Effects of intensive training on menstrual function and certain serum hormones and peptides related to the female reproductive system

Bloody stressed! A systematic review of the associations between adulthood psychological stress and menstrual cycle irregularity

Regular menstruation is a key indicator of general health and irregular menstrual parameters have been associated with elevated risk of adverse health outcomes. While psychological stress is believed to contribute to abnormal menstruation, little is known of the effects of discrete psychological stressors, including the COVID-19 pandemic, on menstrual function. A systematic database search was performed and studies investigating the relation between psychological stress and menstrual cycle irregularity in otherwise healthy adults were included. Two independent investigators completed abstract and full-text screening, data extraction, and risk of bias assessment. In the 41 included studies, a variety of stressors were assessed, namely COVID-19 pandemic stress, academic stress, and occupational stress. Our review found most studies report an association between psychological stress and menstrual dysfunction, with the most common disruptions being irregular menstruation and abnormal menstrual flow. Our findings also underlined notable discrepancies in the operational definitions used in the study of menstrual disorders. These observations emphasize the importance of psychological stress as a modifiable risk factor associated with irregular menstruation.

Age and menstrual cycle may be important in establishing pregnancy in female athletes after retirement from competition

BACKGROUND

Although it has been shown that amenorrhea associated with low energy availability or relative energy deficiency in sport affects body physiology in female athletes, the association between menstrual dysfunction during active sports careers and reproductive function after retirement is not clear.

OBJECTIVE

To investigate the association between menstrual dysfunction during their active sports career and post-retirement infertility in female athletes.

METHODS

A voluntary web-based survey was aimed at former female athletes who had become pregnant and gave birth to their first child after retirement. Nine multiple-choice questions were included, on maternal age, competition levels and menstrual cycles during active sports careers, time from retirement to pregnancy, the time of resumption of spontaneous menstruation after retirement, conception method, and mode of delivery, etc. Regarding cases of primary and secondary amenorrhea among the abnormal menstrual cycle group, only those whose spontaneous menstruation had not recovered from retirement to the time of pregnancy were included in the study. The association between the presence of abnormal menstrual cycles from active sports careers to post-retirement pregnancy and the implementation of infertility treatment was evaluated.

RESULTS

The study population included 613 female athletes who became pregnant and gave birth to their first child after retiring from competitive sports. Of the 613 former athletes, the infertility treatment rate was 11.9%. The rate of infertility treatment was significantly higher in athletes with abnormal than normal menstrual cycles (17.1% vs. 10.2%, p = 0.0225). Multivariable logistic regression analysis showed that maternal age (adjusted odds ratio [OR] 1.194; 95% confidence interval [CI] 1.129, 1.262) and abnormal menstrual cycles (OR and 1.903; adjusted OR 1.105, 3.278) were the relevant factors for infertility treatment.

CONCLUSION

It was suggested that menstrual dysfunction that persist from active sports careers to post-retirement may be a factor in infertility when trying to conceive after retirement.

Menstrual cycles and the impact upon performance in elite British track and field athletes: a longitudinal study

Objective

To assess the prevalence of menstrual disorders and the perceived effect of menstrual cycles upon performance in elite athletes.

Methodology

A longitudinal survey in the form of a questionnaire was sent to female track and field athletes at British Athletics every 6 months, over a five-year period between 1st October 2014 and 1st October 2019 in the United Kingdom (UK).

Results

128 athletes completed an average of 4.2 ± 2.9 questionnaires across the study period. The mean age of menarche was 14.2 ± 1.4 years, 13.4 ± 1.3 years and 12.8 ± 1.4 years in endurance, power, and thrower athletes respectively (p < 0.05). Two-thirds (66%; n = 82) reported consistently regular cycles, 30% (n = 37) irregular at some point during the period of observation and 4% (n = 5) were amenorrhoeic. 87 athletes (68%) reported dysmenorrhoea and 40 (31%) menorrhagia. More than three quarters (76.8%; n = 96) described their cycle negatively affected performance. Amongst those who reported when the negative impact occurred (n = 91), 40% (n = 36) reported this in the late luteal phase and 35% (n = 32) during the early follicular phase. 79% (n = 100) of athletes reported at least one cyclical symptom, of which bloating, lower back and pelvic pain were most frequently experienced.

