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Introduction
My lab studies the form and function of human skeletal muscle. Specifically, we use in vivo human subject research models to examine changes in muscle strength, size, and function. As a result, I have authored or co-authored over 200 peer-reviewed scientific articles, 200 conference research presentations, and a textbook entitled "Laboratory Manual for Exercise Physiology, Exercise Testing, and Physical Fitness."
Additional affiliations
August 2020 - present
August 2003 - July 2005
August 2012 - July 2020
Publications
Publications (427)
This study compared absolute and relative measurements of peak torque (PT), mean power (MP), and rate of velocity development (RVD) during isometric and isokinetic elbow flexion muscle actions in pre- and post-pubescent males and females.
Forty children participated (pre-pubescent: mean ± 95% confidence interval age = 9.79 ± 0.35 years, n = 10 male...
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...
Shoemaker, ME, Smith, CM, Gillen, ZM, and Cramer, JT. Sex differences in test-retest reliability of near-infrared spectroscopy during postocclusive reactive hyperemia of the vastus lateralis. J Strength Cond Res XX(X): 000–000, 2023—The purpose of this study was to determine test-retest reliability for vascular reactivity measures and ranges for no...
Metabolic flexibility can be defined as the ability of the skeletal muscle to adjust its utilization of substrate pathways [...]
PurposeThe purpose of this study was to examine the responses of electromyographic (EMG) and mechanomyographic (MMG) amplitude across the torque spectrum in pre- and post-pubescent males and females.Methods
Forty pre-pubescent (mean ± 95% confidence interval, age = 9.79 ± 0.35 years, n = 10 males, n = 10 females) and post-pubescent (age = 17.23 ± 0...
PurposeThe purpose of this study was to examine peak torque (PT), mean power (MP), electromyographic (EMG) amplitude, mechanomyographic (MMG) amplitude, and neuromuscular efficiency from EMG and MMG amplitude (NMEEMG and NMEMMG, respectively) across the velocity spectrum in children versus adolescents.Methods
Seventeen children (n = 8 males, n = 9...
Little is known about potential protective factors for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), referred to as COVID-19. Suboptimal vitamin D status is a risk factor for immune dysfunction, respiratory tract infections (RTIs), and viral infections. Supplementation of vitamin D (2000–4000 IU) has decreased incidence and complica...
There is conflicting evidence of the roles vitamin D and iron have in isolation and combined in relation to muscle health. The purpose of this narrative review was to examine the current literature on the roles that vitamin D and iron have on skeletal muscle mass, strength, and function and how these nutrients are associated with skeletal muscle he...
Malnutrition and sarcopenia commonly overlap and contribute to adverse health outcomes. Previously, chronic supplementation with two oral nutritional supplements (ONS), control (CONS) and experimental ONS enriched with protein, vitamin D and β-hydroxy β-methylbutyrate (HMB) (EONS), improved muscle strength and quality in malnourished sarcopenic old...
Background:
Metabolic flexibility is the ability of skeletal muscle to adapt fuel utilization to the demand for fuel sources [carbohydrates (CHO) and fats (FAT)]. The purpose of this study was to explore muscle energy metabolism and metabolic flexibility under various conditions in sarcopenic (S) versus nonsarcopenic (NS) older adults.
Methods:...
Purpose: To examine and compare the effects of three days of dynamic constant external resistance (DCER) and isokinetic (ISOK) training and subsequent detraining on thigh muscle cross-sectional area (TMCSA) and thigh lean mass (TLM), ISOK peak torque (PT), DCER strength, isometric force, muscle activation, and percent voluntary activation (%VA). Me...
INTRODUCTION
As virtual education becomes more widespread, particularly considering the recent COVID-19 pandemic, studies that assess the impact of online teaching strategies are vital. Current anatomy curriculum at Paul L. Foster School of Medicine consists of self-taught PowerPoint material, clinical vignette-centered team-based learning (dry lab...
BACKGROUND: Low-load resistance training with blood flow restriction (LL + BFR) attenuated delayed onset muscle soreness (DOMS) under some conditions. OBJECTIVE: The purpose of this study examined the effects of reciprocal concentric-only elbow flexion-extension muscle actions at 30% of peak torque on indices of DOMS. METHODS: Thirty untrained wome...
PurposeThe purpose of this study was to compare measurements of muscle strength, size, and activation of the forearm flexors in pre- and post-pubescent males and females.Methods
Forty pre-pubescent (mean ± 95% confidence interval, age = 9.79 ± 0.35 years, n = 10 males, n = 10 females) and post-pubescent (age = 17.23 ± 0.58 years, n = 10 males, n =...
Objectives
To examine differences in metabolic flexibility during submaximal aerobic exercise in sarcopenic (S) and non-sarcopenic (NS) older adults.
