Monday, January 12, 2009


Before I post, I must apologize to Vinny. He hates when I bust out the chalk and start up with the math equations on the blackboard...

So I tried to compare some performances between two participants during a WO. Several variables quickly arose... weight of kettlebell, height of participant (and hence overhead reach), time, and number of repetitions.  Each of these can easily be converted into the proper units of measure to compare Work (or in this case Power).

Luckily, each participant did the WO for the same time (20 minutes).  That makes differences in Power and Work directly proportionate. But for the sake of future experiments, I converted the results to Power instead of Work. Here is the difference:
  • Work measures the amount of energy, as a function of Mass, Acceleration, and Displacement.. (Force and Distance).
  • Power measures the Work with respect to Time.

Here is an example: Weightlifter 1 and 2 are the same height. They both lift 100 pounds from the ground to overhead. They each do this ten times.  Weightlifter 1 does it in ten seconds. Weightlifter 2 does it in 15 seconds.  Both weightlifters do the SAME amount of Work. However, Weightlifter 1 is more powerful because he did the same work in less time.

My scenario:  
  • Different KB weights
  • Different heights
  • Different bodyweights
  • Different repetition numbers
  • Same time limit
The Power formula was used to calculate which participant was more powerful (and since the time limit was equal, whichever participant did more Work, was also more Powerful). The movement was kettlebell clean-and-press, with total repetitions in 20 minutes. Participants had displacements of 75 and 78 inches (from floor to bottom of KB at top of press), KB weights of 55# and 50#, performed 122 and 182 repetitions, respectively.  The questions raised: 
  • Could the participant with the shorter reach AND fewer repetitions still have Power/Work output equal to (or greater than) the other participant by using a heavier KB? 
  • Leaving the weights alone, how many repetitions would the Power/Work "loser" have had to add to win? 
  • Leaving repetition numbers alone, how much heavier would the "loser's" KB have to be to win?
  • Leaving all else alone, how much quicker would the "loser" have to perform the same number of repetitions to be as Powerful as the winner?
The answers were reached only after using the Power/Work formulas.

The shorter participant (26 watts) with the heavier KB did produce less Power than the taller participant (36 watts). The shorter one would have had to do 50 more repetitions in the same time. Or do the same work in 5:45 less time, or use a 78#KB and do the same number of reps.

Power-to-Weight Ratio:  Power per kilogram of participant's bodyweight.  Since the shorter participant weighed considerably less than the more powerful participant, I adjusted the "score" based on bodyweight.  Since many of the figures were estimated (or rounded), a truly accurate reading is not available. But, the less powerful participant's ratio of Watts/kg = 0.3444, and the more powerful participant was 0.3409.  Too close to call, but you see how the efficiencies of the two participants' bodies are virtually EXACT! (at least in this experiment)

Amazing stuff. I am surely going to be experimenting with the above Power formula.  Some other linear lifts and movements I will experiment with  include:
  • Deadlifts
  • Sumo Deadlift High Pulls
  • Thrusters
  • Clean-and-Press
For example: Imagine Barbell Deadlifts.  If a two-minute test is used, with maximum repetitions being the goal, how will Power output change with higher reps of 135# versus mid-reps of 225# versus lower reps of 315#?? Or Power outputs for maximum repetitions without stopping, which would mean different time limits?

I produced a rudimentary Microsoft Excel spreadsheet "calculator" to determine Power and Work outputs for future experiments. I'll surely send it out to anyone who emails me. This could be a lot of fun.  If you are interested in helping out with my experiment by collecting data on some baseline WOs, please email me. The more data points I have to use, the more accurate results I can expect.

Reading: "Toward an Understanding of Power" by Patrick O'Shea.

NOTE: The actual WO was AMRAP in 20 minutes of KB C&Ps, with round one being 1R and 1L, round two being 2R and 2L, and so on.  Round 10 had 10R and 10L.  This definitely affected the total repetition numbers for 20 minutes. I'm confident that a less-structured WO would allow both of the participants to perform more repetitions in 20 minutes.

1 comment:

Louis Hayes said...

CFters: I posted a call for volunteers on the CF message board under "Community."