Estrogen and substrate metabolism: a review of contradictory research.

The increasing number of females participating in physical activity has heightened our awareness of changes in the menstrual cycle which often accompany physical activity. As such, there has been a considerable amount of research investigating the relationships between menstrual cycle changes and bone mineral density, performance, ventilation and substrate metabolism. A number of researchers have concluded that there may be enhanced fat metabolism in eumenorrhoeic versus amenorrhoeic females, or in the follicular phase versus the luteal phase of the menstrual cycle, due to the theoretical estrogen level in eumenorrhoeic versus amenorrhoeic females or the luteal phase versus the follicular phase. However, a definite relationship between resting estrogen level and substrate metabolism has not been clearly established. In addition, the mechanisms which may be responsible for the effect of estrogen on substrate metabolism have not been addressed. It appears that the effects of estrogen on metabolism may be via the effect of estrogen on glucogenic hormones or lipolytic enzymes. Therefore, the primary purpose of this review is to explore the effects of estrogen on substrate metabolism. Menstrual cycle physiology and possible mechanisms for the effects of estrogen on metabolism, as well as previous research on estrogen and metabolism in rats and humans, will be discussed.

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.

Disordered eating in female collegiate athletes and collegiate females in an advanced program of study: a preliminary investigation.

The purpose of this study was to use the Eating Disorders Inventory-2 (EDI-2) to compare disordered eating pathology between female intercollegiate athletes and a control group of nonathletic subjects enrolled in an advanced program of study. Analysis of variance (ANOVA) procedures revealed no significant difference (NSD) (p > .05) between any of the athletic groups or the control group on any EDI-2 subscale, and there was no significant difference between "lean" sports, other sports, and the control group. There was also NSD on EDI-2 subscale scores on the basis of age. African Americans had significantly lower scores on the Body Dissatisfaction and Impulse Regulation subscales than white Americans. Chi-square analysis revealed NSD between any groups in percentage of respondents scoring above anorexic norms. The results did not indicate a greater amount of disordered eating in female athletes compared to nonathlete controls.