Jeffrey R. Stout

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

In this opinion article, we advocate for the combination of creatine monohydrate supplementation and resistance training as a safe and effective non-pharmacological strategy to prevent and treat sarcopenia that should be internationally recognized by health practitioners and public health organizations.

Purpose To characterize the magnitude, timescale, and reliability of changes in functional and systemic outcome markers following moderate (MIR) and high (HIR) isoinertial resistance flywheel squat protocols (FSP). Methods Twenty-four resistance-trained males completed two exercise trials (ET1 & ET2) separated by 32 days. Functional and systemic m...

Objectives: The objective of this study was to examine the difference between the extent of muscle damaging exercise on muscle function variables of vegans and omnivores. Methods: Twenty recreationally trained participants completed the study. Participants were assigned to either vegan (n = 10) or omnivore (n = 10) groups. Subjects completed a c...

Editorial on the Research Topic New insights and advances in body recomposition

Autonomous exercise within nonspecific low back pain rehabilitation is a necessary tool to treat low back pain. The purpose of this study was to quantify adherence and compliance during two different 6-week home-exercise programs. Forty adults were randomly allocated to a gamified and packet group. Adherence, compliance, and system usability assess...

Despite BIA emerging as a clinical tool for assessing older adults, it remains unclear how to calculate whole-body impedance (Z), reactance (Xc), resistance (R), and phase angle (PhA) from segmental values using modern BIA devices that place electrodes on both sides of the body. This investigation aimed to compare both the whole-body and segmental...

Purpose The purpose of this study was to determine the test–retest reliability of critical force (FCr), peak force (Y0), and k (rate constant), during a 5-min intermittent handgrip fatiguing protocol. Methods Seventeen males (n = 8) and females (n = 9) between the ages of 18–55 years old (23.94 ± 6.21 y; 169.16 ± 7.62 cm; 74.24 ± 12.91 kg; 25.74 ±...

Purpose This study aimed to establish a new threshold parameter called the physical working capacity at pain intensity threshold (PWCPIT) using a pain intensity scale and mathematical methods similar to those used to develop the physical working capacity at oxygen consumption threshold (PWCVO2) and physical working capacity at heart rate threshold...

Background Skeletal muscle echo intensity (EI) is associated with functional outcomes in older adults, but resistance training interventions have shown mixed results. Texture analysis has been proposed as a novel approach for assessing muscle quality, as it captures spatial relationships between pixels. Purpose To examine changes in first-order (E...

While resistance training promotes muscle hypertrophy and strength, accessibility of equipment is a barrier. This study evaluated a wearable VAriable Resistance Suit (VARS) as a novel and alternative method to achieve muscle strength improvement. It was hypothesized that by providing adjustable, bi-directional and speed dependent resistance, VARS c...

Context: The hip adductor and abductor muscles play vital roles as stabilizers in the lower-extremity. Their activation during soccer-specific actions is essential, but local muscular fatigue can hinder athletic performance and increase the risk of injury. Design: This study aimed to observe the variations in frontal plane hip strength in female...

ABSTRACT Position statement: The International Society of Sports Nutrition (ISSN) provides an objective and critical review of the use of a ketogenic diet in healthy exercising adults, with a focus on exercise performance and body composition. However, this review does not address the use of exogenous ketone supplements. The following points summar...

Purpose: To measure the change in pain and disability during and after a 6-week gamified delivery of home exercise compared to a take-home packet. Materials and methods: A 6-week at-home exercise protocol included participants randomly allocated to a gamified delivery group or packet group. The exercise protocol included the plank, side plank, f...

Limb immobilization causes rapid declines in muscle strength and mass. Given the role of the nervous system in immobilization‐induced weakness, targeted interventions may be able to preserve muscle strength, but not mass, and vice versa. The purpose of this study was to assess the effects of two distinct interventions during 1 week of knee joint im...

Muscle strength declines ∼3% per year after the age of 70. Resistance training guidelines for older adults are often based on free-weight and machine exercises, which may be inaccessible and lack carryover to activities of daily living. We tested the hypothesis that resistance training adaptations in older adults are task-specific. Thirty adults (8...

Protein supplementation often refers to increasing the intake of this particular macronutrient through dietary supplements in the form of powders, ready-to-drink shakes, and bars. The primary purpose of protein supplementation is to augment dietary protein intake, aiding individuals in meeting their protein requirements, especially when it may be c...

Introduction: Fall Risk Appraisal (FRA), a process that integrates perceived and objective fall risk measures, serves as a crucial component for understanding the incongruence between fear of falling (FOF) and physiological fall risk in older adults. Despite its importance, scant research has been undertaken to investigate how habitual physical act...

Purpose The US Centers for Disease Control and Prevention (CDC) has implemented the Stopping Elderly Accidents, Deaths, and Injuries (STEADI) initiative. This initiative provides an algorithm for fall risk screening. However, the algorithm has the potential to overcategorize individuals as high risk for falling upon initial screening, which may bur...

Caffeine is a popular ergogenic aid that has a plethora of evidence highlighting its positive effects. A Google Scholar search using the keywords “caffeine” and “exercise” yields over 200,000 results, emphasizing the extensive research on this topic. However, despite the vast amount of available data, it is intriguing that uncertainties persist reg...

Objectives This investigation examined the effects of continuous (CBFR) and intermittent (IBFR) blood flow restriction (BFR) applied during sprint interval training (SIT) on performance and neuromuscular function. Methods Fifteen men completed a randomized bout of SIT with CBFR, IBFR, and without BFR (No-BFR), consisting of 2, 30-s maximal sprints...

