Panagiota Klentrou

Influence of menstrual cycle and oral contraceptives on tolerance to uncompensable heat stress.

Abstract In this study we examined the influence of menstrual cycle phase and oral contraceptive use on thermoregulation and tolerance during uncompensable heat stress. Eighteen women (18–35 years), who differed only with respect to oral contraceptive use (n = 9) or non-use (n = 9), performed light intermittent exercise at 40°C and 30% relative humidity while wearing nuclear, biological and chemical protective clothing. Their responses were compared during the early follicular (EF, days 2–5) and mid-luteal (ML, days 19–22) phases of the menstrual cycle. Since oral contraceptives are presumed to inhibit ovulation, a quasi-early follicular (q-EF) and quasi-mid-luteal (q-ML) phase was assumed for the users. Estradiol and progesterone measurements verified that all subjects were tested during the desired phases of the menstrual cycle. Results demonstrated that rectal temperature (Tre) was elevated in ML compared with EF among the non-users at the beginning and throughout the heat-stress trial. For the users, Tre was higher in q-ML compared with q-EF at the beginning, and for 75 min of the heat-stress exposure. Tolerance times were significantly longer during EF [128.1 (13.4) min, mean (SD)] compared with ML [107.4 (8.6) min] for the non-users, indicating that these women are at a thermoregulatory advantage during the EF phase of their menstrual cycle. For the users, tolerance times were similar in both the q-EF [113.0 (5.8) min] and q-ML [116.8 (11.2) min] phases and did not differ from those of the non-users. It was concluded that oral contraceptive use had little or no influence on tolerance to uncompensable heat stress, whereas tolerance was increased during EF for non-users of oral contraceptives.

Cardiovascular disease risk in adolescent smokers: evidence of a 'smoker lifestyle'

This study assessed the prevalence of traditional cardiovascular disease risk factors in 119 adolescent smokers, compared to an age-matched sample of non-smokers. Participants were assessed for body mass index (BMI), relative body fat, systolic/diastolic/mean arterial blood pressure, total serum cholesterol, aerobic fitness, family (parents or siblings) smoking habits and history of cardiovascular disease. The results showed that BMI and relative body fat were significantly increased, while aerobic fitness was significantly decreased in smokers. Male smokers further demonstrated increased diastolic blood pressure and mean arterial pressure. Smokers also showed increased prevalence for family smoking habits and cardiovascular disease history. Prevalence rates for all other cardiovascular disease risk factors were increased in smokers, but the differences between groups did not reach statistical significance. It is concluded that the studied adolescent smokers demonstrated a higher risk for developing cardiovascular disease later in life, compared to their non-smoking counterparts.

Role of physical activity and perceived adequacy on peak aerobic power in children with developmental coordination disorder

The purpose of this study was to determine the mediating role of physical activity and perceived adequacy towards physical activity on peak aerobic power (VO(2)peak) in children with developmental coordination disorder. This case-control study involved 61 male and female subjects age 12-13 years with motor impairments and 61 healthy controls matched for age, gender and school location. Subjects were assessed for motor proficiency and classified as probable developmental coordination disorder (p-DCD) or healthy control using the Movement Assessment Battery for Children, 2nd Edition. VO(2)peak was assessed by a progressive exercise test on a cycle ergometer. Perceived adequacy towards physical activity was estimated using the Childrens Self-perception of Adequacy and Predilection for Physical Activity scale. Physical activity was monitored for seven days using accelerometry. Children with p-DCD had significantly lower VO(2)peak adjusted for lean mass (48.8±7.2 ml/kg LM/min; p≤0.05) compared to controls (53.1±8.2 ml/kg LM/min). Regression analysis demonstrated that perceived adequacy and physical activity were significant mediators in the relationship between p-DCD and VO(2)peak (R-squared=24.3%). In conclusion, using a stringent laboratory assessment, the current study verifies earlier non laboratory findings, adding low aerobic power, the most important component of cardiorespiratory fitness, to the list of health consequences associated with developmental coordination disorder.

