Muscular strength and endurance tests assess the ability of muscles and muscle groups to work against resistance with repeated muscular contractions. Muscular strength is the maximum force that a muscle or muscle group can exert in a single effort. Muscular endurance is the ability of a muscle or muscle group to perform repeatedly at submaximal force for a defined period of time. Thus, muscular strength and endurance tests measure two different types of ability, and some tests may be referred to as muscular strength endurance tests.
Muscular strength and endurance tests assess muscle strength and fatigue, in contrast to cardiorespiratory fitness tests that measure the amount of oxygen supplied to and utilized by muscles. Muscular strength and endurance depend on the physical condition of the muscles, the number and size of the muscles involved in the work, the proportion of muscle fibers that are involved, coordination between muscle groups, and any contribution from mechanical leverage. Because these properties differ among the various muscle groups, there is no single muscular strength and endurance test. Rather, each test is specific for the muscle group or groups, the type and speed of muscular contraction, and the angles of the joints involved in the particular action. Most muscular strength and endurance tests are similar or identical to components of a muscle fitness training regimen.
Muscular strength and endurance tests are often performed using free weights or resistance machines. Although resistance machines are safer and easier to use, free weights require more motor coordination and better balance, and thus involve more muscle groups, particularly stabilizing muscles. Free weights also allow more varied testing protocols. However, there are many muscular strength and endurance tests that do not require weights or machines. The Shape Up America! program uses push-ups to test muscular strength and endurance. The President's Challenge Adult Fitness Test uses half-sit-ups and push-ups.
Among the muscles of the body core, the abdominals are most frequently tested for strength and endurance. Weak abdominal muscles can cause poor posture, muscle fatigue, and low back pain and injury. There are various tests of abdominal strength, including straight leg lifts and four-stage and seven-stage tests that involve progressively more difficult sit-ups. However, half-sit-up or curl-up tests are the most common.
The YMCA half-sit-up test is used by the President's Challenge to assess abdominal muscle strength and endurance, although it also uses other muscle groups. It is considered a curl-up test because the trunk is only partially lifted from the floor. Curl-ups are often preferred to sit-ups because they do not involve the hip flexors. The test requires a mat or rug with two parallel strips of tape 3.5 in. (9 cm) apart, which are placed perpendicular to the body and can be felt with the hands. The starting position is with the back on the mat, the knees bent to 90°, the feet flat on the floor, and the palms on the mat with the fingers just touching the upper tape. The lower back is flattened to the mat and the trunk is lifted so that the fingers move to the second tape. The fingers, feet, and buttocks remain on the mat. To complete the half-sit-up, the shoulders lower to the mat, although the head does not need to touch. The score is the number of half-sit-ups completed in one minute. Pacing should be such that the full minute can be completed. Alternatively, curl-ups are performed at a pace of 50 beats per minute and continued for 80 repetitions or until the pace or proper technique cannot be maintained.
Shoulder pain in middle-aged and older people is often caused by reduced strength and endurance in the upper body and shoulder muscles. These muscles are often tested with push-ups or pull-ups.
The starting position for push-ups is the elevated or up position. In a standard push-up test, performed by males in the President's Challenge and Shape Up America!, the hands are shoulders-width apart and flat on the floor and the arms are fully extended directly below the shoulders. The back and legs form a straight line, with the toes curled under, and all of the weight is on the hands and feet. The body is held rigid and pushed up and down using the muscles of the arms, shoulders, and chest, with the feet as the pivot point, so the workload is the body weight. The modified push-up is used for females and males who cannot perform at least eight standard push-ups. The hands are flat on the floor and slightly in front of the shoulders, to place them correctly for the downward motion. The knees are bent on the floor and the feet are in the air and crossed at the ankles. Thus, the knees form the pivot point and the workload is reduced to the upper body. In the President's Challenge, the chest is lowered to 2 in. (5 cm) from the floor on an inhale and raised back up on an exhale. For Shape Up America!, the chest touches the floor. Push-ups are continued for as long as possible. It is important to maintain a rigid position with a flat back and to fully straighten the arms in the up position. In the President's Challenge, a brief rest is permitted in the up position.
