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PubMed1999

Status of the year 2000 health goals for physical activity and fitness.

In Healthy People 2000, the national strategy for improving the health of the American people by the year 2000, lifestyle factors such as physical inactivity are major determinants of chronic disease and disability. Despite the documented benefits of exercise in enhancing health and reducing the risk of premature death, only 1 of the 13 physical activity and fitness objectives of Healthy People 2000 has been met or exceeded. Although progress toward 5 objectives for the year 2000 has been made, 3 objectives are actually farther from attainment. Coronary heart disease death rates (Objective 1.1) have declined, and the prevalence of overweight people (Objective 1.2) has increased. Overall physical activity in adults (Objectives 1.3 and 1.4) and strengthening and stretching activities in children (Objective 1.6) have increased, but reduction in the percentage of sedentary persons (Objective 1.5) has showed no change. The proportion of the population adopting sound dietary practices combined with regular physical activity to attain appropriate body weight (Objective 1.7) has declined. Even though participation in daily school physical education (Objective 1.8) has shown a decline during the past several years, students who are enrolled in physical education classes are spending more time performing physical activities (Objective 1.9). The proportion of work sites offering employer-sponsored physical activity and fitness programs (Objective 1.10) has increased substantially, surpassing the year 2000 goal. Data to update progress for increasing physical activity levels of children (Objectives 1.3-1.5), community exercise facilities (Objective 1.11), clinician counseling about physical activity (Objective 1.12), and improvement in personal self-care activities (Objective 1.13) are not yet available.

Adolescent↗

PubMed2003

Promoting physical activity in a multi-ethnic district - methods and baseline results of a pseudo-experimental intervention study.

BACKGROUND AND DESIGN: A combined community and high-risk intervention study of three years duration started in one district in Oslo after a baseline health survey in two multi-ethnic and low socio-economic status (SES) districts, using a pseudo-experimental design with an age-matched sample from the other district as controls. The intervention focused on promoting physical activity to reduce the burden of type 2 diabetes and cardiovascular disease (CVD). METHODS: A total of 6140 subjects were invited to participate (age group: 31-67). Data on health status and health-related behaviours, collected via standardized questionnaires, physical examinations and blood sample analyses, were available for 2950 persons (attendance rate 48%), whereas official statistics were available for the invited population. RESULTS: The prevalence of self-reported diabetes was 5.1% in men and 3.5% in women, but the total diabetes prevalence was 9% for men and 5.1% for women. One-third of the population were sedentary in their leisure time, men more than women (38% versus 29%). The prevalence of obesity did not differ between the genders (21% had BMI 30 kg/m(2)). The relatively high mean scores on most psychosocial variables related to physical activity, especially among women, indicate a high motivational readiness for increase in physical activity behaviour. The baseline data, for example on the prevalence of chronic diseases were similar in the two districts. CONCLUSION: The prevalence of self-reported diabetes is remarkably higher than reported from other studies in Norway. The proportion of undiagnosed diabetes was higher than anticipated, and constituted 39% of all those categorized as diabetics.

Cardiovascular Diseases↗

PubMed2001

Maintenance of physical activity following an individualized motivationally tailored intervention.

This study examined predictors of exercise maintenance following completion of a physical activity intervention. Sedentary adults recruited through newspaper advertisements were randomly assigned to receive either (a) a motivation-matched intervention with feedback reports that were individually tailored (IT) to psychological variables from social cognitive theory and the Transtheoretical Model via computer expert system, or (b) a standard, print-based intervention (ST). The intervention phase of the study included mailed assessments and intervention materials at baseline, 1, 3, and 6 months. An assessment-only follow-up was conducted 6 months after the end of the intervention (Month 12). Participants were assessed for current physical activity participation, motivational readiness for physical activity, a number of psychological constructs posited to influence participation in physical activity (e.g., self-efficacy), and current affect. Significantly more participants in the IT condition met or exceeded exercise participation goals at the end of the intervention period and maintained this level of physical activity through the Month 12 follow-up compared to ST participants. Prospective analyses revealed significant differences in several psychological constructs both at program entry (baseline) and the end of the intervention period between individuals who maintained their physical activity participation through Month 12 and those who did not. Results suggest that the maintenance of physical activity following the end of an active intervention program may be influenced by attitudes and behaviors acquired along with increased participation in physical activity, as well as by preexisting characteristics that individuals bring into treatment.

