Finding biomechanically effective and functional exercises for the abdominal and back muscles is a popular topic of discussion in the fitness industry. Choices for abdominals have ranged all the way from traditional sit-ups through abdominal crunches to stabilization exercises. The selection of back exercises includes good mornings, dead lifts and various stabilization techniques. In the search for effective exercises, the fitness profession has even borrowed techniques from related areas such as physical therapy, Feldenkrais, yoga and Pilates. With such a wide range of exercises, techniques and equipment available today, fitness professionals must educate themselves on determining the most biomechanically effective choices for their clients.
The process of choosing the best exercises for your clients is similar to the process of choosing a car. You cannot select the best car for a person without first assessing and prioritizing their needs. While customers want a car that will take them from one place to another, their need for a sports car, sedan or van will probably vary over their lifetime. It's the same with choosing spinal exercises for your clients. You'll have to first assess and prioritize their needs. Factors to consider will include age, goals, history of back injury, equipment accessibility and available time. The client’s needs will also vary over their lifetime so periodic reassessments will be necessary.
To help our clients make the best choices, it's important for personal trainers to educate themselves on spinal anatomy, kinesiology and basic exercise formats. While the basic biomechanics of the spine do not change over time, there are always new exercises and different pieces of equipment to consider. A solid foundation in spinal mechanics and logical problem solving will help you analyze any new techniques you might see.
Basic Anatomy and Kinesiology of the Spine
When analyzing spinal exercises, it's important to be familiar with the bony anatomy of the spine and the abdominal and back muscles. The vertebral column is composed of vertebrae, intervertebral disks and ligaments. It has five sections: cervical (neck), thoracic (chest), lumbar (lower back), sacral (pelvis) and coccygeal (tailbone). Each section has different functions, strengths and weaknesses than the other. However, because the spine is one column, the position or movement of one part of the spine can affect other portions. Fitness professionals are primarily focused on the cervical, thoracic and lumbar portions of the spine.
The spinal column is designed for a combination of stability and mobility that varies depending on the primary function of each portion of the spine. The first seven vertebrae of the spinal column form the neck or cervical portion of the spine. The cervical spine is primarily designed for mobility to allow the head to turn and see all around. The thoracic spine is composed of the next twelve vertebrae. These vertebrae, the ribs and the sternum (breastbone) form a series of bony rings, commonly called the ribcage, which encircle the heart and lungs. This framework is much stiffer than that of the cervical and lumbar spine which increases the stability of the thoracic spine. The lumbar vertebrae must be adept at mobility and stability. The lumbar spine is also the most commonly injured area of the back. The predisposition to injury is often due to areas of hypermobility (lack of stability) alternating with areas of hypomobility (lack of mobility) and the use of poor body mechanics.
When looking at the muscles affecting spinal movement, you must consider both the abdominal and back muscles. There are four layers of abdominal muscles located in the front of the body. From the most superficial (near the skin) to the deepest (near the center), they are the rectus abdominus, the external obliques, the internal obliques and the transversus. The rectus abdominus and the obliques perform spinal flexion. The obliques also perform a combination movement incorporating both flexion and rotation to one side. The function of the transversus is not completely understood. Some experts believe that the transversus is a skeletal muscle that can be actively contracted to flatten the abdominal area. Other professionals believe that the transversus is an autonomic muscle used in involuntary movements such as sneezing.
There are also multiple layers of back muscles. The most superficial layers provide scapular motion from muscles such as the trapezius, latissimus dorsi and the rhomboids. Under this layer, as you go from the most superficial to the deepest, are the erector spinae, the semispinalis, the multifidus and the rotatores. The erector spinae extend multiple vertebral segments of the back simultaneously. The semispinalis and multifidi extend two to four vertebral segments at a time. The rotatores will rotate one or two vertebral segments at a time. Other muscles that attach to the spine include the quadratus lumborum and the psoas. The quadratus lumborum is the primary mover during lateral flexion of the lumbar spine. While the psoas muscles are not normally considered primary movers for the spine, they can affect spinal biomechanics due to their attachments.