Age of Puberty and Sexual Orientation in a National Probability Sample

The relations between sexual orientation and age of puberty in both men and women were examined in a national probability sample of the United States. The sample was the National Health and Social Life Survey (E. O. Laumann, J. H. Gagnon, R. T. Michael, & S. Michaels, 1994), which contains 3432 cases. Gay/bisexual men reported an earlier age of puberty (e.g., age of first pubic hair) relative to heterosexual men, but lesbian/bisexual women did not report a different age of puberty (i.e., age of menarche) than heterosexual women. These results confirm findings from prior research examining age of puberty using nonrepresentative samples and add to a body of literature suggesting that gay/bisexual men may score, on average, in the female-typical direction on certain sex-dimorphic physical and developmental characteristics.

Osteoporosis health beliefs and knowledge in college students: the role of dietary restraint.

This study investigated the relationship between dietary restraint (DR) and osteoporosis-related knowledge and beliefs in college women and men. A total of 517 university students completed measures of osteoporosis knowledge, perceived susceptibility to and severity of osteoporosis, barriers to and benefits of calcium and exercise, health motivation, exercise and calcium self-efficacy, and DR. Two MANOVAs were conducted to examine differences between high and low dietary restrainers on osteoporosis beliefs and knowledge. For women, HR scored higher on perceived susceptibility to, and severity of, osteoporosis, calcium barriers, and health motivation; for men, HR scored lower on exercise benefits. These results suggest that DR may be related to osteoporosis beliefs and knowledge differently for men and women.

Energetics of backstroke swimming in males and females

The aims of this study were to compare the oxygen demand of back crawl in male and female competitive swimmers and to examine the effect of stroke mechanics on these costs. Twenty-two male and 16 female swimmers participated in the study. The VO2 increased with v2 to a peak of approximately 4.03 l.min-1 in males and of approximately 2.88 l.min-1 in females. Mean VO2 of the males at a given v was significantly higher than that of the female swimmers, but the slopes of the regression lines were identical. Increases of velocity in both groups were related to increases in f and a decrease in distance. Costs per stroke (ml O2.str-1) in males were significantly higher than in females at a v = 1.0, 1.1, and 1.2 m.s-1. The relationship between VO2 and body mass at v = 1.1 m.s-1 was evaluated by deriving the exponent b in the allometric equation VO2 = a Mb. The exponent b was found to be 0.55. These results indicate that submaximal VO2 in back crawl swimming does not increase in proportion to body mass and may explain why VO2 (l.min-1) has been found to be higher in males than in females.

Gender Differences in Osteoporosis Health Beliefs and Knowledge and Their Relation to Vigorous Physical Activity in University Students.

Abstract Objective: The purpose of this cross-sectional investigation was to examine (1) gender differences in osteoporosis-related knowledge and beliefs and (2) if these beliefs could predict vigorous physical activity behavior in university students. Participants: Male (n = 176) and female (n = 351) university students participated in the study. Methods: Participants completed self-report measures of osteoporosis knowledge and health beliefs and vigorous physical activity. Results: Regardless of gender, osteoporosis knowledge was relatively poor. Women reported higher knowledge, perceived susceptibility, perceived severity, and calcium barriers, and lower exercise self-efficacy than men. Regression analyses showed that for women, perceived susceptibility, health motivation, and exercise self-efficacy predicted vigorous physical activity, whereas for men, exercise barriers was the only predictor. Conclusions: Gender differences in osteoporosis health beliefs appear to be greater in older adults than college-aged students. Interventions designed to increase vigorous physical activity may want to target different beliefs for men and women.

Predicting osteoporosis prevention behaviors: health beliefs and knowledge.

