The interrelationships among sex hormone concentrations, motoneuron excitability, and anterior tibial displacement in women and men

Neuromuscular and gene signaling responses to passive whole-body heat stress in young adults

This study aimed to investigate whether acute passive heat stress 1) decreases muscle Maximal Voluntary Contraction (MVC); 2) increases peripheral muscle fatigue; 3) increases spinal cord excitability, and 4) increases key skeletal muscle gene signaling pathways in skeletal muscle. Examining the biological and physiological markers underlying passive heat stress will assist us in understanding the potential therapeutic benefits. MVCs, muscle fatigue, spinal cord excitability, and gene signaling were examined after control or whole body heat stress in an environmental chamber (heat; 82 °C, 10% humidity for 30 min). Heart Rate (HR), an indicator of stress response, was correlated to muscle fatigue in the heat group (R = 0.59; p < 0.05) but was not correlated to MVC, twitch potentiation, and H reflex suppression. Sixty-one genes were differentially expressed after heat (41 genes >1.5-fold induced; 20 < 0.667 fold repressed). A strong correlation emerged between the session type (control or heat) and principal components (PC1) (R = 0.82; p < 0.005). Cell Signal Transduction, Metabolism, Gene Expression and Transcription, Immune System, DNA Repair, and Metabolism of Proteins were pathway domains with the largest number of genes regulated after acute whole body heat stress. Acute whole-body heat stress may offer a physiological stimulus for people with a limited capacity to exercise.

Neurophysiologic evaluation of patients with cervical spondylotic myelopathy

Background

Cervical spondylotic myelopathy (CSM) is a neurodegenerative disease caused by repetitive spinal cord damage that has resulted in significant clinical morbidity. The clinical evaluation of signs and symptoms, as well as neuroimaging and several neurophysiological tests, are used to make the diagnosis.

Objectives

To investigate changes in the cutaneous silent period (CuSP), cortical silent period (CoSP), and H-reflex in CSM patients, and to correlate these tests with the Japanese Orthopedic Association (JOA) score and Nurick’s grading, as well as to determine the diagnostic value of each of them.

Methods

Twenty patients (14 males and 6 females) with CSM were clinically diagnosed and documented by magnetic resonance imaging (MRI), and they were paired with another 20 healthy volunteers (13 males and 7 females) as a control group. CuSP, CoSP, and H-reflex tests were performed on both groups.

Results

In CSM patients, CuSP latency and duration are substantially longer and shorter in CSM patients, respectively. The degree of changes in CuSP latency is well correlated with the severity of the disease. Further, CoSP duration is significantly shortened. The H-reflex parameters did not differ significantly between the patient and control groups.

Conclusion

The shortened CoSP’s duration and the prolonged CuSP's latency suggest malfunction of the inhibitory and excitatory circuits in the spinal cord. The CuSP is more sensitive and specific than the CoSP in the diagnosis of a patient with CSM.

Effect of Low Versus High-Heeled Footwear on Spinopelvic Alignment at Different Phases of Menstrual Cycle in Young Adult Women: A Biopsychosocial Perspective

High-heeled shoes adversely affect spinal curvature, increase the risk of low back pain, and disturb the normal gait pattern. The purpose of this study was to examine, from a biopsychosocial point of view, the combined effect of wearing two different heel heights and of hormonal oscillation throughout different phases of the menstrual cycle on spinopelvic alignment. Notably, 70 females with an average age of 20.42 ± 1.51 years participated in this study, wearing each female two different heel heights as follows: low (2.5 cm) and high (7 cm). Spinopelvic alignment was evaluated by rasterstereography formetric 3D analysis during early follicular, ovulatory, and mid-luteal phases of the menstrual cycle. Statistical analysis showed that there was no significant difference (p > 0.05) on spinopelvic alignment [kyphotic angle (KA), trunk inclination (TI), and pelvic inclination] between wearing low- or high-heeled shoes during early follicular, ovulatory, and mid-luteal phases of the menstrual cycle. Considering that high-heeled shoes are traditionally associated with femininity, body image, beauty, and charm, this research has important biopsychosocial implications that should be explored in detail in future studies.

