The duration of lactational amenorrhoea in urban Bangladeshi women

The duration of lactational amenorrhoea, and infant feeding patterns and behaviour, were investigated in a sample of 97 mother-infant pairs living in a poor urban area of Dhaka, Bangladesh. A seven-hour time allocation method was used to determine the number of breast-feeding bouts and their duration. The seven-hour observation period was conducted on five occasions: at birth, 1 month, 4 months, 8 months and either 10 or 11 months. The median duration of lactational amenorrhoea was determined to be 24.07 weeks using survival analysis. Mothers who breast-fed their babies for longer and more frequently had, on average, a longer period of lactational amenorrhoea. There was no relationship between sociodemographic characteristics of the mother and duration of lactational amenorrhoea, nor was there any significant relationship between maternal anthropometry and birth weight of the baby and duration of lactational amenorrhoea, but there was a tendency for women with lower body mass index to have longer durations. Using the Cox proportional hazards model, the best predictor of duration of lactational amenorrhoea was the mean of months 0 and 1 durations of breast-feeding, adjusted for the mean frequencies for those months. The introduction of weaning food was also an important predictor.     

Daily energy expenditure of singing great reed warblers Acrocephalus arundinaceus

According to honest signalling theory, signals must be costly to produce to retain information about the signaller's quality. The song produced by male birds during breeding is a vocal "ornament" used for intra- and inter-sexual purposes. The energetic cost of this vocal signal remains a contentious issue. We used the doubly labelled water method to measure field metabolic rate by estimating CO₂ production and then convert this to daily energy expenditure (DEE) in great reed warbler males singing under natural conditions (10 at low to moderate intensity and 7 at very high intensity from dawn to dusk). There was a significant positive relationship between singing intensity and DEE. From this relationship we extrapolated the average DEE for intensely singing males (i.e., males producing song sounds 50% of the time and hence sitting at their elevated song post in the top of a reed stem more or less continuously throughout the ∼20 h of daylight) to 3.3×BMR (basal metabolic rate) and for non-singing males to 2.2×BMR. The mean DEE measured for the seven males singing with very high intensity was 3.1×BMR. The maximum measured DEE for a single male was 3.9×BMR, i.e. close to the maximum sustainable DEE (4×BMR), and the minimum DEE was 2.1×BMR for a male singing at very low intensity. These results imply that producing intensive advertising song in birds may incur a substantial cost in terms of increased energy expenditure.     

Daily energy expenditure in active and inactive persons with spinal cord injury.

Daily energy expenditure (DEE) was evaluated seventeen male subjects with spinal cord injury (SSCI), who had active (N = 9) and inactive (N = 8) lifestyles, and in seven normal males. DEE was estimated from the mean 24-hr heart rate and heart rate-energy expenditure relationship determined in an arm cranking exercise. The DEE of SSCI on active days did not differ from those of normal subjects. On inactive days, SSCI had significantly lower DEE than on active days and than normal subjects. In contrast, the mean 24-hr heart rates of SSCI on active days and inactive SSCI were significantly greater than those of normal subjects, suggesting that SSCI, particularly inactive SSCI, exhibited a slight degree of tachycardia when compared to normal subjects. On inactive days, the DEE was fairly independent of the level of spinal cord injury. However, on active days, there was a clear tendency for SSCI with a low lesion level to have a higher DEE. Even if a SSCI with a high lesion level engaged in active sports, his DEE was relatively small. This lower DEE was largely attributable to the smaller functional muscle mass due to the limitation of physical activity.     

High-level medium-chain triglyceride feeding and energy expenditure in normal-weight women

The objective of this study was to assess how short-term feeding of high levels of dietary medium-chain triglyceride (MCT) affect energy expenditure and postprandial substrate oxidation rates in normal-weight, premenopausal women. Eight healthy women were fed both a MCT-rich and an isocaloric long-chain triglyceride (LCT)-rich diet for two 1-week periods separated by a minimum of 21 days. The energy intake in each diet was 45% carbohydrates, 40% fat, and 15% protein. The 2 diets had either 60.81% or 1.11% of total fat energy from MCT with the remaining fat energy intake from LCT. On days 1 and 7 of each diet, resting metabolic rate and postprandial energy expenditure (EE) were measured by indirect calorimetry with a ventilated hood. Results indicated on days 1 and 7, there were no significant differences between diets for resting metabolic rate or mean postprandial EE. On both days 1 and 7, fat oxidation for the MCT-rich diet was significantly greater (0.0001 相似文献   

Daily energy expenditure of male barn swallows correlates with tail-streamer length: handicap-mediated foraging strategies

Daily energy expenditure (DEE) of male barn swallows (Hirundo rustica), measured using the doubly labelled water technique, correlated with streamer length. Contrary to predictions derived from previous findings, neither a positive linear nor a u-shaped relationship was found between DEE and streamer length. Instead, an n-shaped curve showed that the highest DEE corresponded to an intermediate streamer length of 119 mm. A model incorporating estimates of resting metabolism and flight energy expenditure from aerodynamics models suggested that variation in individual tail dynamics was the most likely explanation for the observed DEE. We suggest that streamer length is coupled to foraging strategy, because tail dynamics control flight performance, which in turn influences flight behaviour.     

