heart rate training

COROS Heart Rate Monitor Review

Name of Gear: COROS Heart Rate Monitor

Gear Category: Accessories/ Technology (heart rate monitors)

What the COROS Heart Rate Monitor looks like when not being worn.
What the COROS Heart Rate Monitor looks like when not being worn.

Typical Price: $79

Where to Buy: coros.com, rei.com, skimo.co, backcountry.com, runningwarehouse.com

Best Use:

Athletes are always in search of wearables that will provide more data! However, metrics mean little if they aren’t accurate. Wrist monitors on today’s watches have come a long way, but there are still large inaccuracies and anomalies that can occur. For example, when I grip a trekking pole, my watch will often read a low heart rate (HR) regardless of intensity level. Chest straps have long been the standard option for athletes who desire the most accurate HR data. Often they can be paired with a watch to make the real time HR readings accessible in action. That said, some folks, myself included, find wearing a chest strap to be uncomfortable at best or, at the worse, a recipe for chaffing. Additionally, chest monitors can interfere with avalanche beacon signals. This makes them risky for both skimo athletes and runners who enjoy high alpine adventures in the snow.

How?

The COROS Heart Rate Monitor provides a more accurate reading than wrist monitors while avoiding the shortcomings of the chest strap outlined above. This low profile heart rate monitor (HRM) is mounted on a soft elastic band and fits comfortably around the bicep of the user. Yes, the bicep! The HRM activates automatically once on the athlete’s arm. Then, after the initial set up, syncs to most watch brands and devices via Bluetooth (it doesn’t have to be another COROS product). The location on the bicep makes the device hardly noticeable to the user, decreases chafe probability and mitigates the interference issue with an avalanche beacon.

When? Where?

The COROS Heart Rate Monitor can be used in any situation where an accurate HR reading is desired. This includes roads, trails, long runs, races, training, etc. The only scenario I can think of where this monitor might not be a good fit is in a 200+ mile race due to the limit of 38 hours of active battery life. However, this is a highly specific situation and 38 hours is plentiful for most users. While the HRM is perfectly fine in rainy, wet conditions, it’s not suitable for swimming with as Bluetooth signals don’t carry underwater.

TRR Coach Dandelion running with her COROS Heart Rate Monitor on her left bicep. PC: Damien Scott
TRR Coach Dandelion running with her COROS Heart Rate Monitor on her left bicep. PC: Damien Scott
Sizing:

True to size.

Additional Sizing Comments:

The standard band is easy to adjust and fits a large variety of arms. There is also a large size band for athletes who require more volume. In either case, I suggest first adjusting the band snuggly, but not too tight, with your arm bent as though you were doing an arm swing while running. Micro adjustments can then be made from this point. I have found that sizing the band with your arm straight does not account for the increase in bicep size when the arm is bent. Therefore, it can end up being too tight.

Comparison to Previous Models and Other Brands:

Arm band heart rate monitors are relatively new developments. This COROS Heart Rate Monitor is the first, and most popular, model available. Other options include the Wahoo Tickr Fit and Polar Verity Sense, though I haven’t tested or heard much about them. All three come in at a similar price range of $79 to $99.

Durability and Accessibility:

I have been using the COROS Heart Rate Monitor for about 9 months during both training and ultra distance races. It has accompanied me in temperatures ranging from -20F to 102F (that’s -29C to 39C) and performed without issue within that range. It was subject rain, hail, dust and a variety of other harsh environmental factors. Aside from the elastic band getting dirty there is no noticeable wear on the device itself. (The band can be easily washed with soap and water.) A new band can be purchased for $25 in a different color if desired or if the elastic wears out over time, though this hasn’t happened to mine.

Changes for the Next Model:

A battery indicator on the device would be handy, but it is certainly not imperative. My watch does give me an alert when the heart rate monitor battery is very low. But it would be nice to know before it is “mission critical.”

The True Test – Would You Recommend It?

