The kBox Power Test

The kBox Power Test is our standardized protocol for testing the power of a kBox user with reliable and comparable results. The protocol is based on a 4RM squat exercise using the kMeter feedback system.

How can you test your own or your clients’ power and get reliable numbers that can also be compared with other users and over time?

In flywheel training with the kBox, the kMeter feedback system provides accurate power monitoring, but a standardized test protocol is necessary to define in detail how the exercise should be performed and documented.

The kBox Power Test is developed so that kBox users will not need to spend time developing protocols of their own. In addition, it gives users the opportunity to share and compare results among each other. The kBox Power Test is intended for squats, but the same methodology can be applied to other exercises.

Using the kBox Power Test you also have the opportunity to submit your results to our upcoming reference database for kBox users. By sharing your data you will contribute to this flywheel training knowledge base for the benefit of your peers, and in addition you will get an early access to the results collected.

General setup

For testing of maximum power, the user should be rested and not do any heavy or fatiguing lower limb work for at least +48 hours. For readiness testing, the goal is to assess the level of neuromuscular fatigue so this does not matter. Always start with a maximum test to set a baseline even if you aim for a readiness test in-season to set a baseline. Re-calibrate baseline in 4-6 weeks of training or you might underestimate your user’s level of fatigue.

Harness

Tighten the Harness around the waist and the horizontal belt should be placed in the lower back and not over the glutes (too big) or in the upper parts of the lower back (too small).

Drive belt length

Subject should be able to fully extend ankle, knees and hip. He/she should not have any slack in the belt in the fully extended position.

Stance

Squat stance should be the users preferred stance where he/she can have the desired squat depth. Wide stance and externally rotated feet are allowed if preferred.

Depth

Subjects use the depth where they feel they can produce the most force much like a counter-movement jump (CMJ). (See also the comment about ROM to the right / below.)

kMeter settings

  • kMeter settings for kBox Power TestInertia 0.05 kgm2
  • Reps 4
  • Pre-reps 2
  • Weight in kgs
  • Manual start

Testing

  • Retract subject down into desired start position
  • Start kMeter acquisition in bottom position – tell subject to start.
  • Rep 1 (Pre-rep 1) is submaximal just to accelerate (80-90%)
  • Rep 2 (Pre-rep 2) is maximal
  • Rep 3-6 (Test reps 1-4) are maximal
  • Stop
  • Repeat after 3 minutes. Do 3-4 tests*
  • Analyze the best set.

*) In a team setting about 50% score their best value in test no. 3 and only 15% in the 1st test. For readiness testing, do a complete testing session to set baseline and then one test every session after warm-up for assessment.

Absolute power: Concentric peak power (average of the concentric peak power values for the 4 test reps).

Relative peak power: Relative peak power (the above metric divided by bodyweight in kg, calculated in kMeter app)

Range of motion: important for comparison in the same user over time.

Eccentric overload %: Peak Power Eccentric / Concentric. Shows the ability for the subject to decelerate hard in the eccentric phase and use the stretch-shortening cycle transfer more power into the concentric phase.

Submit data

Besides helping users to standardise test results, another purpose of the kBox Power Test is to aggregate power values from a wide range of users in a reference database available for our users.

What you need to submit is the .csv spreadsheet file that can be exported from the kMeter. This file automatically includes the power values as well as date and range of motion. In addition to these values, we welcome further data about the respective user, such as:

  • Gender
  • Age
  • Activity level (sedentary / active / trained / pro athlete)
  • Sports discipline (if professionally active athlete)
  • Level of play 1-3 (1: regional elite or below, 2: national elite, 3: international elite) if subject is an athlete
  • Position (as exact as possible)

We need the additional information manually entered in the comment column of the .csv file using this format:

M/F Age Activity-level Sports-discipline Level-of-play Position

For example:

M 21 athlete Soccer 2 goalkeeper
F 48 sedentary

So when you are done, just send the .csv file to us by email using powertest@exxentric.com.

 

 

If you have any questions about the kBox Power Test, please feel free to contact us. Go back to methods.

Learn More

Proceed to learn about
the kBox flywheel training device. 

Video: Fredrik and Henrik presenting the kBox Power Test.

 

 

Comment: Peak Power vs ROM

Squat depth, or range of motion (ROM), doesn’t seem to correlate with power. I.e. the users selects depth by preference where they feel they can produce the highest power.

Skärmavbild 2016-05-06 kl. 23.43.07ROM changes between testing sessions should be noted. In theory an increased ROM increases ability for power production but in reality we haven’t seen any strong correlation between ROM and power in the squat test. Increasing ROM also increases energy expenditure over the whole set which can counteract the benefit of increased ROM.

It’s however beneficial if a user is able to produce a higher power with an increased ROM since he/she probably have gained strength in the deeper position which is advantageous for building strength and power. However, lower or similar power with an increased ROM could be interpreted as a sign of decreased power or fatigue, consider re-testing when rested at a specific ROM to verify if the user has progressed.

 

Further reading

See the blog post by Fredrik Correa introducing the kBox Power Test here.

Extended blog post on the topic Squat Depth and Peak Power here.

Learn more about kBox methods here.