Methods
Twenty-two older adults (mean age ± SE = 77 ± 2) were categorized as NS (n = 11) and S (n = 11) based on grip strength and muscle mass. Participants completed an aerobic, steady-state 10-min...
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...
Purpose
The purpose of this investigation was to examine the individual and composite patterns of responses and time-course of changes in muscle size, strength, and edema throughout a 4 week low-load blood flow restriction (LLBFR) resistance training intervention.
Methods
Twenty recreationally active women (mean ± SD; 23 ± 3 years) participated in...
The purposes of this study were to determine whether countermovement jump (CMJ) force profiles differ for jumps in which peak force occurred at the low position of the countermovement (LP) compared to jumps in which peak force did not occur at the low position of the countermovement (NLP), and compare relationships among CMJ and isokinetic metrics...
Background & Aims
Consumption of rapid digesting sugars by children are under increased scrutiny because of their contribution to unhealthy weight gain. Previous studies in adults and children have suggested that altering the blend of carbohydrates (CHOs) consumed may cause shifts in substrate utilization. The purpose of this study was to examine t...
PurposeThis study examined changes in vertical jump performance with progressively greater eccentric pre-loading in relation to growth and development in young female athletes.Methods
Twenty young female athletes ranging from 9 to 17 years old performed the following vertical jumps in random order: static jumps (SJs), counter-movement jumps (CMJs),...
The purpose of this study was to use polynomial regression analyses to examine the torque- and power-velocity relationships and calculate and compare the vertices of these nonlinear models, and how they relate to measurements of muscle size and maximal strength, between male and female children and adolescents during maximal isokinetic leg extensio...
Gillen, ZM, Shoemaker, ME, McKay, BD, Bohannon, NA, Gibson, SM, and Cramer, JT. Peak torque explains more unique variability in growth measurements than rate of torque development in young boys and girls. J Strength Cond Res XX(X): 000-000, 2020-This study reported test-retest reliability and evaluated collinearity for isometric leg extension and f...
Purpose:
The purposes of the present study were to (a) examine resting metabolism, substrate utilization, and endogenous versus exogenous carbohydrate (CHO) oxidation before and after 30-g rapidly-digesting carbohydrate (RDC) ingestion using indirect calorimetry and breath test analysis of stable isotope concentrations in pre-pubescent children an...
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...
PurposeThe purpose of this study was to examine the relationships among leg extension strength, explosive strength, muscle activation, and measurements of growth to predictions of vertical jump performance in youth athletes.Methods
Height, body mass, skinfolds, and quadriceps femoris muscle cross-sectional area were measured in 39 sports active chi...
Bohannon, NA, Gillen, ZM, Shoemaker, ME, McKay, BD, Gibson, SM, Cramer, JT. Test-Retest Reliability of Static and Counter-Movement Power Push-Up Tests in Young Male Athletes. J Strength Cond Res 34(9): 2456-2464, 2020-The primary purpose of this study was to evaluate test-retest reliability of the static (SP) and countermovement (CMP) power push-up...
Gillen, ZM, Shoemaker, ME, McKay, BD, Bohannon, NA, Gibson, SM, and Cramer, JT. Influences of the stretch-shortening cycle and arm swing on vertical jump performance in children and adolescents. J Strength Cond Res XX(X): 000-000, 2020-This study compared the influences of the stretch-shortening cycle and arm swing on vertical jump performance duri...
Purpose
Low-load venous blood flow restriction resistance training (RT + BFR) has been demonstrated to increase muscle strength to a greater degree than low-load non-BFR resistance training (RT) during isotonic training, but no previous investigations have examined RT + BFR versus RT during isokinetic training. The purpose of the present study was...
This study measured peak force (PF), peak rate of force development (PRFD), peak power (PP), concentric impulse, and eccentric impulse during static jump (SJ), countermovement jump (CMJ), and drop jump (DJ) in youth athletes to examine changes in vertical jump power with progressively greater eccentric preloading in relation to age, maturity, and m...
Background:
The purpose of this study was to examine relationships among biomarkers of iron status, athletic performance, growth and development, and dietary intakes in pre-adolescent and adolescent male and female athletes.
Methods:
Two-hundred and forty-nine male (n = 179) (mean ± standard deviation for age = 12.0 ± 2.1 years, height = 156.3 ±...
Jenkins, NDM, Miramonti, AA, Hill, EC, Smith, CM, Cochrane-Snyman, KC, Housh, TJ, and Cramer, JT. Mechanomyographic amplitude is sensitive to load-dependent neuromuscular adaptations in response to resistance training. J Strength Cond Res XX(X): 000-000, 2019-We examined the sensitivity of the mechanomyographic amplitude (MMGRMS) and frequency (MMG...
