Part II. Common questions and misconceptions about creatine supplementation: what does the scientific evidence really show?

Creatine monohydrate supplementation (CrM) is a safe and effective intervention for improving certain aspects of sport, exercise performance, and health across the lifespan. Despite its evidence-based pedigree, several questions and misconceptions about CrM remain. To initially address some of these concerns, our group published a narrative review in 2021 discussing the scientific evidence as to whether CrM leads to water retention and fat accumulation, is a steroid, causes hair loss, dehydration or muscle cramping, adversely affects renal and liver function, and if CrM is safe and/or effective for children, adolescents, biological females, and older adults.

Utility of fat-free adipose tissue correction formula for tracking body composition changes with dual-energy X-ray absorptiometry.

Introduction: Fat loss is often the target of weight loss interventions; however, preservation of lean soft tissue (LST) may be more important for health and weight maintenance. Though some LST loss may be inevitable when tracking body composition changes using dual-energy X-ray absorptiometry (DXA), correcting for the fat-free component of adipose tissue (FFAT) in DXA-derived LST (DXALST) has been proposed. This analysis sought to evaluate differences between DXALST and FFAT-corrected LST (FFATLST) amongst varied populations and interventions to understand application of the correction formula on LST outcomes.

Single Leg Hop Performance After Anterior Cruciate Ligament Reconstruction: Ready for Landing but Cleared for Take-Off?

Context: Understanding former professional football players engagement with health promoting behaviors (physical exercise, high quality diet, and good sleep hygiene) will be helpful for developing lifestyle interventions to improve their feelings of well-being, a relatively understudied facet of health among this population.

Objective: Examine associations among health-promoting behaviors and subjective outcomes related to well-being among former National Football League (NFL) players.

Design: Cross-sectional.

Effects of Hormonal Contraception and the Menstrual Cycle on Maximal Strength and Power Performance.

Introduction: To evaluate the effects of oral contraceptive (OC) and hormonal intrauterine device (H-IUD) use, compared with an eumenorrheic (EUM) cycle, on maximal strength and power between hormone phases.

Methods: One-repetition maximum (1RM) leg press and bench press, peak force from knee extension and upright row isometric dynamometry, and power from vertical jump height and reactive strength index (cm·s -1 ) were measured in 60 healthy, active women (mean ± SD; age: 26.5 ± 7.

Fat-Free Mass Index in Sport: Normative Profiles and Applications for Collegiate Athletes.

Jagim, AR, Harty, PS, Jones, MT, Fields, JB, Magee, M, Smith-Ryan, AE, Luedke, J, and Kerksick, CM. Fat-free mass index in sport: normative profiles and applications for collegiate athletes. J Strength Cond Res 38(9): 1687-1693, 2024-Recent concerns have been raised regarding the ethical considerations of conducting body composition assessments in sports.

Effects of the Menstrual Cycle and Hormonal Contraceptive Use on Metabolic Outcomes, Strength Performance, and Recovery: A Narrative Review.

The effects of female sex hormones on optimal performance have been increasingly recognized as an important consideration in exercise and sport science research. This narrative review explores the findings of studies evaluating the effects of menstrual cycle phase in eumenorrheic women and the use of hormonal contraception (oral contraceptives and hormonal intrauterine devices) on metabolism, muscular strength, and recovery in active females. Ovarian hormones are known to influence metabolism because estrogen is a master regulator of bioenergetics.

Association between dietary intake of creatine and female reproductive health: Evidence from NHANES 2017-2020.

The hormonal changes in women influence creatine dynamics, emphasizing its potential importance during menstruation, pregnancy, postpartum, menopause, and postmenopause. Yet, limited research explores creatine's impact on female reproductive health at the population level. Our study investigated the relationship between dietary creatine intake and reproductive health indices in US women using data from the 2017-2020 National Health and Nutrition Examination Survey (NHANES).

Effects of Hormonal Contraception and the Menstrual Cycle on Fatigability and Recovery From an Anaerobic Exercise Test.

Cabre, HE, Ladan, AN, Moore, SR, Joniak, KE, Blue, MNM, Pietrosimone, BG, Hackney, AC, and Smith-Ryan, AE. Effects of hormonal contraception and the menstrual cycle on fatigability and recovery from an anaerobic exercise test. J Strength Cond Res 38(7): 1256-1265, 2024-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.

