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John L Grace, Meghan E Hancock, Madison L Malone, Bahman Adlou, Jerad J Kosek, Hannah R Houde, Christopher M Wilburn, Wendi H Weimar School of Kinesiology, Auburn University, Auburn, AL, USACorrespondence: John L Grace, School of Kinesiology, Auburn University, 301 Wire Road, Auburn, AL, 36849, USA, Tel +1 (334) 844-1468, Fax +1 (334) 844-1469, Email jlg0068@auburn.eduIntroduction: The National Football League (NFL) combine tests the athleticism of prospects competing for the draft. The vertical jump is included to test lower extremity power, yet the components which lead to the greatest performance remain elusive. Therefore, this study aimed to utilize a sample of elite athletes to analyze vertical jump components associated with increased performance and the relationship between vertical jump performance and rookie-year success.Methods: Videos of 50 NFL prospects performing the vertical jump task were analyzed for various countermovement jump components. Regression analyses examined the components in relation to normalized jump height and rookie Approximate Value (AV) using an alpha level of 0.05.Results: After analysis, only the overall model for normalized jump height was statistically significant (R^2^ = 0.69, p = 0.002).Discussion: While no single variable predicted jump height, distinct strategies were evident between the top and bottom 25% performers based on component correlations. The regression model approached significance in predicting rookie AV (R^2^ = 0.94, p = 0.052), with notable components like heel pauses for skilled positions and greater knee flexion for linemen. By creating models that can predict jump height or AV, variables can be identified that can be used to improve one’s jump height or, in the case of AV, that can be used to predict which draft prospects will perform better in the NFL.Keywords: athletes, technique, biomechanics, sport, video analysis

We examined how set-volume equated resistance training using either the back squat (SQ) or hip thrust (HT) affected hypertrophy and various strength outcomes. Untrained college-aged participants were randomized into HT (n = 18) or SQ (n = 16) groups. Surface electromyograms (sEMG) from the right gluteus maximus and medius muscles were obtained during the first training session. Participants completed 9 weeks of supervised training (15-17 sessions), before and after which gluteus and leg muscle cross-sectional area (mCSA) was assessed via magnetic resonance imaging. Strength was also assessed prior to and after the training intervention via three-repetition maximum (3RM) testing and an isometric wall push test. Gluteus mCSA increases were similar across both groups. Specifically, estimates [(-) favors HT (+) favors SQ] modestly favored the HT versus SQ for lower [effect ±SE, -1.6 ± 2.1 cm 2 ; CI 95% (-6.1, 2.0)], mid [-0.5 ± 1.7 cm 2 ; CI 95% (-4.0, 2.6)], and upper [-0.5 ± 2.6 cm 2 ; CI 95% (-5.8, 4.1)] gluteal mCSAs but with appreciable variance. Gluteus medius + minimus [-1.8 ± 1.5 cm 2 ; CI 95% (-4.6, 1.4)] and hamstrings [0.1 ± 0.6 cm 2 ; CI 95% (-0.9, 1.4)] mCSA demonstrated little to no growth with small differences between groups. mCSA changes were greater in SQ for the quadriceps [3.6 ± 1.5 cm 2 ; CI 95% (0.7, 6.4)] and adductors [2.5 ± 0.7 cm 2 ; CI 95% (1.2, 3.9)]. Squat 3RM increases favored SQ [14 ± 2 kg; CI 95% (9, 18),] and hip thrust 3RM favored HT [-26 ± 5 kg; CI 95% (-34, -16)]. 3RM deadlift [0 ± 2 kg; CI 95% (-4, 3)] and wall push strength [-7 ± 12N; CI 95% (-32, 17)] similarly improved. All measured gluteal sites showed greater mean sEMG amplitudes during the first bout hip thrust versus squat set, but this did not consistently predict gluteal hypertrophy outcomes. Squat and hip thrust training elicited similar gluteal hypertrophy, greater thigh hypertrophy in SQ, strength increases that favored exercise allocation, and similar deadlift and wall push strength increases., Competing Interests: BC and MH disclose that they sell exercise-related products and services. However, neither was involved in any aspect of the study beyond assisting with the study design and providing funds to partially cover participant and MRI costs through a gift to the laboratory of MR. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Plotkin, Rodas, Vigotsky, McIntosh, Breeze, Ubrik, Robitzsch, Agyin-Birikorang, Mattingly, Michel, Kontos, Lennon, Frugé, Wilburn, Weimar, Bashir, Beyers, Henselmans, Contreras and Roberts.)

Lower extremity multi-joint strength curves tend not to evaluate individual joint contributions to endpoint force in maximum effort isometric whole limb extension. Therefore, the purpose of this study was to measure the contribution of the hip, knee, and ankle to vertical ground reaction force in maximum effort isometric whole limb extension at various postures. An effect of posture on the contributions of the hip, knee, and ankle to vertical ground reaction force was found ( F (3,96) = 85.31, p < 0.0001; F (3,96) = 21.32, p < 0.0001; F (3,96) = 130.61, p < 0.0001 for the hip, knee, and ankle, respectively). The hip and knee contributed most to vertical endpoint force when the lower limb was in a flexed posture, and their contributions decreased when posture was extended. Conversely, the ankle contributed least when the limb was flexed, but its contribution increased as posture was changed from flexed to more extended. In comparison to recent research involving induced acceleration analysis, it appears that the hip, knee, and ankle utilize the same force allocation strategy in multi-joint maximum effort isometric leg extensions and activities of daily living.