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Gillen ZM, Burch RF, Saucier DN, Strawderman L, Luczak T, Piroli A, Petway AJ, Rath T. Effects of a Strength and Conditioning Offseason Program on Countermovement Jump Ground Reaction Forces in Division I American Football Players. J Strength Cond Res 2024; 38:e86-e95. [PMID: 38088878 DOI: 10.1519/jsc.0000000000004660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/29/2024]
Abstract
ABSTRACT Gillen, ZM, Burch, RF, Saucier, DN, Strawderman, L, Luczak, T, Piroli, A, Petway, AJ, and Rath, T. Effects of a strength and conditioning offseason program on countermovement jump ground reaction forces in Division I American football players. J Strength Cond Res 38(3): e86-e95, 2024-The purpose of this study was to examine the effects of a 10-week strength and conditioning offseason program on the ground reaction forces (GRFs) of American football players during single-leg and double-leg countermovement jumps (SLJ and CMJ, respectively). Each subject visited the laboratory twice, once for preoffseason and once for postoffseason testing. During each visit, subjects performed CMJs and SLJs for each leg. Ground reaction forces were collected by force plates to quantify unweighting, braking, propulsive, and performance metrics for each jump. In addition, an efficiency index was calculated for each jump to examine changes in vertical jump efficiency. Dependent samples t tests compared all CMJ metrics. Two-way repeated measures analyses of variance (leg × time) compared all SLJ metrics. An alpha level of p ≤ 0.05 was considered statistically significant. For the CMJ, propulsive phase duration decreased due to the program ( p = 0.007), whereas peak braking power, peak propulsive power, mean propulsive force, and jump height increased ( p ≤ 0.012). For the SLJ, peak braking power, force at the low position, braking rate of force development, eccentric force, peak propulsive power, mean propulsive force, and jump height increased in both legs ( p ≤ 0.044). The efficiency index increased for the CMJ and the SLJ for both legs ( p ≤ 0.016). This study demonstrated that SLJ and CMJ vertical jump performance significantly increases in as few as 10 weeks of offseason strength and conditioning. Strength and conditioning programming may effectively increase vertical jump performance, as assessed by GRFs, which can be used as a simple indicator regarding changes in athletic performance.
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Affiliation(s)
- Zachary M Gillen
- Department of Kinesiology, Mississippi State University, Mississippi State, Mississippi
| | - Reuben F Burch
- Department of Industrial & Systems Engineering, Mississippi State University, Mississippi State, Mississippi
- Human Factors & Athlete Engineering, Center for Advanced Vehicular Systems, Mississippi State University, Mississippi State, Mississippi
| | - David N Saucier
- Human Factors & Athlete Engineering, Center for Advanced Vehicular Systems, Mississippi State University, Mississippi State, Mississippi
| | - Lesley Strawderman
- Department of Industrial & Systems Engineering, Mississippi State University, Mississippi State, Mississippi
| | - Tony Luczak
- National Strategic Planning & Analysis Research Center, Mississippi State University, Mississippi State, Mississippi
| | - Anthony Piroli
- Tampa Bay Buccaneers Strength & Conditioning, Tampa, Florida
| | - Adam J Petway
- Department of Industrial & Systems Engineering, Mississippi State University, Mississippi State, Mississippi
- Human Factors & Athlete Engineering, Center for Advanced Vehicular Systems, Mississippi State University, Mississippi State, Mississippi
- University of Louisville Strength & Conditioning, Louisville, Kentucky; and
| | - Ted Rath
- Philadelphia Eagles Strength & Conditioning, Philadelphia, Pennsylvania
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Li M, Meng X, Guan L, Kim Y, Kim S. Comparing the Effects of Static Stretching Alone and in Combination with Post-Activation Performance Enhancement on Squat Jump Performance at Different Knee Starting Angles. J Sports Sci Med 2023; 22:769-777. [PMID: 38045747 PMCID: PMC10690507 DOI: 10.52082/jssm.2023.769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Accepted: 11/06/2023] [Indexed: 12/05/2023]
Abstract
We aimed to investigate the impact of isolated static stretching (4 sets of 30 seconds) and its combined form with 10 repetitive drop jumps on lower limb performance during squat jumps at different knee joint starting angles (60°, 90°, and 120°). Thirteen participants completed three randomly ordered experimental visits, each including a standardized warm-up and squat jumps at three angles, apart from the intervention or control. Information was gathered through a three-dimensional movement tracking system, electromyography system, and force platform. The electromyography data underwent wavelet analysis to compute the energy values across the four wavelet frequency bands. The average power (Pavg), peak power (Ppeak), peak ground reaction force (GRFpeak), peak center of mass velocity (Vpeak), and force-velocity relationship at peak power (SFv) were extracted from the force and velocity-time data. The results revealed no significant influence of isolated static stretching, or its combined form with drop jumps, on the energy values across the frequency bands of the gastrocnemius, biceps femoris and rectus femoris, or the Pavg or Ppeak (P > 0.05). However, at 120°, static stretching reduced the GRFpeak (P = 0.001, d = 0.86) and SFv (P < 0.001, d = 1.12), and increased the Vpeak (P = 0.001, d = 0.5). The GRFpeak, Pavg, Ppeak, and SFv increased with an increase in the joint angle (P < 0.05), whereas the Vpeak decreased (P < 0.05). These findings suggest that static stretching does not diminish power output during squat jumps at the three angles; however, it alters GRFpeak, Vpeak, and the relative contributions of force and velocity to peak power at 120°, which can be eliminated by post-activation performance enhancement. Moreover, compared to 60° and 90°, 120° was more favorable for power and peak force output.