Flexion, extension, rotation and lateral flexion (side bending) are all movements that can be performed by the cervical, thoracic and lumbar spine. While there is little movement at any one segment, the overall movement of the spinal column is significant. The range of motion (ROM) for each movement varies depending on the area of the spine, gender and age. Spinal ROM can decrease by as much as 50% as we age. Spinal flexion has the greatest ROM with most of the movement in the lumbar region. It may be of interest to note that flexion and extension are the only pure movements of the spine. Rotation and lateral flexion are combination movements. Rotation of the spine will include some lateral flexion and vice versa.
Stabilization vs. Active Movement Exercises
There has been a lot of discussion about the effectiveness of stabilization exercises compared to the more traditional active spinal movement exercises such as abdominal crunches. In this author’s experience a well-rounded exercise program should include both components. The emphasis on each type of exercise will depend on the client’s current physical condition and long-term goals.
For purposes of this discussion, we will define stabilization exercises as exercises where the goal is to keep the spine in proper alignment while performing other movements. Stabilization exercises require a co-contraction of the back and abdominal muscles. Spinal stabilization is easier to achieve when the body is in a symmetrical position. Conversely, it is more difficult to maintain proper alignment when one arm or one leg is in motion.
Active movement exercises include sit-ups and crunches. The majority of the traditional exercises for the abdominal muscles incorporate active spinal flexion against gravity. Many people feel that these types of exercises are not functional and should be taken out of general exercise programs. While the average exerciser probably does not need to perform crunches for an extended period of time, there is no reason to omit them completely. When getting out of bed, the majority of the population will use their abdominal muscles to lift their head and to get into a sitting position before getting out of bed. Active movement exercises can also help slow the decrease in ROM that comes from the aging process. Additionally, blood flow to the spine and spinal muscles can be increased through the use of active movement exercises.
When assessing a client’s physical condition prior to designing their exercise program, the personal trainer may want to incorporate the following screening methods.
1. Spinal Flexion vs. Hip Flexion
Observe your client performing movements such as a knee lift or front kick. In these exercises, you expect to see a stable spine and movements through the hips. If the client flexes the spine while doing a knee lift or front kick, they should lower the height of these movements. Basic spinal stabilization exercises should be incorporated in their program. The picture on the left shows a client with excessive spinal flexion.
2. Spinal Flexion
Have your client flex their spine. Look to see how much movement is in the thoracic area vs. the lumbar area. In most cases, clients will require both verbal and tactile cueing to flex primarily through their lumbar spine. If they cannot flex their lumbar spine, active movement exercises to relax the lumbar extensors and to strengthen the abdominals in this area would be appropriate. The picture on the left shows moderate lumbar and thoracic flexion. The picture on the left shows increased thoracic flexion.
3. Spinal Extension vs. Hip Extension
Ask your client to perform a few back kicks. Determine if the movement is primarily through the hips or through the back. If the client extends through the back with each movement, you would want to add hip flexor stretches and spinal stabilization exercises into their program. The picture on the left shows a client extending through the back to increase the height of the back kick.
4. Spinal Extension
Ask the client to extend their spine and observe if the movement is primarily in one or two vertebral segments. If this occurs, ask them to stand tall and lift their ribcage prior to leaning back. In most cases, this will correct any hinging. The picture on the left shows hinging. Notice the sharp bend in the back at waist level rather than a gradual curve as shown on the left.
5. Spinal Rotation
Ask the client to look to one side and then the other while keeping the lower body stable. Observe if there is as much range going from one side to the other. This client has increased rotation to the left when compared to the right.
