Chapter 7: Training for Mobility 157 until there is noticeable improvement. In some cases, this may mean spending up to 10 minutes in each position. A sufficient hold duration is necessary in order to stimulate the Golgi tendon organ (a proprioceptor located adjacent to the myotendinous junction that detects changes in muscle tension and when stimulated produces muscle contraction) (Figure 7.5), which in turn allows the muscle to relax and lengthen. As previously mentioned, poor flexibility is more likely a factor of CNS inhibition than it is muscle fiber length. According to Page et al. (2010), muscle imbalances are among the top culprits for musculoskeletal pain, especially in the back, neck, shoulder, hip and knee. These imbalances can lead to patterns of tightness and weakness that can compromise joint function. Page et al. (2010) classifies muscles as either tonic or phasic. Tonic muscles are primarily flexor muscles and tend to tighten with age; whereas phasic muscles are primarily extensor muscles and tend to weaken with age. Examples of tonic muscles include the hip adductors, hamstrings, iliopsoas, and piriformis. Examples of phasic muscles include the quadriceps, glutes, and rectus abdominis. To correct imbalances, Page et al. (2010) recommends performing regular flexibility training to help lengthen the tonic muscles and regular strength training to help strengthen the phasic muscles. In terms of precautions, it is important not to bounce (e.g., ballistic stretching) or force a movement when stretching. Immediately stop stretching if you experience any sharp or shooting pains. Additionally, stretching is not recommended if you have sustained a recent injury, are within 8-12 weeks post fracture, and/or have acute inflammation in the joint or surrounding tissue. Low Back Pain Causes According to one online poll, it is estimated that 80% of American adults will suffer from back pain at least once in their lives (Peterson & Rittenhouse, 2019). Additionally, it is estimated that 20% of adults under the age of 60 suffer from chronic back pain (Cady, 2016). Low back pain can be caused by many factors. Some of the prominent causes of low back pain include bulging or herniated discs, spinal stenosis (abnormal narrowing of the spinal canal), piriformis syndrome and/or arthritis. In addition to the aforementioned causes, low back pain can also be self-induced. For example, some of the common agitators of low back pain include prolonged sitting / standing, certain sleeping positions and poor posture. Keeping the spine in a flexed or overextended position for a prolonged period of time can lead to or exacerbate low back pain. Figure 7.12 depicts the proper and improper body position for various daily activities.
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