Jagim, Andrew R.

Purpose: The purpose of the current study was to cross-validate previously developed RMR prediction equations using laboratory measurements of RMR as a criterion. Methods: National Collegiate Athletic Association (NCAA) Division I (n = 60) and III (n = 113) male wrestlers participated in the current study (n = 173; Age: 19.6 ± 1.5 yrs.; Height: 176.3 ± 6.3 cm; Weight: 76.6 ± 10.9 kg; Body Fat: 11.4 ± 3.0%). Indirect calorimetry was used to measure RMR and Skinfold thickness was used to estimate body fat percentage (BF%) during the preseason period under standardized dress (underwear only), fasting, and resting conditions. Results: Mean measured RMR was 2102±341 kcal·d −1 . All body mass-based RMR prediction equations significantly underestimated the measured RMR, with the exception of the Jagim and Schofield equations. The Tinsley fat-free mass (FFM) equation and the Cunningham equation had the lowest constant error (CE) values when compared to measured RMR (mean bias ± standard error: 80 ± 20 kcal and 126 ± 20 kcal·d −1 , respectively). Linear regression indicated the Tinsley FFM (R 2 = 0.422, RMSE = 279 kcals, %RMSE = 13.3%), and Cunningham FFM equations had the closest agreement to measured RMR (R 2 = 0.422, RMSE = 301 kcals, %RMSE = 14.3%), along with the Jagim equation for a body mass-based prediction equation (R 2 = 0.377, RMSE = 338 kcals, %RMSE = 16.1%). The standard error of the estimate (SEE) ranged from 260 to 272 kcal·day −1 across equations. Coefficients of determination (R 2 ) ranged from 37% to 42%. The new body mass and FFM-based equations exhibited good agreement based on the CE (26 and -13 kcal·day −1 ), RMSE (274 and 252 kcal·day −1 ), respectively. Conclusions: The newly developed equations demonstrated mean bias <2% of measured RMR.

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 This review examines physiological limits, longitudinal projections, and best practices for muscle hypertrophy with a focus on bodybuilding and physique sport. Recurring body composition assessments using multicompartment models are recommended for monitoring short-term fat-free mass (FFM) changes and long-term muscular development. Normative data indicate that drug-free male athletes typically gain roughly 1.4 kg of FFM over 12 weeks of resistance training, with an interquartile range of 1–2 kg. A practical upper limit for FFM index in drug-free male athletes is approximately 28.5, although higher values have been observed in the context of elevated adiposity or anabolic androgenic steroid use. Female athletes tend to have roughly 70% less FFM at baseline but make proportionally similar FFM gains in response to resistance training. The present review models plausible short-term and long-term growth trajectories for both male and female lifters. Training practices that optimize hypertrophy include moderate loads (6–12 repetition maximum), training near muscular failure, and sufficient weekly volume (12–30 fractional sets per muscle group). Nutritional factors include maintaining modest caloric surpluses (0.1–0.25% body weight gain weekly), adequate protein intake (1.6–2.2 g/kg/d), sufficient carbohydrate intake (≥3 g/kg/d), and moderate fat intake (0.5–1.5 g/kg/d). Creatine and protein supplementation provide established hypertrophic benefits, while evidence for other supplements remains inconclusive.

The primary aim of this study was to examine pitching performance metrics before and after ulnar collateral ligament reconstruction (UCLR) among Major League Baseball (MLB) starting and relief pitchers. The following information was extracted from the “Tommy John Surgery List” database regarding UCLR surgeries among MLB pitchers: UCLR date, pitcher type (starting pitcher, relief pitcher), and age at time of UCLR. Pitching performance metrics were extracted from the Baseball Savant online platform for the two seasons immediately prior to UCLR (pre) and the two seasons immediately following returning to pitching after UCLR (post). Fifty-nine pitchers were included in this study (29 starting pitchers, 30 relief pitchers). The outcome measures included the number of pitches thrown, earned run average (ERA), walks plus hits per inning pitched (WHIP), strikeout percentage, whiff percentage, walk percentage, batting average against, ground ball percentage, and fastball velocity. There was a pitcher type-by-time interaction effect for ERA (p = 0.01; η2 = 0.12) and WHIP (p = 0.01; η2 = 0.12). Starting pitcher ERA increased from 3.68 to 4.40 from pre- to post-surgery, while relief pitcher ERA decreased from 4.47 to 3.90. In addition, starting pitcher WHIP increased from 1.22 to 1.29 from pre- to post-surgery, while relief pitcher WHIP decreased from 1.38 to 1.28. There was a main effect of time for pitches thrown (p = 0.04; η2 = 0.07). Significant differences between starting and relief pitchers were observed for changes in ERA and WHIP following UCLR, whereas no pitcher type-by-time interactions were observed for the remaining performance metrics. Both starting and relief pitchers threw fewer pitches following UCLR, while fastball velocity and other key pitching performance metrics remained largely unchanged.

