Journal of Strength and Conditioning Research最新文献

Abstract: Calaway, C, Walls, K, Levitt, H, Caplan, J, Mann, B, Martinez, K, Gastaldo, R, Haq, I, and Signorile, JF. Frequency of velocity-based-training frequency impacts changes in muscle morphology, neuromuscular performance and functional capability in persons with Parkinson's disease. J Strength Cond Res XX(X): 000-000, 2024-Velocity-based training (VBT) positively impacts muscle morphology and performance in persons with Parkinson's disease (PD); however, optimal training frequencies for VBT in patients with PD remain undetermined. Changes in ultrasound-determined muscle thickness (MT) and echo intensity (EI)-derived muscle quality of the rectus femoris (RF) and vastus lateralis (VL), neuromuscular performance, and functional capacity were examined following 2 VBT frequencies (2-3 d·wk-1) using 30% velocity loss thresholds for 12 weeks. Neuromuscular performance was assessed using computerized pneumatic resistance machines. For each variable, 2 (time) × 2 (group) repeated-measures analyses of variance (ANOVA) were used to determine significant main effects and interactions. Significant time effects were seen for MT and EI of all muscles (p < 0.05). Muscle thickness improvements included right VL (RVL) (0.171 ± 0.065 cm; p = 0.019), left VL (LVL) (0.214 ± 0.101 cm; p = 0.049), right RF (RRF) (0.194 ± 0.077 cm; p = 0.023), and left RF (LRF) (0.318 ± 0.109 cm; p = 0.010). For EI, improvements occurred in RVL (-18.688 ± 3.600; p = <0.001), LVL (-10.959 ± 4.894; p = 0.040), RRF (-9.516 ± 3.537; p = 0.016), and LRF (-9.018 ± 3.444; p = 0.019). Time effects were seen for leg-press 1-repetition maximum and peak power (p < 0.01) and habitual walking speed (p = 0.022), with a group by time interaction for maximal gait speed favoring the 3 d·wk-1 condition (∆0.15 m·s-1, p = 0.002). The results indicate that VBT at 2 or 3 d·wk-1 can significantly improve muscle morphology, neuromuscular performance, and functional capability in patients with PD; however, improvements in maximal gait speed require 3 d·wk-1. These findings provide flexibility when developing exercise prescriptions for patients with PD.

Abstract: Gillen, ZM. Position-specific differences in speed profiles among NFL scouting combine participants. J Strength Cond Res XX(X): 000-000, 2024-This study examined the relationships between speed profiles and athletic performance measurements from the National Football League (NFL) Scouting Combine, and position-specific differences in speed profiles. Subjects included NFL Scouting Combines participants with valid scores for the 40-yard dash, as well as the 10- and 20-yard splits of the 40-yard dash (n = 2,156). Subjects were divided into the following position groups: defensive backs (DBs, n = 421), defensive linemen (DL, n = 356), linebackers (LBs, n = 261), offensive linemen (OL, n = 354), running backs (RBs, n = 217), tight ends (TEs, n = 122), quarterbacks (QBs, n = 108), and wide receivers (WRs, n = 317). Performance measures included 40-yard dash time (with 10- and 20-yard split times), bench press repetitions to failure, vertical jump height, broad jump distance, pro-agility time, and L-cone drill time. The 40-yard dash and its splits calculated vmax, τ, and amax to reflect speed profiles. One-way analysis of variances examined position-related differences. Pearson's product moment correlation coefficients examined relationships between performance measures and speed profile variables. Skill positions (DB and WR) had the greatest vmax and amax, and lowest τ, followed by big skill positions (LB, RB, TE, QB), followed by DL, then OL with the lowest vmax and amax, and highest τ. For skill and big skill positions, vmax, τ, and amax exhibited greater relationships with combine measures, whereas OL generally had the lowest relationships. The position-specific differences in this study demonstrate potential areas of strength and weakness for certain positions. This may help guide strength and conditioning coaches desiring to improve position-specific speed and acceleration capabilities for American football players.