Conclusion

This data highlights the complex interrelationship between women's health and elite athletic performance. Athletes perceive a negative impact from their menstrual cycles upon performance with a desire to manage these more effectively, particularly during competition. Female reproductive health expertise in the multi-disciplinary management of elite athletes is required.

The Risk of Menstrual Dysfunction Increases for Women during U.S. Army Basic Combat Training

PURPOSE

To determine whether changes in menstruation develop in female trainees during BCT and whether changes in body mass, body composition and/or physical activity are associated with menstrual interruption during BCT.

METHODS

Female trainees grouped according to self-reported menstrual status in the 12 months before BCT as having regular cycles (RC; n = 352) or MD ( n = 97) completed height, body mass, and body composition assessments and questionnaires before and after BCT. Fisher's exact test and Mann-Whitney U test were used to compare between-group differences in categorical and continuous variables, respectively. Among RC trainees, odds ratios were calculated to examine the influence of changes in body mass, lean mass, and fat mass on a trainee's likelihood to miss a period during BCT.

RESULTS

There were no differences in race, height, body mass, body mass index, or physical activity history at pre-BCT between RC and MD ( P > 0.05). Overall, 86% of trainees experienced changes to menstruation during BCT. RC were more likely than MD to have at least one period during BCT (81% vs 69%, respectively, P = 0.01). Among RC, gaining more body mass and lean mass and losing less fat mass were associated with increased odds of missing a period during BCT.

CONCLUSIONS

These findings demonstrate that most female trainees experience menstrual changes during BCT. Menstrual cycle interruptions do not appear to align with loss of body or fat mass.

Cell apoptosis in the testis of male rats is elevated by intervention with β-endorphin and the mu opioid receptor

β-endorphin (β-EP) is involved in the regulation of male germ cells; however, little is known about the effect of β-EP on primary germ cells via opioid receptors. In this study, we first revealed significant cell apoptosis in the testis of male rats after β-EP intervention. Subsequently, the expression of the mu opioid receptor (MOR) was detected in both Leydig cells (LCs) and spermatogonia (SGs) by fluorescence colocalization; overlapping signals were also detected in apoptotic cells. In addition, LCs and SGs were separated from the testis of male rats and primary cells were treated with β-EP; this increased the mRNA levels of MOR and was accompanied by acute cell apoptosis. Our findings provide a foundation for the further study of apoptosis in reproductive cells regulated by β-EP and the MOR receptor.

Amenorrhea and oligomenorrhea risk related to exercise training volume and intensity: Findings from 3705 participants recruited via the STRAVA™ exercise application

OBJECTIVES

To investigate associations between self-reported exercise training habits and amenorrhea/oligomenorrhea among physically active women.

DESIGN

A cross-sectional survey was completed by 3705 women (median age = 40 years [quartile 1, quartile 3: 30, 45], body mass index = 22.1 kg/m2 [20.5, 24.2]) representing multiple nationalities and sports via the STRAVA™ exercise application. Respondents selected the amount of time they participated in low intensity, moderate intensity, and high intensity exercise training per week. Amenorrhea/oligomenorrhea was defined as self-reporting ≤10 menses in the last year.

METHODS

Associations between weekly exercise volume for low intensity training, moderate intensity training, and high intensity training and amenorrhea/oligomenorrhea were modeled with univariate logistic regression models, followed by adjustment for age and body mass index.

RESULTS

Amenorrhea/oligomenorrhea prevalence was 16 % (n = 576/3705), with no difference by country of origin or most sport modes. In adjusted models, participating in low intensity training ≥7 h/week or moderate intensity training ≥6 h/week was associated with 1.43 (95 % confidence interval: 1.04-1.96) and 1.46 (1.10-1.95) greater odds of amenorrhea/oligomenorrhea compared to 2 to 3 h/week, respectively. Similarly, high intensity training ≥5 h/week was associated with 1.41 (1.03-1.92) greater odds of amenorrhea/oligomenorrhea compared to 1 to 2 h/week. Participating in low intensity training for ≤30 min/week compared to 2 to 3 h/week was associated with reduced amenorrhea/oligomenorrhea odds (0.65 [0.44-0.94]).

