Katarina Melzer

Physical activity and pregnancy: cardiovascular adaptations, recommendations and pregnancy outcomes.

Regular physical activity is associated with improved physiological, metabolic and psychological parameters, and with reduced risk of morbidity and mortality. Current recommendations aimed at improving the health and wellbeing of nonpregnant subjects advise that an accumulation of ≥30 minutes of moderate physical activity should occur on most, if not all, days of the week.Regardless of the specific physiological changes induced by pregnancy, which are primarily developed to meet the increased metabolic demands of mother and fetus, pregnant women benefit from regular physical activity the same way as nonpregnant subjects.Changes in submaximal oxygen uptake (V̇O2) during pregnancy depend on the type of exercise performed. During maternal rest or submaximal weight-bearing exercise (e.g. walking, stepping, treadmill exercise), absolute maternal V̇O2 is significantly increased compared with the nonpregnant state. The magnitude of change is approximately proportional to maternal weight gain.When pregnant women perform submaximal weight-supported exercise on land (e.g. level cycling), the findings are contradictory. Some studies reported significantly increased absolute V̇O2, while many others reported unchanged or only slightly increased absolute V̇O2 compared with the nonpregnant state. The latter findings may be explained by the fact that the metabolic demand of cycle exercise is largely independent of the maternal body mass, resulting in no absolute V̇O2 alteration.Few studies that directly measured changes in maternal maximal V̇O2 (V̇O2max) showed no difference in the absolute V̇O2max between pregnant and nonpregnant subjects in cycling, swimming or weight-bearing exercise. Efficiency of work during exercise appears to be unchanged during pregnancy in non-weight-bearing exercise. During weight-bearing exercise, the work efficiency was shown to be improved in athletic women who continue exercising and those who stop exercising during pregnancy. When adjusted for weight gain, the increased efficiency is maintained throughout the pregnancy, with the improvement being greater in exercising women.Regular physical activity has been proven to result in marked benefits for mother and fetus. Maternal benefits include improved cardiovascular function, limited pregnancy weight gain, decreased musculoskeletal discomfort, reduced incidence of muscle cramps and lower limb oedema, mood stability, attenuation of gestational diabetes mellitus and gestational hypertension. Fetal benefits include decreased fat mass, improved stress tolerance, and advanced neurobehavioural maturation. In addition, few studies that have directly examined the effects of physical activity on labour and delivery indicate that, for women with normal pregnancies, physical activity is accompanied with shorter labour and decreased incidence of operative delivery.However, a substantial proportion of women stop exercising after they discover they are pregnant, and only few begin participating in exercise activities during pregnancy. The adoption or continuation of a sedentary lifestyle during pregnancy may contribute to the development of certain disorders such as hypertension, maternal and childhood obesity, gestational diabetes, dyspnoea, and pre-eclampsia. In view of the global epidemic of sedentary behaviour and obesity-related pathology, prenatal physical activity was shown to be useful for the prevention and treatment of these conditions. Further studies with larger sample sizes are required to confirm the association between physical activity and outcomes of labour and delivery.

Physical activity: the health benefits outweigh the risks.

Purpose of reviewThis article will summarize the current findings on the effects of physical activity on human health and well-being. Recent findingsPhysical activity is associated with enhanced health and reduced risk of all-cause mortality such as cardiovascular disease, hypertension, type 2 diabetes, obesity, osteoporosis, sarcopenia, cognitive disorders, and some forms of cancer. Nevertheless, the effects of exercise with respect to potential health consequences are complex. When untrained or previously sedentary persons undertake vigorous exertion suddenly, the undesired side effects of injuries, dehydration or cardiac arrest are amplified. SummaryIt is reasonable to conclude that the risk exposure through physical activity is outweighed by its overall benefits, and health authorities strongly encourage participation in moderate intensity physical activity on a daily basis. In the future, the identification and characterization of particularly inactive sub-groups of the population may facilitate and optimize the planning of public health interventions.

