Journal of Strength and Conditioning Research最新文献

Abstract: Springham, M, Singh, N, Stewart, P, Matthews, J, Jones, I, Norton-Sherwood, C, May, D, Salter, J, Strudwick, AJ, and Shaw, JW. The moderating effect of match external load on neuromuscular performance in U-18 English Premier League academy football players: A principal component regression approach. J Strength Cond Res 40(2): e172-e179, 2026-We examined the moderating effect of match external load measures on neuromuscular performance in U-18 English Premier League (EPL) football players. Seventeen male outfield players completed countermovement jump (CMJ) and isometric hip adductor (IADS) and posterior chain strength tests 1 day before (MD-1) and 2 days after (MD+2) 8 competitive games. Total, high-speed running, high metabolic load, explosive and Zone6 distances, and the total number of accelerations and decelerations were recorded using global positioning system and microelectrical mechanical sensor devices. Standardized changes to neuromuscular performance measures (CMJ jump height and IADS and isometric posterior chain strength peak force) were summated to create a total score of neuromuscular performance. Principal component (PC) analysis and a linear mixed-effects regression model examined the relationships between external load and neuromuscular performance changes with significance set to p < 0.050. Two PCs explained 93% of the variance in external load variables. PC1 had an equal contribution from all external load metrics and was therefore considered representative of total match volume. PC2 was primarily composed from Zone6 and high-speed running distance and was therefore considered representative of high-speed running and sprint volume. Standardized neuromuscular performance reduced by 0.85 from MD-1 to MD+2. PC1 (mean: 0.0 ± 2.4, range: -5.9 to 4.8) had a significant negative relationship with neuromuscular performance ( β = -0.23, p = 0.044) and IADS peak force ( β = -0.15, p = 0.007), but no other components exerted significant effects ( p ≥ 0.121). Match volume exerts a negative linear effect on neuromuscular performance and IADS peak force in U-18 EPL academy football players.

Abstract: Saini, AS, Sharma, SK, Kushwah, GS, Phukan, MI, McCabe, C, and Thapa, RK. Effects of three different volumes of in-water warm-up protocols in acute physiologic responses and 100 m swimming performance across all strokes. J Strength Cond Res 40(2): 191-197, 2026-This study examined the effects of 3 in-water warm-up (WU) protocols of varying volumes (600, 1,200, and 1,800 m) on acute physiologic responses and 100-m swimming performance across all strokes. Forty male national-level swimmers (21.0 ± 2.0 years) participated in a randomized crossover study, performing each WU protocol followed by a 100-m time trial in their respective strokes. Physiologic metrics, including blood lactate, temperature, heart rate, and rating of perceived exertion (RPE), were recorded. A repeated measures ANOVA was used to investigate the effects of the 3 protocols on physiologic and swimming performance across all the strokes. Results showed that the regular WU (1,200 m) led to significantly faster times in backstroke (65.56 ± 1.14 seconds vs 67.02 ± 1.20 seconds), breaststroke (70.73 ± 0.94 seconds vs 72.73 ± 0.94 seconds), and butterfly (58.64 ± 0.77 seconds vs 60.53 ± 0.86 seconds) than the long WU (1,800 m) ( p < 0.05). For the butterfly, the short WU (600 m) also resulted in significantly better swimming performance than the long WU. No significant differences were observed in freestyle performance among the 3 WU protocols, nor were there differences in heart rate across all strokes ( p > 0.05). Higher blood lactate and tympanic temperatures were observed after regular WU, while RPE was lowest after the short WU. This study emphasizes the importance of optimizing WU volumes based on stroke-specific demands in swimming. In addition, it also suggests practitioners to be cautious about using heart rate as a sole marker of WU effectiveness in swimming.

Abstract: Fields, JB, Jones, MT, Kitts, SE, King, EL, and Jagim, AR. Relationships between disordered eating, body dissatisfaction, and low energy availability in women collegiate athletes. J Strength Cond Res 40(2): e164-e171, 2026-Women collegiate student-athletes face unique challenges regarding nutrition, body image, and athletic performance, increasing their risk for low energy availability (LEA), disordered eating (DE), and body dissatisfaction (BID). However, limited data exist exploring LEA, DE, and BID across a variety of women's sports. Therefore, the purpose of this study was to evaluate the prevalence of and relationships among LEA risk, DE behaviors, and BID in women collegiate athletes from multiple sports. Division I, II, and III women student-athletes ( n = 115) participated in this cross-sectional, descriptive study. Athletes completed the low energy availability for females questionnaire (LEAF-Q), eating attitudes test (EAT-26), muscularity-oriented eating test (MOET), and body dissatisfaction items from the eating disorder examination questionnaire (EDE-Q) to assess LEA risk, DE behaviors, and BID, respectively. Sixty-four percentages of athletes were at risk for LEA, with the highest prevalence in volleyball (100%), wrestling (68%), lacrosse (67%), and cross country (57%). However, only 8% of athletes were classified at risk for eating disorders. Notably, 81 and 84% of athletes reported body weight and shape dissatisfaction, respectively, which was strongly associated with disordered eating behaviors (EAT-26: r = 0.707; MOET: r = 0.723, p < 0.001). These results show a high prevalence of LEA risk and BID across athletes, with DE behaviors strongly linked to body image concerns. Despite a high LEA risk among athletes, clinical eating disorder risk remained low, suggesting that undereating may often be unintentional. Targeted interventions focused on nutritional education, body image, and psychological support are critical for improving health and performance outcomes among collegiate women student-athletes.

