Christine L. Wells

Effects of physical exercise on pregnancy outcomes: a meta-analytic review.

In this study, using meta-analysis the findings of all individual reports on the effects of exercise training on pregnancy outcomes were pooled to determine the effects of such training on the pregnant woman and her fetus. Meta-analysis is a statistical technique used to summarize the results of experimental studies that address a common problem. Results show that women who exercised during their pregnancies did not differ from sedentary women for any of the outcome variables measured: maternal weight gain (P = 0.07), infant birth weight (P = 0.20), length of gestation (P = 0.67), length of labor (P = 0.14), and APGAR scores (P = 0.59). Many of the exercise programs exceeded, without apparent adverse effects, the recommended limitations set by the American College of Obstetricians and Gynecologists. Overall, an exercise program using any of a variety of exercise modes that is performed for an average of 43 min.d-1, 3 times.wk-1, at a heart rate of up to 144 bpm, does not appear to be associated with adverse effects to the mother or fetus in a healthy normal pregnancy. However, these findings should be cautiously applied owing to the nature of the currently available data base. Recommendations or precautions for programs of greater intensities can not be made at this time.

Effects of low- and moderate-intensity training in spinal cord-injured persons.

This study examined the applicability of exercise prescription guidelines established for the able-bodied to spinal cord-injured (SCI) persons. Two SCI groups performed wheelchair ergometry (WCE) 20 min three times per week for 8 wk. Low-intensity (LI, N = 6) and moderate-intensity (MI, N = 5) groups trained at 50-60% and 70-80% maximal heart rate reserve (HRR), respectively. The subjects completed an incremental discontinuous maximal WCE test to exhaustion pre- and post-training. A submaximal WCE test consisting of 4-min exercise stages at power outputs of 5, 10, and 15 W was also performed pre- and post-training. Blood samples were collected before and after training and analyzed for total cholesterol (TC), triglycerides (TG), high-density lipoprotein-cholesterol (HDL-C), and low-density lipoprotein-cholesterol (LDL-C). The TC/HDL-C ratio was calculated. Both groups exhibited no significant changes (P greater than 0.10) in VO2max, HRmax, POmax, lactate (La)max, and VO2 at 4 mmol [La]. No pre- to post-training differences were recorded in the LI group for submaximal VO2, HR, VE, La, and ratings of perceived exertion (RPE). The MI group had significantly lower (P less than or equal to 0.10) post-training submaximal HR, La, and RPE and no changes in VO2 or VE. Blood lipid levels remained unaltered in the LI group, while the MI group exhibited significant increases in HDL-C and decreases in TG, LDL-C, and the TC/HDL-C ratio. The maximal test data revealed that 8 wk of LI and MI wheelchair ergometry training did not improve VO2max in SCI persons.(ABSTRACT TRUNCATED AT 250 WORDS)

Physical activity in urban white, African-American, and Mexican-American women

PURPOSE AND METHODS The purpose of this study was to analyze physical activity in a large, diverse sample of urban women (N = 521; X = 40.5 +/- 10.5 yr) relative to race/ethnicity, income, age, and education, using a sex-specific physical activity questionnaire. We also examined demographic and behavioral predictors of high levels (> or = 2000 kcal.wk-1) of leisure-time physical activity (LTPA; exercise, sports, recreational activities) in this population. RESULTS The majority of women were sedentary (0-666 kcal.wk-1 in LTPA), and only 8% of African-American women (N = 6), 11% of Mexican-American women (N = 4), and 13% of white women (N = 55) participated in the level of physical activity recommended by the surgeon general (i.e., moderate to vigorous physical activity most days of the week for at least 30 min). Women of color, women over 40, and women without a college education had the lowest levels of participation in LTPA. Logistic regression analysis indicated that education was the only significant predictor of high LTPA in white women (P < 0.01) and marital status was the only significant predictor of high LTPA in minority women (P < 0.001). Age, body mass index (BMI; kg.m-2), income, self-rated health, alcohol intake, and smoking were not significant predictors of high LTPA for any of the women. Because the majority of adult women from this sample do not participate in adequate amounts of physical activity as recommended by the surgeon general, they may be at increased risk for hypokinetic diseases. CONCLUSIONS These results indicate that public health efforts to increase physical activity in women should be focused on women of color, women over 40, and women without a college degree. More attention to predictors of physical activity that are specific to race or ethnicity may improve intervention program design and implementation.

