Jeffrey R. Stout

University of Central Florida | UCF · School of Kinesiology and Physical Therapy

Position Statement: The International Society of Sports Nutrition (ISSN) presents this position based on a critical examination of literature surrounding the effects of essential amino acid (EAA) supplementation on skeletal muscle maintenance and performance. This position stand is intended to provide a scientific foundation to athletes, dietitians...

BACKGROUND Interdisciplinary evaluation of older adults’ healthcare is a priority in prevention of chronic health conditions and maintenance of daily functioning. While many studies evaluate different physical performance tests (PPTs) from a retrospective view in predicting mortality or cardiopulmonary health, it remains unclear which of the common...

Renziehausen, JM, Bergquist, AM, Park, J-H, Hill, EC, Wells, AJ, Stout, JR, and Fukuda, DH. Time of day effects on anaerobic performance using a nonmotorized treadmill. J Strength Cond Res 37(10): 2002–2007, 2023—The purpose of this study was to determine the effects of time of day on performance during a maximal effort sprinting assessment (30nmt)...

This study aimed to determine the test-retest reliability and efficacy of the Drift protocol. Thirteen male Division I Baseball pitchers (18–35 years.) completed four testing visits where a single leg hopping protocol on the stride and trail legs was completed with and without an arm swing. Jump contact time and flight time demonstrated “moderate t...

Background The lack of health care coverage, low education, low motivation, and inconvenience remain barriers to participating in fall prevention programs, especially among low-income older adults. Low-income status also contributes to negative aging self-perceptions and is associated with a high perceived barrier to care. Existing fall prevention...

BACKGROUND The lack of health care coverage, low education, low motivation, and inconvenience remain barriers to participating in fall prevention programs, especially among low-income older adults. Low-income status also contributes to negative aging self-perceptions and is associated with a high perceived barrier to care. Existing fall prevention...

Background: Adequate normalization methodology to establish maximum voluntary isometric contraction (MVIC) is needed to compare %MVIC values for core exercise completed until discontinuation. Clinicians can use %MVIC classifications to guide their preventative and rehabilitative exercise interventions. Objective: The aim of this study was to com...

Accelerometer data is commonplace in physical activity research, exercise science, and public health studies, where the goal is to understand and compare physical activity differences between groups and/or subject populations, and to identify patterns and trends in physical activity behavior to inform interventions for improving public health. We p...

The purpose of this study was to estimate the workloads accumulated by collegiate female soccer players during a competitive season and to compare the workloads of starters and substitutes. Data from 19 college soccer players (height: 1.58 ± 0.06 m; body mass: 61.57 ± 6.88 kg) were extracted from global positioning system (GPS)/heart rate (HR) moni...

We examined the associations between levels of accelerometer-based physical activity and the mismatch of physiological fall risk and fear of falling (FOF) in community-dwelling older adults. We assessed 123 participants who received 7-day wrist-worn accelerometry. Physiological fall risk was assessed using the portable BTrackS™ balance system and F...

Objectives: We aimed to 1) assess body composition using a portable technology, bioelectrical impedance analysis, (BIA) and 2) examine the associations between body composition and the discrepancy of fear of falling (FOF) and balance performance. Methods: A cross-sectional study included 121 older adults 60 years and older, 78% were female, 41% liv...

(1) Background: There is a lack of literature that examines the impact of early vs. late sport specialization on quality of life after retirement from tennis. Thus, the purpose of this study was to examine the relationship between early specialization in the sport of tennis and health outcomes after retirement from collegiate/professional sport; (2...

Non-exercise physical activity (NEPA), also called unstructured or informal physical activity, refers to those daily activities that require movement of the human body without planning or strict control of the physical effort made. Due to new technologies and motorized transportation devices, the general population has significantly decreased its N...

Background: Endurance performance has been shown to be enhanced by strength training. Therefore, there is a potential relationship between power-related variables such as the countermovement jump (CMJ) and drop jump (DJ) with specific cardiorespiratory performance parameters such as maximal oxygen consumption (VO2max) and velocity at VO2max (vVO2ma...

Position Statement: The International Society of Sports Nutrition (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 tra...

Background Carbohydrate (CHO) and carbohydrate-protein co-ingestion (CHO-P) have been shown to be equally effective for enhancing glycogen resynthesis and subsequent same-day performance when CHO intake is suboptimal (≤0.8 g/kg). Few studies have specifically examined the effect of isocaloric CHO vs CHO-P consumption on subsequent high-intensity ae...

