International Journal of Sports Physiology and Performance, 2016, 11, 61  -65 http://dx.doi.org/10.1123/ijspp.2015-0028 © 2016 Human Kinetics, Inc.

ORIGINAL INVESTIGATION

Jump Shrug Height and Landing Forces Across Various Loads Timothy J. Suchomel, Christopher B. Taber, and Glenn A. Wright The purpose of this study was to examine the effect that load has on the mechanics of the jump shrug. Fifteen track and field and club/intramural athletes (age 21.7 ± 1.3 y, height 180.9 ± 6.6 cm, body mass 84.7 ± 13.2 kg, 1-repetition-maximum (1RM) hang power clean 109.1 ± 17.2 kg) performed repetitions of the jump shrug at 30%, 45%, 65%, and 80% of their 1RM hang power clean. Jump height, peak landing force, and potential energy of the system at jump-shrug apex were compared between loads using a series of 1-way repeated-measures ANOVAs. Statistical differences in jump height (P < .001), peak landing force (P = .012), and potential energy of the system (P < .001) existed; however, there were no statistically significant pairwise comparisons in peak landing force between loads (P > .05). The greatest magnitudes of jump height, peak landing force, and potential energy of the system at the apex of the jump shrug occurred at 30% 1RM hang power clean and decreased as the external load increased from 45% to 80% 1RM hang power clean. Relationships between peak landing force and potential energy of the system at jump-shrug apex indicate that the landing forces produced during the jump shrug may be due to the landing strategy used by the athletes, especially at lighter loads. Practitioners may prescribe heavier loads during the jump-shrug exercise without viewing landing force as a potential limitation. Keywords: weightlifting, weightlifting pulling derivatives, landing strategy, potential energy, jumping, triple extension The use of weightlifting movements and their derivatives in strength and conditioning programs is well documented. As a result, previous studies have sought to examine the best way to implement these exercises by examining the loading effects1–5 and identifying the optimal load for peak power development.6–10 More recently, however, researchers have been interested in comparing the kinetic and kinematic differences between weightlifting movements that involve the catch and their pulling derivatives that exclude the catch.11–14 These studies have indicated that weightlifting pulling derivatives that exclude the catch may produce a training stimulus that is as good as13,14 or better11,12 than weightlifting movements that involve the catch. Due to the potential benefits of weightlifting pulling derivatives, it appears that further research on how they should be implemented in a practical setting is warranted. The jump-shrug (JS) exercise is a weightlifting pulling derivative that is ballistic in nature and can be used in the teaching progression for the full weightlifting movements.3,11,12,15–17 Although it is not as widely used as other weightlifting derivatives, previous research has indicated that the JS may produce greater kinetic (ie, force, velocity, and power)11 and kinematic (ie, joint velocity)12 magnitudes than weightlifting derivatives that involve the catch phase. To successfully complete a repetition of the JS, an individual must begin in the midthigh position, perform a countermovement to a position where the bar is just above the knee, and without pausing transition back to the midthigh position and then jump as high as possible while simultaneously shrugging.15 A potential concern of practitioners is that the landing forces after the JS may be excessive. However, no previous study has examined how different loads during the JS affect the landing forces produced. If landing forces Suchomel and Taber are with the Dept of Exercise and Sport Sciences, East Tennessee State University, Johnson City, TN. Wright is with the Dept of Exercise and Sport Science, University of Wisconsin–La Crosse, La Crosse, WI. Address author correspondence to Timothy Suchomel at [email protected].

increase with a greater external load, practitioners may be averse to prescribing heavier loads with the JS. However, it is possible that landing forces may be maintained or decreased due to the likelihood of a decreased jump height and time for gravitational acceleration to act on an airborne mass with heavier loads. As previously mentioned, little research has examined the landing/impact phase of weightlifting movements and their derivatives. Moolyk et al18 examined the characteristics of lower-extremity work during the landing/impact phase of jump and drop landings, the clean, and power clean. Their results indicated that the drop landing and clean landing produced greater lower-extremity work than the jump landing. In addition, the work performed during the clean landing was greater than during the power-clean landing. It should be noted, however, that the previous study did not present effect-size magnitudes, and thus the practical significance between exercises cannot be interpreted. Although previous research has examined the impact that load has on force–time characteristics of the JS,3 it is unknown whether if the landing forces covary with changes in load. To effectively prescribe loads for the JS to meet the goals of different phases of training (eg, maximum strength, strength–power, speed), it is necessary to investigate all aspects of the exercise. Therefore, the purpose of this study was to examine the effect that load has on the mechanics of the JS.

