Background Individuals who are living with obesity often adopt alternative lower limb walking mechanics compared to persons with a healthy weight. Stair negotiation is a common activity of daily living that, when used consistently with diet and other physical activity, can help promote the reversal of health-related risk factors associated with people who are obese. The purpose of this study was to determine how stair negotiation affects normalized and non-normalized peak knee extension and abduction moments in young adults who live with obesity (BMI between 30 and 40 kg/m2) compared to adults with a healthy weight (BMI between 18.5 and 25 kg/m2). Methods Fifteen young adults living with obesity and fifteen with a healthy weight performed stair ascent and descent walking trials on a 3-step instrumented staircase at a self-selected walking speed. A one-way ANCOVA (covariate: gait speed) was used to compare knee moment variables between groups. Results No significant differences were found between groups in peak knee joint moments normalized to body mass. The individuals living with obesity demonstrated significantly larger non-normalized peak knee extension moments during stair ascent and descent but no differences in the non-normalized peak knee abduction moments for stair ascent or descent. Conclusion Results of this study indicate differences in non-normalized peak knee extension moments between BMI groups. The young age of the obese group may have contributed to minimal differences overall. Future research should determine how these findings differ in an older obese population and how using a handrail would affect these results.

Background: The most common symptom of peripheral artery disease (PAD) is intermittent claudication that involves the calf, thigh, and/or buttock muscles. How the specific location of this leg pain is related to altered gait, however, is unknown.Objectives: We hypothesized that because the location of claudication symptoms uniquely affects different leg muscle groups in people with PAD, this would produce distinctive walking patterns. Methods: A total of 105 participants with PAD and 35 age-matched older volunteers without PAD (CTRL) were recruited. Participants completed walking impairment questionnaires (WIQ), Gardner-Skinner progressive treadmill tests, the six-minute walk test, and we performed an advanced evaluation of the biomechanics of their overground walking. Participants with PAD were categorized into 4 groups according to their stated pain location(s): calf only (C, n = 43); thigh and calf (TC, n = 18); buttock and calf (BC, n = 15); or buttock, thigh, and calf (BTC, n = 29). Outcomes were compared between CTRL, C, TC, BC and BTC groups using a one-way ANOVA with post-hoc comparisons to identify and assess statistically significant differences.Results: There were no significant differences between CTRL, C, TC, BC and BTC groups in distances walked or walking speed when either pain-free or experiencing claudication pain. Each participant with PAD had significantly dysfunctional biomechanical gait parameters, even when pain-free, when compared to CTRL (pain -free) walking data. During pain-free walking, out of the 18 gait parameters evaluated, we only identified significant differences in hip power generation during push-off (in C and TC groups) and in knee power absorption during weight acceptance (in TC and BC groups). There were no between-group differences in gait parameters while people with PAD were walking with claudication pain.Conclusions: Our data demonstrate that PAD affects the ischemic lower extremities in a diffuse manner irrespective of the location of claudication symptoms.Database Registration: ClinicalTrials.gov NCT01970332.(c) 2023 The Author(s). Published by Elsevier Masson SAS. This is an open access article under the CC BY-NC -ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Different levels of arterial occlusive disease (aortoiliac, femoropopliteal, multi-level disease) can produce claudication symptoms in different leg muscle groups (buttocks, thighs, calves) in patients with peripheral artery disease (PAD). We tested the hypothesis that different locations of occlusive disease uniquely affect the muscles of PAD legs and produce distinctive patterns in the way claudicating patients walk. Ninety-seven PAD patients and 35 healthy controls were recruited. PAD patients were categorized to aortoiliac, femoropopliteal and multi-level disease groups using computerized tomographic angiography. Subjects performed walking trials both pain-free and during claudication pain and joint kinematics, kinetics, and spatiotemporal parameters were calculated to evaluate the net contribution of the calf, thigh and buttock muscles. PAD patients with occlusive disease affecting different segments of the arterial tree (aortoiliac, femoropopliteal, multi-level disease) presented with symptoms affecting different muscle groups of the lower extremity (calves, thighs and buttocks alone or in combination). However, no significant biomechanical differences were found between PAD groups during the pain-free conditions with minimal differences between PAD groups in the claudicating state. All statistical differences in the pain-free condition occurred between healthy controls and one or more PAD groups. A discriminant analysis function was able to adequately predict if a subject was a control with over 70% accuracy, but the function was unable to differentiate between PAD groups. In-depth gait analyses of claudicating PAD patients indicate that different locations of arterial disease produce claudication symptoms that affect different muscle groups across the lower extremity but impact the function of the leg muscles in a diffuse manner generating similar walking impairments.

