Get access to everything we publish when you sign up for Outside+.
Run Free Pro Bio Headphones by Soul Electronics
Weight: 20 grams
Best Features: Great sound quality. Real time coaching feedback.
Room for Improvement: Challenging set up, initially.
The Soul Electronics Run Free Pro Bio with real-time voice coaching is an impressive product that provides real-time coaching while you’re running via technology that is built into the headphones. Included is a set of bluetooth headphones (with reflective cable), six sets of ear tips, two pair of ear locks, a micro USB charger and a carrying case.
Out of the box expect to charge the headphones for about two hours. Next, download the Soul Fit app (free) and register. Pair the headphones via bluetooth to your mobile device, and once paired, the headphones will likely need a firmware update. During testing, the update took an hour. Finally, the headphones need to be calibrated, which is a pretty simple process of putting them on and allowing them to “find their balance.”
The sound quality is great and the fit is easily adjustable with the ear tip and ear lock options. The headphones then monitor your running form and provide feedback on the following:
Symmetry—Represents the balance of the push-off forces of both legs. It indicates the stronger side of the two legs and the percentage of the left-right difference. A slight asymmetry is acceptable (<2.5%).
Head Angle—The up-down tilt angle of your head. A head angle affects your upper body posture that is critical to efficient running. The alignment of your head and shoulder possibly affects your breathing as well.
Vertical Oscillation—The up-down bounce of your body. A large vertical oscillation in your run indicates that more energy is wasted while moving up and down.
Flight Time—The duration of time that both feet are off the ground. A long flight time is related to large vertical oscillation, over-strides, and high shocks on legs when landing.
Consistency—Represents the consistency of your running form in percentage. Elite runners maintain a high level of consistency throughout long-distance runs. Inconsistency may lead to an injury or lower running efficiency.
Step Length—Forward distance from one heel to the other.
Maximum Force—The maximum force generated by your legs when pushing off the ground. The metric is in units of body weight (BW). For instance, the maximum force of 2.5BW represents that your leg generated a force 2.5 times greater than your body weight. An excessively high force leads to leg injuries.
Shock—Represents how hard or quickly your foot strikes the ground when landing. This measures the loading rate of impact force, in units of body weights (BW) per second. A shock value under 100BW/s is desirable.
Stance Time—The duration of time that your foot is in contact with the ground. A long stance time spreads the landing shock, reducing injury risk. Shortening the stance time will improve performance.
Cadence—The amount of steps taken per minute (SPM). A high cadence of 160 to 180 SPM will greatly increase your efficiency, limit your flight time, limit overstriding and decrease shock.
How does it assess all of these different components from a pair of headphones?
Trail Runner‘s contact for Soul Electronics explained: “Run Free Pro Bio has a built-in piece of hardware designed by Beflex called BiomechEngine. Essentially, it’s a microchip-sized motion sensor that has the ability to track each user’s body movements and compute it into various running data points. It’s able to do this because it’s attached to the runner’s head via the earphones, allowing it to capture all of these measurements through repeated running motion.”
Feedback is given over the top of your favorite running playlist in real time (you can also forego the music and just have the in-ear coach activated, or vice versa, and only do music). Each of these functions can be adjusted in the app settings. In run, the app will announce distance covered and average pace every mile or kilometer.
While testing, the assessment was accurate and immediate. At one point, I looked down at my shoe during a run and the coach noticed me leaning forward. The coach then asked me to look up to correct the form inefficiency.
One of the best features of the Run Free Bio is after your run. The Soul Fit app will map your route via GPS showing pace, splits, elevation gain and loss, calories burned and step count. The app will store your workout and show your stats versus the optimal range for the key parameters.
Based on that information, the app will provide the key factors to evaluate the risk of injury. Any imbalance can be viewed and corrected by the runner. The app only works when your phone is present and enabled. Soul Electronics claims the headphones can run for 11 hours on a single charge.
—Brian Passenti is the owner of Altitude Endurance Coaching, a running and multisport coaching service. A self proclaimed pizza connoisseur, Brian eats most of his pizza in Glenwood Springs, Colorado.