Methods Design The current study used a repeated-measures design to examine the differences in jump height, peak landing force (PFLand), and potential energy of the lifter-plus-bar system (PE) at various loads during the JS exercise. Each subject attended a familiarization session followed by a testing session 2 to 7 days later. The familiarization session was used to determine each subject’s 1-repetition-maximum hang power clean (1RM HPC) and to allow the subjects to practice the JS 61

62  Suchomel, Taber, and Wright

before the testing session. During the testing session, each subject performed 3 single repetitions of the JS at relative loads of 30%, 45%, 65%, and 80% of their 1RM HPC on a force platform in a randomized order. A series of 1-way repeated-measures ANOVAs was used to compare the jump height, PFLand, and PE between loads.

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Subjects A convenience sample of 15 resistance-trained men, including National Collegiate Athletic Association (NCAA) Division III track and field athletes and collegiate club/intramural athletes, participated in this study (Table 1). The track and field athletes competed in short sprints, jumps, and throws, while the club/intramural-sport athletes competed in volleyball and basketball. This study was approved by the institutional review board at the University of Wisconsin–La Crosse. Additional approval was obtained from the institutional review board at East Tennessee State University. All subjects were informed of the possible risks of participation in the study and provided their written informed consent.

Procedures On arrival for the familiarization session, all subjects completed a standardized dynamic warm-up that consisted of 3 minutes of stationary cycling and dynamic stretches completed over 10 m (eg, walking forward lunge, walking hamstring stretch, walking quadriceps). The subjects then performed 5 slow body-weight squats, 5 fast body-weight squats, and 5 countermovement jumps of increasing intensity. This was followed by submaximal HPC sets at 30%, 50%, 70%, and 90% of each subject’s estimated 1RM HPC in accordance with previous research.1–3,11 It should be noted that a 1RM HPC was completed because it may be impractical for subjects to complete a 1RM JS in an athletic setting. Progressively heavier loads were lifted until the subject failed to complete a repetition; the greatest load that was successfully completed was recorded as his 1RM. Four minutes of recovery were provided to the subjects between maximal attempts. A minimum 2.5-kg increase in load was used between 1RM repetitions. All HPC repetitions were performed using the technique previously described by Suchomel et al.1 On completion of the 1RM HPC test, subjects performed light exercise sets with approximately 30% of their 1RM HPC to become proficient with the proper JS technique. All JS repetitions during the familiarization and testing sessions were completed with the technique previously described by Suchomel et al.15 Briefly, the subjects were required to start in the midthigh position, flex at the hip and lower the bar to the knee, and immediately transition back to the midthigh position into the second pull phase. On reaching the midthigh position, the subjects rapidly extended their hips, knees, and ankles and jumped as high as possible while simultaneously shrugging their shoulders. They were instructed to lower the barbell to a position just above the knee and immediately transition back

Table 1  Descriptive Subject Information (N = 15) Demographic or performance variable

Mean ± SD

Age (y)

21.7 ± 1.3

Height (cm)

180.9 ± 6.6

Body mass (kg)

84.7 ± 13.2

1-repetition-maximum hang power clean (kg)