Background Individuals poststroke experience gait asymmetries that result in decreased community ambulation and a lower quality of life. A variety of studies have utilized split-belt treadmill training to investigate its effect on gait asymmetry, but many employ various methodologies that report differing results. Objective The purpose of this meta-analysis was to determine the effects of split-belt treadmill walking on step length symmetry in individuals poststroke both during and following training. Methods A comprehensive search of PubMed/MEDLINE, CINAHL, Web of Science, and Scopus was conducted to find peer-reviewed journal articles that included individuals poststroke that participated in a split-belt treadmill walking intervention. Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) was used to assess risk of bias. Pooled Hedge’s g with random effects models were used to estimate the effect of split-belt training on step length symmetry. Results Twenty-one studies were assessed and included in the systematic review with 11 of them included in the meta-analysis. Included studies had an average STROBE score of 16.2 ± 2.5. The pooled effects for step length asymmetry from baseline to late adaptation were not significant ( g = 0.060, P = .701). Large, significant effects were found at posttraining after a single session ( g = 1.04, P < .01), posttraining after multiple sessions ( g = −0.70, P = .01), and follow-up ( g = −0.718, P = .023). Conclusion Results indicate split-belt treadmill training with the shorter step length on the fast belt has the potential to improve step length symmetry in individuals poststroke when long-term training is implemented, but randomized controlled trials are needed to confirm the efficacy of split-belt treadmill training.

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. METHODS:A randomized, double-blind, crossover design was used. Nineteen pre-pubescent children (n = 10 boys, n = 9 girls, mean ± standard error, age = 9.84 ± 0.37-yrs) participated. Visits to the laboratory began with a 30-min measurement of resting metabolism followed by consumption of either an RDC or SDC drink. Postprandial resting metabolism was recorded for 60-min, immediately followed by 60-min of submaximal cycling exercise while metabolism was recorded, which was immediately followed by another 60-min recording of post-exercise metabolism. Total CHO and fat oxidation, endogenous and exogenous CHO oxidation, blood glucose, and insulin were assessed. RESULTS:Total CHO oxidation rate (g∙min-1) was greater after the RDC drink at 60 min (p = 0.032). Endogenous CHO oxidation rate (g∙min-1) was greater after the SDC drink at 15 min (p ≤ 0.010). Cumulative endogenous CHO oxidation (g) was greater after the SDC drink at 45 min (p = 0.009). Endogenous CHO oxidation accounted for a greater proportion of substrate oxidation after the first 60-min rest period (p = 0.028), while exogenous CHO oxidation accounted for a greater proportion of substrate oxidation for the RDC at all time points (p ≤ 0.019). CONCLUSIONS:The present study provides novel data suggesting that an SDC promotes greater endogenous substrate utilization in pre-pubertal children, which may have beneficial health impacts on energy intake and carbohydrate regulation/metabolism during growth and development. CLINICAL TRIALS REGISTRY NUMBER:NCT03185884, clinicaltrials.gov.

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 Res34(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. Cross-sectional anthropometric and performance data were obtained from 12 different high school American football recruiting combines between March 7, 2015, and January 9, 2016, across the United States. Subjects included a sample (n= 7,478) of high school-aged American football athletes in their junior (n= 3,779), sophomore (n= 2,514), and freshman (n= 1,185) classes. The database included combine date, school state, position, class, height, body mass (BM), 40-yard dash, pro-agility, 3-cone, vertical jump, broad jump, and power push-up. Each player self-classified their American football positions as defensive back, defensive end, defensive linemen, linebacker, offensive linemen, quarterback, running back, tight end (TE), or wide receiver. Test- and position-specific normative values were generated by aggregating data from freshman, sophomore, and junior classes. Mean differences were found among classes for all positions and all measurements (p <= 0.05), except for TE BM (p> 0.05). Greater differences for all variables were observed from freshman to sophomore classes than from sophomore to junior classes. These normative reference values may provide realistic comparisons and evaluations in performance for young American football players, parents, and coaches with collegiate football aspirations. High school strength and conditioning professionals should use these norms to set attainable goals and reward accomplishments for young football players.

