An excerpt from the VeloPress book "Crosstraining for Endurance Athletes: Building Stability, Balance, and Strength" by Raul Giusado


You can't shoot a cannon from a canoe.  -Paul Chek (on the importance of core strength in athletics)

The trunk or core of your body is the point from which your extremities (arms and legs) are connected. When you engage in physical activity of any kind, the platform for your strength, power, and control comes from your core. Everything you do-from reaching into the trunk of your car to pick up a heavy bag of groceries, to leaning over the sink when you brush your teeth-involves the core musculature to some degree.

Trunk stability refers to the ability to coordinate the recruitment of the musculature that attaches to your spine and pelvis to maintain optimal postural positions during movement. Dynamic balance sports such as skiing, snowboarding, and surfing require a high degree of trunk stability to control the body's center of mass and to make it easier for lower-body stabilizers to react to terrain and gravitational forces. And, efficiency, injury prevention, and force production in endurance sports such as running, cycling, and swimming are all dependent on the ability to stabilize the spine and pelvis for hours at a time.

TRUNK STRENGTH AND STABILITY ROLES
Transverse abdominis-helps stabilize center of mass at the lumbar spine
Internal and external obliques-aid in lateral flexion and rotation of the spine and act as stabilizers of the spine in these two planes
Rectus abdominis-are responsible for spinal flexion and provide fore and aft spinal stability
Erector spinae-are responsible for spinal extension and provide fore and aft spinal stability
Lattisimus dorsi-provide pulling strength for the arms and act as shoulder and torso stabilizers
Rhomboids-are responsible for shoulder retraction, shoulder stability, and thoracic spine stability
Pectoralis-provide pushing strength for the arms and act as shoulder and torso stabilizers
Gluteals-provide lower-body strength and act as stabilizers of the pelvis
Hip flexor complex-are responsible for hip flexion and hip joint stability
Hip abductors and adductors-are responsible for hip abduction and adduction and hip joint stability
Biceps femoris-provide pulling strength for the legs and act as pelvis stabilizers

Developing a stable trunk requires strong core musculature. However, many athletes in various sports have trunk strength but are not stable. This is because stability is dependent on the ability of the nervous system to recruit these muscles during movement. Moreover, most athletes are training their core musculature in isolation opposed to integration. Endurance athletes need to incorporate trunk stability training into their weekly programs to eventually teach these muscles to contract and effectively stabilize the pelvis and spine during their sport.

ANATOMY OF THE TRUNK
The most important trunk muscles are the transverse abdominis (innermost abdominal wall), the internal and external obliques (side abdominals), the rectus abdominis (large outer muscles of the abdomen), erector spinae (smaller back musculature), the lattisimus dorsi (large back musculature), the rhomboids (smaller back muscles between the shoulder blades), the pectoralis (chest), the gluteals (buttocks), the psoas, rectus femoris, and tensor fascia latae (commonly known as the hip flexor complex), the hip abductors and adductors (outer and inner thighs), and the biceps femoris (hamstrings). Optimal strength, power, and balance require that these muscles work together to stabilize the core when we move.

POSTURE AND NEUTRAL SPINE
The term neutral spine refers to the position in which all the vertebrae are level in relation to one another. The spine runs from your head to your pelvis and has a natural curvature.

The spine has three major portions. The cervical spine is essentially your neck, the thoracic portion is where your ribs attach, and the lumbar section is the lower back. The spine curves toward the rear of the body in the upper back and curves forward at the lumbar region. When it's in this neutral position, it is best able to disperse loads, provides a strong foundation for movement, and places the least amount of pressure on vertebral discs. The vertebral discs are made of soft tissue and act as mini-shock absorbers in our back. If we're not in a neutral spine position, the vertebrae may be squeezing a disc, making it more prone to injury during movement. As a result, it's important that we learn how to find and maintain this neutral spine position when we sit, walk, run, lift, swim, ride, and perform any movement that may involve loading or rotation of the spine.

Many of us have developed poor postural habits and positions over the years that our tendons, ligaments, and muscles have become accustomed to. Breaking such habits may take a great deal of stretching muscles that are tight, usually the chest musculature, and strengthening muscles that are weaker, generally the muscles of the back. Little did your parents know that reminding you not to slouch would not only make you look more respectable but would help keep your back healthy as well as improve your performance!

TRAINING TRUNK STABILITY
We can improve our trunk stability by increasing our awareness of how these muscles function in various movements and making an effort to involve those muscles when we crosstrain. We will discuss specific exercises that accomplish this goal very effectively. Another way to improve trunk stability is to integrate these muscles when we are strengthening other muscles in our lower and upper body. When you integrate coremusculature into your resistance-training program, you're teaching the body, and more specifically the nervous system, to recruit these muscles when performing a variety of movements. As a result, you'll be able to prevent injury, move more efficiently, and create a more stable base from which you can exert your strength and power during all kinds of physical activities.

This approach is also known as functional training because you're preparing the body for realistic movements that you make in your sport and in everyday activities. For example, the leg press machine that can be found in nearly every large gym in the world is great for building quadriceps (thigh muscle) strength. However, unless you're a circus performer (you know, the guy who lies on his back and juggles large barrels with his feet), it's not very functional. A more functional lower-body exercise, for most activities, would be to perform a standing single-leg squat while holding a medicine ball, dumbbells, or a weighted plate.

Functional resistance training can also greatly reduce an athlete's risk of injury. For example, it's common to see ankle and knee injuries in sports like basketball and tennis that involve quick direction changes. Oftentimes these injuries could have been avoided by preparing the body for the demands of the sport by improving overall strength and stability in all planes of movement. Endurance athletes experience repetitive or overuse type injuries because they tend to overlook the need for training their bodies in side-to-side or rotational movements. Failure to incorporate such movements into your training program can cause muscle and postural imbalances. Ultimately, we want to improve our strength in all planes of movement in order to increase power and efficiency through improved balance and stability.

What does this have to do with your trunk? Well, to perform a single-leg squat while holding dumbbells, with proper form, your core musculature has to be recruited to keep your pelvis level, maintain your posture, and stabilize your center of mass so that you don't fall over. In other words, the functional exercise will not only fatigue the quadriceps just as effectively as the leg press machine but also train all of the stabilizing muscles of the trunk, pelvis, hip, knee, and ankle at the same time. I am not proposing that you stop using the leg press machine or any other stable machine that was developed to emphasize and strengthen a particular muscle. I am merely stressing the need for incorporating the concept of integration into your resistance training.

By improving the ability to stabilize the spine and pelvis, you accomplish three main things. First, trunk stability protects the spine from trauma. Holding the spine in a biomechanically advantageous position and activating abdominal and back musculature during movement can prevent a variety of rotational and impact injuries to your spine and help keep your back healthy for life.

Second, as mentioned previously, trunk stability improves balance. Balance is enhanced by joint stability. The better you can stabilize every joint in your body, the better you'll be able to control movement. Human center of gravity or mass is slightly below and behind the navel. Thus, the better we can stabilize that point, the more effectively we can make subtle balance adjustments in our extremities. Most important, a stable core will make it easier for other joints to handle stresses and as a result help prevent injury.

Third, trunk stability increases strength and power. It's necessary to provide a solid platform from which the muscles of the extremities can maximally produce force. A strong and stable trunk allows a muscle to devote more energy to movement and less energy acting as a stabilizer. The more complex or powerful the movement, the more important trunk stability becomes.

Visit InsideTri.com next week for "Trunk Stabilty: Part Two" to learn about developing core strength and the most neglected part of the trunk.

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