Effects of recommended levels of physical activity on pregnancy outcomes

OBJECTIVE We sought to examine the relation between recommended levels of physical activity during pregnancy and pregnancy outcomes. STUDY DESIGN We conducted an observational study with energy expenditure, aerobic fitness, and sleeping heart rate measured in 44 healthy women in late pregnancy. Medical records were examined for pregnancy outcome. RESULTS Active women, who engaged in > or = 30 minutes of moderate physical activity per day, had significantly better fitness and lower sleeping heart rate compared to the inactive. Duration of second stage of labor was 88 and 146 minutes in the active vs inactive women, respectively (P = .05). Crude odds ratio of operative delivery in the inactive vs the active was 3.7 (95% confidence interval, 0.87-16.08). Birthweight, maternal weight gain, and parity adjusted odds ratio was 7.6 (95% confidence interval, 1.23-45.8). Neonatal condition and other obstetric outcomes were similar between groups. CONCLUSION Active women have better aerobic fitness as compared to inactive women. The risk for operative delivery is lower in active women compared to inactive, when controlled for birthweight, maternal weight gain, and parity. Further studies with larger sample size are required to confirm the association between physical activity and pregnancy outcomes.

Pregnancy-related changes in activity energy expenditure and resting metabolic rate in Switzerland.

Background/Objectives:To measure resting metabolic rate (RMR), activity energy expenditure (AEE), total energy expenditure (TEE) and physical activity pattern, that is, duration and intensity (in metabolic equivalents, METs) of activities performed in late pregnancy compared with postpartum in healthy, well-nourished women living in Switzerland.Subjects/Methods:Weight, height, RMR, AEE, TEE and physical activity patterns were measured longitudinally in 27 healthy women aged 23–40 years at 38.2±1.5 weeks of gestation and 40.0±7.2 weeks postpartum.Results:The RMR during late pregnancy was 7480 kJ per day, that is, 1320±760 kJ per day (21.4%) higher than the postpartum RMR (P<0.001). Absolute changes in RMR were positively correlated with the corresponding changes in body weight (r=0.61, P<0.001). RMR per kg body weight was similar in late pregnancy vs postpartum (P=0.28). AEE per kg during pregnancy and postpartum was 40±13 and 50±20 kJ/kg, respectively (P=0.001). There were significant differences in daily time spent at METs<1.5 (1067 vs 998 min, P=0.045), at 2.5⩽METs <3.0 (58 vs 82 min, P=0.002) and METs⩾6 (1 vs 6 min, P=0.014) during pregnancy and postpartum, respectively.Conclusions:Energy expenditure in healthy women living in Switzerland increases in pregnancy compared with the postpartum state. Additional energy expenditure is primarily attributed to an increase in RMR, which is partly compensated by a decrease in AEE. The decrease in physical activity-related energy costs is achieved by selecting less demanding activities and should be taken into account when defining extra energy requirements for late pregnancy in Switzerland.

Eight-Year Longitudinal Changes in Body Composition in Healthy Swiss Adults

Objective: Significant changes in body composition occur during lifetime. This longitudinal study (8.0 ± 0.8 yrs) in a cohort of healthy sedentary and physically active men (n = 78) and women (n = 53), aged 20 to 74 yr describes: 1) the longitudinal changes in weight and body composition and 2) their associations with age and physical activity. Method: Fat-free mass (FFM) and body fat (BF) were assessed by bioelectrical impedance analysis (BIA). Subjects who regularly performed >3 hours per week of endurance type physical activity were classified as “Active”. Others were classified as “Sedentary”. Subjects were also separated by age (<45 yr vs ≥45 yr). Results: FFM increased by 1.7 ± 2.8 kg in men <45 yr who gained 4.0 ± 5.0 kg of body weight and was maintained (0.5 ± 1.6 kg) in women <45 y who gained 1.6 ± 3.0 kg of weight. A weight gain of 1.2 ± 3.3 kg in men ≥45 yr was accompanied by stable FFM (−0.1 ± 2.3 kg), and of 1.0 ± 3.2 kg was accompanied by a loss of FFM in women ≥45 yr. In active men ≥45 yr, maintenance of FFM was associated with smaller weight gains than in sedentary; sedentary men ≥45 yr decreased FFM with larger weight gains than active subjects. Sedentary women <45 yr were able to gain FFM; the active women maintained, but did not gain FFM with smaller weight gains than in sedentary women. FFM decreased in ≥45 yr women despite of small weight gains. Conclusion: Weight change is clearly associated with a change in FFM. Weight gain is necessary to offset age-related FFM loss between 20 and 74 yrs. In active men, a FFM increase was associated with less weight gain than sedentary men. Future studies should evaluate the threshold of weight change and the level of physical activity necessary to prevent age-related losses of FFM.

