Journal of Strength and Conditioning Research最新文献

Abstract: Jiang, G, Tan, X, Zou, J, and Wu, X. A 24-week combined resistance and balance training program improves physical function in older adults: a randomized controlled trial. J Strength Cond Res 39(1): e62-e69, 2025-This randomized controlled trial assessed the feasibility of older adults performing combined resistance and balance training (RBT) and compared the effects of RBT on physical function with those of resistance training (RT) alone and with no exercise training in older adults. In total, 65 community-dwelling adults aged 60-74 years were randomly assigned to an RT (n = 22), RBT (n = 22), or control (n = 21) group. The exercise intervention consisted of RT or RBT for 45 minutes, 3 times per week for 24 weeks. The control group engaged in no exercise training. The compliance rates were 93% in the RT group and 92% in the RBT group. No training-related adverse effect was observed. In the RT and RBT groups, dynamic balance (p = 0.017; p < 0.001, respectively), maximum walking speed (p = 0.014; p < 0.001), upper extremity (p = 0.013; p = 0.009) and lower extremity (p = 0.009; p < 0.001) muscle strength, and spirometry (p = 0.043; p = 0.018) were significantly improved at 24 weeks compared with the control group. Only the RBT group showed significant improvement in normal walking speed (p = 0.002). Compared with the RT group, the RBT group showed additional significant improvements in dynamic balance (p = 0.001) and lower limb muscle strength (p = 0.027). The findings of this randomized controlled trial indicated that RBT was safe and feasible for older adults. Long-term RBT had better effects than either no exercise training or RT alone on improving physical function in older adults. Compared with RT, RBT additionally benefited dynamic balance and lower limb muscle function, which are clinically important factors in preventing falls, frailty, disability, and other geriatric syndromes.

Abstract: Yang, Y-R, Chen, C, Pan, C-H, Yen, S-Y, and Cheng, C-F. Effects of half-time re-warm-up with core strength exercises on subsequent agility and power performance in basketball players. J Strength Cond Res 39(1): 62-69, 2025-This study investigated the effects of half-time re-warm-up (RW) comprising core strength exercise (CSE) on basketball players' subsequent power and change of direction (COD) performance. Twelve male collegiate basketball players were recruited to perform 3 conditions--CSE RW on a stable platform (STA) or an unstable platform (USTA) and passive rest (control, CON)--in randomized, counter-balanced order after a modified Loughborough intermittent shuttle test (LIST). The COD and power performance tests were administered before the LIST and after the interventions. Heart rate (HR) was continuously measured during each trial. Results showed significantly lower changes in T-test time in STA compared with CON (p < 0.05). Changes in countermovement jump height in STA were significantly higher than those in CON (p < 0.05). During the isometric midthigh pull test, changes in the maximum rate of force development (RFD) (p < 0.05), RFD in the range of 0-90 milliseconds (p < 0.05), 0-150 milliseconds (p < 0.05), 0-200 milliseconds (p < 0.05), and 0-250 milliseconds (p < 0.05), in STA were significantly higher than those in CON. In addition, RFD in the range of 0-150 milliseconds (p < 0.05) and 0-250 milliseconds (p < 0.05) in USTA was significantly higher than that in CON. The mean HR during USTA was significantly higher than that in STA and CON (p < 0.05). These findings indicated that CSE RW during halftime might prevent power and COD performance decline in the second half of a game, with practical implications for coaches and players.

Abstract: Somma, M and Lawrence, MA. Reliability and accuracy of Stryd to detect changes in vertical displacement of the center of mass while running. J Strength Cond Res XX(X): 000-000, 2024-The purpose of this study was to determine if Stryd can reliably and accurately detect changes in vertical displacement of the center of mass (VCoM) that are produced when cadence was increased by 5 and 10%. A secondary purpose of this investigation was to determine the interlimb reliability of Stryd for VCoM and cadence. Twenty healthy individuals (5 males, 15 females; age: 24.5 ± 1.5 years; mass: 67.1 ± 12.2 kg; height: 1.66 ± 0.01 m) were fitted for motion capture and 2 Stryd devices. After warm-up, subjects ran at a self-selected speed on the treadmill for each condition (self-selected, +5%, and +10% cadence) while VCoM and cadence were collected simultaneously from Stryd and motion capture. Reliability between the Stryd devices on different limbs was excellent for both cadence (intraclass correlation coefficient [ICC] = 0.999, p < 0.001) and VCoM (ICC = 0.993, p < 0.001). Cadence was not significantly different between the Stryd device and motion capture (p = 0.153). Stryd produced significantly (p < 0.001) smaller values for VCoM regardless of condition, with average differences ranging between 4.4 and 4.6 cm. A linear regression revealed that Stryd predicted 50.7% of variation in motion capture VCoM (p < 0.001). Stryd can reliably measure both cadence and VCoM regardless of which limb it is placed on, as indicated by the near-perfect agreement between Stryd devices, and the Stryd device can detect and predict changes in VCoM. However, Stryd consistently underestimates VCoM, which can be corrected by using a linear regression equation.

