The interaction between regular exercise and selected aspects of women's health

No 129-L'exercice physique pendant la grossesse et le postpartum

OBJECTIF

Énoncer une directive canadienne visant à informer les fournisseurs de soins obstétricaux des répercussions, pour la mère, le fœtus et le nouveau-né, des exercices de conditionnement aerobique et musculaire pendant la grossesse. RéSULTATS ATTENDUS: Effets sur la morbidité maternelle, fœtale et néonatale et mesures de la forme physique maternelle.

PREUVES

Une recherche sur MEDLINE des articles, publiés en anglais de 1966 à 2002, appartenant aux catégories suivantes : études sur le conditionnement aérobique et musculaire chez des femmes ne faisant pas jusque-là d'exercice et chez des femmes actives avant leur grossesse, ainsi que des études sur les répercussions du conditionnement aérobique et musculaire sur les issues précoces et tardives de la grossesse ou sur les issues néonatales; rapports de synthèse et méta-analyses portant sur l'exercice pendant la grossesse.

VALEURS

Les résultats recueillis ont été revus par la Société des obstétriciens et gynécologues du Canada (Comité de la pratique clinique - obstétrique), avec la participation de la Société canadienne de physiologie de l'exercice, et ils ont été classés suivant les critères d'évaluation des preuves établis par le Groupe de travail canadien sur l'examen de santé périodique.

RECOMMANDATIONS

VALIDATION: Cette directive a été approuvée par le Comité de pratique clinique - obstétrique de la SOGC, par le Comité exécutif et par le Conseil de la SOGC, ainsi que par le Conseil d'administration de la Société canadienne de physiologie de l'exercice. PARRAINé PAR: la Société des obstétriciens et gynécologues du Canada et par la Société canadienne de physiologie de l'exercice.

A selective review of prenatal exercise guidelines since the 1950s until present: Written for women, health care professionals, and female athletes

BACKGROUND

Traditional society values have long-held the notion that the pregnant woman is construed as a risk to her growing fetus and is solely responsible for controlling this risk to ensure a healthy pregnancy. It is hard to ignore the participation of pregnant women in sport and exercise today, especially in high-level sports and popular fitness programs such as CrossFit™. This challenges both traditional and modern prenatal exercise guidelines from health care professionals and governing health agencies. The guidelines and perceived limitations of prenatal exercise have drastically evolved since the 1950s.

AIM

The goal of this paper is to bring awareness to the idea that much of the information regarding exercise safety during pregnancy is hypersensitive and dated, and the earlier guidelines had no scientific rigor. Research is needed on the upper limits of exercise intensity and exercise frequency, as well as their potential risks (if any) on the woman or fetus.

DISCUSSION

Pregnant women are physically capable of much more than what was once thought. There is still disagreement about the types of exercise deemed appropriate, the stage at which exercise should begin and cease, the frequency of exercise sessions, as well as the optimal level of intensity during prenatal exercise.

CONCLUSION

Research is needed to determine the upper limits of exercise frequency and intensity for pregnant women who are already trained. Healthy women and female athletes can usually maintain their regular training regime once they become pregnant.

Changes in leisure time physical activity during pregnancy compared to the prior year

To quantify changes in leisure time physical activity (LTPA) type, frequency, duration and intensity during the first half of pregnancy as compared with the year prior to pregnancy. A cross sectional study was conducted at the Maternal University Hospital in Granada, Spain. A total of 1,175 healthy pregnant women attending a scheduled visit during the 20-22nd gestational week were enrolled in the study. Information about socio-demographic, obstetric and life-style variables during the previous year and the first half of pregnancy were collected. LTPA was quantified by assigning metabolic equivalents to each activity according to frequency, intensity and duration. The prevalence of women who met the optimal physical activity recommendations before and during pregnancy was calculated, and the McNemar-Bowker symmetry test was used to assess changes in type, frequency, intensity and duration of activities between the two periods. Some sort of LTPA was performed before and during pregnancy by 68.6% of the pregnant women. Respectively, just 27.5% and 19.4% of women fulfilled LTPA recommendations prior to pregnancy and during pregnancy; 12.6% of the women meeting recommendations prior to pregnancy later did not meet those recommendations during gestation, and 4.5% showed the reverse trend. A light increase in walking as a LTPA, and a decrease in the rest of the LTPA type activities, were seen during pregnancy. Some 13.4% of women changed from moderate--the year before- to light LTPA- during pregnancy. Pregnancy involved a decrease in LTPA, not only regarding frequency, but also duration and intensity.

