The habit of shaking one’s leg while sitting, often done unconsciously, is a subtle movement that prompts a common question: does this small, repetitive action actually burn a meaningful amount of energy? This motion is a form of spontaneous physical activity, and while it may seem insignificant, it represents a slight increase in energy expenditure compared to sitting completely still. Understanding the metabolic impact of this movement requires looking at specific scientific data and the broader context of how the body uses energy throughout the day.
The Specific Calorie Expenditure
The act of leg shaking, or fidgeting, results in an extra energy expenditure over the baseline rate of sitting motionless. Studies measuring this type of movement have found that fidgeting while seated can increase the metabolic rate by approximately 54% compared to lying down at rest. This increase represents the additional energy needed to power the small, repetitive muscle contractions involved in the movement.
Translating this percentage increase into a specific hourly calorie number places the additional burn in a measurable range. For an average adult, sustained leg shaking over a one-hour period typically burns an additional 10 to 30 calories beyond what is burned by sitting still. For example, if a person burns about 70 calories an hour while sitting quietly, they might burn 80 to 100 calories an hour while actively shaking their leg. This signifies a consistent, albeit minor, departure from a completely sedentary state.
The Science Behind Fidgeting Non-Exercise Activity Thermogenesis
The energy spent on leg shaking falls under the scientific category known as Non-Exercise Activity Thermogenesis, or NEAT. NEAT is the energy expended for everything a person does that is not sleeping, eating, or structured exercise. This includes a wide range of movements, such as walking, typing, yard work, and spontaneous actions like fidgeting.
Fidgeting is a component of a person’s total daily energy expenditure (TDEE). Even trivial physical activities can substantially increase the metabolic rate, and the cumulative impact of these actions throughout the day is significant. NEAT can account for a vast majority of a person’s non-resting energy needs, and differences in NEAT can vary dramatically between individuals. Some research suggests that the difference in NEAT between two people of similar body size can be up to 2,000 kilocalories per day, mainly due to lifestyle and occupational differences.
NEAT is regulated by the body’s energy balance. Studies have shown that NEAT can increase when a person is overfed, suggesting it may be a mechanism the body uses to resist weight gain. Conversely, NEAT tends to decrease when a person is underfed. This indicates that the subtle energy expenditure from movements like leg shaking is part of a larger physiological response to maintaining body weight.
Variables That Determine the Final Number
The precise number of calories burned from leg shaking is not a fixed value, but rather a range determined by several individual variables. Primary among these factors is a person’s body mass. Individuals with a greater body mass require more energy to move that mass, even in a repetitive, small motion, resulting in a higher overall calorie expenditure for the same activity.
The intensity and vigor of the movement also directly influence the final calorie count. A slight, intermittent foot tap burns significantly fewer calories than a sustained, rapid, and forceful leg bounce. The speed and amplitude of the muscle contractions dictate the energy demand placed on the leg muscles.
The duration and consistency of the movement are also crucial for calculating the hourly total. The hourly estimate assumes the fidgeting is sustained for the entire 60 minutes. If the leg shaking is intermittent, the final number will be much lower. These variables explain why precise calculation is difficult for the average person and why scientific studies report a wide range of values for fidgeting.