cost of walking, both of which may impact unaided egress performance. Neither the LES, the LES helmet, nor the G-suit were designed for ambulation. Data from this investigation suggests that adapting flight equipment for uses other than those for which it was originally designed can result in unforeseen problems.

Physiological determinants of performance on an indoor military obstacle course test.

Obstacle courses (OCs), physical challenge courses, and confidence courses are valuable in training and assessing military troops. However, OCs are not well characterized with regard to physical demands and requisite abilities. The purpose of this study was to evaluate the physical capabilities associated with success on an OC. Male subjects (N = 47) were assessed on an OC, skinfolds, upper and lower body aerobic and anaerobic power, muscular strength, and endurance. Faster performers were lighter (p < 0.003), leaner, and, relative to body weight, averaged greater arm anaerobic peak and mean power, leg aerobic power, one-repetition maximum leg press, and one-repetition maximum latissimus dorsi pull-down, than slower performers. There were significant correlations between OC time and weight (0.59), percent fat (0.54), anaerobic leg mean power (-0.43), arm anaerobic peak (-0.48) and mean power (-0.48), and arm (-0.51) and leg aerobic power (-0.53), all expressed relative to body weight. A three-variable regression model accounted for 35% of the variation in OC time. Good performers on this OC displayed many diverse physical capabilities.

Physiologic Responses to Treadmill and Water Running.

In brief: The physiologic responses to running on a treadmill and to running in water while wearing a buoyant vest were compared in seven uninjured runners. Ventilation, oxygen uptake, and respiratory quotient were significantly higher during treadmill running, whereas heart rate and perceived exertion were not significantly different for the two forms of exercise. Water running elicited a 36% lower metabolic cost than treadmill running despite the athletes' efforts to maintain a similar level of exertion. The results suggest that water running may help lessen the rate of deconditioning of injured athletes who must suspend their regular forms of exercise, but they fail to show that the metabolic cost of water running is significantly greater than that of treadmill running.