It's really light (25g to be precise) and the clip doesn't rub against your back. Running with the Lumo Run is surprisingly really comfortable and you barely notice it once you're in the zone. Thankfully, the latter didn't happen once, but it's always a concern and just to be clear, you do need to remove the sensor before giving your sweaty shorts a clean. The sensor is sweat and waterproof, which in practice means it's good for a run in the rain rather than accidentally taking it for a dip in the pool or throwing it in the washing machine.
Fortunately, it didn't appear to have an impact on the sensor picking up the data. We thought this could potentially be an problem for those that tend to wear shorts and leggings at the same time on those colder running sessions along with a running bag around waist.
It can only be clipped on the back of lower body garments (shorts, leggings etc) because it needs to be in alignment with the spine to provide the most valuable data. If you don't wear it properly, you won't get the data. Placement is key with the Lumo Run sensor. Initially, this was our biggest concern about wearing the Run, but it hasn't managed to fall off once.
LUMO BODY TECH REVIEW ZIP
The black rubber casing is a lot like the one you find on the (now ancient) Fitbit Zip with a clip that offers a clamp-like grip to ensure that it doesn't go flying off. There's a small compartment at the bottom that hides away the microUSB charging port and a single LED notification light to indicate whether it's got enough battery to track a run. The thumb sized sensor keeps things simple on the design front and that's not all that surprising when you're not going to need to look at it during a run. Read this: Understanding the stats on your running watch Then the decision was made to launch the Lumo Run sensor with a small rubber case so you can clip it onto any running kit and make it smarter. When the Lumo Run was first announced it was pitched as a pair of smart running shorts or capris that you can slip the sensor into. We've been putting the Lumo Run through its paces for over a month now to find out if the makers of a posture tracker can actually make a good wearable for runners too. At $99, it's significantly cheaper than buying a GPS running watch, but it is only compatible with iPhones, so that's something to keep in mind.