Physiological and metabolic responses of late pregnant women to 40 min of steady-state exercise followed by an oral glucose tolerance perturbation

We examined the physiological and metabolic responses of 24 active late pregnant women to 40 min of vigorous (95% ventilatory threshold) steady-state treadmill exercise followed by a metabolic perturbation [oral glucose tolerance test (OGTT), 75 g] after exercise. Heart rate and respiratory measures were taken throughout exercise, and blood samples were collected during exercise and every 30 min during the 2-h OGTT. Values were compared with those for a group of physically active nonpregnant women ( n = 16) in the luteal phase of the menstrual cycle. Although late pregnant women were heavier, they performed the same work rate (182 vs. 208 W, P > 0.05), with the same oxygen pulse, but responded to the exercise with a blunted heart rate and relative oxygen consumption, with less carbon dioxide expired, possibly due to pregnancy-related adaptations in heart efficiency. Resting glucose concentrations were the same between groups, but by 40 min of exercise (3.8 ± 0.1 vs. 4.6 ± 0.1 mmol/l) and into 15 min of recovery (4.3 ± 0.2 vs. 5.0 ± 0.1 mmol/l), glucose concentrations were diminished in late pregnant women ( P ≤ 0.05, respectively). The pregnancy-induced delay of glucose uptake was seen in response to the postexercise OGTT compared with the nonpregnant women, but insulin sensitivity (ISI) remained (7.4 ± 0.9 vs. 9.7 ± 1.4 ISI, P > 0.05, respectively), with the preservation of the sensitivity of lipolysis inhibition of nonesterified free fatty acids to insulin. These adaptations may be fetoprotective, because our research suggests that 40 min of continuous treadmill exercise is well tolerated by physically active pregnant women. No adverse effects on birth outcome (3.53 ± 0.08 kg birth weight; 39.6 ± 0.33 wk gestational age) were observed.

Maternal exercise and growth in breastfed infants: a meta-analysis of randomized controlled trials

BACKGROUND AND OBJECTIVES

Studies have revealed that women who breastfeed their infants may be reluctant to exercise due to concerns that to do so would adversely affect their breast milk and consequently the growth of their infants. In this review, we seek to systematically review and statistically synthesize evidence from randomized controlled trials (RCTs) that have assessed the effects of maternal exercise on breastfed infant growth (weight gain and gain in length).

METHODS

Searches of the following electronic bibliographic databases were performed to identify RCTs: Cochrane Library (CENTRAL), Medline/PubMed, Embase, Cumulative Index to Nursing and Allied Health Literature, and SPORT Discus. RCTs that compared any type of exercise intervention with other treatments or no treatment in women exclusively or predominately breastfeeding were eligible for inclusion, as were trials involving exercise as a cointervention. Two authors extracted data from studies independently.

RESULTS

Four RCTs (5 comparisons) were included in the meta-analysis of infant weight gain that incorporated 170 participants. In breastfed infants, maternal exercise did not significantly affect infant weight gain (difference in mean weight gain = 18.6 g [95% confidence interval: -113.52 to 150.80, P = .73]). Only 1 trial assessed infant gain in length; no difference between the exercise and control groups was reported. Trials were classified as moderate or good methodological quality (moderate risk of bias).

