Field tests for measuring muscular strength

Unquestionably, the most widely used field test for evaluating muscular strength is the one-repetition maximum (1-RM) test. This test has traditionally been used to assess dynamic strength by determining how much weight an individual can lift during a single repetition. This approach to measuring muscular strength usually involves performing three or four exercises that are representative of the body's major muscle groups. For example, performing a bench press or an incline press is frequently used to assess the strength of the torso (upper body) muscles, while a squat or a leg press is typically performed to ascertain hip-leg (lower body) strength.

Similar to almost every attempt to quantify muscular endurance, conducting the test is often easier than knowing how to accurately interpret test results. Once you've obtained your 1-RM results, you face a dilemma in deciding what, if anything, the data mean. For example, are they an accurate reflection of how much work you actually performed in the weight room? Do they provide you with a reliable means for evaluating the effectiveness of your strength-training efforts or your current strength level? Do they give you a logical means for comparing your strength level to another person's? All factors considered, for each of the aforementioned issues, the answer is, at best, questionable.

How much work you actually perform in the weight room and how strong you actually become are affected by a number of genetic factors that are beyond your control. Collectively, these genetic factors make muscular fitness and the assessment of muscular fitness a relative matter. In other words, what you do in the weight room is relative to your genetic capabilities. Accordingly, demonstrating a specific strength achievement is relative to such factors as the length of your arms, the proportion of fast-to-slow twitch fibers, the ratio of muscle length to tendon length, the insertion point of the muscle on the skeletal lever involved, the level of neuromuscular efficiency, etc.

In addition to the restraints that genetic factors impose on 1-RM testing, a more serious limitation with this approach is that it can be dangerous. Safety can become a major concern if you attempt to exceed the physiological capacity of your body, or if your lifting techniques expose you to undue risk of injury.

Unfortunately, the trial-and-error method of increasing the weight in the 1-RM approach (particularly if it's combined with an adrenaline rush or a machismo-driven attempt to validate an unrealistic exhibition of strength) often leads to attempting to use too much weight in assessment efforts. Attempting to perform a 1-RM lift with a relatively heavy weight can place an inordinate level of stress on your muscles, bones and connective tissues. The 1-RM approach to strength testing can also increase blood pressure to a risky level. Lifters, particularly at the upper end of the trial-and-error 1-RM method, tend to hold their breath while performing the exercise, an action that increases blood pressure beyond what is normally encountered when lifting less (submaximal) resistance.

Another safety issue involved in 1-RM testing is that if you attempt to lift too much, you may compromise the proper techniques for performing the exercise, and injure yourself. For example, one of the most common problems attendant to 1-RM testing is back injuries, which occur as the result of the 1-RM bench press test. When using excessively high loads, individuals arch their backs during the lift, thereby placing undue stress on their lumbar spine. Finally, in a few isolated instances, individuals have actually lost control of the weight at some point in the 1-RM lift and injured themselves. Accordingly, if you decide to perform 1-RM testing, you must use a competent spotter to help maintain control of the weight during the exercise and to provide feedback regarding adherence to proper techniques.

Given that individuals have their own unique genetic potential for achieving (and demonstrating) muscular strength, comparing the strength of one person to another is of dubious value. A more logical approach would be to compare the results of your strength testing to your previous performances. Even accounting for the occasional glitch in testing results that might be attributed to either emotional or mental factors, comparing the results of your assessment efforts with previous test scores should, in the long haul, provide a reasonable basis for measuring the relative progress of your training efforts.

Measuring strength safely

In lieu of the inherent problems with assessing strength (e.g., genetic differences, safety limitations, etc.), what measures should you use to assess strength? Two of the better approaches are the strength-to-weight ratio and the one-rep predicted max from reps to fatigue.

The strength-to-weight ratio is a relative method of determining how much you lifted on a given exercise compared to the listed values. This approach uses your body weight and gender to categorize your performance on a scale ranging from excellent to poor. Tables 1 through 4 present the 1-RM/BW values for the bench press and leg press exercises. To use either table, you divide the amount lifted by your body weigh and then compare the resultant to the values listed in the table. For example, if you are 35 years old, weigh 200 pounds, and bench press 250 pounds, your 1-RM/BW ratio of 1.25 (250 divided by 200) would categorize your performance as "excellent."

