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This study sought to evaluate the effects of oral contraceptive (OC) and hormonal intrauterine device (H-IUD) use, compared with a eumenorrheic (EUM) cycle, on fatigability and recovery between hormone the phases. Peak power (PP), average power (AP), fatigue index (FI), blood lactate, vessel diameter, and blood flow (BF) were measured from a repeated sprint cycle test (10 × 6 seconds) in 60, healthy, active women (mean ± SD; age: 26.5 ± 7.0 years, BMI: 22.5 ± 3.7 kg-m-2) who used monophasic OC (≥6 months; n = 21), had a H-IUD (≥6 months; n = 20), or had regular naturally occurring menstrual cycle (≥3 months) or had a nonhormonal IUD (EUM; n = 19). Subjects were randomly assigned to begin in either the low-hormone phase (LHP) or high-hormone phase (HHP) and were tested once in each phase. Separate univariate analyses of covariances assessed the change from HHP to LHP between the groups, covaried for progesterone, with significance set at p≤ 0.05. All groups demonstrated similar changes in PP, AP, FI, blood lactate, vessel diameter, and BF between the phases (p > 0.05). Although not significant, AP was higher in LHP for OC (A-248.2 ± 1,301.4 W) and EUM (A-19.5 ± 977.7 W) and higher in HHP for H-IUD (A 369.3 ± 1,123.0 W). Oral contraceptive group exhibited a higher FI (A 2.0%) and reduced blood lactate clearance (A 2.5%) in HHP. In recreationally active women, hormonal contraception and hormone phases may minimally impact fatigue and recovery. Individual elite female athletes may benefit from understanding hormonal contraception type as performance and recovery may slightly vary across the cycle. [ABSTRACT FROM AUTHOR]

This study investigated the effect of oral contraceptive (OC) use on acute changes in steroid hormone concentrations and tryptophan (TRP) metabolites in response to strength exercise. Twenty-one women (age: 23 ± 3 years), 8 combined OC users (OC group) and 13 naturally cycling women (menstrual cycle [MC] group), participated. Testing was performed during the pill-free interval for the OC group and the follicular phase for the MC group. Subjects completed an intense strength exercise protocol (4 x 10 repetitions back squat). Blood samples were taken at baseline (T0), post-exercise (T1), and after 24 hours (T2) to determine serum concentrations of cortisol, estradiol, testosterone, TRP, and kynurenine (KYN). Statistical significance was defined asp <0.05. At T0, the OC group showed higher cortisol (OC: 493.7 ± 47.1 ng⋅ml-1, MC: 299.1 ± 62.7 ng⋅ml-1, p < 0.001) and blood lactate(OC: 1.81 ±0.61 mmol⋅L-1, MC: 1.06 ± 0.30 mmol⋅L-1, p = 0.001) and lower estradiol (OC: 31.12 ± 4.24 pg⋅mL-1, MC: 38.34 ± 7.50 pg⋅mL-1, p = 0.023) and KYN (OC: 1.15 ± 0.23 μmol⋅L-1, MC: 1.75 ± 0.50 μmol⋅L-1, p = 0.005). No significant interactions (group x time, p> 0.05) were found for the hormones and TRP metabolites assessed. Oral contraceptive use did not affect the physiological response of steroid hormones and TRP metabolites to acute strength exercise during the low hormone phase of the contraceptive or MC in healthy young women, even when some baseline concentrations differed between groups. Consequently, these findings provide important implications for practitioners testing heterogeneous groups of female athletes. [ABSTRACT FROM AUTHOR]

Mooses, M, Haile, DW, Ojiambo, R, Sang, M, Mooses, K, Lane, AR, and Hackney, AC. Shorter ground contact time and better running economy: evidence from female Kenyan runners. J Strength Cond Res 35(2): 481-486, 2021-Previously, it has been concluded that the improvement in running economy (RE) might be considered as a key to the continued improvement in performance when no further increase in V̇o2max is observed. To date, RE has been extensively studied among male East African distance runners. By contrast, there is a paucity of data on the RE of female East African runners. A total of 10 female Kenyan runners performed 3 × 1,600-m steady-state run trials on a flat outdoor clay track (400-m lap) at the intensities that corresponded to their everyday training intensities for easy, moderate, and fast running. Running economy together with gait characteristics was determined. Subjects showed moderate to very good RE at the first (202 ± 26 ml·kg-1·km-1) and second (188 ± 12 ml·kg-1·km-1) run trials, respectively. Correlation analysis revealed significant relationship between ground contact time (GCT) and RE at the second run (r = 0.782; p = 0.022), which represented the intensity of anaerobic threshold. This study is the first to report the RE and gait characteristics of East African female athletes measured under everyday training settings. We provided the evidence that GCT is associated with the superior RE of the female Kenyan runners. [ABSTRACT FROM AUTHOR]