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Affiliation(s)
- Ming Li
- Department of Physical Education, Jeonbuk National University, Republic of Korea
| | - Xiangwei Meng
- Department of Physical Education, Jeonbuk National University, Republic of Korea
| | - Lihao Guan
- Department of Physical Education, Jeonbuk National University, Republic of Korea
| | - Youngsuk Kim
- Department of Physical Education, Jeonbuk National University, Republic of Korea
| | - Sukwon Kim
- Department of Physical Education, Jeonbuk National University, Republic of Korea
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Krzyszkowski J, Chowning LD, Harry JR. Phase-Specific Verbal Cue Effects on Countermovement Jump Performance. J Strength Cond Res 2022; 36:3352-3358. [PMID: 34533485 DOI: 10.1519/jsc.0000000000004136] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
ABSTRACT Krzyszkowski, J, Chowning, LD, and Harry, JR. Phase-Specific Verbal Cue Effects on Countermovement Jump Performance. J Strength Cond Res 36(12): 3352-3358, 2022-The aim of this study was to determine whether countermovement vertical jump (CMVJ) phase-specific cues can improve jump performance and phase-specific force-time characteristics. Twenty-nine subjects (14 males and 15 females) performed 15 total CMVJ trials (5 per condition) while being provided with a control and phase-specific (unloading phase and eccentric braking phases) foci of attention. Jump height, reactive strength index-modified, countermovement depth, time-to-takeoff, and CMVJ subphase force-time characteristics were compared between each phase-specific verbal cues and the control condition using paired samples t-tests ( α = 0.05) and Cohen's d effect sizes ( d ; large >1.2). Female ( d = 0.242; p = 0.012) and male ( d = 1.96; p = 0.047) subjects achieved greater jump heights in the control condition compared with the unloading phase condition. Females demonstrated a faster unloading phase, less unloading force, greater unloading yank, and greater braking force during the unloading condition, as well as greater eccentric braking force during the eccentric braking condition compared with the control condition ( p ≤ 0.014; d ≥ 0.242). Males exhibited less body mass unloading, greater unloading yank, faster eccentric braking time, greater eccentric braking force, and greater eccentric braking yank for both the unloading and eccentric braking conditions compared with the control condition ( p ≤ 0.047; d ≥ 0.196). Collectively, these results suggest that phase-specific foci of attention do not acutely improve jump performance but can enhance phase-specific force-time characteristics in recreationally active individuals. Specifically, practitioners should consider using an eccentric braking phase instruction for individuals need to improve eccentric braking force generation.
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Affiliation(s)
- John Krzyszkowski
- Human Performance & Biomechanics Laboratory, Department of Kinesiology & Sport Management, Texas Tech University, Lubbock, Texas
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Gillen ZM, McHugh MP, Shoemaker ME, Cramer JT. Comparisons of countermovement jump force profiles in youth athletes. TRANSLATIONAL SPORTS MEDICINE 2021. [DOI: 10.1002/tsm2.257] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Zachary M. Gillen
- Department of Kinesiology Mississippi State University Mississippi State MS USA
| | - Malachy P. McHugh
- Nicholas Institute of Sports Medicine and Athletic TraumaLenox Hill Hospital New York NY USA
| | - Marni E. Shoemaker
- College of Health SciencesThe University of Texas at El Paso El Paso TX USA
| | - Joel T. Cramer
- College of Health SciencesThe University of Texas at El Paso El Paso TX USA
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