Objectives: To assess the effect of mild forced physical training on cognitive and locomotory behavior in old (26 mo.) mice.Design: Randomized, controlled study.Setting: Open-field in the behavioral laboratory.Participants: Sixteeen old sedentary male mice randomly assigned to one of two groups, exercise (E) or rest (R).Intervention: group E underwent treadmill running for one month at moderate intensity (belt speed = 8 m/min, 45 min, five days a week), group R was only allowed spontaneous locomotor activity.Measurements: exploratory and locomotor behavior were evaluated in an enriched environment (Ethovision recording).Results: motor patterns were significantly reduced (χ² test, p< 0.05) in the E vs R group after one month of training; exploratory patterns were not different, both groups showing modest exploratory activity.Conclusions: mild forced physical training initiated at old age may have detrimental effect on motor behavior in male mice without improving cognitive parameters.