This manuscript represents the second phase of a clinical trial designed to examine the effects of knee joint immobilization and retraining on muscle strength and mass. In Phase 2, we examined sex differences in the recovery of multiple indices of muscle quality after a resistance training-based rehabilitation program. Following 1 week of immobiliz...

Objectives To compare activation ratios of the transverse abdominis (TrA) during an abdominal draw-in maneuver (ADIM) and abdominal obliques during a golf swing, with and without ultrasound biofeedback, and to determine intrarater reliability of these ultrasound thickness measures. Design Single-session crossover study. Setting Laboratory. Parti...

Combat sports athletes seeking a competitive edge often engage in weight management practices to become larger than their opponents, which ultimately includes periods of gradual weight loss, rapid weight loss, and weight regain. This pattern of weight loss and regain is known as weight cycling and often includes periods of low energy availability,...

Skeletal muscle is the largest organ system in the human body and plays critical roles in athletic performance, mobility, and disease pathogenesis. Despite growing recognition of its importance by major health organizations, significant knowledge gaps remain regarding skeletal muscle health and its crosstalk with nearly every physiological system....

Body Fat Mass (BFM) is a crucial body composition measurement serving as a predictor for various health conditions and mortality in older adults. However, limited research has been conducted to investigate how upper limb BFM associates with anthropometric measurements and handgrip strength (HGS) in older adults. In this cross-sectional study, 119 o...

Approximately 43% of older adults are affected by fear of falling (FOF). A portion of those affected by FOF have irrational fall risk appraisal (FRA) which means they have a high FOF despite normal balance. This secondary analysis aimed to examine the 18% of the 124 study participants living with irrational FRA from the RO3AG06799-0 data source. De...

Psychological factors related to appetitive and avoidant motivation, perceptions of aging, and regulatory focus (promotion focus on gains versus a prevention focus on non-losses) are likely to play an important role in predicting one’s fear of falling (FOF) and resulting impact on physical activity engagement. This pilot study aimed to investigate...

Both physical activity (PA) and sedentary behavior (SB) have been independently linked with health outcomes in older adults. However, limited research has been done to investigate how different combinations of these behaviors influence their body composition and functional balance. This cross-sectional study examined the associations of mutually ex...

Fall Risk Appraisal Matrix (FRAM) is vital for understanding the discrepancy between perceived fall risk (i.e., Fear of Falling, FOF) and physiological fall risk (i.e., balance performance) in older adults. However, little is known about how habitual physical activity (PA) levels, expressed in Monitor Independent Movement Summary (MIMS) units, diff...

Balance performance is a key predictor of falls, contributing to an increased risk of chronic disease and future falls in older adults. In this study, we aimed to characterize the effects of age, gender, and body mass index (BMI) on changes in balance over time. BTrackS, a portable and inexpensive technology system, was utilized to objectively meas...

Emerging sensing techniques, which are easily transportable, user-friendly, and cost-effective, may reveal new possibilities in monitoring daily objectively measured physical activity (PA) and fall risk appraisal (FRA) identification. We used a Smoothing Spline Analysis of Variance (SS-ANOVA) to profile the daily PA using accelerometer-based device...

Body composition is an important determinant of physical fitness and overall health in older adults. Body mass index (BMI) is currently the standard used to categorize clinical thresholds for body composition (underweight, normal weight, overweight, obese). However, BMI does not account for key aspects of body composition like skeletal muscle mass...

Adequate hydration is an important modifiable determinant of overall physical health within community-dwelling older adults. Research and clinical practice often use urine osmolarity and bioelectrical impedance analysis (BIA) to assess hydration status. Prior evidence links inadequate hydration to increased obesity, typically measured by body mass...

Integrating assistive technologies into fall prevention interventions could improve health outcomes, but older adults in low-income settings face greater challenges with technology use due to factors such as cost, access, and location. We examined the acceptance of technology in low-income older adults and the factors associated with their acceptan...

Boffey, D, DiPrima, JA, Kendall, KL, Hill, EC, Stout, JR, and Fukuda, DH. Influence of body composition, load-velocity profiles, and sex-related differences on army combat fitness test performance. J Strength Cond Res 37(12): 2467–2476, 2023—The Army Combat Fitness Test (ACFT) became the U.S. Army's mandatory physical fitness test in April of 2022....

BACKGROUND Older adults experience a significant decline in muscle quality and function with aging. Phase angle (PhA) and impedance ratio (IR) measured via bioelectrical impedance analysis (BIA) are both indicative of physical function and cellular health. OBJECTIVE This study aim is to characterize the relationships between hand grip strength (HG...

Background Older adults experience a significant decline in muscle integrity and function with aging. Early detection of decreased muscle quality can pave the way for interventions to mitigate the progression of age-related physical declines. Phase angle (PhA) and impedance ratio (IR) are measures of muscle integrity, which can be assessed quickly...

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...

Herring, CH, Beyer, KS, Redd, MJ, Stout, JR, and Fukuda, DH. Utility of novel rotational load-velocity profiling methods in collegiate softball players. J Strength Cond Res 38(1): 136–145, 2024—The purpose of this study was to determine the reliability of bat swing (BS) and rotational medicine ball throw (RMBT) load-velocity profiling (LVP) methods...

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...

Background Interdisciplinary evaluation of older adults’ health care is a priority in the 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 c...

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...

Wizenberg, AM, Gonzalez-Rojas, D, Rivera, PM, Proppe, CE, Laurel, KP, Stout, JR, Fukuda, DH, Billaut, F, Keller, JL, and Hill, EC. Acute effects of continuous and intermittent blood flow restriction on sprint interval performance and muscle oxygen responses. J Strength Cond Res XX(X): 000-000, 2023-This investigation aimed to examine the acute effe...

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...