Myllyaho, MM, Ihalainen, JK, Hackney, AC, Valtonen, M, Nummela, A, Vaara, E, Häkkinen, K, Kyröläinen, H, and Taipale, RS. Hormonal contraceptive use does not affect strength, endurance, or body composition adaptations to combined strength and endurance training in women. J Strength Cond Res 35(2): 449-457, 2021-This study examined the effects of a 10-week period of high-intensity combined strength and endurance training on strength, endurance, body composition, and serum hormone concentrations in physically active women using hormonal contraceptives (HCs, n = 9) compared with those who had never used hormonal contraceptives (NHCs, n = 9). Training consisted of 2 strength training sessions and 2 high-intensity running interval sessions per week. Maximal bilateral isometric leg press (Isom), maximal bilateral dynamic leg press (one repetition maximum [1RM]), countermovement jump (CMJ), a 3,000-m running test (3,000 m), body composition, and serum hormone levels were measured before and after training between days 1-5 of each subject's menstrual cycle. Both groups increased 1RM and CMJ: HC = 13.2% (p < 0.001) and 9.6% (p < 0.05), and NHC = 8.3% (p < 0.01) and 8.5% (p < 0.001). Hormonal contraceptive improved 3,000 m by 3.5% (p < 0.05) and NHC by 1% (n.s.). Never used hormonal contraceptive increased lean mass by 2.1% (p < 0.001), whereas body fat percentage decreased from 23.9 ± 6.7 to 22.4 ± 6.0 (-6.0%, p < 0.05). No significant changes were observed in body composition in HC. No significant between-group differences were observed in any of the performance variables. Luteinizing hormone concentrations decreased significantly (p < 0.05) over 10 weeks in NHC, whereas other hormone levels remained statistically unaltered in both groups. It seems that the present training is equally appropriate for improving strength, endurance, and body composition in women using HC as those not using HC without disrupting hypothalamic-pituitary-gonadal axis function. [ABSTRACT FROM AUTHOR]

Background: Special Operations Forces (SOF) combat soldiers are frequently exposed to blast and blunt neurotrauma, most often classified as mild traumatic brain injury (mTBI). Repetitive mTBI may increase the risk of developing long-term neurological sequelae. Identifying changes in neuroinflammatory biomarkers before chronic conditions emerge could serve as preliminary evidence of developing neuropathology. Objective: To determine the effects of mTBI history, lifetime mTBI incidence, and recency on blood biomarker concentrations of axonal protein neurofilament light (NfL), glycolytic enzyme neuron-specific enolase (NSE), astrocyte-expressed S100 calcium-binding protein B (S100B), and neurotrophic cytokine interleukin-6 (IL-6) in healthy, active duty SOF combat soldiers. Methods: Self-reported mTBI history/recency and fasted blood samples were collected in this cross-sectional study of 104 asymptomatic SOF combat soldiers. Biomarker concentrations were quantified using commercial enzyme-linked immunosorbent assays. Mann-Whitney U and Kruskal-Wallis tests were used to compare groups. Post hoc tests with appropriate corrections were conducted as warranted. Results: Soldiers with mTBI history had higher NSE concentrations than those without (z = -2.60, P = .01). We also observed significant main effects o f lifetime mTBI incidence on NSE (χ²(3) = 9.52, P = .02) and S100B (χ²(3) = 8.21, P = .04) concentrations and a significant main effect of mTBI recency on NfL concentration (χ²(2) = 6.02, P = .049). Conclusion: The SOF combat soldiers with mTBI history had increased NSE. Longitudinal studies in this population are needed due to between-subject heterogeneity in biomarker concentrations. The NfL concentrations in our SOF combat soldiers--regardless of mTBI history or recency-were similar to values previously reported in civilian acute TBI patients. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the effects of 2 soccer-training seasons on physical fitness and hormone concentrations in elite youth soccer players. Twenty male elite soccer players (SP, age 14.5 ± 0.4 years) and 20 male control subjects (CS, age 14.3 ± 0.3 years) participated in the study. Anthropometric measurements, aerobic (Yo-Yo Intermittent Recovery Test Level 1 [YYIRT1]) and anaerobic soccer relevant performances (jump and sprint tests), blood testosterone (T), cortisol (C), sex hormone binding globulin (SHBG), and T/C ratio were assessed 5 times (from T0 to T4) during 2 competitive seasons. Significant differences from basal values (Δ) of T, SHBG, and C between SP and CS were observed (p < 0.01). Additionally, T and T/C ratio changes were positively correlated with physical performance (p ≤ 0.05). In conclusion, as expected, higher T concentration and greater power performance were observed in the soccer players group compared with controls. Our findings also show that the T concentrations and power performance outcomes co-vary positively over the 2 soccer seasons in soccer players. [ABSTRACT FROM AUTHOR]

