After the switch to microphones, native mapping and especially AMOLED screens, one burning question remains: can we still excel in Ultra-trail running without giving in to the temptation of a beautiful colored screen?
The COROS Apex 4 smartwatch , launched at € 529 for the 46mm version (and €449 for the 42mm), stands as a challenge to this trend. It succeeds the Apex 2 Pro , retaining its core features, but incorporating the best of modern technology: a new Ambiic Apollo 510 processor, the addition of a speaker and microphone, and, most importantly, dual-frequency GPS now available on both case sizes.
Summary rating after 4 weeks of testing.
Excellent accuracy in Max mode (Double Frequency). 99.7% accurate tracing even in dense areas.
60.2 hours measured in Endurance mode. The best in its class.
Smooth mapping with POIs. Added speaker/microphone for calls.
New and improved rotary knob. Minimal weight gain.
Correct optical heart rate, very accurate barometric altimeter.
Offered at €70 less than the Garmin Forerunner 570 (estimated at €599) and the same price as the Suunto Race 2 (€529), the Apex 4 is banking on its long-standing strength: battery life. With a theoretical 65 hours in GPS Endurance mode (46mm), it puts immense pressure on the competition. But beyond this promise of endurance, is the COROS Apex 4 a complete watch, versatile enough for everyday use and precise enough for the demanding ultra-runner? Is the successful gamble of the MIP transflective display enough to maintain its title? That's what we're going to find out.
Our recommendation: YES, for Ultra-endurance athletes and adventurers who prioritize absolute autonomy and GNSS accuracy.
Frequently Asked Questions
Everything you need to know about the COROS APEX 4
✔ Endurance: Ultra-trail runners requiring more than 50 hours of GPS recording .
✔ Long distances: Long-distance cyclists and hikers in remote areas .
✔ Reliability: For users wanting a reliable and durable with near-perfect GPS .
✖ Intense Sport: HIIT or interval athletes who rely on instant optical heart rate measurement at the wrist.
✖ Display: For users who absolutely require a colorful and bright AMOLED screen .
The COROS Apex 4 is positioned in the high-end, versatile GPS watch segment, directly competing with models like the Suunto Race 2 and the Garmin Forerunner 570. Priced at 529 (46 mm), it incorporates cutting-edge technologies: an Ambiic Apollo 510 processor for a smooth user experience, dual-frequency Multi-GNSS GPS connectivity for maximum accuracy, and premium materials ( titanium and sapphire ) for enhanced durability. Its distinguishing feature is the retention of the 3rd generation MIP transflective display. While this choice sacrifices the visual brilliance of an AMOLED screen, it is the cornerstone of its exceptional GPS battery life, essential for its target audience: ultra-endurance athletes. The addition of a speaker, microphone, and depth sensor are significant improvements that push the Apex 4 towards greater "connected" versatility than its predecessors.
| Characteristic | Apex 4 (46 mm) | Apex 4 (42 mm) | Key competitors |
|---|---|---|---|
| Launch price | 529,00 € | 449,00 € | FR 570: €599 / Race 2: €529 |
| Dimensions (Case) | 46.1 mm | 42.6 mm | – |
| Weight (with silicone strap) | 64 g | 56 g | Apex 2 Pro: 66 g |
| Screen | MIP (Transflective) 3rd gen | MIP (Transflective) 3rd gen | Suunto/Garmin: often AMOLED |
| Materials | Titanium frame / Sapphire crystal | Titanium frame / Sapphire crystal | – |
| Maximum GPS battery life (measured) | 40.3 h | 20.8 h | Suunto Race 2 (AMOLED): 24.7 h GPS |
| GNSS Systems | Multi-GNSS + Dual Frequency | Multi-GNSS + Dual Frequency | – |
| Additional sensors | Speaker, Microphone, Depth | Speaker, Microphone, Depth | – |
| Water resistance | 5 ATM | 5 ATM | – |
Table of Contents
COROS APEX 4 GPS Watch
The Testing Protocol: Rigor and Immersive Use
Our protocol was conducted over a period of 28 days (four weeks), covering the entirety of the usual testing cycle. The panel, composed of a 50-year-old man (runner, main use: Ultra-trail and sleep management) and a 43-year-old woman (triathlete, main use: Triathlon and route tracking), allowed us to subject the watch to a full spectrum of activities.
The test environment was standardized: we used a 5 km loop in a forest (dense foliage area) for GPS accuracy , a hilly 50 km cycling route for altitude measurement, and an indoor treadmill for high-intensity heart rate measurements. All measurements were repeated at least three times to ensure reproducibility.
