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Abdominal and Trunk Muscles: Building Strength and Endurance

In both contact sports and non-contact sports, all movements rely on strength and endurance in the abdominal and trunk muscles, according to LiveStrong.com. Midsection strength is essential to core stabilization and the protection of internal organs.

Core stabilization is actually more important than core strength, as evidenced by the common training assertion “stabilize first, strengthen second.” The term “core” (the center of the body and the root of all body movement) includes not only the abdominals, but also all deep and superficial muscles that stabilize, align, and move the trunk, pelvis, and hips.

A weak and unstable core in an athlete is like a house without a foundation. Repetitive or one-time stressors can cause inefficient movement, posture issues, and a variety of direct and indirect injuries.

Weak trunk muscles also limit the transference of force from the legs and hips to the upper torso, which is essential to throwing and hitting movements. As a result, shoulder rotation is more restricted, which is detrimental in sports that rely on an efficient muscle contraction sequence across various angles in the midsection.

Overall performance in any sports activity is limited by weak muscles. Often, many recreational and competitive athletes are pleasantly surprised to find out that when they enhance strength, endurance, and flexibility in their abdominal and trunk muscles, they experience noticeably improved control on their golf drive, tennis serve, or softball swing.

Strong Abdominal and Trunk Muscles Are Essential to Avoid Some Types of Back Pain

According to Fitness Measures and Health Outcomes in Youth, youth fitness tests include both trunk and abdominal strength and flexibility assessments. These physical fitness tests are popular because of their predictive ability; they can identify potential future low back problems as early as elementary school.

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Low back pain can often be attributed to weak stomach muscles and poor flexibility.

Low back pain, rapidly being recognized as a major health problem, is strongly related to having weak stomach muscles and poor flexibility, particularly in the hamstrings and lumbar area. The Presidential Physical Fitness Award, the American Alliance for Health, Physical Education, Recreation & Dance (AAHPERD) Physical Best Test and the YMCA youth fitness test all have various versions of the curl-up test to evaluate abdominal strength and endurance. They also have different versions of the sit-and-reach test to evaluate someone’s lower back and hamstring flexibility.

The development of torso strength and flexibility at an early age can help correct posture problems and reduce pelvic tilt. In time, that will decrease the likelihood of future painful back problems.

Cross River Therapy observes that about eight out of 10 American adults will experience back pain at some point in their lives. Back problems are the second leading reason for missing work (behind the common cold), and they contribute much more to this country’s health care problems than most people realize.

According to Cleveland Clinic, Americans swallow billions of tablets of nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen and aspirin each year to reduce pain and inflammation. The medical and economic consequences of back pain is estimated at $600 billion dollars, says Cross River Therapy.

Related: Delayed Onset Muscle Soreness and the Reasons Why It Happens

How the Abdominal and Trunk Muscles Work

The major abdominal and trunk muscle groups utilized during physical activities are the rectus abdominus, external and internal obliques, and transverse abdominus, according to KenHub. Anatomically speaking, the tops of the abdominal muscles are attached to the xiphoid process (the cartilage section at the lower end of the sternum) and the cartilage of the fifth and seventh ribs. The bottom section of these muscles are connected to the lower border of the pelvic girdle.

Normally, the abdominal muscles are utilized during any activity where the distance between the upper and lower attachments is shortened. During most movements in sports, this contraction occurs at a variety of angles.

Exercises for Improving the Abdominal and Trunk Muscles

There are various exercises that can be performed to strengthen the abdominal and trunk muscles. According to Physiopedia, these abdominal and trunk muscle exercises include:

  • Trunk flexion exercises
  • Trunk extension exercises
  • Right/left lateral flexion exercises
  • Trunk rotation exercises

Trunk Flexion Exercises

Trunk flexion exercises, such as bent-knee curl-ups and stomach crunches, strengthen the rectus abdominus, the major muscle of the midsection. It’s important to remember that trunk flexion, the focus of curl-ups and crunches that only involves the first 30 degrees during a full sit-up, is often confused with hip flexion.

Hip flexion, which involves having the body at an angle greater than 30 degrees from the ground, works the iliopsoas, a much smaller and less important supporting muscle of the midsection. Ideally, curl-ups should be half or partial sit-ups that focus on the initial 30 degrees, unless you are doing sport-specific conditioning for the hip flexors as a part of training for sports such as gymnastics.