CONCLUSIONS

Taken together, these associations suggest greater weekly exercise volume, irrespective of intensity, may increase amenorrhea/oligomenorrhea risk among physically active women.

The impact of the menstrual cycle on orthopaedic sports injuries in female athletes

There is a disparity in sport-related injuries between sexes, with females sustaining non-contact musculoskeletal injuries at a higher rate. Anterior cruciate ligament ruptures are between two and eight times more common than in males, and females also have a higher incidence of ankle sprains, patellofemoral pain, and bone stress injuries. The sequelae of such injuries can be devastating to an athlete, resulting in time out of sport, surgery, and the early onset of osteoarthritis. It is important to identify the causes of this disparity and introduce prevention programmes to reduce the incidence of these injuries. A natural difference reflects the effect of reproductive hormones in females, which have receptors in certain musculoskeletal tissues. Relaxin increases ligamentous laxity. Oestrogen decreases the synthesis of collagen and progesterone does the opposite. Insufficient diet and intensive training can lead to menstrual irregularities, which are common in female athletes and result in injury, whereas oral contraception may have a protective effect against certain injuries. It is important for coaches, physiotherapists, nutritionists, doctors, and athletes to be aware of these issues and to implement preventive measures. This annotation explores the relationship between the menstrual cycle and orthopaedic sports injuries in pre-menopausal females, and proposes recommendations to mitigate the risk of sustaining these injuries.

Characterization of Female US Marine Recruits: Workload, Caloric Expenditure, Fitness, Injury Rates, and Menstrual Cycle Disruption during Bootcamp

Basic training is centered on developing the physical and tactical skills essential to train a recruit into a Marine. The abrupt increase in activity and energy expenditure in young recruits may contribute to high rates of musculoskeletal injuries, to which females are more susceptible. To date, the total workload of United State Marine Corps (USMC) bootcamp is unknown and should include movement around the military base (e.g., to and from dining facilities, training locations, and classrooms). Thus, the purpose of this effort was to quantify workload and caloric expenditure, as well as qualitatively assess the impact of female reproductive health and injury rates in female recruits. Female recruits (n = 79; age: 19.1 ± 0.2 years, weight: 59.6 ± 0.8 kg, height: 161.6 ± 0.7 cm) wore physiological monitors daily throughout 10 weeks of USMC bootcamp. Physical fitness test scores, physiological metrics from wearables, injury data, and menstrual cycle information were obtained. Female recruits on average expended 3096 ± 9 kcal per day, walked 11.0 ± 0.1 miles per day, and slept 5:43 ± 1:06 h:min per night throughout the 10 weeks of bootcamp. About one-third (35%) of female recruits sustained an injury. In a subset of females that were not taking birth control and had previously been menstruating, 85% experienced cycle dysfunction during boot camp. High levels of physical activity and caloric expenditure, coupled with the stress of a new environment and insufficient sleep, may lead to alterations in female reproductive cycles and musculoskeletal injuries in young USMC recruits.

Sex, gender or occupational psychology: what matters most to preventing heat-related illnesses and improving outcomes for women in ground close combat?

Since the advent of women in ground close combat (WGCC) roles, the impact on women of the attendant risk of heat stress and heat illness has been considered. Much emphasis has been placed on sex differences in thermal physiology. This article considers the application of evidence of sex-associated thermoregulatory variation to the occupational and environmental setting of WGCC, and weighs the relative importance of physiological differences arising from biological sex, and behaviour associated with gender normatives. Quantifying the risk of heat illness to WGCC should draw on data from their real-world occupational context.

