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We calculated individual heart rate–oxygen consumption (HR–V̇O₂) regression lines for 49 sixth-grade girls based on a treadmill test. From these data, we determined V̇O₂ at HRs of 140 and 160 b · min⁻¹ and 50%, 60%, and 75% of maximal heart rate reserve (MHRR), and the relationship between V̇O₂ and %fat at given heart rates. Results indicated traditional 140 and 160 b · min⁻¹ HR cutpoints were at the low end of exercise intensity (46 and 63% V̇O_2max) and were negatively correlated with %fat. Heart rates at 50%, 60%, and 75% MHRR corresponded to 52%, 62%, and 76% of V̇O_2max. Although the best method for analyzing HR data to describe physical activity intensity is unknown, use of 140 and 160 cutpoints may not describe vigorous or very hard exercise in adolescent girls as well as 75% MHRR. Researchers should also consider the effects of adiposity when using specific heart rate cutpoints.

Junior high school male basketball players (n = 10) were assessed during a 55-min practice to evaluate the validity of the Computer Science and Applications, Inc. (CSA) accelerometer for estimating physical activity (PA). Direct observation (Five-Level Children’s Activity Rating Scale [CARS]) and heart rate monitoring (HR) were used as criterion measures. CSA, CARS, and HR values were recorded during each minute of practice. Correlation using group data showed a moderate to good (r = 0.60; P < .001) relationship between CSA and HR. Individual participant analyses revealed a significant correlation (range 0.54–0.81; P < .001) between CSA and HR in nine of ten subjects. ANOVA revealed significant differences (P < .001) in CSA and HR in values associated with CARS levels 2–4. The CSA provides valid estimates of PA intensity (compared to CARS and HR) during basketball played by adolescent boys. It appears that CSA is sufficiently sensitive to quantify physical activity level as well as to discriminate between various intensity levels that exist during a typical basketball practice session.

Pregnant and postpartum women have reported a number of barriers that prevent them from being sufficiently physically active. Overcoming these barriers is critical to ensure the health benefits of physical activity to both mother and fetus. The primary focus of this review centers on the potential impact social support may have in overcoming each of the primary barriers to physical activity experienced during pregnancy and the postpartum period. A reasonable body of research exists regarding the relationships between social support and these barriers; however, few investigations have specifically attempted to mitigate the effects of these barriers via social support interventions. Within this review, the enabling influence of social support as it pertains to pregnant and postpartum women's physical activity is discussed. Recommendations are suggested for the application of social support in future research investigations involving physical activity during pregnancy and postpartum.

This study presents 3 years of data from a longitudinal study designed to follow changes in VO₂max and treadmill (TM) exercise performance in African-American girls throughout middle school. Subjects (N = 19) were tested 6 months apart during grades 6-8. VO₉ and heart rates (HR) were measured continuously while each subject performed an incremental TM test to volitional exhaustion. Absolute VO₂max (ml • min¹) increased with time, while relative (ml • kg ¹ * min¹) values declined significantly from 6th to 8th grade. Treadmill time to exhaustion improved after the first test, but showed a significant decline by the end of 8th grade. Correlations between fall 6th-grade and spring 8th-grade aerobic fitness measures ranged from .35 to .57, indicating moderate tracking of these variables throughout middle school. Aerobic fitness values are low (compared to Caucasians) in African-American adolescent girls and show significant declines throughout middle school. Future studies should investigate anatomical, physiological, and behavioral reasons for the apparently low aerobic fitness seen in African-American girls.

This study investigated the validity of the Caltrac accelerometer for estimating resting and exercise energy expenditure for children. Seventeen children 9 to 12 years of age participated in the study. Criterion values of energy expenditure were determined from measures of oxygen consumption (VO₂) and respiratory exchange ratio (RER), and Caltrac estimates of energy expenditure were obtained concurrently for each experimental condition. Correlations were significant between Caltrac estimates and measured energy expenditure at rest (r = .53, p<.03) and at slow (r = .89, p<.001) and brisk (r = .85, p<.001) treadmill walking. The Caltrac overestimated caloric expenditure for rest (M = 7%; range = −8 to 36%) and also for both slow (M = 17%; range = −3 to 30%) and brisk (M = 25%; range = 5 to 46%) walking. However, because of the high validity coefficients during activity, and because of its practicality in field settings, the Caltrac may be useful in estimating daily resting and walking energy expenditure for groups of children.

Ornithine supplementation has gained popularity with athletes because of its alleged potential to release anabolic hormones, factors governing skeletal muscle hypertrophy. Three female and nine male bodybuilders sewed as subjects in a study to test the effectiveness of oral ornithine in bringing about the release of insulin, an anabolic hormone. After an overnight fast, subjects were administered 40, 100, or 170 mg·kg⁻¹ L-ornithine.HC1 by mouth in a random fashion on three consecutive Saturday mornings. Blood samples were drawn at baseline (T=O), 45, and 90 min afterward. Serum ornithine levels were elevated (p~0.01) at T=45 and 90 min for all three dosage levels. However, serum insulin did not change from baseline levels at any dose of ornithine. The present findings show that ornithine is not an insulin secretagogue.

Previous research clearly indicates that exercise training decreases during pregnancy, even among the fittest of women. Despite this, women are typically able to resume their prepregnancy exercise routines soon after delivery, and in some instances, their postpartum performances are better than previously experienced. While anecdotal reports are common, there does not appear to be significant research data to explain this phenomenon. In this review, we explore possible physiologic explanations for heightened postpartum exercise performance, such as pregnancy related changes in aerobic fitness, lactate threshold, flexibility, and musculoskeletal fitness. At this time, limited data do not appear to support an ergogenic role for these variables. Another consideration is a positive change in a woman’s psyche or perceptions toward her athletic abilities as a result of her pregnancy and delivery. While this concept is theoretically possible and may have scientific merit, data are sparse. What is clear is that an increasing number of women are maintaining their physical activity and exercise routines during pregnancy, with many able to return to competition soon after delivery. Well-designed studies are needed to further explore the relationships among physiologic and psychological variables and postpartum exercise performance. Ideally, these studies should be prospective (studying women prepregnancy through the postpartum period) and include diverse samples of women with regard to activity type and fitness level.