Reproducibility of nine tests to measure spinal mobility and trunk muscle strength.

The reproducibility of nine back function tests suitable for use in the occupational health service was determined in 30 male employees. The correlation of three tests made with a tape measure--forward bending, modified Schober, and side bending--was high in both intra- and inter-observer comparisons (r = 0.82-0.96). Immediate repetition of the testing procedure improved the performance in the forward and side bending tests. The reproducibility was also good for the tests of dynamic (K = 0.57-0.78) and endurance (r = 0.90-0.96) strength of the abdominal muscles and quite good for the test of endurance strength of the back muscles (r = 0.74-0.80). The differences between the examiners must be taken into account in the modified Schober test, and in testing the flexibility of the hip flexors and hamstrings and the endurance strength of the back muscles.