To use the Polar Loop biceps band, pair the Loop in Polar Flow, place its module in the band with the fastener facing up, and wear it snugly on the upper arm with the module on the outside and the oval mark pointing forward. In Polar Flow, set “I wear my product on” to the arm you are actually using. Polar documents left- and right-wrist choices rather than a separate biceps setting, so accurate readings depend on correct physical placement and uninterrupted skin contact.
The sensor should stay against your skin without a visible gap, but the band should not pinch or leave numbness. Polar recommends the non-dominant side for the most accurate activity tracking; if you choose the biceps, use the same side consistently and keep the Flow handedness selection matched to that arm.
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What you need before fitting the band
Have the Polar Loop, its biceps armband, a compatible phone with the Polar Flow app, and the charging cable ready. Plug in the Loop before attempting setup. Open Polar Flow and allow the app to install any device-firmware update it offers. Keeping both the app and firmware current ensures that the setup screens and device behavior match Polar’s current software.
Polar listed the Loop at $199.99 in the United States in 2025. That is a dated, region-specific list price rather than a guaranteed current price, so check Polar’s current product page if purchase cost is part of your decision.
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Set up and pair the Polar Loop in Polar Flow
- Charge and wake the device. Connect the Loop to power and wait for it to become available. Do not begin a workout or rely on readings until the device has completed its initial setup.
- Open Polar Flow. Sign in if prompted, then start the device-add or pairing flow. Keep the Loop close to the phone while the app searches.
- Install offered updates. If Polar Flow presents a firmware or app update, apply it before configuring wear location. Keep the phone nearby until the update and restart are complete.
- Confirm the device card appears. After pairing, open the Loop’s device card in Polar Flow. This is where you set the arm selection used by the app.
- Choose the matching arm. Open “I wear my product on” and select “Left wrist” or “Right wrist” according to the side on which the band is worn. Polar’s documented labels are wrist-oriented; the app does not document a distinct biceps or upper-arm mode.
- Put on the band and check the live signal. Once the physical fit is complete, check that the optical sensor remains in contact with skin and that the device is recording normally before you rely on the session.
If you switch the Loop from one arm to the other, return to the device card and change the handedness selection. The setting should describe the arm in use, not your dominant hand by default.
Install the Loop module in the biceps armband
Orient the fastener before inserting the module
Fit the Loop module into the armband with the fastener facing up. Secure the fastener fully so the module cannot shift inside the frame during movement. A loose module can change sensor contact even when the fabric itself feels tight.
Find the upper-arm position
Slide the armband onto the upper arm, generally over the biceps area rather than the forearm or directly across the elbow. Polar’s armband instructions specify that the module belongs on the outside of the arm. The outside position keeps the optical unit aligned with the skin while leaving the display and frame oriented consistently.
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Rotate the frame until its oval mark points toward the front of your body. This forward-facing orientation is part of Polar’s placement guidance. Do not use the mark as a substitute for skin contact: the sensor still has to sit flat against the arm.
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How tight should the biceps band be?
Adjust the band until it is snug and comfortable. The correct tension is the minimum that keeps the optical sensor in continuous contact while you move. A properly fitted band should not slide significantly when you raise, bend or rotate the arm, yet it should not cause pressure pain, tingling, numbness, cold fingers or pronounced skin irritation.
- Too loose: the sensor lifts during movement, a gap appears between the optical window and skin, or the LED can be seen through the gap. Tighten the band slightly and recheck.
- Too tight: the band leaves deep marks, feels restrictive, causes discomfort during strength work or makes the skin sore. Loosen it one adjustment at a time.
- Correct: the module stays still, the optical window remains flat against the skin and you can wear the band through ordinary movement without distraction.
Overtightening does not create a more accurate reading if it irritates the skin. If you remove the band for a break, refit it at the same snug tension before restarting tracking. Hair, sweat, lotion and fabric folds can also create small gaps; smooth the band and clean the contact area when needed.
