Jones, Margaret T

Abstract Burke, AA, Saine, ND, King, EL, Fields, JB, Jagim, AR, Miller, AD, Green, BC, and Jones, MT. Longitudinal modeling of pitching workload and countermovement jump performance as determinants of fastball velocity and consistency in collegiate baseball pitchers. J Strength Cond Res XX(X): 000–000, 2026—Maintenance of four-seam fastball (FSFB) velocity across the baseball season is critical, yet the extent to which workload and neuromuscular status relate to velocity is unclear. Thus, aims of the current study were to assess the relationship between external pitching workload metrics and FSFB velocity; quantify within-season FSFB velocity; and examine how countermovement jump (CMJ) performance predicts FSFB velocity. Collegiate pitchers ( n = 8) completed weekly CMJ testing during a 15-week, 53-game season. Countermovement jump metrics included jump height (JH), reactive strength index–modified (RSImod), peak braking force, and peak propulsive force normalized to body mass. Workload variables (innings, total pitches, FSFB pitches) and FSFB velocity were evaluated via repeated measures correlation (RMCORR). A longitudinal heat map visualized velocity trends, and a hierarchical location–scale model assessed predictors of mean velocity and variance. Repeated measures correlation showed weak negative associations between FSFB velocity and innings ( r = −0.15, p = 0.11), total pitches ( r = −0.18, p = 0.05), and FSFB pitches ( r = −0.18, p = 0.05). Heat map analysis identified 3 distinct velocity clusters. Location model results indicated no predictors of mean velocity. The scale model showed JH ( γ = −0.060, p = 0.001) predicted reduced velocity variance, and RSImod ( γ = 3.800, p < 0.001) predicted increased variance. Findings suggest that velocity patterns varied across athletes, where greater workloads were negatively associated with FSFB pitch velocity. Further, CMJ performance related to velocity stability rather than mean velocity. Routine longitudinal monitoring and continued strength-power training are recommended to support FSFB velocity.

Abstract The purpose of the current study was to identify the influence of individual characteristics on differences in body fat percentage between air displacement plethysmography and dual-energy X-ray absorptiometry (change in body fat percentage) in 360 collegiate student-athletes. Body fat percentage was obtained from air displacement plethysmography and dual-energy X-ray absorptiometry. A 2 (sex)×3 (Brozek body fat percentage, Siri body fat percentage, and dual-energy x-ray absorptiometry body fat percentage) analysis of variance was used to evaluate the difference between the body fat percentages obtained from air displacement plethysmography and dual-energy x-ray absorptiometry in men and women. The agreement between air displacement plethysmography and dual-energy X-ray absorptiometry was evaluated via Bland–Altman plot and linear regression. Multiple linear regression was used to identify the influence of sex, race, height, and body mass on the change in body fat percentages. Dual-energy X-ray absorptiometry yielded greater body fat percentages in both men (4.8±2.8; p < 0.001) and women (2.2±2.9; p < 0.001) compared to air displacement plethysmography measurements. Proportional and systematic biases were observed between air displacement plethysmography and dual-energy X-ray absorptiometry. Race, height, and mass were significant predictors of the body fat percentage difference between air displacement plethysmography and dual-energy X-ray absorptiometry (R 2=0.445, p<0.001, and standard error of the estimate=2.527). The present study suggests that air displacement plethysmography underestimates body fat percentages when compared to dual-energy X-ray absorptiometry and this underestimation may not be the same for every athlete due to their individual characteristics.

