Gestational Age and Pregnancy Outcomes

Some of the important pregnancy outcomes such as preterm delivery, growth restriction and low birth weight (LBW) infant, stillbirth, and some long-term chronic diseases vary by race and ethnicity but also tend to be associated with gestational age of the infant at birth. In the United States, during the last 25–30 years, the rate of low birth weight has increased, as has the rate of preterm delivery among both whites and blacks. Examination of causes for these secular trends has focused mainly on changes in the distribution of maternal age, race, and certain psychosocial factors. However, gestational age at birth is associated with most of these pregnancy outcomes, particularly infant mortality, certain morbidities, birth weight, and preterm birth. In this chapter, the association between gestational age and some significant pregnancy outcomes will be discussed

Clothing fabric effects on physiological and comfort responses

During exercise and in hot environments, the main cooling mechanism is through sweat evaporation. However, clothing can disrupt evaporation, which leads to decreased performance and in some cases can lead to heat illness. New fabrics and designs have been introduced with the purpose of improving thermoregulatory properties. One of those innovations is a channeled synthetic fabric. The first of three studies evaluated the effects of a channeled synthetic and synthetic t-shirts under a ballistic vest on physiological and comfort responses during exercise in a hot environment. Eight participants, in counterbalanced order, completed two simulated "industrial" protocols for three hours. The overall (0 - 180 min) change in rectal temperature was significantly (p = 0.04) lower with channeled synthetic shirt compared to a synthetic shirt. Additionally, overall change in thermal comfort (p = 0.05), sweating sensation (p = 0.06), and heart rate (p = 0.07) were, or tended to be more favorable throughout exercise with channeled synthetic compared to synthetic shirt. We also examined the effects of channeled synthetic shirt and synthetic cycling shirt effects on thermoregulation, thermal comfort, and heart rate. Eight participants attempted a 30-km cycling time trial. Results indicated significantly (p = 0.04, n = 8) smaller increase in rectal temperature from baseline to 15th km (first dropout) with the channeled synthetic shirt compared to cycling shirt. Also, the change in thermal comfort was significantly (n = 5, p = 0.03) lower with channeled shirt compared to cycling shirt from baseline to 30th km. A third study examined channeled compression shorts, compression shorts, and cycling shorts effects on thermoregulation, heart rate, and thermal comfort response during 30-km cycling trial in hot a environment. Eight participants completed a 25-km cycling trial. Results revealed no significant main effect for rectal or skin temperatures, heart rate, and thermal comfort between the three different types of shorts (n = 8, p > 0.05). In conclusion, wearing a channeled synthetic shirt provided better thermoregulatory or thermal comfort responses compared to synthetic shirt in two studies. Channeled compression shorts did not improve thermoregulatory or thermal comfort responses compared to cycling and compression shorts. (Published By University of Alabama Libraries

Effect of whole-body vibration on acute recovery after fatiguing exercise

High-intensity intermittent or resistance activity for a short period of time causes an increased break down of energy stores and accumulation of metabolic by-products. Increased metabolic disturbances may lead to decreased muscle contractile function which eventually will lead to muscle fatigue. Sufficient recovery time is needed for optimal competitive performance and optimizing the ability to tolerate high-intensity, various lengths and duration training loads. There are a number of recovery modalities available that have been used between training sessions, pre- and post- training, and between competitions. In order to evaluate vibration as a recovery aid that contributes to improved performance, three studies were conducted. The first study evaluated the effects of whole-body vibration (WBV) and WBV plus cooling on lower-body peak and mean anaerobic performance, leg volume, perceived recovery, and muscle soreness. The second study evaluated the effects of WBV and upper-body vibration (UBV) on upper-body performance, perceived recovery and muscle soreness, and the third study evaluated the effect of WBV on sprint performance, leg volume and perceived recovery. Healthy and physically active male and female volunteers participated in the studies. In a repeated measures, counterbalanced design, participants completed fatiguing exercise, each recovery treatment and performance test. As indicated by the group mean data, results of the first study suggested possible psychological but not performance enhancing benefits after the use of WBV and WBVC as a recovery method. The findings of the second study suggest no psychological or physiological benefits using WBV and UBV as a recovery modality. The results of the third study suggest no benefits for WBV in enhancing recovery or sprint performance. However, while actual recovery was not enhanced, perceived recovery was better after WBV compared to no vibration. Even though actual recovery or performance was not enhanced by the addition of WBV to the recovery, psychological perception of better recovery may be of some benefit for training or competition. It appears that acute exposure to WBV does not enhance performance under the conditions of this study. (Published By University of Alabama Libraries

Cardiovascular and themoregulatory responses to ice slurry ingestion during heat stress