6. Spinal Lateral Flexion
Ask the client to lean to one side and then the other. They should show the most bending at the waistline. In some cases, one side will bend at the waist while the other side will show bending higher in the ribcage. The picture on the right shows lateral spinal flexion predominantly through the rib cage. The middle picture shows bending predominantly at the waist. The picture on the left shows spinal flexion through the thoracic and lumbar spine.
Spinal Stabilization Exercises
Spinal stabilization exercises are recommended for clients who are unable to maintain proper spinal alignment during functional activities. These exercises are effective for training the abdominals and back extensors to co-contract to maintain the spine in proper alignment. Because the exercises are predominantly isometric in nature, they can enhance the strength and endurance of the spinal muscles, but only in the range of motion that is used during the exercise. Stabilization exercises are not particularly effective for increasing range of motion in the spine.
There are two types of spinal stabilization exercises. In some exercises, spinal stabilization is the primary goal. In other exercises, stabilization is a necessary component of an exercise targeting other muscles. The personal trainer will usually find that it is more effective to perform exercises where spinal stabilization is the primary goal at the end of the workout session. If you fatigue the spinal stabilization muscles early in the session, you increase the risk of injury due to poor body mechanics in later exercises.
An exercise where spinal stabilization is the primary goal would be to sit on an exercise ball and lean back while maintaining proper spinal alignment with the ears, shoulders, and hips in a straight line. This position challenges the abdominal and back muscles to maintain proper alignment with increased focus on the abdominals. You can increase the difficulty of this exercise by adding light weights and performing upper body exercises. Symmetrical bilateral (both arms) movements will be easier than unilateral (one arm) movements. To further increase the difficulty of this exercise, you could also ask the client to sit on one side of the ball. The personal trainer must closely monitor the client and stop the exercise when the client can no longer maintain proper spinal alignment.
An example where spinal stabilization is a key component of an exercise targeting other muscles would be a squat. While the squat is designed to challenge muscles in the lower body, there is a high risk of injury if the client does not keep their spine in proper alignment. Observe your client from the side to ensure that they do not extend their spine during the squat. A common example of poor body mechanics is when the client extends their lumbar spine near the bottom of the squat as shown in the picture on the left. During this repositioning, there is an increased risk of spinal injury. For the general population, it is recommended that clients work in the range of the squat where they do not have to reposition through the lumbar spine.
Active Spinal Movement Exercises
Active spinal movement exercises would include spinal flexion, extension, rotation, lateral flexion and any combination of these movements. The movement that is performed against gravity will determine the muscles exercised. Active spinal movement exercises are appropriate for clients who would like to increase or maintain spinal range of motion or would like to increase the strength or endurance of these muscles. When incorporating these exercises, the personal trainer must determine whether the client should focus on increasing muscle strength or muscle endurance. For the general population, muscle endurance, or the ability of the muscles to perform many repetitions, is a nice complement to stabilization exercises. Strengthening, or the ability to perform one repetition, would be more appropriate for athletes or for physical therapists working with special population clients.
Traditional spinal movement exercises for the abdominals include sit-ups and crunches. There should be active flexion of the spine. Flexion in the thoracic area would target the abdominal muscles in that area. Flexion in the lumbar area would target the abdominal muscle fibers in the lower portion of the torso. To maximize the effectiveness of these exercises, most clients will benefit from stretching the back extensors prior to performing active spinal flexion.
Sit-ups traditionally refer to exercises that require coming to a full sitting position. Spinal flexion and hip flexion are included in this exercise. In the initial phase of the exercise, the abdominal muscles work to move the spine. In the end phase of the exercise, the abdominals stabilize the spine and the hip flexors contract to complete the sit up. Because many clients do not need the additional exercise for their hip flexors, crunches are more popular among the general population.
