At-home fitness brand NordicTrack from iFIT has launched what it says are the first voice-controlled, adjustable dumbbells to work with Amazon's virtual assistant Alexa.

The NordicTrack iSelect dumbbells can be electronically adjusted from five to 50 pounds in seconds with a voice command to a compatible Alexa-enabled device.

The dumbbells can also save and automatically adjust to a user's preset for 15 different dumbbell exercises.

According to Mark Watterson, chief experience officer for iFIT – NordicTrack's parent company – the innovation means that a user doesn't need to end to disrupt a workout by adjusting weights between exercises.

"The electronic adjustment eliminates the pain points of cumbersome mid-workout weight change found on other adjustable dumbbells, which can lead to decreased heart rate and reduced time under tension," Watterson said.

The dumbbells can also be adjusted mechanically, triggering a weight adjustment with a turn of a knob.

The NordicTrack iSelect Adjustable Dumbbells are priced at US$429 and come with a one-month iFIT membership, providing access to iFIT's library of workouts.