Shadows and pumps

On Monday we went shopping at the sports shop and as usual came away somewhat poorer.
One of our purchase was bungypumps; a 4 kilo version for Janet and a 6 kilo version for me.
So what do they do? In Nordic walking you walk with the help of two poles, rather like cross-country skiing poles. Not only your legs are working, even your upper body is pushing you along, taking some of the load. You tend to walk faster, more energetically and with longer strides.
Bungypumps are a deliberately inefficient form of nordic pole. As you push you must first compress the spring (that's the 6 kilos) and only then does the pole push you along. So basically you burn more energy for the same distance walked, and you work the upper body, especially the shoulders, even more. The spring also acts as a shock-absorber so there's no shock to the shoulders and arms as there can be with normal nordic poles.
We'll have to see how it feels.