Sex differences in response to exercise heat stress in the context of the military environment

Women can now serve in ground close combat (GCC) roles, where they may be required to operate alongside men in hot environments. However, relative to the average male soldier, female soldiers are less aerobically fit, with a smaller surface area (A _D), lower mass (m) with higher body fat and a larger A _D/m ratio. This increases cardiovascular strain, reduces heat exchange with the environment and causes a greater body temperature increase for a given heat storage, although a large A _D/m ratio can be advantageous. Physical employment standards for GCC roles might lessen the magnitude of fitness and anthropometric differences, yet even when studies control for these factors, women sweat less than men at high work rates. Therefore, the average female soldier in a GCC role is likely to be at a degree of disadvantage in many hot environments and particularly during intense physical activity in hot-arid conditions, although heat acclimation may mitigate some of this effect. Any thermoregulatory disadvantage may be exacerbated during the mid-luteal phase of the menstrual cycle, although the data are equivocal. Likewise, sex differences in behavioural thermoregulation and cognition in the heat are not well understood. Interestingly, there is often lower reported heat illness incidence in women, although the extent to which this is influenced by behavioural factors or historic differences in role allocation is unclear. Indeed, much of the extant literature lacks ecological validity and more work is required to fully understand sex differences to exercise heat stress in a GCC context.

Menstrual disturbances in British Servicewomen: A cross-sectional observational study of prevalence and risk factors

Female athletes are at increased risk of menstrual disturbances. The prevalence of menstrual disturbances in British Servicewomen and the associated risk factors is unknown. All women under 45 years in the UK Armed Forces were invited to complete a survey about demographics, menstrual function, eating and exercise behaviors, and psychological well-being. 3,022 women participated; 18% had oligomenorrhoea or amenorrhoea in the last 12 months, 25% had a history of amenorrhoea, and 14% had delayed menarche. Women who sleep ≥ 8 h were at a lower risk of a history of amenorrhoea than women who sleep ≤ 5 h [odds ratio (95% confidence intervals) = 0.65 (0.48, 0.89), p = 0.006]. Women who completed > 10 days of field exercise in the last 12 months were at higher risk of a history of amenorrhoea than women completing no field exercise [1.45 (1.13, 1.85), p = 0.004]. Women at high risk of an eating disorder (FAST score >94) were at higher risk of oligomenorrhoea or amenorrhoea [1.97 (1.26, 3.04), p = 0.002] and history of amenorrhoea [2.14 (1.63, 2.79), p < 0.001]. Women with symptoms of anxiety or depression were at higher risk of a history of amenorrhoea [1.46 (1.20, 1.77) and 1.48 (1.22, 1.79), p < 0.001]. British Servicewomen had a similar prevalence of menstrual disturbances to some endurance athletes. Eating disorders, sleep behaviors, and management of mental health, provide targets for protecting health of the reproductive axis.

Ghrelin Response to Acute and Chronic Exercise: Insights and Implications from a Systematic Review of the Literature

BACKGROUND

Ghrelin is a peptide hormone predominantly produced by the stomach. It exerts a wide range of functions including stimulating growth hormone release and regulating appetite, food intake, and glucose and lipid metabolism. Since physical exercise affects all these aspects, a particular interest is accorded to the relationship between ghrelin and exercise. This systematic review aimed to summarize the current available data on the topic for a better understanding of the relationship.

METHODS

An extensive computerized search was performed in the PubMed and SPORTDiscus databases for retrieving relevant articles. The search contained the following keywords: ghrelin, appetite-related peptides, gastrointestinal peptides, gastrointestinal hormones, exercise, acute exercise, chronic exercise, training, and physical activity. Studies investigating the effects of acute/chronic exercise on circulating forms of ghrelin were included.

RESULTS

The initial search identified 840 articles. After screening, 80 articles were included. Despite a heterogeneity of studies and a variability of the findings, the review suggests that acute exercise suppresses acyl ghrelin production regardless of the participants and the exercise characteristics. Long- and very long-term exercise training programs mostly resulted in increased total and des-acyl ghrelin production. The increase is more noticeable in overweight/obese individuals, and is most likely due to weight loss resulting from the training program.

CONCLUSION

The review suggests that exercise may impact ghrelin production. While the precise mechanisms are unclear, the effects are likely due to blood flow redistribution and weight loss for acute and chronic exercise, respectively. These changes are expected to be metabolically beneficial. Further research is needed for a better understanding of the relationship between ghrelin and exercise.

