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Why 50-60% of 1 Rep Max Makes You Fitter

You get fitter, faster, by using a weight that just allows you to do your reps unbroken.

In CrossFit, we do “met-cons” to improve our cardiovascular fitness, which are high-intensity workouts often using weights.  To get the most bang for our buck, we want to use a weight that allows you to move as fast as possible, while still challenging you to work at your limit.  This means you’re maximizing your power output, and therefore your fitness gains.  You may find it easier to push yourself harder, and get fitter, faster, if you understand what this means.

What is power? Physics textbooks define power by the formula P=w/t.

P=w/t

Where:

  • P = power

  • w = work, which in turn =  force * distance

  • t = time

So we can also write the formula as Power = (force * distance)/time

The force is equal to the weight moved.  Normally, we ignore body weight to vastly simplify the math.  Obviously, it is always relevant, but it is also pretty much the same unless you are rapidly gaining or losing weight, so we normally treat it as constant.

Distance is how far you move the weight.

Time is how long it takes you to move the weight that distance.

CrossFit defines “fitness” as “increased work capacity across broad time and modal domains.”  That “increased work capacity” means the ability to do the same amount of work, or more, in less time.  This means you can do a more challenging version of a workout in the same time, or do the same version of a workout in less time.  You will even find yourself doing a harder version of a particular workout in less time!  This is increased work capacity, which is the same thing as increasing your average power output.

Related: Strength Training for Endurance Athletes – Videos & Guide

CrossFit met-con’s are all about average power output.  Think about a met-con you’ve done where round 2 took much longer than round 1, and round 3 longer than 2.  Your average power output dropped.  Being fitter is about (1) increasing your maximum power output, and (2) improving your ability to maintain your power output over time.

Being fitter is about (1) increasing your maximum power output, and (2) improving your ability to maintain your power output over time.

So what does this have to do with 50-60% of 1 repetition maximum (“1RM”)?  When we program met-cons at CrossFit Slipstream, especially benchmark workouts that have “prescribed” weights to them, you will notice that we direct you to “use the lower of 42.5/30kg or 60% 1RM” for the weight to use.  In this example, if your 1RM for the movement in question is 70/50 (men’s weight/women’s weight) or more, you can use the “prescribed” weight.  If you can do much more than 70 or 50, congratulations!  You should be able to do the workout really fast at 42.5 or 30 kg!  If your 1RM is less than that, use 60% of your actual or estimated 1RM.  This will adjust the difficulty to keep your power output high, which is the best way to – you guessed it – increase your average power output.

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Doing the workout with too much weight will slow you down, lowering your average power output, reducing the metabolic load, and reducing your metabolic gains from the workout in favor of strength gains. While we want to get stronger, the time to do that is during focused strength work, not during met-cons.

Related: What Do You DO At A CrossFit Box?

Through a mix of reviewing the scientific research and our own experience, we find that 50-60% of 1RM allows most of our athletes to complete most weightlifting sets unbroken, which is important to keeping your speed, and thus your average power, high.

Ultimately, the 50 & 60% marks come from a mix of science and experience of what works to keep you moving fast, but challenged, to maximize the benefit of your workout. It also automatically adjusts your weight so you can benefit fully from having others around you doing the same workout – you’ll be able to keep up and that helps you push yourself harder!

-John Bryant
Founder/Head Trainer

john@crossfitslipstream.com