To perform the basic curl-up correctly, lie on your back with your knees flexed at a slightly less than a 90-degree angle. The backs of your heels should be about 12 to 18 inches from your buttocks, depending on your leg length.  

Your feet should not be wider than four to six inches apart. Beginner exercisers may need their feet held down by a spotter; they can also be hooked under a solid object such as a barbell or a sofa.

The arms should never be behind the neck; instead, they should be crossed across the chest with the fingertips of each hand touching an opposite shoulder. Intertwining the fingers behind your head is no longer recommended. This hand position places undue stress on the neck and upper back, especially while an exerciser is straining to complete final repetitions and approaching exhaustion.

Keeping the hands behind the neck during curl-ups also encourages “hitching” with the shoulder muscles, when the goal of the exercise is isolate the trunk and abdominal muscles as much as possible. “Hitching” only promotes bad form, increases the possibility for injury, and provides less stress to the trunk and abdominal muscle groups to be strengthened. A momentary pause at the end of both the raising and lowering actions of the curl-up will also ensure that the exercise is performed correctly. 

According to Skimble, another variation of this exercise is to cross your legs in front during the curl-up. The feet should remain flat on the ground to better isolate the large abdominal muscles (important in achieving the desired “six-pack” abs) instead of the smaller supplementary muscles.

Beginning exercisers should work toward performing three to five sets of 15 to 20 repetitions each, maintaining proper form and dropping back slowly into the original supine position, for an excellent workout. As the rectus abdominus muscles get stronger, you can simply increase the number of repetitions, but I recommend keeping the same number of repetitions and increasing the resistance.

More resistance can be added to this exercise by holding a five- to 10-pound weight plate on your chest. Another option is to increase the angle of your back by dropping your head lower than your waist as you’re lying on an angled weight bench.

Most curl-up benches in health club weight rooms are adjustable to four or five different angles. If an adjustable bench is not available, you can perform inclined curl-ups on a grassy hill at your local park.

If you cannot perform 15 curl-ups correctly in the level position, try starting out by performing decline curl-ups (keeping your head higher than your waistline). This strategy will help you to avoid frustration.

Trunk Extension Exercises

Trunk extension exercises focus on the erector spinae muscles of the back. They also work out the small muscles of the posterior neck and obliques when a hyperextension is combined with a twist. These exercises use stabilizing muscles such as the rectus abdominus and gluteal region (buttocks).

Most universal weight machines have back hyperextension sections that enable an exerciser to lower and elevate the upper body from a horizontal hanging position. Extra resistance can be added by holding a weight or dumbbell behind your head.

“Good morning” exercises, according to Very Well Fit, are another type of trunk extension exercise. This exercise involves balancing a light barbell behind the neck while bowing forward and returning to an upright position, and it can be performed while an exerciser is seated or standing.

Probably the best and simplest trunk extension exercise involves lying prone (on your stomach) and raising your right arm and left leg simultaneously for 30 seconds. The exercise can then be repeated with the left arm and right leg.

Although many people just do curl-ups and do not supplement them with trunk extensions, it is important to do both types of exercises to keep your body in symmetry. For example, many people think they only have to use the leg extension machine in a weight room and avoid the leg curls while they’re getting in shape for skiing.

Although quadricep strength is ideally about 60% stronger than hamstring strength according to Prehab, it is important to train both muscles to keep them in balance. It is also a way to avoid tracking problems that can occur in the ligaments, tendons, and muscles surrounding the knee, according to Physio.co.uk. Keeping the small, supporting muscles of the spine strong and in symmetry with the rest of the body greatly assists in alleviating nagging back problems and reduces the possibility of going to a chiropractor later.

Right and Left Lateral Flexion Exercises

Right and left lateral flexion exercises train the internal and external obliques (the smaller muscles on the sides of the abdominal wall) and the erector spinae muscles. These muscles are best strengthened by side bends to both the right and left sides. Side bends are performed in a standing position as the exerciser holds a dumbbell in one hand and bends to one side, alternating between the right and the left side of the body.

Trunk Rotation Exercises

Trunk rotation exercises also strengthen the obliques and erector spinae muscles. These muscles are crucial to the body’s rotation when a ball is thrown or when a club, racket or bat is swung (as in golf, tennis, softball or baseball).

