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PubMedDate not supplied

Moderate intensity exercise training improves cardiorespiratory fitness in women.

Among women, there is an increased prevalence of sedentary lifestyle and less participation in physical activity at levels recommended by the Surgeon General. As a result, women have been identified as a target group in public health initiatives to increase physical activity. The health-related benefits of habitual, moderate intensity physical activity are well documented in the epidemiological literature, but less is known about the effect of such physical activity on cardiorespiratory fitness. Our hypothesis was that moderate and vigorous exercise training regimens of similar estimated energy expenditure would result in similar changes in cardiorespiratory fitness. Eighteen sedentary premenopausal women with the following baseline characteristics [x +/- SE]: maximal oxygen consumption (Vo2max) = 29.5+/-1.5 ml x kg(-1) x min(-1); age = 33+/-1 years; height = 162.6+/-0.9 cm; mass = 62.7+/-2.3 kg, were randomly assigned to either vigorous (HI, 80% Vo2max, n = 10) or moderate intensity (MOD, 40% Vo2max, n = 8) cycle ergometer training groups. Exercise training was conducted 3-4 (3.37+/-0.05) days/week for 12 weeks in a supervised and progressive manner, with estimated exercise energy expenditure equated across both training groups. Vo2max and time to exhaustion increased significantly in both groups (p<0.05), with no difference between groups. Both groups had lower (p<0.05) posttraining submaximal heart rates (HR), respiratory exchange ratios (RER), and ratings of perceived exertion (RPE) during graded exercise testing, with no significant differences between the groups in posttraining values. Women participating in moderate intensity exercise training as recommended in basic public health guidelines demonstrate an increase in cardiorespiratory fitness similar to that elicited by vigorous training.

Adult↗
PubMed2006

Efficacy of continuous real-time blood glucose monitoring during and after prolonged high-intensity cycling exercise: spinning with a continuous glucose monitoring system.

BACKGROUND: Hypoglycemia is the most common and serious side effect of insulin therapy in type 1 diabetes (T1DM), frequently occurring both during and after vigorous exercise. Late-onset hypoglycemia (LOH) is of great concern, occurring 1-36 h after exercise, often going unnoticed during sleep. Repeated exposure to LOH causes autonomic glucose counterregulatory failure and sometimes coma and death. Continuous glucose monitoring systems have recently emerged as a potentially important tool in diabetes management, allowing individuals to track glucose levels continuously and learn how various behaviors influence glucose control. METHODS: In this pilot study, we determined the efficacy of using a real-time continuous glucose monitoring system (Guardian RT, Minimed, Northridge, CA) to detect blood glucose excursions associated with exercise and LOH (i.e., blood glucose concentration <4 mM) after exercise in individuals with T1DM. Five subjects with T1DM were monitored before, during, and after a 60 min vigorous spin class using Guardian RT (48 h in total). RESULTS: Following the exercise, three of the five subjects had LOH, while the other two experienced decreases in blood glucose concentrations to 4 mM. The Guardian RT monitor was effective in notifying all of the subjects of such glycemic excursions over the 48 h surveillance period. A strong correlation (r = 0.89, P < 0.001) was found between conventional self-monitoring of blood glucose and Guardian RT data pairs. CONCLUSION: These limited data suggest that nocturnal LOH occurs commonly following vigorous exercise and that a Guardian RT is a useful and important diagnostic tool. Further study into clinical strategies for preventing hypoglycemia associated with this common form of mixed aerobic and anaerobic exercise is urgently needed through insulin modification and carbohydrate supplementation.

Adult↗
PubMed2002

Physical inactivity is associated with lower forced expiratory volume in 1 second : European Prospective Investigation into Cancer-Norfolk Prospective Population Study.

