Altered muscle strength and flexibility among a subgroup of women with chronic nonspecific low back pain: Cross-sectional case-control study.

To compare muscle strength and flexibility among a subgroup of women with extension-related chronic nonspecific low back pain (CNLBP) with healthy controls. In this case-control study, 32 subjects with and without extension-related CNLBP were tested (n = 16 in each group). Gluteal, abdominal, paravertebral, and hamstring strength, along with hip flexor flexibility and hamstring flexibility were compared between groups. Data were analyzed using the Mann–Whitney test (p <.007). The CNLBP subgroup displayed significantly lower strength of all muscles analyzed (p <.007), with the exception of gluteus medius. The flexibility of the hip flexors and hamstrings were not significantly reduced among the women with CNLBP (p >.007). The present study showed that alterations in muscle strength, but not flexibility, partly consistent with those previously hypothesized but not objectively reported, were present among a subgroup of women with extension-related CNLBP. These results may have implicatio