Why Massive Amounts of Repetition Per Session, Not Just Number of Sessions, Are Required For Neuroplasticity
Neuroplasticity is the brain’s ability to change neuronal circuits. Animal studies1 in neuroplasticity have shown that 400 to 600 repetitions per day of a challenging functional task, such as fine motor grasping, are required before the brain reorganizes to accomplish the new task. Gait evidence in animal studies show that approximately 1,000 – 2,000 steps per session are required to improve hind-limb stepping and step quality.
After stroke in human subjects2, increased amounts of task repetition have been shown to cause cortical changes and functional improvement. For example, human subjects with impaired grasp-and-release after stroke performed more than 100 repetitions per day (1,200 total) of a finger-tracking exercise and demonstrated significant cortical reorganization and functional improvements.
Thus, clearly, one item of focus for rehabilitation professionals should be the number of reps and type of activity performed in each session. Current research, however, shows that most therapy sessions do not contain the proper amount of repetitions per session to cause actual changes in the brain. Typical therapy sessions, whether physical, occupational, speech, or behavioral, last about one hour per session with the therapist employing various tasks and exercises throughout the session.
Are Therapists Doing Enough Per Session?
In a recent study published in the Journal of Rehabilitation Research & Development, researchers quantified the number and types of activities performed by patients with traumatic brain injury (TBI) and stroke in their therapy sessions3. Not surprisingly, the number of repetitions observed for upper extremity work was between 40-60 repetitions per session – far below the hundreds required for neuroplasticity.
The Movement Toward “Massed Practice”
Because individual therapy sessions infrequently provide sufficient repetitions to maximize neuroplasticity, there is a movement in the physical therapy community now toward intensive “massed practice” – where sessions are clustered back-to-back with little or no rest in between sessions. Such practice has been effective in recovery of balance, gait, and ambulation after stroke4,5.
For more information on massed practice post-hemispherectomy, see Intensive Mobility Training.
How many repetitions per session is enough? The evidence across animal and human literature suggests that the number is in the hundreds for upper extremity work and in the thousands for gait steps.