Which unit expresses energy cost per distance per body mass in gait analysis?

Which unit expresses energy cost per distance per body mass in gait analysis?

• A. cal/kg/hr
• B. cal/kg/m
• C. cal/kg/cm
• D. cal/m/kg

Answer: (B)

The main idea is expressing energy cost of movement as energy used per distance traveled, normalized by body mass. This is captured by energy divided by both mass and distance, i.e., calories per kilogram per meter (cal/(kg·m)). That’s why cal/kg/m is the best fit: it directly communicates how much energy is needed to move one kilogram of body mass for each meter walked. Think of it as cost of transport: you want a measure that lets you compare efficiency across people of different sizes and across different walking distances. By dividing energy by body mass, you normalize for size; by dividing by distance, you normalize for how far you’ve traveled. For example, if you expend 50 kcal while walking 500 meters with a 70 kg person, the cost of transport is 50 kcal / (70 kg × 500 m) ≈ 0.00143 kcal/(kg·m). This shows why the unit uses energy per distance per mass. Per hour would describe a rate over time, not per distance, so it’s not the right expression for cost per distance. Using centimeters instead of meters changes the distance unit but is not standard in gait analysis (meters are the convention). The form cal/m/kg is equivalent in meaning (cal/(kg·m)) but cal/kg/m is the conventional presentation.

The main idea is expressing energy cost of movement as energy used per distance traveled, normalized by body mass. This is captured by energy divided by both mass and distance, i.e., calories per kilogram per meter (cal/(kg·m)). That’s why cal/kg/m is the best fit: it directly communicates how much energy is needed to move one kilogram of body mass for each meter walked.

Think of it as cost of transport: you want a measure that lets you compare efficiency across people of different sizes and across different walking distances. By dividing energy by body mass, you normalize for size; by dividing by distance, you normalize for how far you’ve traveled.

For example, if you expend 50 kcal while walking 500 meters with a 70 kg person, the cost of transport is 50 kcal / (70 kg × 500 m) ≈ 0.00143 kcal/(kg·m). This shows why the unit uses energy per distance per mass.

Per hour would describe a rate over time, not per distance, so it’s not the right expression for cost per distance. Using centimeters instead of meters changes the distance unit but is not standard in gait analysis (meters are the convention). The form cal/m/kg is equivalent in meaning (cal/(kg·m)) but cal/kg/m is the conventional presentation.