Abstract: Lockie, RG, Young, MA, Lanham, SN, Orr, RM, Dawes, JJ, and Nagel, TR. Scenario and shooting performance in incumbent deputy sheriffs/police officers, cadets, and cadets who worked in custody/corrections facilities. J Strength Cond Res XX(X): 000-000, 2024-Job-specific fitness of law enforcement personnel can decline during their careers. Personnel could offset fitness deficiencies with greater skill and knowledge. Cadets in certain counties may work in custody/corrections before their training academy. This study used archival data to compare job-specific scenario performance of incumbent deputy sheriffs/police officers (INC; n = 15), cadets entering academy (CAD; n = 19), and cadets entering academy after working in custody/corrections facilities (CADCUST; n = 25). Subjects completed a scenario (step-ups, jumping jacks, sprawls, strikes, drags, sandbag carries, and a simulated fight) as fast as possible followed by a firearms test where they had to hit 6 steel plates. Steel time (time to hit all plates) and number of shots required were recorded. Univariate analysis of covariances, with sex and age as covariates and Bonferroni post hoc analyses, derived between-group differences in all variables (p < 0.05). The CAD group completed the scenario faster than the INC group (p = 0.011). Though not significant, the INC group did have the fastest steel time and lowest number of shots. The CADCUST group completed the scenario 10% slower than the CAD group, was 138-366% slower in steel time, and needed 61-100% more shots than the other groups. The INC group likely had fitness limitations that affected scenario performance but demonstrated better shooting skills. The CADCUST group was slower than the CAD group in the scenario and performed worst in the shooting test. Cadets who work in custody/corrections facilities before academy may require fitness and skill interventions while INC should attempt to maintain their fitness during their career.

Abstract: Rebelo, A, Loturco, I, Pereira, JR, Martinho, DV, Valente-dos-Santos, J, and Broek, GV. Impact of congested match schedules on countermovement jump metrics in elite volleyball players. J Strength Cond Res XX(X): 000-000, 2024-The aim of this study was to assess the impact of a congested match schedule on various countermovement jump (CMJ) metrics recorded across the braking, transfer, propulsive, and flight phases of the CMJ. Fourteen male elite volleyball players were monitored across 7 microcycles, with CMJ assessments conducted at 14 time points using portable force plates. Repeated measures analysis of variance with Bonferroni post hoc tests and coefficient of variation (CV) analysis were used to analyze the data. The CVs for all metrics indicated a moderate variability between microcycles and low variability between the beginning and end of the weeks. Significant variability was observed in key performance metrics, including peak propulsive power (p < 0.001, partial eta squared [ηp2] = 0.336), peak propulsive velocity (p = 0.005, ηp2 = 0.207), propulsive phase duration (p = 0.008, ηp2 = 0.197), and jump momentum (p = 0.019, ηp2 = 0.225), across microcycles. These findings indicate that these CMJ metrics may be used as sensitive indicators of fatigue and performance changes during intense training and competitive periods. The total score of athleticism, calculated by averaging a set of standardized scores from multiple tests or repeated measures of the same test, for the propulsive and flight phases, proved to be particularly useful in providing a comprehensive view of the neuromuscular status. This emphasizes the importance of recording and analyzing a range of CMJ metrics to optimize training and recovery strategies in elite volleyball players.