Reproductive and metabolic adaptation to multistressor training in women

Hypothalamic-pituitary-gonadal (HPG) axis suppression in exercising women can be caused by low energy availability (EA), but the impact of a real-world, multistressor training environment on reproductive and metabolic function is unknown. This study aimed to characterize reproductive and metabolic adaptation in women undertaking basic military training. A prospective cohort study in women undertaking 11-month initial military training (n = 47) was carried out. Dynamic low-dose 1-h gonadotrophin-releasing hormone (GnRH) tests were completed after 0 and 7 mo of training. Urine progesterone was sampled weekly throughout. Body composition (dual X-ray absorptiometry), fasting insulin resistance (homeostatic modeling assessment 2, HOMA2), leptin, sex steroids, anti-Müllerian hormone (AMH), and inhibin B were measured after 0, 7, and 11 mo with an additional assessment of body composition at 3 mo. Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) responses were suppressed after 7 mo (both P < 0.001). Among noncontraceptive users (n = 20), 65% had regular (23-35 days) cycles preenrollment, falling to 24% by 7 mo of training. Of women in whom urine progesterone was measured (n = 24), 87% of cycles showed no evidence of ovulation. There was little change in AMH, LH, and estradiol, although inhibin B and FSH increased (P < 0.05). Fat mass fluctuated during training but at month 11 was unchanged from baseline. Fat-free mass did not change. Visceral adiposity, HOMA2, and leptin increased (all P < 0.001). HPG axis suppression with anovulation occurred in response to training without evidence of low EA. Increased insulin resistance may have contributed to the observed pituitary and ovarian dysfunction. Our findings are likely to represent an adaptive response of reproductive function to the multistressor nature of military training.NEW & NOTEWORTHY We characterized reproductive endocrine adaptation to prolonged arduous multistressor training in women. We identified marked suppression of hypothalamic-pituitary-gonadal (HPG) axis function during training but found no evidence of low energy availability despite high energy requirements. Our findings suggest a complex interplay of psychological and environmental stressors with suppression of the HPG axis via activation of the hypothalamic-pituitary adrenal (HPA) axis. The neuroendocrine impact of nonexercise stressors on the HPG axis during arduous training should be considered.

SEX DIFFERENCES IN THE PHYSICAL PERFORMANCE, PHYSIOLOGICAL, AND PSYCHO-COGNITIVE RESPONSES TO MILITARY OPERATIONAL STRESS

Combat roles are physically demanding and expose service personnel to operational stressors such as high levels of physical activity, restricted nutrient intake, sleep loss, psychological stress, and environmental extremes. Women have recently integrated into combat roles, but our knowledge of the physical, physiological, and psycho-cognitive responses to these operational stressors in women is limited. The aim of this narrative review was to evaluate the evidence for sex-specific physical, physiological, and psycho-cognitive responses to real, and simulated, military operational stress. Studies examining physical and cognitive performance, body composition, metabolism, hypothalamic-pituitary-gonadal axis, and psychological health outcomes were evaluated. These studies report that women expend less energy and lose less body mass and fat-free mass, but not fat mass, than men. Despite having similar physical performance decrements as men during operational stress, women experience greater physiological strain than men completing the same physical tasks, but this may be attributed to differences in fitness. From limited data, military operational stress suppresses hypothalamic-pituitary-gonadal, but not hypothalamic-pituitary-adrenal, axis function in both sexes. Men and women demonstrate different psychological and cognitive responses to operational stress, including disturbances in mood, with women having a higher risk of post-traumatic stress symptoms compared with men. Based on current evidence, separate strategies to maximize selection and combat training are not warranted until further data directly comparing men and women are available. However, targeted exercise training programs may be advisable to offset the physical performance gap between sexes and optimize performance prior to inevitable declines caused by intense military operations.

Effects of different intensities of exercise on folliculogenesis in mice: Which is better?