Abstract: Tallis, J, Bolt, L, Morris, OR, Suchomel, TJ, and Eustace, SJ. Between session reliability of traditional and temporal bilateral and unilateral dynamic strength index calculations and association with sprint and change of direction performance. J Strength Cond Res 40(2): 167-179, 2026-The present study aimed to (a) evaluate the between session reliability of traditional and temporal based bilateral and unilateral dynamic strength index (DSI); (b) determine the association between DSI and sprint and change of direction performance in participants clustered by DSI root metrics. Thirty-eight recreationally active male participants (age: 23.4 ± 3.4 years) completed 20-m sprints, 5-0-5 change of direction test, bilateral and unilateral countermovement jumps (CMJ), and isometric midthigh pulls (IMTP) on 2 occasions. Vertical ground reaction force profiles were assessed to determine traditional DSI (DSI T ), DSI based on mean force achieved after 100 milliseconds (DSI 100 ), 150 milliseconds (DSI 150 ), the entire CMJ propulsive phase (DSI P ), and CMJ propulsive impulse (DSI I ). Bayesian interclass correlation coefficients and multiple linear regression after K-means clustering were used to analyze the data. Between session reliability of DSI was poor-moderate (interclass correlation coefficient [ICC] = 0.24-0.76) and highest for DSI T measures, albeit with some uncertainty (95% Higher Density Intervals [HDI]: 0.53-0.87). Bilateral temporal based DSI reliability was greater compared with unliteral equivalents, and temporal based DSI calculated for the nondominant limb, and those determined over a small-time epoch for the dominant limb were poor. There was limited association across DSI measures and straight-line 20-m sprint and 5-0-5 change of direction performance test. DSI 100 for the dominant side had the strongest association with the performance outcomes ( R2 = 0.33-0.36) and was improved in participants that expressed higher CMJ peak propulsive force. Dynamic strength index should be used with caution with respect to exercise prescription for the intention of improving tasks requiring rapid horizontal center of mass translation.

Abstract: Boccia, G, Serranò, S, Bonelli, B, La Torre, A, and Pavei, G. The scaling factor between jump height and ground contact time in drop jumps: A linear relationship at the individual level. J Strength Cond Res 40(2): 152-157, 2026-The extent to which jump height scales with changes in ground contact time (GCT) remains unknown. Establishing this relationship would enable more accurate comparisons of rebounds with different GCTs. Currently, to reliably compare reactive strength index (RSI) values, it is necessary to consider only those with similar contact time parameters. Elite young track and field athletes performed drop jumps from a 40 cm box under 3 distinct instructional conditions: (a) trade-off strategy-minimizing GCT while maximizing jump height; (b) maximizing jump height; (c) minimizing GCT. A hierarchical linear regression model was applied, with GCT and sex (male/female) as independent variables and jump height as the dependent variable. Compared with the trade-off condition, focusing on short GCT led to a 21-millisecond reduction in GCT ( p < 0.0001) but also a 5.9-cm decrease in jump height ( p < 0.0001). Conversely, prioritizing jump height increased jump height by 4.8 cm ( p < 0.0001) but prolonged GCT by 49 milliseconds ( p < 0.0001). However, RSI remained unaffected by instructions ( p = 0.567). A significant main effect of GCT on jump height was observed ( β = 0.154; p < 0.00001). The full model, incorporating random and fixed effects, accounted for 94% of the variance in jump height. At the individual level, our findings confirm a linear relationship between GCT and jump height. This relationship underscores the importance of considering the GCT-jump height trade-off when assessing drop jump performance and highlights the need for evaluations across various GCT ranges rather than relying solely on 1 jump strategy.

