Critical Force Calculator

The Critical Force Calculator will help you determine where you stand with your forearm aerobic endurance. If you’re a strong sport’s or trad climber, but end up pumped on your way to the crux, it means that your forearm aerobic endurance likely requires some attention. The Critical Force Calculator will also allow you to find the optimum load at which you should train so that you will soon breeze up through those endurance routes!

For best results, train exactly at CF intensity and try to maximize the total work done.

Instructions

To determine your forearm aerobic endurance Critical Force, you can use the calculator below. Input your body weight and your 7-second MVC on a 20 mm edge, followed by respective times to failure for the 7/3 Endurance Repeaters at 80% MVC-7 and 60% MVC-7. For the last measurement you may choose 45%, 50% or 55% MVC-7 load, just make sure that you fail in under 1200 seconds.

The calculator will output your CF and the weight you need to subtract in order to exercise exactly at CF load. You will also receive a brief assessment of your strength and forearm aerobic endurance. The calculator is calibrated for the half crimp grip on a 20 mm edge, to enable a direct comparison with the results published in [1]. The bouldering level prediction is based on the results of the survey published at [2].

You can find more detailed information regarding the role of the Critical Force in sport’s and climbing endurance training in [3]

Example Critical Force test

Let’s say you weigh 68 kg, and you take the MVC-7 test on a 20 mm edge. You can add 32 kg to the bodyweight and hang for 7 seconds, so the MVC-7 load is 100 kg. Now we can calculate your 80%, 60% and 45% loads, which are 80 kg, 60 kg and 45 kg respectively.

  1. Test your T80% :
    • To set the 80% load, you must add 12 kg to the harness.
    • Execute a set of 7/3 Repeaters until failure.
    • Add the hanging times together. This means that if you were able to execute 10 full hangs and failed at hang 11 in the 4-th second, then your T80% is 74 seconds.
    • Rest 15 minutes before the next test.
  2. Test your T60%
    • To set the 60% load, you must remove 8 kg using a pulley system.
    • Execute a set of 7/3 Repeaters until failure.
    • Add the hanging times together. This means that if you were able to execute 15 full hangs and failed at hang 16 in the 4-th second, then your T60% is 109 seconds.
    • Rest 30 minutes before the next test.
  3. Test your T45%:
    • To set the 45% load, you must remove 23 kg using a pulley system.
    • Execute a set of 7/3 Repeaters until failure.
    • Add the hanging times together. This means that if you were able to execute 60 full hangs and failed at hang 61 in the 4-th second, then your T45% is 424 seconds.
    • If your aerobic endurance is very good, and you are able to last more than 20 minutes at the 45% load, you should change the load to 50% or even 55% of your MVC-7 and redo the test.
  4. Enter your data into the form and press calculate.
Input
kg lbs
T(45%) [s]
T(50%) [s]
T(55%) [s]

Results