Forced expiratory volume in 1 second (FEV(1)) is a strong risk factor for cardiovascular disease, stroke, lung cancer, and all-cause mortality. One possible explanation for this association is that FEV(1) is a marker of other determinants of mortality risk, such as obesity and physical inactivity. In a population-based cohort study of 12,283 men and women aged 45-74 years from the European Prospective Investigation into Cancer-Norfolk Study recruited in 1993-1997, the cross-sectional association between physical activity and FEV(1) and that between physical activity and change in FEV(1) were analyzed. Indices of physical activity, including participation in vigorous recreational activity, stair climbing, and television viewing, were assessed with a validated questionnaire designed to assess activity in the previous year. Television viewing was negatively associated with FEV(1) in men and women (p < 0.001), whereas stair climbing and participation in vigorous leisure time activities were positively associated with FEV(1) in men and women (p < 0.001). The associations remained after adjustment for known confounders, including age, height, vitamin C, and smoking. Climbing more stairs and participating in vigorous leisure-time activity predicted a slower rate in annual percent decline in FEV(1) (p < 0.004 and p < 0.002, respectively). In conclusion, physical activity is associated with higher levels of FEV(1), whereas television viewing is associated with lower levels.

Aged↗
PubMed2002

Physical activity and menstrual cycle characteristics in two prospective cohorts.

Relations between physical activity and prospectively collected menstrual cycle characteristics were examined in two large cohorts. One cohort consisted of women employed in the semiconductor industry in 1989 who participated in a prospective study of reproductive outcomes (n = 367). The other consisted of women living in Tecumseh, Michigan, who completed both the 1992-1993 and 1993-1994 examinations for the Michigan Bone Health Study (n = 328). Mean cycle length, variability of cycle length, and mean bleed length were calculated from daily diaries (Semiconductor cohort) or monthly menstrual calendars (Michigan cohort) for a median of five and 11 cycles, respectively. Physical activity was assessed by self-report at baseline and expressed as metabolic equivalent-minutes per week. In the Semiconductor study, women also reported daily minutes of vigorous exercise in their diaries. In the Michigan cohort, total physical activity, total recreational physical activity, and vigorous recreational activity were positively associated with cycle length. The magnitude of these associations declined as body mass index increased. In the Semiconductor cohort, the minutes of daily vigorous exercise were positively associated with cycle length only in a repeated-measures analysis. These findings lend modest support to the hypothesis that moderate levels of physical activity can lengthen the menstrual cycle.

Adult↗
PubMed2006

Physical activity, insulin sensitivity, and hypertension among US adults: findings from the Insulin Resistance Atherosclerosis Study.

Although regular physical activity is associated with less hypertension and improved insulin sensitivity, there is debate regarding the role of insulin sensitivity in hypertension. Thus, in this cross-sectional study, the authors investigated whether physical activity and insulin sensitivity were associated with hypertension. The sample consisted of 1,599 persons aged 40-69 years who participated in the Insulin Resistance Atherosclerosis Study. The outcome measure was hypertension as measured by a standard protocol. Energy expended in vigorous physical activity was calculated from a recall interview on past-year physical activity. Descriptive statistics revealed that 590 (37%) participants had prevalent hypertension. In adjusted logistic regression analysis, participants expending >or=150 kcal/day in vigorous physical activity had an odds ratio for hypertension of 0.73 (95% confidence interval (CI): 0.55, 0.98) in comparison with participants who were sedentary. Further adjustment for insulin sensitivity resulted in attenuation of the effect of vigorous physical activity on hypertension (odds ratio = 0.97, 95% CI: 0.71, 1.33), while the effect of insulin sensitivity was significant (odds ratio = 0.33, 95% CI: 0.26, 0.41). These results suggest that longitudinal studies are warranted to determine whether insulin sensitivity is a mediator of the relation between physical activity and hypertension.

Adult↗
PubMed2000

Relationship between selected personality traits and citation for violating pharmacy board regulations.