Adult↗

PubMedDate not supplied

Changes in steps per day over the course of a pilot walking intervention.

UNLABELLED: The objective of this study is to explicate changes in steps per day observed over the course of a pilot study concerned with promoting walking. A pre/post single group design was used to evaluate a 12-month group intervention with 6-month follow-up with a sample of twenty-one sedentary, hypertensive African American women 25-68 years of age. A 3-hour monthly meeting was paired with an at-home walking component. Results indicated that the total group experienced a slight increase (5%) in mean steps per day at the end of the 12-month intervention, while a subgroup experienced a 13% decrease. However, mean steps per day increased from baseline to 6-month follow-up for both groups. Mean steps per day increased from 3857 to 5582 (37%) for total group and from 4659 to 7038 (51%) for the subgroup. CONCLUSIONS: A group intervention can have a positive impact on promoting walking among African American women; however, multi-phased interventions may be necessary to assist this population meet current physical activity recommendations.

Adult↗

PubMed1994

High intensity exercise during pregnancy of rats. Effects on mother and offspring.

We see in this study the effect of high intensity exercise (90% VO2 max) in pregnant rats and their offspring depending on the length of pregnancy. The findings were compared with those obtained for sedentary pregnant rats and non-pregnant rats for similar exercise. This allowed for analysing the isolated effects of exercise (against the sedentary non-pregnant rat control group), of pregnancy and of the interaction between the two factors. For checking the effect of the length of pregnancy, each group of rats was subdivided into those with pregnancy terminated or sacrificed on the seventh, fourteenth or twentieth day of the experiment. VO2 max, post-exertion blood lactic acid level, body weight gain, food intake, feed efficiency, glucose, triglyceride, total cholesterol, total protein and albumin plasmatic concentrations in adult rats, and weight and number of offspring of pregnant rats were determined. Pregnancy increased weight gain and feed efficiency from the first week of the study, accompanied by a greater food intake (from the twelfth day). In the group of pregnant rats subjected to exercise, there was a reduction in weight gain percentage and feed efficiency in the first and third weeks, staying the same in the second week. A greater food intake during the period accompanied this recovery in the second week. In the group of non-pregnant rats subjected to exercise, food intake did not vary. As the weight gain percentage was less in relation to the non-pregnant control group, feed efficiency decreased. Pregnancy induced a drop in blood sugar level starting in the second week, and the exercise performed during pregnancy did not change this behavior. Pregnancy produced, however, an increase in plasmatic concentration of triglycerides and total cholesterol during the third week of pregnancy. Exercise performed by pregnant rats also did not change this behavior, but the increase observed in the third week was less. Exercise performed by non-pregnant rats did not change the blood sugar level and plasmatic concentration of triglycerides and total cholesterol during the entire experiment. Plasmatic concentration of total proteins and albumin showed a drop in the third week of pregnancy, probably due to high fetal use of proteins in this stage. Exercise performed by the pregnant group caused a lower protein drop in the third week, and in the non-pregnant group, determined an increase in plasmatic protein concentrations.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMedDate not supplied

Motivations for exercise and weight loss among African-American women: focus group results and their contribution towards program development.