Objective: The purpose of this study was to determine the prevalence of poor iron status in young athletes throughout the stages of iron deficiency and assess sex differences with iron deficiency in relation to growth and development and dietary intake.
Methods: A cross-sectional analysis evaluated young male and female athletes (n = 91) between th...
The purpose of this study was to examine the effects of an online sports nutrition curriculum on athletic performance and iron status in high school-aged male and female athletes. A repeated-measures design evaluated forty-three males (n=18) and females (n=25). Athletic performance and biomarkers of iron status were measured before and after partic...
Purpose
To compare measurements of muscle strength, size, and neuromuscular function among pre-adolescent and adolescent boys and girls with distinctly different strength capabilities.
Methods
Fifteen boys (mean age ± confidence interval: 13.0 ± 1.0 years) and 13 girls (12.9 ± 1.1 years) were categorized as low strength (LS, n = 14) or high streng...
Purpose:
The purpose of this study was to determine magnitudes of differences for anthropometric and athletic performance scores between high school and elite college-level American football players.
Method:
Participants included high school-age (n = 3,666) athletes who participated in American football combines, as well as elite college-level (...
This study compared athletic performance differences among high school American football combine participants originating from states of different population sizes. High school-aged American football players (n=7,214) who had participated in athletic performance combines between March 2015 and January 2016 were included in this analysis. Data inclu...
McKay, BD, Miramonti, AA, Gillen, ZM, Leutzinger, TJ, Mendez, AI, Jenkins, NDM, and Cramer, JT. Normative reference values for high school-aged American football players: Proagility drill and 40-yard dash split times. J Strength Cond Res XX(X): 000-000, 2018-The purpose of this short report was to provide test- and position-specific normative refer...
PURPOSE: To examine the changes in mechanomyographic (MMG) amplitude following 3 and 6 weeks of 80% vs. 30% one repetition maximum (1RM) resistance training in the leg extensors.
METHODS: Twenty-six healthy men (23.1 ± 4.7 years; height = 180.6 ± 6.0 cm; weight = 80.0 ± 14.1 kg) participated in this randomized, repeated measures, between-group des...
Athletic performance combine tests are used by high school, collegiate, and professional American football programs to evaluate performance; however, limited evidence is available on performance combine test results in youth athletes. The purposes of this study were to report test-retest reliability statistics and evaluate concurrent validity among...
The purpose of the present report was to provide test- and position-specific normative reference values for combine test results based on a large, nationally-representative sample of high school-aged American football players in their freshman, sophomore, and junior classes. Cross-sectional anthropometric and performance data were obtained from 12...
The purpose of the present study was to investigate differences among player positions at three grade levels in elite, collegiate-prospective American football players. Participants' data (n = 7,160) were analyzed for this study [mean height (Ht) ± standard deviation (SD) = 178 ± 7 cm, weight (Wt) = 86 ± 19 kg]. Data were obtained from 12 different...
The purpose of this study was to evaluate stature (HT), weight (WT), body mass index (BMI), and obesity prevalence based on BMI categories in a large sample (n = 7,175) of high school American football players enrolled as freshmen, sophomores, or juniors. Players were categorized by their positions: offensive linemen (OL), defensive linemen (DL), t...
University of Nebraska’s Supplemental Nutrition Assistance Program-Education (SNAP-Ed) implements interventions to help the target audience establish healthy eating habits and physically active lifestyles. This report assesses the impact of eight, 30-min CATCH ® nutrition lessons on 6 categories for youth: healthy eating habits (EH), healthy behavi...
The power push-up (PPU) test is an explosive upper-body test performed on a force plate and is currently being used in high school football combines throughout the U.S. The purpose of this study was to quantify the reliability of the PPU test based on age and starting position (knees vs. toes) in young athletes. Sixty-eight boys (mean ± standard de...
We examined the neuromuscular adaptations following 3 and 6 weeks of 80 vs. 30% one repetition maximum (1RM) resistance training to failure in the leg extensors. Twenty-six men (age = 23.1 ± 4.7 years) were randomly assigned to a high- (80% 1RM; n = 13) or low-load (30% 1RM; n = 13) resistance training group and completed leg extension resistance t...
The optimal resistance training program to elicit muscle hypertrophy has been recently debated and researched. Although 3 sets of 10 repetitions at 70-80% of the 1-repetition maximum (1RM) is widely recommended, recent studies have shown that low-load (∼30% 1RM), high-repetition (3 sets of 30-40 repetitions) resistance training can elicit similar m...
Background:
Recently, passive musculotendinous stiffness (MTS) has been assessed manually in the field; however, when conducting these types of assessments, the stretching velocity must be controlled to avoid eliciting the stretch reflex, which can be observed by increased electromyographic (EMG) amplitude of the stretched muscles and greater resi...
