Differences in muscle energy metabolism and metabolic flexibility between sarcopenic and nonsarcopenic older adults.

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: Twenty-two older adults aged 65 years or older were categorized as NS [n = 11; mean ± standard deviation (SD); age = 73.

Impact of slow versus rapid digesting carbohydrates on substrate oxidation in pre-pubertal children: A randomized crossover trial.

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 the effects of consuming a slow digesting carbohydrate (SDC) and rapid digesting carbohydrate (RDC) on CHO and fat oxidation, glucose, and insulin responses at rest, during exercise, and post-exercise rest in pre-pubescent children.

Test-Retest Reliability of Static and Countermovement Power Push-Up Tests in Young Male Athletes.

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 test in young male athletes.

Endogenous versus exogenous carbohydrate oxidation measured by stable isotopes in pre-pubescent children plus C abundances in foods consumed three days prior.

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 and (b) report the C abundances in foods consumed for three days prior.

Methods: Nineteen children (n = 10 boys, n = 9 girls) at Tanner stage I or II participated (mean age ± 95% CI = 9.84 ± 0.

Peak Torque Explains More Unique Variability in Growth Measurements than Rate of Torque Development in Young Boys and Girls.

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 34(9): 2507-2514, 2020-This study reported test-retest reliability and evaluated collinearity for isometric leg extension and flexion peak torque (PT) and rate of torque development (RTD) in young boys and girls.

Changes in Strength, Mobility, and Body Composition Following Self-Selected Exercise in Older Adults.

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 evaluated before and after 12 weeks of self-selected, free-weight resistance exercise plus 30 min of self-paced walking three times per week. The participants were randomized into two groups: whey protein (n = 46) or placebo (n = 55).

Influences of the Stretch-Shortening Cycle and Arm Swing on Vertical Jump Performance in Children and Adolescents.

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 36(5): 1245-1256, 2022-This study compared the influences of the stretch-shortening cycle and arm swing on vertical jump performance during static jumps (SJs), counter-movement jumps (CMJs), and CMJs with arm swing (CMJAs) in young male and female athletes.

Effects of Eccentric Preloading on Concentric Vertical Jump Performance in Youth Athletes.

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 muscle mass. Twenty-one males ranging from 6 to 16 years old performed the following vertical jumps in a random order: SJ, CMJ, and DJ from drop heights of 20, 30, and 40 cm (DJ20, DJ30, and DJ40, respectively). Measurements included PF, PRFD, PP, eccentric impulse, and concentric impulse for each vertical jump condition.

Sex-specific relationships among iron status biomarkers, athletic performance, maturity, and dietary intakes in pre-adolescent and adolescent athletes.

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.

High Prevalence of Poor Iron Status Among 8- to 16-Year-Old Youth Athletes: Interactions Among Biomarkers of Iron, Dietary Intakes, and Biological Maturity.

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. A cross-sectional analysis evaluated young male and female athletes ( = 91) between the ages 8 and 16 years. Anthropometric assessments, body composition, dietary intakes, and blood samples measuring ferritin, soluble transferrin receptor (sTfR), and hemoglobin (Hb) were examined.

Muscle strength, size, and neuromuscular function before and during adolescence.

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.

Performance Differences between National Football League and High School American Football Combine Participants.

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 (n = 5,537) athletes who participated in the National Football League (NFL) scouting combine. Combine data included position; height; weight; 10-, 20-, and 40-yard dash; pro-agility (PA); L-cone drill (LC); vertical jump (VJ); and broad jump (BJ).

State Population Influences Athletic Performance Combine Test Scores in High School-Aged American Football Players.

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 included combine date and location, school state of origin, football position, class, height, weight, 10-, 20-, and 40-yd dash times, pro-agility, L-cone drill, vertical jump, broad jump, and power push-up.

Stature, Body Mass, and Body Mass Index in High School American Football Players: Appropriate Determinants of Obesity Prevalence?

Mendez, AI, Miramonti, AA, Gillen, ZM, McKay, BD, Leutzinger, TJ, and Cramer, JT. Stature, body mass, and BMI in high school american football players: Appropriate determinants of obesity prevalence? J Strength Cond Res 32(11): 3119-3126, 2018-The purpose of this study was to evaluate stature (HT), mass (BM), 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 (OLs), defensive linemen (DLs), tight end, defensive end, linebacker, running back, quarterback, defensive back, and wide receiver.

Normative Reference Values for High School-Aged American Football Players: Proagility Drill and 40-Yard Dash Split Times.

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 34(4): 1184-1187, 2020-The purpose of this short report was to provide test- and position-specific normative reference values for the 10- and 20-yd split times (10YD and 20YD) during the 40-yd dash (40YD) as well as 10-yd split times during the proagility drill (PA) based on a large, nationally representative sample of high school-aged American football players in their freshman, sophomore, and junior classes.

Normative Reference Values for High School-Aged American Football Players.

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. J Strength Cond Res 34(10): 2849-2856, 2020-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.

Test-Retest Reliability and Concurrent Validity of Athletic Performance Combine Tests in 6-15-Year-Old Male Athletes.

Gillen, ZM, Miramonti, AA, McKay, BD, Leutzinger, TJ, and Cramer, JT. Test-retest reliability and concurrent validity of athletic performance combine tests in 6-15-year-old male athletes. J Strength Cond Res 32(10): 2783-2794, 2018-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.

Anthropometric and Athletic Performance Combine Test Results Among Positions Within Grade Levels of High School-Aged American Football Players.

Leutzinger, TJ, Gillen, ZM, Miramonti, AM, McKay, BD, Mendez, AI, and Cramer, JT. Anthropometric and athletic performance combine test results among positions within grade levels of high school-aged American football players. J Strength Cond Res 32(5): 1288-1296, 2018-The purpose of this study was to investigate differences among player positions at 3 grade levels in elite, collegiate-prospective American football players.

Reliability and Sensitivity of the Power Push-up Test for Upper-Body Strength and Power in 6-15-Year-Old Male Athletes.

Gillen, ZM, Miramonti, AA, McKay, BD, Jenkins, NDM, Leutzinger, TJ, and Cramer, JT. Reliability and sensitivity of the power push-up test for upper-body strength and power in 6-15-year-old male athletes. J Strength Cond Res 32(1): 83-96, 2018-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 United States.

Exertional Rhabdomyolysis in a 21-Year-Old Healthy Woman: A Case Report.

McKay, BD, Yeo, NM, Jenkins, NDM, Miramonti, AA, and Cramer, JT. Exertional rhabdomyolysis in a 21-year-old healthy woman: a case report. J Strength Cond Res 31(5): 1403-1410, 2017-The optimal resistance training program to elicit muscle hypertrophy has been recently debated and researched.

Effects of rumenic acid rich conjugated linoleic acid supplementation on cognitive function and handgrip performance in older men and women.

The purpose of this study was to investigate the effects of 8weeks at 6g 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.