OBJECTIVE: African-American women are more likely to be sedentary and maintain higher body weights compared with Caucasian women, although some are physically active and able to maintain weight loss. To develop effective intervention strategies, we need to understand why some women are successful. DESIGN: We conducted focus groups on four distinct groups of African-American women (currently physically active; currently sedentary; successful weight loss for > or = 1 year; unsuccessful weight loss) to explore motivations and intervention strategies. Open-ended questions, probes, and visual aids were used to stimulate discussions. Transcripts of sessions were read to highlight themes and concepts. RESULTS: Results indicated that motivators for the exercisers to start exercising were health concerns, weight control, stress reduction, and the influence of others. Motivators to continue exercising were feeling good and having energy. In contrast, the sedentary women reported that social support and enjoyment would be motivating. Both groups reported that physically active women conveyed the image of high energy and self-esteem. The successful weight loss women employed strategies that allowed them to eat a variety of foods and were less likely to 'diet'. The unsuccessful women referred to 'going on a diet' and were more likely to label foods as 'good' or 'bad'. They reported feeling tired and thought that losing weight would give them more energy. CONCLUSION: This information was used to develop two culturally appropriate interventions for African-American women, which is presented. Conducting formative research in study design protocols can provide an important role in intervention development.

Adult↗

PubMed1996

Angina in patients with an active lifestyle.

The care of the active angina patient comprises risk stratification, risk factor modification, cardiac rehabilitation and pharmacotherapy. Risk stratification may be undertaken using a symptom limited exercise test, with the possibility of myocardial perfusion imaging to improve sensitivity. Higher risk patients may be evaluated angiographically. Risk factor modification should be tailored to the individual patient and should include weight reduction, cessation of smoking, treatment of hypertension and a controlled increase in levels of exercise for the sedentary patient. Cardiac rehabilitation is comprised of patient education, risk factor management and an individualized exercise prescription, based on a symptom-limited exercise tolerance test. Exercise training is associated with measurable physiological improvements in exercise tolerance. The risk of myocardial infarction due to sudden bouts of heavy exertion is also reduced, by approximately 50-fold, in those who exercise regularly. Pharmacological management should be based on the patient's anginal threshold. Those with a high threshold may be treated symptomatically with nitroglycerin, while beta-blockers may be the most appropriate therapy for those with a lower threshold. Those with a variable threshold may respond better to calcium channel blockers. Long-acting agents are preferred, ideally providing therapeutic coverage in the morning, and throughout the day, until the next daily dose reaches therapeutic levels.

Angina Pectoris↗

PubMed1975

Adipose tissue cellularity and lipolysis. Response to exercise and cortisol treatment.

Male rats a 5 wk of age were subjected to 13 wk of intensive treadmill running to study the effect of exercise on adipose tissue cellularity and lipolysis. Untrained controls of the same age remained sedentary in their cages for the duration of the experiment. Adipocyte numbers were similar in eqidiymal fat pads from trained and untrained rats (12.7 plus or minus 1.3 X 10(6) vs. 15.3 plus or minus 1.3 X 10(6) cells/pad), however trained rats had smaller fat pads containing smaller cells (0.09 plus of minus 0.01 vs. 0.20 plus or minus 0.04 mug triglyceride/cell). Adipocytes from trained rats possessed greater epinephrine-sensitive lipase activity than sedentary rats on a per cell, per milligram protein, per gram adipose tissue, or per fat pad basis. Although the smaller cells of the trained rats had greater epinephrine-sensitive lipase activity than the larger cells of the untrained rats, lipolysis was positively correlated with cell size within both treatment groups. Cortisol treatment of intact animals did not significantly affect in vitro adipose tissue lipolysis. The results of this study indicate that exercise training increased the potential of adipose tissue cells to release free fatty acids in response to epinephrine stimulation. Exercise training initiated at 5 wk of age had only a small effect on adipose tissue cell numbers but significantly decreased cell size.

Adenylyl Cyclases↗

PubMed1997

Pediatric obesity. An overview of etiology and treatment.