Objective
The purpose of the present investigation was to examine the effect of sex on maximal voluntary isometric contraction (MVIC) torque and the EMG and MMG responses as a result of fatiguing, intermittent, submaximal (65% of MVIC), isometric elbow flexion muscle contractions.
Methods
Eighteen men and women performed MVIC trials before (pretes...
Objectives:
To determine the test-retest reliability and minimum detectable change scores for seven common clinical measurements of muscle strength and physical function in a multiethnic sample of sarcopenic, malnourished men and women.
Design:
Each participant visited the laboratory seven times over 25 to 26 weeks. Reliability was assessed for...
Background:
Recent evidence suggests that nutritional interventions may improve muscle outcomes in malnutrition and sarcopenia.
Objectives:
We evaluated the effects of 2 high-quality oral nutritional supplements (ONS) differing in amount and type of key nutrients in older adult men and women.
Design:
A multicenter, randomized, double-blinded,...
Introduction:
This study examined relationships among mechanomyographic (MMG), electromyographic (EMG), and peak twitch torque (PTT) responses as well as test-retest reliability when recorded during recruitment curves in the soleus muscle.
Methods:
PTT, EMG (M-wave, H-reflex), and MMG responses were recorded during recruitment curves in 16 subje...
Numerous conditions and types of physical activity (e.g., exercise, aging, muscle-related diseases) can influence muscle fiber types and the proteins expressed. To date, muscle fibers can only be characterized by actually obtaining a tissue sample using the invasive muscle biopsy procedure. Mechanomyography (MMG) is the assessment of the vibration...
The purpose of this study was to investigate the effects of 8 weeks at 6 g per day of RAR CLA versus placebo on cognitive function and handgrip performance in older men and women. Sixty-five (43 women, 22 men) participants (mean ± SD; age = 72.4 ± 5.9 yrs; BMI = 26.6 ± 4.2 kg·m-2) were randomly assigned to a RAR CLA (n = 30: 10 men, 20 women) or pl...
The purpose of this study was to investigate the effects of 4-weeks of high- versus low-load resistance training to failure on rate of torque development (RTD), electromechanical delay (EMD), and contractile twitch characteristics. Fifteen men (mean±SD; age=21.7±2.4 yrs) were randomly assigned to either a high- (80% 1RM; n=7) or low-load (30% 1RM;...
This study examined the electromyographic (EMG) responses from the vastus medialis (VM) for electrodes placed over and away from the innervation zone (IZ) during a maximal voluntary isometric contraction (MVIC) and sustained, submaximal isometric muscle action. A linear electrode array was placed on the VM to identify the IZ and muscle fiber pennat...
BACKGROUND: Previous investigations have examined the torque and neuromuscular responses to maximal concentric and isometric muscle actions. The literature, however, has paid less attention to the effects of performing maximal eccentric muscle actions. Furthermore, the available information in this regard is contradictory. OBJECTIVE: The purpose of...
Short-term resistance training has been shown to increase isokinetic muscle strength and performance after only two to nine days of training. The purpose of this study was to examine the effects of three days of unilateral dynamic constant external resistance (DCER) training and detraining on the strength of the trained and untrained legs. Nineteen...
In this response, we addressed the specific issues raised by Vigotsky et al. and clarified (1) our methods and adherence to electromyographic signal reporting standards, (2) our interpretation of EMG amplitude, and (3) our interpretation of EMG mean power frequency.
This study examined patterns of responses for physiological and perceptual variables during cycle ergometry at a constant rate of perceived exertion (RPE) within the moderate and heavy exercise intensity domains. Nineteen (mean age 21.3 ± 0.5 years; 43.4 ± 2.0 mL·kg−1·min−1 V ˙ O 2 Peak ) moderately trained cyclists performed an incremental test to...
The purpose of this study was to investigate the hypertrophic, strength, and neuromuscular adaptations to 2- and 4-weeks of resistance training at 80% versus 30% 1RM in untrained men. Fifteen untrained men (mean+/-SD; age=21.7+/-2.4 yrs; weight=84.7+/-23.5 kg) were randomly assigned to either a high- (n=7) or low-load (n=8) resistance training grou...
The purposes of this study were to examine the effects of the velocity of repeated eccentric muscle actions on the torque and neuromuscular responses during maximal isometric and eccentric muscle actions. Twelve resistance trained men performed 30 repeated, maximal, eccentric, isokinetic muscle actions at randomly order velocities of 60, 120, or 18...
This study compared electromyographic (EMG) amplitude, the number of repetitions completed, and exercise volume during three sets to failure of high- (80% 1RM) versus low-load (30% 1RM) forearm flexion resistance exercise on a subject-by-subject basis. Fifteen men were familiarized, completed forearm flexion 1RM testing. Forty-eight to 72 h later,...