109.1 ± 17.2

to the midthigh position in 1 fluid motion without pausing at the knee. No additional instruction was given to the subjects regarding the landing from the JS. Subjects returned 2 to 7 days after their familiarization session for their testing session. The same dynamic warm-up was performed before any testing repetitions. In addition, each subject performed submaximal exercise sets of the JS at 30% and 50% of his 1RM HPC. After completing the warm-up exercise sets, subjects performed 3 maximal-effort repetitions each of the JS at relative loads of 30%, 45%, 65%, and 80% of their 1RM HPC, totaling 12 repetitions. Specifically, 3 repetitions were performed at a given load and then the load was changed. The order of the loads was randomized to mitigate any potentiating or fatiguing effects. One minute of recovery was provided between repetitions, while 2 minutes of recovery were provided between loads. To reduce additional fatigue between repetitions, the subjects placed the barbell on the safety bars of a squat rack that was positioned just below the hip height for each subject. Before completing a repetition of the JS, the subjects lifted the barbell off of the safety bars and stepped backward onto the force plate, which was positioned outside of the squat rack. The use of weightlifting shoes was permitted, while the use of weightlifting straps was not. Finally, strong verbal encouragement was given to the subjects to ensure maximal effort during all repetitions. All JS repetitions were performed on a portable Kistler Quattro Jump force platform (Type 9290AD, Kistler, Winterthur, Switzerland) interfaced with a laptop computer. The sampling rate of the force platform was 500 Hz. The vertical ground-reaction-force data of the lifter-plus-bar system were directly measured by the force platform, and the raw force–time data were exported into a custom template created in Microsoft Excel (Microsoft Corp, Redmond, WA). The ground-reaction-force data were filtered using a digital low-pass Butterworth filter with a cutoff frequency of 10 Hz. The jump height during each JS repetition was based on the flight time of the center of mass of the lifter-plus-bar system using previously described methods.19 PFLand was identified as the greatest force value after the flight phase of the JS as indicated by the force–time curve. PE was calculated at the apex of the jump at each load.20

Statistical Analyses Intraclass correlation coefficients (ICCs) were used to examine the test–retest reliability of jump height and PFLand at each load examined. Pearson zero-order product–moment correlation coefficients (r) were calculated between the PE and PFLand at each load. Correlation values of .0, .1, .3, .5, .7, .9, and 1.0 were interpreted as trivial, small, moderate, large, very large, nearly perfect, and perfect, respectively, based on a previously established scale by Hopkins.21 A series of 1-way repeated-measures ANOVAs was used to examine the differences in jump height, PFLand, and PE in the JS exercise performed at the various loads examined (30%, 45%, 65%, and 80% 1RM HPC). Greenhouse-Geisser-adjusted values were reported if the assumption of sphericity was violated. Post hoc analyses were performed using the Bonferroni technique when necessary. Statistical power (c) of the main effect comparisons of jump height, PFLand, and PE was calculated. Effect sizes (d) and 95% confidence intervals (CI) for mean differences were calculated for all pairwise comparisons. Effect-size magnitudes were interpreted based on previous recommendations.21 The initial statistical significance level was set at .05; however a Holm-Bonferroni sequential adjustment was applied, as 3 separate repeated-measures ANOVAs were performed. All statistical analyses were performed using SPSS 22 (IBM, Armonk, NY).

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Results The ICC values for jump height and PFLand ranged from .94 to .95 and from .75 to .85, respectively, across all loads examined. Statistically significant relationships existed between PE and PFLand at loads of 65% (r = .576, P = .025) and 80% 1RM (r = .601, P = .018). However, the relationships between PE and PFLand were not statistically significant at 30% (r = .315, P = .252) and 45% 1RM (r = .268, P = .334). Descriptive jump-height, PFLand, and PE data at each load are displayed in Table 2. Statistically significant differences existed between loads for jump height (F1.557,21.793 = 294.488, P < .001, c = 1.00), PFLand (F3,42 = 4.143, P = .012, c = 0.82), and PE (F2.045,28.625 = 120.065, P < .001, c = 1.00). Post hoc analysis revealed that the JS jump height at 30% 1RM was statistically greater than the jump height produced at 45% (P < .001, d = 1.13, CI = 0.034–0.058), 65% (P < .001, d = 3.49, CI = 0.096–0.139), and 80% 1RM (P < .001, d = 5.06, CI = 0.136–0.187). In addition, the jump height at 45% 1RM was statistically greater than the jump height at 65% (P < .001, d = 2.75, CI = 0.054–0.088) and 80% 1RM (P < .001, d = 4.71, CI = 0.097–0.130). Finally, the jump height at 65% 1RM was statistically greater than the jump height at 80% 1RM (P < .001, d = 2.50, CI = 0.032–0.055). Similar to jump height, post hoc analysis of PE indicated that the PE at 30% 1RM was statistically greater than at 45% (P = .006, d = 0.33, CI = 5.012–34.530), 65% (P < .001, d = 0.96, CI = 35.736–82.501), and 80% 1RM (P < .001, d = 2.28, CI = 103.428–162.839). In addition, the PE at 45% 1RM was statistically greater than the PE at 65% (P = .002, d = 0.65, CI = 14.406–64.290) and 80% 1RM (P < .001, d = 2.00, CI = 90.181–136.544). Finally, the PE at 65% 1RM was statistically greater than at 80% 1RM (P < .001, d = 1.27, CI = 52.856–95.173). Although a statistically significant effect for PFLand was present, post hoc analysis revealed no statistically significant differences between the loads examined (P > .05). However, it should be noted that small effect sizes existed between 30% 1RM and 45% (d = 0.29) and 65% 1RM (d = 0.55), while a moderate effect size existed between 30% 1RM and 80% 1RM (d = 0.70). The frequency at which the greatest PFLand occurred at each load is displayed in Figure 1.