Pediatric obesity is a chronic and growing problem for which new ideas about the biologic basis of obesity offer hope for effective solutions. Prevalence of pediatric and adult obesity is increasing despite a bewildering array of treatment programs and severe psychosocial and economic costs. The definition of obesity as an increase in fat mass, not just an increase in body weight, has profound influence on the understanding and treatment of obesity. In principle, body weight is determined by a balance between energy expenditure and energy intake, but this observation does not by itself explain obesity. There is surprisingly little evidence that the obese overeat and only some evidence that the obese are more sedentary. Understanding of the biologic basis of obesity has grown rapidly in the last few years, especially with the identification of a novel endocrine pathway involving the adipose tissue secreted hormone leptin and the leptin receptor that is expressed in the hypothalamus. Plasma leptin levels are strongly correlated with body fat mass and are regulated by feeding and fasting, insulin, glucocorticoids, and other factors, consistent with the hypothesis that leptin is involved in body weight regulation and may even be a satiety factor (Fig. 2, Table 1). Leptin injections have been shown to reduce body weight of primates, although human clinical trials will not be reported until summer 1997. So many peptides influencing feeding have been described that one or more may have therapeutic potential (Fig. 2, Table 1). Although the complexity of pathways regulating body weight homeostasis slowed the pace of understanding underlying mechanisms, these complexities now offer many possibilities for novel therapeutic interventions (Fig. 2). Obesity is a major risk factor for insulin resistance and diabetes, hypertension, cancer, gallbladder disease, and atherosclerosis. In particular, adults who were obese as children have increased mortality independent of adult weight. Thus, prevention programs for children and adolescents will have long-term benefits. Treatment programs focus on modification of energy intake and expenditure through decreased calorie intake and exercise programs. Behavior-modification programs have been developed to increase effectiveness of these intake and exercise programs. These programs can produce short-term weight loss. Long-term losses are more modest but achieved more successfully in children than in adults. Several drug therapies for obesity treatment recently have been approved for adults that produce sustained 5% to 10% weight losses but experience with their use in children is limited. Identification of the biochemical pathways causing obesity by genetic approaches could provide the theoretic foundation for novel, safe, and effective obesity treatments. The cloning of leptin in 1994 has already led to testing the efficacy of leptin in clinical trials that are now underway. Although novel treatments of obesity are being developed as a result of the new biology of obesity, prevention of obesity remains an important goal.

Adolescent↗

PubMed1997

Walking to health.

Walking is a rhythmic, dynamic, aerobic activity of large skeletal muscles that confers the multifarious benefits of this with minimal adverse effects. Walking, faster than customary, and regularly in sufficient quantity into the 'training zone' of over 70% of maximal heart rate, develops and sustains physical fitness: the cardiovascular capacity and endurance (stamina) for bodily work and movement in everyday life that also provides reserves for meeting exceptional demands. Muscles of the legs, limb girdle and lower trunk are strengthened and the flexibility of their cardinal joints preserved; posture and carriage may improve. Any amount of walking, and at any pace, expends energy. Hence the potential, long term, of walking for weight control. Dynamic aerobic exercise, as in walking, enhances a multitude of bodily processes that are inherent in skeletal muscle activity, including the metabolism of high density lipoproteins and insulin/glucose dynamics. Walking is also the most common weight-bearing activity, and there are indications at all ages of an increase in related bone strength. The pleasurable and therapeutic, psychological and social dimensions of walking, whilst evident, have been surprisingly little studied. Nor has an economic assessment of the benefits and costs of walking been attempted. Walking is beneficial through engendering improved fitness and/or greater physiological activity and energy turnover. Two main modes of such action are distinguished as: (i) acute, short term effects of the exercise; and (ii) chronic, cumulative adaptations depending on habitual activity over weeks and months. Walking is often included in studies of exercise in relation to disease but it has seldom been specifically tested. There is, nevertheless, growing evidence of gains in the prevention of heart attack and reduction of total death rates, in the treatment of hypertension, intermittent claudication and musculoskeletal disorders, and in rehabilitation after heart attack and in chronic respiratory disease. Walking is the most natural activity and the only sustained dynamic aerobic exercise that is common to everyone except for the seriously disabled or very frail. No special skills or equipment are required. Walking is convenient and may be accommodated in occupational and domestic routines. It is self-regulated in intensity, duration and frequency, and, having a low ground impact, is inherently safe. Unlike so much physical activity, there is little, if any, decline in middle age. It is a year-round, readily repeatable, self-reinforcing, habit-forming activity and the main option for increasing physical activity in sedentary populations. Present levels of walking are often low. Familiar social inequalities may be evident. There are indications of a serious decline of walking in children, though further surveys of their activity, fitness and health are required. The downside relates to the incidence of fatal and non-fatal road casualties, especially among children and old people, and the deteriorating air quality due to traffic fumes which mounting evidence implicates in the several stages of respiratory disease. Walking is ideal as a gentle start-up for the sedentary, including the inactive, immobile elderly, bringing a bonus of independence and social well-being. As general policy, a gradual progression is indicated from slow, to regular pace and on to 30 minutes or more of brisk (i.e. 6.4 km/h) walking on most days. These levels should achieve the major gains of activity and health-related fitness without adverse effects. Alternatively, such targets as this can be suggested for personal motivation, clinical practice, and public health. The average middle-aged person should be able to walk 1.6 km comfortably on the level at 6.4 km/h and on a slope of 1 in 20 at 4.8 km/h, however, many cannot do so because of inactivity-induced unfitness. The physiological threshold of 'comfort' represents 70% of maximum heart rate. (ABSTRACT TRUNCATED)