The individual effects of physical activity (PA) and sedentary behavior (SB) on health are well-recognized. However, little is known about the extent to which different combinations of these behaviors are associated with body composition and fall risk in older adults. This cross-sectional study examined the associations of mutually exclusive catego...

Research is limited on the use of technology to help individuals who have a mismatch between physiological fall risk (Body) and perceived fall risk (Mind) and are unable to access traditional fall interventions. We examined the feasibility and acceptability of a technology-based body-mind intervention in low-income older adults during the COVID-19...

Falls and fear of falling (FOF) are the leading cause of disability, and hospitalization in ethnically diverse low-income older adults. The present study included an ethnically diverse sample of low-income older adults (N=121) to examine ethnic and income-based group differences in risk factors for falls (high FOF, depression, avoidance of physical...

Background The demands of typical daily activities require a constant level of alertness and attention. Multi-ingredient, caffeine-containing supplements have been shown to improve measures of cognitive performance. As many of these supplements become readily available, efficacy of each should be evaluated. Therefore, the purpose of this study is t...

Weight resistance training (RT) is an essential component of physical conditioning programs to improve the quality of life and physical fitness in different ages and populations. This integrative review aimed to analyze the scientific evidence on the relationship between exercise selection and the appearance of musculoskeletal injuries in physical...

Muscle disorders and induced muscle atrophy impose critical risks to the well-being of an individual, limiting normal activities of daily living. Several resistance training methods exist that have effectively reversed the progression of muscle atrophy. Weightlifting and hydrotherapy are the two widely practiced schemes for resistance training; how...

This position stand aims to provide an evidence-based summary of the energy and nutritional demands of tactical athletes to promote optimal health and performance while keeping in mind the unique challenges faced due to work schedules, job demands, and austere environments. After a critical analysis of the literature, the following nutritional guid...

Purpose Previous studies have suggested that beta-alanine supplementation may benefit exercise performance, but current evidence regarding its effects on body composition remains unclear. This systematic review and meta-analysis aimed to investigate the effects of beta-alanine supplementation on body composition indices. Methods Online databases, i...

The long-term impact of weight cycling on health status, eating habits, physical activity, and the lifestyle of former combat sports athletes is still insufficiently explored. Therefore, a novel questionnaire in English, Portuguese, Spanish and Croatian language was constructed. To determine the reliability and the content/face validity, a total of...

Introduction: The addition of protein to a carbohydrate solution has been shown to effectively stimulate glycogen synthesis in an acute setting and enhance exercise performance in a subsequent bout of exhaustive exercise. This study examined the effects of carbohydrate-protein (CHO-P), carbohydrate (CHO), and placebo (PLA) within a 2-hour recovery...

BACKGROUND Physical activity (PA) is vital for attenuating the aging-related physiological and functional declines in women aged 60 years or above. However, little is known about the objectively assessed PA behavior in older women during the COVID-19 pandemic and its association with socio-demographics, health and physical function. OBJECTIVE This...

Background Physical activity (PA) is vital for attenuating the aging-related physiological and functional declines in women aged 60 years or above. However, little is known about the objectively assessed PA behavior in older women during the COVID-19 pandemic and its association with sociodemographics, health and physical function, and COVID-19 rel...

The immune function is closely related to iron (Fe) homeostasis and allostasis. The aim of this bioinformatics-assisted review was twofold; (i) to update the current knowledge of Fe metabolism and its relationship to the immune system, and (ii) to perform a prediction analysis of regulatory network hubs that might serve as potential biomarkers duri...

The purpose of this study was to evaluate the effects of environmental conditions on running performance and performance efficiency index (Effindex). Performance data recorded using Polar Team Pro sensors from eight collegiate female soccer players in nine matches were analyzed during the 2019 competitive season. Effindex and running performance, i...

Promising technologies, which are simple, portable, quick, non-invasive, and inexpensive, may open new horizons on fall risk assessments and provide important information for older adults. We used a mixed-methods approach to examine the feasibility and acceptability of technology-based fall risk assessments, including the BTrackS Balance System, Bi...

One-third of older adults have a discrepancy between perceived and physiological fall risks or maladaptive fall risk appraisal (FRA). Older adults who report high fear of falling and overestimate their physiological fall risk are less likely to participate in physical activity (PA). Limited data suggest the interrelation between fall risk appraisal...

One-third of older adults have maladaptive fall risk appraisal (FRA), a condition in which there is a discrepancy between perceived fall risk or levels of fear of falling (FOF) and physiological fall risk (balance performance). We aimed to examine the associations among FRA, body composition, and physical activity (PA) using Assistive Health Techno...