moderate and small relationships that existed between PE and the PFLand at 30% and 45% 1RM HPC, respectively, were not statistically significant. Statistically significant differences in jump height existed between all of the loads examined. Statistically significant differences in PFLand between the loads were identified; however, no statistically significant pairwise comparisons for PFLand were present. Statistically significant differences in PE existed between all of the loads examined. As expected, jump height decreased as the external load increased. The jump heights produced at 30% 1RM HPC were 17.4%, 56.4%, and 94.1% greater than the jump heights produced at 45%, 65%, and 80% 1RM HPC, respectively. These findings are consistent with literature that has examined the jump height produced at various loads for the jump-squat exercise.22–24 The JS may be the only weightlifting variant whose goal is to jump as high as possible, making it more ballistic in nature than other weightlifting movements.3,11,12,15 However, it is likely that the intent to jump as high as possible may contribute to the training stimulus produced.11,12,17 This is in comparison with other weightlifting derivatives whose goal is to either complete the triple extension movement (ie, clean/snatch pull, hang high pull, midthigh pull)17,25–27 or finish the lift by catching the bar (ie, clean and snatch).28,29 Because the training stimulus of weightlifting movements and their derivatives may be different,11–14,17 further research comparing these movements is suggested, as it may affect the prescription of specific exercises throughout the training year.

Discussion The current study examined how the external load affected the mechanics of the JS. The primary findings of this study are as follows. Large statistically significant relationships existed between PE and the PFLand at 65% and 80% 1RM HPC. In contrast, the

Figure 1 — Peak landing-force frequency at each load (N = 15). 1RM indicates 1-repetition maximum.

Table 2  Descriptive Jump Height, Peak Landing Forces, and Potential Energy During the Jump Shrug (N = 15), Mean ± SD Performance Variable Jump height (m)

Peak landing force (N)

Potential energy of the lifter-plus-bar system (J)

30%

Load (% 1RM HPC)

0.25 ± 0.04a,b,c

4770.8 ± 488.5

293.5 ± 61.8a,b,e

45%

0.21 ±

0.03a,b

4586.0 ± 774.7

273.7 ± 58.7a,d

65%

0.14 ± 0.02a

4380.4 ± 868.4

234.4 ± 61.2a

80%

0.09 ± 0.02

4201.8 ± 1034.9

160.4 ± 54.7

Abbreviation: 1RM HPC, 1-repetition-maximum hang power clean. a Statistically greater than value at 80% 1RM HPC at P < .001 level. b Statistically greater than value at 65% 1RM HPC at P < .001 level. c Statistically greater than value at 45% 1RM HPC at P < .001 level. d Statistically greater than value at 65% 1RM HPC at P < .01 level. e Statistically greater than value at 45% 1RM HPC at P < .01 level. IJSPP Vol. 11, No. 1, 2016

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64  Suchomel, Taber, and Wright