Cardiovascular Diseases↗

PubMedDate not supplied

General social support and physical activity: an analysis of the Ontario Health Survey.

In spite of the many benefits of regular physical activity, the majority of Canadians are sedentary. This paper examines the relationship between general social support and physical activity levels. An analysis of data on 29,135 individuals from the 1990 Ontario Health Survey was conducted. Hierarchical multiple regression was used to determine the relationship between measures of general social support, derived from factor analysis, and physical activity levels. Sociodemographic and perceived health status measures were included as control variables. The results showed that general social support, in the form of Social Quantity and Social Frequency (number of friends/family members and frequency of contact), was significantly associated with higher levels of physical activity. Conversely, support in the form of Familial Structure (marital/cohabitation and parental status) was significantly associated with lower levels of physical activity. The findings indicate the types of general social support that facilitate or hinder participation in physical activity.

Adult↗

PubMed1994

Muscle strength and fall rates among residents of Japanese and American nursing homes: an International Cross-Cultural Study.

OBJECTIVE: In Western society, aging if often associated with adoption of a sedentary lifestyle and associated disuse muscle atrophy and weakness. Recent studies suggest a relationship between quadriceps muscle weakness and falls in elderly residents of US nursing homes (NHs). We hypothesized that fall rates would be lower in Japanese NHs, where lifestyle differences such as squatting to toilet or sleeping on the floor may maintain quadriceps strength and result in fewer falls. Therefore, we examined the relationships between falls, muscle strength, lifestyle, and other clinical characteristics in residents of a Japanese and an American NH. DESIGN: Cross-culture, prospective, cohort study. MEASUREMENTS: We evaluated disease histories and current medications, quadriceps strength, and mobility of ambulatory American (n = 76) and Japanese (n = 89) NH residents, then followed these residents prospectively for the development of falls. Project staff from both sites trained together to assure uniform data ascertainment. MAIN RESULTS: During a 6-month follow-up period, fall rates were nearly 4-fold higher in the American than in the Japanese residents (49% vs 13%, respectively; P < 0.0001). In the American sample, fall rates declined with increasing muscle strength, while in Japan there was no relationship between fall rates and quadriceps strength. Residents also differed in number of medical diagnoses and use of medications, which were greater among American residents. The Japanese had slower gait speeds. Very few Japanese residents practiced squatting behaviors while living in the NH. CONCLUSIONS: The relationship between muscle weakness and falls is probably modified by multiple characteristics of the individual, their culture, and their environment. Information from cross-cultural studies may provide new insights into effective fall prevention strategies for nursing home residents.