CONCLUSIONS

It appears that mothers can exercise and breastfeed without detriment to the growth of their infants, but this is based on limited evidence, and more research is required before this finding is confirmed.

Developmental and contextual risks of social physique anxiety among female athletes

In the present study, we examined developmental and contextual factors that may increase the odds of reporting higher social physique anxiety (SPA) among 404 adolescent athletes 11 to 16 years old. Findings showed older, later maturing athletes past peak height velocity and with greater body mass index (BMI) reported higher SPA. Individual aesthetic sport athletes were older at menarche, had lower BMI, and reported higher SPA. The odds of reporting higher SPA were 4.5 times higher (odds ratio = 4.61) for individual aesthetic sport athletes than for nonaesthetic sport athletes. Team aesthetic sport contexts were not implicated in SPA risk. Results are discussed in terms of self-selection away from individual aesthetic sports and the relevance of physical size and puberty in the SPA construct.

Aerobic exercise during pregnancy improves health-related quality of life: a randomised trial

QUESTION

Does supervised aerobic exercise during pregnancy improve health-related quality of life in nulliparous women?

DESIGN

Analysis of secondary outcomes of a randomised trial with concealed allocation, blinded assessors, and intention-to-treat analysis.

PARTICIPANTS

64 nulliparous, pregnant women attending for prenatal care at one of three tertiary hospitals.

INTERVENTION

The experimental group completed a 3-month supervised exercise program, commencing at 16 to 20 weeks of gestation. Each session included walking (10 min), aerobic exercise (30 min), stretching (10 min), and relaxation (10 min). The control group continued usual activities and performed no specific exercise.

OUTCOME MEASURES

The primary outcome was health-related quality of life assessed by the Colombian version of the Medical Outcome Study Short-Form Health Survey at baseline and immediately after the 3-month intervention.

RESULTS

Fifty women completed the study. After the 3-month intervention, the experimental group had improved their health-related quality of life more than the control group in the physical component summary of the questionnaire by 6 points (95% CI 2 to 11), the physical function domain (7 points, 95% CI 0 to 14), the bodily pain domain (7 points, 95% CI 1 to 13) and the general health domain (5 points, 95% CI 1 to 10).

CONCLUSIONS

A supervised 3-month program of primarily aerobic exercise during pregnancy improves health-related quality of life.

TRIAL REGISTRATION

NCT00741312.

Clinical trial to assess the effect of physical exercise on endothelial function and insulin resistance in pregnant women

Background

Preeclampsia (PE) is a common maternal disease that complicates 5 to 10% of pregnancies and remains as the major cause of maternal and neonatal mortality. Cost-effective interventions aimed at preventing the development of preeclampsia are urgently needed. However, the pathogenesis of PE is not well known. Multiple mechanisms such as oxidative stress, endothelial dysfunction and insulin resistance may contribute to its development. Regular aerobic exercise recovers endothelial function; improves insulin resistance and decreases oxidative stress. Therefore the purpose of this clinical trial is to determine the effect of regular aerobic exercise on endothelial function, on insulin resistance and on pregnancy outcome.

Methods and design

64 pregnant women will be included in a blind, randomized clinical trial, and parallel assignment. The exercise group will do regular aerobic physical exercise: walking (10 minutes), aerobic exercise (30 minutes), stretching (10 minutes) and relaxation exercise (10 minutes) in three sessions per week. Control group will do the activities of daily living (bathing, dressing, eating, and walking) without counselling from a physical therapist.

Trial registration

NCT00741312.

Breast-feeding mothers can exercise: results of a cohort study

Objectives

To study the relationship between exercise by the mother and breast-feeding initiation and duration, and its effect on infant growth.

Design

A cohort study of mothers and infants, recruited at birth. Infant feeding methods were recorded in detail and breast-feeding was categorised as ‘any’ or ‘full’. Exercise levels were categorised using the metabolic equivalent tasks approach based on details of physical activity recorded in questionnaires.