A statistically significant main effect existed between loads for PFLand; however, no statistically significant pairwise comparisons were present. The lack of statistical significance is likely due to the large standard deviations of the PFLand at each load and multiple post hoc comparisons completed with a Bonferroni-adjusted P value. It should be noted that practical significance for PFLand existed, as small effect sizes existed between 30% 1RM HPC and 45% (d = 0.29) and 65% 1RM HPC (d = 0.55), and a moderate effect size existed between 30% 1RM HPC and 80% 1RM HPC (d = 0.70). The greatest PFLand was produced at 30% 1RM HPC and was followed in order by 45%, 65%, and 80% 1RM HPC. The PFLand produced at 30% 1RM HPC was 4.0%, 8.5%, and 12.7% greater than the PFLand values at 45%, 65%, and 80% 1RM HPC, respectively. This is the first study to examine the PFLand of the JS exercise. A potential concern of practitioners who may be considering prescribing heavier loads with the JS exercise are the impact forces on landing. The results of this study indicate that the JS exercise may not be limited by the external load prescribed. In fact, the decreasing PFLand that occurs with increasing loads may allow for the prescription of higher loads, which if implemented with a ballistic movement may lead to peak-force and rate-of-force-production adaptations.17,30,31 Only 1 other study has examined the landing/impact phase of weightlifting movements,18 and the results indicated that more lower-extremity work was performed during the drop landing and the clean landing than during the jump landing. In addition, the work performed during the clean landing was statistically greater than during the power-clean landing. Although the previous study did not compare the PFLand at different loads during the clean and power clean, it should be noted that the authors of that study instructed their subjects to absorb the landing during the jump and drop landings, while no additional instruction was given for the clean and power clean. The findings of the previous study are similar to those of the current study as they may relate to the landing strategy used by each subject (eg, landing with stiff legs or absorbing the landing with increased joint flexion). The PEs achieved at 30% 1RM HPC were 7.0%, 22.4%, and 58.6% greater than the PEs at 45%, 65%, and 80% 1RM HPC, respectively. Based on the calculation of PE, the lifter-plus-bar system realizes its greatest PE at the greatest jump height achieved, assuming that the mass of system stays constant.20 In this light, the PE should also be related to the PFLand because there will be more time for gravitational acceleration to act on the lifter-plusbar system, leading to a greater impulse being needed to bring the momentum of the system (ie, lifter plus bar) to zero on landing. Our results indicated that moderate and small relationships21 existed between PE and PFLand at 30% and 45% 1RM HPC, respectively. In contrast, strong relationships21 existed between PE and PFLand at the heavier loads of 65% and 80% 1RM HPC. These findings may indicate that the PFLand at lighter loads may be more attributable to other factors such as the landing strategy used by the subjects. In contrast, the lower PFLand with heavier loads may be more attributable to lower jump height and therefore lower PE. The landing strategy used during the JS may be a primary determinant of the PFLand, especially at lighter loads. All subjects in this study practiced the JS during the familiarization session, but they were not provided with any more instruction on how best to land. Because this is the first study to examine the landing forces of the JS, we did not attempt to control the PFLand by providing additional instruction and feedback, which has been shown to affect landing-

force magnitude.32,33 The landing position of the JS is unique due to the barbell being in the midthigh position. It is unknown whether the landing position and the subsequent movement of the athlete during the JS will increase or decrease the PFLand as compared with other landing positions. Although it was outside of the scope of this study, future research may consider investigating the landing strategies used by subjects during the JS, specifically focusing on spine, hip, knee, and ankle kinetic and kinematic characteristics, especially with varying loads. The findings of this study are important to practitioners who prescribe or may prescribe the JS. We found that the greatest jump height, PFLand, and PE occurred at the lightest load of 30% 1RM HPC. These findings are consistent with previous literature on the JS that indicated that the greatest peak power, velocity, and velocity at peak power occur at 30% 1RM HPC3,11 and that the greatest joint velocities occurred at the lightest load examined in another study.12 However, one must consider the benefits of decreased landing forces at higher loads. For example, if a practitioner wants to use the JS during a strength or strength–power training block in which the prescribed loads are high, it appears that the JS would not be limited by the PFLand produced. Thus, practitioners may be able to prescribe higher loads with the JS if the primary training goals are to improve peak force and rate of force production during the concentric (propulsive) phase of the movement. However, practitioners should note that 2 previous studies3,11 have indicated that the technique of the propulsive phase of the JS may break down at loads greater than 65% 1RM HPC. It is possible that the subjects of the previous studies did not fully extend their hips during the second pull phase due to the heavier load. However, we admit that this is speculation, as no kinematic data were presented in the previous studies.