Abstract Korpinen, M, Magee, M, Dulak-Sigler, C, Fields, JB, Jagim, AR, King, E, Burke, A, and Jones, MT. Seasonal changes in neuromuscular performance across a training year in women collegiate lacrosse athletes. J Strength Cond Res 39(11): 1186–1193, 2025—Body composition and athlete load management are vital to adequate training stimuli and to mitigate neuromuscular (NM) fatigue. Research is limited regarding NM performance (NMP) in women lacrosse athletes. Therefore, the purpose of this study was to investigate changes in NMP in women lacrosse athletes across a training year. Collegiate women lacrosse athletes ( n = 9, mean ± SD ; age = 19.1 ± 0.9 years, height = 168.4 ± 6.8 cm, body mass = 68.0 ± 8.1 kg) completed countermovement jump (CMJ) and isokinetic strength (IS) testing of dominant and nondominant legs 4 times throughout the season: preseason start, preseason end, in-season end, and off-season end to assess NMP. Measures included (a) CMJ output variables of reactive strength index modified (RSImod), jump height, relative values of braking force, peak power, peak propulsive force, impulse; (b) CMJ strategy variables of time-to-takeoff, eccentric duration, concentric duration, relative braking time, CMJ depth; and (c) IS relative peak torques of quadriceps and hamstrings musculature. Secondary measures including body composition variables of body mass, % body fat (%BF), and fat-free mass. Repeated measures ANOVA with Bonferroni post hoc analysis assessed changes in CMJ and IS parameters to determine patterns in NMP ( p < 0.05). Changes observed from preseason start to offseason end included increased CMJ depth ( p = 0.019), relative braking time ( p = 0.009), and %BF ( p = 0.01). The IS variables increased throughout the training year, except for a decrease during preseason, perhaps indicative of overreaching. Negative changes in alternative CMJ variables and body composition reduced NMP, which highlights the importance of off-season program design and implementation to elicit desired training adaptations.

Abstract Magee, MK, Fields, JB, Jagim, A, Lockard, B, Miller, A, Stroiney, D, and Jones, MT. Estimation of whole-body bone mineral density through air displacement plethysmography in a large sample of elite athletes. J Strength Cond Res 39(4): 427–432, 2025—Dual-energy x-ray absorptiometry (DXA) is used to determine bone mineral density (BMD) and body composition. Regulations and cost may limit DXA's utility in some athletic settings. Air displacement plethysmography (ADP), while able to measure body composition, does not measure BMD. The purpose was to evaluate the influence of body composition parameters obtained from ADP on BMD. Collegiate athletes (males, n = 153; females, n = 208) underwent ADP and DXA assessments. For ADP testing, the Brozek equation was used to estimate body fat percent (BF%) and fat-free mass (FFM) from body density. Dual-energy x-ray absorptiometry tests were completed to obtain BMD using the whole-body scan mode. Stepwise regression was conducted using age, body mass, height, sex, race, FFM (ADP), BF% (ADP), and sport type as independent variables. Total BMD (DXA) was the dependent variable. Accuracy and precision of the final equation were evaluated through Bland–Altman and linear regression. The final regression equation yielded an R 2 of 0.691 with race, mass, BF%, age, and sport type as significant predictors ( p < 0.05) of BMD. Bland–Altman and linear regression showed systematic {95% confidence interval [CI] (−0.619 to −0.360)} and proportional bias (95% CI [0.173–0.374]). Although an ADP-derived regression equation may not provide a precise prediction of BMD, it may be useful to establish risk for low BMD if DXA is unavailable. Dual-energy x-ray absorptiometry may not be feasible for some athletic programs; therefore, an estimation equation for BMD derived from ADP values is advantageous for practitioners. This equation may assist in screening athletes for risk of low BMD.

The strength of the shoulder musculature involved with internal rotation and arm extension plays an important role in the overhead throwing motion for baseball athletes, both for throwing-related performance and injury risk. The maintenance of shoulder strength is a high priority for baseball athletes throughout a season; however, little is known in regards to the expected changes in strength throughout a season. To examine pre-post changes in shoulder strength, lower body power, and body composition among collegiate baseball players after the completion of a summer baseball league season. Amateur baseball players (n = 12; age: 20.9 ± 1.0 years.; height: 181.6 ± 5.6 cm; body mass: 86.4 ± 11.1 kg; BMI: 26.0 ± 2.6 kg/m2) participated in the current study. Pre- and post-competitive season, the participants completed shoulder strength assessments and body composition and countermovement vertical jump (CMJ) tests. An upper-body isometric test (athletic shoulder [ASH] test) was used to evaluate shoulder strength for each arm. Each subject completed maximal isometric contractions for both the throwing and non-throwing arms at four separate angles of abduction (180°, ‘I’; 135°, ‘Y’; 90°, ‘T’; and −180°, ‘A’) while lying in a prone position. For shoulder strength, the primary dependent variable of interest was a composite measure that represented the average of the forces produced across all four positions of the ASH test (I, Y, T, A). For the ASH test composite measure, there was a trend toward a significant arm-by-time interaction effect (p = 0.08), as shoulder strength decreased by 9.03% for the throwing arm (ES = 0.72; 95% CI = [−0.27, −0.01]), compared to only 2.03% for the non-throwing arm (ES = 0.15; 95% CI = [−0.16, 0.09]), over the course of the season. The main effects of time (p = 0.16) and arm (p = 0.58) were not significant for the ASH test composite measure. There was no relationship between lower body power and throwing arm strength at baseline (r = 0.20, p = 0.56), and only a non-significant weak relationship at post-test (r = 0.28, p = 0.41). Throughout a season, baseball players may experience reductions in shoulder strength of the throwing arm with minimal changes in shoulder strength in the non-throwing arm.

