Mastery of a skill comes only with consistent and deliberate practice over time. But a new study suggests that practice serves another crucial purpose as well – though this variety of practice comes after the skill is already mastered.
The study, led by University of Colorado-Boulder Assistant Professor Alaa Ahmed, focused on how research subjects learned particular arm-reaching movements using a robotic arm. Participants used a joystick on the arm to control a cursor on a computer screen. Each person started from a set position to reach for a target on the screen, using both inward and outward arm movements.
Participants had to exert more energy in some of the arm movements when the robotic arm created a “force field,” making subjects push harder as they steered the cursor toward the target.
The test subjects first performed a series of 200 reaching trials with no force field, then two sets of 250 trials each when pushing back against the force field. The experiment ended with another 200 trials with no force field. A metronome was used to signal the test subjects to move the robotic arm every two seconds toward the target during the trials.
The first result was, as predicted, that with repeated practice the participants learned how to move the robotic arm against the force fields and reach the target with fewer and fewer errors, until they were nearly error free.
The next result, also predicted, was that even after participants had significantly reduced errors, more practice also reduced how much energy their muscles required to complete the tasks.
The clincher result, however, was that even after muscle activity stabilized (in other words, participants’ muscles reached an optimum energy consumption point that required less energy to complete the same tasks), energy consumption still decreased with more practice. By the end of the study, participants who had mastered the skill and continued to practice experienced a 20% reduction in energy consumption.
That result suggests something new about how bodies exert energy. Conventional thinking is that “metabolic cost” is a direct result of biomechanics (muscle activity); to become more energy efficient, you train your muscles to accomplish more with less.
But this study suggests that there’s a wild card in the energy consumption game: More efficient thinking. Neural processing and biomechanics appear to both be responsible for energy efficiency. As participants’ thinking improved with practice—even after optimal muscle function was achieved—the less energy they expended.
The takeaway -- energy efficiency is a mind-muscle combo, even for top performers.
The study was published in the Journal of Neuroscience.
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