Yes, absolutely! I often recommend the COROS Heart Rate Monitor to the athletes I coach and to friends who are looking for a more accurate heart rate monitor and/or do not care for chest straps.

Keeping it Honest – Did You Get This Gear for Free?

I did not get this device for free nor do I currently receive any compensation for recommending/reviewing this product.

Dandelion Dilluvio-Scott is a multisport outdoor athlete, ultra-runner and certified coach. She is passionate about collaborating with driven athletes who love to explore, train and play outside.

Zone Training for Runners

Introducing Zone Training

As a high school runner, before I knew anything about zone training, my coach would provide me training programs every month. A departure from the tools that we utilize today, these programs were always crafted on pen and paper. Words like “Easy” or “Steady” were used to indicate intensity. Though I had an implicit understanding of what this entailed back then, by today’s standards this language may be seen as vague or ambiguous. 

Being a runner in 2024 comes with the opportunity to utilize a variety of tools, built to aid in training and race-day performance. After each run, my Garmin feels compelled to tell me how I’m progressing in my training. Other gadgets on the market, like Whoop’s wristbands and Stryd’s running power meters, add even more layers of information. Gone are the days of pen-and-paper training plans. Today, quantitative data has won the hearts and minds of runners across the globe.

Ryan Woolley racing on the trails with the help of an advanced GPS watch shows how much technology has evolved.
Ryan Woolley racing on the trails with the help of an advanced GPS watch shows how much technology has evolved.

The heart rate zones framework has been a popular reference point for those who are choosing to organize training load according to one particular piece of data – heart rate, collected from either the wrist, upper arm or chest. Heart rate can be correlated with intensity during endurance training. Considering this, coaches and athletes can plan training sessions to fall within a certain intensity range. The desired intensity depends on the goal race, workout purpose and stage in a training cycle. Understanding how to apply these zones is crucial for progressing toward a big race or adventure while managing rest and recovery.

This article is for those who want to make sense and use of heart rate zones. We’ll start by defining heart rate zone training and some it’s nuances. Then we’ll move onto discussing how to apply the framework during your next training block.

What Are Heart Rate Zones?

Heart rate zone training comes from the understanding that the body controls for energy production according to its rate of work. For example, the mix of energy systems used in a 1-mile race differ significantly from those used in a marathon. Heart rate zone training is utilized with the intention of building volume (or time) spent running at race specific intensities. This protocol consists of dividing ranges of exercise intensity into segments that are each associated with a heart rate range. The intensity range goes from walking to maximum sustained exertion running.

The number of zones and how they’re structured will often vary depending on the creator. For simplicity, I’ll reference a 5-zone framework in this article (below). However, other zone frameworks consist of 4 or even 3 zones in association with intensity-related metabolic changes.

ZoneNameIntensityUse
1Active RecoveryVery LightHiking, active recovery
2EasyLightEasy days, medium/long runs
3AerobicModerateTempo work
4ThresholdHardStrength-based intervals
5VO2 MaxMaximumPower-based intervals

The Wandering Heart and You

Here’s the deal with your heart rate while running: it’s not always a perfect indicator of effort. During long efforts, for example, heart rate can slowly increase over time. This is known as cardiac drift, occurring in response to an increase in the body’s core temperature and sweat losses. As such, running in hot environments can create a bigger discrepancy between heart rate and perceived effort.

Additionally, heart rate numbers during submaximal exercise can be swayed by our emotions – a charged atmosphere can lead to higher average heart rate values due to an increase in sympathetic nervous system tone.

Experience level also plays a role. Seasoned runners are able to pump more blood per beat to the working muscle. This allows them to maintain lower heart rates at higher efforts. In contrast, those who are new to the sport may see higher heart rate values relative to the same level of perceived effort. 

Given these variables, it’s clear that heart rate numbers should be taken with a grain of caution. But if heart rate can sometimes mislead, how do we make sense of our training? Connecting intensity zones with target race paces can help to create a more complete picture. 

