To determine the effects of exercise training modality on glucose tolerance in men with untreated abnormal glucose regulation, 26 untrained men (age 54 +/- 9 years; mean +/- SD) with either non-insulin-dependent diabetes mellitus (N = 8), impaired glucose tolerance (IGT) (N = 12) or hyperinsulinemia with normal glucose tolerance (N = 6) were studied before and after 20 wk of either strength training (ST) (N = 8), aerobic (treadmill walk/jog) training (AT) (N = 8), or no exercise (control group; N = 10). Plasma concentrations of glucose and insulin were measured after a 12-14 hr fast and during a standard oral glucose tolerance test (OGTT) before and after training. The ST program significantly reduced total plasma glucose area (mmol.l-1.120 min-1) under the OGTT curve (1348 +/- 251 vs 1190 +/- 329, p < 0.05), and plasma glucose levels (mmol.l-1) at 60 min (p < 0.05), 90 min (P < 0.05), and 120 min (p < 0.05) after glucose ingestion. Strength training also lowered the total plasma insulin area (pmol.l-1.120 min-1) under the OGTT curve (60082 +/- 25467 vs 46727 +/- 11273, p < 0.05) as well as plasma insulin levels (pmol.l-1) at fasting (p < 0.05) and at 90 min (p < 0.01) and 120 min (p < 0.05) after glucose ingestion. All men with IGT (four in each training group) normalized their glucose tolerance following the training. There were no significant differences in OGTT results between ST and AT and no changes were observed in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)