Abstract: Sandau, I and Kipp, K. Prediction of snatch and clean and jerk performance from physical performance measures in elite male weightlifters. J Strength Cond Res XX(X): 000-000, 2024-This study aimed to build a valid model to predict maximal weightlifting competition performance using ordinary least squares linear regression (OLR) and penalized (Ridge) linear regression (penLR) in 29 elite male weightlifters. One repetition maximum (1RM) or 3RM test results of assistant exercises were used as predictors. Maximal performance data of competition and assistant exercises were collected during a macrocycle in preparation for a competition. One repetition maximum snatch pull, 3RM back squat, 1RM overhead press, and body mass were used to predict the 1RM snatch; and 1RM clean pull, 3RM front squat, 1RM overhead press, and body mass were used to predict the 1RM clean and jerk. Model validation was performed using cross-validation (CV) and external validation (EV; random unknown dataset) for the coefficient of determination and root mean square error (RMSE). Results revealed that penLR models present more plausible output in the relative importance of highly correlated predictors. Of note, the 1RM snatch pull is the most relevant predictor for the 1RM snatch, whereas the 1RM clean pull and 3RM front squat are the most relevant predictors for the 1RM clean and jerk. Validation-based absolute predictive error (RMSE) ranged between ≈ 3-9 kg for the 1RM snatch and ≈ 3-7 kg for the 1RM clean and jerk, depending on the model (OLR vs. penLR) and validation procedure (CV vs. EV). In conclusion, penLR models should be used over OLR models to analyze highly correlated predictors because of more plausible model coefficients and smaller predictive errors.

Abstract: Lewis, A, Rattray, B, and Flood, A. Does cathodal preconditioning enhance the effects of subsequent anodal transcranial direct current stimulation on corticospinal excitability and grip strength? J Strength Cond Res XX(X): 000-000, 2024-Inconsistent effects of transcranial direct current stimulation (tDCS) on corticospinal excitability (CSE) and exercise performance are commonly reported. Cathodal preconditioning, involving cathodal tDCS delivered before anodal tDCS over the same region, may enhance changes in CSE and exercise beyond that resulting from anodal tDCS alone. This study aimed to investigate whether the effects of anodal tDCS on CSE and isometric grip strength can be enhanced by cathodal preconditioning. Thirty-five healthy subjects aged 19-37 years completed a familiarization session followed by 4 stimulation conditions presented in a randomized cross-over design across 4 separate sessions. tDCS doses were applied at 2 mA over the primary motor cortex for 10 minutes. Corticospinal excitability was assessed using 120% of resting motor threshold and an input/output curve of motor evoked potentials of the first dorsal interosseous. Grip strength was evaluated as time to exhaustion (TTE) in a sustained isometric contraction. Relative to conventional sham stimulation, TTE was significantly increased by 15% after conventional anodal tDCS. Corticospinal excitability increased in response to tDCS, but this effect did not differ across conditions. Cathodal preconditioning before anodal stimulation did not increase CSE or grip strength beyond that seen in the other stimulation conditions. Our findings did not reveal any significant impact of stimulation type on CSE. Notably, anodal tDCS led to a significant improvement in grip strength endurance. However, cathodal preconditioning did not seem to increase the effect of subsequent anodal stimulation on CSE nor grip strength.

Abstract: Takuya, Y, Taro, I, Chihiro, K, Mana, O, Takahiro, O, and Masako, H. Evaluation of trunk oblique muscle activities in baseball batters using T2-weighted magnetic resonance imaging. J Strength Cond Res XX(X): 000-000, 2024-This study investigated abdominal oblique muscle activity using T2-weighted imaging in baseball batting. For this purpose, 17 baseball batters (21.6 ± 2.7 years, 173.9 ± 4.0 cm, 77.5 ± 7.6 kg) performed 100 toss-batting trials. Before and after toss-batting, 3 Tesla magnetic resonance imaging scans were performed to obtain the T2 values of the 4 abdominal external and internal oblique muscle pairs. The results showed that the T2 values of all abdominal oblique muscles were significantly increased after the 100 trials (p < 0.05), with no differences in these increases between the muscles. The rate of change in the T2 values was 1.0 ± 3.9% and 4.2 ± 5.2% for the external and internal oblique muscles on the pitcher's side and 3.2 ± 5.1% and 0.9 ± 2.5% for the external and internal oblique muscles on the catcher's side, respectively. These findings indicate that the activity levels of all abdominal oblique muscles during baseball battings are similar and lower than those of the agonist muscles used during resistance exercise and sprinting. These findings suggest that baseball batting is a low-intensity exercise of the abdominal oblique muscles, but adequate training of each abdominal oblique muscle may improve batting performance and prevent injury.

