Force- and pressure-based wearables like smart insoles and grip sensors operate more sophisticatedly than you might think. While they may appear to be simple sensors attached to shoe insoles or handles, they contain highly sensitive pressure-sensing structures inside.
Basically, piezoresistive, capacitive, and piezoelectric sensors utilize the principle that electrical properties change under pressure.

For example, insoles simultaneously measure the load distribution on the sole of the foot at multiple points. When we walk, the load shifts from the heel to the midfoot to the toes. Sensors read these pressure changes in real time and extract biomechanical information, such as gait pattern, left-right balance, impact intensity, and ankle rotation angle. This data is used in sports training as feedback, indicating things like “too much weight on one side” or “excessive landing impact.”

Grip sensors operate under a similar principle. They detect pressure distribution, force direction, and subtle changes in force that occur when gripping something with the hand. In the field of rehabilitation, it’s particularly useful for measuring information such as whether a patient is recovering intended hand strength, accumulating muscle fatigue, or experiencing fluctuations in strength during repetitive movements. Analyzing force change patterns over time can create a muscle fatigue accumulation curve and identify areas where specific muscle groups are overused.

Real-time feedback is possible because sensor data is transmitted directly to a smartphone app or wearable system, where an algorithm interprets this and provides immediate feedback. For example, “10% more weight is being placed on the left foot,” “asymmetry in grip strength,” or “weak shock absorption may lead to fatigue accumulation.” Recently, many attempts have gone beyond simple thresholding to analyze patterns using machine learning (ML) to estimate exercise posture and even injury risk.

In short, these sensors aren’t simply “tools for measuring force,” but rather biomechanical interfaces that interpret body movement, balance, efficiency, and fatigue through force changes. Even without hands-on experience, their precision is technically understandable, leading to their widespread use in sports and rehabilitation.

Wow… I enjoyed reading the article. I’ve heard a lot about smart insoles, but I didn’t know they could measure pressure changes so precisely. But I have a question: how precise are these pressure sensors? For example, can they detect even the slightest pressure change on the sole of the foot?

They’re surprisingly sensitive. Even basic sensors like FSR (Fixed Pressure Resistive Sensors) are quite accurate, and capacitive and piezoelectric sensors can even detect subtle changes in load.
For example, they can accurately detect patterns like a 2-3% increase in force applied to the toes while walking. This allows them to immediately detect balance issues or ankle rotation patterns.

Oh… Isn’t that almost equivalent to physical therapy equipment? So, is it possible to provide something like a “gait analysis report” with smart insoles?

Yes, most current products go that far.
They even have ML models that analyze pressure distribution, gait cycle, left-right asymmetry, impact intensity, and fatigue patterns. It used to be simply “high/low pressure,” but now it interprets it like this: “Your left foot landing timing is 0.1 seconds slower → fatigue is accumulating.”

Is the grip sensor similar? You said it’s good for monitoring hand muscle strength recovery. How does it actually provide feedback?

Yes, the principle is almost the same.
It doesn’t just measure average strength like a grip strength meter. It reads patterns like when strength is lost, when things start to shake, and when pressure on specific fingers is weakening.
So the app tells you something like, “As you’re entering your third set, the strength in fingers 4 and 5 is declining first → muscle fatigue is starting.” It’s really useful for rehabilitation.

Wow… This is much more high-tech than I thought. I thought it was just a sensor toy, but it’s almost like an interface that reads your entire body movements.

That’s accurate. It doesn’t just measure force or pressure, but rather interprets the overall context of your body movements through those changes. That’s why sports trainers and physical therapists are using it a lot these days.
The term “sensor-based biomechanical interface” isn’t for nothing.