The physical and psychological factors associated with reduction of disability after aquatic exercise are not well understood. Sixty participants (30 men and 30 women; age, 50.60 [9.69] yrs; body mass index, 27.21 [5.20] kg/m(2)) with chronic low back pain were prospectively recruited. The 8-wk aquatic therapy program was carried out in an indoor pool sized 25 x 6 m, with 140-cm water depth and 30 degrees C (1 degrees C) of water temperature, where patients exercised for 2-5 days a week. Each aquatic exercise session lasted 55-60 mins (10 mins of warm-up, 20-25 mins of aerobic exercise, 15-20 mins of resistance exercise, and 10 mins of cooldown). Demographic information, disability (Oswestry Disability Index), back pain (visual analog scale), quality-of-life (Short Form 36), abdominal muscular endurance (curl-up), handgrip strength, trunk flexion and hamstring length (sit and reach), resting heart rate, and body mass index were outcomes variables. Significant correlations between change in disability and visual analog scale (at rest, flexion, and extension), curl-up and handgrip (r ranged between -0.353 and 0.582, all Ps < 0.01) were found. Changes in pain and abdominal muscular endurance were significant predictors of change in disability after therapy.