The one-rep predicted max from reps-to-fatigue method is an approach based on the precept that a direct relationship exists between anaerobic endurance and strength. Given this relationship, it follows that you can determine your level of strength by assessing your level of anaerobic endurance (and vice versa). Unquestionably, the most positive aspect of this approach is that measuring anaerobic endurance is a much safer process than directly determining your 1-RM because it involves lifting submaximal loads.

Despite being a much more safety-oriented approach for measuring your 1-RM, identifying a practical and relatively accurate method for assessing anaerobic endurance has been an impossible task for the exercise science community until recently. Research conducted in the early 1990s by Matt Brzycki, the health fitness coordinator and strength coach at Princeton University, demonstrated that a nearly linear relationship exists between the number of reps you can perform before you reach a fatigue state and the percentage of maximum load you can lift. Based upon his findings, Brzycki subsequently developed an equation for predicting 1-RM when the number of reps-to-fatigue performed is less than 10 (refer to Exhibit 1). If the number of reps-to-fatigue is exactly 10, you should divide the weight lifted by 0.75 to get your predicted 1-RM. Because Brzycki's equation has been found to be less reliable if the number of reps-to-fatigue exceeds 10, the reps-to-fatigue method for predicting 1-RM should not be used if the rep count exceeds 10. A user-friendly matrix for predicting 1-RM based on reps-to-fatigue with weights ranging from 45 to 310 pounds is presented in Table 5.

Checking out the facts

The need to check things out starts fairly early in most people's lives. Check both ways before you cross the street. Check with your parents before you make plans. Check your appearance before you leave for school in the morning. And so forth.

Realistically speaking, as you get older, the need to continuously check things out only becomes more important. In a similar vein, it could be reasonably argued that if your clients want to maximize the capacity of their body to withstand the daily demands imposed upon it and minimize musculoskeletal aches, pains and injuries, they should periodically check their level of muscular fitness. Although they might have an intuitive feeling for how muscularly fit they are, a more structured evaluation can offer a quantified basis for deciding whether they need to take specific steps to remedy a functional deficiency. The data they obtain from such an assessment can also serve as a subsequent benchmark for evaluating how well their muscular conditioning program is working. The point to keep in mind is that individuals are never too old to test themselves. If the test for checking their level of muscular fitness is conducted safely and provides them with meaningful feedback, they have everything to gain, and nothing to lose. The facts are irrefutable: muscles do matter. Check it out.

REFERENCES

American College of Sports Medicine. Guidelines for Exercise Testing and Prescription, 5th ed. Philadelphia, PA: Lea and Febriger, 1995.

Brzycki, M. Strength testing -- Predicting a one-rep max from a reps-to-fatigue. Journal of Physical Education, Recreation and Dance 64 (1): 88-90, 1993.

Golding, L.S., C.F. Myers & W.E. Sinning. The Y's Way to Physical Fitness, revised. Chicago, IL: National Board of YMCA, 1982.

Heyward, V.H. Advanced Fitness Assessment & Exercise Prescription, 2nd ed. Champaign, IL: Human Kinetics Publishers, 1991.

Nieman, D.C. Fitness and Sports Medicine: An Introduction, 2nd. ed. Palo Alto, CA: Bull Publishing Co., 1990.

Peterson, J.A. & C.X. Bryant. The StairMaster Fitness Handbook, 2nd ed. St. Louis, MO: Wellness Bookshelf, 1995.

Peterson, J.A., C.X. Bryant, & S.L. Peterson. Strength Training for Women. Champaign, IL: Human Kinetics, 1995.


By James Peterson, Ph.D., FACSM, a sports medicine consultant, fellow of the American College of Sports Medicine, a former faculty member at the United States Military Academy and a former director of sports medicine for StairMaster Sports/Medical Products Inc.