An abdominal crunch, when performed properly, involves active spinal flexion throughout the exercise. The client flexes their spine to lift their head and shoulders off of the floor. There has been some controversy regarding whether the lumbar spine should be “pressed” into the floor. The majority of the range of motion for spinal flexion occurs in the lumbar spine. In the supine position, flexion of these vertebrae would move the low back closer to the floor. Therefore, if the client is targeting the abdominal muscles in the lumbar region of the spine, there should be movement of the lumbar spine toward the floor. If the client is only targeting the abdominal muscles in the thoracic portion of the spine, then there will be no movement in the lumbar area.
There are several variations of abdominal crunches. By lifting on the diagonal, the obliques are targeted more effectively. When lifting the right shoulder toward the left hip, the right external obliques will work with the left internal obliques to perform the crunch. Lifting the left shoulder toward the right hip, targets the left external obliques and the right internal obliques. The obliques pull on the diagonal and form a girdle around the abdominal area.
Many clients believe that sit ups and crunches will reduce body fat in the abdominal area. Personal trainers know aerobic training is a more effective way to lose body fat. While there is no known method for spot reducing body fat, abdominal exercises can help spot tone in this area. Exercising the obliques can help slim the waistline by increasing the tone in these muscles. As they pull on the diagonal, the waistline will resemble more of an hourglass shape rather than a pillar. As with other exercises, the results will vary based on a client’s genetic potential.
Side crunches involve the client lying on their side and performing lateral spinal flexion. Many clients believe that the obliques are the primary muscles being worked in this exercise. In this position, the primary mover would be the quadratus lumborum which is located deep to the abdominals close to the spine. Because the obliques act as assistors in this exercise, it is not as effective as a diagonal lift for toning them.
Spinal extension exercises can range from prone extensions to dead lifts. The personal trainer must monitor their client, to determine whether the exercise is incorporating stabilization or active movement of the spine. If the spine is stable while the hips are moving, then the exercise is a stabilization exercise for the client. If the spine is flexing or extending during the exercise, then they are performing active movement of the spine.
Dead lifts are an obvious example of an exercise that can be used for either spinal stabilization or active spinal extension. Because it is difficult for the general population to perform this exercise well, personal trainers must use their professional judgement to determine whether or not this exercise is appropriate for their clients.
When performing active spinal extension, observe your client to ensure that they are not “hinging” or targeting the movement to one or two vertebral segments as discussed in the screening section of this article. If the load is too high or as they fatigue, they will be more likely to substitute with poor body mechanics to complete their repetitions.
When using exercise machines for active spinal flexion or extension, the personal trainer must ensure that the equipment fits their client properly. Many abdominal and back exercisers are designed to focus the movement on the lumbar spine. The machine’s pivot point should be adjusted to be at the level of the client’s waistline to maximize active movement. Some machines will adjust so the pivot point can be located at the hip to allow for spinal stabilization exercises. Again, either type of exercise can be appropriate for personal training clients. It’s important for the personal trainer to determine which type of exercise the client is actually performing. Without proper supervision, the client can inadvertently substitute stabilization for active movement or active movement for stabilization.
There is a multitude of equipment that is marketed as enhancing abdominal exercises. The personal trainer should look at several factors to determine the effectiveness of this equipment.
- Does my client need active spinal movement or spinal stabilization exercises in their workout program?
- Is the equipment properly designed for the type of exercise the client needs?
- Is my client able to use the equipment properly? Some clients may be too tall or too short. Some clients do not have the proper muscle control to use the equipment appropriately.
The purpose of a personal trainer is to help an individual assess their needs, determine appropriate goals and develop an exercise program tailored to fit the client. Because many programs incorporate abdominal and back exercises, we hope this information has helped you understand the difference between spinal stabilization and active movement exercises. By interviewing your clients and screening them for specific spinal movements, you can develop a safe and effective program that fits their needs. Due to the complexity of the spine, many articles focus on one type of client and/or a specific category of exercise. The highly trained personal trainer will understand how to interpret the multitude of information to select the most biomechanically effective choices for their clients from the wide range of exercises, techniques and equipment available today.
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