Abstract: Cardoso, F, Costa, MJ, Colaço, P, Vilas-Boas, JP, Pinho, JC, Pyne, DB, and Fernandes, RJ. Ventilatory and perceived ergogenic effects of mandibular forward repositioning during running at maximal oxygen uptake intensity. J Strength Cond Res XX(X): 000-000, 2024-Wearing an intraoral dental splint may enhance ventilatory function and exercise performance. Nineteen runners performed on a 400-m outdoor track: (a) an incremental protocol to assess the velocity at maximal oxygen uptake (vV̇o2max) and (b) 2 square wave bouts wearing 2 intraoral splints (with and without mandibular forward repositioning). The time until exhaustion at vV̇o2max (TLimv V̇o2max), ventilatory variables, oxygen uptake (V̇o2) kinetics, energetic profiling, perceived exertion and kinematics, were all measured. Ventilatory data were assessed breath-by-breath and perceived exertion evaluated using the Borg 6-20-point scale at the end of TLimv V̇o2max bouts. Images were recorded by video cameras (120 Hz) and kinematic measures retrieved using Kinovea. A paired t test was computed for comparison of splints (p ≤ 0.05). With (vs. without) mandibular forward repositioning, runners increased their TLimv V̇o2max by ∼6% (p = 0.03), coupled with higher ventilation (151 ± 22 vs. 147 ± 23 L·min-1, p = 0.04), end-tidal oxygen tension (114.3 ± 3.7 vs. 112.9 ± 3.9 mm Hg, p = 0.003), and lower inspiratory time (0.526 ± 0.083 vs. 0.540 ± 0.090 seconds, p = 0.02), despite similar V̇o2 kinetics (e.g., 49.0 ± 8.7 vs. 47.7 ± 8.6 ml∙kg∙min-1 of fast component amplitude) being observed. The energy expenditure was ∼8% higher (p = 0.03) with the mandible forward, coupled with lower perceived exertion scores (p = 0.04). Mandibular forward repositioning was effective in acutely improving running performance at vV̇o2max with ergogenic effects on ventilatory and perceived variables.

Abstract: Chae, S, McDowell, KW, Baur, ML, Long, SA, Tufano, JJ, and Stone, MH. Accentuated eccentric loading and alternative set structures: A narrative review for potential synergies in resistance training. J Strength Cond Res XX(X): 000-000, 2024-As athletes become adapted to training over time, it becomes more difficult to develop their strength and power. In a conventional resistance training strategy, volume or load may be increased to provide novel stimuli to break through a plateau. However, physiological stress markers increase with increased volume or load, which is an innate shortcoming. In that case, practitioners strive to develop unconventional strategies that could increase training stimuli while adjusting fatigue. Two programming tactics, accentuated eccentric loading (AEL) using eccentric overload and alternative set structures (AS) using intraset rests, have been reported to increase training stimuli and alleviate fatigue, respectively. Importantly, when merging AEL and AS in various contexts, the 2 benefits could be accomplished together. Because AEL and AS cause different outcomes, it is important to deal with when and how they may be integrated into periodization. Moreover, prescribing eccentric overload and intraset rests requires logistical considerations that need to be addressed. This review discusses the scientific and practical aspects of AEL and AS to further optimize strength and power adaptations. This review discusses (a) scientific evidence as to which tactic is effective for a certain block, (b) potential practical applications, and (c) related discussions and future research directions.

Abstract: Trecroci, A, Cavaggioni, L, Rossi, A, Bongiovanni, T, Invernizzi, PL, Formenti, D, and Longo, S. Self-regulated learning assessment in young soccer players: beyond competitive levels. J Strength Cond Res XX(X): 000-000, 2024-This study explores self-regulated learning (SRL) among young soccer players, transcending the traditional focus on competitive levels. One hundred twenty-four soccer players of regional and provincial levels from under 14 to under 17 age groups voluntarily participated in the study and were combined into a single group. A median-split method based on total time performance was used to separate players into low performers (LPs) and high performers (HPs) from a 90° change of direction dribbling test. The self-regulation of learning-self-report scale for sport practice (SRL-SRS-SP) with a 5-factor solution (planning, reflection, effort, self-efficacy, and self-supervision) and 31 items was used. The score was based on a 1-5 Likert scale. The level of significance was set at p-value < 0.05. The SRL-SRS-SP total score by HP players differed significantly from that of LP players (p = 0.015). Regarding each subscale, HP players showed significantly higher scores than LP players (p = 0.011) for planning, whereas no differences were observed for the remaining factors (p ≥ 0.05). The main observation of this study revealed that HP soccer players had a greater level of engagement in the learning process with a remarkable ability to plan for specific improvement than LP peers. This suggests that the competitive level might not be the sole determinant of differences in SRL. Therefore, strength and conditioning coaches should emphasize metacognitive and motivational components because of their crucial role in enhancing technical and physical performance.

