I've looked into that. It seems to me to be about as useful as a pedometer, which will work well on level walks at an even speed.

If one stumbles a little bit, stops, climbs or drops they have that delayed reaction thing changing their center of gravity and putting strain on muscles.

Seems to me a bit like the spring-loaded trekking poles. They absorb energy when you need it, pushing off, and release it when you don't, a complete loss. Downhill they're OK, I guess, but I have elbows and knees which give me more control and are more predictable. I never hike without poles, and love 'em for downhill, but not with the springs.

Great marketing ideas, they sound good, and I'm sure work in ideal circumstances. I'll wait a while on the backpack to see what happens.

Arf