The Menstrual Cycle May Affect Anterior Knee Laxity and the Rate of Anterior Cruciate Ligament Rupture: A Systematic Review and Meta-Analysis

BACKGROUND

Women have a higher risk of anterior cruciate ligament (ACL) tears than men, the causes of which are multifactorial. The menstrual cycle and its hormonal effect on the knee may contribute to knee laxity and ACL injury. This work reviewed published studies examining the effects of the phases of the menstrual cycle on anterior knee laxity and the rate of ACL tears.

METHODS

A systematic review with meta-analysis and meta-regression was performed. Studies with data comparing the menstrual cycle phase with ACL injury or anterior knee laxity were included for analysis. Data with regard to patient demographic characteristics, anterior knee laxity, ACL injury, and menstrual cycle phases were extracted from the included studies.

RESULTS

In this study, 1,308 search results yielded 396 articles for review, of which 28 met inclusion criteria. Nineteen studies of knee laxity with 573 combined subjects demonstrated a mean increase in laxity (and standard deviation) of 0.40 ± 0.29 mm in the ovulatory phase compared with the follicular phase and a mean increase in laxity of 0.21 ± 0.21 mm in the luteal phase compared with the follicular phase. Nine studies examining ACL tears with 2,519 combined subjects demonstrated a decreased relative risk (RR) of an ACL tear in the luteal phase compared with the follicular and ovulatory phases combined (RR, 0.72 [95% confidence interval, 0.56 to 0.89]). There were no differences in ACL tear risk between any of the other phases.

CONCLUSIONS

An increased risk of an ACL tear does not appear to be associated with periods of increased laxity in this meta-analysis. Although this suggests that hormonal effects on an ACL tear may not be directly related to increases in knee laxity, the methodologic heterogeneity between published studies limits the conclusions that can be drawn and warrants further investigation.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Sex differences in soleus muscle H-reflex and V-wave excitability

NEW FINDINGS

 What is the central question of this study? How do H-reflex and V-wave excitability compare between men and women engaging in similar levels of physical activity?  What is the main finding and its importance? H-reflex excitability is lower in women than in men because of their greater level of antagonist co-activation during sustained plantar flexion isometric exercise. In addition, supraspinal drive is similar between men and women independently of their differences in H-reflex excitability and antagonist muscle co-activation.

ABSTRACT

We compared H-reflex and V-wave excitability between men and women engaging in similar levels of physical activity. We also explored whether differences in antagonist muscle co-activation between sexes might partially explain sexual dimorphism in the excitability of the H-reflex and V-wave. Fifty-seven young participants were included (29 men: 21.7 ± 2.3 years; 28 women: 22.4 ± 3.3 years). Soleus M- and H-recruitment curves were constructed on a tonic background muscle activation. V-waves were elicited during maximal voluntary contraction (MVC). Besides being stronger than women, men achieved greater H_max /M_max values and presented a steeper slope of the ascending limb of the H-reflex recruitment curve (P < 0.05). The current intensity required to elicit H_max was lower for men (P < 0.05). The co-activation of the tibialis anterior muscle during the sustained plantar flexions was greater in women (ratio between tibialis and soleus normalized EMG: 20.5 vs. 8.3%, P < 0.05). Covariance analysis showed that sexual dimorphism in H-reflex excitability was dissipated when controlling for antagonist co-activation. V-wave normalized amplitude was similar between sexes even after controlling for the effects of H_max /M_max and antagonist co-activation as covariates. Thus, women exhibit lower H-reflex excitability than men and this is dependent on their higher level of antagonist muscle co-activation. While sex differences in antagonist co-activation persist during MVCs, this is not the case for V-wave normalized amplitude. Thus, although the efficacy of the transmission between Ia afferent fibres to α-motoneurons is lower in women because of a greater level of antagonist co-activation, our findings are consistent with similar supraspinal drive between sexes.

