Wednesday, June 15, 2011

How To Calculate 1RM (rep max)

One rep max is measurement of muscular strength, not endurance.  Athletes who dominantly use the anaerobic system would get the most out of a one rep maximum strength test.

If a spotter isn't present or the individual has a medical condition that could be aggravated by high intensity weight lifting, use the equation.

There are many things that can go wrong with a maximal lift and dropping the weight is one of those things.  Consult an experienced or competent fitness professional to spot the lift.  They are knowledgeable about the potential risks associated with specific exercises.  They might also identify problems with technique that could have led to a future overuse injury.  If you can't afford a personal trainer, don't risk the lift and get injured.  Injury is the biggest enemy of progression!

Individuals with hypertension should especially avoid trying to lift as much as they can for one repetition.  Because heavy weights cannot be lifted quickly in a one rep max test, the primary movers and the core muscles will contract almost isometrically and increase blood pressure quickly.  This can lead to serious problems or even death.

Some people suggests isometrically lifting greater than the predicted 1RM prior to the test.  I'm not sure how this trend even started.  Although psychologically, this may help to boost moral, I have not read any physiological benefit about doing this- only performance decrements.  Performing a high intensity isometric contraction will create residual fatigue and affect the one rep max negatively by using up the energy provided by the phosphogen system (ATP-PC) (1,3).  In order to prepare the neuromuscular system and literally warm up the muscles through increased blood circulation, the specific muscle groups that will be worked maximally must be warmed up through lighter repetitions (1).  If a one rep max bench press will be performed, warm up the anterior deltoids and the pectoralis major prior to the test.  Light cycling would not be an ideal way to warm up the muscles of the bench press.

Generally, power exercises should be avoided due to its explosive nature.  Power exercise also cannot be spotted, so the risk is even greater.  It would be wise to estimate one rep max through multiple repetitions.  Besides, power is best developed through relatively light loads (30-45% of maximum), so it might not even be necessary to perform a one rep max (1).  A big exception to this applies to power lifters who are literally Olympic lift athletes.

For fitness purposes, one rep max is best applied to larger muscle groups and exercises that may be performed with control.
  • Bench press - Pectoralis major
  • Squat - Gluteus maximus
  • Split squat - Gluteus maximus, hamstrings
  • Romanian dead lift - Gluteus maximus
  • Step up - Gluteus maximus
  • Shoulder press - Trapezius, triceps
  • Knee extension - Quadriceps
  • Knee flexion - Hamstrings
Pay attention to muscle fiber type too.  Muscles of the core and other muscles which are naturally slow twitch should not be tested through a one rep max.  For example, stabilizers are mostly slow twitch and would not respond to strength training well- they should be trained for endurance, not strength.  Avoid the following exercises.  There is more than what is listed here.
  • External rotation - Rotator cuff muscles
  • Hip abduction - Gluteus minimus/ medius
  • Hip adduction - Adductor magnus
  • Spine extension - Erector spinae
  • Crunch - Rectus abdominis
  • Oblique crunch - External/ internal oblique
Now that you have a better understanding about one rep max, the contraindications and the risks involved with 1RM testing, hopefully you can make a better decision about what is more appropriate, the actual test or an estimation through the equations below.  Generally, more accurate estimations are produced with less repetitions than with more repetitions.
Equation 1
  • 1RM = [(reps/30) + 1] * weight (lbs)
Brzycki Formula (2)
  • 1RM = w / (1.0278 - (0.0278 * repetitions))

Go back to How To Design a Strength Training Program

  1. Bloomfield, John, Timothy Robert Ackland, and Bruce C. Elliott. Applied anatomy and biomechanics in sport. New York: Blackwell Scientific Publications, 1994. Print.
  2. Brzycki, Matt (1998). A Practical Approach To Strength Training. McGraw-Hill. ISBN 1-570-28018-5.
  3. Plowman, Sharon A., and Denise L. Smith. Exercise physiology for health, fitness, and performance. 3rd ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins, 2011. Print.