1. The problem statement, all variables and given/known data If a 70kg man is running 3 m/s horizontally, how many watts is he consuming? 2. Relevant equations W = N-m/s N = mass*acceleration 3. The attempt at a solution I would assume that in order to get the force in N one would use the gravitational constant of the Earth, but the man is moving in a horizontal line. Regardless, he is technically using work to move 'up' since his center of mass is going slightly up and down. How do I account for this, however? Thank you.