Ground Reaction Forces Are Predicted with Functional and Clinical Tests in Healthy Collegiate Students

Increased vertical and posterior ground reaction forces (GRFs) are associated with anterior cruciate ligament (ACL) injury. If a practical means to predict these forces existed, ACL injury risk could be attenuated. Forty-two active college-age individuals (21 females, 20.66 ± 1.46 y, 70.70 ± 2.36 cm, 82.20 ± 7.60 kg; 21 males, 21.57 ± 1.28 y, 65.52 ± 1.87 cm, 64.19 ± 9.05 kg) participated in this controlled laboratory study. GRFs were ascertained by having the subjects perform a unilateral landing task onto a force plate. Several clinical measures (Fat Free Mass (FFM), dorsiflexion passive range of motion (DPROM), isometric peak force of the lateral hip rotators, knee flexor/extensor peak force ratio (H:Q), the completion of the overhead deep squat), two functional tests (Margaria–Kalamen, Single Leg Triple Hop (SLTH)), and sex served as the predictor variables. Regression models to predict the GRFs normalized to the FFM (nGRFz, nGRFy) were generated. nGRFz was best predicted with a linear regression equation that included SLTH and DPROM (adjusted R² = 0.274; p = 0.001). nGRFy was best predicted with a linear regression equation that included H:Q, FFM, and DPROM (adjusted R² = 0.476; p < 0.001). Simple clinical measures and functional tests explain a small to moderate amount of the variance associated with the FFM normalized vertical and posterior GRFs in active college-age individuals.

Sex Differences in Lower Limb Proprioception and Mechanical Function Among Healthy Adults

Twenty-four healthy adults, including 12 females and 12 males, participated in the study. Each female participant completed three trials in three different phases of one menstrual cycle, which included follicular, ovulatory, and luteal phases. The study aimed to investigate whether there is any difference in joint kinetic sense, neuromuscular coordination, and isokinetic muscle strength (a) between healthy males and females at different phases of the menstrual cycle and (b) between females at different phases of the menstrual cycle. The outcome measures included the number of jumps in the square-hop test and ankle and knee proprioception, which were assessed by an electric-driven movable frame rotated at 0.4 deg/s and isokinetic muscle strength measured by a computerized dynamometer (Biodex). For the square-hop test (p = .006), ankle dorsiflexion/plantar flexion (p < .05), knee flexion/extension (p < .05), the relative peak torque of the isokinetic muscle strength at the 60° and 180° knee flexion/extension (p < .001), and the 30° and 120° ankle plantar flexion/dorsiflexion (p < .05) between females and males showed significant differences. For the females at different phases of the menstrual cycle, significant differences were found on ankle dorsiflexion (p = .003), plantar flexion (p = .023), knee extension (p = .029), the square-hop test (p = .036), and relative peak torque of isokinetic muscle strength at 180° knee flexion (p = .029). This study demonstrated that there are sex differences in lower limb proprioception and mechanical function. Females at ovulatory and luteal phases have better lower limb proprioception than at the follicular phase.

Comparison of some intrinsic risk factors of shoulder injury in three phases of menstrual cycle in collegiate female athletes

OBJECTIVES

present study aims to investigate the changes in the shoulder joint stability factors during the menstrual cycle.

DESIGN

cross-sectional study; SETTING: laboratory.

PARTICIPANTS

15 healthy collegiate female athletes with normal menstrual cycles.

MAIN OUTCOME MEASURES

shoulder strength, proprioception, laxity and functional stability were the primary outcomes. Participants were assessed in three phases (mense, ovulation, midluteal (day 21) by 4 different categories of tests, each designed for a different factor. Shapiro-Wilk Test was used to determine normality of data, ANOVA and Friedman Test were used to compare results. Significance level and alpha were considered 95 percent and ≥0.05, respectively. Data shown a relation between proprioception, strength and menstrual cycle.

RESULTS

shoulder strength was significantly increased in ovulation phase compared to other phases (p < 0.5) (effect size >0.14). Proprioception was significantly decreased in luteal phase than in mense and ovulation phases (p < 0.5) (effect size >0.14). Finally, ligament laxity and functional stability showed no change in all phases (p < 0.5).

CONCLUSION

Menstrual cycle and sexual hormones affect muscle strength and proprioception of shoulder joint, but have no effect on ligament laxity and functional stability.

