Exercise requires energy but who knew energy can be generated by sweat that comes from exercise?

Incredibly, a small device called a "temporary tattoo" has been created that harnesses the power of sweat.

The temporary tattoo transforms the lactate found in sweat to generate electrical energy. The innovation sprang from a research team's effort to monitor levels of lactate during exercise.

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Lactate is a by-product of the body produced when glucose is converted into energy.

Athletes actually monitor their lactate levels in an effort to evaluate their endurance during training. Lactate levels are also vital indicators of heart failure and infection.

Currently, the only way scientists measure lactate levels is through blood analysis. Lactate levels can be measured through sweat as well, said researcher Wenzhao Jia of the University of California San Diego.

The "temporary tattoo" or lactate sensor, which is worn like a bandage, collects data through a mobile device.

The energy created by the sensor is only around 4 microwatts, not even enough to power a digital watch.

Researchers, however, believe they can intensify the "biobattery" such that it can generate enough electricity to power an iPod or a GPS device.

"Right now we're working on the biofuel cell so it can get higher power," Jia stated.

What the study found was that people who were less fit produced more sweat energy than those who were moderately fit to fit. Subjects who were the fittest expelled the least amount of energy.

The inconsistency is a problem researchers are trying to overcome.

Jia said they may have to integrate another electronic element into the biobattery for it to store power better and more efficiently.

"Sweat has gotten a bum reputation. It makes us uncomfortable, makes us smell ... Sweat has been largely neglected, not thought of as a worthwhile physiological fluid," said Josh Windmiller, another one of the researchers involved with the study.

Windmiller, the founder of Electrozyme, a company that develops wearable sweat monitors, believes the new technology might finally give sweat the respect it deserves.