Abstract: McMahon, G, Best, N, Coulter, T, and Erskine, RM. Increased neuromuscular activation, force output and resistance exercise volume when using 5-minute compared with 2-minute rest intervals between the sets. J Strength Cond Res 38(9): 1527-1534, 2024-Longer rest intervals between resistance exercise (RE) sets may promote greater muscle hypertrophy and strength gains over time by facilitating the completion of greater training volume and intensity. However, little is known about the acute neuromuscular responses to RE sets incorporating longer vs. shorter rest intervals. Using a within-subject, crossover design, 8 healthy, young subjects completed 2 separate acute bouts of 4 sets of 8 × 3-s maximal isometric contractions using either a 2-minute (REST-2) or 5-minute (REST-5) rest interval between sets. Peak torque (PT) and electromyography (EMG) were measured pre and 5 minutes postexercise. Peak torque and mean torque (MT), EMG, mean, and median frequencies were measured during each set, whereas blood lactate (BLa), heart rate (HR), and rating of perceived exertion (RPE) were measured following each set. Peak torque and MT were lower ( p < 0.05) in sets 3 and 4, and sets 2-4 in REST-2 compared with REST-5, respectively. Electromyography and BL were lower and higher, respectively, in REST-2 vs. REST-5. There was no main effect of condition on HR or RPE. Pre-to-post exercise reductions in PT (-17 ± 9% vs. -4 ± 7%) and EMG (-29 ± 14% vs. -10 ± 7%) were greater ( p < 0.001) in REST-2 vs. REST-5. Total exercise volume was less in REST-2 vs. REST-5 (9,748 ± 2296 N·m -1 vs. 11,212 ± 2513 N·m -1 , p < 0.001). These results suggest that incorporating 5-minute between-set rest intervals into a resistance exercise session facilitates improved neuromuscular function, increased exercise volume, and less metabolic stress compared with 2-minute rest intervals. Thus, 5-minute rest intervals may be more efficacious for promoting muscle hypertrophy and strength gains in a chronic resistance training program.

Abstract: Chéradame, J, Loursac, R, Piscione, J, Carling, C, Decq, P, and Jacqmin-Gadda, H. Impact of weekly training-load structure and content on the risk of injury in professional Rugby Union match-play. J Strength Cond Res 38(9): 1613-1619, 2024-The aim of this study was to investigate the impact of different components of daily training load during the week preceding the match on the risk of sustaining a match injury in professional rugby union. A cohort of 72 players from a single professional French club participated. Global positioning system-derived data including total distance (TD) and high-speed distance in addition to ratings of perceived effort (RPE) for both on- and off-pitch (gym-based strength conditioning work) training were collected for each training session over 3 seasons (2017-2020). The association between the daily measures of external and internal training load over the week preceding the day of the match (MD) and the subsequent risk of injury in match-play was estimated using a mixed-effects logistic model adjusted for contextual and individual factors. A total of 184 injuries were sustained in 128 matches (incidence: 81.2 injuries per 1,000 player hours). Higher RPE values for the strength conditioning session on MD-5 ( p < 0.001) and for the on-pitch session on MD-1 ( p = 0.04) were associated with an increased risk of injury in matches. On MD-2, a higher TD covered and that run at high speed (>MAS) were, respectively, associated with a higher ( p = 0.03) and lower risk ( p = 0.02) of injury in matches played. This study in professional rugby union shows that different components of external and internal load had varying influences on injury risk and particularly in relation to the day on which these were performed in the week leading up to the next match. At MD-2, training load favoring intensity rather than volume could reduce the risk of match-play injury.