Associations between the menstrual cycle, lifestyle factors and clinical assessment of the ocular surface: a prospective observational study

BACKGROUND

Little is known about the ocular surface changes over the menstrual cycle in young women and the interactions with lifestyle factors. Therefore, the purpose of this study was to explore the associations between modifiable lifestyle factors and menstrual cycle phases on the ocular signs and symptoms of dry eye in young healthy women.

METHODS

This was a prospective 1-month observational study. Thirty young healthy women with regular, 24 to 32-day menstrual cycles were recruited. Participants attended three visits at day 7, 14, and 21 (± 1) of their menstrual cycle. At baseline, general health questionnaire was conducted. At each visit, symptomology was quantified using Ocular Surface Disease Index (OSDI) and overall ocular comfort (OOC, visual analogue scale). Ocular signs were assessed using Efron scales, tear break-up time (TBUT) and phenol red thread (PRT). Pearson's correlation was used to determine associations between variables at each visit.

RESULTS

A total of 26 participants (mean age = 22.3 ± 3.7 years) with an average menstrual cycle of 28.3 ± 1.3 days completed the 3 visits. The interaction between signs/symptoms and lifestyle factors changed over the cycle. At the follicular phase (day 7), lifestyle factors such diet and levels of stress were correlated with PRT and OSDI, (r = - 0.4, p = 0.022; r = 0.4, p = 0.045 respectively). At the ovulation phase (day 14), the general health score was correlated with OOC scores (r = 0.4, p = 0.047). At day 14, exercise frequency correlated with PRT (r = - 0.4, p = 0.028) and caffeine intake was positively correlate with both; TBUT (r = 0.5, p = 0.020) and PRT (r = 0.5, p = 0.014). At the luteal phase (day 21), we found no correlations between lifestyle factors and dry eye signs or symptoms.

CONCLUSIONS

The associations between lifestyle factors and objective and subjective ocular surface assessment appeared to be more pronounced during the ovulation phase of the menstrual cycle compared to the follicular and luteal phases. Misalignment of these factors with the ocular health during the luteal phase could be attributed to central sensitization and changes in levels of luteinising hormone. Natural hormonal changes during menstrual cycle should be considered for diagnosis and treatment of dry eye in young healthy women.

Revision ACL reconstruction using quadriceps or hamstring autografts leads to similar results after 4 years: good objective stability but low rate of return to pre-injury sport level

PURPOSE

Due to the increased importance of revision ACL reconstruction, this study aims to evaluate the outcome 4 years after the surgery, compare two revision strategies and identify factors that influence the results.

METHODS

Seventy-nine patients who received a revision ACL reconstruction were retrospectively evaluated. All patients were assessed with an average follow-up of 4.4 years (range 3.3-5.5 years). The results of patients treated with a quadriceps autograft were compared with those treated with a hamstring autograft.

RESULTS

Ninety-seven percent of patients had a KT-1000 side-to-side difference of ≤ 5 mm (mean 1.7 ± 2.0 mm). Pivot-shift test was absent or minor in 95%. In the SLTH-test, 70% of patients reached 90% of the contralateral side. The mean Lysholm score on follow-up was 83 ± 12 (56% excellent/good). The mean IKDC 2000 subjective evaluation score was 81 ± 14 (58% normal/almost normal). The median Tegner activity score was 6 (range 3-10), a median of 2 levels worse than before the first injury. Return to sport rate was 89% but only 34% of patients reached their pre-injury sport level. Most common cause for this reduction was fear of another injury. Three patients suffered a re-rupture. Patients with a hamstring autograft performed pivoting sports more often, but had worse pivot-shift results compared to those with a quadriceps autograft. No significant influence was seen for other parameters. Young, male patients with a high activity level and no chondral damage had the best results.

CONCLUSION

Through revision ACL reconstruction, the goal of stabilizing the knee can be achieved in the majority of patients. However, a good function and a high activity level are significantly less common in these patients. The main reason for this is fear of a renewed ACL-injury. Both quadriceps and hamstring autografts were able to achieve a good outcome. Young, male, patients with a normal BMI, a high activity level and without cartilage damage seem to benefit the most from revision ACL surgery. The discrepancy between the good laxity restoration and the lower activity rate should therefore be a main point in clinical counseling when deciding for or against revision ACL-Reconstruction.