Energy and macronutrient requirements for physical fitness in exercising subjects

Optimal nutritional intakes are critical for health- and skill-related physical fitness. This review details the effect of energy restriction and supplementation on physical fitness, discusses the optimal chronic macronutrient intakes for physical fitness in exercising subjects and finally overviews the impact of short-term intakes of carbohydrate and protein, before, during and after exercise, on physical fitness of athletes. The present standings highlight that it is essential that health care givers personalize nutritional advice to meet the specific needs of exercising individuals while applying the described recommendations. It reminds the difficulty of providing straight nutritional recommendations for physical fitness on the basis of evidence-based medicine.

Maternal heart rate changes during labour.

OBJECTIVES Labour and delivery represent a considerable effort for pregnant women. Lack of aerobic fitness may limit pushing efforts during childbirth and represents increased cardiovascular strain and risk. Increasing prevalence of sedentary behaviour and lack of aerobic fitness may reduce heart rate reserve during labour. STUDY DESIGN We quantified maternal heart rate reserve (maximum heart rate minus resting heart rate) of 30 healthy pregnant women during labour and delivery and related it to habitual daily physical activity levels quantified during the third pregnancy trimester by the Pregnancy Physical Activity Questionnaire. RESULTS Heart rates during labour reached values similar to those observed during moderate to heavy physical exercise. During active pushing one out of five women reached heart rates more than 90% of their heart rate reserve (188 ± 7 beats per min). Half of the women reached more than 70% of heart rate reserve (172 ± 14 beats per min). Physically inactive women used more of their heart rate reserve as physically more active women (87 ± 20% vs. 65 ± 12%, upper and lower tertile respectively, p<0.05). CONCLUSIONS Use of heart rate reserve for the effort of labour is increased in physically inactive women and may potentially limit the intensity and duration of pushing efforts. Such higher cardiovascular strain in physically less active women may represent increased cardiovascular risk during labour.

Neural network versus activity-specific prediction equations for energy expenditure estimation in children

The aim of this study was to compare the energy expenditure (EE) estimations of activity-specific prediction equations (ASPE) and of an artificial neural network (ANNEE) based on accelerometry with measured EE. Forty-three children (age: 9.8 ± 2.4 yr) performed eight different activities. They were equipped with one tri-axial accelerometer that collected data in 1-s epochs and a portable gas analyzer. The ASPE and the ANNEE were trained to estimate the EE by including accelerometry, age, gender, and weight of the participants. To provide the activity-specific information, a decision tree was trained to recognize the type of activity through accelerometer data. The ASPE were applied to the activity-type-specific data recognized by the tree (Tree-ASPE). The Tree-ASPE precisely estimated the EE of all activities except cycling [bias: -1.13 ± 1.33 metabolic equivalent (MET)] and walking (bias: 0.29 ± 0.64 MET; P < 0.05). The ANNEE overestimated the EE of stationary activities (bias: 0.31 ± 0.47 MET) and walking (bias: 0.61 ± 0.72 MET) and underestimated the EE of cycling (bias: -0.90 ± 1.18 MET; P < 0.05). Biases of EE in stationary activities (ANNEE: 0.31 ± 0.47 MET, Tree-ASPE: 0.08 ± 0.21 MET) and walking (ANNEE 0.61 ± 0.72 MET, Tree-ASPE: 0.29 ± 0.64 MET) were significantly smaller in the Tree-ASPE than in the ANNEE (P < 0.05). The Tree-ASPE was more precise in estimating the EE than the ANNEE. The use of activity-type-specific information for subsequent EE prediction equations might be a promising approach for future studies.

