Vicki J. Harber

Effects of aerobic exercise training on estrogen metabolism in premenopausal women: a randomized controlled trial.

Background: Regular physical activity may alter estrogen metabolism, a proposed biomarker of breast cancer risk, by shifting metabolism to favor production of 2-hydroxyestrone (2-OHE1). Few studies, however, have examined this question using a randomized controlled trial. Purpose: To examine the effects of 12 weeks of aerobic exercise training on 2-OHE1 and 16α-hydroxyestrone (16α-OHE1) in premenopausal women. Methods: Participants were healthy, regularly menstruating, Caucasian women, 20 to 35 years, body mass index of 18 to 29.9, not using pharmacologic contraceptives, with average or below average fitness [maximal oxygen consumption (VO2max), <40 mL/kg/min]. Following a baseline menstrual cycle, participants (N = 32) were randomly assigned to a 12-week aerobic exercise training intervention (n = 17) or usual lifestyle (n = 15). Height, body mass, body composition by dual-energy X-ray absorptiometry, and VO2max were measured at baseline and following the intervention. Urine samples were collected in the luteal phase of four consecutive menstrual cycles. Results: The exercise group increased VO2max by 14% and had significant, although modest, improvements in fat and lean body mass. No significant between-group differences were observed, however, for the changes in 2-OHE1 (P = 0.944), 16α-OHE1 (P = 0.411), or the ratio of 2-OHE1 to 16α-OHE1 (P = 0.317). At baseline, there was an inverse association between body fat and 2-OHE1 to 16α-OHE1 ratio (r = −0.40; P = 0.044); however, it was the change in lean body mass over the intervention that was positively associated with a change in 2-OHE1 to 16α-OHE1 ratio (r = 0.43; P = 0.015). Conclusions: A 12-week aerobic exercise training intervention significantly improved aerobic fitness and body composition but did not alter estrogen metabolism in premenopausal women. Interestingly, an increase in lean body mass was associated with a favorable change in 2-OHE1 to 16α-OHE1 ratio. (Cancer Epidemiol Biomarkers Prev 2007;16(4):731–9)

Physical Activity, Nutrition, and Reproduction

Thin high mileage female and male runners often have reproductive problems. Strenuous physical activity can affect the hypothalamic-pituitary-gonadal (HPG) axis function of both females and males but physical activity alone probably does not cause reproductive problems. Nutritional changes and changes in the metabolic balance are likely responsible for the exercise-associated reproductive problems. Reproductive dysfunction in female athletes include pubertal delay (age at menarche 15.5 years for ballet dancers 15 years for athletes trained before menarche vs. 12.5 years for controls) luteal phase inadequacy anovulatory cycles secondary amenorrhea and oligomenorrhea. Male athletes tend to have reduced circulating testosterone androstenedione and luteinizing hormone levels. Endurance training has comparable chronic effects on the HPG axis in women and men. A possible mechanism of inhibition is changes to the gonadotropin releasing hormone-gonadotropin axis the cause of the changes is unknown. Neurotransmitter precursor deficiencies changes in thyroid function activation of stress hormones changes in glucoregulatory and other metabolic hormones changes in steroid metabolism in fat tissue changes in hepatic metabolism of binding proteins or an exaggerated peripheral response to exercise in a nutritionally stressed person are possible causes of the changes to the axis. Factors in the emergence of exercise-associated menstrual dysfunction include the physical and emotional stress of training and/or competition predisposition to menstrual irregularity inadequate nutrition weight loss and low body fat. Reduced physical activity reverses menstrual dysfunction. Further research is needed to clarify the relative importance of dietary deficiencies energy balance and physical activity in bringing about reproductive change and dysfunction. Obstacles to resolving the complex interrelationships are imprecision of dietary evaluation difficulty of accuracy versus freedom in energy balance measurements and the conceptual barrier of the body fat theory.

Reduced Plasma Glucose and Leptin After 12 Weeks of Functional Electrical Stimulation-Rowing Exercise Training in Spinal Cord Injury Patients

OBJECTIVE To investigate the effects of exercise training with a functional electrical stimulation (FES) rowing machine on insulin resistance, plasma leptin levels, and body composition in people with spinal cord injury (SCI). DESIGN Experimental study. SETTING A fitness and research center for people with disabilities. PARTICIPANTS Healthy male participants with paraplegia (N=6) participated in the study (mean age, 48.6±6y; mean weight, 70.06±3.28kg; injury levels between T4-5 and T10). INTERVENTIONS Twelve weeks of FES-rowing exercise training 3 to 4 times a week (600-800kcal). MAIN OUTCOME MEASURES Peak oxygen consumption, plasma leptin, insulin, and glucose levels, insulin sensitivity, body composition. RESULTS Twelve weeks of FES-rowing training improved aerobic fitness significantly (P=.048). In addition, plasma glucose and leptin levels were significantly decreased after exercise training by 10% and 28% (P<.028), respectively. A trend toward fat mass reduction was seen in 4 of the 6 subjects; this change did not reach statistical significance (P=.08). CONCLUSION A 12-week training program that included FES rowing improved aerobic fitness and fasting glucose and leptin levels in the absence of significant change to body composition, fasting insulin levels, or calculated insulin sensitivity in people with SCI.

