Luedke, Joel A

Abstract VanZile, AW, Jones, DD, McHugh, LJ, Clickovich, GL, Morales, MA, Reimschisel, RK, Widenhoefer, TL, Baughman, JT, Urquidi, MD, Conner, DJ, Dobbs, WC, Jagim, AR, Luedke, JA, and Almonroeder, TG. Examining countermovement jump performance and dynamic balance among male high school athletes with varying levels of sports specialization. J Strength Cond Res 39(11): 1163–1168, 2025—Specializing at a young age may limit an athlete's motor development, since focusing on a single sport potentially exposes athletes to less variety of movements and neuromuscular demands. However, there are few studies examining the association between sport specialization and movement performance/control. The purpose of this study was to compare countermovement jump performance and dynamic balance among high school athletes of varying levels of sports specialization. 110 male high school athletes completed countermovement jump testing and the Y-Balance Test (YBT). Ground reaction forces were recorded during countermovement jumps and used to derive peak force, peak velocity, peak power, jump height, and the modified reactive strength index. Y-Balance Test composite scores were calculated to assess dynamic balance across multiple directions, for the dominant and non-dominant limbs. Athletes were grouped into high ( n = 46), moderate ( n = 39), and low ( n = 25) specialization groups based on their sport participation habits. There were no between-group differences for any of the countermovement jump metrics ( p > 0.05). For the YBT composite scores, there was not a group-by-limb interaction effect ( p = 0.28); however, there was a main effect of group ( p = 0.03). Post hoc tests indicated that the high specialization group exhibited lower YBT composite scores compared to the moderate specialization group ( p = 0.01) and a trend toward lower scores compared to the low specialization group ( p = 0.05). In general, highly specialized male athletes exhibited poorer dynamic balance compared to less specialized athletes.

Abstract Dobbs, WC, Almonroeder, TG, Carpenter, M, Schmitt, RE, Jacobson, AK, Luedke, JA, Roberts, BM, and Jagim, AR. Relationships between the Army Combat Fitness Test scoring structure and laboratory measurements of physical fitness in reserve officer training corps cadets. J Strength Cond Res 39(7): 798–808, 2025—The Army Combat Fitness Test (ACFT) assesses aerobic and anaerobic fitness capabilities in the U.S. Army. The aim of this study was to evaluate the association between raw and composite ACFT scores and laboratory-based measurements of fitness. Nineteen Reserve Officers' Training Corp cadets performed a battery of laboratory-based fitness testing. Tests included a movement screening (Fusionetics), countermovement jumps, and maximal isometric mid-thigh pulls on portable force plates to determine power and strength. A Wingate test involving maximal cycling for 30 seconds was used to determine peak and mean power. On a separate day, cadets completed body composition and a graded exercise test on a motorized treadmill to determine peak oxygen uptake (V̇ o 2 peak). Pearson correlations and partial corrections with 2000 bootstraps were used to compare ACFT scores (raw, composite, gender-neutral composite, and z -scores) with laboratory results. Significant associations were identified as 95% confidence intervals, not including zero. The results indicated that V̇ o 2 peak ( r = 0.61, [0.08–0.84]), body fat percentage ( r = −0.4, [−0.72 to −0.06]), and relative peak power ( r = 0.38, [0.02–0.68]) were associated with the total ACFT composite score when partialled by sex. All laboratory tests, except the movement screening, showed meaningful associations with total ACFT z -scores and gender-neutral ACFT scores ( r > 0.54). However, most relationships were eliminated when partialled out by sex, which may be due to a low sample size of women. This suggests the current scoring structure utilized for men is representative of aerobic and anaerobic fitness parameters and may be able to discriminate performance levels.

Abstract Witte, BC, Schouten, TC, Westphal, JA, VanZile, AW, Jones, DD, Widenhoefer, TL, Dobbs, WC, Jagim, AR, Luedke, JA, and Almonroeder, TG. The modified reactive strength index is a valid measure of lower-body explosiveness in male and female high school athletes. J Strength Cond Res 38(8): 1428–1432, 2024—The modified reactive strength index (mRSI) is a commonly used metric to quantify lower-body explosiveness during countermovement jump (CMJ) performance. However, few studies have attempted to examine its validity as a measure of explosiveness, particularly among high school athletes. The purpose of this study was to examine the validity of the mRSI as a measure of lower-body explosiveness among a relatively large sample of male and female high school athletes from various sports. As part of this study, male ( n = 132) and female ( n = 43) high school athletes performed CMJs, while ground reaction forces were recorded using a force platform. The vertical ground reaction force data collected during the CMJs were used to derive the following variables: peak force (PF), peak power, time to PF, time to take-off, peak rate of force development, and the mRSI. Principal component analysis was applied and reduced these variables into 2 components related to “force” and “speed.” The mRSI loaded on both the force (loading = 0.82) and speed (loading = −0.46) components, indicating that it incorporates elements of both force and speed, although it loaded more strongly on the force component than the speed component. The observed pattern of cross-loading suggests that the mRSI is generally a valid measure of lower-body explosiveness for male and female high school athletes.

