it looks like jumping stilts allow you to deliver a lot more energy in a short period - for instance, running up to 25mph, or jumping over cars - but you pay for that with significantly increased calorie burn and the use of many more muscles.
So, probably really not what you want for endurance activities such as foot patrol.
In addition, the springs in them need to be calibrated for the weight they're supporting, and they top out around 240lb / 110kg. So you'd need extra heavy duty ones for soldiers with packs, and then you couldn't use those once the packs had been removed.
Maybe if you had a situation where you needed a couple of soldiers to dump their packs, don a pair of these that they'd been carrying, and run somewhere really fast ... ;)
In related news, the Russian Army investigated gasoline-powered 'rocket boots' for soldiers. Because of course they did. Sadly they didn't work out too well.
https://www.nytimes.com/2007/03/17/business/worldbusiness/17...
"One result of the Russian space agency testing was a calculation that the energy in calories used to move the two-pound boot at a run would exceed the energy input from the gasoline engine. That meant, it was more tiring to run with the motorized footwear than without it, undermining the original rationale. Only if the weight could be reduced to below 2 pounds per boot would the wearer have a net energy gain. So far they have failed at this."
Also,
" 'The worst situation is when the spark fires as the runner just lands, and the force of the blast is absorbed by his body,' Mr. Garipov explains flatly."
Maybe not the best idea. (Although I reckon if you outfitted them with modern electronic ignition and a sensor to ensure that they'd bottomed out and begun recoiling before ignition, you could do a lot better...)