Accidental Falls↗

PubMed2001

Does engagement with life enhance survival of elderly people in Sweden? The role of social and leisure activities.

OBJECTIVES: This research examined whether engagement with life, defined as involvement in social, leisure, and productive activities, produced a survival advantage among oldest old persons in Sweden. Survival was investigated with respect to activities that involved (a) social integration, (b) physical mobility, and (c) neither social nor physical aspects. The authors also investigated the degree to which any observed survival benefits were related to prior health differences that select older adults into active roles. METHODS: Baseline data derived from the Swedish Panel Study of Living Conditions of the Oldest Old, a nationally representative sample of persons aged 77 years and older living in Sweden in 1992. The authors used factor analysis to apply a simplifying measurement structure to frequency of participation in 10 leisure activities. They used Cox proportional hazard regression to estimate the relative effects of activity factors and other independent variables on the logged hazard rate of mortality up to 1996. RESULTS: Analyses revealed 4 domains of activities that lie along 2 basic dimensions: solitary-social and sedentary-active. Among men, only participation in activities that were both solitary and active was significantly associated with reduced mortality risk when health variables were controlled. Among women, none of the activity domains was significant when health variables were controlled. For the entire sample, greater participation in solitary-active activities significantly reduced risk of mortality when all other activity domains and health factors were controlled. DISCUSSION: Although most of the observed associations between activity involvement and survival are a byproduct of the confound between poor initial health and low activity levels, solitary activities have a positive influence on the survival of very old individuals, especially men, suggesting that nonsocial aspects of activities may promote health and longevity in late old age.

Activities of Daily Living↗

PubMedDate not supplied

Factors related to physical activity in Hispanic women.

Hispanic women are more likely to be sedentary than the general population. Increasing physical activity in this at-risk group is an important challenge in the prevention and management of coronary heart disease. This article reviews research conducted with Hispanic women in whom physical activity was the primary focus of study or the primary outcome of interest. Computer and manual searches were performed to identify articles published from 1990 to 2005. Factors that influence physical activity in Hispanic women include self-efficacy, having a concern for own and family health, social support and norms for physical activity, serving as a role model to others, and perceived neighborhood resources. Despite significant efforts to understand and promote physical activity among Hispanic women, much work remains to be done in this area. Future research should include attention to cultural, social, and contextual resources in understanding and promoting physical activity.

Culture↗

PubMedDate not supplied

An exercise program for women who are caring for relatives with dementia.

OBJECTIVE: This study describes factors related to retention and adherence to an exercise program for women caregivers. METHODS: One hundred sedentary women (average age = 62 years) caring for relatives with dementia were randomly assigned to an exercise program or an attention control (nutrition education) condition. Participants in the exercise condition received 12 months of home-based exercise counseling to achieve at least four exercise sessions per week, for at least 30 minutes per session. Adherence was tracked through monthly exercise logs, validated in a subsample by ambulatory heart rate and motion monitors. Participants also completed a psychosocial questionnaire battery at baseline and 12 months after randomization. RESULTS: Participants achieved a 12-month average exercise adherence rate of 74% (ie, three exercise sessions per week) with an average of 35 minutes per session. At 12 months, the exercise condition demonstrated increased knowledge of the benefits of exercise and increased motivational readiness for exercise compared with the nutrition education condition. Both groups significantly improved in perceived stress, burden, and depression from baseline to posttest. Women who were older, less depressed, and more anxious at baseline showed better program retention, and lower baseline depression was associated with better exercise adherence. CONCLUSIONS: This study demonstrates the feasibility and success of delivering home-based health promotion counseling for improving physical activity levels in a highly stressed and burdened population. Given the independent risk factors of caregiving and physical inactivity on mortality, programs to improve healthful behaviors are needed to preserve the health of caregivers as they undertake this important familial and societal role.