Daily energy expenditure and cell-mediated immunity in pied flycatchers while feeding nestlings: interaction with moult

Ecological immunology posits a trade-off between parental effort and immunocompetence underlying the cost of reproduction. The moult-breeding overlap observed in several bird species represents a conflict in resource allocation between two energy-demanding processes. Moult processes have been associated with enlargements of immune system organs. In the present study. we measured simultaneously daily energy expenditure (DEE) and the T-cell-dependent immune response of pied flycatchers, Ficedula hypoleuca, caring for grown nestlings. We used the doubly labelled water technique and the phytohaemagglutinin (PHA) injection assay on both males and females, while recording provisioning rates and moult scores. DEE and the PHA response were negatively correlated for females, but not for males. A significantly higher proportion of males than females initiated moult. Provisioning rates were strongly correlated with DEE for females but only for non-moulting males. The DEE of moulting males was marginally correlated with moult score. For moulting males, there was a marginally significant positive correlation between moult score and immune response. The trade-off between DEE and immunity for females could underlie the cost of reproduction. However, the moult-breeding overlap found in males may offset this trade-off, thereby reducing the implications of immunosuppression for parental survival.     

Daily energy expenditure of the grey mouse lemur (Microcebus murinus): a small primate that uses torpor

We aimed to investigate the pattern of utilisation of torpor and its impact on energy budgets in free-living grey mouse lemurs (Microcebus murinus), a small nocturnal primate endemic to Madagascar. We measured daily energy expenditure (DEE) and water turnover using doubly labelled water, and we used temperature-sensitive radio collars to measure skin temperature (T _sk) and home range. Our results showed that male and female mouse lemurs in the wild enter torpor spontaneously over a wide range of ambient temperatures (T _a) during the dry season, but not during the rainy season. Mouse lemurs remained torpid between 1.7–8.9 h with a daily mean of 3.4 h, and their T _sk s fell to a minimum of 18.8 °C. Mean home ranges of mouse lemurs which remained normothermic were similar in the rainy and dry season. During the dry season, the mean home range of mouse lemurs showing daily torpor was significantly smaller than that of animals remaining normothermic. The DEE of M. murinus remaining normothermic in the rainy season (122 ± 65.4 kJ day⁻¹) was about the same of that of normothermic mouse lemurs in the dry season (115.5 ± 27.3 kJ day⁻¹). During the dry season, the mean DEE of M. murinus that utilised daily torpor was 103.4 ± 32.7 kJ day⁻¹ which is not significantly different from the mean DEE of animals remaining normothermic. We found that the DEE of mouse lemurs using daily torpor was significantly correlated with the mean temperature difference between T _sk and T _a (r ²=0.37) and with torpor bout length (r ² =0.46), while none of these factors explained significant amounts of variation in the DEE of the mouse lemurs remaining normothermic. The mean water flux rate of mouse lemurs using daily torpor (13.0 ± 4.1 ml day⁻¹) was significantly lower than that of mouse lemurs remaining normothermic (19.4 ± 3.8 ml day⁻¹), suggesting the lemurs conserve water by entering torpor. Thus, this first study on the energy budget of free-ranging M. murinus demonstrates that torpor may not only reflect its impact on the daily energy demands, but involve wider adaptive implications such as water requirements. Accepted: 29 August 2000     

Resumption of menstruation among urban post-partum women in Bangladesh.

To investigate the return of menstruation among postpartum women in Dacca, a random sample of 360 women (1-12 months postpartum) was selected from 4 Dacca hospitals for a cross-sectional study; another random sample of 200 women ( 1 month postpartum at time of interview) was selected from the same hospitals for prospective follow up. Many of the women were from rural areas who left the city after delivering their babies; most were under 25 years old at the time of interview. Results of the cross sectional study showed that 63% started menstruating by the 6th postpartum month; 10% were still amenorrhoeic by the 12th postpartum month; 46% were breastfeeding their infants by the 4th month; 90% resumed sexual relations, and 48% were using contraceptives, by the 6th month. Results of the prospective study showed that slightly more than half of the women started menstruating by the end of the 5th postpartum month; almost half stopped breastfeeding by the 5th month, 88.8% were having sexual relations with their husbands, and about 50.5% were on some form of birth control. The findings suggest a much shorter duration of lactational amenorrhea than has been claimed for a rural area of Bangladesh; they also suggest that urban women start menstruating earlier because of their primary reliance on supplementary feeding. The contraceptive effectiveness, as well as health benefits to infants, of prolonged and intensive lactation should be promoted to urban mothers.     