Objective

Exercise is a risk factor for infertility in women. However, research on the effects of different intensities of exercise on folliculogenesis has not yielded clear results. This study was conducted to analyze the effects of differences in the intensity of exercise on folliculogenesis in mice.

Methods

Nineteen female BALB/c mice (age, 3–4 months; weight, 13–25 g) were randomly divided into four groups: control, mild exercise, moderate exercise, and high-intensity exercise. The mice in the exercise groups engaged in swimming, with additional loads of 3%, 6%, or 9% of body weight, respectively. There were five swimming sessions per week for 4 weeks, with a gradually increasing duration every week. At the end of the treatment, ovarian extraction was carried out and hematoxylin and eosin staining was performed to identify folliculogenesis.

Results

There were significant differences in the number of total follicles between the control and moderate-exercise groups (p=0.036) and between the mild- and moderate-exercise groups (p=0.005). The mean number of primary follicles was higher in the moderate-exercise group than in the mild-exercise group (p=0.006). The mean number of secondary, tertiary, and Graafian follicles did not differ significantly among groups (p≥0.05). However, the number of total follicles and follicles in each phase tended to increase after exercise, especially moderate-intensity exercise.

Conclusion

Exercise of different intensities affected the total number of follicles and primary follicles. The number of follicles of each phase tended to increase after exercise. Moderate-intensity exercise had better effects than other intensities of exercise.

Fasted plasma asprosin concentrations are associated with menstrual cycle phase, oral contraceptive use and training status in healthy women

Purpose

Asprosin, an orexigenic hormone that stimulates hepatic glucose release, is elevated in insulin resistance and associated with obesity. Plasma asprosin concentrations may also be related to female sex hormone levels; higher levels are reported in women with polycystic ovary syndrome (PCOS) but this may be related to peripheral insulin resistance also associated with PCOS. Clarification of female-specific factors influence on the plasma asprosin response is crucial for studies investigating asprosin. Therefore, this study determined the association of menstrual phase, oral contraceptive (OC) use (as a pharmacological influence on sex hormone levels) and training status (as a physiological influence on sex hormone levels) on plasma asprosin levels in pre-menopausal women.

Methods

Fasting plasma asprosin, 17β-estradiol (E2) and progesterone, were assessed in 32 healthy untrained and trained women with regular menstrual cycles (non-OC; n = 8 untrained, n = 6 trained) or using OC (n = 10 untrained, n = 8 trained) during early follicular, late follicular and mid-luteal menstrual phases (or the time-period equivalent for OC users).

Results

Asprosin was lower in OC (0.75 ± 0.38 ng mL⁻¹) than non-OC users (1.00 ± 0.37 ng mL⁻¹; p = 0.022). Across a cycle, asprosin was highest in the early follicular equivalent time-point in OC users (0.87 ± 0.37 ng mL⁻¹) but highest in the mid-luteal phase in non-OC users (1.09 ± 0.40 ng mL⁻¹). Asprosin concentrations varied more across a cycle in untrained than trained women, with higher concentrations in the early follicular phase compared to the late follicular and mid-luteal (training status-by-menstrual phase interaction p = 0.028).

Conclusion

These findings highlight the importance of considering OC use, menstrual cycle phase and to a lesser extent training status when investigating circulating asprosin concentrations in females.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00421-020-04570-8.

"A LEAP 2 conclusions? Targeting the ghrelin system to treat obesity and diabetes"

BACKGROUND

The hormone ghrelin stimulates food intake, promotes adiposity, increases body weight, and elevates blood glucose. Consequently, alterations in plasma ghrelin levels and the functioning of other components of the broader ghrelin system have been proposed as potential contributors to obesity and diabetes. Furthermore, targeting the ghrelin system has been proposed as a novel therapeutic strategy for obesity and diabetes.

SCOPE OF REVIEW

The current review focuses on the potential for targeting ghrelin and other proteins comprising the ghrelin system as a treatment for obesity and diabetes. The main components of the ghrelin system are introduced. Data supporting a role for the endogenous ghrelin system in the development of obesity and diabetes along with data that seemingly refute such a role are outlined. An argument for further research into the development of ghrelin system-targeted therapeutic agents is delineated. Also, an evidence-based discussion of potential factors and contexts that might influence the efficacy of this class of therapeutics is provided.