Setting

Perth, Western Australia.

Subjects

A total of 587 mothers were interviewed on seven occasions over a period of 12 months.

Results

There was no difference in the means of infant weight and length changes, indicating that exercise appeared to have no significant influence on infant growth up to 52 weeks after birth (P = 0.236 and 0.974, respectively). The mother's level of exercise was not significantly associated with breast-feeding to 6 or 12 months. This applied to ‘full’ and ‘any’ categories of breast-feeding.

Conclusion

Exercise does not affect breast-feeding outcomes at the usual levels of activity undertaken by mothers. Breast-feeding and exercise are important for maintaining and promoting health, and this study provides reassurance to health professionals wishing to encourage mothers to continue both behaviours.

Musculoskeletal aspects of pregnancy

Sex-specific care of musculoskeletal impairments is an increasingly important topic in women's health. This is clinically relevant and of paramount importance as it pertains to diagnosis and treatment of musculoskeletal and peripheral neurologic disorders of pregnancy and the puerperium. It is estimated that virtually all women experience some degree of musculoskeletal discomfort during pregnancy, and 25% have at least temporarily disabling symptoms. This review provides information on common pregnancy-related musculoskeletal conditions, including a discussion of anatomy and physiology, diagnosis, prognosis, and treatment of these disorders.

Fetal heart rate and uterine contraction during automobile driving

OBJECTIVE

The purpose of this study was to clarify the influence of automobile driving in the third trimester of pregnancy on fetal heart rate and uterine contraction.

METHODS

Twenty-nine pregnant women with singleton pregnancies after 28 weeks of gestation were monitored using a portable cardiotocogram during driving, and the results obtained before and after driving were compared.

RESULTS

Baseline fetal heart rate and its variability, as well as periodic fetal heart rate patterns, showed no abnormal patterns during car driving. Automobile driving in late pregnancy was not a reinforcement factor for uterine activity. Maternal systolic and diastolic blood pressure and heart rate showed no specific characteristic or adverse change during driving.

CONCLUSION

The results of this study suggest that automobile driving in the third trimester of pregnancy has no adverse influences on either pregnant women or fetuses.

Joint SOGC/CSEP Clinical Practice Guideline: Exercise in Pregnancy and the Postpartum Period

Objective: To design Canadian guidelines advising obstetric care providers of the maternal, fetal, and neonatal implications of aerobic and strength-conditioning exercises in pregnancy. Outcomes: Knowledge of the impact of exercise on maternal, fetal, and neonatal morbidity, and of the maternal measures of fitness. Evidence: MEDLINE search from 1966 to 2002 for English-language articles related to studies of maternal aerobic and strength conditioning in a previously sedentary population, maternal aerobic and strength conditioning in a previously active population, impact of aerobic and strength conditioning on early and late pregnancy outcomes, impact of aerobic and strength conditioning on neonatal outcomes, as well as for review articles and meta-analyses related to exercise in pregnancy. Values: The evidence collected was reviewed by the Society of Obstetricians and Gynaecologists of Canada (SOGC Clinical Practice Obstetrics Committee) with representation from the Canadian Society for Exercise Physiology, and quantified using the evaluation of evidence guidelines developed by the Canadian Task Force on the Periodic Health Exam.Recommendations:1. All women without contraindications should be encouraged to participate in aerobic and strength-conditioning exercises as part of a healthy lifestyle during their pregnancy. (II-1,2B)2. Reasonable goals of aerobic conditioning in pregnancy should be to maintain a good fitness level throughout pregnancy without trying to reach peak fitness or train for an athletic competition. (II-1,2C)3. Women should choose activities that will minimize the risk of loss of balance and fetal trauma. (III-C)4. Women should be advised that adverse pregnancy or neonatal outcomes are not increased for exercising women. (II-1,2B)5. Initiation of pelvic floor exercises in the immediate postpartum period may reduce the risk of future urinary incontinence. (II-1C)6. Women should be advised that moderate exercise during lactation does not affect the quantity or composition of breast milk or impact infant growth. (I-A)Validation: This guideline has been approved by the SOGC Clinical Practice Obstetrics Committee, the Executive and Council of SOGC, and the Board of Directors of the Canadian Society for Exercise Physiology. Sponsors: This guideline has been jointly sponsored by the Society of Obstetricians and Gynaecologists of Canada and the Canadian Society for Exercise Physiology. Key words: fetus, neonate, outcomes, aerobic, strength