Fluid ingestion has been reported to influence cardiovascular and thermoregulatory function, thereby affecting exercise performance. It remains unclear whether ice slurry ingestion during exercise results in similar effects. Three experiments examined thermal-, cardiovascular-, and exercise-related responses to ice slurry ingestion. In the first study, participants in firefighter protective clothing walked at ~7 METs in 35 °C while ingesting carbohydrate-electrolyte beverages as a tepid fluid, cold fluid, and ice slurry in a counterbalanced repeated measures study design. When ingested in large quantities and during uncompensable heat stress, ice slurry ingestion mitigated physiological strain by attenuating the rise in heart rate and rectal temperature. In a second study, cardiovascular drift (CV drift) was measured during 45 min of cycling at 60% maximal oxygen uptake (V̇O2max) in 35 °C, immediately followed by measurement of V̇O2max. Participants ingested fluid and ice slurry during two counterbalanced trials of exercise. CV drift was attenuated with ice slurry ingestion but V̇O2max was unaffected. In a third study, participants ingested ice slurry or cold fluid ad libitum while cycling at 50% maximal workload in 35 °C, immediately followed by a 15-min time trial during which participants completed as much work as possible. Compared to the fluid treatment, participants consumed half as much ice slurry, but total work completed during the time trial was not different. In conclusion, ice slurry ingestion blunts physiological strain during conditions in which evaporative heat loss is impaired, such as when wearing occlusive coverings. Furthermore, ice slurry ingestion attenuates the magnitude of CV drift during exercise in the heat, but this does not blunt the decrease in V̇O2max associated with exercise in hot conditions. Lastly, a smaller quantity of ice slurry is voluntarily ingested compared to cold fluid during prolonged submaximal exercise in the heat, but this does not differentially affect exercise performance. (Published By University of Alabama Libraries

Effects of bunker gear temperature and different work rates on micro-E and heat stress

Wearing protective clothing (PC) such as firefighter bunker gear leads to increased heat strain. Bunker gear has multiple layers which creates a heat sink during the first several minutes after donning, potentially providing some amount of cooling of the micro-environment (micro-E) around the skin. Furthermore, predicting heat strain at various work rates while wearing PC is important for determining work tolerance limits. The purpose of these studies was to determine the effect of a COLD (< 0 °C) bunker gear on rectal temperature (T_re ) and micro-E at a steady-state exercise intensity and to begin creating a regression model to predict micro-E temperature and relative humidity under bunker gear based on work rate. Studies I and II utilized a repeated-measures randomized experimental design, which consists of 4 trials (LO, MOD, HI (HOT), and HI (COLD)). Human volunteers wore bunker gear for 30 min while oxygen uptake (V&#775;O_2), heart rate, perceptive measures (ratings of perceived exertion, thermal sensation, sweating sensation, and clothing comfort), T_re, skin temperature, and micro-E (temperature and relative humidity at the anterior and posterior portion of the jacket and pants) were measured. A repeated measures MANOVA with a Bonferroni post hoc analysis was used to evaluate: the physiological measures; while the Friedman's Test was performed with a Wilcoxon Signed Rank Test on all perceptual measures. The COLD bunker gear did not significantly alleviate heat strain when compared to HOT bunker gear. Additionally we low, moderate and high intensities of work in ~ 29 °C macro-E WBGT did not differentially affect micro-E WBGT under bunker gear, and these data were used to derive models of micro-E from macro-E. Further data is needed to cross-validate the derived micro-E WBGT model predicted from macro-E WBGT and work rate. (Published By University of Alabama Libraries

Effect of Menthol on Respiratory and Perceptual Responses to Exercise in Firefighter Protective Gear

Impaired respiration reduces firefighters’ work capacity. This study evaluated the effect of menthol lozenge on respiratory and perceptual responses during exercise in a hot environment. Ten participants wearing firefighter protective gear performed two repeated exercise and rest trials in a counter-balanced order. Exercise consisted of two bouts of 20-min treadmill exercise at 60% of maximal oxygen uptake and one bout of 20-min stepping exercise at a wet bulb global temperature of 35°C. Participants either took 10-mg menthol or control lozenges prior to the beginning of each exercise bout. Respiratory gas exchange, heart rate, thermal sensation, and breathing comfort were continuously recorded. Menthol lozenges significantly increased pulmonary ventilation (menthol: 45.0±6.6 L•min-1 vs. control: 41.4±5.8 L•min-1 and menthol: 52.7±9.7 L•min-1 vs. control: 46.5±7.0 L•min-1, for the 1st and 2nd treadmill exercise, respectively) and oxygen consumption (menthol: 26.7±2.0 ml•kg-1•min-1 vs. control: 25.2±2.3 ml•kg-1•min-1 and menthol: 28.8±2.3 ml•kg-1•min-1 vs. control: 26.9±1.9 ml•kg-1•min-1, for the 1st and 2nd treadmill exercise, respe¬cti¬ve¬ly) (p0.05). The ventilatory equivalents though were not different throughout the exercise (p>0.05). Ratings of thermal sensation and breathing comfort were not different (p>0.05). It was concluded that menthol could alter breathing pattern and increase respiratory responses during strenuous exercise in the heat. There was no favorable effect of menthol on respiratory or perceptual responses under exercise-heat stress