A new motor research has said that there are significant differences in how the body moves when performing similar activities.
In the study, co-authored by Howard N. Zelaznik, a Purdue University professor of health and kinesiology, the research team wanted to know if discrete skills, which have a definite beginning and end, such as typing, are controlled identically to continuous skills, such as scribbling, which do not have such a clear beginning and end. Or, are continuous movements composed of a series of discrete movements that are knotted together?
"In language we start with letters that lead to syllables that lead to words, and we use grammar to put everything together. One of the fundamental questions in motor control is whether there is an alphabet that guides movement," said Zelaznik.
"We wanted to know if discrete skills, which have a definite beginning and end, such as typing, are controlled identically to continuous skills, such as scribbling, which do not have such a clear beginning and end. Or, are continuous movements composed of a series of discrete movements that are knotted together? On both accounts, the answer is no," he added.
"Potential implications for physical therapy and humanoid robotics are immense," Zelaznik said.
"This work shows that discrete and continuous movements must be considered separate classes of movement," he added.
For example, in a physical therapy setting many skills are taught discretely first, such as stepping or bending a joint, and then the patient is told to perform continuously, such as walking. Humanoid robots, which resemble people and walk upright, often control movements as a series of discrete actions.
"Prior to this work, the basis for explaining the relationship of these skill sets was based upon inferences from empirical movement data," Zelaznik said.
"In our research, we mathematically and computationally demonstrate that the discrete model cannot be morphed into a continuous model and vice versa. Discrete models cannot produce fast repetitive movements, which shows us there is a difference in how the brain controls the body's slightest action," he added.
In the research, the models were based on the assessment of eight study participants who performed timed finger-tapping tasks to match the tempo produced by a metronome. There were three conditions: moving as fast as possible, moving as smoothly as possible or moving naturally with no instruction. While the speed was manipulated, the participants' movement trajectories were recorded.
The study is published in the Public Library of Science's Computational Biology online journal.