Effect of Acute Dynamic and Static Stretching on Maximal Muscular Power in a Sample of College Age Recreational Athletes by Jeffrey Christopher Murphy B.S. Psychology, Saint Vincent College, 1994 M.S. Exercise Physiology, University of Pittsburgh, 2003 Submitted to the Graduate Faculty of Health and Physical Activity in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Exercise Physiology University of Pittsburgh 2008 UNIVERSITY OF PITTSBURGH [SCHOOL OF EDUCATION] This dissertation was presented by Jeffrey Christopher Murphy It was defended on July 28, 2008 and approved by Robert Robertson, Ph.D., Professor, HPA] Jean McCrory, Ph. D., Research Assistant Professor, HPA Ray Burdett, Ph. D., Associate Professor, HRS Dissertation Advisor: Elizabeth Nagle, Ph. D., Assistant Professor, HPA ii Copyright © by Jeffrey Christopher Murphy 2008 iii EFFECT OF ACUTE DYNAMIC AND STATIC STRETCHING ON MAXIMAL MUSCULAR POWER IN A SAMPLE OF COLLEGE AGE RECREATIONAL ATHLETES Jeffrey Christopher Murphy, Ph.D. University of Pittsburgh, [2008] The purpose of the study was to determine the effect of dynamic and static stretching on muscular peak power production and hip and knee range of motion in a sample of college age recreational males. Forty-two males (aged 18-24) healthy, physically active volunteers from a University of Pittsburgh physical education class participated as subjects in this investigation. Subjects performed pre and post test measures of sit and reach, hip and knee goniometry measures, and vertical jump test. A one repetition maximum leg press was performed prior to pre-tests to determine group differences in strength. Subjects were randomly assigned to one of three stretch groups (dynamic, static, and control). All subjects began with a five minute warm- up on an upright cycle that elevated the heart rate to 110 beats per minute. Following the warm- up period, subjects immediately began their stretching program (dynamic or static), or remained seated for 12 minutes. A one-way ANOVA was conducted to detect group differences in strength levels conducted during pre-tests. A 3x2 factorial ANOVA was conducted to determine between and within group differences in treatment groups. Statistical significance was set at α = 0.05. Results of the investigation showed significant time effects for all dependent measures (p < 0.05). Significant time x treatment interactions were found for maximum jump height, maximum peak power, and sit and reach in the DS and SS + DS groups, respectively (p < 0.05). However, there was no time x treatment interactions for mean jump height, mean peak power, knee range of motion, or hip range of motion. The results of the present study suggest that static iv and dynamic stretching for 20 seconds prior to a vertical jump can improve mean vertical jump height, mean peak power, and hip and knee range of motion in a sample of male college age recreational athletes. Future research is needed to investigate the effect of intensity of stretch on force production, and the relationship between stretch intensity and duration on force production to establish a dose-response relationship between stretching and its effect on force production. v TABLE OF CONTENTS PREFACE .................................................................................................................................. XII 1.0 INTRODUCTION ........................................................................................................ 1 1.1 Statement of problem ............................................................................................. 4 1.2 Hypothesis ............................................................................................................. 4 2.0 LITERATURE REVIEW ............................................................................................ 5 2.1 Introduction ............................................................................................................ 5 2.2 Rationale for Stretching with an Active Warm-up ................................................ 7 2.3 Stretching Methods ................................................................................................ 9 2.3.1 Static Stretching Methods ................................................................................ 10 2.3.2 Acute Affects of Static Passive Stretching on Temperature and Elasticity ..... 12 2.3.3 Force Decrements Associated with Passive Static Stretching ......................... 13 2.3.4 Effects of Passive Static Stretching on Power ................................................. 15 2.3.5 Dynamic Stretching Methods .......................................................................... 16 2.3.6 Acute Affects of Active Dynamic Stretching on Temperature and Elasticity 17 2.3.7 Active Dynamic Stretch and Power ................................................................. 19 2.4 Relationship Between Power and Vertical Jump Performance ........................... 20 2.5 Measurements of Power and Jump Height During the Vertical Jump ................ 21 2.5.1 Laboratory Measures of Muscular Power and Jump Height ........................... 22 vi 2.5.2 Field Measures of Muscular Power and Jump Height ..................................... 23 2.6 Factors that Influence Vertical Jump Performance ............................................. 25 2.6.1 Effect of Muscle Mass and Strength on Vertical Jump Performance.............. 25 2.6.2 Training Status and Vertical Jump Performance ............................................. 27 2.6.3 Stretch Shortening Cycle and Vertical Jump Performance ............................. 28 2.7 Conclusions.......................................................................................................... 29 3.0 METHODS .................................................................................................................. 31 3.1 Experimental Design ........................................................................................... 31 3.2 Subjects ................................................................................................................ 31 3.3 Procedures ............................................................................................................ 