Lame... or lazy?

Coffee Time Challenge: Sponsored by Micro-Epsilon

This month's coffee time challenge asks you to think about the effort it takes to move about. We are not looking at travelling great distances, or even anything that would make automated transport essential. This is more the 'pop round the corner to the shops' type distance. Are you using up too much energy to make the journey? If the walk was less demanding would it mean the Mars bar reward was optional rather than essential? Or would simple fatigue reduction for those that walk a lot – and we do typically use up more energy walking than any other daily activity – be benefit enough.

More importantly, beyond appeasing the lazy, there are very real applications where walking aids can offer very real benefits. Someone recovering from a stroke is a prime example of an individual who may need the exercise and discipline of walking, but could do with a helping hand. Or foot.

There may be other temporary conditions concerning the joints, tendons or muscles in the lower leg that could also be helped by a walking aid.

The challenge then is to design a device that will take some of the strain away from walking. Typically we have a solution in mind. It requires no additional power, all movement and power is self-generated. It must also be comfortable and easy to use. To be stylist might be, literally, a step too far.

As always, the idea we have in mind will be published next month but if you have any entertaining and interesting solutions then feel free to leave a comment on the Coffee Time Challenge section of the website or email the editor at

Our solution is far from being a commercially available product, but instead has been developed and used for research carried out at Carnegie Mellon University and North Carolina State University.

They have developed a lightweight elastic device that acts in parallel with the user’s calf muscles, off-loading muscle force and thereby reducing the metabolic energy consumed in contractions. The device uses a mechanical clutch to hold a spring as it is stretched and relaxed by ankle movements when the foot is on the ground, helping to fulfil one function of the calf muscles and Achilles tendon. Unlike muscles, however, the clutch sustains force passively.

The exoskeleton consumes no chemical or electrical energy and delivers no net positive mechanical work, yet reduces the metabolic cost of walking by around 7% for healthy human users under natural conditions, comparable to savings with powered devices.