Anyone who runs regularly knows the importance of avoiding a stress fracture, which can sideline you for weeks. So many runners have been turning to shoe insoles and socks fitted with sensors to protect them from this dreaded overuse injury. Is this new wearable tech the best thing since, well, feet…or a waste of money? A new study looks into that.

The new wearable sensors are in shoe insoles, socks and waistband clips. The sensors estimate something called ground reaction force (GRF), which is the impact of each foot hitting the pavement. Researchers have long assumed that GRF reflects the amount of stress on the body’s muscles and bones—the higher the GRF, the higher the stress and the greater the risk of an overuse injury. Vanderbilt University scientists tested that theory in a small study using 10 healthy adults, average age 24, who ran at least 10 miles a week.

The researchers designed a series of 30 different treadmill tests at a variety of running speeds and slopes intended to mimic real-life running conditions for recreational runners. High-speed, motion-capture cameras tracked the runners’ movements…while the treadmills were equipped to record the GRF under their feet. From the combined data of GRF plus the estimated force on bone from muscle contractions, the researchers were able to determine bone loading on the runners’ tibias—the lower leg bone that is a common site for stress fractures.

Results: GRF alone did not correlate to bone loading. The researchers commented that typically, GRF contributes less than 20% to bone loading. In fact, in the study, when GRF was lower, stress on the bone was sometimes actually higher—exactly the opposite of what researchers and exercisers alike have long believed. The primary source of tibia stress was from the muscle contractions.

What it means: The data collected by these wearable sensors is both incomplete and—since bone stress was higher when GRF was lower—interpreted in a way that could actually lead to great risk for injury.

The Vanderbilt team hopes to create more useful wearable tech for recreational and elite athletes and military cadets. It will be based on a system they developed that gathers several kinds of data from multiple wearable sensors.

In the meantime, here are some things that can reduce the likelihood of stress fractures (they also help avoid shin splints)…

• Take a gradual approach to reaching your goal. Get in condition slowly.

• Consider using a training program, such as the one from New York Road Runners (NYRR), which offers training plans for races of various lengths for beginners to advanced runners.

• As much as possible, run on even surfaces.

• Build days off to rest into your training program.

• Boost running efficiency the way pros do by learning the Pose Method, a system for teaching human movement and sport specific techniques developed by an Olympic coach.

• Recognize the symptoms of a problem—such as pain in a single spot at the front of your lower leg while running, a common sign of a stress fracture—and consult a sports medicine doctor right away.

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