Abstract Horlock, CF, Allen, LE, Jagim, AR, Jones, MT, and Fields, JB. In-season assessment of dietary intake and match demands of men’s collegiate Rugby Sevens players. J Strength Cond Res XX(X): 000–000, 2026—Limited research has examined the external workload demands and dietary intake of collegiate men's Rugby Sevens players. Therefore, the purpose of this study was to (a) quantify match demands in Division 1-AA collegiate Rugby Sevens across a competitive season, and (b) assess players' dietary intake relative to sport-specific nutrition guidelines. Division 1-AA men's collegiate Rugby Sevens players ( n = 13; age: mass: 87 ± 14 kg; body fat %: 20 ± 4%) wore a global positional system device during all matches ( n = 17). External load metrics were total distance (TD) (m), sprint distance (>20.1 km·h −1 ), high-intensity distance (>18.1–20.0 km·h −1 ), meters per minute (m·min −1 ), acceleration efforts (#), deceleration efforts (#), sprint efforts (#), high-speed efforts (#), player load (PL) (arbitrary unit [AU]), PL per minute (AU/min), and estimated energy expenditure (EE) (kcal). Dietary intake was assessed at the start of the season using a 4-day food log. Linear mixed models examined changes in workload parameters across tournament matches. Spearman's rank correlation and linear regression assessed relationships and predictability of EE and external workloads. One-samples t test compared dietary intake relative to established guidelines ( p ≤ 0.05). No significant differences in workload metrics were observed across individual matches. Total distance ( r = 0.968, p < 0.001), m·min −1 ( r = 0.973, p < 0.001), PL ( r = 0.912, p < 0.001), and PL/min ( r = 0.855, p < 0.001) had the strongest correlations with EE. Players significantly underconsumed calories ( p = 0.028) and carbohydrates ( p < 0.01). Monitoring external workloads and assessing dietary intake can provide coaches with strategies to optimize sports performance and nutrition support to prepare players for competition demands.

Introduction Female distance runners are at elevated risk for impaired bone remodeling due to high mechanical loading, potential low energy availability, and sustained inflammatory stress. Collagen peptide (CP) supplementation has been proposed as a nutritional strategy to support type I collagen synthesis and modulate osteoimmune signaling; however, evidence in premenopausal endurance athletes is limited. This pilot randomized, double-blind, placebo-controlled trial examined the effects of four weeks of high-dose CP supplementation on markers of bone metabolism and inflammatory activity in endurance-trained premenopausal women. Methods Twenty-two participants (18–35 years; ≥35 miles/week [&gt;56km/week]) were randomized to CP (INT; 20 g/day) or isocaloric maltodextrin (CON). Pre- and post-intervention assessments, conducted in the early follicular phase, included serum procollagen type I N-terminal propeptide (P1NP), plasma C-terminal telopeptide of type I collagen (CTX-1), serum soluble receptor activator of nuclear factor-κB ligand (sRANKL), osteoprotegerin (OPG), the sRANKL/OPG ratio, and interleukin-6 (IL-6). Repeated-measures ANCOVAs were performed, adjusting for accumulated running distance and vitamin D status. Results A significant group × time interaction was observed for P1NP ( p = 0.04), with increases in INT and no change in CON. No significant interaction was observed for CTX-1 ( p = 0.13). Significant interactions were also observed for sRANKL ( p = 0.046) and IL-6 ( p = 0.03). No significant interaction effects were detected for sRANKL, OPG, or the sRANKL/OPG ratio. Discussion Short-term CP supplementation increased a marker of bone formation, altered osteoclast-related signaling, and reduced IL-6 in endurance-trained premenopausal women. These findings support the potential for CP-mediated modulation of bone turnover and inflammatory activity and warrant further investigation in larger, adequately powered trials incorporating structural bone outcomes.

