Journal of Strength and Conditioning Research最新文献

Abstract: Faricier, R, Fleitas-Paniagua, PR, Iannetta, D, Millet, GY, Keir, DA, and Murias, JM. Time spent near maximal oxygen uptake during exercise at different regions of the severe-intensity domain. J Strength Cond Res XX(X): 000-000, 2024-This study applied the critical power (CP) model and several bouts of constant-power exercise within different regions of the severe-intensity domain to determine whether there exists an optimal intensity to maximize time spent near V̇o2peak. Subjects visited the laboratory 9 times. After a ramp-incremental test to determine V̇o2peak and peak power output (POpeak), 9 active individuals (5 females) performed 4 constant-power bouts to task failure between 65 and 100%POpeak to estimate CP and total finite work above CP (W'). Subjects then completed 4 additional exhaustive trials predicted to result in task failure in ∼3, 6, 9, and 12 minutes. Time spent at V̇o2peak was calculated as the duration at which V̇o2 ≥ 95% of the trial-specific V̇o2peak. The level of significance set for the study was p < 0.05. Mean CP and W' were 201 ± 48 W and 17.6 ± 8.4 kJ, respectively. For each bout, time to task failure was 2.7 ± 0.5, 6.3 ± 0.6, 9.5 ± 1.2, and 13.1 ± 3.1 minutes for the 3-, 6-, 9-, and 12-minute conditions. Time spent at V̇o2peak during the 3-minute trial (45 ± 22 seconds) was shorter than during the 9-minute (204 ± 104 seconds; p = 0.002) and 12-minute trials (260 ± 155 seconds; p < 0.001). The 6-minute trial (117 ± 46 seconds) had shorter (p = 0.005) time spent at V̇o2peak compared with the 12-minute trial. At least when performing single bouts of exercise, intensities closer to CP (i.e., those sustainable for ∼9 minutes or longer) seem preferable compared with POs in the upper regions of the severe-intensity domain to maximize time at V̇o2peak.

Abstract: Gdovin, JR, Hogan, B, and Williams, CC. Limiting access to resistance training equipment during the off-season: the impact on collegiate pitching metrics. J Strength Cond Res XX(X): 000-000, 2024-Resistance training has been shown to improve overhead throwing velocity, but it is unknown as to how limiting access to a strength and conditioning facility affects a baseball pitcher's readiness for the spring season. Therefore, the purpose of this study was to examine the influence of an individualized pitching program on pitching metrics during an 8-week fall season in collegiate baseball pitchers without a simultaneous structured strength training program. Twelve National Collegiate Athletic Association Division-I baseball pitchers completed the study and wore a PULSE Throw Workload Monitor to track peak arm slot angle, peak arm velocity, and peak elbow varus torque, while a radar gun measured ball velocity. An 8-week pitching program had subjects throw 30 and 50 maximum effort pitches in the first and eighth week, respectively, while workload increased by 5 maximum effort pitches every 2 weeks. Paired samples t-tests were conducted to compare variables of interest before and after an 8-week fall season with an alpha level set at 0.05. There was no significant difference in peak arm slot angle, peak arm velocity, and peak elbow varus torque (p > 0.05); however, there was a significant decrease in ball velocity (p < 0.001). These data indicate that 8-week pitching programs, not coupled with a resistance training regimen, negatively affect a pitcher's ball velocity. Sport coaches and practitioners should thus make accommodations to access the necessary equipment for a pitching and strength training program to be implemented simultaneously to ensure that pitchers are prepared to perform at an optimal level during the spring season.

Abstract: Suzuki, K, Mizoguchi, Y, Kimura, F, Fujisaki, K, Yokoyama, D, Hall, T, and Akasaka, K. Correlation between muscle strength, swing speed, batting statistics, and body composition parameters in high school baseball players: a retrospective observational study. J Strength Cond Res XX(X): 000-000, 2024-Body composition has emerged as a pivotal factor influencing baseball player performance. The purpose of this study was to examine the relationships between muscle strength, swing speed, batting statistics, and body composition in high school baseball players. This retrospective study evaluated 29 high school baseball players included critical parameters related to body composition (body fat percentage, lean body mass [LBM], fat mass index [FMI], and fat-free mass index [FFMI]), muscle strength (bench press, squat, deadlift), batting statistics (batting average, on-base percentage, slugging percentage, on-base plus slugging), and swing speed. These metrics were gathered using a body composition analyzer (Omron HBF-701; Omron Healthcare Co., Kyoto, Japan). After the correlation analysis with body composition, a subsequent multivariate analysis was conducted. Multivariate regression analysis identified LBM (p < 0.05, p < 0.01) as a significant predictor for bench press and swing speed, FFMI for squat (p < 0.01), and FMI for deadlift (p < 0.05). No significant association was found between body composition and batting statistics. Lean body mass has been identified as an important contributing factor to swing speed, suggesting the need for body composition management among high school baseball players and coaches to enhance performance and functionality. However, no association was found between batting statistics and body composition. Therefore, it is suggested that high school baseball players prioritize the development of technical skills over swing speed and muscle strength to improve batting statistics.