The relationship between certain personality traits and citation for pharmacy board violations was studied. The Gordon Personal Profile-Inventory (GPP-I) was mailed to three samples of pharmacists licensed in North Carolina (95 pharmacist leaders, 199 pharmacists who had been cited for violating one or more board of pharmacy regulations, and a random sample of 494 pharmacists licensed in the state). The pharmacists were asked to provide demographic information and to complete the 38-item GPP-I, which measures eight different personality traits (ascendancy, responsibility, emotional stability, sociability, cautiousness, original thinking, personal relations, and vigor). The response rates for the three samples were 78.9%, 23.6%, and 58.3%, respectively. Pharmacists who had been cited for one or more board of pharmacy violations had significantly lower scores on the GPP-I for the personality trait vigor than general pharmacists. They also had lower scores on the GPP-I traits of ascendancy, original thinking, and vigor than pharmacy leaders. They were less likely to have advanced degrees or belong to any pharmacy organizations. They tended to be male, older, and out of school longer than those pharmacists who had never been cited for violating one or more board of pharmacy regulations. Significant differences in personality traits were found between pharmacists who had been cited for violating board of pharmacy regulations and general pharmacists and pharmacy leaders.

Adult↗
PubMed2005

Influence of the gibberellin-sensitive Rht8 dwarfing gene on leaf epidermal cell dimensions and early vigour in wheat (Triticum aestivum L.).

BACKGROUND AND AIMS: The gibberellin-insensitive Rht-B1b and Rht-D1b dwarfing genes are known to reduce the size of cells in culms, leaves and coleoptiles of wheat. Resulting leaf area development of gibberellin-insensitive wheats is poor compared to standard height (Rht-B1a and Rht-D1a) genotypes. Alternative dwarfing genes to Rht-B1b and Rht-D1b are available that reduce plant height, such as the gibberellin-responsive Rht8 gene. This study aims to investigate if Rht8 has a similar dwarfing effect on the size of leaf cells to reduce leaf area. METHODS: The effect of Rht8 on cell size and leaf area was assessed in four types of epidermal cells (interstomatal, long, sister and bulliform) measured on leaf 2 of standard height (rht8) and semi-dwarf (Rht8) doubled-haploid lines (DHLs). The DHLs were derived from a cross between very vigorous, standard height (rht8) ('Vigour18') and less vigorous, semi-dwarf (Rht8) ('Chuan-Mai 18') parents. KEY RESULTS: Large differences were observed in seedling vigour between the parents, where 'Vigour18' had a much greater plant leaf area than 'Chuan-Mai 18'. Accordingly, 'Vigour18' had on average longer, wider and more epidermal cells and cell files than 'Chuan-Mai 18'. Although there was correspondingly large genotypic variation among DHLs for these traits, the contrast between semi-dwarf Rht8 and tall rht8 DHLs revealed no difference in the size of leaf 2 or average cell characteristics. Hence, these traits were independent of plant height and therefore Rht8 in the DHLs. Correlations for leaf and average cell size across DHLs revealed a strong and positive relationship between leaf width and cell files, while the relationships between leaf and cell width, and leaf and cell length were not statistically different. The relative contribution of the four cell types (long, sister, interstomatal and bulliform) to leaf size in the parents, comparative controls and DHLs is discussed. CONCLUSIONS: Despite a large range in early vigour among the DHLs, none of the DHLs attained the leaf area or epidermal cell size and numbers of the vigorous rht8 parent. Nonetheless, the potential exists to increase the early vigour of semi-dwarf wheats by using GA-sensitive dwarfing genes such as Rht8.

Genes, Plant↗
PubMed1993

Effects of sustained training on left ventricular structure and function in top level rowers.

