Objective     To investigate the effects of different load exercises on motor learning ability of high and low skilled movements in aged rats.  Methods     Seventy-two aged male rats (16 months old) were randomly divided into 6 groups (n=12

for each group). Four groups were trained with two load exercises of treadmill for 8 consecutive weeks. We analyzed the effects of different load exercises on eyeblink conditioned response (CR) upon a strong or weak conditioned stimulus (CS) in aged rats according to the incidence of eyeblink CR

CR peak amplitude and training times for reaching learning criterion.   Results    In the presence of weak CS

the long-term high and moderate load exercises exerted different effects on the motor learning ability. The former significantly decreased the training times (P0.05)

and improved the incidence of CR and CR peak amplitude (P0.05)

whereas the latter significantly increased the training times(P0.05)

and reduced the incidence of CR and CR peak amplitude (P0.05). In contrast

under the strong CS

both load exercises had no significant impacts on the training times

the incidence of CR and CR peak amplitude (all P0.05).  Conclusion     Differing from the negative effect of long-term high load exercise

long-term moderate load exercise is beneficial for motor learning of high skilled movement in aged rats. However

both load exercises have no effects on the motor learning ability of low skilled movement.