Thank you Dr Annear for your input. Am looking at evaluating energy cost as solely an output of gait using energy relationships with the basal gait parameters and not as a product of physical activity(walking).

Nice question and I sharing my view...

I not a from physics or from any modern medicine stream...

In our Ayurveda literature we consider every human being has his own unique identity and each individual is different from each other.

We called it as Prakruti (Basic constitution of each individual). And this Prakruti decides his Structural-Physical and mental abilities in future.

We consider Sahas (Extreme Courageous physical activity) is responsible for debilitating disorders including neuro-spine diseases.

So it all depends on the physical strength or we call it as Sharira Prakruti (Human body Constitution) of each individual and we may can adopt a appropriate range according to specific age group for 'energy cost and relationship with gait performance'.