Stability ball training has been used for many years to improve spinal stability and to reduce the risk of back pain. It is frequently employed in both the physical therapy and fitness settings. From an anatomical perspective, clinicians link the mechanisms of spinal stability to the trunk muscles, which are often grouped into two categories: the global muscle system and the local muscle system.
The global muscle system includes the larger extrinsic muscles of the trunk, such as the internal and external obliques, the rectus abdominis and the superficial (outermost) lower-back muscles. This global system of muscles is involved with spinal-column movement and the load-bearing tasks of the spine.
The local muscle system refers to the smaller and deeper muscles of the spine. Although they produce small forces, these intrinsic muscles are meaningfully involved in postural control of the spine, maintaining the integrity of the spinal column. Muscles of the local muscle system include the multifidus and the transversus abdominis.
To date, few investigations have examined the benefits of stability ball training on spinal stability. Most of the limited research that does exist has focused on the global muscle system through strength measurements and surface EMG (electromyogram) recordings. However, these investigations have not adequately determined whether (or how much) the intrinsic muscles contribute to improvement in spinal stability. This study was designed to answer that question by examining the effect of stability ball training on static back endurance and side bridge tests in sedentary men and women.
Subjects. Twenty healthy, but relatively sedentary, male and female volunteers (29–49 years of age), who worked 40–60 hours per week, participated in this study. Before it began, each subject provided demographic information (e.g., exercise habits, health history, occupation) and completed informed-consent and PAR-Q forms. On average, subjects completed 4 hours of recreational activity per week. None of the participants had any back pain that would limit bodily movement. Subjects were randomly assigned to either an experimental group or a control group. Both the experimental and control groups were permitted to continue with their regular cardiovascular and strength routines, as it was felt that these types of exercise did not have a direct influence on the endurance of the intrinsic trunk muscles. However, all subjects were asked to refrain from doing any extra spinal stability training during the 10-week study.
Tests and Training. The static back endurance and side bridge tests were used to measure spinal stability during both pre- and posttests. The static back endurance test assessed and recorded the amount of time each subject could maintain a horizontal position while lying prone on a flat bench (on hips with trunk unsupported) with ankles anchored beneath a pad. The authors cited research indicating that performance (or perhaps “poor” performance) on this test is a good predictor of future back pain. The side bridge test required each subject to maintain a side-lying position on the floor (plank position on the side, with extended legs), while propped up by the forearm closest to the ground. Each subject self-selected his or her “preferred” side for this test; again, the amount of time each subject could maintain this position was recorded. The researchers confirmed that both these tests are routinely used for back function and dysfunction assessment in clinical settings.
The Stability Training Program. The experimental group participated in 30-minute stability ball exercise sessions twice a week for a 10-week period, whereas the control group completed only the pre- and posttests. Each subject in the experimental group was provided with a stability ball (either 55 or 65 centimeters) that allowed for achieving ≥90º range of motion at both the hip and the knee. The exercise program consisted of static (no flexion and extension of the spine) spinal stability exercises (see Table 1 for the exercise progression during the 10-week program). The authors explained that this was done to better assess the outcome results for the smaller intrinsic spinal muscles, which are very involved in spinal-column stability.
Study Design. Early training sessions provided subjects with body control suggestions on how to obtain neutral spine during all the exercises. Subjects performed an instructor-led, 5-minute warm-up and did stretching exercises during and after each session. The researchers progressed the difficulty of the training program by
1. increasing the number of repetitions (building from 10 to 20);
2. increasing the complexity of exercises (adding opposing limb movements);
3. increasing the duration of static exercises (from 10 to 60 seconds);
4. increasing the exercise difficulty by changing the movement levers (from short to long)
5. altering the base of support (from more support to less); and
6. increasing the tempo of limb movement on some exercises (from 40 to 70 beats per minute).
As can be seen in Tables 2 and 3, the experimental group showed significant pre- to posttest improvements on the static back and side bridge tests, compared to the control group.
This study clearly shows the positive effects of stability ball training on increasing spinal stability, as measured by the static back endurance and side bridge tests in men and women. More specifically, stability ball training that incorporates static-hold exercises clearly improves the endurance capacity of the deep intrinsic muscles of the spine, which contribute considerably to spinal stability and postural control during prolonged sitting. Prolonged sitting is commonly recognized as a contributing cause of low-back pain.
The results of this study show the encouraging effect of stability ball training on improving spinal stability. This investigation incorporated static-hold stability exercises to adequately test the endurance function of the intrinsic muscles of the spine and clearly showed a significant change after 10 weeks of training. Personal trainers and fitness professionals should be pleased that research is starting to provide excellent scientific validity for the structured stability training now enthusiastically and regularly employed in fitness programs.
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