Estimation of daily energy expenditure in pregnant and non-pregnant women using a wrist-worn tri-axial accelerometer

Background

Few studies have compared the validity of objective measures of physical activity energy expenditure (PAEE) in pregnant and non-pregnant women. PAEE is commonly estimated with accelerometers attached to the hip or waist, but little is known about the validity and participant acceptability of wrist attachment. The objectives of the current study were to assess the validity of a simple summary measure derived from a wrist-worn accelerometer (GENEA, Unilever Discover, UK) to estimate PAEE in pregnant and non-pregnant women, and to evaluate participant acceptability.

Methods

Non-pregnant (N = 73) and pregnant (N = 35) Swedish women (aged 20–35 yrs) wore the accelerometer on their wrist for 10 days during which total energy expenditure (TEE) was assessed using doubly-labelled water. PAEE was calculated as 0.9×TEE-REE. British participants (N = 99; aged 22–65 yrs) wore accelerometers on their non-dominant wrist and hip for seven days and were asked to score the acceptability of monitor placement (scored 1 [least] through 10 [most] acceptable).

Results

There was no significant correlation between body weight and PAEE. In non-pregnant women, acceleration explained 24% of the variation in PAEE, which decreased to 19% in leave-one-out cross-validation. In pregnant women, acceleration explained 11% of the variation in PAEE, which was not significant in leave-one-out cross-validation. Median (IQR) acceptability of wrist and hip placement was 9(8–10) and 9(7–10), respectively; there was a within-individual difference of 0.47 (p<.001).

Conclusions

A simple summary measure derived from a wrist-worn tri-axial accelerometer adds significantly to the prediction of energy expenditure in non-pregnant women and is scored acceptable by participants.     

An energy 'sources' and 'fractions' approach to the mechanical energy expenditure problem--III. Mechanical energy expenditure reduction during one link motion

Mechanical energy economy and transformation during one link motion are analyzed on the basis of the theory developed in the previous publications (parts I and II of this series, J. Biomechanics 19, 287-300). The 'compensation coefficient' characterizing mechanical energy economy is introduced. The attempts to estimate MEE using only energy curves and neglecting the powers of real sources of energy implicitly lead to replacement of real force and moment systems by the systems reduced to the centers of mass. But such an unintentional substitution of imaginary sources for real ones, specifically, the reduction of forces acting on the link to the equivalent system, changes estimates of mechanical energy expenditure (MEE). That is why the methods of calculating MEE economy based on the determination of so-called 'quasi-mechanical' work (the sum of the kinetic and potential energy increases per one cycle of motion) are not correct. There are two mechanisms to reduce the MEE using the antiphase fluctuations (corresponding to energy transformations) of the (a) rotational and translational fractions of the total energy (at the expense of the F-sources); (b) potential and kinetic energies (at the expense of the mg-source).     

Role behaviours among urban women as revealed by time allocation

The present study, conducted among 190 urban middle-class women of Calcutta city, examines the differences between a group of working mothers and a socioeconomically comparable group of non-working mothers with respect to their time use pattern. The underlying hypotheses are: (a) working mothers have less time for certain household responsibilities compared to non-working mothers; and (b) combined job and family responsibilities generate role conflicts among the working mothers, due to lack of support in the family and/or outside it. Results suggest that though the working mothers had contributed significantly less time in parental, domestic, conjugal and individual activities compared to their non-working counterparts, they hardly faced role conflicts as corroborated from their lower anxiety scores.     

Marital coitus across the life course

It remains unclear whether the frequency of marital coitus does in fact decline universally across the life course, what shape that decay normally takes, and what best accounts for it: increasing marriage duration, women's age or age of their partners. Using cross-sectional Demographic and Health Survey (DHS) data of 91,744 non-abstaining women in their first marriage, a generalized linear model is used to determine if there is a consistent pattern in the life course pattern of degradation in the frequency of marital coitus. Datasets were drawn from nineteen countries in Asia, Africa and the Americas. Use of very large samples allows proper disentangling of the effects of women's age, husband's age and marital duration, and use of samples from multiple countries allows consideration of the influence of varied prevailing fertility regimes and fertility-related practices on life course trajectories. It is found that declining coital frequency over time seems a shared demographic feature of human populations, but whether marriage duration, wife's age or husband's age is most responsible for that decline varies by country. In many cases, coital frequency actually increases with women's age into their thirties, once husband's age and marriage duration are taken into account, but in most cases coital frequency declines with husband's age and marital duration.     