Aged↗

PubMed1995

Exercise in middle-aged adults: self-efficacy and self-presentational outcomes.

BACKGROUND: Whereas self-efficacy expectations have been identified as important determinants of exercise participation patterns, little empirical work that examines efficacy expectations as outcomes of exercise participation or their theoretical relationship to other psychological outcomes associated with exercise has been conducted. In the context of middle-aged males and females, the present study attempted to integrate social cognitive and impression management perspectives with respect to anxiety associated with exercise. METHODS: Formerly sedentary subjects participated in a 5-month exercise program with assessments of physique anxiety, efficacy, outcome expectations, and anthropometric variables prior to and following the program. RESULTS: Both acute bouts and long-term participation in exercise resulted in significant increases in self-efficacy. In turn, these changes in efficacy and initial positive outcome expectations were significant predictors of reductions in physique anxiety, even when controlling for the influence of gender and reductions in body fat, weight, and circumferences. CONCLUSIONS: The findings are discussed in terms of the implications for structure and content of exercise environments and the utility of the proposed theoretical integration. Strategies for enhancing beliefs regarding health and fitness outcomes associated with exercise rather than appearance outcomes may be required to maximize reductions in negative body image.

Anthropometry↗

PubMedDate not supplied

Association of ventricular myosin heavy chains in functional states which lead to isoenzyme populations encompassing the whole range of possible distribution.

A statistical model is presented which describes quantitatively the distribution of ventricular myosin (VM) isoenzymes VM-1, VM-2 and VM-3. In order to account for the actual distribution of the isoenzymes, it was assumed that the probability for formation of the heterodimer VM-2 (alpha- and beta-heavy chain) is lower than that of the homodimers VM-1 (2 alpha-heavy chains) or VM-3 (2 beta-heavy chains). The relation VM-2 = 0.85 (VM-1 X VM-3)0.5 describes quantitatively the proportion of the 3 isoenzymes in a given population. The model was established for 252 sedentary normotensive Wistar rats and spontaneously hypertensive rats (SHR) fed ad libitum. It is demonstrated that the isoenzyme populations of rats subjected to 8 weeks experimental routines involving intermittent feeding (1 day feeding ad libitum, followed by 1 or 2 days fasting) or swimming also obey this theoretical distribution. Intermittent feeding led to an increased proportion of VM-3 in Wistar rats and SHR, whereby the latter approached the limits of the possible distribution. Intermittent swimming resulted in an increased proportion of VM-1 which was independent of the feeding schedule in SHR. In Wistar rats, however, the swimming rats fed intermittently exhibited a significantly smaller proportion of VM-1. By combining certain experimental routines, it is thus possible to induce within 8 weeks an isoenzyme population of a predefined composition, nearly within the whole range of possible distribution.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗

PubMed1992

Did food increase fertility? Evaluation of !Kung and Herero history.

Low fertility among nomadic !Kung foragers of the northern Kalahari Desert of Botswana has been hypothesized to be an adaptation to scarcity of food. However, a comparison of !Kung fertility before and after a transition to a more sedentary lifestyle indicates that more food did not increase fertility. An examination of the fertility of neighboring sedentary Bantu-speaking Herero pastoralists during the same period also indicates that low female reproductive rates in this region are not unique to the !Kung. Herero fertility has increased dramatically in recent decades, probably in response to the control of sexually transmitted diseases in northwestern Botswana. More food appears to have substantially increased !Kung reproductive success by reducing infant and child mortality rates to levels observed among the Herero. These findings suggest that low !Kung fertility and mortality reflect contact with the Herero, who began expanding in large numbers into !Kung territory in the 1950s. This study emphasizes the need for a more rigorous comparative perspective in anthropology to understand better the significance of findings from restricted populations, and I suggest that evolutionary ecology would benefit from shifting some of its current focus on fertility to mortality.

Adolescent↗