Assessment of Muscular Strength

Whether you're a performance athlete or a recreational weight lifter, getting the most out of your workout requires lifting enough weight to get a training effect. According to the National Strength Conditioning Association, or NSCA, exercisers often train at only 42 to 57 percent of the maximal load they are capable of, but increases in strength require training loads ranging from 60 to 85 percent of maximal capacity. Maximal strength testing using compound exercises like the back squat can establish a baseline to predict optimal training loads for a variety of exercises.

Why the Barbell Squat?

Because multiple muscles are involved in a back squat, using it to test lower body strength can give you a baseline to predict maximal strength for various exercises, according to the NSCA. Muscles of your quadriceps, hamstrings, gluteals, adductors, abductors, low back and abdominals all come into play in a squat. Your back squat test results can be translated to apply to a variety of exercises using prediction equations established for a number of hamstring- and knee extension-based exercises, including leg curls, deadlifts, lunges, stepups, and leg extensions.

Max Values

Strength test values are based on one-rep max, or 1RM, which is the maximal load you can lift one time with good form. To perform a 1RM test, do a warmup of five to 10 repetitions of squats with a load of 40 to 50 percent of your estimated maximum. After a brief rest, increase the load to 60 to 80 percent of estimated maximum and perform three to five repetitions. Slightly increase the load, resting three to five minutes between trials, arriving at 1RM in three to five trials.

Execution Essentials

Correct execution is vital to prevent injury and to get accurate results. Use two spotters positioned at each end of the barbell. Stand with your feet flat, shoulder-width apart. Place the bar just above your shoulder blades, not on your neck, and grip slightly wider than shoulder width. Keep your chest lifted and chin up, and contract your abdominal muscles and sit back over your heels, slowly moving downward until your thighs are parallel to the floor, knees at 90 degrees. Exhale and drive your weight upward, pushing through your heels.

Not for Everyone

Back squats are used in the athletic arena, and prediction equations are based on performance of NCAA college athletes. Because squatting requires balancing a heavily weighted bar, the back squat test poses a potential for injury to the low back and knees, and may not be appropriate for the average exerciser. According to Ian McLeod, author of "Swimming Anatomy," the most common causes for injury to the knees during a squat are shifting them forward past the toes or allowing them to collapse inward on the downward phase. Failure to contract the core muscles can lead to back injury. An alternative to squatting is to use a leg press machine to test for maximal lower body strength.