Exercise- can it help the brain change itself?

Aerobic exercise on a stationary bicycle. Healthy participants will cycle at 75% of their maximal heart rate for 15 minutes in the moderate intensity exercise session and in the low intensity condition they will cycle at half this workload for 30 minutes. The results from Stage 1 will determine the exercise intensity the stroke participants will exercise at, and for how long. Each exercise session will be supervised by a physiotherapist, trained in CPR, and will be conducted at least 1 week apart. Healthy participants are involved in three sessions (control, low or moderate intensity exercise) and stroke participants in two sessions (exercise or control). The order of testing sessions in this cross-over study will be randomised within groups. The second phase of the study with people following stroke will be conducted over three sessions: a control, low intensity session at a somewhat light intensity and repetitive brain stimulation, and a low intensity session without the plasticity inducing paradigm but other tests to probe changes in cortical excitability. Participants will cycle on an exercise bike at approximately 55% age-predicted max HR for 30 mins. Each session is separated by at least one week. The brain stimulation (TMS or Transcranial Magnetic Stimulation) procedure involves sitting in a comfortable armchair with adhesive electrodes attached to the skin over the affected hand. The magnetic field stimulates the cortical cells, causing the hand muscles to fire and this EMG activity is recorded. TMS is performed before and after the exercise, and involves single pulse, paired pulse and repetitive TMS to probe cortical excitability, intracortical inhibition, and stimulation induced plasticity respectively and takes approximately 10 mins to complete single pulse TMS at 120% of resting threshold, and intracortical inhibition according to established protocols.