Does physical activity reduce risk of estrogen-dependent cancer in women?

The estrogen-dependent cancers (breast, endometrial, and ovarian) are among the leading causes of morbidity and mortality in American women. Increased incidence of these cancers is predicted in the future, and the need for primary prevention is clear. Sufficient evidence has accumulated to warrant an analysis of the relationship between physical activity and estrogen-dependent cancer. Recent epidemiological studies confirm an inverse relationship between physical activity and estrogen-dependent cancer, with stronger associations appearing for occupational activity than for leisure time or nonoccupational activity. Several hypothesized mechanisms are described for the prevention of estrogen-dependent cancer by physical activity: 1) maintenance of low body fat and moderation of extraglandular estrogen, 2) reduction in number of ovulatory cycles and subsequent diminution of lifetime exposure to endogenous estrogen, 3) enhancement of natural immune function, and 4) the association of other healthy lifestyle habits. Although the mechanisms are not well defined, several lines of evidence support the inclusion of low-to-moderate physical activity as a preventive strategy for estrogen-dependent cancer.

Hematological changes following a marathon race in male and female runners

SummaryThe subjects of this experiment were well-trained men (6) and women (4) participating in a marathon race in Phoenix, Arizona, on a cool, cloudy, windy day. Venous blood was collected one week prior to the run, immediately after, and 4,8, and 24 h after the race. There were no significant changes in hematocrit, hemoglobin, or red blood cell counts following the race. The sample collected immediately after the race showed a pronounced leucocytosis. Differential counts showed that this increase in white blood cell count was limited to polymorphonuclear cells, suggesting that an inflammatory response to stress of the race was involved. Percentage changes in blood volume, red blood cell volume, and plasma volume were calculated from hematocrit and hemoglobin changes. These changes showed that there was reduction of plasma volume of 8% for females and 13% for males immediately after the race, with return to initial values within 8 h. We suggest that the increase in protein following the race was contributed by the flow of lymph from muscle to the vascular compartment.

Effect of age and menopausal status on cardiorespiratory fitness in masters women runners

Forty-nine trained masters women endurance runners (mean = 42 km.wk-1) between the ages of 35 and 70 yr (mean = 46.4 +/- 8.3) were tested on a treadmill to examine cardiorespiratory fitness (VO2max and VO2 submax) in relation to age, training, and menopausal status. Although VO2max was lower with increasing age, no age group differences occurred in VO2 submax at 5.4 km.h-1, 8% treadmill grade. The younger runners (35-39 and 40-44 yr) had significantly higher VO2max than the other 5-yr competitive age groups (45-49, 50-55, 55-70 yr) (P < 0.01). HR max did not differ across age, but HR submax was higher with increasing age. Premenopausal, transitional, and post-menopausal women were not significantly different on any exercise variable when age and/or training differences among the groups were statistically controlled. A decrease in VO2max of 0.58 ml.kg-1 x min-1 x yr-1 was determined (r = -0.62). It was concluded that 1) these highly trained women runners had higher cardiorespiratory fitness than previously reported for women of comparable age, 2) menopausal status did not effect cardiorespiratory fitness when age and training were accounted for, and 3) regular physical training seems to prevent age-related changes in HR max in women, but not age-related changes in maximal oxygen uptake.

Physiological responses to a 20-mile run under three fluid replacement treatments

Ten experienced male marathon runners ran 20 miles (32.18 km) on an outdoor course in a warm climate to measure responses in selected physiological variables as a result of drinking water, an electrolyte-glucose solution (ERG), or a caffeine solution (5 mg X kg-1 body weight) before and during the run. The caffeine solution and water were colored and flavored to resemble the electrolyte-glucose solution so that a double-blind condition could be maintained. Subjects ingested a different fluid in each of the three trials in a counterbalanced design. Parameters studied were: heart rate; rectal temperature; body weight; hemoglobin and hematocrit; serum glucose, sodium, potassium, chloride, and free fatty acids; perceived exertion; respiratory exchange ratio (R); and fractional utilization of VO2max (percentage of VO2max). Both R and percentage of VO2max were higher in subjects who drank the caffeine solution compared to those who drank water. Although post-run free fatty acid mean values were significantly higher than pre-run levels, there were no statistically significant differences among the fluid treatments. Since no other differences were observed, we concluded that, under the outdoor road-running conditions encountered here, these fluid replacement treatments did not differ in their effects on the parameters studied.