Abstract: Haynes, H, Tinsley, GM, Swafford, SH, Compton, AT, Moore, J, Donahue, PT, and Graybeal, AJ. Mobile anthropometry in Division I baseball athletes: evaluation of an existing application and the development of new equations. J Strength Cond Res XX(X): 000-000, 2024-The purpose of this study was to evaluate the agreement between mobile application and dual-energy x-ray absorptiometry (DXA)-derived body composition parameters in a group of Division I (DI) collegiate baseball athletes and to develop new equations for this population using this mobile technique. A total of 41 (age: 20.5 ± 1.5 years; DXA %fat: 18.9 ± 4.6%) DI collegiate baseball athletes underwent body composition assessments using DXA and a mobile anthropometric application. Total and appendicular body composition estimates were produced from this mobile application using previously developed equations and evaluated against the reference (DXA) in the complete sample of athletes. Least absolute shrinkage and selection operator regressions were then used to develop new equations using the mobile application in a portion of the athletes (n = 34) and subsequently tested in the remaining athletes (n = 7). In the complete sample, no body composition estimate using the mobile application's existing equations (R2: 0.00-0.68) demonstrated equivalence with DXA, including estimates of %fat (R2: 0.37; root-mean-squared error [RMSE]: 3.74%), fat mass (FM), and total (appendicular lean mass [ALM]) and leg lean mass ([ALMlegs] R2: 0.67-0.68; RMSE: 3.43-4.86 kg). In the testing sample, estimates produced from the newly developed equations demonstrated acceptable performance when compared to DXA, most notably %fat (R2: 0.80; RMSE: 3.66%), FM, ALM, and ALMlegs (R2: 0.55-0.87; RMSE: 0.74-3.46 kg). Previously developed equations using mobile anthropometrics may not demonstrate acceptable agreement with DXA in DI collegiate baseball athletes, and newly developed equations specific to this group may be more suitable. Those employing these newly developed equations should use caution until further external cross-validation is performed.

Abstract: Oddsson, HR, Friðgeirsdóttir, KÝ, Hafliðadóttir, L, Einarsson, IÞ, Kristjánsdóttir, H, and Saavedra, JM. Differences in anthropometric parameters, physical fitness, and kicking speed in young football players according to performance level, playing position, and relative age effect: a population-based study. J Strength Cond Res XX(X): 000-000, 2024-The objectives of this study were to determine (a) the differences, both in male and female players, in anthropometric parameters, physical fitness, and kicking speed based on the players' level and position on the field; (b) whether there is a relative age effect based on the players' level, and (c) whether there is a relationship between the relative age effect and the anthropometric parameters, physical fitness, and kicking speed parameters. Eight hundred twenty-six football players (15.76 ± 2.60 year old, 75.7% male) participated in the study. Players were grouped into elite and nonelite, as well as based on their field position and birth quartile. Nonparametric tests were used to study differences by level and by position or trimesters. Chi-square goodness of fit analysis was performed to know the association between elite and nonelite players regarding the relative age effect. Physical fitness parameters and kicking speed were higher in elite players than in nonelite players (5.834 ≥χ2 ≤ 48.079; p < 0.001). There were differences in anthropometric and physical fitness parameters and kicking speed depending on the player's position: goalkeeper vs. outfield players (7.648 ≥χ2 ≤ 26.078; p < 0.001) except in jump tests. There was a relative age effect in elite male players (χ2 = 26.313; p < 0.001) but not in female players, and it was related to anthropometric and physical fitness parameters. This population-based study offers insights into the variables that differentiate elite from nonelite players at young ages, with differences in the relative age effect between male and female players, which can be used by coaches to identify key performance variables.