Where to wear the Loop on your upper arm
Polar’s official biceps-band guidance is specific about the region and orientation: upper arm, module outward, oval mark forward. It does not publish a required distance from the shoulder, elbow or biceps muscle belly. Choose a section of upper arm that gives the module a broad, stable skin surface and does not sit directly on a moving joint.
Use the same placement each day when you want comparable activity records. Moving the module between the upper arm, wrist and different points on the arm changes how it contacts the skin and how it moves, which can make day-to-day values harder to interpret.
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Wrist versus upper-arm wear
Polar’s Loop manual says: “For the most accurate activity tracking, we recommend wearing the device on your non-dominant hand.” For wrist use, place the Loop on top of the wrist at least one finger’s width above the wrist bone, with the oval mark toward the thumb. The biceps armband is an alternative physical location, but Polar does not publish a numerical accuracy improvement for it or a controlled comparison against wrist wear.
| Decision factor | Wrist placement | Upper-arm placement |
|---|---|---|
| Sensor contact during movement | Follow Polar’s wrist position: top of the wrist, at least one finger’s width above the wrist bone, oval mark toward the thumb. Keep the sensor flat. | Use the upper arm with the module outside, oval mark forward, and a snug fit that prevents lifting. |
| Documented app setting | Polar Flow explicitly offers “Left wrist” and “Right wrist.” | Polar does not document a separate biceps mode; select the left- or right-side option that matches the arm in use. |
| Interference with watches | Wrist wear can compete for space with a conventional watch, bracelet or clothing cuff. | An upper-arm band leaves the wrist free, but you must ensure it does not catch on sleeves or shift during training. |
| Strength-training comfort | A wrist device can contact bars, handles or wrist wraps. | The biceps position may avoid wrist contact, provided the band remains clear of the elbow’s moving area. |
| Published biceps accuracy figure | Polar provides its general non-dominant-hand recommendation. | Not stated by Polar; no percentage improvement or controlled wrist comparison is published. |
| Cleaning and refitting | The Loop can be removed and cleaned directly on the wrist. | The module must be removed or opened from the armband so the frame, band and skin can be cleaned and dried. |
Choose the upper arm when it gives you steadier contact or avoids wrist interference, not because Polar promises a specific accuracy gain. The defensible priority is fit quality: a stable sensor touching clean skin is preferable to a nominal location that moves or leaves gaps.
How to verify accurate tracking after fitting
Check the optical contact
Look at the sensor area after tightening. The optical sensor should remain in constant contact with the skin. If you can see an LED through a gap, or if the module rocks as you flex the arm, adjust the band before starting an activity.
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Check the orientation
Confirm all three orientation points: fastener facing up, module on the outside of the upper arm and oval mark pointing forward. A twisted frame can feel secure while placing the sensor at an angle.
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Check the Flow arm selection
Open the Loop device card in Polar Flow and verify that “I wear my product on” names the side you are wearing. The choice is presented as left or right wrist even when you are using the biceps band; there is no documented upper-arm label to select.
Check movement, not only a stationary fit
Raise and lower the arm, rotate the shoulder and perform a few ordinary movements. The band should stay in place without the sensor lifting. If it shifts only during a particular exercise, refit it before that activity rather than assuming the stationary fit is sufficient.
Using the Loop in water
Polar lists the Loop as water-resistant to 30 meters (WR30), suitable for bathing and swimming. It can track heart rate and calorie burn in water, but it does not provide swimming stroke-count or distance metrics.
For the most accurate heart-rate data in water, Polar recommends a tighter-than-usual fit. “Tighter” still means secure and comfortable; it does not mean painful or restrictive. Check that the optical window remains against the skin before entering the water, because water movement can expose a loose fit more quickly than ordinary activity.