Pull-up or chin-up tests require a horizontal overhead or pull-up bar from which the subject can hang with the arms fully extended and the feet above the ground. The bar is grasped either overhand (palms away from the body) or underhand (palms toward the body). The body is raised until the chin clears the bar and then released back to the fully extended position in a smooth motion. Swinging, bending, or kicking the legs and jerky movements are not allowed. As many pull-ups as possible are completed.
Other upper-body muscular strength and endurance tests include:
Squat tests assesses hip and lower-leg function, balance, and the strength of the quadriceps, gluteals, and hip stabilizers. Squat tests can be either single or two legged. For a two-legged squat test, standing with the back to a chair, hands on hips, and feet shoulders-width apart, the subject squats, lightly touching the chair, and stands back up as many times as possible.
For the chair-stand test, the subject sits in the middle of a chair, with feet flat on the floor and shoulders-width apart, arms crossed at the wrists and close to the chest. The score is the number of times the subject can stand up and sit down completely in 30 seconds.
The wall sit assesses lower-body strength, especially the quadriceps. Standing against a wall with the feet about shoulder-width apart, the subject slides down the wall until both knees and hips are at a 90° angle. One foot is lifted off the ground and held for as long as possible. After resting, the test is repeated with the other foot.
Several lower-body tests involve jumping. The 30-second endurance jump counts the number of jumps over and back a 12-in. (30-cm) hurdle—taking off and landing with both feet—in 30 seconds. Other tests include the multistage hurdle jump test and the 45-second agility hurdle jump test.
Other muscular strength tests include:
Other muscular strength and endurance tests include:
There are specific precautions for different muscular strength and endurance tests. For example, situps and curl-ups must always be performed with the lower back flat on the mat, since arching the back can cause injury. Increased blood pressure is a normal consequence of resistance exercise. Exhaling on the concentric phase—when the muscles are shortening, as in the up movement of a push-up—and inhaling during the eccentric phase when the muscles are lengthening under tension—as in lowering during a push-up—can help keep blood pressure within a safe range. Push-ups and pull-ups may aggravate preexisting shoulder, elbow, or wrist pain. Finally, spotters are essential whenever using heavy free weights.
Muscular strength and endurance tests should take place in a quiet environment at a comfortable temperature. Subjects should be carefully instructed in the proper exercise techniques, including body position and starting and ending points. Protocols should be followed carefully, so that the results on future tests are comparable. Although sit-up and push-up tests may not require a warm-up, other types of muscular strength and endurance tests do require warming up prior to testing.
Muscular strength and endurance test results can be improved by repeating the exercises frequently or increasing the workload for the same number of repetitions. Exercises should be performed at least three days each week. The half-sit-up load can be increased by folding the arms across the chest or placing them behind the head. Standard push-ups can be made easier by performing them against a wall. The intensity should be increased only if proper posture and control can be maintained. Participants should work up to three sets of 25 half-sit-ups and three sets of 10 to 20 push-ups, with short rests between each set. Once half-sit-ups and push-ups are mastered, additional exercises can be added, including equipment such as balance balls, weights, or elastic tubing.
Although any exercise can result in injury, there are generally no complications with muscular strength and endurance tests. However, they should always be conducted according to proper protocols and all precautions should be followed.
See also Isometric training ; Shoulder stability .
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American College of Sports Medicine, 401 W Michigan St., Indianapolis, IN, 46202-3233, (317) 637-9200, Fax: (317) 634-7817, http://www.acsm.org .
Cooper Institute, 12330 Preston Rd., Dallas, TX, 75230, (972) 341-3200, (800) 635-7050, Fax: (972) 341-3227, firstname.lastname@example.org, http://www.cooperinstitute.org .
President's Council on Fitness, Sports & Nutrition, 1101 Wootton Pkwy., Ste. 560, Rockville, MD, 20852, (240) 276-9567, Fax: (240) 276-9860, email@example.com, http://www.presidentschallenge.org .
YMCA of the USA, 101 N Wacker Dr., Chicago, IL, 60606, (800) 872-9622, http://www.ymca.net .
Margaret Alic, PhD