Chapter 7: Training for Mobility 160 simple method of assessing the current position of your spine and affording feedback as to what adjustments (if any) need to be made. The belly-whack test is another simple method of assessing posture. In essence, proper posture requires a certain amount of tension (albeit modest) from the abdominal muscles in order to maintain a neutral spine. Being able to take a quick whack to the belly ensures you have enough abdominal tension in order to support good posture. Figure 7.14 depicts the proper set-up and execution of both the twohand rule and belly-whack test. Figure 7.14. Two-Hand Rule (Left) and Belly-Whack Test (Right) Low Back Pain Prevention and Treatment According to Cady (2016), nearly every American adult has some form of spinal abnormality. In fact, just as with graying hair and wrinkles, changes to the spine (i.e., vertebra and intervertebral discs) are a natural part of the aging process. For example, the water content of the intervertebral discs gradually decreases with age (Zatsiorsky & Kraemer, 2006). Even so, these abnormalities of and age-related changes to the spine do not necessarily guarantee that an individual will experience low back pain. Figure 7.15 shows the relationship between age and the percentage of individuals with a documented disc abnormality but no reported back pain (as depicted via magnetic resonance imaging (MRI)). As shown in the figure, by the age of 50 nearly 80% of adults have some degree of disc degeneration and 60% have a disc bulge.