The effects of vigorous training on left ventricular structure and function were evaluated in 15 top level rowers using electrocardiography, Doppler echocardiography and radionuclide angiography. All subjects were studied after 1 month of deconditioning and again after 5 months of vigorous training. After training there was an increase in the ventricular hypertrophy voltage criteria proposed by Sokolow-Lyon and by Friedman but not in that proposed by Casale; T wave amplitude in leads V5 and V6 increased in nine subjects, was unchanged in one and decreased in five; the mean values were also unchanged. Training induced a significant increase in left ventricular end-diastolic and end-systolic diameter and in left ventricular mass index, while peak systolic stress and mean wall stress index decreased. No change was detected after training in the mean values of Doppler echocardiographic and radionuclide angiographic data; nevertheless a significant relationship was found between changes in T wave height in V5 or V6 and in peak filling rate, and between changes in T wave height and ejection fraction. Our study confirms that the effect of vigorous training on left ventricular mass and dimensions does not include changes in mean values of systolic and diastolic function. The relationship between change in T wave amplitude and in peak filling rate values suggests that some metabolic or neurohumoral derangement occurs in the subset of athletes with T wave flattening, that is responsible for the slight reduction in peak filling rate and ejection fraction.

Adolescent↗
PubMed2006

Increasing children's physical activity levels during recess periods in elementary schools: the effects of providing game equipment.

BACKGROUND: During recess, children can be active on a daily basis, making it an important school environmental factor for the promotion of health-related physical activity. The aim of the present study was to investigate the effects of providing game equipment on children's physical activity levels during morning recess and lunch break in elementary schools. METHODS: Seven elementary schools were randomly assigned to the intervention group (four schools), including 122 children (75 boys, 47 girls, mean age: 10.8 +/- 0.6 years), and to the control group (three schools), including 113 children (46 boys, 67 girls, mean age: 10.9 +/- 0.7 years). Children's activity levels were measured before and three months after providing game equipment, using MTI accelerometers. RESULTS: During lunch break, children's moderate and vigorous physical activity significantly increased in the intervention group (moderate: from 38 to 50%, vigorous: from 10 to 11%), while it decreased in the control group (moderate: from 44 to 39%, vigorous: from 11 to 5%). At morning recess, providing game equipment was effective in increasing children's moderate physical activity (from 41 to 45%), while it decreased in the control group (from 41 to 34%). CONCLUSION: Providing game equipment during recess periods was found to be effective in increasing children's physical activity levels. This finding suggests that promoting physical activity through game equipment provision during recess periods can contribute to reach the daily activity levels recommended for good health.

Analysis of Variance↗
PubMed2001

Effects of housing relocation on immunocompetence and psychosocial functioning in older adults.

BACKGROUND: The psychological and physical response to moderate life stressors among older adults has not been well characterized. This research examines effects of voluntary housing relocation on distress and immune function in healthy older adults as a model for studying the effects of moderate life stress. METHODS: Thirty older adults moving to congregate living facilities were assessed 1 month premove, 2 weeks postmove, and 3 months postmove. Twenty-eight nonmoving control subjects were assessed at similar time points. Subjects completed psychosocial questionnaires and had early morning blood draws in their homes. Blood samples were assayed for natural killer cell cytotoxicity (NKCC), interleukin-6 (IL-6), and IgG antibody titers to the Epstein Barr virus (EBV) viral capsid antigen. RESULTS: Movers demonstrated decreased vigor and elevated thought intrusion 1 month premove and 2 weeks postmove. By the 3-month follow-up, vigor increased, and intrusion decreased to levels commensurate with the controls. Averaged across all time points, movers showed lower NKCC than controls; however, post-hoc analyses indicate that by the 3-month follow-up time point, these differences were no longer significant. There were no differences between groups in IL-6 or in EBV antibody titers. Independent of the effects of group, higher levels of vigor were associated with greater NKCC at all assessments and with lower EBV titers at 2 weeks postmove. CONCLUSIONS: Findings suggest that in general, healthy older adults recover well psychologically from moderate. temporary life stressors such as moving. Whereas movers showed generally lower NKCC than controls, IL-6 and EBV antibody titers appeared not to be strongly affected by the stress of moving.