In addition to enhancing athletic performance, these muscles are in the best position to resist the rotational torques often responsible for disc problems in the spine. Trunk twists with a 45-pound bench press bar (no weights attached) held behind the neck and shoulders are excellent, provided that the rotational speed of the bar is kept under control. Russian twists and upper body rotation machines (now available at some health clubs) also work the torso in a circular range of motion.

Finally, adding a twist to curl-ups or crunches develop the obliques as well. Medicine ball crunches, crunches with feet elevated, Roman curl-ups, and V-ups require some coaching from a trainer or other sports professional before they can be effective, but these exercises are excellent for athletes who want explosive power and not just muscle tone.

Upside-down bicycle action leg pumps are popular with schoolchildren. I personally recommend staying away from isometric leg lifts while an exerciser is lying supine; these exercises have dropped in popularity due to the possible aggravation of back problems, according to Medical News Today.

It’s Important to Perform Exercises for the Abdominal and Trunk Muscles Correctly and Make Adjustments If Necessary

Exercise adherence (the percentage of people that stay with an exercise program once they have begun) is often less than 20%, according to Total Coaching. Anything that can be done to reduce the initial feeling of failure is beneficial. Ideally, in any strength-training activity – including exercises involving the trunk and abdominal muscles – the amount of weight should leave the lifter completely exhausted within the recommended number of repetitions.

Otherwise, adjustments should be made. For instance, if an exerciser can perform less than 15 consecutive curl-ups, then the angle of a weight bench should be reduced. If an exerciser can perform more than 20 reps, the angle of the bench can be increased.

Unlike other lifts such as bench presses and squats, exercises for the trunk and abdominal muscles can safely be performed by most people on a daily basis. Weight room workouts focusing on the upper or lower body should only be performed every other day and 48 hours of recovery time is necessary for optimal muscle development and the prevention of overtraining. Torso exercises appear to be an exception to this general rule and those muscles can be worked out more often. 

A quality workout involving the trunk and abdominal muscles can be completed in 10 to 20 minutes, depending on how many lifts and sets you choose. It’s essential to keep moving from one exercise to the next and avoid time-consuming distractions such as talking to others or stopping to listen to music. Two minutes of recovery time is all that is physiologically or psychologically required between sets.

Isometric “holds” (such as leg lifts from an underarm support) are oftentimes effective in rehabilitation programs. However, most athletic events involve dynamic movements, so they should be the focus of a normal workout.

Proper Breathing During Lifting Exercises Is Also Vital

It’s also important to use proper breathing while performing any repetitive lifting exercise to avoid the Valsalva maneuver. The Valsalva occurs when an exerciser is straining the body while attempting to exhale against a closed glottis. The Valsalva causes a considerable increase in blood pressure and temporarily restricts blood from returning to the heart.

After the Valsalva is released, the heart gets a sudden surge of blood, which can be potentially harmful. Remember to exhale during the most difficult part of a lift and inhale while you are returning to your starting position (or back to supine position during curl-ups).

Related: Progressive-Intensity Exercise and Improving Breathing

Improving Abdominal and Trunk Muscles Can Also Improve Self-Esteem and Overall Fitness

Cleveland Clinic notes that psychological studies have indicated that maintaining a “lean and mean” abdominal area is more important to improving self-image than other areas of the body, especially in young people. However, if your fitness goal involves losing fat, especially around your midsection), your workout time will be more effectively spent doing 60 minutes of calorie-burning aerobic exercise at a minimum of 60% of your maximal heart rate, rather than spending your lunch hour doing only curl-ups in a weight room.

According to LCR Health, “spot reduction” – somehow converting fat tissue into muscle cells as advertised by some self-proclaimed fitness gurus – is discredited by all scientific research. A combination of regular exercises for abdominal and trunk muscles will improve midsection muscle strength and endurance is the best way to improve sports performance, reduce excess fat around the waist, and improve your body image.

Daniel G. Graetzer, Ph.D., received his B.S. from Colorado State University/Fort Collins, a M.A. from the University of North Carolina/Chapel Hill and a Ph.D. from the University of Utah/Salt Lake City. He has been a faculty member in the School of Health Sciences, Department of Sports and Health Sciences, since 2015. As a regular columnist in social media blogs, encyclopedias, and popular magazines, Dr. Graetzer greatly enjoys helping bridge communication gaps between recent breakthroughs in practical application of developing scientific theories and societal well-being.

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