A comparison of physiological responses to two types of particle barrier, vapor permeable clothing ensembles.

Chemical protective clothing (PC) use while working results in elevated rectal temperatures (Tre) that limit work time. Particle barrier, vapor permeable (PBVP) PCs allow workers to cool themselves by evaporating some sweat. The purpose of this study was to compare the effects on worker productivity of two types of PBVP suits, a Kleenguard (PPPC) (Kimberly Clark), and a Tyvek (PEPC) (DuPont) suit. Fifteen males in a repeated measures design performed four work tests consisting of a walk/arm curl combination at a time-weighted work rate of 1.0 L/min (300 kcal/hr), two in a wet bulb globe temperature (WBGT) of 26 degrees C and two in a WBGT of 18 degrees C, with subjects wearing each suit once in each environment. No significant difference (p > 0.05) was observed between the suits at 18 degrees C WBGT, but a significant difference was found (p < 0.05) between the suits, with the PPPC having a lower Tre in the WBGT = 26 degrees C at the 80th, 100th, and 120th min. A significant difference (p < .05) was also seen in the 26 degrees C WBGT with the PPPC resulting in a lower heart rate (HR) at the 40th, 60th, 80th, 100th, and 120th min and rate of perceived exertion (RPE) at the 75th, 90th, and 120th min. Additionally, a significant difference (p < .05) was seen between PEPC and PPPC for Tre, delta Tre, mean skin temp (mTsk), delta mTsk, and HR, each regressed against time in the 26 degrees C WBGT. Twelve of the 15 subjects also reported feeling cooler in the PPPC versus the PEPC in either WBGT environment.

A modified step test based on a function of subjects' stature.

A number of submaximal step tests have been developed to predict maximal aerobic capacity. Because step height may influence biomechanical efficiency and heart rate, step tests based on subjects' stature may more accurately predict maximal aerobic capacity. Eighteen women performed the Queens College step test and a modified Queens College step test. The modified step test was performed with the height of the bench set even with the height of the foot at a knee angle of 90 degrees. Analysis of the data indicated a lower recovery heart rate following this test (p < .05). Further, correlations between maximal aerobic capacity and recovery heart rate for both tests were moderate (r = -.80 and -.75, respectively). Our results suggest that step tests based on subjects' stature do not more accurately predict aerobic capacity than those using a standardized bench height.

Comparison of a military chemical suit and an industrial usage vapor barrier suit across two thermal environments.

This study compared physiological responses to wearing military chemical protective clothing (MPC) and industrial vapor barrier protective clothing (IPC) across two thermal environments to determine the application of the MPC research toward IPC use. Ten males wore each ensemble in a wet bulb globe temperature (WBGT) = 18 and 26 degrees C environment for four test sessions. Each test session consisted of two 30-min work bouts separated by a 30-min recovery period. Each work bout consisted of walking on a treadmill with an oxygen demand of 1.4 L/min for 15 min followed by 7 min of arm curling of 0.9 L/min, followed by 8 min of walking. Work was stopped when either the 30-min time limit was met or a core temperature (Tre) of 38 degrees C was achieved. Variables included sweat rate, heart rate at the end of each work bout, change in (delta) Tre and mean skin temperature (mTsk), and heat stored (Whr). A repeated measures analysis of variance showed no significant difference (p > 0.05) between heart rates at the end of the work bouts between the MPC and IPC. A significant difference was found (p < 0.05) between sweat rates (MPC = 11.5, IPC = 7.4 g/min), delta mTsk, and heat stored, all independent of WBGT. A significant difference (p < 0.05) was also found between delta Tre (MPC = 0.52, IPC = 0.90) in the WBGT = 26 degrees C environment. Results indicate that these two suits elicit similar physiological responses in a cool environment (WBGT = 1 degrees C) but different Tre responses in a hot (WBGT = 26 degrees C) environment. Results show that MPC research can be applied toward IPC settings; however, comparisons between the two should be made with caution, particularly in regard to hot environments.

Relating heat strain in the chemical defense ensemble to the ambient environment.

Management of military personnel in chemical protective clothing (CPC) is difficult. The purpose of this study was to test a 10 degrees C wet bulb globe temperature (WBGT) adjustment for CPC. Five male subjects walked for 1 hour at 400 kcal/hour twice in a U.S. military CPC at a WBGT = 20 degrees C, and once without protective clothing (NoPC) in a WBGT = 30 degrees C followed by a 45 minute seated recovery. No significant differences (p > 0.1) were observed between CPC trials, nor between the mean of the CPC trials and NoPC for heart rate, sweat rate, or change in rectal or mean skin temperatures during the work or recovery phases. Correlations between mean CPC and NoPC were all greater than 0.68. These results suggest minimal differences in responses between CPC and NoPC when the WBGT difference equaled 10 degrees C.

The acute effect of moderate alcohol consumption on cardiovascular responses in women.

OBJECTIVE: The purpose of this study was to assess the effects of moderate dose alcohol consumption on human metabolic and cardiovascular responses during submaximal exercise. METHOD: Ten female subjects participated in two experimental conditions: (1) an alcohol session where the subjects ingested 0.625 g per kg body weight of 80-proof ethyl alcohol (0.25 g/kg of 100% ethanol), and (2) a placebo session. In each session, the subjects exercised on a stationary bicycle at 70% predicted maximum heart rate (HR) for 30 minutes. HR, blood pressure (BP) and oxygen consumption (VO2) were measured at the baseline and at 10, 20 and 30 minute intervals during exercise. Blood lactic acid (BLA) was measured at the baseline and at the end of exercise. RESULTS: Repeated analysis of variance and subsequent comparisons showed that the alcohol session had significantly higher scores for HR, BP, VO2 and BLA than the placebo session (p < .05). CONCLUSIONS: These results suggest that during submaximal work, acute moderate alcohol consumption may interfere with aerobic energy metabolism, thus increasing the demand placed upon the cardiovascular system.