Firefighters often complete air management courses (AMC) to assess the ability to tolerate personal protective equipment, appropriately manage the breathing system and assess occupational performance. Little information is known relative to the physiological demands of AMCs, nor how to assess work efficiency in order to characterize occupational performance and evaluate progress. Purpose: To assess the physiological demands of an AMC and examine differences across BMI categories. A secondary aim was to develop an equation to assess work efficiency in firefighters. Methods: Fifty-seven firefighters (Women, n = 4; age: 37.2 ± 8.4 yr.; height: 182.0 ± 6.9 cm; body mass: 90.8 ± 13.1 kg; BMI: 27.8 ± 3.6 kg·m−2) completed an AMC per routine evaluation while wearing a department issued self-contained breathing apparatus and full protective gear. Course completion time, starting pounds per square inch (PSI) on the air cylinder, changes in PSI, and distance traveled were recorded. All firefighters were equipped with a wearable sensor integrated with a triaxial accelerometer and telemetry to assess movement kinematics, heart rate, energy expenditure, and training impulse. The AMC consisted of an initial section involving a hose line advance, rescue (body drag), stair climb, ladder raise, and forcible entry. This section was followed by a repeating loop, which consisted of a stair climb, search, hoist, and recovery walk. Firefighters repeated the course loop until the self-contained breathing apparatus air supply pressure reached 200 PSI, at which time they were instructed to lay down until the PSI reached zero. Results: Average completion time was 22.8 ± 1.4 min, with a mean distance of 1.4 ± 0.3 km and an average velocity of 2.4 ± 1.2 m·s−1. Throughout the AMC, the mean heart rate was 158.7 ± 11.5 bpm equating to 86.8 ± 6.3% of the age-predicted max heart rate and a training impulse of 55 ± 3 AU. Mean energy expenditure was 464 ± 86 kcals and work efficiency was 49.8 ± 14.9 km·PSI−1·s. Regression analysis determined that fat-free mass index (R2 = 0.315; β = −5.069), body fat percentage (R2 = 0.139; β = −0.853), fat-free mass (R2 = 0.176; β = −0.744), weight (R2 = 0.329; β = −0.681), and age (R2 = 0.096; β = −0.571) were significant predictors of work efficiency. Conclusions: The AMC is a highly aerobic task with near-maximal heart rates reached throughout the course. Smaller and leaner individuals achieved a higher degree of work efficiency during the AMC.

Research quantifying the unique workload demands of starters and reserves in training and match settings throughout a season in collegiate soccer is limited. Purpose: The purpose of the current study is to compare accumulated workloads between starters and reserves in collegiate soccer. Methods: Twenty-two NCAA Division III female soccer athletes (height: 1.67 ± 0.05 m; body mass: 65.42 ± 6.33 kg; fat-free mass: 48.99 ± 3.81 kg; body fat %: 25.22 ± 4.78%) were equipped with wearable global positioning systems with on-board inertial sensors, which assessed a proprietary training load metric and distance covered for each practice and 22 matches throughout an entire season. Nine players were classified as starters (S), defined as those playing >50% of playing time throughout the entire season. The remaining 17 were reserves (R). Goalkeepers were excluded. A one-way ANOVA was used to determine the extent of differences in accumulated training load throughout the season by player status. Results: Accumulated training load and total distance covered for starters were greater than reserves ((S: 9431 ± 1471 vs. R: 6310 ± 2263 AU; p < 0.001) and (S: 401.7 ± 31.9 vs. R: 272.9 ± 51.4 km; p < 0.001), respectively) throughout the season. Conclusions: Starters covered a much greater distance throughout the season, resulting in almost double the training load compared to reserves. It is unknown if the high workloads experienced by starters or the low workloads of the reserves is more problematic. Managing player workloads in soccer may require attention to address potential imbalances that emerge between starters and reserves throughout a season.