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After swimming or bathing, rinse the device and armband with running water and dry them. Water resistance does not remove the need for routine cleaning.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Cleaning the Loop, armband and skin
Clean the device, band and contact area with mild soap and running water, especially after sweating. Rinse away soap and dry the components before wearing the Loop again. Polar advises against alcohol, disinfectant and other chemicals, which can damage materials or irritate skin.
- Remove the Loop from the armband if the frame or sensor needs cleaning.
- Rinse visible sweat, salt and dirt from the module and band with running water.
- Use a small amount of mild soap, then rinse thoroughly so residue is not trapped between the sensor and skin.
- Dry the module, band and arm before refitting.
- Inspect the sensor window and fastener for residue or damage before the next session.
If the skin under the band remains irritated after cleaning and loosening the fit, stop wearing it until the irritation settles. Repositioning to the other arm is not a substitute for allowing damaged skin to recover.
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Troubleshooting common fit and setup problems
| Symptom | Likely cause | What to do |
|---|---|---|
| The Loop will not pair | The app or firmware is outdated, the device is not sufficiently powered, or the phone is too far away. | Charge the Loop, keep it near the phone, reopen Polar Flow and install any update it offers before retrying the pairing flow. |
| The sensor LED is visible through a gap | The band is too loose, the module is not seated correctly or the frame is twisted. | Re-seat the module with the fastener up, point the oval mark forward and tighten slightly until the optical window lies flat. |
| The band slides during exercise | The adjustment is too loose or the placement is directly over a highly moving area. | Move it to a stable section of the upper arm and increase tension only enough to stop movement. |
| Readings become inconsistent after changing arms | The Flow arm selection still describes the previous side. | Open the device card and change “I wear my product on” to the arm now in use. |
| The band causes pressure or numbness | It is overtightened or positioned where the arm is compressed. | Loosen it, move it away from the elbow, and stop wearing it if discomfort persists. |
| Water sessions show heart rate but no swim distance | The Loop does not provide stroke-count or distance metrics for swimming. | Use the Loop for the metrics it supports in water: heart rate and calorie burn. |
A practical routine for daily use
- Before putting it on, check that the sensor and band are clean and dry.
- Insert the module with the fastener facing up and secure it.
- Place the armband on the same upper-arm region, module outward and oval mark forward.
- Adjust until the sensor is continuously touching skin without painful pressure.
- Confirm the left- or right-side selection in Polar Flow if you changed arms.
- After a sweaty or wet session, rinse with mild soap and running water, then dry before storage or the next wear.
This routine addresses the factors Polar documents: pairing and firmware, correct orientation, arm selection, clean skin and continuous optical contact. It does not turn the biceps band into a separately calibrated mode; Polar has not published a biceps-specific accuracy percentage.
What Polar does and does not establish about biceps accuracy
Polar’s published instructions establish how to place the official armband and how to maintain sensor contact. They do not establish that biceps wear is more accurate than wrist wear, nor do they provide a laboratory percentage, error range or controlled head-to-head result for the two positions.
That limitation matters when interpreting your data. Use the biceps band because it is more comfortable, avoids interference or stays in contact better for your activities. Keep placement and tension consistent, and avoid comparing a loose upper-arm session directly with a tightly fitted wrist session as though the location alone explains every difference.
Final setup checklist
- The Loop has been charged, paired in Polar Flow and updated when an update was offered.
- The module is seated in the armband with the fastener facing up.
- The armband is on the upper arm, with the module on the outside.
- The oval mark points forward.
- The optical sensor is flat against clean skin with no visible gap.
- The band is snug but does not cause pain, numbness or excessive pressure.
- “I wear my product on” matches the left or right arm in use, even though Polar labels the choices as wrists.
- After sweating or swimming, the Loop, band and skin are rinsed with mild soap and running water; alcohol and disinfectants are avoided.
Once those checks are satisfied, the Polar Loop is configured and worn according to Polar’s documented guidance. The quality of biceps tracking then depends chiefly on maintaining that same stable, clean, skin-contacting fit.
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