PURPOSE: Recent exercise guidelines recommend a generalized rating of perceived exertion (RPE) range of 12 to 16 (15-point Borg scale) as the perceptual range associated with a physiological training effect. However, whether an individual who selects an RPE within the generalized range during an graded exercise test or exercise training, is actually within the correlated physiological range (50 to 85% maximum oxygen consumption [VO2max]) has not been studied in large samples of apparently healthy individuals or cardiac patients. The purpose of the present study was to assess the validity of the generalized RPE recommendations in a large heterogeneous group of apparently healthy subjects and cardiac patients. METHODS: Subjects included apparently healthy adults (N = 463) and cardiac patients (N = 217) who presented for a sign-symptom limited maximal graded exercise test (SSLMGXT). Ratings of perceived exertion associated with relative exercise intensities of 60 and 80% of maximal heart rate reserve (MHRR) and peak exercise were selected for analyses. RESULTS: Significant interindividual variability in RPE was observed at both relative exercise intensities (6 to 20 RPE range at 60% MHRR; 8 to 20 RPE range at 80% MHRR) for both populations. Thirty-nine percent of healthy subjects and 32% of cardiac patients reported an RPE outside an 11 to 14 range at 60% of MHRR, whereas 32% of healthy subjects and 52% of cardiac patients reported an RPE outside of a 14 to 17 range at 80% of MHRR. Peak RPE was higher for the apparently healthy subjects compared with the cardiac patients (18.8 +/- 1.2 versus 16.5 +/- 1.8; P < 0.01). CONCLUSIONS: These results challenge the applicability of the generalized RPE recommendations described in recent exercise guidelines under typical clinical exercise testing conditions. The basis for the generalized RPE recommendations warrant further investigation. Those who desire to use RPE as a marker of relative exercise intensity during SSLMGXT should take into consideration the large interindividual variability in these measures.

Adult↗

PubMedDate not supplied

General toxicity and reproductive screen of liquid propellant XM46 administered in the drinking water of Sprague-Dawley rats.

Liquid propellant XM46 is being considered as a replacement for solid propellants, both as part of a regenerative injection gun system and as a working fluid in an electrothermal gun system. The XM46 formulation contains hydroxylammonium nitrate, triethanolammonium nitrate, and water. Male and female Sprague-Dawley rats received XM46 in drinking water containing 2.0, 1.0, 0.2, or 0.0 g XM46/liter throughout a 90-day study. Mating occurred following 14 days of treatment. One-half the male rats per group were necropsied after 28 days of treatment; the remaining males and all dams were necropsied following 90 days of treatment. No mortality occurred in any of the parental animals during the study. The study did not demonstrate any adverse effects on reproduction or litter parameters. Hemolytic anemia and methemoglobinemia were common in both sexes of rats. Splenomegaly was found in both sexes; in male rats as early as 28 days. Exposures via drinking water containing XM46 for 90 days did not result in any decrease in reproductive performance in male or female rats, but it did result in clinical signs of hemolytic anemia at doses as low as 17 mg/kg/day.

Aerosol Propellants↗

PubMedDate not supplied

Reproductive toxicity screen of 1,3,5-trinitrobenzene administered in the diet of Sprague-Dawley rats.

Several Army installations targeted for restoration have measurable quantities of 1,3,5-trinitrobenzene (TNB) in the soil and groundwater. As part of the process of developing environmental and health effects criteria for restoration, a modified Screening Information Data Set (SIDS) reproductive study was performed. Male and female Sprague-Dawley rats received a diet containing approximately 30, 150, or 300 mg TNB/kg diet. Mating occurred following 14 days of treatment. All dams, one-half the males, and representative pups were maintained for a total of 90 days of treatment. No mortality occurred during the study; however, a decrease in mean body weights was noted in both sexes of high-dose rats. A dose-related effect was noted in measurements of sperm function/activity. Sperm depletion and degeneration of the seminiferous tubules were noted histopathologically. Methemoglobinemia and splenic hemosiderosis were common findings in the high- and mid-dose levels of both sexes at necropsy. No adverse effects were noted in mating or fertility indices. No significant treatment-related differences were found in length of gestation, sex ratio, gestation index, or mean number of pups per litter.

Animals↗

PubMedDate not supplied

Reproductive toxicity screen of ammonium dinitramide administered in the drinking water of Sprague-Dawley rats.

The Department of Defense is currently considering replacing ammonium perchlorate with ammonium dinitramide (ADN), a class 1.1 explosive oxidizer to be used in solid rocket propellant mixtures and explosives. This study was intended to evaluate the potential of ADN to produce alterations in paternal fertility, maternal pregnancy and lactation, and growth and development of offspring. Male and female rats received drinking water containing 0.0, 0.2, 1.0, or 2.0 g ADN/liter throughout the study. Mating occurred following 14 days of treatment. All dams, one-half the males, and representative pups were maintained for a total of 90 days of treatment. No mortality occurred in parental animals during the study. Treatment with ADN resulted in no adverse effects on mating; 92-100% of the animals mated. No treatment-related effects were seen in parental animals clinically or histopathologically. Adverse treatment-related effects were noted in maternal and paternal fertility indices, gestational indices, and live birth indices in both the mid- and high-dose groups. Litter sizes in the mid- and high-dose groups were significantly smaller than those of the low-dose and control groups. Mean pup weights showed no statistically significant differences between ADN-treated pups and controls. Gross and histopathological examination of the animals failed to identify the cause for the decrease in litter production in the mid- and high-dose dams. This study indicates that ADN is a reproductive toxicant. The no-observable-effect level (NOEL) is 29 mg/kg/day, the median dose of the low level female rats.

Animals↗