Body composition, physical activity, and menopause symptoms: how do they relate?

Objective: This study characterized the impact of physical activity (light, moderate, and vigorous [VIG] active minutes per day) and body composition (percent body fat [%BF] and fat-free mass index) on total menopausal symptoms (TMSs) in 72 premenopausal, perimenopausal (PERI), or postmenopausal women.

Methods: Activity minutes were collected from wearable fitness trackers. Body composition was evaluated using a whole-body dual-energy x-ray absorptiometry scan.

Ultrasound-based measurement of central adiposity: Key considerations and guidelines.

Central adiposity, which is visceral and subcutaneous adiposity in the abdominal region, is a known risk factor for developing chronic cardiometabolic diseases. Central adiposity can be measured relatively inexpensively using ultrasound. Ultrasound has been shown to be precise and reliable, with measurement accuracy comparable to computed tomography and magnetic resonance.

Pre-exercise protein intake is associated with reduced time in hypoglycaemia among adolescents with type 1 diabetes.

Aim: Secondary analyses were conducted from a randomized trial of an adaptive behavioural intervention to assess the relationship between protein intake (g and g/kg) consumed within 4 h before moderate-to-vigorous physical activity (MVPA) bouts and glycaemia during and following MVPA bouts among adolescents with type 1 diabetes (T1D).

Materials And Methods: Adolescents (n = 112) with T1D, 14.5 (13.

Post-Exercise Protein Intake May Reduce Time in Hypoglycemia Following Moderate-Intensity Continuous Exercise among Adults with Type 1 Diabetes.

Little is known about the role of post-exercise protein intake on post-exercise glycemia. Secondary analyses were conducted to evaluate the role of post-exercise protein intake on post-exercise glycemia using data from an exercise pilot study. Adults with T1D ( = 11), with an average age of 33.

Pre-sleep feeding, sleep quality, and markers of recovery in division I NCAA female soccer players.

Pre-sleep nutrition habits in elite female athletes have yet to be evaluated. A retrospective analysis was performed with 14 NCAA Division I female soccer players who wore a WHOOP, Inc. band - a wearable device that quantifies recovery by measuring sleep, activity, and heart rate metrics through actigraphy and photoplethysmography, respectively - 24 h a day for an entire competitive season to measure sleep and recovery.

International society of sports nutrition position stand: nutritional concerns of the female athlete.

Based on a comprehensive review and critical analysis of the literature regarding the nutritional concerns of female athletes, conducted by experts in the field and selected members of the International Society of Sports Nutrition (ISSN), the following conclusions represent the official Position of the Society: 1. Female athletes have unique and unpredictable hormone profiles, which influence their physiology and nutritional needs across their lifespan. To understand how perturbations in these hormones affect the individual, we recommend that female athletes of reproductive age should track their hormonal status (natural, hormone driven) against training and recovery to determine their individual patterns and needs and peri and post-menopausal athletes should track against training and recovery metrics to determine the individuals' unique patterns.

The effects of L-Citrulline and Glutathione on Endurance performance in young adult trained males.

Background: Citrulline may amplify the effects of L-arginine and nitric oxide concentration, which may augment vasodilation and blood flow, thereby enhancing aerobic exercise performance. The purpose of this randomized, double-blind, placebo-controlled crossover study was to investigate effects of L-citrulline + Glutathione on aerobic exercise performance and blood flow in well-trained men.

Methods: Twenty-five males (Mean ± SD; Age: 22.

A High Protein Diet Is Associated with Improved Glycemic Control Following Exercise among Adolescents with Type 1 Diabetes.

Nutritional strategies are needed to aid people with type 1 diabetes (T1D) in managing glycemia following exercise. Secondary analyses were conducted from a randomized trial of an adaptive behavioral intervention to assess the relationship between post-exercise and daily protein (g/kg) intake on glycemia following moderate-to-vigorous physical activity (MVPA) among adolescents with T1D. Adolescents ( = 112) with T1D, 14.

Validity of total body water measured by multi-frequency bioelectrical impedance devices in a multi-ethnic sample.

