I can buy the extra energy cost for walking because gravity is putting some force on there and you'd expend energy to counterbalance it versus just letting the ground push back.
But your fingers have exactly as much force as you put behind them yourself, so I don't know what's up with the finger-slammers. They totally exist though.
I was probably reaching with the foot-stompers comparison. Seems like a similar result, but the causes may well be unrelated.