Practical Applications It is recommended that practitioners implement loads of approximately 30% of an individual’s 1RM HPC for the JS exercise to produce the greatest peak power, velocity, and velocity at peak power stimulus. However, practitioners may prescribe the JS with heavier loads (ie, 65% or 80% 1RM HPC) without viewing PFLand as a limitation. The combination of the ballistic nature of the JS and heavier loads may then lead to enhanced peak-force and rateof-force-production adaptations.17,30

Conclusions In conclusion, JS jump height, PFLand, and PE were the greatest at 30% 1RM HPC and decreased as the external load increased. Increases in loading during the JS appear to have a large effect on the jump height and PE achieved during the exercise but a smaller influence on PFLand. Practitioners may prescribe the JS at heavier loads without viewing PFLand as a limitation of the exercise. Acknowledgments The results of this study do not constitute endorsement of the product by the authors or the journal. There are no conflicts of interest. There are no professional relationships with companies or manufacturers who will benefit from the results of the current study for any author.

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References 1. Suchomel TJ, Beckham GK, Wright GA. The impact of load on lower body performance variables during the hang power clean. Sports Biomech. 2014;13(1):87–95. PubMed doi:10.1080/14763141.2013. 861012 2. Suchomel TJ, Beckham GK, Wright GA. Effect of various loads on the force–time characteristics of the hang high pull. J Strength Cond Res. 2015;29(5):1295–1301. PubMed 3. Suchomel TJ, Beckham GK, Wright GA. Lower body kinetics during the jump shrug: impact of load. J Trainol. 2013;2:19–22. doi:10.17338/ trainology.2.2_19 4. Comfort P, Udall R, Jones PA. The effect of loading on kinematic and kinetic variables during the midthigh clean pull. J Strength Cond Res. 2012;26(5):1208–1214. PubMed doi:10.1519/JSC.0b013e3182510827n 5. Kawamori N, Rossi SJ, Justice BD, et al. Peak force and rate of force development during isometric and dynamic mid-thigh clean pulls performed at various intensities. J Strength Cond Res. 2006;20(3):483– 491. PubMed 6. Comfort P, Fletcher C, McMahon JJ. Determination of optimal loading during the power clean, in collegiate athletes. J Strength Cond Res. 2012;26(11):2970–2974. PubMed doi:10.1519/ JSC.0b013e318245bed4 7. Kawamori N, Crum AJ, Blumert PA, et al. Influence of different relative intensities on power output during the hang power clean: identification of the optimal load. J Strength Cond Res. 2005;19(3):698–708. PubMed 8. Kilduff LP, Bevan H, Owen N, et al. Optimal loading for peak power output during the hang power clean in professional rugby players. Int J Sports Physiol Perform. 2007;2(3):260–269. PubMed 9. Cormie P, McCaulley GO, Triplett NT, McBride JM. Optimal loading for maximal power output during lower-body resistance exercises. Med Sci Sports Exerc. 2007;39(2):340–349. PubMed doi:10.1249/01. mss.0000246993.71599.bf 10. Cormie P, McBride JM, McCaulley GO. Validation of power measurement techniques in dynamic lower body resistance exercises. J Appl Biomech. 2007;23(2):103–118. PubMed 11. Suchomel TJ, Wright GA, Kernozek TW, Kline DE. Kinetic comparison of the power development between power clean variations. J Strength Cond Res. 2014;28(2):350–360. PubMed doi:10.1519/ JSC.0b013e31829a36a3 12. Suchomel TJ, Wright GA, Lottig J. Lower extremity joint velocity comparisons during the hang power clean and jump shrug at various loads. Paper presented at: XXXIInd International Conference of Biomechanics in Sports; July 2014; Johnson City, TN. 13. Comfort P, Allen M, Graham-Smith P. Kinetic comparisons during variations of the power clean. J Strength Cond Res. 2011;25(12):3269– 3273. PubMed doi:10.1519/JSC.0b013e3182184dea 14. Comfort P, Allen M, Graham-Smith P. Comparisons of peak ground reaction force and rate of force development during variations of the power clean. J Strength Cond Res. 2011;25(5):1235–1239. PubMed doi:10.1519/JSC.0b013e3181d6dc0d 15. Suchomel TJ, DeWeese BH, Beckham GK, Serrano AJ, Sole CJ. The jump shrug: A progressive exercise into weightlifting derivatives. Strength Cond J. 2014;36(3):43–47. doi:10.1519/ SSC.0000000000000064