Background & Aims: Total body water (TBW) is the largest component of fat free mass and therefore is commonly used in multi-compartment body composition models and as a stand-alone method to assess body composition. Previous literature has not validated bioelectrical impedance spectroscopy device estimates of TBW in racial and ethnic minority populations; previous studies have focused on bioelectrical impedance analysis devices that rely on proprietary algorithms and participant characteristics for accuracy. The purpose of this study was to assess the validity of two bioelectrical impedance spectroscopy devices for measures of TBW compared to a deuterium dilution criterion in a multi-ethnic sample.

Menopause Transition: A Cross-Sectional Evaluation on Muscle Size and Quality.

Introduction: The menopause transition yields significant physiological alterations. The purpose was to characterize lean soft tissue (LST), muscle size (muscle cross-sectional area (mCSA)), muscle quality (echo intensity (EI)), and strength across the menopause transition. A secondary aim was to evaluate whole-body protein turnover in a subsample of women.

International society of sports nutrition position stand: energy drinks and energy shots.

Position Statement: The (ISSN) bases the following position stand on a critical analysis of the literature regarding the effects of energy drink (ED) or energy shot (ES) consumption on acute exercise performance, metabolism, and cognition, along with synergistic exercise-related performance outcomes and training adaptations. The following 13 points constitute the consensus of the Society and have been approved by the Research Committee of the Society: Energy drinks (ED) commonly contain caffeine, taurine, ginseng, guarana, carnitine, choline, B vitamins (vitamins B1, B2, B3, B5, B6, B9, and B12), vitamin C, vitamin A (beta carotene), vitamin D, electrolytes (sodium, potassium, magnesium, and calcium), sugars (nutritive and non-nutritive sweeteners), tyrosine, and L-theanine, with prevalence for each ingredient ranging from 1.3 to 100%.

The Time Course of Health, Fitness, and Occupational Performance Changes in Recruits across a Fire Academy.

Purpose: The purpose of this study was to examine the time course of health, fitness, and occupational performance changes in firefighter recruits across a fire academy.

Methods: Nineteen recruits (24.9 ± 4.

A Randomized Controlled Trial of Changes in Fluid Distribution across Menstrual Phases with Creatine Supplementation.

This study examined the effects of creatine (Cr) loading on body mass (BM) and fluid markers of total body water (TBW), extra-cellular fluid (ECF), and intra-cellular fluid (ICF) across the menstrual cycle (MC). Thirty moderately active females, either naturally-menstruating (NM) or using hormonal contraceptives (HC), were randomized to Cr (Cr; 4 × 5 g/day of creatine monohydrate for 5 days; n = 15) or a non-caloric placebo (PL; n = 15) using a double-blind, placebo-controlled design, with a menstrual phase crossover. BM, TBW, ECF, and ICF were measured at pre- and post-supplementation in randomized order of follicular phase (FP; NM: MC days 0−8, HC: inactive pill days) or luteal phase (LP; NM: ≤15 days from next projected cycle start date, HC: active pill days) using bioelectrical impedance spectroscopy.

Evaluation of pre-workout and recovery formulations on body composition and performance after a 6-week high-intensity training program.

Introduction: Activities such as high-intensity resistance training (HIRT) and high-intensity interval training (HIIT) may be more time-efficient modes to stimulate rapid changes in performance and body composition. There is little research evaluating the combined effects of HIRT and HIIT on body composition and strength, particularly when paired with nutritional supplementation.

Purpose: To evaluate the chronic effects of pre- and post-workout supplementation on body composition and strength, and to understand sex-specific responses.

Physical activity and pregnancy outcomes: an expert review.

This expert review aimed to assess current literature on the effect and tracking of physical activity during pregnancy and associated outcomes. Self-reported physical activity may be inaccurate given the subjective nature of the questionnaires. The accelerometer ActiGraph is considered the "gold standard" to objectively measure physical activity.

Active Women Across the Lifespan: Nutritional Ingredients to Support Health and Wellness.

Women are the largest consumers of dietary supplements. Dietary supplements can play a role in health and performance, particularly for women. Growing evidence and innovations support the unique physiological and nutrient timing needs for women.