Adaptation, Psychological↗
PubMed2004

The Stages of Change in three stage concepts and two modes of physical activity: a comparison of stage distributions and practical implications.

Stages of Change were assessed for three stage definitions and two modes of health-enhancing physical activity (HEPA) in a representative telephone survey in Switzerland (participation 55.8%; n = 1471). Two five-stage definitions focusing either on intention to change or current behavior were integrated into a seven-stage concept, taking into account both aspects. The two target behaviors were activities with at least moderate intensity and activities with vigorous intensity. According to the two five-stage definitions, at least half of the participants were either in precontemplation (focus on intention) or in preparation (focus on behavior). Upon classification into the seven stages these large stage groups were differentiated. There were differences in the pros for change between the new stages of the seven-stage concept. One in seven participants was regularly active according to the moderate criteria, but not using the vigorous criteria, and one in every eight participants reported the inverse. Results show that an individual can be in different Stages of Change depending on the stage definition and be regularly active or not depending on the target behavior. The practical implications of the seven-stage algorithm and a two-dimensional matrix to classify participants for both moderate and vigorous intensity activities in an Internet-based HEPA program are presented.

Adult↗
PubMed2000

A prospective study of physical activity and risk of prostate cancer in US physicians.

BACKGROUND: Exercise can suppress androgen production and may thus decrease the risk of prostate cancer. However, findings from epidemiological studies assessing physical activity and risk of prostate cancer are inconsistent. METHODS: We prospectively examined the association between physical activity and prostate cancer risk in the Physicians' Health Study (PHS), a randomized trial of low-dose aspirin and beta-carotene among 22,071 men aged 40-84 without self-reported myocardial infarction, stroke and cancer. At baseline in 1982, men were asked about the frequency of exercise vigorous enough to work up a sweat. Physical activity was assessed in a similar fashion again at 36 months of follow-up. RESULTS: During 11.1 years of follow-up (258 779 person-years), 982 cases of prostate cancer occurred and were confirmed by medical record review. After adjustment for potential confounding factors (including age, height, randomized treatment assignment, smoking status, alcohol intake, use of multivitamins, history of diabetes, history of hypertension and history of high cholesterol), the relative risks for prostate cancer associated with exercise vigorous enough to work up a sweat were 1.0 (referent) for frequency less than once per week, 1.02 (95% CI: 0.82-1.26) for once per week, 1.07 (95% CI: 0.90-1.27) for 2-4 times per week, and 1.11 (95% CI: 0.90-1.36) for 5+ times per week. Across all subgroups of men categorized by age, body mass index, smoking status, alcohol intake, use of multivitamins, history of diabetes, history of hypertension and history of high cholesterol, there were no significant associations between frequency of exercise vigorous enough to work up a sweat and prostate cancer risk. After excluding cases of prostate cancer that occurred during the first 36 months of follow-up, again, there was no significant association. Combining physical activity assessments at baseline and at 36 months also yielded no significant association with prostate cancer risk. CONCLUSIONS: These observational data from the Physicians' Health Study do not support the hypothesis that increased physical activity reduces the risk of prostate cancer.

Adult↗
PubMed2004

A prospective study of plasma C-peptide and colorectal cancer risk in men.

