The fitness industry defines muscular strength as the physical ability to generate force against an external load. The 1RM simply represents the maximum amount of force that a muscle can exert against an external resistance, moving through a full range of motion to the extent of its capabilities. Read on to understand the foundations and calculations in determining a personal training client’s safe 1RM, or one-rep max.

One Heavy Push versus Multiple Sets at Lower Weight

Attempting a 1RM requires a great deal of focus and mental preparation on the part of the lifter. A maximal exertion for a single repetition consumes a surplus of training time as well as drains an excessive amount of the trainee’s recuperative resources. Simply put, the time and energy spent in performing a one-rep max detract from the flow of the overall training regimen; moreover, any performance of exertions with maximal workloads may lead to significant stress imposed on muscle tissues, bone and ligaments, which in turn can trigger metabolic alterations. In light of this, many practitioners and coaches view the 1RM as dangerous and impractical in most exercise settings.

Multiple repetition tests prove much safer and more applicable to different populations, whether the client seeks strength, endurance, power, or hypertrophy. Many strength and conditioning trainers utilize submaximal testing to estimate the one-rep maxfor a variety of strength measures. The performance of such submaximal sets allows for the safe and effective determination of maximal loads, a starting point from which an athlete can then progressively increase his muscularity. The combination of the training effect elicited through the use of submaximal sets along with the ability to use data from these submaximal performances as indicators of 1RM/absolute strength of the client makes this a valuable tool for many coaches.

The Brzycki Equation

Armed with this knowledge, researchers have through the years attempted to develop accurate ways to estimate an individual’s 1RM, choosing to employ the safer alternative of submaximal multiple repetitions. The results suggest that the Brzycki equation may provide a satisfactory estimate of an individual’s one-rep max for the bench press, utilizing data culled from submaximal tests of 7-10 RM. The Brzycki formula can function as a useful tool in fitness program preparations, especially for those clients who seek a quantifiable measure of their existing performance and future progress.

This formula states that an individual’s 1RM = w ÷ [(1.0278) – (0.0278 x r)]. The w represents the weight, in pounds, lifted for 10 successful repetitions. The r stands for the number of repetitions performed for the given exercise.

Below, we outline a safe protocol for determining a client’s 1RM:

 *a warm-up set of a light weight lifted for 5-10 reps (light weight = 40-60% of perceived max), followed by a 1-minute rest

*increase weight slightly for 12-15 reps at a moderate weight (60-80% of perceived max), followed by a 1-2 minute rest

*increase load again by 5-10%, executing up to 10 repetitions. If the client successfully completes 10 or more repetitions, allow for another 1-2 minute rest, then add additional weight, keeping a check on the client’s RPE.

A specific example might look like this:

After conducting a warm-up with gradual weight increase, your client bench presses 55 pounds 10 times. Plug these numbers into the equation:

1RM = w ÷ [(1 .0278) – (0 .0278 x r)]

w = 55, r = 10

1RM = 55 ÷ [(1.0278) – (0.0278 x 10)] = 55 ÷ [1.0278 – .278] =

55 ÷ .75 = 73.333

1RM= 73.33

Determining a Safe Percentage

In this example, 73 pounds represents the estimated 1RM,(useful when converted into a percentage), to suggest an appropriate load for this client, when attempting this specific exercise. Trainers often turn to percentage-based programs when designing workouts, with most exercises executed at a designated percentage of the athlete’s strength capabilities (1RM). We can reason that if a poorly designed prediction equation places the one-rep max too heavy, training will lead to increased risk of injury. On the other hand, when underestimating the one-rep max, an athlete may not witness optimal strength gains and adaptation.

Thus, if the client comfortably lifts 40 pounds, we can determine his %1RM using the equation w ÷ 1RM = %1RM. From this example, w = 40 and 1RM = 73, so 40 ÷ 73 = .55 Your client, in this example, can successfully lift 55% of his 1RM. (This is probably too low for most fitness clients!)

Key Takeaway Points

The one-rep max concept establishes a baseline when planning successful strength training programs for clients. When making predictions based on formulae/calculations, however, trainers must understand that mere numbers do not always translate into a client’s strength/experience. Each person comes to his trainer with different needs, goals, physical/mental constraints, and unique motivation. Therefore, consider calculations as a single step when designing/tailoring workout protocols. Prudent trainers learn that such factors must pair with common sense when addressing a variety of client capabilities.

Through resistance training, and the adaptive ability of the human body, strength acquisition fluctuates, and so too will an athlete’s definitive 1RM. Thus, using the reliable predictive Brzycki equation for this value can help throughout the course of a client’s journey in strength training.


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NFPT Study and Reference Manual: The Fundamentals CPT  Seventh Edition © 2017

Cathleen Kronemer

Cathleen Kronemer is an NFPT CEC writer and a member of the NFPT Certification Council Board. Cathleen is an AFAA-Certified Group Exercise Instructor, NSCA-Certified Personal Trainer, ACE-Certified Health Coach, former competitive bodybuilder and freelance writer. She is employed at the Jewish Community Center in St. Louis, MO. Cathleen has been involved in the fitness industry for over three decades. Feel free to contact her at She welcomes your feedback and your comments!