Purpose: This article aimed to study the associations between aspects of endurance exercise training and sexual libido in healthy men using a cross-sectional online survey study design. Methods: A developed online survey questionnaire was used. The questionnaire was based on preexisting validated questionnaires and was used to assess elements of physical characteristics, exercise training habits, and libido of participants (n = 1077). Three evidence-based categories were created for the primary outcome of total libido score and low, normal, and high-response category sets. The high and normal categories were combined to form a high/normal score group, and the low category formed a low score group. Odds ratio (OR) values were calculated to examine group categorization. Results: Age, training intensity, and training duration of participants had significant (P < 0.02) univariate relationships, with libido scores, and were thus included in the multivariate model. In the multivariate model, training intensity (P < 0.0001) and duration (P < 0.002) components were the most significantly associated with libido group designation (high/normal vs low). Participants with the lowest (OR = 6.9, 95% confidence interval [CI] = 2.6-17.9) and mid-range training intensities (OR = 2.8, 95% CI = 1.4-5.3) had greater odds of high/normal libido state than those with the highest training intensity. Participants with the shorter (OR = 4.1, 95% CI = 1.6-10.0) and mid-range training durations (OR = 2.5, 95% CI = 1.3-4.8) at their current intensity also had greater odds of high/normal libido score than those with a greatest duration. Conclusion: Exposure to higher levels of chronic intense and greater durations of endurance training on a regular basis is significantly associated with a decreased libido scores in men. Clinicians who treat male patients for sexual disorders and/or council couples on infertility issues should consider the degree ofendurance exercise training a man is performing as a potential complicating factor. [ABSTRACT FROM AUTHOR]

Introduction: To evaluate the effects of oral contraceptive (OC) and hormonal intrauterine device (H-IUD) use, compared to an eumenorrheic (EUM) cycle, on maximal strength and power between hormone phases., Methods: One repetition max (1RM) leg press and bench press, peak force (PF) from knee extension and upright row isometric dynamometry, and power from vertical jump height (VJH) and reactive strength index (RSI; cm/s) were measured in 60 healthy, active women (mean ± standard deviation [SD]; Age: 26.5 ± 7.0 yrs, BMI: 22.5 ± 3.7 kg/m2) who were monophasic OC users for ≥6 months (n = 21), had a H-IUD for ≥6 months (n = 20), or had regularly naturally occurring menstrual cycle for ≥3 months or were using a non-hormonal IUD (EUM; n = 19). Participants were randomly assigned to begin in the follicular phase/placebo pill (low hormone phase; LHP) or in the luteal phase/active pill (high hormone phase; HHP) and were tested once in each phase. Estimates of total lean mass (LM), leg LM, and arm LM were measured via dual energy x-ray absorptiometry. Separate univariate ANCOVAs were used to assess the change from HHP to LHP between groups, with LM and progesterone as covariates., Results: Leg press 1RM was significantly different across phases between groups (p = 0.027), with higher leg press 1RM in the HHP for the OC group (mean difference[∆HHP-LHP] ± standard error: ∆7.4 ± 15.9 kg; p = 0.043) compared to the H-IUD group (∆-8.9 ± 23.8 kg; p = 0.043). All groups demonstrated similar bench press 1RM, PF, VJH, and RSI between phases (p > 0.05)., Conclusions: Lower body strength was greater in the HHP for OC users (5.6% increase) suggesting lower body maximal strength outcomes may be influenced by hormonal contraception type., Competing Interests: Conflict of Interest and Funding Source: The authors declare no conflict of interest. This study received funding from the National Strength and Conditioning Association Foundation. The research reported in this publication was supported by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under Award Number T32DK064584., (Copyright © 2024 by the American College of Sports Medicine.)