Weight loss and thermogenic dietary supplements often claim to promote weight loss by increasing metabolic activity. This study characterized the identity and quantity of common supplement ingredients. Commercially available products (n=98) whose name, label, or packaging referenced promotion of thermogenesis or weight loss were identified at retail outlets or web search. Product ingredients were divided into 6 possible categories of ingredient quantity based on packaging. Extracts included raw plant ingredients, plant extracts, etc. Small molecule isolates included caffeine, melatonin, etc. The remaining 4 ingredient categories were lipids, minerals, vitamins, and amino acids. Product suggested serving size was 13±16 grams (40±71 Cal). Green tea (521±1334 mg), cayenne (57±46 mg) and black pepper (5±2 mg) extracts were the most common, with 22 ingredients of 137 extracts being quantified 3 or more times. Caffeine (181±59 mg), acetyl-L-carnitine (595±368 mg) and L-carnitine (510±345 mg) were the most common small molecule isolates, with 11 of 49 total ingredients quantified in at least 3 products. There were 18 different lipid or fatty acid ingredients with only linoleic (740±718 mg) and lipoic (250±235 mg) acids being quantified in at least 3 products. Chromium (268±282 µg), calcium (156±110 mg), and iodine (145±85 mg) were the most common minerals, with 10 of 14 minerals quantified in at least 3 products. Cobalamin (49±78 µg), pyridoxine (8±9 mg) and folate (391±252 mcg) were the 3 most common vitamins, with 5 of 13 vitamins quantified in at least 3 products. Alanine (2133±924 mg), tryptophan (60±40 mg) and tyrosine (250±229 mg) were the most common amino acids, with 3 of 9 amino acids quantified in at least 3 products. Ingredients were indicated as “present” but not quantified 541 times across the 98 products. Proprietary formulas and vaguely worded ingredients were listed in 44 of the 98 products. The 98 thermogenic and weight loss products contained a tremendous variety of ingredients, although only 53 of the 240 different ingredients were present in 3 or more products. Variable ingredient content and quantity, complicate blanket claims about function, efficacy, or safety. Future evaluations of ingredient contents should determine if specific amounts confer discernable benefits. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Objective: To evaluate the current literature on the role of collagen peptide supplementation in bone health, focusing on changes in bone turnover markers (BTMs) and bone mineral density (BMD). Data Sources: A search was conducted following PRISMA guidelines in the databases Academic Search Premier, APA PsychInfo, CINAHL Plus, GreenFILE, MEDLINE, and SPORTDiscus. Keywords included “collagen supplementation,” “bone turnover,” and “bone structure.” Studies published between January 2000 and March 2024 were included if they involved human subjects, oral collagen supplementation, and skeletal-related outcomes (BTMs or BMD). Risk of bias was assessed using the modified Physiotherapy Evidence Database (PEDro) scale. Main Results: Fifteen studies met the inclusion criteria. Collagen supplementation was associated with improvements in BTMs such as procollagen type I N-terminal propeptide and C-terminal telopeptide of type I collagen, as well as increases in BMD at whole body, femoral neck, and lumbar spine sites, particularly in postmenopausal women. However, neutral findings and substantial heterogeneity in study design, population characteristics, and dosing protocols were also observed. Conclusions: Collagen supplementation shows promise for supporting bone health, particularly in postmenopausal women, but the evidence remains inconsistent. Future research should address these gaps by focusing on premenopausal populations, standardizing dosing protocols, and exploring broader orthopedic applications, such as reducing stress fractures and enhancing recovery from musculoskeletal injuries.

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.