Sunday, October 12, 2008

Velocity and Power Data: Monday Morning Geekout

Here's the velocity data from the lifters profiled in my 10/5-6 posts. What do you think? Same weight on the bar with the same outcome: good lift--but accomplished via different styles.

Sage has a max velocity of 1.48 m/s at a bar height of .76 meters. This corresponds to 1167 W max power and 18.8 W/kg.

Shannon has a max velocity of 1.79 m/s at a bar height of .68 meters. This corresponds to max power of 1402 W and 22.46 W/kg.


video

4 comments:

Anonymous said...

Requiring less force/power for the same weight suggests that style is more efficient and will ultimately yield higher weights. But nothing succeeds like success.

Orie said...

Cool stuff!

Will the taller lifter (assuming similar skill and athleticism) always tend to have higher velocity and power when lifting the same load?

Kristof said...

"Requiring less force/power for the same weight suggests that style is more efficient" ... True ... if we assume that the displacement (in this case the bar path) and the top of the pull are the same. From the Dartfish data is does look like the girls' maximum vertical height is similar. So, it would appear that Sage is 'more efficient'.

Other things to notice are:
1. Sage achieves her max bar velocity 8cm higher than Shannon (this may be due to anthropometric differences), yet both girls reach almost the same ultimate vertical height (1cm diff.). So, Shannon's bar is actually drifting more, which is kind of opposite of what I thought based on the video alone. Goes to show you that you really need the kinematics/kinetics.

2. Slope of the velocity curve during the first pull is steeper for Sage than Shannon which indicates that Sage is exerting more force, which is why she also reaches a higher velocity during the first pull.

3. The trend in slopes in 2. is reversed during the second pull. Meaning, that Shannon exerts more force during this phase.

4. The dip in Sage's velocity profile indicates that the barbell is experiencing a braking period (which in itself could be considered 'inefficient').

Overall, Sage's arms appears to pull very fast off of the floor, but applying less force during the second pull (when you really need it). Probably has to do with her arms bending. Again, the trend is reversed for Shannon. However, it appears that Shannon reaches a max velocity that is way to high. Energetically, she should aim to utilize that extra velocity and transfer it to more weight on the bar. Bottom line, two great girls who both appear to have at least some more reserve in performance.

Chris said...

I'm curious how you're calculating power without having kinetic data?

If I'm not mistaken, power = work/time

work = force x displacement

or

power = force x velocity

While you collected the kinematic variables, how can you justify your force measurements? Are you just calculating in their body mass alone?