Abstract: As, H and Ozkaya, O. Evaluation of acute metabolic and physiologic responses obtained from sprint interval trainings performed by low cadence/high resistance and high cadence/low resistance. J Strength Cond Res 40(2): e117-e124, 2026-This study aimed to compare the acute metabolic and physiologic responses obtained from different sprint interval training (SIT) protocols performed by low cadence/high resistance and high cadence/low resistance. Ten moderately trained men completed two 6 × 30-second all-out SIT protocols with 4 minutes recovery periods as follows: (a) traditional fixed-load protocol, that is, using 7.5% of body mass (BM), (traditional SIT [SIT TRAD ]) and (b) adjusted-load protocol, that is, using an initial load of 5% of BM and then adjusting load for subsequent bouts based on the criterion of ≥120 rpm mean cadence for the last 5 seconds of each 30-second bout, (modified SIT [SIT MOD ]). Gas exchange variables and blood lactate concentration ([La]) were measured before, during, and after both protocols. Total net O 2 consumption and 3-hour postexercise recovery fat oxidation values were similar between SIT TRAD and SIT MOD ( p > 0.05). However, SIT MOD demonstrated a greater anaerobic contribution than SIT TRAD ( p < 0.001), despite similar aerobic contributions ( p = 0.32). The mean cadence was significantly higher in SIT MOD (139 ± 3) than that in SIT TRAD (98 ± 5 rpm; p < 0.001). SIT MOD elicited both the highest peak delta [La] (∆[La]) at the end of the session (19.6 ± 1.4 vs. 17.8 ± 1.8 mmol·L -1 , respectively; p = 0.003) and higher ∆[La] values at the 30th, 60th, 90th, and 120th minute of recovery compared with SIT TRAD (11.1 ± 1.4 vs. 8.3 ± 2.2, 4.5 ± 0.6 vs. 3.1 ± 1.1, 3.2 ± 0.8 vs. 1.9 ± 0.8, and 2.1 ± 0.9 vs. 0.7 ± 0.6 mmol·L -1 , respectively; p < 0.05). In conclusion, the high-cadence/low-resistance protocol (i.e., SIT MOD ) resulted in a greater anaerobic contribution than the traditional fixed-load protocol that leaded low cadence/high resistance (i.e., SIT TRAD ).

Abstract: Hummel, JW, Miltenberger, MM, Hummer, ET, and Spaeth, AM. Nocturnal sleep is associated with next-day vertical jump performance in collegiate athletes. J Strength Cond Res 40(2): 180-185, 2026-This study examined the relationship between nocturnal sleep and next-day vertical jump performance in NCAA Division I male football athletes. We hypothesized that longer sleep would be associated with better vertical jump performance and explored potential mediators of the relationship, including peak concentric force (N), peak concentric velocity (m·s -1 ), and countermovement depth (cm). A total of 174 athletes provided 4,049 instances of nocturnal sleep data (measured through photoplethysmography-based smart ring that was worn 5 nights/week) and next-day vertical jump performance. Each week, as part of routine team operations, athletes performed 3 vertical jumps in succession on a force plate and athletic staff calculated maximum and average jump height. A within-subject linear mixed-effects model assessed the relationship between sleep and vertical jump performance, and mediation analysis explored how sleep influenced vertical jump ability. Nocturnal sleep duration averaged 6.2 ± 1.1 hours per night, maximal jump height averaged 41.8 ± 7.8 cm, and average jump height averaged 40.2 ± 7.7 cm. Longer nocturnal sleep duration associated with better next-day vertical jump performance (maximal jump height: SE = 0.062, t = 3.07, 95% confidence interval (CI) [0.07-0.31], p = 0.002; average jump height: SE = 0.063, t = 4.41, 95% CI [0.15-0.40], p < 0.001). Countermovement depth significantly mediated the relationship between sleep and maximal jump performance ( β = -0.18, 95% CI [-0.25 to -0.13], p < 0.001), whereas peak concentric force and peak concentric velocity did not. These findings highlight the importance of prioritizing sufficient nocturnal sleep for optimizing anaerobic performance. Athletic staff should promote sleep hygiene to prevent sleep restriction in student athletes.

Abstract: Dicks, ND, Ketterling, JJ, Wooldridge, JD, Shoemaker, ME, and Barry, AM. Evaluating Army Combat Fitness Test scores: The influence of sleep, nutrition, and body composition in army reserve officers' training corps cadets. J Strength Cond Res 40(2): 218-224, 2026-The U.S. Army's Holistic Health and Fitness (H2F) program highlights the importance of physical, mental, nutritional, spiritual, and sleep domains for optimizing soldier readiness. Reserve Officers' Training Corps (ROTC) cadets must meet physical fitness standards, including the Army Combat Fitness Test (ACFT), yet often lack access to H2F resources. This cross-sectional study investigated how lifestyle factors-physical activity (PA), sleep quality, nutritional habits, and fat-free mass (FFM)-influence ACFT performance among Army ROTC cadets. Forty-six cadets (21.6 ± 2.0 years; women = 7) completed validated questionnaires assessing PA (IPAQ), sleep (PSQI), and nutrition (REAP-S), and underwent anthropometric testing. ACFT scores were obtained from the cadre within 30 days of survey completion. Cadets scoring ≥540 on the ACFT demonstrated significantly better sleep quality (PSQI; p < 0.01) and shorter sleep latency than those scoring <540. Backward linear regression identified PSQI as a significant negative predictor of ACFT scores ( β = -0.42, p = 0.007), with REAP-S and FFM showing marginal significance. Correlation analyses revealed small, significant associations between BF%, MVPA, and PSQI. The final regression model explained 22.4% of the variance in ACFT scores. These results emphasize the importance of sleep quality and body composition in cadet performance, suggesting that targeted education and training strategies could improve readiness in ROTC populations. Future programs should consider holistic approaches to cadet wellness, especially without formal H2F support.