Differences in epinephrine and substrate responses between arm and leg exercise

The purpose of this study was to determine epinephrine (EPI) and selected substrate responses during arm crank (AC) and leg cycle (LC) exercise at the same absolute and relative exercise intensity. Nine males performed 30 min AC and LC tests at 70% of ergometer-specific peak oxygen uptake (VO2), and a 30 min LC test eliciting a similar VO2 required during the AC test. Blood samples (30 ml) were collected via an indwelling arm catheter at rest, and at minutes 13 and 28 of exercise for determinations of plasma EPI, serum free fatty acid (FFA), serum glycerol (GLY), blood glucose (GLU), and blood lactate (LA) concentrations. At equivalent VO2, higher (P less than 0.05) EPI, LA, and respiratory exchange ratio (RER) responses were obtained during AC than LC exercise. However, these physiologic responses were similar during AC and LC exercise at the same relative intensity. No significant differences over time were observed for FFA, GLY, and GLU between AC and LC exercise at either the same absolute or relative intensity. The results support previous hypotheses that AC exercise is physiologically more stressful than LC exercise at the same VO2. The data further indicate that adrenomedullary activity (EPI response) and substrate utilization (LA and RER responses) are regulated by relative exercise intensity and not the exercising muscle mass.

Responses of physically active and acclimatized men and women to exercise in a desert environment

In most studies of physiological responses of men and women to exercise in the heat, the subjects are unacclimatized and the females are unaccustomed to strenuous physical activity. In this investigation, 5 men and 6 women known to be physically active in an outdoor hot-dry environment were studied in a temperate environment (Tdb=23C, WBGT=18C) and in an outdoor desert environment (Tdb=39C, WBGT=29C) during rest and exercise at 50% Vo2max. No differences between the groups occurred in Vo2, HR or Tre in either environment. Of greatest interest was that no differences occurred in evaporative weight losses, sweating rates, or % body weight losses in the heat. It was concluded that (1) women accustomed to exercise in a desert climate are able to substantially increase their sudorific response, and (2) that acclimatized male and female subjects of similar aerobic capacity have comparable responses to rest and exercise in a desert environment.

Body composition and sexual maturation in premenarcheal athletes and nonathletes.

The purpose of this study was to compare premenarcheal athletes (A) and nonathletes (NA) in terms of body composition and sexual maturation and to discern the relationship between these variables. Percent body fat (%BF) was determined by the three-component system of Siri utilizing body density from hydrostatic weighing and total body water measured by deuterium oxide dilution. Sexual maturation was self-assessed using the system described by Marshall and Tanner. ANOVAs and polynomial regression analysis revealed that both the A (N = 73) and NA (N = 53) showed similar values and linear increases (P less than 0.001) in height (HT), weight (WT), breast (B) and pubic hair (PH) development from 7 to 15 yr but not in %BF (XA = 15.7 +/- 4.6; XNA = 20.5 +/- 6.4 (P less than 0.001]. The NA exhibited a quadratic curve (P less than 0.01) in %BF over age, while the A showed a negative linear relationship (P less than 0.001) with age. Scheffe post hoc tests revealed significant differences (P less than 0.03, A less than NA) at 11 and 12-15 yr. When %BF was compared to maturation, the A were found to have less fat (P less than 0.01) at stages 1 and 4 of PH and at stages 2, 3, and 4 of B. There were no significant differences between A and NA in the age at which B2, 3, or 4 or PH2, 3, or 4 occurred. Both groups exhibited similar and significant correlations between age, HT, WT, B, and PH development but not %BF.(ABSTRACT TRUNCATED AT 250 WORDS)