MAJOR CONCLUSIONS

It would not be a "leap to" conclusions to suggest that agents which target the ghrelin system - including those that lower acyl-ghrelin levels, raise LEAP2 levels, block GHSR activity, and/or raise desacyl-ghrelin signaling - could represent efficacious novel treatments for obesity and diabetes.

Energy Deficiency in Soldiers: The Risk of the Athlete Triad and Relative Energy Deficiency in Sport Syndromes in the Military

Military personnel experience energy deficit (total energy expenditure higher than energy intake), particularly during combat training and field exercises where exercising energy expenditures are high and energy intake is reduced. Low energy availability (energy intake minus exercising energy expenditure expressed relative to fat free mass) impairs endocrine function and bone health, as recognized in female athletes as the Female Athlete Triad syndrome. More recently, the Relative Energy Deficiency in Sport (RED-S) syndrome encompasses broader health outcomes, physical and cognitive performance, non-athletes, and men. This review summarizes the evidence for the effect of low energy availability and energy deficiency in military training and operations on health and performance outcomes. Energy availability is difficult to measure in free-living individuals but doubly labeled water studies demonstrate high total energy expenditures during military training; studies that have concurrently measured energy intake, or measured body composition changes with DXA, suggest severe and/or prolonged energy deficits. Military training in energy deficit disturbs endocrine and metabolic function, menstrual function, bone health, immune function, gastrointestinal health, iron status, mood, and physical and cognitive performance. There are more data for men than women, and little evidence on the chronic effects of repeated exposures to energy deficit. Military training impairs indices of health and performance, indicative of the Triad and RED-S, but the multi-stressor environment makes it difficult to isolate the independent effects of energy deficiency. Studies supplementing with energy to attenuate the energy deficit suggest an independent effect of energy deficiency in the disturbances to metabolic, endocrine and immune function, and physical performance, but randomized controlled trials are lacking.

Endogenous opiates and behavior: 2017

This paper is the fortieth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2017 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Effects of high-intensity interval training and nutrition advice on cardiometabolic markers and aerobic fitness in adolescent girls with obesity

The aim of the study was to compare the effects of high-intensity interval training (HIIT) and nutrition advice on cardiometabolic biomarkers, hormonal parameters, and cardiorespiratory fitness in adolescent girls with obesity. Adolescent girls with obesity (n = 44, aged 13-19 years) were randomized into a 12-week intervention as follows: (i) dietary advice and HIIT (n = 22), and (ii) dietary advice only (n = 22). The concentration of biomarkers of inflammation, biochemical and hormonal testing, oral glucose tolerance test, cardiorespiratory fitness, physical activity levels, and nutrition were assessed. After a 3-month intervention, the diet+HIIT group significantly increased insulin sensitivity index (-0.34 ± 1.52 vs. 1.05 ± 3.21; p = 0.001) and work load (0.6 ± 11.3 W vs. 14.6 ± 20.2 W; p = 0.024) and decreased glucose area under the curve (-0.29 ± 4.69 vs. -0.98 ± 4.06; p = 0.040), insulin area under the curve (-9.65 ± 117.9 vs. -98.7 ± 201.8; p = 0.003), and high-sensitivity C-reactive protein (hs-CRP) (0.12 ± 1.92 mg/L vs. -1.47 ± 3.67 mg/L; p = 0.039) in comparison with the diet group. Regarding within-group changes, both groups had significant improvements in body mass index (BMI), BMI-standard deviation score, body fat percentage, and systolic blood pressure. Positive impact on waist circumference, waist circumference/height ratio, diastolic blood pressure, hs-CRP, work load, maximal heart rate, and resting heart rate was observed only after the diet+HIIT intervention. No significant change was noted in peak oxygen uptake, lipid profile, and hormonal parameters between groups after intervention. Novelty HIIT and nutrition advice increased insulin sensitivity and decreased BMI, body fat, systolic blood pressure, and diastolic blood pressure. Nutrition advice decreased BMI, body fat, and systolic blood pressure in adolescent girls with obesity.