BACKGROUND: Colorectal cancer and type 2 diabetes share many risk factors, and hyperinsulinemia appears to be associated with an increased risk of colorectal cancer. We used the concentration of plasma C-peptide (an indicator of insulin production) to determine whether insulin and insulin resistance are associated with the risk of developing colorectal cancer. METHODS: We conducted a nested case-control study in the Physicians' Health Study. Plasma samples were collected from 14 916 cancer-free men from August 1982 through December 1984. Plasma C-peptide concentration, measured with an enzyme-linked immunosorbent assay, was available for 176 case patients who developed incident colorectal cancer through December 31, 1995, and 294 age- and smoking status-matched control subjects. Information on four other insulin resistance-related factors at baseline was obtained. We used conditional logistic regression models to investigate associations. All statistical tests were two-sided. RESULTS: Plasma C-peptide concentration was positively associated with age, body mass index (BMI), and number of insulin resistance-related factors, and it was inversely associated with fasting time before the blood draw, alcohol consumption, and vigorous exercise. An increased concentration of plasma C-peptide was statistically significantly associated with an increased risk of colorectal cancer (relative risk [RR] for the highest versus lowest quintile of plasma C-peptide = 2.7, 95% confidence interval [CI] = 1.2 to 6.2; P(trend) =.047), after adjusting for age, smoking status, fasting, BMI, alcohol consumption, vigorous exercise, and aspirin assignment in the Physicians' Health Study. The association became even stronger when the analysis was further adjusted for factors related to insulin resistance other than insulin levels (RR for the highest versus lowest quintile = 3.4, 95% CI = 1.4 to 8.3; P(trend) =.02) or when data from case patients who were diagnosed during the first 5 years of follow-up were excluded (RR for the highest versus the lowest quintile = 3.4, 95% CI = 1.3 to 8.8; P(trend) =.03). Adjusting for plasma levels of insulin-like growth factor I (IGF-I) and its binding protein 3 (IGFBP-3) did not materially change the results. There was no apparent modification of risk by BMI, insulin resistance-related factors, or vigorous exercise. CONCLUSION: Elevated insulin production, as reflected by elevated concentrations of plasma C-peptide, may predict the risk of developing colorectal cancer, independently of BMI, factors related to insulin resistance, or levels of IGF-I and IGFBP-3.

Adult↗
PubMed1991

Reliability of long-term recall of participation in physical activity by middle-aged men and women.

The reliability of long-term recall of physical activity participation was examined in 322 women and 129 men in a worksite health study conducted at the Liberty Corporation, Greenville, South Carolina during 1976-1987. Leisure time physical activity was assessed at baseline; and energy expenditure in total, light, moderate, and vigorous activities was calculated. The long-term recall of baseline activities was determined 1-10 years after the examination. The relation between actual baseline and recalled activity was positive and in most cases the coefficients were statistically significant at p less than 0.05. The correlations were modest, most in the range of 0.20 to 0.50. Percent agreement between baseline and recalled activity generally ranged from 60 to 75%. Multiple regression analyses suggested that recalled activity was a significant predictor of baseline activity, but recall interval and age were not important contributors to the regression model. R2 values for the model were 0.10 for light activity and 0.26 for vigorous activity. Questionnaire assessment of long-term physical activity recall appeared to be reliable, length of recall interval up to 10 years was not an important factor, and recall of vigorous activity was more accurate than for less intensive activities.

Female↗
PubMed1994

Preliminary characterization of a factor in human follicular fluid that stimulates human spermatozoa motion.

Follicular fluid alters the physiology and behaviour of spermatozoa by increasing acrosome reaction, accelerating capacitation, attracting the spermatozoon and enhancing vigorous motion of the cell. The objective of this study was to characterize the factor(s) in human follicular fluid that causes vigorous spermatozoa motion. Follicular fluid and its fractions were tested for stimulation of spermatozoa motion using a standardized assay which employs a computerized digital imaging system. Our results show that both follicular fluid and its methanol extract stimulate vigorous spermatozoa motion. To determine the characteristics of the active factor(s), the methanol extract was subjected to molecular weight fractionation, protease digestion, microcrystalline thin-layer chromatography (TLC) and C18 reverse-phase high-pressure liquid chromatography (HPLC). The spermatozoa motion stimulator in the methanol extract was dialysable against a low molecular weight membrane (1000 Da), insensitive to boiling and low pH (3.5) and was largely inactivated by proteinase K digestion. The activity was detected near the solvent front on TLC. Using reverse-phase HPLC monitored at 254 nm (UV), the activity eluted as a single peak of activity at low methanol concentration, indicating that the activity was relatively hydrophilic. The activity in the HPLC peak lost most of its motion-stimulating ability after digestion with proteinase K. The motion stimulator could be a peptide analogous to the egg-associated peptides characterized in echinoderms which stimulate spermatozoa motion, respiration and chemotaxis.