LEVEL OF EVIDENCE

III.

Changes in Knee Vastii Muscle Activity in Women with Patellofemoral Pain Syndrome During the Menstrual Cycle

BACKGROUND

Changes in hormonal levels during the menstrual cycle are known to affect muscle electromyographic (EMG) activity, but no studies have investigated the effect of hormonal changes on the EMG activity of muscles around the knee in patients with patellofemoral pain syndrome (PFPS).

OBJECTIVE

To evaluate the EMG activity of the vastus medialis obliquus (VMO) and vastus lateralis (VL) muscles during toe rise and heel rock tasks in different phases of the menstrual cycle in women with PFPS.

DESIGN

Cross sectional study.

SETTING

Rehabilitation Research Center at the School of Rehabilitation Sciences of Shiraz University of Medical Sciences.

PARTICIPANTS

Ten women with PFPS between 18 and 40 years of age.

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURES

The VL/VMO amplitude ratio and differences between onset (onset VL-onset VMO) of vastii muscle activity were measured in the affected limb during rise and rock tasks in the follicular and ovulatory phases of the menstrual cycle. The signals were analyzed with MATLAB software.

RESULTS

During both tasks, there were no significant changes in onset differences in vastii muscles between the ovulatory and follicular phases. However, the amplitude ratio (VL/VMO) was significantly lower in the ovulatory phase compared to the follicular phase (P = .035 for rise tasks and .010 for rock tasks).

CONCLUSION

The menstrual cycle may affect some EMG parameters. These factors can be taken into account when planning sports and rehabilitation training programs.

Presynaptic inhibition decreases when estrogen level rises

The objective was to determine estrogen's influence on control of a skeletal muscle through measurements of motorneuron excitability (H:M ratio) and presynaptic inhibition (PI). Estrogen serum concentrations were measured at menses and ovulation of female subjects and compared to male controls. Data were analyzed from 12 women and 13 men reporting no history of knee ligament injury. Women reported regular menstrual cycles and no hormone-based contraceptive use for the previous year. Women were tested at menses (Time1) and ovulation (Time2). Men were tested twice, approximately 14 days apart. Analysis indicated no difference in the H:M ratio between the sexes at either time point. A significant difference for the sexes was detected in the magnitude of estrogen change (∆EST) between observations. At Time1, the male and female estrogen concentrations were not different; however, they were different at Time2, primarily due to the large rise observed in the women. A significant difference between the sexes was also seen in the magnitude of change for PI (∆PI) between observations. As with EST, the levels of PI between the sexes at Time1 were not different; however, a difference existed at Time 2. Estrogen interacts with GABA at several nervous system locations affecting inhibition of synaptic transmission. This is the first study to investigate changes in PI of a skeletal muscle between times of low and high estrogen. Improving the understanding of estrogen's influence on skeletal muscles may provide answers to why noncontact anterior cruciate ligament injuries of the knee occur more frequently in women.

The Effect of Menstrual Cycle and Contraceptives on ACL Injuries and Laxity: A Systematic Review and Meta-analysis

BACKGROUND

Women are at substantially greater risk for anterior cruciate ligament (ACL) injuries than are men.

PURPOSE

To conduct a systematic review and meta-analysis of the literature to clarify the effect of the menstrual cycle and contraceptives on the laxity of and noncontact injuries to the ACL.

STUDY DESIGN

Systematic review; Level of evidence, 4.

METHODS

Searches were conducted using MEDLINE (1946-August 2016), the Cochrane Library Database, clinical trial registries, and related reference lists. Search terms included athletic injuries, knee injuries, ligaments, joint instability, menstrual cycle, ovulation, hormones, and contraceptives. Investigators independently dually abstracted and reviewed study details and quality using predefined criteria and evaluated overall strength of evidence using the GRADE (Grading of Recommendations Assessment, Development and Evaluation) criteria.