Neuropeptide Y and dipeptidyl peptidase IV in normally cycling and postmenopausal women: A prospective pilot study

The purpose was to investigate changes in neuropeptide Y (NPY) protein and dipeptidyl peptidase IV (DPP-IV) activity in the plasma and saliva in normally cycling women and women after menopause. We recruited 7 cycling women and 7 postmenopausal women for a cross-sectional, prospective pilot study. Blood via venipuncture and saliva samples were taken at each point in the menstrual cycle (premenopausal) or once per week (postmenopausal) for 2 months. Blood and saliva were analyzed for estrogen, NPY using ELISA and DPP-IV activity using a fluorometric assay. Plasma β-estradiol was an average of 96.45 ± 57.04 pg/mL over 2 cycles in the premenopausal group and 1.72 ± 0.35 pg/mL over 2 months in the postmenopausal group (P < .05). In the cycling group, there were no significant differences in saliva or plasma NPY or DPP-IV over the cycle. For the postmenopausal group, salivary NPY and DPP-IV did not change over 2 months. Plasma NPY was lowest in the middle 2 weeks (average: 0.52 ± 0.10 ng/mL) compared to the first and fourth weeks (average of week 1 and 4: 0.60 ± 0.14 ng/mL; P < .05). Plasma NPY in postmenopausal women was higher overall (0.56 ± 0.13 ng/mL) compared to cycling women (0.30 ± 0.11 ng/mL; P < .05). Plasma DPP-IV activity was unchanged by time in the postmenopausal group. Saliva DPP-IV and saliva NPY in the cycling group had a significant negative correlation (R = -0.95; P < .05). We found that saliva measures of NPY and DPP-IV activity appear to be poor estimates of plasma concentrations and activities, but a larger sample size is required to conform this. Differences in plasma NPY concentrations between the groups and the relationship between salivary NPY and DPP-IV suggests that there may be some unique differences between these groups.

Ghrelin mediates exercise endurance and the feeding response post-exercise

Objective

Exercise training has several well-established health benefits, including many related to body weight, appetite control, and blood glucose homeostasis. However, the molecular mechanisms and, in particular, the hormonal systems that mediate and integrate these beneficial effects are poorly understood. In the current study, we aimed to investigate the role of the hormone ghrelin and its receptor, the growth hormone secretagogue receptor (GHSR; ghrelin receptor), in mediating the effects of exercise on food intake and blood glucose following exercise as well as in regulating exercise endurance capacity.

Methods

We used two mouse models of treadmill running to characterize the changes in plasma ghrelin with exercise. We also assessed the role of the ghrelin system to influence food intake and blood glucose after exercise, exercise endurance, and parameters potentially linked to responses to exercise. Mice lacking GHSRs (GHSR-null mice) and wild-type littermates were studied.

Results

An acute bout of exercise transiently elevated plasma acyl-ghrelin. Without the action of this increased ghrelin on GHSRs (as in GHSR-null mice), high intensity interval exercise markedly reduced food intake compared to control mice. The effect of exercise to acutely raise blood glucose remained unmodified in GHSR-null mice. Exercise-induced increases in plasma ghrelin positively correlated with endurance capacity, and time to exhaustion was reduced in GHSR-null mice as compared to wild-type littermates. In an effort to mechanistically explain their reduced exercise endurance, exercised GHSR-null mice exhibited an abrogated sympathoadrenal response, lower overall insulin-like growth factor-1 levels, and altered glycogen utilization.

Conclusions

Exercise transiently increases plasma ghrelin. GHSR-null mice exhibit decreased food intake following high intensity interval exercise and decreased endurance when submitted to an exercise endurance protocol. These data suggest that an intact ghrelin system limits the capacity of exercise to restrict food intake following exercise, although it enhances exercise endurance.

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High intensity exercise transiently increases plasma ghrelin.

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Without ghrelin action on its receptors (growth hormone secretagogue receptors), exercise markedly reduces food intake.

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An intact ghrelin system enhances exercise endurance.