Recently, Nicola Duffy, of Dublin, Ireland, recorded her own close call with a bolt of lightning. The video has shocked more than 300,000 viewers on YouTube.

Luckily, Nicola is okay, but bolts from the blue can cause severe injuries, or worse.

When applied correctly, however, electrical impulses in the form of electro-stimulation can ease pain, heal broken bones, mend wounds, promote muscle strength, and repair cartilage.

Researchers think electro-stim works by hot-wiring nerve impulses, increasing blood flow, and altering gene expression that promotes wound healing.

There are at least two kinds of electro-stim: TENS (transcutaneous electrical nerve stimulation), and EMS (electronic muscle stimulator).

TENS aims to keep pain messages from arriving at pain receptors in the brain. There are Food and Drug Administration-approved over-the-counter versions for prevention of migraine, for pain relief, and for easing diabetic nerve pain.

But overuse can cause pain and muscle twitching, and TENS isn't for use around your eyes, if you're pregnant, or if you have a pacemaker.

EMS targets muscles by triggering contraction of muscle fibers. Some OTC brands are unsafe.

The FDA has reports of EMS causing shocks, burns, bruising, skin irritation, and pain, as well as interfering with pacemakers.

There's also a risk of electrocution if the devices' cables and leads don't meet electrical safety standards (and some don't). The FDA is investigating firms that are illegally marketing EMS devices. Unfortunately, there are many.

So talk to your doc before using at-home TENS or EMS; get a recommendation for a safe brand, and don't use it during a lightning storm.