Background: Some controversy exists over the possibility that exercise during pregnancy might increase the risk of preterm delivery. Objective: This study aimed to determine the possible cause-effect relationship between regular exercise performed during the second and third trimesters of pregnancy by previously sedentary, healthy gravidae and gestational age at the moment of delivery. Methods: Caucasian (Spanish) women with singleton gestation were assigned to either a training (n = 72) or a control (n = 70) group. The supervised training programme focused mainly on very light resistance and toning exercises and included ,80 sessions (three times/ week, 35 min/session from weeks 12-13 to weeks 38-39 of pregnancy). Results: No significant differences were found (p.0.05) between the groups in those maternal characteristics (age, smoking habits, number of hours standing or prior parity history) that could potentially influence gestational age. The mean gestational age did not differ (p = 0.745) between the training (39 weeks,3 days (SD 1 day)) and the control group (39 weeks,4 days (SD 1 day)). Conclusions: Previously sedentary, healthy gravidae with singleton gestation can safely engage in moderate, supervised exercise programmes until the end of gestation as this would not affect gestational age.Historically, and largely based on socio-cultural reasons more than on scientific evidence, pregnant women have been encouraged to reduce physical activity (PA) and stop working during pregnancy because of perceived increased risk of problems, e.g., such as early pregnancy loss or reduced placental circulation. 1In 1985 the American College of Obstetricians and Gynecologists (ACOG) provided conservative recommendations for exercise during pregnancy; women were told to avoid intense activities (such as jogging or cycling) for more than 15 minutes per session, and limit their heart rate to (140 beats/min.2 In recent years, however, an increasing number of women are engaging in regular exercise during pregnancy. This tendency is overall supported by the results of several publications over the last decade, reporting few negative effects of PA on the pregnancy of a healthy gravida. [4][5][6][7] More recent ACOG guidelines are in fact more proactive regarding exercise recommendations during pregnancy. 8 Obstetricians, family practitioners and nurse midwives are, however, not always prepared to provide constructive guidance for their physically active patients. One question frequently addressed and still to be clearly answered relates to the possibility that high PA levels, especially during the second part of pregnancy, might increase the risk for preterm delivery. A potential source of controversy on this issue arises from the fact that more ''active'' or energy-consuming occupational professional activities that require prolonged standing (.3 h/day) and/or carrying loads .10 kg, such as in industrial work or as cleaning staff and shopkeepers, might increase the risk of preterm births and low birth weight in compari...
We present a new model of the underlying dynamics of the oxygen uptake VO2(v,t) kinetics for various exercise intensities. This model is in the form of a set of nonlinear coupled vector fields for the VO2(v,t) and v, the derivative of the exercise intensity with respect to time. We also present a new and novel means for calculating the oxygen demand, D(v,t), and hence also the oxygen deficit and debt, given the time series of the VO2(v,t). This enables us to give better predictions for these values especially for when exercising at or close to maximal exercise intensities. Our model also allows us to predict the oxygen uptake time series given the time series for the exercise intensity as well as to investigate the oxygen uptake response to nonlinear exercise intensities. Neither of these features is possible using the currently used three-phase model. We also present a review of both the underlying physiology and the three-phase model. This includes for the first time a complete set of the analytical solutions of the three-phase model for the oxygen deficit and debt.
We present a mathematical model, in the form of two coupled ordinary differential equations, for the heart rate kinetics in response to exercise. Our heart rate model is an adaptation of the model of oxygen uptake kinetics of Stirling et al. [21]; a physiological justification for this adaptation, as well as the physiological basis of our heart rate model is provided. We also present the optimal fit of the heart rate model to a set of raw un averaged data for multiple constant intensity exercises for an individual at a particular level of fitness.
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