•Resting metabolism and 13C abundance were measured in pre-pubescent children.•Foods provided effectively minimized 13C variation prior to metabolic testing.•30-g RDC resulted in a three-fold increase in cumulative exogenous CHO utilization.•Despite increases in exogenous oxidation, endogenous utilization was not suppressed.

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. Participants' data (n = 7,160) were analyzed for this study (mean height [Ht] ± SD = 178 ± 7 cm, mass [Bm] = 86 ± 19 kg). Data were obtained from 12 different high school American football recruiting combines hosted by Zybek Sports (Boulder, Colorado). Eight 2-way (9 × 3) mixed factorial analysis of variances {position (defensive back [DB], defensive end, defensive lineman, linebacker, offensive lineman [OL], quarterback, running back, tight end, and wide receiver [WR]) × grade (freshmen, sophomores, and juniors)} were used to test for differences among the mean test scores for each combine measure (Ht, Bm, 40-yard [40 yd] dash, proagility [PA] drill, L-cone [LC] drill, vertical jump [VJ], and broad jump [BJ]). There were position-related differences (p ≤ 0.05) for Ht, 40 yd dash, and BJ, within each grade level and for Bm, PA, LC, and VJ independent of grade level. Generally, the results showed that OL were the tallest, weighed the most, and exhibited the lowest performance scores among positions. Running backs were the shortest, whereas DBs and WRs weighed the least and exhibited the highest performance scores among positions. These results demonstrate the value of classifying high school-aged American football players according to their specific position rather than categorical groupings such as "line" vs. "skill" vs. "big skill" when evaluating anthropometric and athletic performance combine test results.

Abstract 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. The purposes of this study were to report test-retest reliability statistics and evaluate concurrent validity among combine performance tests in 6–15-year-old male athletes. Sixty-nine young male athletes (mean ± SD; age = 10.9 ± 2.1 years, height = 154.4 ± 13.6 cm, body mass = 46.8 ± 16.0 kg) were divided into 3 age groups: 6–9 years (n = 16), 10–11 years (n = 26), and 12–15 years (n = 27). Participants completed 2 attempts of the vertical jump (VJ), broad jump (BJ), pro-agility (PA), L-cone (LC) drill, and 10-, 20-, 40-yd dashes. The results indicated that the older age groups performed better on most performance assessments compared with the 6–9-year group (p ⩽ 0.05). The combine tests demonstrated consistently adequate reliability for all age groups, except for the 10-yd dash, which was deemed unreliable. Evidence of concurrent validity, and possible measurement redundancy were observed in the VJ vs. BJ, PA vs. LC, and 20 vs. 40 yd, but zero- and first-order partial correlations suggested that only the PA and LC were redundant, and the PA may be superior for this age group over the LC. Although the VJ and BJ provide independent performance information regarding lower-body power, questions regarding the redundancy of the 20 vs. 40 yd remain unanswered from a measurement perspective.

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. Cross-sectional performance data were obtained from 12 different high school American football recruiting combines between March 7, 2015, and January 9, 2016, across the United States. The sample included (n = 7,478) high school-aged American football athletes in their freshman (n = 1,185), sophomore (n = 2,514), and junior (n = 3,779) classes. Each player self-classified their American football positions as defensive back, defensive end, defensive linemen, linebacker, offensive linemen (OL), quarterback (QB), running back, tight end, or wide receiver. The results of the freshman, sophomore, and junior class were aggregated to generate test- and position-specific normative values. Mean differences were found among classes for all positions and all measurements (p <= 0.05) except for OL and QB PA split time (p > 0.05). Greater percent differences for all 3 variables were observed between freshman and sophomore years than between sophomore and junior years. These normative reference values will be useful for athletes, parents, coaches, and high school strength and conditioning professionals to set realistic goals for young American football 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. 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 ± SD; age = 10.8 ± 2.0 years) were tested twice over 5 days. Boys were separated by age as 6-9 years (n = 16), 10-11 years (n = 26), and 12-15 years (n = 26). The PPU test was performed on a force plate while rotating from the knees vs. the toes. Measurements were peak force (PF, N), peak rate of force development (pRFD, N·s), average power (AP, W), and peak power (PP, W). Intraclass correlation coefficients (ICC2,1), SEMs, coefficients of variation (CVs), and minimum detectable changes (MDCs) were calculated to quantify reliability and sensitivity. Peak force from the knees in 10-15-year-olds, PF from the toes in 12-15-year-olds, and pRFD from the knees and toes in 12-15-year-olds were comparably reliable (ICC ≥ 0.84). Neither power measurements (AP or PP) for any age group, nor any measurements (PF, pRFD, AP, or PP) for the 6-9-year-olds were comparably reliable (ICC ≤ 0.74). When considering the reliable variables, PF was greater in the 12-15-year-olds than in 10-11-year-olds (p ≤ 0.05). In addition, in 12-15-year-olds, PF and pRFD were greater from the knees than from the toes (p ≤ 0.05). For reasons largely attributable to growth and development, the PPU test may be a reliable (ICC ≥ 0.80) and sensitive (CV ≤ 19%) measure of upper-body strength (PF), whereas pRFD was also reliable (ICC ≥ 0.80), but less sensitive (CV = 30-38%) in 10-15-year-old male athletes.