Ryan Woolley running an ultra trail race.
Ryan Woolley running an ultra trail race. (Check out his TRR hat here!)

The “Golden” Zone 2

Zone 2 training is often hailed as the “golden” zone for distance runners. For the past few years, influential coaches, physiologists and runners alike have been taking to social media and speaking to the sweet, sweet taste of this secret sauce. The perfect amount of Zone 2 running (approximately 60 – 70% of maximum heart rate) to add to any training recipe, they say, is 80% of total volume. Regardless of how much time it contributes toward your weekly volume, running within the lower zones of 1 and 2 allows you to build a strong aerobic engine without risking mechanical failure.

What does Zone 2 feel like?

As they say, keep it conversational. Learn how to breathe deep and sink into an easy rhythm. To ensure that you’re not feeling any pressure to maintain a set pace, run to duration on these days. Runners I coach slowly progress up to an hour of running at this intensity before I introduce any harder running. The less experience you have, the more time you’ll need to spend running within this zone each week. 

Which Zone and When?

After building a foundation of easy Zone 1 and 2 running, you can start to build volume around harder efforts. The next zone up will typically be the main intensity range that you live in during a marathon. Workouts in Zone 3 might include tempo runs or long intervals at marathon pace, equivalent to a steady, harder than easy but controlled, effort. Start by running for 20 minutes at your target marathon pace, before progressing this workout by adding time, or by slowly increasing your speed towards the end. If you’re really struggling for air at the end of these workouts, adjust your goal times accordingly. Alongside Zone 2 days, one of these sessions per week is plenty.

Once you feel that your body is starting to recover well from Zone 3 work, you can add a little spice with Zone 4 training. Aim to spend more time here if you’re looking to perfect the 5 and 10 kilometer distances.

Zone 4 interval training allows you to safely build volume at this intensity. Considering that you’re likely working within the Zone 4 heart rate range during 5 kilometer and 10 kilometer races, any interval training may be modeled off these target paces. Start with 2 to 3 minute intervals at your target 10 kilometer race pace, before introducing shorter intervals – 300 to 400 meters – at 5 kilometer race pace. Focus on starting small, before slowly increasing the number of intervals while maintaining a consistent pace. Try to keep the recovery to no more than the equivalent of the interval duration. If you find that you need more recovery time to keep a consistent pace, take your foot off the gas and slow down your target times. Treat Zone 4 work as the crescendo of your training block.

During your final weeks of preparation toward a key race, your week will likely include one Zone 3 day, Zone 4 interval day, as well as one day dedicated to running long in Zone 2.  

Zone 4 intervals helped prepare Ryan Woolley for a shorter distance XC race.
Zone 4 intervals helped prepare Ryan Woolley for a shorter distance XC race.

Final Note on Zone Training

When thinking about the zones framework, context is everything. Three things to consider when organizing your next training block are your:

1) Level of experience

2) Current state of fitness

3) Target race, goal or adventure

Within the design of any program, your progression in training should always be cyclical. At each stage in the cycle of your training block, a different zone will become the focal point. The amount of volume that you work up to within each zone will depend on the intensity range that you’ll be utilizing the most while trying to hit your next running goal. In that sense, heart rate zone training should never exist in a vacuum. Instead, consider the zones as a collection of tools – at any given time, the one that you use will depend on the project at hand. 

References

Power, S. K., Howley, E. T., & Quindry, J. (2008). Exercise Physiology: Theory and Application to Fitness and Performance. McGraw Hill: New York, NY.

Ryan Woolley is a coach with Team RunRun based in New Zealand. As a coach, he focuses on strength for performance and injury prevention. He uses his 20 years of competitive experience across many distances and terrains to guide his athletes towards their goals. Ryan also has a strong technical understanding of exercise physiology (BSc, MA) and applies it to his coaching.