16. Suchomel TJ, Sato K. Baseball resistance training: should power clean variations be incorporated? J Athl Enhanc. 2013;2(2). doi:10.4172/2324-9080.1000112 17. Suchomel TJ, Comfort P, Stone MH. Weightlifting pulling derivatives: rationale for implementation and application. Sports Med. 2015;45(6):823–839. PubMed doi:10.1007/s40279-015-0314-y 18. Moolyk AN, Carey JP, Chiu LZF. Characteristics of lower extremity work during the impact phase of jumping and weightlifting. J Strength Cond Res. 2013;27(12):3225–3232. PubMed doi:10.1519/ JSC.0b013e31828ddf19 19. Linthorne NP. Analysis of standing vertical jumps using a force platform. Am J Phys. 2001;69(11):1198–1204. doi:10.1119/1.1397460 20. Hamill J, Knutzen KM. Linear Kinetics. Biomechanical Basis of Human Movement. 3rd ed. Baltimore, MD: Lippincott Williams & Wilkins; 2009:367–410. 21. Hopkins WG. A scale of magnitude for effect statistics. 2014. http:// sportsci.org/resource/stats/effectmag.html. 22. Dayne AM, McBride JM, Nuzzo JL, Triplett NT, Skinner J, Burr A. Power output in the jump squat in adolescent male athletes. J Strength Cond Res. 2011;25(3):585–589. PubMed doi:10.1519/ JSC.0b013e3181c1fa83 23. McBride JM, Triplett-McBride T, Davie A, Newton RU. A comparison of strength and power characteristics between power lifters, Olympic lifters, and sprinters. J Strength Cond Res. 1999;13(1):58–66. 24. Cormie P, McBride JM, McCaulley GO. Power–time, force–time, and velocity–time curve analysis during the jump squat: impact of load. J Appl Biomech. 2008;24(2):112–120. PubMed 25. DeWeese BH, Serrano AJ, Scruggs SK, Sams ML. The clean pull and snatch pull: proper technique for weightlifting movement derivatives. Strength Cond J. 2012;34(6):82–86. doi:10.1519/ SSC.0b013e31826f1023 26. Suchomel TJ, DeWeese BH, Beckham GK, Serrano AJ, French SM. The hang high pull: a progressive exercise into weightlifting derivatives. Strength Cond J. 2014;36(6):79–83. doi:10.1519/ SSC.0000000000000089 27. DeWeese BH, Serrano AJ, Scruggs SK, Burton JD. The midthigh pull: proper application and progressions of a weightlifting movement derivative. Strength Cond J. 2013;35(6):54–58. doi:10.1519/ SSC.0b013e318297c77b 28. Garhammer J. Power clean: kinesiological evaluation. Strength Cond J. 1984;6(3):40, 61–63. 29. Frolov VI, Lellikov SI, Efimov NM, Vanagas MP. Snatch technique of top-class weight-lifters. Sov Sports Rev. 1979;14:24–29. 30. Haff GG, Nimphius S. Training principles for power. Strength Cond J. 2012;34(6):2–12. doi:10.1519/SSC.0b013e31826db467 31. Harris GR, Stone MH, O’Bryant HS, Proulx CM, Johnson RL. Short-term performance effects of high power, high force, or combined weight-training methods. J Strength Cond Res. 2000;14(1):14–20. 32. Onate JA, Guskiewicz KM, Sullivan RJ. Augmented feedback reduces jump landing forces. J Orthop Sports Phys Ther. 2001;31(9):511–517. PubMed doi:10.2519/jospt.2001.31.9.511 33. McNair PJ, Prapavessis H, Callender K. Decreasing landing forces: effect of instruction. Br J Sports Med. 2000;34(4):293–296. PubMed doi:10.1136/bjsm.34.4.293

IJSPP Vol. 11, No. 1, 2016

Jump Shrug Height and Landing Forces Across Various Loads.

The purpose of this study was to examine the effect that load has on the mechanics of the jump shrug. Fifteen track and field and club/intramural athl...
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