An evaluation of four different measures of abdominal muscle strength: patient, order and instrument variation.

We compared 4 measures of abdominal muscle strength in 24 male subjects aged 20-52 years, 12 without low back pain (LBP) and 12 with LBP. The manometer to knee and manometer to sternum methods involved 2 positions of testing abdominal muscle strength using the adapter sphygmomanometer, a 3rd method was a scheme of graduated sit-ups, and the 4th had the sphygmomanometer bladder replaced by a disposable plastic tube and the subject blowing into the manometer. Order of methods was controlled with knee 4 x 4 latin squares. Analysis of variance showed that order of measurement was not significant [F (3,60) = 0.24, P2 = 0.725], but methods were different [F (3,60) = 86.80, P2 less than 0.01], and subjects without LBP had higher abdominal muscle strength than subjects with LBP [F (1.60) = 89.29, P2 less than 0.001]. The manometer to knee and manometer to sternum methods were equally sensitive and more sensitive than the graduated sit-up and blow into manometer methods. The manometer to sternum method was best as it was not painful and exercised the abdominals well.