Alterations in energy balance from an exercise intervention with ad libitum food intake

Better understanding is needed regarding the effects of exercise alone, without any imposed dietary regimens, as a single tool for body-weight regulation. Thus, we evaluated the effects of an 8-week increase in activity energy expenditure (AEE) on ad libitum energy intake (EI), body mass and composition in healthy participants with baseline physical activity levels (PAL) in line with international recommendations. Forty-six male adults (BMI = 19·7–29·3 kg/m2) participated in an intervention group, and ten (BMI = 21·0–28·4 kg/m2) in a control group. Anthropometric measures, cardiorespiratory fitness, EI, AEE and exercise intensity were recorded at baseline and during the 1st, 5th and 8th intervention weeks, and movement was recorded throughout. Body composition was measured at the beginning and at the end of the study, and resting energy expenditure was measured after the study. The intervention group increased PAL from 1·74 (se 0·03) to 1·93 (se 0·03) (P < 0·0001) and cardiorespiratory fitness from 41·4 (se 0·9) to 45·7 (se 1·1) ml O2/kg per min (P = 0·001) while decreasing body mass (−1·36 (se 0·2) kg; P = 0·001) through adipose tissue mass loss (ATM) (−1·61 (se 0·2) kg; P = 0·0001) compared with baseline. The control group did not show any significant changes in activity, body mass or ATM. EI was unchanged in both groups. The results indicate that in normal-weight and overweight men, increasing PAL from 1·7 to 1·9 while keeping EI ad libitum over an 8-week period produces a prolonged negative energy balance. Replication using a longer period (and/or more intense increase in PAL) is needed to investigate if and at what body composition the increase in AEE is met by an equivalent increase in EI.

Total Energy Expenditure, Energy Intake, and Body Composition in Endurance Athletes Across the Training Season: A Systematic Review

BackgroundEndurance athletes perform periodized training in order to prepare for main competitions and maximize performance. However, the coupling between alterations of total energy expenditure (TEE), energy intake, and body composition during different seasonal training phases is unclear. So far, no systematic review has assessed fluctuations in TEE, energy intake, and/or body composition in endurance athletes across the training season.The purpose of this study was to (1) systematically analyze TEE, energy intake, and body composition in highly trained athletes of various endurance disciplines and of both sexes and (2) analyze fluctuations in these parameters across the training season.MethodsAn electronic database search was conducted on the SPORTDiscus and MEDLINE (January 1990–31 January 2015) databases using a combination of relevant keywords.Two independent reviewers identified potentially relevant studies. Where a consensus was not reached, a third reviewer was consulted. Original research articles that examined TEE, energy intake, and/or body composition in 18–40-year-old endurance athletes and reported the seasonal training phases of data assessment were included in the review. Articles were excluded if body composition was assessed by skinfold measurements, TEE was assessed by questionnaires, or data could not be split between the sexes.Two reviewers assessed the quality of studies independently. Data on subject characteristics, TEE, energy intake, and/or body composition were extracted from the included studies. Subjects were categorized according to their sex and endurance discipline and each study allocated a weight within categories based on the number of subjects assessed. Extracted data were used to calculate weighted means and standard deviations for parameters of TEE, energy intake, and/or body composition.ResultsFrom 3589 citations, 321 articles were identified as potentially relevant, with 82 meeting all of the inclusion criteria. TEE of endurance athletes was significantly higher during the competition phase than during the preparation phase (p < 0.001) and significantly higher than energy intake in both phases (p < 0.001). During the competition phase, both body mass and fat-free mass were significantly higher compared to other seasonal training phases (p < 0.05).ConclusionsLimitations of the present study included insufficient data being available for all seasonal training phases and thus low explanatory power of single parameters. Additionally, the classification of the different seasonal training phases has to be discussed.Male and female endurance athletes show important training seasonal fluctuations in TEE, energy intake, and body composition. Therefore, dietary intake recommendations should take into consideration other factors including the actual training load, TEE, and body composition goals of the athlete.