Unmasking the Deconditioning Paradigm for Chronic Low Back Pain Patients

Abstract

Physical activity is behaviour. Like all behaviours it varies widely between (healthy) people and tends to decrease as people age or develop health impairments. Physical activity and physical fitness are interrelated; physical activity influences fitness, which in turn may modify the level of physical activity. Health-related fitness consists of those components of physical fitness that are affected by habitual physical activity and that are related to health status. An adequate level of health-related fitness has been defined as a state of being able to perform daily activities with vigour, and traits and capacities that are associated with a low risk of premature development of hypokinetic diseases and conditions (Bouchard and Shephard 1994).The components of health-related fitness are defined as morphological (body composition and bone strength), muscular (muscular strength, muscular endurance, and flexibility), motor (postural control), cardiorespiratory and metabolic fitness (carbohydrate and lipid metabolism) (Bouchard and Shephard 1994; Skinner and Oja 1994). A decrease in the volume and intensity of physical activities may therefore reduce physical fitness and the capacity for physical activity, thus creating a downward spiral resulting in physical deconditioning. Physical deconditioning is defined as an integrated physiological response of the body to a reduction in metabolic rate; that is, to a reduction in energy use or exercise level (Greenleaf 2004) and affects all aspects of health related fitness.Physical inactivity and the resultant physical deconditioning have been hypothesized to be associated with both the aetiology and consequence of chronic pain (Verbunt et al. 2003). Physical inactivity, however, has not only become a topic in chronic pain management, but also in public health. In developed countries, physical inactivity is associated with considerable economic burden, accounting for 1.5–3.0% of the total direct healthcare costs (Oldridge 2008). This may give rise to the question whether patients with chronic low back pain (CLBP) exceed the general population concerning their level of physical inactivity. The extent of the problem of deconditioning in CLBP and its specific perpetuating role in chronicity still seems unclear. Despite this, the restoration of function (i.e. health related fitness) through intensive physical rehabilitation intervention continues to form the basis of many physiotherapy-guided training programmes as well as comprehensive pain management programs. This approach is in part based on the hypothesis of the ‘deconditioning syndrome’ in which deconditioning itself is seen as a factor contributing to the intolerance to physical activities and subsequent loss of function and disability in patients with chronic pain (Mayer et al. 1985, 1986; Vlaeyen and Linton 2000).A second theoretical model, in which the role of disuse is included as one of the perpetuating factors of pain is the fear-avoidance model (Vlaeyen and Linton 2000). According to the fear-avoidance model, patients may interpret their pain as threatening (catastrophizing about their pain) and this can result in pain-related fear, of which fear of movement/(re)injury is the most salient. Both this fear and expectation of adverse consequences from keep on performing or increasing activities may cause avoidance of these physical activities. In the long run, avoidance behaviour might result in disability, depression and the loss of physical activities in daily life of which loss of aerobic fitness is a consequence.Although the influence of pain-related fear on the perceived disability level has currently been confirmed based on several studies (Klenerman et al. 1995; Vlaeyen et al. 1995; Fritz et al. 2001), its presumed negative influence on a patient's level of physical activity in daily life (PAL) is still inconclusive (Bousema et al. 2007). It can even be debated whether physical deconditioning in patients with CLBP really exists (Smeets et al. 2007; Smeets and Wittink 2007; Wittink et al. 2008).In this chapter we will examine the deconditioning paradigm by summarizing the existing literature on this topic. We will start with a section on PALs in patients with CLBP. Next we will discuss studies describing the various aspects of health related fitness in patients with CLBP, followed by the latest theories regarding activity-related behaviour and the measurement problems in assessing physical fitness parameters in patients with CLBP. And finally, overall conclusions on the impact of deconditioning in CLBP will be provided.