COVID-19 pandemic has caused a severely detrimental effect on the physical, psychological, and functional well-being of older adults by forcing them to limit their social activities. This study investigates the amount and intensity of daily physical activity (PA) in older adults, living under the social distancing guidelines during COVID-19 pandemi...

Fear of falling is common in the older adult population with an estimated 43% being affected. We aimed to examine the associations among fear of falling, fall risk, depression, and anxiety in community-dwelling older adults. For this study 124 participants ranging from 60 to 96 years of age were recruited from the community settings in Central Flor...

The mechanical properties of knee flexors and extensors in 15 collegiate male soccer players following different warm-up protocols [small-sided games (SSG), dynamic (DYN), and plyometric (PLY)] were evaluated. Tensiomyography (TMG) was used to assess contraction time (Tc), delay time (Td) and maximal displacement (Dm) of the rectus femoris (RF) and...

Based on a comprehensive review and critical analysis of the literature regarding the effects of sodium bicarbonate supplementation on exercise performance, 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. Sup...

Creatine (Cr) and phosphocreatine (PCr) are physiologically essential molecules for life, given they serve as rapid and localized support of energy- and mechanical-dependent processes. This evolutionary advantage is based on the action of creatine kinase (CK) isozymes that connect places of ATP synthesis with sites of ATP consumption (the CK/PCr sy...

Herda, AA, Smith-Ryan, AE, Kendall, KL, Cramer, JT, and Stout, JR. Evaluation of high-intensity interval training and beta-alanine supplementation on efficiency of electrical activity and electromyographic fatigue threshold. J Strength Cond Res 35(6): 1535-1541, 2021-The purpose of this study was to determine the effects of high-intensity interval...

Numerous health conditions affecting the musculoskeletal, cardiopulmonary, and nervous systems can result in physical dysfunction, impaired performance, muscle weakness, and disuse-induced atrophy. Due to its well-documented anabolic potential, creatine monohydrate has been investigated as a supplemental agent to mitigate the loss of muscle mass an...

Background: The present study aimed to determine whether energy drink (ED) formulas containing 140 and 100 mg of caffeine have the potential to alter excess postexercise oxygen consumption (EPOC) responses after an incremental exercise test in males and females. Materials and Methods: Participants were submitted to incremental tests to exhaustion a...

Creatine (Cr) is a ubiquitous molecule that is synthesized mainly in the liver, kidneys, and pancreas. Most of the Cr pool is found in tissues with high-energy demands. Cr enters target cells through a specific symporter called Na+/Cl−-dependent Cr transporter (CRT). Once within cells, creatine kinase (CK) catalyzes the reversible transphosphorylat...

Although creatine has been mostly studied as an ergogenic aid for exercise, training, and sport, several health and potential therapeutic benefits have been reported. This is because creatine plays a critical role in cellular metabolism, particularly during metabolically stressed states, and limitations in the ability to transport and/or store crea...

BACKGROUND One-third of older adults have maladaptive fall risk appraisal (FRA), a condition in which there is a discrepancy between a level of fear of falling (FOF) and physiological fall risk (balance performance). Older adults who overestimate their physiological fall risk and report high fear of falling are less likely to participate in physica...

Background One-third of older adults have maladaptive fall risk appraisal (FRA), a condition in which there is a discrepancy between the level of fear of falling (FOF) and physiological fall risk (balance performance). Older adults who overestimate their physiological fall risk and report a high FOF are less likely to participate in physical activi...

Following critical evaluation of the available literature to date, The International Society of Sports Nutrition (ISSN) position regarding caffeine intake is as follows: 1. Supplementation with caffeine has been shown to acutely enhance various aspects of exercise performance in many but not all studies. Small to moderate benefits of caffeine use...

Background: Thermogenic fitness drink formulas (TFD) have been shown to increase energy expenditure and markers of lipid metabolism. The purpose of the current study was to compare TFD formulas containing different caffeine concentrations versus a placebo drink on energy expenditure and lipid metabolism at rest and during exercise. Methods: Thir...

Purpose of review: The interest in the use of beta-hydroxy-beta-methylbutyrate (HMB) as an intervention to prevent and treat sarcopenia has increased over recent years. The purpose of this review is to explore recent evidence pertaining to the mechanism of action of HMB and how this may influence changes in lean mass and strength in older persons...

This study examined the cardiac autonomic responses, as measured by heart rate variability (HRV), during cycling exercise and short-term rest after energy drink consumption. Seventeen participants (seven males and 10 females; age: 22.8 ± 3.5 years; BMI: 24.3 ± 3.3 kg/m2) completed this double-blind, placebo-controlled, counterbalanced crossover des...

