Function Of Cycle Phase Research Articles

Pedal Reaction Forces and Electromyography Responses Indicate Eccentric Contractions During Motorized Cycling in a Rat Model of Incomplete Spinal Cord Injury.

Motorized cycling (MC) is utilized as an alternative to traditional exercise in individuals who are unable to perform voluntary movements post-spinal cord injury. Although rodent models of MC often show more positive outcomes when compared with clinical studies, the cause of this difference is unknown. We postulate that biomechanical differences between rats and humans may contribute to this discrepancy. To begin to test this theory, we examined pedal reaction forces and electromyography (EMG) of hindlimb muscles as a function of cycle phase and cadence in a rat model of MC. We found that higher cadences (≥30 RPM) increased EMG and force, with higher forces observed in animals with contusion injuries as compared with transections. To further investigate the forces, we developed a technique to separate rhythmic (developed with the motion of the pedals) from nonrhythmic forces. Rhythmic forces resulted from induced eccentric muscle contractions that increased (amplitude and prevalence) at higher cadences, whereas nonrhythmic forces showed the opposite pattern. Our results suggest that muscle activity during MC in rats depends on the stretch reflex, which, in turn, depends on the rate of muscle lengthening that is modulated by cadence. Additionally, we provide a framework for understanding MC that may help translate results from rat models to clinical use in the future.

Variation in sociosexuality across natural menstrual cycles: Associations with ovarian hormones and cycle phase

Abstract The psychological construct of sociosexuality—one's sexual openness or propensity to engage in uncommitted sexual relationships—has been broadly examined within numerous cultures and mating contexts. Although there is some evidence suggesting that components of sociosexuality, namely behavior, desire and attitude, change within-person, relatively little research has investigated potential sources of such variation. The aim of our study was to explore if the individual components of sociosexuality change across the menstrual cycle, either as a function of cycle phase or ovarian hormones. One hundred and two naturally cycling women, both single and in a committed relationships, completed questions from the the SOI-R (Sociosexuality Revised) questionnaire three times during a menstrual cycle, scheduled to coincide with their early follicular, peri-ovulatory, and luteal phases. Women provided saliva samples and performed luteinizing hormone tests to distinguish between ovulatory and anovulatory cycles. Women reported slightly more openness to uncommitted sexual relationships during the peri-ovulatory session, but significant differences were restricted only to women who exhibited the luteinizing hormone surge. Ovarian hormone concentrations within cycles significantly predicted SOI Attitude and Desire scores, with estradiol positively related, and progesterone negatively related to openness to uncommitted sexuality. These effects were generally modest in size. The results of this study suggest that sociosexuality can vary within short periods of time, such as a single menstrual cycle.

Menstrual cycle phase predicts women's hormonal responses to sexual stimuli

A robust body of research has demonstrated shifts in women's sexual desire and arousal across the menstrual cycle, with heightened desire and arousal coincident with heightened probability of conception (POC), and it is likely that ovarian hormones modulate these shifts. However, studies in which women are exposed to audiovisual sexual stimuli (AVSS) at high POC (mid-follicular) and low POC (luteal) phases have failed to detect significant differences in genital or subjective arousal patterns based on menstrual cycle phase. Here, we tested whether hormonal responsivity to AVSS differs as a function of cycle phase at testing, and whether phase during which participants were first exposed to AVSS influences hormonal responsivity in subsequent test sessions. Twenty-two naturally cycling heterosexual women were exposed to AVSS during the follicular and luteal phases, with phase at first test session counterbalanced across participants. Salivary samples were collected before and after AVSS exposure. Estradiol increased significantly during both follicular and luteal phase sessions, and increases were higher during the follicular phase. Testosterone (T) increased significantly only during the follicular phase session, while progesterone (P) did not change significantly during either cycle phase. Session order and current cycle phase interacted to predict P and T responses, such that P and T increased during the follicular phase in women who were first tested during the luteal phase. These data suggest that menstrual cycle phase influences hormonal responsivity to AVSS, and contribute to a growing body of clinical and empirical literature on the neuroendocrine modulators of women's sexuality.

The Impact of Menstrual Cycle Phase on Economic Choice and Rationality.

It is well known that hormones affect both brain and behavior, but less is known about the extent to which hormones affect economic decision-making. Numerous studies demonstrate gender differences in attitudes to risk and loss in financial decision-making, often finding that women are more loss and risk averse than men. It is unclear what drives these effects and whether cyclically varying hormonal differences between men and women contribute to differences in economic preferences. We focus here on how economic rationality and preferences change as a function of menstrual cycle phase in women. We tested adherence to the Generalized Axiom of Revealed Preference (GARP), the standard test of economic rationality. If choices satisfy GARP then there exists a well-behaved utility function that the subject’s decisions maximize. We also examined whether risk attitudes and loss aversion change as a function of cycle phase. We found that, despite large fluctuations in hormone levels, women are as technically rational in their choice behavior as their male counterparts at all phases of the menstrual cycle. However, women are more likely to choose risky options that can lead to potential losses while ovulating; during ovulation women are less loss averse than men and therefore more economically rational than men in this regard. These findings may have market-level implications: ovulating women more effectively maximize expected value than do other groups.