A randomized controlled crossover trial of the effect of ginseng consumption on the immune response to moderate exercise in healthy sedentary men

Ginseng is a popular herbal remedy that is reputed to increase resistance to stress and improve immune function. Regular exercise results in acute physiologic stress that affects the immune response. This study was conducted to investigate the effects of daily consumption of a standardized ginsenoside-containing North American ginseng (Panax quinquefolius) extract on immune function before, during, and after a moderate-exercise protocol in healthy sedentary men. Ten healthy males were randomized to receive either ginseng (1125 mg.d-1) or placebo for 35 days. After a 3 month washout period, subjects received the opposite treatment for another 35 days. An exercise test and blood collection were performed at the end of each treatment period. Immune parameters and blood hormone levels were measured before, during, and after the exercise stress protocol. Ginseng treatment reduced the peripheral blood concentration of CD8+ T cells and increased mitogen-stimulated T cell production of interleukin-2 ex vivo. Ginseng had no effect on total white blood cell counts; on concentrations of neutrophils, monocytes, or lymphocytes (CD3+, CD4+, CD16+, CD20+); on lymphocyte proliferation; or on neutrophil oxidative burst. Ginseng did not significantly affect exercise-induced changes in plasma concentrations of lactate, insulin, cortisol, or growth hormone. The consumption of ginseng for 5 weeks had a limited effect on the immune response to an acute exercise protocol.

Associations between aerobic fitness and estrogen metabolites in premenopausal women

UNLABELLED Chronic physical activity may alter estrogen metabolism, a proposed biomarker of breast cancer risk, by causing a shift toward higher 2-OHE1 and lower 16alpha-OHE1 levels. PURPOSE To investigate the association between an objective indicator of chronic exercise, aerobic fitness, and 2-OHE1 and 16alpha-OHE1 in premenopausal women. METHODS Women with high aerobic fitness (N=17; VO2max>or=48 mL.kg.min-1) were compared with women with average aerobic fitness (N=13; VO2max<or=40 mL.kg.min-1) in terms of 2-OHE1 and 16alpha-OHE1 profiles. Participants were healthy, regularly menstruating, Caucasian women, aged 20-42 yr, with a normal body mass index (BMI) of 18-24, not using pharmacologic contraceptives. We measured height, weight, sum of four skinfolds, and maximal aerobic fitness (VO2max), using an incremental cycle ergometer test. Urine samples were collected during the follicular and luteal phase of the menstrual cycle. RESULTS There were no statistically significant differences between average and highly fit women for 2-OHE1, 16alpha-OHE1, or the 2:16alpha-OHE1 ratio in either the follicular or luteal phase. However, the high-fitness group showed a trend toward a higher luteal 2:16alpha-OHE1 (P=0.20). In ancillary analyses, a higher sum of skinfolds was associated with significantly higher luteal 16-OHE1 levels (r=0.39, P=0.03) and lower luteal phase 2:16 OHE ratio (r=-0.41, P=0.02). Higher BMI was associated with lower follicular phase 2-OHE1 (r=-0.37, P=0.04) and lower follicular 2:16 OHE1 ratio (r=-40, P=0.03). CONCLUSION This exploratory study is the first to investigate the association between aerobic fitness and estrogen metabolites in premenopausal women using metabolic parameters. We observed no statistically significant association between aerobic fitness and 2-OHE1 and 16alpha-OHE1, but found that body composition was associated with 2-OHE1 and 16alpha-OHE1 levels.

Assessment of Pre-Pregnancy Dietary Intake with a Food Frequency Questionnaire in Alberta Women

Purpose: Pre-pregnancy is an under-examined and potentially important time to optimize dietary intake to support fetal growth and development as well as maternal health. The purpose of the study was to determine the extent to which dietary intake reported by non-pregnant women is similar to pre-pregnancy dietary intake reported by pregnant women using the same assessment tool. Methods: The self-administered, semi-quantitative food frequency questionnaire (FFQ) was adapted from the Canadian version of the Diet History Questionnaire, originally developed by the National Cancer Institute in the United States. Pregnant women (n = 98) completed the FFQ which assessed dietary intake for the year prior to pregnancy. Non-pregnant women (n = 103) completed the same FFQ which assessed dietary intake for the previous year. Energy, macronutrients, and key micronutrients: long-chain omega-3 fatty acids, folate, vitamin B6, vitamin B12, calcium, vitamin D and iron were examined. Results: Dietary intake between groups; reported with the FFQ; was similar except for saturated fat; trans fat; calcium; and alcohol. Pregnant women reported significantly higher intakes of saturated fat; trans fat; and calcium and lower intake of alcohol in the year prior to pregnancy compared to non-pregnant women who reported intake in the previous year. Conclusions: Despite limitations; a FFQ may be used to assist with retrospective assessment of pre-pregnancy dietary intake.