Abstract: He, P, Ye, Z, Liu, M, Zhang, Y, Zhou, C, Zhang, Y, Yang, S, and Qin, X. Associations of handgrip strength, walking pace, and genetic risks with incident arrhythmias. J Strength Cond Res XX(X): 000-000, 2024-We quantified the associations of handgrip strength and walking pace with incident arrhythmias using Cox proportional hazards models with hazards ratios (HRs). The study included 487,673 subjects, with an average age of 56.4 years, 54.8% female, and free of baseline arrhythmias from the UK Biobank prospective study. Handgrip strength was assessed by a dynamometer. Low handgrip strength was defined as less than 27 kg in men and 16 kg in women. Walking pace was self-reported as slow, average, or brisk. The arrhythmia categories involved incident atrial fibrillation (AF), incident ventricular arrhythmias, and incident bradyarrhythmia, respectively. Over a median follow-up duration of 12.4 years, 28,967 (5.9%), 4,061 (0.8%), and 11,741 (2.4%) subjects developed incident AF, incident ventricular arrhythmias, and incident bradyarrhythmia, respectively. Compared with those with low handgrip strength, the adjusted HRs (95% confidence interval [CI]) of incident AF, ventricular arrhythmias, and bradyarrhythmia in subjects with normal handgrip strength were 0.76 (95% CI: 0.73.-0.79), 0.75 (95% CI: 0.67.-0.84), and 0.80 (95% CI: 0.74.-0.85), respectively. Compared with those with a slow walking pace, subjects with a brisk walking pace had significantly lower risks of incident AF (HR, 0.56; 95% CI: 0.53.-0.58), ventricular arrhythmias (HR, 0.52; 95% CI: 0.45.-0.59), and bradyarrhythmia (HR, 0.63; 95% CI: 0.59.-0.68). In addition, the inverse associations of handgrip strength and walking pace with AF were significantly stronger among those with a lower genetic risk of AF (both p interaction <0.001). In conclusion, handgrip strength and walking pace were inversely associated with incident arrhythmias. The inverse associations for incident AF were stronger in those with a lower genetic risk of AF.

Abstract: Chiba, Y, Sato, K, Yoshimoto, T, Ohnuma, H, Yamanaka, R, Takahashi, K, Kobayashi, K, Matsubayashi, T, and Takai, Y. Revamping pace distribution: A case study on elevating the men's 400 m track and field Japanese national record after 32 years. J Strength Cond Res XX(X): 000-000, 2024-Many studies have investigated the 400-m sprint, and the optimal pacing strategy is subject to debate. Little information is available regarding the effects of changes in the pacing strategy on running speed and spatiotemporal variables in the official 400-m race. This case study analyzed changes in running speed and spatiotemporal variables of a Japanese elite long sprinter who set a new Japanese national record in the 400-m race by modifying his pace distribution based on the analysis of his previous races and the performances of world-class long sprinters. To revamp his pace distribution, 25 preceding races (ranging from 45.47 to 46.95 seconds) were analyzed, spanning from June 2015 to June 2023. The independent variables were the 50-m split time, average running speed, percentage of the 50-m split time relative to the 400-m record, step length, and step frequency. K.S. broke his own record by modifying the pacing distribution based on the development of his previous race and the world-class long sprinters. The modified pacing strategy increased running speed in the 200- to 300-m section. Step lengths were longer throughout the 400 m, and step frequencies were higher in the last 200 m than before the alteration in the pace distribution. Modifying the pacing strategy from leading to driving may enhance the personal records of long sprinters. This improvement is attributed to the maintenance of longer step lengths over the entire 400-m range and an increase in the step frequency in the last 200 m.

Abstract: Şentürk, D, Akyildiz, Z, Janicijevic, D, and García-Ramos, A. Sensitivity of the load-velocity relationship variables to discriminate the level of fatigue induced by multiple sets of the hexagonal barbell deadlift exercise. J Strength Cond Res XX(X): 000-000, 2024-This study aimed to evaluate changes in load-velocity (L-V) relationship variables (L0, v0, and Aline) after different fatigue protocols and to determine their correlation with changes in 1 repetition maximum (1RM). After determining the hexagonal barbell deadlift (HBD) 1RM, 27 resistance-trained men randomly completed 3 sessions that only differed in the activity performed between 2 incremental loading tests that were performed at the beginning (presession) and end (postsession) of the session: (a) control protocol: no training; (b) moderate-fatigue protocol: 5 sets of the HBD exercise at 70% 1RM performing half the maximum possible number of repetitions; and (c) high-fatigue protocol: 5 sets of the HBD exercise performed to failure against the 70% 1RM. Significance was set at an alpha level of 0.05. The reduction of 1RM (p < 0.001), v0 (p = 0.014), and Aline (p < 0.001) at postsession was greater for the high-fatigue protocol, followed by the moderate-fatigue protocol, and finally the control protocol. The changes in L0 did not differ between the fatigue protocols (p = 0.372). The percent change in the 1RM at postsession was significantly correlated with the percent change in Aline (r = 0.714) and L0 (r = 0.540), but not with the percent changes in v0 (r = 0.177). These results suggest that the L-V relationship variables offer a highly sensitive and practical solution for fatigue monitoring.