Exercise in pregnancy and the postpartum period

OBJECTIVE

To design Canadian guidelines advising obstetric care providers of the maternal, fetal, and neonatal implications of aerobic and strength-conditioning exercises in pregnancy.

OUTCOMES

Knowledge of the impact of exercise on maternal, fetal, and neonatal morbidity, and of the maternal measures of fitness.

EVIDENCE

MEDLINE search from 1966 to 2002 for English-language articles related to studies of maternal aerobic and strength conditioning in a previously sedentary population, maternal aerobic and strength conditioning in a previously active population, impact of aerobic and strength conditioning on early and late pregnancy outcomes, and impact of aerobic and strength conditioning on neonatal outcomes, as well as for review articles and meta-analyses related to exercise in pregnancy.

VALUES

The evidence collected was reviewed by the Society of Obstetricians and Gynaecologists of Canada (SOGC Clinical Practice Obstetrics Committee) with representation from the Canadian Society for Exercise Physiology, and quantified using the evaluation of evidence guidelines developed by the Canadian Task Force on the Periodic Health Exam.

RECOMMENDATIONS

1. All women without contraindications should be encouraged to participate in aerobic and strength-conditioning exercises as part of a healthy lifestyle during their pregnancy. (II-1,2B) 2. Reasonable goals of aerobic conditioning in pregnancy should be to maintain a good fitness level throughout pregnancy without trying to reach peak fitness or train for an athletic competition. (II-1,2C) 3. Women should choose activities that will minimize the risk of loss of balance and fetal trauma. (III-C) 4. Women should be advised that adverse pregnancy or neonatal outcomes are not increased for exercising women. (II-1,2B) 5. Initiation of pelvic floor exercises in the immediate postpartum period may reduce the risk of future urinary incontinence. (II-1C) 6. Women should be advised that moderate exercise during lactation does not affect the quantity or composition of breast milk or impact infant growth. (I-A) VALIDATION: This guideline has been approved by the SOGC Clinical Practice Obstetrics Committee, the Executive and Council of SOGC, and the Board of Directors of the Canadian Society for Exercise Physiology.

SPONSORS

This guideline has been jointly sponsored by the Society of Obstetricians and Gynaecologists of Canada and the Canadian Society for Exercise Physiology.

Infant acceptance of breast milk after maternal exercise

OBJECTIVE

Previous research reported that breast milk lactic acid (LA) levels increase after lactating women complete a bout of exhaustive exercise, resulting in poor infant acceptance of the postexercise breast milk. This highly publicized finding may not apply to more practical, everyday exercise conditions of lactating women. The purpose of the present study was to reexamine the composition and infant acceptance of postexercise breast milk while controlling maternal diet, exercise intensity, and the method, timing, and assessment of infant feeding.

RESEARCH DESIGN AND METHODS

Twenty-four women, 2 to 4 months' postpartum, completed 3 test sessions: a maximal oxygen uptake test, a 30-minute bout of moderate exercise, and a resting control session. One hour before and 1 hour after each session, participants fully expressed their milk, placed it in a bottle familiar to the infant, fed their infant, and rated their infant's acceptance of the milk. Each feeding was videotaped and viewed individually by 3 lactation consultants who rated infant acceptance; consultants were blinded to the test sessions. Milk was analyzed for LA and infant milk consumption was measured.