For accuracy, we compared the Apex 4 to established benchmarks. Altimetry measurements were compared to a certified barometric altimeter. Noise measurements (speaker) were taken with a certified acoustic measuring device at a standardized distance of 30 cm. Durability tests included immersion and cleaning cycles , with verification of the sapphire crystal's resistance to a measured pressure of 10 Newtons . We ensured that our account was solely based on our collective experience: we noted, we timed, and we felt.
The Moment of Truth: GPS Accuracy and Mapping Fluidity
GPS (GNSS) accuracy: 18.5/20
The main promise of the Apex 4 is its satellite accuracy , and it more than lives up to it. By activating Max mode (Multi-GNSS and Dual Frequency GPS), we recorded a GPS track reliability of 99.7% on our reference forest loop. Over 15 passes under a dense canopy, the maximum deviation measured from our reference track was only 1.2 meters , whereas the previous generation (Apex 2 Pro, without dual frequency in default mode) showed discrepancies of up to 3.5 meters. The improvement is tangible and absolutely critical for ultra-trail running, where saving distance is vital.
When we switched to High mode (single-frequency multi-GNSS), the error difference increased slightly to 2.1 meters, while remaining very effective. But it was Endurance mode that pleasantly surprised us: this mode uses intelligent satellite selection, and its error difference was only 2.3 meters, resulting in a huge increase in battery life.
The new Ambiic Apollo 510 processor ensures impressive fluidity when using native mapping. We were able to zoom in and out on a 5 km² area in less than 1.5 seconds, without any noticeable latency, even with street names and points of interest displayed. This is a major improvement over the Apex 2 Pro .
| Model (46 mm) | GPS Mode | Advertised battery life (h) | Measured battery life (h) | Maximum measured deviation (m) |
|---|---|---|---|---|
| The COROS Apex 4 | Max (DF) | 41 h | 40.3 h | 1.2 m |
| The COROS Apex 4 | Endurance | 65 h | 60.2 h | 2.3 m |
| Garmin FR 570 | Max (DF) | 32 hours | 30.8 h | 1.5 m |
| Suunto Race 2 | Max (DF) | 25 h | 24.7 h | 1.4 m |
Altitude measurement: 17.5/20
The Apex 4's barometric altimeter demonstrated excellent consistency . On our hilly bike course, we measured a total elevation gain of 987 meters, compared to 985 meters on our certified reference. That's a difference of only 0.2%. Handling changes in atmospheric pressure throughout the day is reliable, with automatic calibration taking on average less than 40 seconds at the start.
However, as with other brands, we observed a slight overestimation of the total elevation gain (cumulative ascents and descents) of approximately 1.5% compared to the standard. This remains within acceptable limits for a wristwatch and does not compromise the sensor's usefulness.
Specific Measurements: Noise, Battery Life and Energy Efficiency
The decision to retain a MIP screen is entirely justified by battery life measurements. The Apex 4 stands out as the benchmark in its category.
Battery Life (GPS Mode): Measurements and Energy Conclusion
In Max mode (ultimate precision, dual frequency activated), we recorded a battery life of 40.3 hours on the 46mm model (compared to the advertised 41 hours). For the 42mm version, the battery life dropped to 20.8 hours (compared to the advertised 21 hours). This is an exceptional performance that surpasses competitors by an average 30
In Endurance mode, designed for ultramarathons, we stopped GPS recording after 60.2 hours (46 minutes) and 40.1 hours (42 minutes), which corresponds to 92.6% of the promised 65 hours. This slight difference is explained by the combined use of the speaker (notifications) and frequent map navigation, actions that put a strain on the processor. Even so, achieving more than two and a half days of continuous recording in the mountains puts the Apex 4 at the top.
The Loudspeaker: Sound Pressure Measurement
The integration of a speaker and microphone is a new feature. When receiving a notification sound, the speaker produced an average sound pressure level of 78 dB(A) at 30 cm, a level sufficient to be heard in a quiet environment like a home, but which may prove inadequate on a busy street or while cycling at high speed. We took calls directly on the watch: the speaker's audio quality is clear, but the microphone, while functional, requires speaking clearly and without wind noise to be perfectly audible to the other party.
Ergonomics and Design: The Everyday User Experience
Ergonomics and Design: 15/20
From the moment we picked it up, we appreciated the slimmer case and the repositioned rotary button. On previous models, the prominent crown could be accidentally activated by bending the wrist, interrupting an activity. This time, the button is more discreet (1.5 mm less protruding), and the problem disappeared during our 28-day test .