RESULTS

Twenty-one studies totaling 68,758 participants were included: 5 on the menstrual cycle and ACL injury, 7 on hormonal contraceptives and ACL injury, as well as 13 on menstrual cycle and ligament laxity. Four of 5 studies of women not using hormonal contraception indicated that the luteal phase was the least associated with ACL injuries. The 2 largest and highest quality studies on hormonal contraceptives suggested that hormonal contraceptives may be protective against ACL injury. Six of 12 studies on ACL laxity provided quantitative data for meta-analysis, finding significantly increased laxity during the ovulatory phase compared with the follicular phase.

CONCLUSION

The literature suggests an association between hormonal fluctuations and ACL injury. Recent studies have suggested that oral contraceptives may offer up to a 20% reduction in risk of injury. The literature on ACL injuries and the menstrual cycle has more than doubled over the past decade, permitting quantitative analysis for the first time. However, the overall strength of this evidence is low. Promising potential directions for future research include long-term observational studies with ongoing hormonal assays and large interventional trials of follicular suppression, including newer hormonal methods.

Influence of Menstrual Cycle and Oral Contraceptive Phase on Spinal Excitability

BACKGROUND

Rates of musculoskeletal injury differ substantially between the genders, with females more likely to experience conditions such as anterior cruciate ligament (ACL) injuries than males in the same sports. Emerging evidence suggests a significant hormonal contribution. Most research has focused solely on how hormonal fluctuations affect connective tissue, but a direct link between hormonal shifts, ligamentous laxity, and ACL injury has not been borne out. There is also evidence to suggest that sex hormones can modulate the central nervous system, but how this affects neuromuscular control is not well understood.

OBJECTIVE

To determine whether changes in sex hormone concentrations would alter spinal excitability, measured across the menstrual and oral contraceptive pill cycle. We hypothesized that spinal excitability would fluctuate across the menstrual cycle (with increased excitability during the periovulatory phase due to peak estradiol concentration), but that there would be no fluctuation in oral contraceptive users.

DESIGN

This was a prospective cohort study.

SETTING

The study took place at a biomechanics laboratory at a rehabilitation hospital.

PARTICIPANTS

A total of 30 healthy women aged 18-35 who were similar in age, body composition, and exercise-training status were included. Fifteen of the women were eumenorrheic and nonusers of oral contraceptives (nonusers), and 15 of the women were taking oral contraceptives (users).

MAIN OUTCOME MEASURES

H-reflex (Hmax/Mmax ratio), serum estradiol, and progesterone concentrations were measured at 3 time points during the menstrual and contraceptive pill cycle.

RESULTS

The H-reflex (Hmax/Mmax ratio) remained stable across the menstrual and contraceptive pill cycle. Spinal excitability was lower in the users compared with the nonusers across all testing sessions, but this was not statistically significant.

CONCLUSIONS

Our results suggest that acute fluctuations of endogenous estradiol and progesterone do not modulate spinal excitability. However, long-term exposure to exogenous estrogen and progesterone (oral contraceptives) might have an impact on spinal excitability and neuromuscular control. Further research is necessary to better understand the potential differential effect of endogenous and exogenous sex hormones on spinal excitability.

Maximal force and tremor changes across the menstrual cycle

PURPOSE

Sex hormones have profound effects on the nervous system in vitro and in vivo. The present study examines the effect of the menstrual cycle on maximal isometric force (MVC) and tremor during an endurance task.

METHODS

Nine eumenorrheic females participated in five study visits across their menstrual cycle. In each menstrual phase, an MVC and an endurance task to failure were performed. Tremor across the endurance task was quantified as the coefficient of variation in force and was assessed in absolute time and relative percent time to task failure.

RESULTS

MVC decreases 23% from ovulation to the mid luteal phase of the menstrual cycle. In absolute time, the mid luteal phase has the highest initial tremor, though the early follicular phase has substantially higher tremor than other phases after 150 s of task performance. In relative time, the mid luteal phase has the highest level of tremor throughout the endurance task.

CONCLUSIONS

Both MVC and tremor during an endurance task are modified by the menstrual cycle. Performance of tasks and sports which require high force and steadiness to exhaustion may be decreased in the mid luteal phase compared to other menstrual phases.