Biological Maturation and Physical Activity in South Korean Adolescent Girls

INTRODUCTION/PURPOSE To examine whether body fatness (i.e., body mass index and percent body fat) and psychosocial correlates of physical activity (PA) mediate the relationships between pubertal status and PA and sedentary behavior (SB) among South Korean adolescent girls. METHODS Pubertal status, body fatness, sport competence, perceived barriers to PA, self-efficacy, parental support for PA, self-reported and step-determined PA, and self-reported SB were assessed among 236 South Korean adolescent girls (mean age = 13.56 ± 1.2 yr). RESULTS A direct association was identified between pubertal status and PA in all models; more advanced pubertal status predicted lower PA among South Korean adolescents (b = -0.51 to -0.57; P < 0.001). Indirect effects on the pubertal status-PA relationship were also found: body fatness, perceived barriers to PA, and self-efficacy mediated the relationship between pubertal status and PA. Parental support for PA did not moderate the relationship between maturation and PA. SB was not associated with pubertal status. CONCLUSIONS This study found mediated effects of body fatness, and psychosocial correlates (i.e., perceived barriers to PA, self-efficacy) on the relationship between maturity and PA among South Korean adolescent girls. Efforts to promote PA among South Korean adolescent girls should focus on reducing perceived barriers to PA, and increasing self-efficacy by providing more opportunities to have positive, and enjoyable experiences in PA among early-maturing girls.

Oral L-arginine before resistance exercise blunts growth hormone in strength trained males.

Acute resistance exercise and L-arginine have both been shown to independently elevate plasma growth hormone (GH) concentrations; however, their combined effect is controversial. The purpose was to investigate the combined effects of resistance exercise and L-arginine supplementation on plasma L-arginine, GH, GH secretagogues, and IGF-1 in strength trained participants. Fourteen strength trained males (age: 25 ± 4 y; body mass: 81.4 ± 9.0 kg; height: 179.4 ± 6.9 cm; and training experience: 6.3 ± 3.4 y) participated in a randomized double-blind crossover design (separated by ~7 days). Subjects reported to the laboratory at 08:00 in a fasted state, consumed L-arginine (ARG; 0.075 g·kg-1 body mass) or a placebo (PLA) before performing an acute bout of resistance exercise (3 sets of 8 exercises, 10 repetitions at ~75% 1RM). Blood samples were collected at rest, before exercise, and at 0, 15, 30, and 60 min of rest-recovery. The ARG condition significantly increased plasma L-arginine concentrations (~120%) while no change was detected in the PLA condition. There were no differences between conditions for GH, GH-releasing hormone, ghrelin, or IGF-1 at any time point. GH-inhibiting hormone was significantly lower in the ARG condition. However, integrated area under the curve for GH was blunted in the ARG condition (L-arginine = 288.4 ± 368.7 vs. placebo = 487.9± 482.0 min·ng·mL1, p < .05). L-arginine ingested before resistance exercise significantly elevated plasma L-arginine concentration but attenuated plasma GH in strength trained individuals despite a lower GHIH. Furthermore our data shows that the GH suppression was not due to a GH or IGF-1 induced autonegative feedback loop.

A Randomized, Controlled Trial of Ginseng Consumption on the Immune Response to a Moderate Exercise Stress Protocol in Non-Athletic Women~!2008-07-27~!2009-04-04~!2010-07-06~!

Background: Ginseng is a popular herbal remedy that has been proposed to increase resistance to stress and en- hance immune function. Regular moderate exercise results in an acute physiological stress that affects immune function. Objective: This study was conducted to investigate the effects of daily consumption of a standardized ginsenoside- containing North American ginseng (Panax quinquefolius) extract on immune function before, immediately after, and during recovery from moderate exercise in healthy, non-athletic women. Research design and methods: A double-blinded randomized trial was conducted where healthy female subjects (n=12) were randomized to receive either ginseng (1125 mg/d; n=6) or placebo (n=6) for four weeks. An exercise test was per- formed and peripheral blood collected before and after the four-week treatment period. Immune assays (phenotype analy- sis, neutrophil function, lymphocyte proliferation and natural killer cell cytotoxicity) were performed before, immediately after, and 30 minutes post-exercise. Results: Ginseng-treated subjects had a lower (P<0.05) proportion of antigen mature CD4+CD45RO+ peripheral blood cells before and after exercise, and experienced a sustained reduction (P<0.05) in the proportions of total CD28+ and CD4+CD28+ cells during recovery from exercise. The ginseng group had significantly higher mitogen-stimulated neutro- phil function (oxidative burst) at all exercise protocol time points (P<0.05). There were no effects of ginseng on the pro- portions of other immune cells, lymphocyte proliferation, or natural killer cell cytotoxicity in peripheral blood. Conclusions: The consumption of ginseng for a four-week period improved the ability of neutrophils to respond to stimu- lation and produced changes consistent with less T cell activation after an acute exercise stress.