RESULTS

There were no differences in presession versus postsession values for maternal skin temperature, breast milk temperature, and infant milk acceptance as judged by either the mothers or lactation consultants. These results prevailed despite a small but significant increase in breast milk LA premaximal versus postmaximal exercise (0.09 vs 0.21 mM, respectively); there was no difference in milk LA premoderate versus postmoderate exercise, or prerest versus postrest.

CONCLUSION

These data support the hypothesis that moderate or even high-intensity exercise during lactation does not impede infant acceptance of breast milk consumed 1 hour postexercise.

Leisure time physical activity in Australian women: relationship with well being and symptoms

This paper explores the association between moderate levels of physical activity (PA) and health benefits in well being and symptoms such as tiredness, back pain, and constipation. Participants in the Australian Longitudinal Study on Women's Health, 14,502 young women (ages 18-23 years), 13,609 middle-age women (45-50 years), and 11,421 older women (ages 70-75 years), answered questions about vigorous and less vigorous exercise (used to determine a physical activity score), well being (SF-36), symptoms, and medical conditions. There were significant associations between the PA score and SF-36 in each cohort. Odds ratios (OR) for a range of symptoms and conditions were lower for women who reported low to moderate activity than for sedentary women, for example, for young women or for constipation = 0.76 (CI, 0.65-0.89), for middle-age women or for tiredness = 0.70 (0.63-0.78). There was no threshold of PA at which health benefits increased significantly. Although cross-sectional, the findings suggest that low-to-moderate levels of exercise are associated with a range of health benefits for women of all ages. These preliminary findings will be followed up during the longitudinal study.

A lifetime of fitness. Exercise in the perimenopausal and postmenopausal woman

The peri- and postmenopausal woman experiences physiologic changes of aging that include alterations in hormone levels. Research has shown that the perimenopausal and postmenopausal woman can benefit significantly from exercise, whether endurance or strength training. Exercise can improve the quality of life and attenuate some of the physiologic changes associated with aging. Additionally, exercise can ameliorate the decline in fitness and bone, prevent chronic disease, and promote functional independence. Women who exercise regularly throughout life are physiologically 20 to 30 years younger than their sedentary counterparts. Fitness is a lifetime endeavor that has many positive benefits. Weightbearing activities are especially important as bone loss increases in the perimenopausal phase of life. Women should perform aerobic exercise 3 to 7 days per week for 15 to 60 minutes at 65% to 70% HRreserve. Strengthening exercises should be done 2 to 3 days per week at 40% to 80% 1RM with appropriately selected exercises. An exercise program should be functional and enjoyable. There is no better motivation to exercise than having a partner to work out with and keep the motivation alive. Most important, age itself is not a deterrent to exercise.

Exercise during the childbearing year

Many women wish to continue to pursue an active lifestyle during pregnancy, while the pregnancy itself may provide the motivation for other more sedentary women to begin an exercise program for the sake of improved health/fitness. Also, female competitive athletes, upon becoming pregnant, may wish to continue sports performance and require careful monitoring to assure maternal-fetal safety. This review is designed to assist the perinatal educator who is in the position to advise the pregnant patient on the risks and benefits of physical activity during the childbearing year and provide suggestions for developing individualized exercise programs.

Development and evaluation of a pilot program to promote exercise among mothers of preschool children

The health benefits of physical activity are well documented, but mothers of young children experience significant barriers to exercise. A 10-week minimal-intervention exercise program, involving a weekly meeting at which child care was provided, and guidance in establishing independent exercise was developed on the basis of previous research with this population group. Thirty-two women with children under age 5, and in the contemplation or preparation stages of exercise behavior change, were recruited from Australian play groups. Postprogram measures showed small but significant decreases in body mass index, resting heart rate, and diastolic blood pressure. Three months later, 41% of participants were still active. Family-related constraints were highly disruptive to these participants. This study is limited by its small sample size, lack of controls, and potential biases in recruitment and assessment, but it does suggest that hard-to-reach groups, such as mothers of young children, may be mobilized to exercise if programs explicitly address social contexts and the constraints on individual choice.

