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Jason D. Stone, Adam C. King, Shiho Goto, John D. Mata, Joseph Hannon, James C. Garrison, James Bothwell, Andrew R. Jagim, Margaret T. Jones and Jonathan M. Oliver

increasing risk for injury 9 and limiting skill transfer to sport. Previous studies suggest that joint kinetics and kinematics vary at differing loads 10 – 12 and/or positioning 13 , 14 during the performance of the back squat, an important exercise for strength–power athletes. 15 In experienced

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Jonathon Weakley, Carlos Ramirez-Lopez, Shaun McLaren, Nick Dalton-Barron, Dan Weaving, Ben Jones, Kevin Till and Harry Banyard

repetition data during the barbell back squat. Eighteen team sport athletes volunteered to complete the 3 resistance training protocols, with 2 athletes being lost to follow up. Following a familiarization session, athletes completed a 10%, 20%, and 30% velocity loss condition that was based on an initial

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Laurent B. Seitz, Gabriel S. Trajano and G. Gregory Haff

Purpose:

To compare the acute effects of back squats and power cleans on sprint performance.

Methods:

Thirteen elite junior rugby league players performed 20-m linear sprints before and 7 min after 2 different conditioning activities or 1 control condition. The conditioning activities included 1 set of 3 back squats or power cleans at 90% 1-repetition maximum. A 2 × 2 repeated-measures ANOVA was used to compare preconditioning and postconditioning changes in sprint performance.

Results:

Both the back-squat and power-clean conditioning activities demonstrated a potentiation effect as indicated by improved sprint time (back squat: P = .001, ES = –0.66; power cleans: P = .001, ES = –0.92), velocity (back squat: P = .001, ES = 0.63; power cleans: P = .001, ES = 0.84), and average acceleration over 20 m (back squat: P = .001, ES = 0.70; power cleans: P = .001, ES = 1.00). No potentiation effect was observed after the control condition. Overall, the power clean induced a greater improvement in sprint time (P = .042, ES = 0.83), velocity (P = .047, ES = 1.17), and average acceleration (P = .05, ES = 0.87) than the back squat.

Conclusions:

Back-squat and power-clean conditioning activities both induced improvements in sprint performance when included as part of a potentiation protocol. However, the magnitude of improvement was greater after the power cleans. From a practical perspective, strength and conditioning coaches should consider using power cleans rather than back squats to maximize the performance effects of potentiation complexes targeting the development of sprint performance.

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Harry G. Banyard, Ken Nosaka, Kimitake Sato and G. Gregory Haff

Purpose:

To examine the validity of 2 kinematic systems for assessing mean velocity (MV), peak velocity (PV), mean force (MF), peak force (PF), mean power (MP), and peak power (PP) during the full-depth free-weight back squat performed with maximal concentric effort.

Methods:

Ten strength-trained men (26.1 ± 3.0 y, 1.81 ± 0.07 m, 82.0 ± 10.6 kg) performed three 1-repetition-maximum (1RM) trials on 3 separate days, encompassing lifts performed at 6 relative intensities including 20%, 40%, 60%, 80%, 90%, and 100% of 1RM. Each repetition was simultaneously recorded by a PUSH band and commercial linear position transducer (LPT) (GymAware [GYM]) and compared with measurements collected by a laboratory-based testing device consisting of 4 LPTs and a force plate.

Results:

Trials 2 and 3 were used for validity analyses. Combining all 120 repetitions indicated that the GYM was highly valid for assessing all criterion variables while the PUSH was only highly valid for estimations of PF (r = .94, CV = 5.4%, ES = 0.28, SEE = 135.5 N). At each relative intensity, the GYM was highly valid for assessing all criterion variables except for PP at 20% (ES = 0.81) and 40% (ES = 0.67) of 1RM. Moreover, the PUSH was only able to accurately estimate PF across all relative intensities (r = .92–.98, CV = 4.0–8.3%, ES = 0.04–0.26, SEE = 79.8–213.1 N).

Conclusions:

PUSH accuracy for determining MV, PV, MF, MP, and PP across all 6 relative intensities was questionable for the back squat, yet the GYM was highly valid at assessing all criterion variables, with some caution given to estimations of MP and PP performed at lighter loads.

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James J. Tufano, Jenny A. Conlon, Sophia Nimphius, Lee E. Brown, Laurent B. Seitz, Bryce D. Williamson and G. Gregory Haff

Purpose:

To compare the effects of a traditional set structure and 2 cluster set structures on force, velocity, and power during back squats in strength-trained men.

Methods:

Twelve men (25.8 ± 5.1 y, 1.74 ± 0.07 m, 79.3 ± 8.2 kg) performed 3 sets of 12 repetitions at 60% of 1-repetition maximum using 3 different set structures: traditional sets (TS), cluster sets of 4 (CS4), and cluster sets of 2 (CS2).

Results:

When averaged across all repetitions, peak velocity (PV), mean velocity (MV), peak power (PP), and mean power (MP) were greater in CS2 and CS4 than in TS (P < .01), with CS2 also resulting in greater values than CS4 (P < .02). When examining individual sets within each set structure, PV, MV, PP, and MP decreased during the course of TS (effect sizes 0.28–0.99), whereas no decreases were noted during CS2 (effect sizes 0.00–0.13) or CS4 (effect sizes 0.00–0.29).

Conclusions:

These results demonstrate that CS structures maintain velocity and power, whereas TS structures do not. Furthermore, increasing the frequency of intraset rest intervals in CS structures maximizes this effect and should be used if maximal velocity is to be maintained during training.

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Harry G. Banyard, Kazunori Nosaka, Alex D. Vernon and G. Gregory Haff

provided within a training set for a consistent range of motion, velocity will decline as concentric muscular fatigue ensues. 9 Currently, it is not known what occurs to movement velocity between training sessions when an athlete is fatigued in nonballistic-type exercises, such as the barbell back squat

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Harry G. Banyard, James J. Tufano, Jose Delgado, Steve W. Thompson and Kazunori Nosaka

conceivable that lighter loads (LVP method) or fewer repetitions (FS VL method) would be completed. Methods Participants Fifteen resistance-trained male volunteers participated in this study (age: 25.1 [3.9] y, height: 179.7 [6.7] cm, and body mass: 83.9 [10.6] kg) and performed the full-depth back squat

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Samuel T. Orange, James W. Metcalfe, Ashley Robinson, Mark J. Applegarth and Andreas Liefeith

study used a parallel group randomized design. Participants were randomly allocated (1:1) to 7 weeks of either VBT or PBT in block sizes of 4 using online randomization software. Both groups completed 2 resistance-training sessions per week that involved the back squat. VBT involved adjusting back squat

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Jonathon Weakley, Kevin Till, John Sampson, Harry Banyard, Cedric Leduc, Kyle Wilson, Greg Roe and Ben Jones

found to enhance acute training performance and physical development. 2 , 7 , 8 By providing kinematic feedback to athletes as they train, acute improvements in jump squat, 9 bench press throw, 7 and barbell back squat 2 performance have been shown to occur. For example, Argus et al 7 demonstrated

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Justin J. Merrigan, James J. Tufano, Jonathan M. Oliver, Jason B. White, Jennifer B. Fields and Margaret T. Jones

velocity across sets. 3 Therefore, this style of acute training may not be ideal when aiming to maintain power, as demonstrated in the jump squat, 4 , 5 back squat, 1 , 6 and weight-lifting exercises. 7 , 8 Of interest, is the manipulation of training variables, such as rest time, that may reduce the