Menstrual cycle mediates vastus medialis and vastus medialis oblique muscle activity

PURPOSE

Sports medicine professionals commonly describe two functionally different units of the vastus medialis (VM), the VM, and the vastus medialis oblique (VMO), but the anatomical support is equivocal. The functional difference of the VMO is principle to rehabilitation programs designed to alleviate anterior knee pain, a pathology that is known to have a greater occurrence in women. The purpose of this study was to determine whether the motor units of the VM and VMO are differentially recruited and if this recruitment pattern has an effect of sex or menstrual cycle phase.

METHODS

Single motor unit recordings from the VM and VMO were obtained for men and women during an isometric ramp knee extension. Eleven men were tested once. Seven women were tested during five different phases of the menstrual cycle, determined by basal body temperature mapping. The recruitment threshold and the initial firing rate at recruitment were determined from 510 motor unit recordings.

RESULTS

The initial firing rate was lower in the VMO than that in the VM in women (P < 0.001) but not in men. There was no difference in recruitment thresholds for the VM and VMO in either sex or across the menstrual cycle. There was a main effect of menstrual phase on initial firing rate, showing increases from the early follicular to late luteal phase (P = 0.003). The initial firing rate in the VMO was lower than that in the VM during ovulatory (P = 0.009) and midluteal (P = 0.009) phases.

CONCLUSION

The relative control of the VM and VMO changes across the menstrual cycle. This could influence patellar pathologies that have a higher incidence in women.

Effects of decision making on landing mechanics as a function of task and sex

BACKGROUND

Factors that contribute to sex-differences in the incidence of anterior cruciate ligament injuries among athletes are not well understood. Of interest is whether decision making during landing influences biomechanical factors associated with anterior cruciate ligament injury. This study examined the effects of decision making on the mechanics of two-footed landing tasks in women and men.

METHODS

Twenty-nine healthy young adults (13 women, 16 men) completed drop landings and drop-jumps under preplanned and decision-making conditions. Biomechanical data were collected and effects of decision making on lower extremity kinematics and kinetics were examined as a function of task and sex.

FINDINGS

Landing mechanics were influenced by decision-making condition, task, and sex. During drop-jumps, participants exhibited lesser hip flexion (-3.3°), lesser knee flexion (-5.1°), and greater knee abduction (+1.0°) at initial contact under decision-making conditions. Under decision-making conditions, no differences were observed in these variables between tasks or with respect to preplanned drop landings. Across tasks and sexes, participants exhibited greater ankle plantarflexion at initial contact (+1.6°), greater peak knee external rotation (+1.5°), lesser peak knee internal rotation (-1.0°), and smaller hip adduction moments (-0.2% body weight×height) under decision-making conditions. Women but not men exhibited smaller ankle inversion moments (-0.1% body weight×height) under decision-making conditions.

INTERPRETATION

Modifications in landing mechanics suggest a default towards the preplanned drop landing strategy under decision-making conditions. Across sexes, drop landings and drop-jumps may be no more dangerous under decision-making conditions, with respect to anterior cruciate ligament loading, than preplanned drop landings.

Prospective correlation between serum relaxin concentration and anterior cruciate ligament tears among elite collegiate female athletes

BACKGROUND

The female anterior cruciate ligament may be more susceptible to injury than the male anterior cruciate ligament because of the gender-specific expression of receptors for relaxin, a collagenolytic hormone that promotes remodeling of the anterior cruciate ligament.

PURPOSE

This study was undertaken to investigate whether collegiate female athletes with elevated serum relaxin concentrations (SRC) sustain anterior cruciate ligament tears at an increased rate compared with those with lower SRC.

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

From 2005 to 2010, 143 Division I female athletes from 2 universities participating in sports at high risk for anterior cruciate ligament tears (basketball, lacrosse, field hockey, soccer, gymnastics, and volleyball) were recruited to participate. Questionnaires and urine luteinizing hormone (LH) tests were used to determine participants' anterior cruciate ligament injury and menstrual history and to identify their mid-luteal phase or projected cycle days 21 to 24. Serum samples were obtained for progesterone and relaxin ELISA (enzyme-linked immunosorbent assay) analysis. Participants were monitored for anterior cruciate ligament injury over their 4-year National Collegiate Athletic Association athletic career.

