Effects of run-up velocity on performance, kinematics, and energy exchanges in the pole vault

1. Effects of run-up velocity on performance, kinematics, and energy exchanges in the pole vault Linthorne and Weetman Corey, Betsy, Maria, Steve, Eric

2. Purpose • This study examined the effect of run-up velocity on the peak height achieved by the athlete in the pole vault and on the corresponding changes in the athlete’s kinematics and energy exchanges. • Hypothesis: a faster run-up allows the athlete to grip higher on a longer and stiffer pole and hence achieve a higher vault

3. Purpose • Aims of the study: • Determine the mathematical form and sensitivity of the relationship between run-up velocity and vault height • Determine the changes in the athlete’s kinematics and the changes in the pole characteristics that are necessary • Determine the resulting changes in the patterns of energy exchange that occur during the vault

4. Methods • An experienced male pole vaulter volunteered • Jumps conducted in still air conditions • Performed 17 jumps for max height using a run-up length of 2,4,6,8,12, and 16 steps • Order of the steps were random • Unlimited rest to minimize fatigue • Self-selected his pole, and grip height • Video analysis was used to obtain kinematic measures • Field of view was zoomed to allow the athlete to be visible in the last two steps of the take-off and throughout the vault

5. Methods • Performance variables measured: • Peak height, grip height, push height • Kinematic variables measured: • Velocity, height, and direction of travel of the athlete’s center of mass • Angle of the leg and knee of the athlete’s take-off leg, and pole angle and chord length • Energy variables measured: • Kinetic energy, gravitational potential energy, and total mechanical energy of the athlete • Noted: • Touchdown, pole grounding and bend, take-off, jump peak

6. Results • Run-up velocity of the athlete increased with increasing run-up length • The athlete’s resultant take-off velocity increased with increasing run-up velocity • The athlete’s total mechanical energy at touchdown, take-off, and peak increased with increasing run-up velocity • All of this was achieved through a combination of a greater grip height and a greater push height

7. Results • What does this mean? • Keeping in mind that the athlete made minor systematic changes to everything as the run-up velocity increased: • A faster run-up produced a greater loss of energy during the take-off, but this loss was not sufficient to negate the increase in run-up velocity and the increase of muscular work performed during the pole support phase • Therefore, the athlete always had a net energy gain during the vault

8. Construct Validity • Dependent (Effect)-Peak Height • Operationalization: 17 jumps for maximum height utilizing video analysis • Independent (Cause)-Run-up velocity • Operationalization: Setting the length of the participants run up at 2, 4, 6, 8, and 12 steps (competition run-up length) • Self-selected combination pole length, pole stiffness and, grip height

9. Construct Validity • Translational ‘Face’ Validity • The study appears to have good face validity in that previous similar studies that have improved our understanding of the optimum technique for high jump and long jump • Pole vault runway, takeoff box, upright and landing mats complied with IAAF regulations for pole vault competitions • Video analysis seems like the only way to take accurate measures

10. Construct Validity • Changing speed of movement due to variation of distance should have an affect on jump height • Stiffer/longer poles should respond differently • Positioning of the pole should also have an effect

11. Construct Validity • However, • There is only 1 subject • Multiple subjects would provide more validity and reliability by providing more data • We are also not informed if these 17 jumps were completed in sequence • Unlimited rest interval? • What does that mean? Why leave it to them? • More structure rest interval would ensure maximal output • What is the significance of performing 17 trials? • A set # of trials at each run-up length would provide more consistent results • Why allow the subject to self select variables? • Wouldn’t it be better to keep variables structured

12. External Validity • Sampling Strategy? • Nonprobability Sampling • Purposive (Only 1 experienced male pole vaulter was used, so they were sampling with a purpose in mind.) • Convenience Sampling(This is due to the fact that they tested a volunteer to was conveniently available.)

13. External Validity • Population being generalized to: • Competitive pole vaulters (athletes) • The authors of this study do realize that only testing one male experienced pole vaulter makes if difficult to generalize to all pole vaulters. It may be especially hard to generalize to females as well since no females were tested.

14. External Validity • Population: • It is not stated what age group or what level of competitiveness they are trying to generalize to due to the fact that information wasn’t presented in the article.

15. External Validity • Time and Setting: • It seems as though the researchers are trying to generalize to pole vaulting athletes across all times. • The generalized setting is within a controlled inside atmosphere, so it would make it more difficult to generalize to athletes who vault outside. The outside environment could potentially have an effect on run-up velocity.

16. External Validity • The sampling strategy implies that it may be difficult to generalize to other pole vaulters, especially that of the female population. • At this point I don’t see any other mismatches when it comes to time. • A possible mismatch with setting could be the fact that it took place in a controlled environment, and not all athletes compete in an inside environment.

17. External Validity • The problem with the generalization of this study is the fact that only one male experienced pole vaulter was used. Though this could potentially bring potential problems when generalizing to a wider range of pole vaulters. That being said, I still it still seems as though there is a good match with the relationship under investigation. The authors state, “Training data from other male pole vaulters suggests that the results from the athlete in the present study are representative of skilled vaulters.”

18. Internal Validity • Cause and effect: does changing the run up velocity change the grip height, vault height (and change kinematics, pole characteristics, and energy exchange patterns)? • Simple answer: • on the face of it, yes

19. Internal Validity • Not so simple answer: it’s a little more than that, but I still think the study holds up. • Many things happening • its more complicated than ‘run faster go higher’

20. Internal Validity • Just because the athlete is making many other changes, that doesn’t necessarily mean there is no validity, but it is certainly not direct causality. • Might be a chain reaction, but still connected; would he make the other mechanical changes at slower run speeds? Could he?

21. Internal Validity • Largest threat is due to there only being one subject • They cite other athletes’ ‘training data’ with similar results to increase their sample size (not by much though)

22. Internal Validity • What exactly is ‘training data’? • Still no real ‘control’ group, or for that matter, multiple groups (depending on the other study)

23. Internal Validity • Bottom Line: Plausible although through a chain of events rather than direct causality • Have a serious problem with there only being one person in the study, even though the results do seem plausible.