Abstract Brown, FSA, Fields, JB, Jagim, AR, Baker, RE, and Jones, MT. Analysis of in-season external load and sport performance in women’s collegiate basketball. J Strength Cond Res 38(2): 318–324, 2024—Quantifying and monitoring athlete workload throughout a competitive season is a means to manage player readiness. Therefore, the purpose of the current study was to quantify practice and game external loads and to assess the relationship between such loads and basketball-specific performance metrics across a women's collegiate basketball season. Thirteen National Collegiate Athletic Association Division I women basketball athletes (age 20.08 ± 1.55 years) wore Global Positioning Systems sensors equipped with triaxial accelerometers for 29 games and 66 practices during the 2019–20 season. A multivariate analysis of variance was used to assess differences in external load between high- and low-minute players and across quarters within games ( p < 0.05). Bivariate Pearson correlation coefficients were run to determine relationships between external loads and metrics of basketball performance. Findings indicated that high- and low-minute athletes experienced different loads during games and practices ( p < 0.001). External loads differed by quarter, such that player load (PL) was highest in Q4 ( p = 0.007), PL·min −1 was highest in Q1 and lowest in Q4 ( p < 0.001), and explosive ratio (i.e., ratio of PL and explosive efforts) was lowest in Q3 ( p = 0.45). Relationships existed between PL·min −1 and field goals ( r = 0.41; p = 0.02) and between the explosive ratio and free throws ( r = 0.377 p = 0.04). These results can be used to inform design of training sessions with the intent to prepare athletes for the demands of the competitive season. It is recommended that future research continue to explore the relationship of sport-specific performance metrics and athlete external load.

Abstract Magee, MK, Fields, JB, Jagim, AR, and Jones, MT. Fat-free mass index in a large sample of National Collegiate Athletic Association men and women athletes from a variety of sports. J Strength Cond Res 38(2): 311–317, 2024—Fat-free mass index (FFMI) can be used to categorize fat-free mass (FFM) relative to height. Normative values have been established in a variety of sports, as has suggested lower and upper thresholds of FFMI. However, FFMI has not been reported in a large sample of athletes, representing both sexes and multiple sport types. The purpose of this study was to evaluate differences in FFMI and establish normative values across a large sample of collegiate sports. A total of 1,961 athletes (men: n = 596, 10 sports; women: n = 1,365, 8 sports) participated. Height and mass were measured using a stadiometer and calibrated digital scale, respectively. Fat-free mass was assessed with air displacement plethysmography and used to calculate FFMI. Kruskal-Wallis test and one-way analysis of variance evaluated differences in FFMI in women's and men's sports, respectively. When collapsed across sport type and stratified by sex, men had a higher FFMI (21.5 ± 1.9 kg·m −2 vs. 17.9 ± 1.8 kg·m −2 ; p < 0.001). Differences occurred in FFMI across sport. In women, basketball athletes had the highest FFMI (18.9 kg·m −2 ) and highest 99th percentile for FFMI, whereas rowers had the lowest (16.9 kg·m −2 ). In men, throwers had the highest FFMI (25.7 kg·m −2 ) and highest 99th percentile, whereas volleyball athletes had the lowest (19.9 kg·m −2 ). Differences in FFMI may be attributable to dietary habits and physiological demands of respective sports. These results can provide information relative to differences in FFMI values across sports. In addition, sport-specific normative values can be used as benchmarks and targets for training, nutrition, and goal setting.

