Stimulation of the motor cortex using transcranial magnetic stimulation (TMS) and electromyographic (EMG) recordings has shown corticospinal excitability to be depressed following exercise (Brasil-Neto et al., 1994). When the exercise is exhaustive, depression of motor evoked potentials (MEPs) can also be seen in homonymous non-exercising muscles but appears to have little measurable effect on performance (Humphry et al., 2004). We have now induced central fatigue in non-exercising muscles and measured its influence on limit of endurance time (LOET). With local ethical approval and informed consent, ten healthy male volunteers (right-handed, aged 20-24 years) visited the laboratory for two sessions one week apart and bilateral surface EMG recordings taken from biceps brachii (BB) muscles. In session 1, a 4kg weight was strapped to the left wrist and subjects performed left-armed biceps curls to exhaustion, in time with a tone repeating at 1.5 seconds interval. Time to exhaustion (without prior right arm exercise) was measured as the LOET. In session 2, a 5kg weight was strapped to the right wrist and subjects performed right-armed curls to exhaustion. Subjects were given five minutes rest before the 4kg weight was attached to the left wrist and left-arm curls were again performed to exhaustion and a post-exercise LOET was recorded. TMS was applied using a MagStim 200 stimulator connected to a 9-cm circular coil centred over the vertex and MEPs were monitored bilaterally during both sessions. In session 1, mean (±SEM) MEP areas were significantly (P 0.05). This study has confirmed that, following exhaustive levels of exercise, depression of MEP responses occurs in the non-exercising as well as the exercising BB. The LOET fell in the non-exercising BB. We conclude that reduced tonic corticospinal excitability may result in a reduced LOET.