The purpose of this trial was to examine the effects of self-selected exercise intensities plus either whey protein or placebo supplementation on vital signs, body composition, bone mineral density, muscle strength, and mobility in older adults. A total of 101 participants aged 55 years and older (males [ n = 34] and females [ n = 67]) were evaluat...

The purpose of this study was to assess the maturity-related differences in the aerobic and anaerobic adaptations to sprint interval training (SIT) among youth male athletes. Twenty-seven youth male athletes were assessed for years from peak height velocity (PHV) and classified into prepubescent (PRE, n = 7, years from PHV = -2.21 ± 0.47 years), pe...

A one-group pre/posttest study was conducted to examine the feasibility and effect size of an 8-week physio-feedback and exercise program (PEER) on improving balance, muscle strength, and fall risk. Nineteen participants (mean age = 76 years) received the intervention, which included visual physio-feedback by the BTrackS™ Assess Balance System, cog...

The current study aimed to categorize fall risk appraisal and quantify discrepancies between perceived fall risk measured subjectively using the short Fall Efficacy Scale-International and physiological fall risk measured objectively using the portable BTrackS™ Assess Balance System. One hundred two community-dwelling older adults were evaluated in...

Post-activation potentiation likely acutely improves power-based performance; however, few studies have demonstrated improved endurance performance. Forty collegiate female rowers performed isometric potentiating (ISO), dynamic potentiating (DYN) and control (CON) warm-up protocols on a rowing ergometer, followed by a three-minute all-out test to e...

Background: Sex-based differences in metabolism and morphological characteristics may result in unique exercise responses during periods of limited oxygen availability. Purpose: To evaluate the effects of moderate normobaric hypoxia on the parameters of the work-time relationship during upper body exercise in women. Materials and Methods: Thirtee...

To examine the preliminary efficacy of an 8-week judo program to promote moderate-to-vigorous physical activity (MVPA) and reduce sedentary behavior (SB) in youth with Autism Spectrum Disorder (ASD). Fourteen children diagnosed with ASD participated in a weekly judo program over a period of 8 weeks. Participants wore an Actigraph accelerometer to m...

Objectives: 1) examine the preliminary effectiveness of the Physio-feEdback and Exercise pRogram (PEER) for shifting maladaptive to adaptive fall risk appraisal and reducing fall risk, 2) determine the participants’ feedback and acceptability of the program. Methods: Forty-one older adults were assigned to either PEER intervention or attention cont...

In this Position Statement, the International Society of Sports Nutrition (ISSN) provides an objective and critical review of the literature pertinent to nutritional considerations for training and racing in single-stage ultra-marathon. Recommendations for Training. i) Ultra-marathon runners should aim to meet the caloric demands of training by fol...

Purpose Recent evidence suggests that deception may not be necessary for placebos to improve clinical outcomes. We tested the hypothesis that placebo and open-label placebo (OLP) treatments would acutely improve strength and voluntary activation, as well as minimize neuromuscular fatigue, in untrained participants. Methods Twenty-one males (n = 11...

Ultrasonography of the lower body typically encompasses supine rest due to fluid shifts affecting tissue size and composition. However, vastus lateralis (VL) examination is completed in the lateral recumbent position, and this positional change may influence morphology and its ability to predict function. This study aimed to examine the effect of p...

The purpose of this study was to identify the effects of superficial cooling on physiological responses while training in a warm, humid environment during an international judo training camp. Sixteen judokas (8 women and 8 men) participated in the experiment. Four high-level women and four men were randomly assigned to wear a cooling vest (vest gro...

β-alanine supplementation increases muscle carnosine content and improves anaerobic exercise performance by enhancing intracellular buffering capacity. β-alanine ingestion in its traditional rapid-release formulation (RR) is associated with the symptoms of paresthesia. A sustained-release formulation (SR) of β-alanine has been shown to circumvent p...

The aim of this study was to compare muscle oxygenation of the vastus lateralis during a high-volume isokinetic resistance exercise protocol (HVP) between young adult (YA) and middle-aged adult (MA) men. Twenty recreationally trained men were assigned to either the YA (age 21.8±2.0 years, body mass 90.7±11.6 kg, body height 179±4.7 cm) or MA (age 4...

Purpose This study evaluated the contributions of somatic maturity (years from estimated peak height velocity) and training experience as developmental indicators of muscle morphology, biomechanical parameters, and bilateral asymmetries in youth judo athletes. Methods Twenty-six judo athletes aged 8–18 years (mean ± SD; age = 12.9 ± 2.6 years, mat...