Abstract: Churilla, JR, Boyer, WR, Richardson, MR, and Williams, CC. Associations between relative lower and upper body strength and hyperinsulinemia in U.S. Adults: NHANES 1999-2002 and 2011-2014. J Strength Cond Res XX(X): 000-000, 2024-Skeletal muscle (SM) is an insulin-sensitive tissue that aids in glucose homeostasis. Insulin resistance leads to chronic hyperglycemia and type 2 diabetes. Previous evidence suggests that greater SM strength and size improve insulin dynamics. The primary aim of this study was to examine the association(s) between relative lower and upper body strength and hyperinsulinemia in a nationally representative sample of US adults. Samples of adult (≥50 years) subjects in the 1999-2002 (N = 1,097) and adults (≥20 years) in the 2011-2014 (N = 2,576) National Health and Nutrition Examination Survey were used in the analyses. Significance was set at p ≤ 0.05 for regression models. Quartiles (Q) of relative lower body strength (RLBS [N·BMI-1]) and relative grip strength (RGS [kg·BMI-1]) were created. Hyperinsulinemia was calculated using the weighted 75th percentile of log-fasted insulin among adults without diabetes. Inverse dose-response relationships were found for decreasing prevalence estimates of hyperinsulinemia by increasing Q of both RLBS and RGS. Similar dose-response associations were revealed for increasing Q of both RLBS and RGS and mean insulin concentrations. Following adjustment for demographic and lifestyle variables, subjects in Q2, Q3, and Q4 of RLBS were found to have significantly lower odds of hyperinsulinemia (OR 0.58 [P = 0.05], OR 0.38, OR 0.22 [p < 0.05 for both], respectively). Subjects in Q2, Q3, and Q4 of RGS were also found to have lower odds of hyperinsulinemia (OR 0.30; OR 0.14; OR 0.05 [p < 0.0001 for all]), respectively. These data suggest RLBS and RGS may both be favorably associated with insulin homeostasis.

Abstract: Kissick, CR, Techmanski, BS, Comfort, P, and Suchomel, TJ. The reliability, bias, differences, and agreement between velocity measurement devices during the hang clean pull. J Strength Cond Res XX(X): 000-000, 2024-This study examined the reliability, bias, differences, and agreement between the GymAware PowerTool (GA) and Tendo Power Analyzer (TENDO) during the hang clean pull (HCP). Fourteen resistance-trained men performed HCP repetitions with 20, 40, 60, 80, 100, 120, and 140% of their 1 repetition maximum hang power clean (1RM HPC) with GA and TENDO devices attached to the barbell. Least-products regression was used to examine instances of proportional and fixed bias for mean barbell velocity (MBV) and peak barbell velocity (PBV) between devices. In addition, Hedge's g effect sizes were calculated to determine the magnitude of the differences between devices. Excellent reliability was displayed by the GA for all measurements. While excellent reliability for the TENDO was displayed for MBV across all loads, only moderate-good reliability was present for PBV at loads >80% 1RM. The TENDO displayed proportional bias for both MBV and PBV as well as fixed bias for PBV at 140% 1RM compared with the GA. Despite the small effect sizes that existed between devices for both MBV (g = 0.35-0.57) and PBV (g = 0.23-0.54), none of these differences were practically meaningful. The GA and TENDO are reliable devices that can measure MBV and PBV accurately during the HCP; however, practitioners should note that the TENDO may overestimate MBV and PBV to a small extent (3.7-6.8% and 1.8-2.9%).

Abstract: Talpey, SW, Drake, M, Haintz, L, Belanger, A, O'Grady, MW, Young, WB, Mundy, PD, James L, Gabbett, TJ, Gardner, EC. The reliability and validity of the rebound countermovement jump in National Collegiate Athletic Association Division I American Football Players. J Strength Cond Res XX(X): 000-000, 2024-The purpose of this study was to investigate the reliability and validity of the rebound countermovement jump (R-CMJ), as an alternate test of leg muscle function to the CMJ and drop jumps (DJs). Because the first phase of the R-CMJ mimics that of the CMJ, it is hypothesized that variables obtained in phase I of the R-CMJ will be like those of a CMJ. Similarly, because the second phase of a R-CMJ mimics a DJ, it is believed that the variables obtained from phase II will be like those from a DJ. Collegiate male American football players (N = 46) aged 18-24 years completed CMJs and R-CMJs on a portable force plate. Tests were completed on 3 separate days to determine the repeatability of select variables and to establish their validity. In addition, a subgroup (N = 20) of players from the cohort completed DJs from both 30 cm (DJ30) and 45 cm (DJ45) to determine the concurrent validity of the variables obtained from the second phase of the R-CMJ. Most variables obtained from the CMJ and R-CMJ phase I were found to be reliable, except for time-to-take-off. The variables from the DJ30, DJ45, and R-CMJ phase II displayed moderate to good reliability; however, all coefficient of variations were >10%. Jump height achieved in the CMJ was significantly greater than that achieved in phase I of the R-CMJ. The reactive strength index was significantly different in the R-CMJ compared with the DJ from both 30 and 45 cm heights. Although the R-CMJ may be inviting for coaches to use owing to its ease and time efficiency, the results of this study highlight that it may not provide a valid representation of an athlete's reactive strength.