Maternal physical activity in pregnancy and infant size for gestational age

PURPOSE

To estimate the effect of several types of maternal physical activity in pregnancy on size for gestational age and length of gestation.

METHODS

Telephone interviews, birth certificates, and medical records provided data on physical activity and other factors for a random sample of 291 Colorado residents. Backward polychotomous logistic regression modeling yielded estimates of the odds ratios for size for gestational age (appropriate versus small or large) and length of gestation (term versus pre-term or post-term) in relation to second and third trimester maternal physical activity.

RESULTS

Performance of any moderate or vigorous physical activity for two hours per week or more in any month was associated with a decreased risk of large infant size for gestational age (LGA; odds ratio = 0.3, 95% confidence interval = 0.2, 0.7), but had no significant effect on risk of small infant size for gestational age (SGA; odds ratio (OR) = 0.8, 95% confidence interval (CI) = 0.3, 2.3). Length of gestation was not affected by prenatal physical activity.

CONCLUSIONS

These results suggest that prenatal physical activity may decrease risk of LGA, as might be expected given its salutary effects on glucose tolerance.

Self-selected recreational exercise has no impact on early postpartum lactation-induced bone loss

Although exercise is known to positively impact bone mineral density (BMD), its effect on lactation-induced BMD loss has not been previously evaluated in a case-control study.

PURPOSE

The purpose of this study was to compare lactation-induced bone changes in women who engaged in regular, self-selected, recreational exercise versus those who refrained from such during early postpartum.

METHODS

Subjects were 20 healthy, lactating women who either exercised regularly (exercise, E; N = 11) or refrained from such (control, C; N = 9) during the first 3 months postpartum. Although preconception VO2max was significantly higher in E than C (E = 54.1, C = 36.9 mL.min-1.kg-1), no significant group differences were observed for parity, age, height, weight (WT), % body fat, dietary calcium intake, lactation calcium loss, and serum estradiol. Total body (TB), lumbar spine (LS), and femur neck (FN) BMD were measured within 2 wk of parturition and repeated at 3 months postpartum by dual energy x-ray absorptiometry.

RESULTS

Although TB was unchanged, BMD decreased significantly from baseline in both groups at LS (C = -5.4, E = -4.1%) and FN (C = -2.7, E = -2.8%). WT decreased significantly over time but was not significantly correlated with BMD loss. No significant group by time interactions were observed for WT or BMD changes.

CONCLUSION

These results suggest that regular, self-selected, recreational E has no impact on early postpartum lactation-induced BMD loss.

Breast milk composition after exercise of different intensities

The purpose of this study was to determine if breast milk composition changed significantly following exercise conducted at different intensities. Nine postpartum women exercised on a treadmill up to maximal oxygen uptake (100% of VO2max) on the first laboratory visit, for 30 minutes on two subsequent occasions (50% and 75% of VO2max) and also performed a nonexercise control session. Blood and breast milk were collected prior to exercise, immediately after exercise, and at 30, 60, and 90 minutes postexercise. Blood samples were analyzed for lactic acid (LA) while milk samples were analyzed for LA, pH, lipid, ammonium, and urea. Milk LA after the 100% intensity session was significantly elevated through 90 minutes postexercise, while there was no significant increase in milk LA at any collection time after the 50% or 75% intensity sessions. There were no significant differences in milk pH, lipid, ammonium, or urea measurements after any of the exercise sessions. These data show that unlike maximum intensity exercise, moderate intensity exercise does not increase breast milk LA content.

Applications of methods and techniques in the study of aerobic fitness during pregnancy

This article is a critical review of the general principles of exercise physiology and their relevance in pregnancy. An overview of the published studies and their conclusions are provided.