Chaos is coming, so you’d better train for it.

This is something I tell almost all of my clients, and it applies to everyone. The need for random, unbalanced, asymmetrical movement will present itself sometime in our future. It could be in response to slipping on a wet floor, riding a subway train, carrying a wiggly child or playing a sport. Being ready for events like these is what core training means to our clients.

Effective core training enhances the ability of core muscles to control the position and motion of the trunk relative to the pelvis and legs. The core muscles don’t get more stable, but they do achieve greater contractile ability to create stability in the lumbopelvic region. With a clear understanding of the goals of core training, we can effectively use many pieces of fitness equipment, including stability balls. By exercising with these balls, we can potentially achieve greater core muscle activation. Given that the nervous system learns with relative rapidity (compared with the time it takes to develop strength), many stability ball exercises can be mastered in a short period of time.

The use of a stability ball does not automatically mean we are training appropriately for improved function. Functional training is not defined by the equipment we choose, but by how we use that equipment. For example, someone standing on a stability ball cannot possibly be training for function as, in this situation, the demands placed on the stabilizers are so excessive that the prime movers must shift roles and act as stabilizers, the opposite of their primary function.

How can we create appropriate, progressive challenges using a stability ball? Many common stability ball exercises have similar characteristics: symmetrical positions and bilateral movements by participants. However, consider just about all the movements we do as part of our day, from carrying things and riding the bus or subway to climbing stairs and playing sports. These movements are rarely symmetrical, and the majority of them are unilateral. Knowing this can help us create stability ball progressions that address daily activities.

By employing the essential principles of physics, we can develop a diverse array of exercise options; and by introducing asymmetrical and unilateral movements, we can create new challenges. Once we begin manipulating center of gravity, torque and angular momentum, a whole new world unfolds and the possible modifications for stability ball exercises seem endless.

The Physics of Off-Center Stability Ball Exercises

The center of gravity is the imaginary point at which all of an object’s mass is said to be concentrated when acted on by gravity. In humans this point lies approximately at the second sacral vertebra, slightly in front of the sacrum when standing in anatomical neutral. Torque is a force that produces rotation about an axis, as well as a measure of a force’s ability to twist an object. Angular momentum describes the rotation of a system about an axis, or its tendency to keep rotating. It is constant if there is no change in torque.

You most likely already understand how these concepts work. For example, consider a figure skater who spins faster when the arms are drawn in. (This represents an increase in angular momentum from using shorter levers.) Another example can be found in the lateral dumbbell raise. It takes a greater amount of force to move the weight when your arms are straighter than it does when your arms are bent.

A Core Consideration

If using stability balls helps us “work our core,” it is reasonable to consider exactly what that means. Core endurance is more desirable than, and should be considered a prerequisite to, core strength and power (Comana 2007). For example, consider the multifidus muscles, which lie deep in the back and provide segmental stability between adjacent vertebrae. The multifidi are primarily type I fibers and are thus best trained with lower loads and higher repetitions (Comana 2007). The low back is the third most common area for sports injuries (behind the ankle and the knee), and trunk muscle endurance correlates with a lower incidence of low-back pain and injury (Gamble 2007).

The main features of off-center ball exercises are asymmetry and rotational motion, and these qualities align perfectly with human movement. The lower parts of the rectus abdominis and external obliques play a significant role in preventing motion and providing stability for the lumbopelvic region (Sahrmann 2001). The core muscles function as antirotators (i.e., they prevent rotation). In the exercises shown in the sidebar, note how the core muscles work either to maintain a symmetrical position while the body is off-center or to control rotation and/or the movement of an extremity in an asymmetrical position. Life and sport result in extreme loading of the spinal musculature but also in varying angles, positions and speeds of movement (Faries & Greenwood 2007).

Using Off-Center Exercises

Off-center exercises are appropriate for individuals who have already mastered many of the common stability ball exercises and have exhibited an ability to perform well in a symmetrical body position. Given the highly coordinated, asymmetrical nature of these exercises, they are best implemented before participants become fatigued.

A great benefit of these exercises is that, given the large degree of neurological stimulus and muscle activation achieved in these movements, a high volume of sets is unnecessary. This characteristic makes off-center ball
exercises a very economical choice for creating time-efficient, results-driven workout programs. When choosing
exercises, you should ask yourself two questions:

  1. Does this exercise make sense for the client’s goals?
  2. Can the client maintain stability of the lumbar spine to allow for mobility elsewhere?

Stability of the trunk allows effective movement farther out in the extremities. The human body is like a whip with one handle (the trunk) and four tails (the extremities). Stability at the “handle” during movement transfers power to the “tails.”

If you decide to introduce off-center work to your clients, you have options for creating your own variations of the “handle” or “tails.” You can either move the center of gravity away from the midline of the ball or move one or more extremities to change the effective location of the center of gravity away from its usual position. Use either of these two simple methods to create your own off-center exercises out of some movements you already use. Simply modify them using one or both of the methods, have fun and experiment.