Physical activity and sedentary behaviour of toddlers and preschoolers in child care centres in Alberta, Canada

ObjectiveTo describe duration of physical activity and duration and bouts of sedentary behaviour during child care in a sample of toddlers and preschoolers (19–60 months) from Alberta, Canada, and to examine whether duration and bouts differed among sex, age and parental immigration status groups.MethodsOne hundred and fourteen children aged 19–60 months from eight child care centres throughout Alberta participated. Data were collected at baseline of a study examining revised Alberta Child Care Accreditation Standards. Duration of physical activity (light (LPA), moderate-to-vigorous (MVPA)) and duration and bouts (1–4, 5–9, 10–14, and >-15 minutes) of sedentary behaviour during child care were accelerometer-derived using 15-second epochs during October/November, 201 3. Median [Interquartile ranges] and ANOVAs, accounting for the clustered nature of the data, were calculated.ResultsMinutes/hour spent in sedentary behaviour, LPA and MVPA were 36.9 [32.9, 40.7], 18.4 [16.0, 20.9] and 4.2 [2.5, 5.6] respectively. Frequency/hour of sedentary bouts lasting 1–4,5–9, 10–14 and >15 mins were 6.7 [6.1, 7.6], 0.9 [0.6, 1.1], 0.4 [0.2, 0.5] and 0.3 [0.2, 0.4] respectively. Preschoolers participated in less sedentary behaviour and more LPA and MVPA, and had fewer sedentary bouts lasting 10–14 and >-15 mins compared to toddlers (p < 0.05).ConclusionThis is the first Canadian study to report on the duration of physical activity and duration and bouts of sedentary behaviour among both toddlers and preschoolers attending child care centres. These findings suggest child care interventions are needed to increase MVPA and decrease total sedentary behaviour while continuing to promote short sedentary bouts.RésuméObjectifsDécrire la durée de l’activité physique et la durée et les épisodes de comportement sédentaire pendant la garde d’un échantillon de tout-petits et d’enfants d’âge préscolaire (19 à 60 mois) de l’Alberta, Canada, et examiner si la durée et les épisodes diffèrent selon le sexe, l’âge et le statut d’immigrant des parents.MéthodesCent quatorze enfants âgés de 19 à 60 mois de huit garderies de l’Alberta y ont participé. Les données ont été recueillies au départ d’une étude examinant les normes d’accréditation révisées des services de garde d’enfants de l’Alberta. La durée de l’activité physique (légère [APL], modérée à vigoureuse [APMV]) et la durée et les épisodes (1 à 4, 5 à 9, 10 à 14 et >- 15 minutes) de comportement sédentaire pendant la garde a été calculée avec un accéléromètre au moyen d’époques de 15 secondes en octobre et novembre 201 3. On a calculé la médiane [intervalle interquartile] et les ANOVA qui tiennent compte de la nature en grappe des données.RésultatsLes minutes et les heures de comportement sédentaire, d’APL et d’APVM étaient de 36,9 [32,9, 40,7], 18,4 [16,0, 20,9] et 4,2 [2,5, 5,6] respectivement. La fréquence et la durée des épisodes sédentaires qui allaient del à 4, 5 à 9,10 à 14 et >- 15 minutes étaient de 6,7 [6,1, 7,6], 0,9 [0,6, 1,1], 0,4 [0,2, 0,5] et 0,3 [0,2, 0,4] respectivement. Les enfants d’âge préscolaire participaient à moins d’épisodes de comportement sédentaire et plus d’APL et d’APMV, et avaient moins d’épisodes sédentaires d’une durée de 10 à 14 et de >- 15 minutes comparés aux tout-petits (p < 0,05).ConclusionsIl s’agit de la première étude canadienne à rendre compte de la durée de l’activité physique et de la durée et des épisodes de comportement sédentaire chez les tout-petits et les enfants d’âge préscolaire dans des garderies. Ces constatations suggèrent que les interventions en garderie sont nécessaires pour augmenter l’APVM et réduire le comportement sédentaire total tout en continuant de favoriser les courts épisodes sédentaires.