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. The HT, BM, and BMI increased as grade increased among all positions. Offensive lineman and DL had the greatest HT, BM, and BMI (p ≤ 0.05). Obesity prevalence was greatest in OL and DL. When accounting for age-related increases in BMI, BM increased to a greater degree than HT. If HT is an indirect indicator of skeletal size, although BM is more influenced by soft tissue, then the age-related BMI increases in this study may be largely accounted for by soft-tissue changes rather than skeletal growth. Although obesity prevalence in OL (94.5%) and DL (78.4%) positions was greater than all other positions as determined from BMI, it is impossible to know the allocations of fat-free and fat mass-particularly in American football athletes. If obesity continues to be defined as an unhealthy accumulation of fat, then athletes who may have a greater relative proportion of lean soft tissue should not be classified as obese using BMI (BM ÷ HT). More sophisticated, reliable, and sensitive measure of body composition, such as skinfolds, may be more appropriate field measurements.

The power push-up (PPU) is an explosive upper-body test performed on a force plate and has recently replaced the bench press test in high school football combines such as the U.S. Army National Combine and Under Armour All-American Combine. PURPOSES: Compare the PPU test performed from the knees versus the toes across 3 age groups (6-9, 10-11, and 12-15 yr) of young male athletes and report the test-retest reliability. METHODS: Sixty-eight boys (mean±standard deviation (SD); height=154±14 cm; mass=47±16 kg) were tested twice over 5 days. The PPU was performed on a force plate from the knees and from the toes. Measurements included peak force (PF, N), peak rate of force development (pRFD, N·s-1), average power (AP, W), and peak power (PP, W). Two-way ANOVAs (position x age) were performed, while intraclass correlation coefficients (ICC2,1), standard errors of measurement (SEM), coefficients of variation (CV), and minimum detectable changes (MDC) were calculated. RESULTS: PF, pRFD, and PP were greater (p ≤ 0.05) from the knees for the 10-11 and 12-15 yr groups, whereas AP was greater (p ≤ 0.05) from the knees for all age groups. PF and pRFD were greater (p ≤ 0.05) in 12-15 yr than 6-9 and 10-11 yr from the knees and the toes. Table 1 shows the mean values and test-retest reliability metrics. CONCLUSIONS: PF, pRFD, AP, and PP were greater from the knees than the toes, and the oldest age group (12-15 yr) demonstrated the highest PF and pRFD values. However, the only consistently reliable measure was PF when the PPU test was performed from the knees in 10 to 15-year-olds; pRFD was also reliable from the knees in 12-15-year-olds. None of the measures from the youngest age group were reliable, and neither of the power measures (AP or PP) were reliable across all ages.Table: No title available.

