It's been assumed for years that a decline in physical activity leads to deconditioning and that deconditioning can result in chronic low back pain (CLBP). But studies have not been able to prove this point right or wrong. However, research does show that declining physical fitness is more likely to be related to disability.
This study of the relationship between physical fitness and CLBP included patients with subacute LBP. Subacute means the pain has been present between four and seven weeks.
Physical activity level (PAL) was measured for each person. A special device was used that recorded how much the person moved. They wore the accelerometer for seven days during their waking hours. Their PAL was measured twice: once at the beginning of the study and again at the end of one year. Decline in PAL was referred to as disuse.
At the same time, three measures of physical fitness were taken. These included body weight, body fat, and muscle strength. The data was analyzed for two groups: patients who recovered during the year and those who developed chronic LBP.
PAL increased for both groups. Strength and percentage of fat remained the same in both groups. Disuse was reported in less than half the patients. All patients with chronic LBP actually had an increase in activity levels. This showed that patients with chronic pain could cope in such a way as to maintain their daily activity at a normal level.
This study over a year period of time failed to show that deconditioning occurs as a result of chronic pain. Patients may have felt disabled, but they didn't stop doing their daily activities. Consequently, their level of physical fitness didn't change.
Eric J. Bousema, et al. Disuse and Physical Deconditioning in the First Year After the Onset of Back Pain. In Pain. August 2007. Vol. 130. No. 3. Pp. 279-286.