Comment: Wood et al.’s (2014) Speculations of Inappropriate Research Practices in Ovulatory Cycle Studies

Wood, Kressel, Joshi, and Louie (2014) meta-analyzed studies examining changes in women’s mate preferences as a function of cycle phase, and claimed to find little evidence for shifts, contrary to Gildersleeve, Haselton, and Fales’s (2014a) meta-analysis. This commentary concerns specific speculations Wood et al. made about particular researchers analyzing data multiple ways, capitalizing on chance and thereby inflating the Type I error rate. In so doing, Wood et al. misconstrued a key article explaining the high fertility period, misrepresented studies, and presented no supportive evidence. The corrosive effects of inappropriate research practices on scientific literatures are concerning. So too are unsubstantiated speculations of them.

Regional gray matter volume differences and sex-hormone correlations as a function of menstrual cycle phase and hormonal contraceptives use

During the menstrual cycle, hormone-driven functional and morphological changes occur in the female brain. The influence of hormonal contraceptives on these changes has received only little attention in the medical literature. The purpose of our study is to measure regional gray matter volume changes as a function of the cycle phase and use of hormonal contraceptives, in relation to blood concentrations of sex hormones. We performed a prospective study in 30 healthy young women; 15 women had a natural menstrual cycle and 15 were using monophasic combined hormonal contraceptives. MRI examinations were acquired at 2 specific time-points in the cycle (follicular and luteal phase). MRI studies included a T1-weighted, isotropic, high-resolution 3-D gradient echo acquisition, for the purpose of performing voxel based morphometry. Peripheral venous blood samples were obtained to determine concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol, and progesterone. We found a highly significant negative correlation of regional gray matter volume in the anterior cingulate cortex with estradiol concentrations. To the best of our knowledge, this result has not been described before, and was only present in the natural cycle group, not in women using hormonal contraceptives. The anterior cingulate cortex is involved in emotion processing and there is literature describing behavioral alternations with changing hormone levels. Our findings provide a structural, morphological basis to support these data. Therefore, we advise neuroscientists to take into account the menstrual cycle phase and use of hormonal contraceptives, in order to avoid obtaining heterogeneous data sets, leading to a significant loss of accuracy and precision.

Symptomatology and energy intake during the menstrual cycle in smoking women.

This study extends our understanding of smoking behavior, withdrawal, and premenstrual symptomatology in smoking women, as well as energy intake as a function of cycle phase. Thirty-two women age 18 to 40 years, smoking ad lib, were followed for an average of two menstrual cycles with hormonal verification. Withdrawal and premenstrual symptomatology as well as energy intake were reported during the follicular (F), luteal (L), and late luteal (LL) cycle phases. Both premenstrual symptomatology and withdrawal symptomatology were higher during the LL phase. Subject response on measurements of craving, irritability, restlessness, increased appetite, and depressed mood tended to be higher in the LL phase. Energy intake did not vary as a function of cycle phase. Participants perceived that they smoked more and had increased appetite in the LL phase but related measurements did not confirm this. Premenstrual and withdrawal symptoms are highly correlated and one needs to be cautious in interpreting cycle effects on withdrawal. Overall symptomatology seems to be lower during the F phase, indicating that this may be a more opportune time for women to quit smoking.

Magnesium and zinc status during the menstrual cycle

The effect of menstrual cycle phases on the indexes of magnesium and zinc status was assessed in five normally menstruating women. Plasma concentrations of magnesium and zinc and the magnesium and zinc content of red blood cells and peripheral blood mononuclear cells were measured for 3 or 5 days per week during three menstrual cycles. The cycles were divided into four phases: menses, follicular, ovulatory, and luteal. Plasma magnesium concentrations were highest during menses and then gradually declined, reaching the lowest point during the ovulatory phase. This was followed by a rise during the luteal phase. Plasma zinc concentrations were higher during menses and the follicular phase and then dropped during the ovulatory and luteal phases. Both the magnesium and zinc content of red blood cells and mononuclear cells remained constant over the course of the study and did not change significantly as a function of cycle phase. This study provides evidence that plasma magnesium and zinc concentrations fluctuate during the menstrual cycle in a phase-related fashion in normally menstruating women. Whether these changes are hormonally mediated or reflect metabolic changes will require further study.

Psychoendocrinology of the menstrual cycle: I. Enjoyment of daily activities and moods.

Thirty-three women participated in a study of the relationship between moods and enjoyment of activities during the menstrual cycle. All subjects had normal cycles and were screened for psychological health. None were taking oral contraceptives. Each subject filled out daily the Profile of Mood States (POMS) and the Social--Sexual Activities Log (SAAL). They also completed the Moos Menstrual Distress Questionnaire (MDQ) once a month. The SSAL was developed as part of this research in order to provide a means of assessing subjective enjoyment of daily activities. SSAL items were developed from semistructural individual interviews and assessed behavior across eight different categories. Results suggest that the SSAL is a reliable self-report instrument. Although there were no changes in either moods or enjoyment of activities as a function of cycle phase with either the POMS or the SSAL, scores on the MDQ showed the usual cycle-related differences. These findings raise questions concerning the validity of retrospective methods in general, and of the MDQ in particular, as techniques for assessment of personal distress during the menstrual cycle. Equally important, the results suggest that when changes in psychological states are assessed concurrently during the menstrual cycle, the fluctuations observed in a healthy population are minimal.