THE EFFECTS OF CLEAN AND JERK RACK POSITION TIME ON SUBSEQUENT JERK KINETICS A Thesis Presented to the Faculty of California State Polytechnic University, Pomona In Partial Fulfillment Of the Requirements for the Degree Master of Science In Kinesiology By Matthew R. Rodriguez 2019 SIGNATURE PAGE THESIS: THE EFFECTS OF CLEAN AND JERK RACK POSITION TIME ON SUBSEQUENT JERK KINETICS AUTHOR: Matthew R. Rodriguez DATE SUBMITTED: Spring 2019 Department of Kinesiology and Health Promotion Dr. Edward Jo ______________________________ Thesis Committee Chair Kinesiology and Health Promotion Dr. Ken Hansen Kinesiology and Health Promotion Dr. Marcus Elam Nutrition and Food Sciences ii iii ABSTRACT In the sport of Olympic weightlifting, athletes typically select their preferred rack position time (RPT) for the clean and jerk (CJ). Prior to this study, there has been a lack of scientific inquiry into the effects of RPT on jerk kinetics and overall CJ performance. Thus, the purpose of this study was to examine the effects of RPT during the CJ on subsequent jerk power, force, and velocity in trained Olympic weightlifters. Twenty (n=20) trained males participated in this crossover design study. Subjects completed four RPT condition: 4s, 8s, 12s, and self-selected RPT across two separate visits (2 RPT conditions per visit). During each RPT condition the CJ was performed using 80% of their pre-determined one repetition maximum. Kinetic measures were acquired during the jerk portion of the lift following the RPT using a linear position transducer. There was no main effect for condition (self-selected vs. 4s, vs. 8s, vs. 12s RPT) for peak power (p=0.37), average power (p=0.35), peak velocity (p=0.92), average velocity (p=0.78), or peak force (p=0.08). There was no significant interaction of relative strength and RPT condition for peak power (p=0.23), average power (p=0.86), peak velocity (p=0.52), average velocity (p=0.47), or peak force (p=0.05). Specifically, subjects with relative 1RM strength below the average (1.21 kg/kg) exhibited no difference in all dependent variables among the RPT conditions. Similarly, subjects with relative 1RM strength above the average demonstrated no difference in all dependent variables among each of the RPT conditions. There was also no significant interaction of limb lengths and RPT condition for all dependent variables. In conclusion, there was no effect of RPT whether pre-determined at varying timeframes or self-selected on subsequent jerk kinetics although trends indicated the lowest kinetic output during the jerk with 12s RPT and iii power and velocity maximized with 8s RPT. Also, peak force, on average, was greatest during the self-selected RPT which was less than 4s. iv TABLE OF CONTENTS Signature Page .............................................................................................................. ii Abstract ......................................................................................................................... iii List of Figure................................................................................................................. vii List of Tables ................................................................................................................ viii Chapter 1: Introduction ................................................................................................. 1 Statement of the Problem .................................................................................. 2 Purpose Statement ............................................................................................. 2 Significance of the Study .................................................................................. 2 Specific Aims .................................................................................................... 2 Hypothesis......................................................................................................... 3 Limitations ........................................................................................................ 3 Delimitations ..................................................................................................... 3 Operational Definitions ..................................................................................... 3 Chapter 2: Literature Review ........................................................................................ 5 Olympic Weightlifting Introduction ................................................................. 5 Biomechanics of Weightlifting ......................................................................... 7 Physiology of Weightlifting .............................................................................. 8 Clean and Jerk Performance ............................................................................. 10 Clean and Jerk Technique Research ................................................................. 11 Chapter 3: Methodology ............................................................................................... 13 Experimental Design ......................................................................................... 13 Participants ........................................................................................................ 14 Experimental Clean and Jerk Conditions .......................................................... 15 v Laboratory Testing Procedures ......................................................................... 15 Clean and Jerk Maximal Strength ......................................................... 15 Jerk Movement Kinetics ....................................................................... 16 Analysis of Data ................................................................................................ 16 Chapter 4: Results ......................................................................................................... 17 Chapter 5: Discussion ................................................................................................... 22 References ......................................................................................................... 27 vi LIST OF FIGURES Figure 1 Jerk Peak Power for each Rack Position Time Condition .......................... 19 Figure 2 Jerk Average Power for each Rack Position Time Condition .................... 19 Figure 3 Jerk Peak Velocity for each Rack Position Time Condition....................... 20 Figure 4 Jerk Average Velocity for each Rack Position Time Condition ................. 20 Figure 5 Jerk Peak Force for each Rack Position Time Condition ........................... 21 Figure 6 Average scores of each kinetic variable during the jerk for each RPT condition ..................................................................................................................... 25 vii LIST OF TABLES Table 1 Jerk Kinetic Measurements per Rack Position Time Condition for Total Group and Relative Strength Groups ....................................................................................... 18 viii CHAPTER ONE Introduction The sport of Olympic weightlifting has undergone changes at the national and international levels to conform to the regulatory requirements stipulated by the International Olympic Committee (IOC), which include more stringent doping policies. With an increase of “clean” elite lifters competing on the international platform, greater emphasis must be placed on evidence-based training and development of optimal technique and biomechanics. The current body of empirical knowledge has provided coaches, both internationally and domestically, with training and biomechanical principles to apply towards the optimization of their athletes’ performance. However, there are certainly gaps that need to be filled to further progress towards success, especially in U.S. weightlifters. The sport of weightlifting presents itself with an immense physical challenge for the athlete in the execution of the Olympic lifts, the snatch and clean and jerk (CJ). They require unique development of various strength attributes such as power, force, velocity, and maximum strength while improving lifting technique and biomechanics. Thus, a body of sport science research has been dedicated to the optimization of weightlifting performance by investigating unique training methodologies and manipulating the biomechanical and physiological properties of the lifts. Regarding the latter, no prior investigation, at least to current knowledge, has examined the influence of CJ rack position time (RPT) following the clean on subsequent power output during the jerk portion. Power output can be argued as to be the determinant of jerk performance and thereby successful CJ execution. The importance of the jerk regarding competition 1 success cannot be understated; it is the last part of the second phase of competition to be completed (i.e. CJ). Championships are determined by this last phase of competition. Therefore, research that focuses on the jerk is significant to optimize training and competition performance. Statement of the Problem The appropriate selection of RPT may be unclear to coaches because the data are not yet available. It remains unknown whether RPT influences jerk performance and if self-selected RPT is more effective than pre-determined RPT. Purpose Statement The purpose of this study was to examine the effects of clean and jerk rack position hold time on subsequent jerk power, force, and velocity in trained Olympic weightlifters.