32 3.3.1 Day 1................................................................................................................ 33 3.3.1.1 Overview of Study ................................................................................ 33 3.3.1.2 Anthropometrics.................................................................................... 34 3.3.1.3 Leg Press Test to Assess Maximal Strength ......................................... 34 3.3.1.4 Pretreatment Assessments ..................................................................... 35 3.3.1.5 Orientation Practice Session ................................................................. 38 3.3.2 Day 2................................................................................................................ 42 3.4 Statistical Analysis ............................................................................................... 43 4.0 RESULTS .................................................................................................................... 44 4.1 Descriptive Statistics ........................................................................................... 45 4.2 1RM Leg Press Strength ...................................................................................... 47 4.3 Dependent Measures ............................................................................................ 50 4.3.1 Observed Trends for Mean Vertical Jump Height and Peak Power ................ 52 vii 4.3.2 Observed Trends for Maximum Vertical Jump Height and Peak Power ........ 54 4.3.3 Observed Trends in Goniometric Measurements ............................................ 57 4.3.4 Observed Trends for Sit and Reach ................................................................. 59 4.4 Intraclass Reliability ............................................................................................ 60 4.5 Summary .............................................................................................................. 60 5.0 DISCUSSION .............................................................................................................. 61 5.1 Stretching and Maximal Muscular Power ........................................................... 62 5.2 Range of Motion and Maximal Muscular Power ................................................ 66 5.3 Limitations ........................................................................................................... 68 5.4 Recommendations for Future Research ............................................................... 71 5.5 Conclusions.......................................................................................................... 74 APPENDIX A .............................................................................................................................. 75 APPENDIX B .............................................................................................................................. 77 APPENDIX C .............................................................................................................................. 79 APPENDIX D .............................................................................................................................. 85 BIBLIOGRAPHY ....................................................................................................................... 97 viii LIST OF TABLES Table 1. Descriptive Statistics on Age, Weight, and Height. ....................................................... 45 Table 2. Descriptive Statistics on Percent Body Fat and Fat Free Mass ...................................... 46 Table 3. Pre-Assessment Leg Press. ............................................................................................. 47 Table 4. Means + SD for dependent variables. ............................................................................. 51 Table 5. Maximum for jump height and peak power + SD .......................................................... 54 ix LIST OF FIGURES Figure 1 One-way ANOVA for relative 1RM leg press strength. ................................................ 48 Figure 2. One-way ANOVA for absolute 1RM leg press strength. .............................................. 49 Figure 3. Change in mean vertical jump height pre and post test. ................................................ 52 Figure 4. Change in mean peak power pre and post test .............................................................. 53 Figure 5. Change in maximum jump height pre and post test ...................................................... 55 Figure 6. Change in maximum peak power pre and post ............................................................. 56 Figure 7. Change in Hip ROM pre to post. ................................................................................... 57 Figure 8. Change in Knee ROM pre to post. ................................................................................ 58 Figure 9. Change in sit and reach pre to post. ............................................................................... 59 Figure 10. Supine hip flexion with bent leg. ................................................................................. 79 Figure 11. Supine hip flexion with straight leg............................................................................. 79 Figure 12. Prone knee flexion. ...................................................................................................... 80 Figure 13. Lunge with knee on floor. ........................................................................................... 80 Figure 14. Supine dorsiflexion with cord. .................................................................................... 81 Figure 15. Standing hip flexion with bent knee. ........................................................................... 81 Figure 16. Standing hip flexion with straight leg. ........................................................................ 82 Figure 17. Standing knee flexion. ................................................................................................. 82 Figure 18. Standing lunge. ............................................................................................................ 83 x