OBJECTIVES To investigate whether the expanded Health Belief Model (EHBM) could predict calcium intake and physical activity in adolescent girls. METHODS Participants self-reported calcium intake, physical activity, and osteoporosis health beliefs. Regression analysis examined the relationship between these beliefs and behaviors. RESULTS Calcium self-efficacy, calcium barriers, and osteoporosis knowledge predicted calcium intake, whereas exercise self-efficacy and health motivation predicted physical activity. CONCLUSIONS The EHBM appears to be useful in predicting osteoporosis prevention behaviors in adolescent girls. Interventions should focus on identifying barriers to calcium consumption and physical activity and increasing beliefs in the ability overcome them.

Response of Bone Turnover Markers and Cytokines to High-Intensity Low-Impact Exercise.

INTRODUCTION Low-impact, high-intensity interval exercise (HIE) was used to investigate the postexercise response in bone turnover markers and cytokines. METHODS Twenty-three recreationally active males (21.8 ± 2.4 yr) performed one HIE bout on a cycle ergometer at 90% maximum workload. The total duration of the exercise was 12 min and included six 1-min high-intensity exercise intervals separated by 1-min rest intervals. Blood samples were collected before exercise, 5 min, 1 h, and 24 h after exercise and were analyzed for serum levels of anti- and pro-inflammatory cytokines (interleukin 10 [IL-10], interleukin 6 [IL-6], interleukin 1-alpha [IL-1α], interleukin 1-beta [IL-1β], and tumor necrosis factor alpha [TNF-α]) and markers of bone formation (bone alkaline phosphatase [BAP], osteoprotegerin [OPG]) and resorption (amino-terminal cross-linking propeptide [NTX], receptor activator of NF-κB ligand [RANKL]). RESULTS There was a significant (P < 0.05) time effect for all bone turnover markers. Post hoc analysis showed that BAP, OPG, and RANKL significantly increased from baseline to 5 min after exercise (10.9%, 13.5%, and 34.2%, P < 0.05). At 1 h after exercise, only BAP was significantly higher than baseline (9.5%, P = 0.010) and remained higher than baseline at 24 h (10.9%, P = 0.001). NTX was significantly lower than baseline 24 h after exercise (-14.6%, P = 0.046). Significant (P < 0.05) time effects were also observed for IL-1α, IL-1β, IL-6, and TNF-α, with all four significantly increasing 5 min after exercise and returning to baseline levels 1 h after exercise. The postexercise changes in bone formation markers correlated positively with the anti-inflammatory cytokine (IL-10) and negatively with the pro-inflammatory cytokines while NTX correlated positively with a pro-inflammatory cytokine, TNF-α (P < 0.05). CONCLUSIONS These results suggest that HIE stimulates a response in bone turnover markers and cytokines and that a correlation exists between immune and skeletal responses to this form of exercise. This type of exercise may benefit individuals for whom high-impact exercise might be contraindicated.

Daily calcium intake in male children and adolescents obtained from the rapid assessment method and the 24-hour recall method

BackgroundIn order to rapidly assess nutrient intake, Food Frequency Questionnaires (FFQ) have been developed and proven to be reliable for quick, user friendly analysis in adults. However, the accuracy of these questionnaires in children has been studied to a limited extent. The aim of this study was to compare the daily calcium intake values obtained from the Rapid Assessment Method (RAM), an FFQ, for assessing daily calcium intake in child and adolescent males with the values obtained from the 24-hour recall method.MethodsSubjects included 162 child and adolescent males, aged 9–16 years, subdivided into elementary school (ES, 9–12 years) and high school (HS, 14–16 years) age groups.ResultsDaily calcium intake was significantly lower in ES compared with HS, using both methods. The intra-class correlation coefficients (ICC) between RAM values and those obtained using the 24-hour recall questionnaire were significant yet moderate (ICC = 0.46 and 0.43 for ES and HS, respectively). However, daily calcium intake obtained using RAM was significantly higher when compared with the 24-hour recall values in both ES (1576 +/- 1101 vs. 1003 +/- 543 mg, in RAM and 24-hour, respectively) and in HS males (1873 +/- 739 vs. 1159 +/- 515 mg, in RAM and 24-hour, respectively).ConclusionRAM overestimates daily calcium intake as compared with the 24-hour recall method in both child and adolescent males.