Abstract: Roberts, TD, Smith, RW, Arnett, JE, Ortega, DG, Schmidt, RJ, and Housh, TJ. Cross-validation of equations for estimating 1 repetition maximum from repetitions to failure for the bench press and leg extension. J Strength Cond Res XX(X): 000-000, 2024-Eighteen previously published equations (EQs) that estimate 1 repetition maximum (1RM) from repetitions to failure (RTF) were cross-validated for the bench press (BP) and leg extension (LE) movements. Forty-three recreationally active men (age: 20.58 ± 1.47 years; body mass [BM]: 81.66 ± 13.65 kg) completed a 1RM test and RTF at 80% of the 1RM test for the LE, and 39 of the 43 men (age: 20.61 ± 1.48 years; BM: 83.58 ± 12.73 kg) completed the same tests for the BP. The EQs were categorized as generic (the source did not indicate its applicability for a specific movement) or movement-specific (BP-specific and LE-specific EQs). The generic EQs were cross-validated for both movements, whereas the BP-specific and LE-specific EQs were cross-validated for their respective movements only. The cross-validation criteria included calculations of the constant error (CE) (mean differences between estimated and measured 1RM), Pearson Correlation Coefficient, standard error of the estimate, and total error. The level of significance was set at p ≤ 0.05. After the initial cross-validation analyses of the previously published EQs, the most accurate EQs were modified by subtracting their cross-validation CE from the original EQ to improve their accuracy for estimating BP and LE 1RM by eliminating systematic error. The modified EQs were then cross-validated using the same statistical procedures. Based on the cross-validation analyses, we recommend the following EQs: BP 1RM = (RTF0.1 × weight) + 1.49 and LE 1RM = (RTF0.1 × weight) + 1.06 using weights that result in 4-10 RTF.

Abstract: Gries, KJ and Witto, PE. Age and sex differences in IRONMAN world championship performance. J Strength Cond Res XX(X): 000-000, 2024-There has been an increasing number of masters athletes, particularly women, who have been competing in ultra-endurance events. With this in mind, we sought to determine the influence of age and sex on IRONMAN World Championship performances from 2014 to 2023. The final times of each component (swim, bike, and run) and overall time were collected for places 1st to 10th in each age group (18-69 years). Sex differences in performance were calculated for each age group. Depth of field (time of nth place/first place), a surrogate for participation, was also calculated for each age group and sex. Significance was set at p < 0.05. These data show a ∼12% sex difference in the performance of the swim, bike, run, and final (p < 0.05), which increased to 20% in the 65-69 years age group (p < 0.05). The differences appeared driven by the bike and run. Depth of field was greater in men than in women (p < 0.05), and the sex difference increased with age. Sex differences in performance trended to be related to depth of field (p = 0.08; R2 = 0.32), suggesting a moderate role of participation in performance sex differences. Although speculative, the performance data can give us an insight into the physiology and sociology of these elite athletes and warrants future research.

Abstract: Hsu, SM, Tseng, WC, Chiu, CH, Hsieh, TY, Weng, MC, Dai, X, and Chen, CH. Effects of preconditioning lower-extremity resistance exercises on multi directional repeated sprinting-induced muscle damage. J Strength Cond Res XX(X): 000-000, 2024-Sprint exercise-induced muscle damage is a popular area of investigation. To examine whether preconditioning lower-extremity resistance exercises would reduce the amount of muscle damage observed after a multi-directional repeated sprinting (MDS) exercise. Thirty-six elite male athletes were randomly allocated to 1 of 3 groups: general warm-up (GW), GW with loaded jump squat (SQ), and GW with loaded hip thrust (HT). Knee flexion isometric strength (MVIC), passive hip flexion range of motion (ROM), soreness, countermovement jump (CMJ), sprint time, and plasma creatine kinase (CK) activity were measured at the pretest and post-24, -48, and -72 hours of the MDS. For SQ, the CK at post-72 hours was significantly lower than the GW group. The decrements of MVIC at post-48 and -72 hours for SQ were significantly less than the GW group. The CMJs at post-24 and -48 hours for SQ and at post-48 and -72 hours for HT were significantly higher than the GW group. The 0-10 m sprint time at post-48 hour for HT was significantly better than the GW group. Adding the SQ or HT interventions to a GW before MDS has a protective effect on the sprinting-induced muscle damage and faster recovery.