Bungee-powered Backpack Can Lighten Your Load, Researcher Says

Unless it has wheels thee is no way that the load is reduced at all, what this is is a suspension system. So yeah, it reduces the impact on joints, and maybe eliminates excess force due to abrupt changes in velocity of the load as the wearer jumps or lands from a jump, but it doesn't change the load. I guarantee that a hiker with 60 lbs on his/her back, would still weigh 60lbs more than his/her weight, sans load, with this fancy back back on. It is a nice attempt to spin the product. It is possible it FEELS like less of a load due to mechanisms above, but that is as much as I'd give 'em.

Please see this from NY Times

FASHION & STYLE | December 7, 2006
Ouch! My Bag Is Killing Me

It could however reduce the impulse of the force by extending the time of the impact thereby reducing the impact force, which is what I think they are referring to in this story. I think its a good idea, and probably one which has been examined in the past, however I wonder how well the load rides while running or jogging, and if it effects balance in any way?

The article does say reduces the force of the load, not the load itself.

dragging it on the ground will reduce it even further

and by far lighten the load

so assume you are running and in essance in a free fall situation for a few tenths of a second before your foot hits the ground (ignore all shock adsorbing systems internal to the backpack wearer such as shoe soles, bending fo the knees, streching or strain on bones and muscels)

Impulse= Force * time of impact = mass * delta velocity

So initial Kenetic Energy = 1/2 *mass * velocity^2 = work required to stop = -Forceaverage * distance to zero velocity

So the average force felt = (-1/2 m * v^2)/distance

From this the greater the distance the bungies can streach, the longer the impact time is extended, the smaller the average force felt on body.

If lightening your load is the net goal--just do it--Travel Light!