INTRODUCTION: Limited data exist on the reliability and sensitivity of the 40-yard dash (40-yd) and vertical jump (VJ) tests in youth athletes, which are popular combine performance assessments. PURPOSE: To examine the test-retest reliability for the 40-yd and VJ in youth athletes. METHODS: Seventy-seven 5-15 year-old athletes (mean height ± SD = 153.0 cm ± 14.9; weight = 45.8 kg ± 16.3) volunteered for the performance assessments during two visits separated by 24-72 hours. Athletes were divided into three age groups (5 - 9, 10 - 11, and 12 - 15 years old). The 40-yd was assessed in seconds (s) with a digital timing gate, and the VJ was assessed in centimeters (cm) with a vertec, both performed on indoor field turf. Intra-class correlation coefficients (ICC) with corresponding 95% confidence intervals, standard errors of measurement (SEM), coefficients of variation (CV), and minimum detectable changes (MDC) were calculated from the repeated measures analysis of variance (ANOVA) from test 1 to test 2 for both assessments. RESULTS: There were systematic decreases in 40-yd times from test 1 to test 2 for the 12 - 15 year-old group, but there was no other detectable systematic variability for any other variable. The ICCs ranged from 0.78 to 0.96, which were greater than zero. MDCs (calculated from SEMs) for the 5 - 9, 10 - 11, and 12 - 15 age groups were 0.49, 0.70, and 0.38 s for the 40-yd, and 6.7, 4.3, and 13.7 cm for the VJ, respectively. CONCLUSIONS: Twelve to fifteen year olds may need a familiarization trial (i.e., test run) for the 40-yd. Based on the age of the athlete, 0.4 - 0.7 s and 4 - 14 cm changes in the 40-yd and VJ, respectively, may be necessary for individual youth athletes to consider their improvements real beyond the errors of the measurements.

PURPOSE: Examine the effects of 9 wks of speed and agility training (SAT) on combine test performance in 7 to 13-year-old male athletes. METHODS: Forty-six boys (7.6 to 13.4 years; height = 152.3 ± 9.9 cm, mass = 44.5 ± 12.1 kg) participated in this study by completing 3 testing sessions: combines 1 and 2 (C1 and C2) were separated by up to 4 days for familiarization and test-reliability, while combine 3 (C3) was performed 9 wks after C2. Combine measures included vertical jump (VJ, cm), broad jump (BJ, cm), pro-agility drill (PA, s), L-cone drill (LC, s), and 40-yd sprint (S40, s) with 10and 20-yd splits (S10 and S20, s). The SAT group (n = 23) participated in a 9-wk SAT camp with 1 session·wk -1 (1.5 hr·session -1 ). The control (CON) group (n = 23) was age-matched, did not perform the SAT, but maintained their regular sports activities. RESULTS: There was no difference in sports participation hours reported between the SAT and CON groups (p = 0.17). There were no group × time interactions (p ≥ 0.12), no main effects for group (p ≥ 0.28), but there were main effects for time for BJ and PA (p ≤ 0.01). There were systematic improvements in PA, LC, and S10 (p ≤ 0.01) from C1 to C2, but not VJ, BJ, S20 or S40 (p ≥ 0.06). Intraclass correlation coefficients (ICC3,1), coefficients of variation (CV, %), standard errors of measurement (SEM), and minimum detectable changes (MDC) were [test: ICC (CV, SEM, MDC)] VJ: 0.91 (8.6%, 3.4 cm, 9.5 cm); BJ: 0.89 (6.8%, 10.5 cm, 29.2 cm); PA: 0.89 (3.7%, 0.22 s, 0.61 s); LC: 0.84 (4.5%, 0.42 s, 1.18 s); S10: 0.68 (6.8%, 0.15 s, 0.42 s); S20: 0.91 (3.8%, 0.14 s, 0.40 s); S40: 0.72 (7.7%, 0.52 s, 1.44 s). Over the 9 wks, 1 boy exceeded the MDC for BJ and LC; 5 exceeded MDC for S10; and 3 exceeded MDC for S20. Seventeen boys exceeded the SEM for VJ; 16 exceeded the SEM for BJ; 11 exceeded the SEM for PA; 12 exceeded the SEM for LC; 15 exceeded the SEM for S10 and S20; 2 exceeded the SEM for S40. CONCLUSIONS: The SAT (1 session·wk -1 ; 9 wks) did not enhance combine performance beyond normal sports participation in young male athletes. Sensitivity, as evaluated by reliability and boys exceeding the MDC (and SEM) after a familiarization session and the 9-wk intervention period, was greatest for the VJ, BJ, PA, LC, S10, and S20 tests. Future studies aiming to examine combine performance enhancement training in youth athletes may consider using these tests.