The Strength Deficit Formula Will Help you Decide Between

The Strength Deficit Formula Will Help you Decide Between Training for Size or Strength

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Decide what to focus on. Save time. Make your efforts count. Use the strength deficit formula.

Who is it for?

It applies both for athletes and bodybuilders. Bodybuilders will know whether they should focus on strength or size at this point of their training. Athletes need this information to periodize their training.

How does this formula work? And what is the strength deficit?

The strength deficit is the % difference between absolute strength and maximal strength. Simply put, it is the % of strength that you are NOT able to express in any given movement. 

A few more definitions

Concentric strength is the amount of force your muscles are able to produce while shortening.

Eccentric strength is the amount of force your muscles are able to produce while lengthening.

Maximum strength is the amount of force you can produce voluntarily. It is your 1RM in exercises such as the squat, deadlift etc.

Absolute strength would be the amount of force produced with total recruitment of all fibers i.e a tetanic contraction when all fibers fire simultaneously. The opposite is asynchronous contraction. Asynchronous contractions allow endurance performance.

Tetanic contractions cannot be achieved under normal circumstances. Elite powerlifters are able to recruit about 70% of motor units. But this is only possible after many years of specialized strength training. 100% recruitment occur in rare life-or-death situations. 

Putting it all together

The ascending recruitment principle also knows as the size principle, explains that slow twitch fibers are recruited first during concentric contractions. The fast twitch fibers are recruited last. Conversly during eccentrics contractions, the fast twitch higher fibers are recruited first and almost exclusively. Hence while eccentric contractions recruit less fibers in total it recruits preferentially the fast twitch fibers and this is why eccentric strength provides an accurate estimation of absolute strength.

How to calculate your strength deficit in the gym?

You can use the 4+2 method to calculate the strength deficit and is a favorite of many coaches.  One reason was that it is a very effective method for functional hypertrophy.

The second was that it allows to assess the strength deficit.


It is best to do it with the help of 2 training partners. And it is pretty simple.

First, select a compound exercise such as the bench press, squat, chin-up, deadlift…

Then warm up to your 4RM.

Do 4 reps to failure on a 40X0 tempo.

When you have completed the final fourth rep – which should be a max effort since it is a true 4RM – your two training partners will add weight on the bar while you rest, no more than 15 seconds. 

Pick a weight that allows you to perform two strict eight second eccentrics. A conservative approach is to begin with a 10-15% increment in load. Adjust upwards if possible.

Perform a 8 second eccentric rep. Have your training partners do the concentric portion. Do another eccentric rep.

The max weight you used on the 2 eccentric reps represents your max eccentric strength.

And the strength deficit is the % difference between this number and your 4 RM.

For instance if your 4RM is 300lbs on the bench press. And you performed 2 eccentrics at 350 lbs.

Your strength deficit is: (350/300) – 1  = 17%

How To Assess The Strength Deficit Without Spotters?

This will be done in two different sessions. In the first session you will determine your 1 RM concentric using a 40X0 tempo. In the second session which must be scheduled 5 days later, determine your max eccentric on a 80X0 tempo. Needless to say that caution is key. Make sure to work with safety bars and work within a range of motion that is 80% of your previous R.M. for safety purposes.

How to Interpret The Data?


For a bodybuilder, you can allow a 25-40% bracket.

When the percentage drops bellow 25% it is indicative of poor eccentric strength.

Actually it means you are good at recruiting your fast twitch fibers during the concentric portion of the lift. You have to all intents and purposes reached your strength potential for your current muscle cross section. So, you will make more progress by focusing size.

When the strength deficit is low, for instance 25 to 40%. Your best bet is to focus on strength. It would appear that you have room to improve your ability to voluntarily recruit your muscles.


When it comes to athletic performance, a 1-40% variance is seen. Depending on how close the competition is. During off-season you are closest to the 40% you want to move toward the other end of the spectrum closest to 1% when peaking depending on the sport.


Case 1: You need more size.

Considering your eccentric strength is the weakest link, it makes sense to improve your eccentric strength.  

Use a 12 week cycle during which you will be doing one eccentric focus workout out of two.

Two great methods to improve eccentric strength are:

  • The Slow Eccentrics Method

7-8 sets of 1 rep with 8 seconds eccentric

  • The Pause Method

Perform a 3-4 RM and for the last rep pause three times on the way down. Each pauses lasts 8 seconds. That’s, 3×8, a 24 seconds eccentric.

Your training partner calls the pauses at random. You should be able to stop the weight at any point across the ROM. Dorian Yates is famous for emphasizing this point: if you have picked the right weight, you can stop the weight wherever you decide.

Case 2: You need more strength. 

There are many methods to improve strength.

oldie but goodie: 5,4,3,2,1



or the modified Hepburn method:

This training protocol pairs antagonistic muscles.

A1 and A2 exercises focus on neurological activation. Pick basic exercises. Keep in mind that each rep needs to be perfect. This is not the place for forced reps. Concentric failure should occur on the last sets for A1 and A2. So pick the weight accordingly.

When selecting exercises B1 and B2 keep the same movement pattern but choose a slightly different exercise in order to tap into different motor units. Also, drop the weights to about 80%.

The key to progression from workout to workout is progressive overload. Each workout average tops the previous one. For instance:

Workout 1

Set 1 = 95kg

Set 7 = 100kg

Next workout

Begin at 97,5kg end at 105kg

A typical workout would be:

A1- Front squat, medium stance, 7-10 sets, 1-3 reps on a 40X0 tempo, rest 2 min

A2- Lying leg curl, plantar flexed, feet out, 7-10 sets, 1-3 reps on a 40X0 tempo, rest 2 min

B1- Front squat, narrow stance, heels elevated, 5 sets, 5 reps, on a 40X0 tempo, rest 2min

B2- Lying leg curl, plantar flexed, feet in, 5 sets, 5 reps, on a 40X0 tempo, rest 2min

A cycle on this program will generally last 4 to 6 weeks depending on your strength levels.

Wait at least 16 weeks before repeating it.

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