The present study was undertaken to analyze the acute and chronic effects of exercise on insulin sensitivity in elder diabetic patients using a horseback riding therapeutic equipment (Joba). The acute effects of exercise were examined by means of a single session of Joba riding that lasted for 30 min. The average glucose infusion rates (GIR) before and during exercise were regarded as an index of the insulin action in peripheral tissues by the euglycemic clamp. The chronic effects of exercise were studied by training the elder diabetic patients for 12 weeks using the Joba apparatus. The insulin sensitivity was determined pre- and post-training by a 90 min euglycemic clamp. In the acute study, average GIR during exercise was significantly higher than pre-exercise (7.8+/-0.4 versus 5.2+/-0.3 mg kg(-1)min(-1), P<0.01) and average GIR during recovery decreased to almost the same levels of pre-exercise (5.0+/-0.4 mg kg(-1)min(-1); P<0.01). The 12-week training resulted in a significant increase in the steady-state GIR (from 5.2+/-0.3 to 7.4+/-0.8 mg kg(-1)min(-1); P<0.05). The steady-state GIR after 12 weeks of detraining returned to pre-training levels (5.3+/-0.5 mg kg(-1)min(-1); P<0.05). In elder diabetic patients, mechanical horseback riding enhances the insulin-induced glucose uptake.