Chemical Fractionation↗
PubMed1982

Whirlpool versus whirlpool rinse for removal of bacteria from a venous stasis ulcer.

The number of bacteria removed from a venous stasis ulcer by whirlpool treatment alone and that removed by whirlpool treatment followed by vigorous rinsing are compared. A single subject received the whirlpool treatment followed by the rinse on 12 separate occasions. The number of bacteria removed was determined by taking samples of the whirlpool water after the subject's whirlpool treatment and again after rinsing the subject's ulcer over the whirlpool. The samples were cultured on agar plates. By calculating the number of bacterial colonies on the plates, the number of bacteria removed by each treatment was determined. The whirlpool treatment followed by vigorous rinsing was found to remove more than four times as many bacteria as the whirlpool treatment alone. Though performed on a single subject, this clinical pilot study suggests that vigorous rinsing of contaminated ulcer following removal from the whirlpool can remove additional bacteria.

Bacterial Infections↗
PubMed2003

Shoot growth and crown development: effect of crown position in three-dimensional simulations.

Trees have been increasingly considered as modular organisms, with individual shoots forming autonomous units that respond semi-independently to their surrounding environment. However, there is evidence for fairly strict hormonal control of tree crown development. Studies on the hydraulic architecture of trees suggest a closer functional connection between shoots and crown development than is postulated by the theory of branch autonomy. We studied how shoot growth pattern influences growth and crown architecture in young Scots pine trees simulated by the LIGNUM model assuming that (a) the growth of a shoot mainly depends on its light climate and (b) the growth of a shoot is influenced by its position within the crown. We determined shoot position within the crown based on a recently developed vigor index. The vigor index compares the relative axis cross-sectional area from the base of the tree to each shoot and gives a value of 1 to the pathway of the greatest cross-sectional area. All other shoots attain values between 0 and 1 depending on their cross-sectional areas and the cross-sectional areas of the branches leading there from the main axis. The shoot light climate is characterized by annually intercepted photosynthetically active radiation. We compared the results from simulations (a) and (b) against an independent data set. The addition of a within-shoot position index (the vigor index) to our simulation (simulation b) resulted in a more realistic tree form than that obtained with simulation (a) alone. We discuss the functional significance of the results as well as the possibilities of using an index of shoot position in simulations of crown architecture.

Models, Biological↗
PubMed2002

Physical activity, body mass index, and ovulatory disorder infertility.

Few studies have examined whether activity and adiposity levels typical of American women affect their risk of ovulatory disorder infertility, and none has examined moderate and vigorous intensity exercise separately. We investigated these associations in the Nurses' Health Study II, comparing prospectively collected data on adiposity and activity for 830 cases of incident ovulatory infertility and 26,125 pregnancies. We observed a U-shaped association between body mass index (BMI) and relative risk of ovulatory infertility, with increased risk for BMI below 20.0 or above 24.0 kg/m2. On the basis of the BMI distribution of U.S. women, these findings suggest that 12% (95% confidence interval = 7-20%) of ovulatory infertility in the U.S. may be attributable to underweight (BMI <20.0) and 25% (95% CI = 20-31%) to overweight (BMI > or = 25.0). An increase in vigorous activity (but not moderate activity) was associated with reduced relative risk of ovulatory infertility. Each hour per week of vigorous activity was associated with a 7% (95% CI = 4-10%) lower relative risk of ovulatory infertility. After adjustment for BMI, a 5% (95% CI = 2-8%) reduction in relative risk per hour of weekly activity remained. These data suggest that, among American women, more ovulatory infertility is attributable to overweight and a sedentary lifestyle than to underweight and overexertion.

Body Mass Index↗