Abstract Fields, JB, Kuhlman, NM, Jagim, AR, Dulak-Sigler, C, and Jones, MT. Analysis of accumulated workloads and performance testing across a collegiate women's lacrosse season. J Strength Cond Res 37(11): 2213–2221, 2023—Monitoring accumulated workloads, acute:chronic workload ratios (ACWR), and training monotony (TM) are practical methods for monitoring athlete physical stress. Performance testing provides useful information about the changing nature of physical abilities. Therefore, the purpose was to examine differences in accumulated workloads based on session type, explore seasonal trends in ACWR and TM, and assess changes in performance assessments in collegiate women's lacrosse athletes. Athletes, who were identified as starters ( n = 12), wore positional monitoring technology during training sessions ( n = 61) and games ( n = 17) and completed preseason and postseason assessments of speed, agility, power (jump tests), strength, aerobic capacity, and body composition. Separate 1-way analyses of variance were used to determine differences in accumulated workloads for session type and differences in performance assessments from preseason to postseason ( p < 0.05). When compared with games, practice sessions elicited greater ( p < 0.001) accumulated total distance, player load, repeated high-intensity efforts, accelerations, change of direction, explosive efforts, high-speed efforts ( p = 0.002), and high-speed distance ( p = 0.002). Throughout the season, ACWR and TM ranged from 0.16 to 1.40 AU and 0.68–1.69 AU, respectively. The 40-yd sprint ( p < 0.001) and pro-agility ( p < 0.001) improved from preseason to postseason, whereas no changes in aerobic capacity, lower-body power, or strength were observed ( p > 0.05). The monitoring of accumulated loads, ACWR and TM, and performance tests revealed novel information about the seasonal demands of collegiate women's lacrosse. Women lacrosse players are able to improve speed and agility throughout the season, while maintaining strength, power, and endurance, with minimal reductions in fat-free mass.

Abstract Askow, AT, Jennings, W, Jagim, AR, Fields, JB, Beaudoin, RG, Sanchez, GM, Weeks, JE, Oliver, JM, and Jones, MT. Athlete external load measures across a competitive season in high school basketball. J Strength Cond Res 37(11): 2206–2212, 2023—The purpose of this retrospective analysis was to quantify in-season external load and to determine if relationships existed between load metrics and basketball performance. Eleven male high school varsity basketball athletes (n = 11; mass 80.5 ± 9.6 kg, height 190.2 ± 9.4 cm, age 17.6 ± 0.7 years) were monitored across a season. PlayerLoad (PL), PL per minute (PL·min −1 ), total jumps, and explosive movements (EMs) were quantified using a commercially available local positioning unit. Basketball-specific performance metrics, including points scored, points allowed, point differentials, and shooting percentages for each quarter and game, were compiled. Data were analyzed using repeated-measure analysis of variance to evaluate differences in load by starting status, session type, game outcome, and game type. Pearson's correlation coefficients were used to assess relationships between load metrics and basketball performance. Statistical significance was set at p < 0.05. The mean values across 23 games for PL, PL·min −1 , total jumps, and EMs were 457 ± 104 AU, 10.9 ± 1.6 AU, 42.6 ± 9.6, and 46.7 ± 7.2, respectively. Relationships were observed ( p < 0.05) between PL and points scored ( r = 0.38) and free throw percentage ( r = 0.21). Further relationships were observed between PL·min −1 and free throw shooting percentage ( r = −0.27), and between points scored and total jumps ( r = 0.28), and EMs ( r = 0.26). Notable differences in game demands were observed for playing status. Meaningful differences in measures of external load were observed between each quarter of play, with the highest measures evident in quarters 1 and 3. Guards and forwards experienced minimal differences in external load during gameplay, and game outcome did not result in differences. Higher point totals corresponded with higher PL, total jumps, and EM.