Introduction: Resting energy expenditure (REE) may fluctuate during the menstrual cycle (MC), due to the physiological effects of estradiol (E2) and progesterone (P4). This study examined changes in REE and metabolic hormones (leptin, ghrelin, thyroid hormones), and dietary intake in two hormonally distinct groups, naturally menstruating women (NoOC) and women using monophasic combined oral contraceptives (COC)., Methods: Measurements included REE by indirect calorimetry, body composition by bioimpedance, and blood samples for hormone analysis in the early follicular and mid-luteal phases of the MC in NoOC-group (n = 38) or the active and inactive phases of the COC cycle (COC, n = 19). Participants recorded their food intake for 3 days after measurements. A secondary analysis was completed for the NoOC-group without REE outliers (difference between measurements >1.5 × interquartile range, n = 4)., Results: In the NoOC-group, luteal phase REE was 40 kcal higher than follicular phase REE [95% confidence interval (CI): -2 kcal/d-82 kcal/d, d = 0.20, p = 0.061]. Leptin (d = 0.35, p < 0.001), T3 (d = 0.26, p = 0.05) and fat intake (d = 0.48, p = 0.027) were lower, and T4 (d = 0.21, p = 0.041) was higher in the luteal phase. After excluding outliers, REE was 44 kcal higher in the luteal phase than in the follicular phase (95% CI: 12 kcal/d-76 kcal/d, d = 0.22, p = 0.007). In the COC-group, the mean difference in REE was -2 kcal (95% CI-82 kcal/d-79 kcal/d) between active and inactive phases, while T3 was higher in the inactive phase (d = 0.01, p = 0.037)., Conclusions: REE increases only slightly from the follicular to the luteal phase but remains unchanged between COC phases. Increases in T3, leptin, and fat intake during the luteal phase might echo metabolic fluctuations that parallel female sex hormones during the MC., Competing Interests: Conflict of Interest and Funding Source: The data presented here are part of a larger Women’s menstrual cycle and endurance training (NaisQs) study. The study was funded by the Finnish Ministry of Education and Culture and Firstbeat Analytics Expense funding for blood analyses was received from the Suomen Urheilututkimussäätiö. The authors declare no conflicts of interest, financial or otherwise, regarding this study., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American College of Sports Medicine.)

Purpose: This study aimed to examine the effects of fatiguing power loading on neuromuscular properties, force production, and metabolic capacities during four phases of the menstrual cycle (MC): menstruation (M), midfollicular (mid FOL), ovulation (OV), and midluteal (mid LUT)., Methods: Sixteen eumenorrheic women performed sessions of maximal explosive leg press (2 × 10 at 60% one-repetition maximum load with 2-min recovery between sets). Serum hormones and neuromuscular responses were measured., Results: The loading protocol significantly decreased power (between -14.2% and -12.5%; P < 0.001) and maximal force production (between maximum voluntary force (MVC); -15.0% and -7.8%; P < 0.001-0.05), while decreasing activation level (between AL; -6.9% and -2.2%; P < 0.001-0.05) in all MC phases. The decreases in AL were greater during mid LUT (P < 0.01) compared with OV. Changes in MVC and AL were associated (r2 = 0.53; P < 0.01) at all MC phases. The decrease in EMG during MVC did not differ between the MC phases; however, mean power frequency was higher during M (+7.7%; P < 0.05) and mid LUT (+3.1%; P < 0.05) compared with OV (-7.5%). Resting twitch force decreased during mid FOL (-6.9%; P < 0.05) and mid LUT (-16.2%; P < 0.001), and these values were significantly decreased (P < 0.05) compared with OV. In addition, resting twitch force at mid LUT was lower (P < 0.01) compared with M. Blood lactate levels increased more (P < 0.05) during M compared with mid LUT. Some serum hormone concentrations were associated with fatigue-induced changes in neuromuscular properties and force production, but these correlations behaved differently between the MC phases., Conclusions: OV may offer a more favorable hormonal milieu for acute neural responses, whereas mid FOL and mid LUT seem to be superior for acute muscular responses., (Copyright © 2022 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American College of Sports Medicine.)