Strength balance and low back pain.

Low back pain is a common complain. About two thirds of an adult population had, have or will suffer at least once during their life (Biering-Sorensen 1987, Waddell 1998). Few back disorders have an organic support and thus must enter specific treatment (red flags). On the other hand, a large majority of complains are without clear etiology and thus lack efficient treatment and are at high risk of chronic development. A huge number of studies have dealt on the relationships between low back pain and back function (Mayer 1987, Granata et Marras 1995), clinical observations (Burton et Waddell 1998, Deyo et Weinstein 2001), individual factors (Grombez et al 1999, Nussbaum et al.1997), occupation (Marras 2000). Through functional index, the ratio between trunk flexion and extension strengths has been the most advocated (Mayer 1987). However, few had been done on studies of the incidence of back function on back pain in large healthy populations.
Our objective is to relate the balance of grip to trunk strengths in a large healthy working population. At our knowledge this balance has never been established on a large number of subjects, while the ability to exert higher forces with the arms then with the trunk could be an explanation of back injuries.