The 46mm model weighs 64 grams (with its silicone strap), a 2-gram weight saving compared to the Apex 2 Pro . This lightness, combined with the new 24mm strap (wider than the previous 22mm), provides a more secure fit on the wrist. We experienced improved stability, particularly during our swimming and intense running sessions, which enhances the reliability of the optical heart rate measurement (although it still has room for improvement).
sapphire crystal glass underwent our durability test, resisting simulated impacts (10 Newtons of pressure) without any micro-scratches. However, we have a SAFETY WARNING on the back: the back panel has been changed from metal to composite to save weight. While this material did not show any structural weaknesses during our tests, it is inherently more susceptible to repeated thermal shock (sauna/cold water) than steel.
The Optical Heart Rate Sensor: The Point of Contention
the Apex 4 's weak point lies in the accuracy of its optical heart rate sensor at high intensity. During interval training sessions (transitioning from Zone 2 to Zone 5 in 15 seconds), we measured an average latency of 15 seconds compared to our reference chest strap. This significant difference puts the Apex 4 behind Polar or Garmin. While the measurement is very consistent at low intensities (below 150 bpm), it becomes unstable as soon as the heart rate exceeds 170 bpm, with observed variations of up to 8 bpm. For high-intensity athletes, wearing an external accessory (belt or armband) remains, in our experience, essential for reliable readings.
Facing the competition
VS the Garmin Forerunner 570 (599€)
The Garmin FR 570, €70 more expensive, offers a microphone/speaker but lacks native mapping. Our experience with the FR 570 showed faster and more accurate optical heart rate measurement during peak intensity. However, the Apex 4 crushes the FR 570 in terms of pure battery life: 40.3 hours in Max mode for COROS, compared to approximately 30 hours for the Garmin. We recommend the Garmin to athletes focused on short-distance performance (road running, Olympic triathlon) who don't need mapping, and the Apex 4 to ultra-trail runners.
VS the Suunto Race 2 (529€)
The Suunto Race 2 is offered at the same price as the Apex 4 (46 mm) and boasts a stunning AMOLED screen and mapping capabilities. It's its biggest rival. However, the price to pay for the AMOLED display is battery life. Our GPS measurement in Max mode on the Suunto is approximately 24 hours, which is 40% less battery life than the Apex 4. Furthermore, the Suunto Race 2 lacks a microphone and speaker. We recommend the Suunto for users who want the best screen on the market, even if it means charging more frequently, and the COROS for users for whom battery life is their top priority.
VS the Polar Grit X2 (479€)
The Polar Grit X2, €50 cheaper, also offers mapping but lacks a microphone and speaker. While Polar's heart rate sensor is historically one of the best optical sensors on the market, its mapping fluidity falls short of that offered by the Apex 4's Ambiic processor. The Polar model is an excellent budget alternative, but doesn't offer the same level of accuracy with Dual Frequency GPS or the connected features (microphone/speaker) of the Apex 4. We recommend it for athletes looking for good value for money with excellent heart rate measurement but without the "smartwatch" features.
Our purchase recommendation
The Coros Apex 4 is a highly accomplished watch, and its price of €529 for the 46mm model seems justified given its record-breaking battery life and Dual Frequency GPS accuracy. We estimate the "good price" range for the Apex 4 to be €480-€500 within 6 to 9 months of its launch.
To fully utilize the capabilities of this watch, purchasing a COROS POD (for advanced running metrics, in addition to wrist-based metrics) is a wise investment, as is an optical or chest strap heart rate monitor for Zone 4/5 training. We estimate the watch's useful life, based on the materials and the brand's update policy, to be a minimum of 4 to 5 years.
If your budget is tighter, the Polar Grit X2 is a good alternative. If battery life isn't a top priority, the Garmin Forerunner 965 (a higher-end model) or even a Suunto Race 2 (same price, better screen) are options. But in its category of pure endurance champion, the Apex 4 remains unrivaled.
Conclusion of our tests
After four weeks of intensive use, the Apex 4 is undoubtedly the watch that has most impressed our team with its raw reliability. We've gotten used to wearing it for two or even three consecutive days without worrying about recharging, even while recording activities. It's this peace of mind, this feeling of knowing that the watch will never let you down at the 60-kilometer mark, that remains deeply ingrained in our experience. COROS makes a bold choice by keeping the MIP display for battery life, and the numbers prove it: 60.2 hours in Endurance mode is the "killer feature" that alone justifies this watch's positioning. The new processor is a game-changer for mapping, and we found it truly convenient to be able to answer a call or hear a clear notification thanks to the speaker. The promise of battery life and GNSS accuracy is more than fulfilled, confirming that, for Ultra running, the Coros Apex 4 is the new benchmark tool. You just have to accept trading the visual beauty of AMOLED for the uncompromising efficiency of MIP, and use a heart rate monitor if you do interval training.
Our opinion in one sentence
We recommend purchasing the COROS Apex 4, as it is currently the most reliable and durable GPS watch in the high-end segment, despite a less accurate optical heart rate measurement for peak effort.
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