Abstract: Wright, WC, Aguiar, EJ, Winchester, LJ, Fedewa, MV, and Esco, MR. Agreement between a motorized resistance device and traditional systems for sprint and change-of-direction testing in female volleyball players. J Strength Cond Res 40(2): 198-205, 2026-The purpose of this study was to determine the agreement between a motorized sprint resistance device (MSRD) and timing gates and an inertial measurement unit (IMU), for assessing time to completion and peak velocity during linear and change-of-direction tasks in elite female volleyball players. Elite volleyball athletes ( n = 16, 19.4 ± 1.5 years, 176.2 ± 10.6 cm, 71.5 ± 11.1 kg) performed the 18.29 m sprint and 5-10-5 drills while being simultaneously assessed using an MSRD, timing gates, and an IMU. Compared with timing gates for measuring sprint (3.09 ± 0.16 seconds) and 5-10-5 (5.08 ± 0.19 seconds) time, the MSRD showed significant ( p < 0.01) mean differences (3.15 ± 0.17 seconds [ p < 0.01, Cohen's d = 0.49, small ]) and 5.16 ± 0.21 seconds [ p < 0.01, Cohen's d = 1.14, moderate ], respectively, but the correlations were very large to nearly perfect ( r = 0.97 and 0.87, respectively). Limits of agreement (LOA) for sprint time were -0.10 ± 0.10 seconds and for 5-10-5 time were 0.23 ± 0.24 seconds. For peak velocity, the mean values from MSRD and IMU for the sprint (4.62 ± 0.34 m·s -1 and 4.72 ± 0.44 m·s -1 , respectively [ p = 0.78]) and 5-10-5 drill (3.91 ± 0.47 m·s -1 and 3.93 ± 0.50 m·s -1 , respectively [ p = 0.98]) were not significantly different. The correlation between the peak velocity values was significant for the sprint ( r = 0.65, p < 0.01), but not for 5-10-5 ( r = 0.25, p = 0.69), with LOA values of 0.03 ± 0.86 m·s -1 and 0.00 ± 0.98 m·s -1 , respectively. The MSRD seems to agree with timing gates for sprint and 5-10-5 time. However, the agreement with IMU for peak velocity is weaker.

Abstract: Fitas, A, Gomes, M, Santos, P, Pezarat-Correia, P, and Mendonca, GV. Sex differences in the back-squat one-repetition maximum estimation accuracy relying on the average optimal minimum velocity threshold. J Strength Cond Res 40(2): 136-142, 2026-The prediction of 1-repetition maximum (1RM) using the submaximal load-velocity relationship (LVR) is highly relevant in the field of strength and conditioning. The average optimal minimum velocity threshold (MVT)-velocity that minimizes the differences between actual and predicted 1RM-was recently proposed to overcome the limitations inherent to the individual optimal MVT: necessity of 1RM direct determination and the lack of knowledge regarding its longitudinal reliability. However, 1RM estimation accuracy based on this methodology has yet to be tested in female subjects. Individual LVRs of the Smith machine pause back squat were obtained in 16 male subjects and 16 female subjects. Estimations of 1RM were made based on sex specific average actual MVTs (1RM velocity) and average optimal MVTs (mean value of the individual actual and optimal MVTs). The accuracy of 1RM predictions was examined using absolute percentage error and Bland-Altman plots. Cross-validation was performed using a leave-one-out approach. Relative 1RM, the slope of the LVR, and the optimal MVT were similar in both sexes. In male subjects, 1RM estimation accuracy was similar regardless of the MVT used. In female subjects, however, the average optimal MVT reduced the absolute percentage error from 8.7 to 6.4% compared with the average actual MVT. However, wide limits of agreement (LoA) were found between actual and estimated 1RM using both approaches (∼15 and ∼10 kg, for male and female subjects, respectively). The average optimal MVT improves female subjects' 1RM estimation accuracy. Despite these findings, the width of the LoA may result in misestimations that are unacceptable for practical use.