RESULTS

A total of 128 participants completed the study and were eligible for data analysis. The cumulative incidence of complete anterior cruciate ligament tear over the 4-year study period was 21.9%, and varied significantly by sport (P < .001). The mean SRC for athletes with anterior cruciate ligament tears (6.0 ± 8.1 pg/mL) was significantly higher than that for those without anterior cruciate ligament tears (1.8 ± 3.4 pg/mL; P = .013). In subgroup analysis of the 46 athletes who had detectable SRC, the cumulative incidence of anterior cruciate ligament tear was 14 of 46 (30.4%); the mean SRC among athletes with anterior cruciate ligament tears (14 of 46) was 12.1 ± 7.7 pg/mL and without anterior cruciate ligament tears (32 of 46), 5.7 ± 3.6 pg/mL (P = .002). When 6.0 pg/mL was set as the SRC cutoff for screening athletes for risk of anterior cruciate ligament tear in the subgroup with detectable relaxin levels, the test had 71% sensitivity, 69% specificity, 52% positive predictive value, 88% negative predictive value, and a relative risk of 4.4. These values were significant by χ(2) test (P = .003) and receiver operating characteristic analysis (P = .002).

CONCLUSION

Elite female athletes with anterior cruciate ligament tears have higher SRC than those without tears. Those with an SRC greater than 6.0 pg/mL had over 4 times increased risk for a tear.

CLINICAL RELEVANCE

Females with higher serum relaxin levels may be at increased risk for anterior cruciate ligament tears. Further investigation of the clinical utility of SRC testing is warranted.

Frequency and clinical characteristics of chronic daily headache in an outpatient clinic setting

BACKGROUND AND PURPOSE

Chronic daily headache (CDH) is not a diagnosis but a category that includes many disorders representing primary and secondary headaches. According to the International Classification of Headache Disorders, 2nd edition (ICHD-II), CDH is defined as headache which occurs more often than 15 days per month for at least 3 months.

MATERIAL AND METHODS

We assessed 1154 headache sufferers diagnosed in our headache outpatient clinic. Clinical history, physical and neurological examination, and laboratory tests were performed to make a diagnosis.

RESULTS

CDH was diagnosed according to ICHD-II in 185 (16%) patients; their mean age was 41±17 years (80% were women). Chronic migraine was a cause of CDH in 49% (91/185) of patients, chronic tension-type headache in 18% (33/185), secondary headache in 25% (46/185) and unclassified pain in 8%. Medication overuse headache occurred in 15%. The most effective therapy in our patients was treatment with tricyclic antidepressants and selective serotonin reuptake inhibitors.

CONCLUSIONS

The most frequent cause of CDH in our cohort was chronic migraine. Women suffered more frequently than men. Antidepressants were the most effective preventive medications for all types of CDH, which may suggest that serotoninergic mechanisms can be an important factor in the pathophysiology of chronic pain syndromes.

Evidence of gender-specific motor templates to resist valgus loading at the knee

Gender differences in neuromuscular control of the lower extremity may contribute to increased injury risk in females, but the neurophysiological mechanisms underlying these differences remain unclear. In this study, we sought to explore the effect of gender on volitional and reflex neuromuscular responses to a rapid valgus perturbation at the knee applied under "intervene" and "do not intervene" conditions. Multiple 7 degrees ramp-and-hold valgus perturbations were applied at the neutrally extended knee of 12 male and 12 female healthy subjects, while surface electromyography over the quadriceps and hamstrings recorded the neuromuscular response. Volitional responses did not vary between groups, perhaps reflecting the relative novelty of the loading direction. However, reflex responses observed under the "do not intervene" paradigm did vary by gender. Males demonstrated much more frequent and consistent reflex muscle activation than females. Moreover, muscle activation patterns were gender-specific. Diminished responses in female subjects may indicate that the position-based valgus perturbation did not produce the necessary mechanical stimulus to elicit reflexes. These gender differences in reflex control of the knee provide new insight into the control of frontal-plane knee joint movement and loading and may elucidate the neuromechanical underpinnings associated with neuromuscular control.