An energy 'sources' and 'fractions' approach to the mechanical energy expenditure problem--V. The mechanical energy expenditure reduction during motion of the multi-link system

Mechanical energy economy during motion of the multi-link system is analyzed on the basis of the theory developed in the previous publications (parts I-IV of this series, J. Biomechanics 19, 287-309). The compensation coefficients for the F- and M-sources and also the absolute compensation coefficient reflecting the mechanical energy economy due to four possible resources are introduced. These resources are the antiphase fluctuations of (I) each link's total energy fractions involving energy transformations between (1) rotational and translational fractions by F-sources, (2) kinetic and potential fractions by mg-source; (II) the links' total energies involving energy transfers between (3) links by F-sources, (4) links by M-sources. The conditions of mechanical energy economy, particularly due to M-sources, are analyzed.     

Effects of mental stress on insulin-mediated glucose metabolism and energy expenditure in lean and obese women

The effects of the sympathetic activation elicited by a mental stress on insulin sensitivity and energy expenditure (VO(2)) were studied in 11 lean and 8 obese women during a hyperinsulinemic-euglycemic clamp. Six lean women were restudied under nonselective beta-adrenergic blockade with propranolol to determine the role of beta-adrenoceptors in the metabolic response to mental stress. In lean women, mental stress increased VO(2) by 20%, whole body glucose utilization ([6,6-(2)H(2)]glucose) by 34%, and cardiac index (thoracic bioimpedance) by 25%, whereas systemic vascular resistance decreased by 24%. In obese women, mental stress increased energy expenditure as in lean subjects, but it neither stimulated glucose uptake nor decreased systemic vascular resistance. In the six lean women who were restudied under propranolol, the rise in VO(2), glucose uptake, and cardiac output and the decrease in systemic vascular resistance during mental stress were all abolished. It is concluded that 1) in lean subjects, mental stress stimulates glucose uptake and energy expenditure and produces vasodilation; activation of beta-adrenoceptors is involved in these responses; and 2) in obese patients, the effects of mental stress on glucose uptake and systemic vascular resistance, but not on energy expenditure, are blunted.     

Restriction of energy intake, energy expenditure, and aging

Energy restriction (ER), without malnutrition, increases maximum life span and retards the development of a broad array of pathophysiological changes in laboratory rodents. The mechanism responsible for the retardation of aging by ER is, however, unknown. One proposed explanation is a reduction in energy expenditure (EE). Reduced EE may increase life span by decreasing the number of oxygen molecules interacting with mitochondria, thereby lowering reactive oxygen species (ROS) production. As a step toward testing this hypothesis, it is important to determine the effect of ER on EE. Several whole-body, organ, and cellular studies have measured the influence of ER on EE. In general, whole-body studies have reported an acute decrease in mass-adjusted EE that disappears with long-term ER. Organ-specific studies have shown that decreases in EE of liver and gastrointestinal tract are primarily responsible for initial reductions in EE with ER. These data, however, do not determine whether cellular EE is altered with ER. Three major processes contributing to resting EE at the cellular level are mitochondrial proton leak, Na(+)-K(+)-ATPase activity, and protein turnover. Studies suggest that proton leak and Na(+)-K(+)-ATPase activity are decreased with ER, whereas protein turnover is either unchanged or slightly increased with ER. Thus, two of the three major processes contributing to resting EE at the cellular level may be decreased with ER. Although additional cellular measurements are needed, the current results suggest that a lowering of EE could be a mechanism for the action of ER.     

A model of human muscle energy expenditure

A model of muscle energy expenditure was developed for predicting thermal, as well as mechanical energy liberation during simulated muscle contractions. The model was designed to yield energy (heat and work) rate predictions appropriate for human skeletal muscle contracting at normal body temperature. The basic form of the present model is similar to many previous models of muscle energy expenditure, but parameter values were based almost entirely on mammalian muscle data, with preference given to human data where possible. Nonlinear phenomena associated with submaximal activation were also incorporated. The muscle energy model was evaluated at varying levels of complexity, ranging from simulated contractions of isolated muscle, to simulations of whole body locomotion. In all cases, acceptable agreement was found between simulated and experimental energy liberation. The present model should be useful in future studies of the energetics of human movement using forward dynamic computer simulation.     

Analytical description of minimum energy expenditure surfaces

Mechanical energy expenditure during level walking was evaluated and graphed for two unilateral, below-knee amputees over time and a range of adjustments of the flexion-extension alignment angle. The resulting mechanical energy surfaces were then least-squared fitted with an analytical function that was linear in time and quadratic in flexion-extension alignment angle. The least-squares analysis showed that there was a flexion-extension adjustment that minimized the mechanical energy expenditure and that this optimal adjustment was very close to the design point set by certified prosthetists.