This study compares the forward reach score, spine and pelvis postures, and hamstring criterion-related validity (concurrent validity) between the sit-and-reach test (SR) and the back-saver sit-and-reach test (BS). Seventy-six men (mean age ± SD: 23.45 ± 3.96 years) and 67 women (mean age ± SD: 23.85 ± 5.36 years) were asked to perform three trials of SR, BS left (BSl), right (BSr), and passive straight leg raise (PSLR) right and left (hamstring criterion measure) in a randomized order. The thoracic, lumbar, and pelvis angles (measured with a Uni-level inclinometer) and forward reach scores were recorded once the subjects reached forward as far as possible without flexing the knees. A repeated measure ANOVA was performed followed by Bonferroni's post hoc test. Pearson correlation coefficients were used to define the relationships between SR and BS scores with respect to PSLR. In both men and women, the thoracic angle in BS was significantly greater than in SR (p<0.016). However, no significant differences were found between the tests in lumbar angle, pelvic angle, and forward reach scores. The concurrent validity of the forward reach score as a measure of hamstring extensibility was moderate in women (0.66 0. 76) and weak to moderate in men (0.51 0.59). The concurrent validity was slightly higher in SR than in BS, although no significant differences between the correlation values were observed. There were significant differences in the thoracic angle between the SR and BS, but not in the forward reach score. There was no difference in concurrent validity between the two tests. However, the traditional SR was preferred because it reached better concurrent validity than the BS.

• Previous studies have analyzed the validity of sit-and-reach and back-saver sit-and-reach tests as criterion measures of hamstring muscle extensibility. The differences in the position of lower limbs between both the tests could influence the spinal and pelvic angles and forward reach score.

• Forward reach scores, lumbar and pelvic angles showed no significant differences between the tests, while lower thoracic angle was found in the sit-and-reach. However relatively large changes in thoracic angle were required to be confident true difference had occurred.

• The sit-and-reach test is the preferred test over the back-saver sit-and-reach as measure of hamstring muscle extensibility. The concurrent validity of sit-and-reach and back-saver sit-and-reach in men is compromised, and hence, other tests should be considered to evaluate the hamstring extensibility.