Heart Rate Zone Training Explained: Train Harder, Run Faster

Introducing Zone Training: It’s More Than the Heart Can Tell

Long before I knew anything about zone training, as a high school runner, my coach handed me training programs every month or two. These weren’t like the high-tech tools we have today—they were simple, handwritten plans, often scribbled with words like “Easy” or “Steady” to indicate intensity. On Sundays, I’d run for two hours, timing myself with an Ironman watch that could store over 100 laps, which was a big deal back then (I’m 35 now).

Fast forward to today, and running has evolved with a plethora of tools designed to enhance training and race performance. A few years ago, I upgraded to a Garmin watch, and suddenly, I was drowning in data. My watch now constantly updates me on my progress, while other gadgets like Whoop’s wristbands and Stryd’s running power meters add even more layers of information. The days of pen-and-paper training plans are long gone—now, data reigns supreme, helping athletes and coaches fine-tune training and optimize performance.

One of the most widely used frameworks in this data-driven world is heart rate zone training. This method organizes training intensity based on heart rate, which can be measured via the wrist, upper arm, or chest. By staying within specific heart rate zones, athletes can plan their sessions to align with their goals and current fitness levels. Understanding how to apply these zones is crucial for progressing toward a big race or adventure while managing rest and recovery.

This article is for those who want to make sense of heart rate zones and apply them to their own running. We’ll start by defining zone training, explore how the body responds at different intensities, and then discuss how to tailor training zones for your next training block.

Ruby Wyles using data from her watch to help her training.
Ruby Wyles using data from her watch to help her training.

What Are Heart Rate Zones?

Heart rate zone training is based on the idea that the body’s energy production changes depending on its rate of work. For example, the energy systems used in a 1-mile race differ significantly from those used in a marathon. Heart rate zones help runners spend the right amount of time at race-specific intensities, optimizing performance.

The number of zones can vary depending on the model used. Polar, for instance, divides training into five zones, each representing 10% increments of your maximum heart rate. Other models might use three or four zones or split them further. For simplicity, I’ll reference a 5-zone framework in this article:

ZoneNameIntensityUse
1Active RecoveryVery LightHiking, active recovery
2EasyLightEasy days, medium/long runs
3AerobicModerateTempo work
4ThresholdHardStrength-based intervals
5VO2 MaxMaximumPower-based intervals

The Wandering Heart and You

Runner training with a chest strap to accurately measure her heart rate while running.
Ruby Wyles training with a chest strap to accurately measure her heart rate while running.

Here’s the thing about heart rate during running: it’s not always a perfect indicator of effort. For example, during sustained efforts, your stroke volume—the amount of blood pumped per heartbeat—decreases as body temperature rises. To compensate, heart rate increases, a phenomenon known as cardiac drift. On hot days, this drift can make your heart rate seem higher than your perceived effort, leading to misleading data.

Additionally, emotions can also affect heart rate. A charged atmosphere, like a race day, can elevate your heart rate due to an increase in sympathetic nervous system activity. Experience level also plays a role. Seasoned runners often have a more efficient stroke volume, allowing them to maintain lower heart rates at higher efforts. In contrast, newer runners might see their heart rates spike more quickly.

Given these variables, it’s clear that heart rate numbers should be taken with a grain of caution. But if heart rate can sometimes mislead, how do we make sense of our training? Understanding how the body reacts at different intensity zones can help.

What Happens at Different Exercise Intensities?

Incremental exercise tests (IET) are used to determine how the body’s metabolic systems respond to increasing heart rate and pace. These tests can reveal how heart rate and energy systems interact as you move through different zones.

Rewind to high school biology and you’ll remember that the body has three types of muscle fibers: Type 1, Type 2a and Type 2x. Type 1 are typically referred to as “slow twitch”. These fibers are great at handling energy metabolism at low intensities, in those first two zones. Compared to Type 1 fibers, Type 2 fibers are able to produce more force, allowing you to reach higher intensities. One major adaptation to long term endurance exercise is the body’s conversion of Type 2 muscle fibers to the more fatigue-resistant and efficient Type 1 fibers.

At the beginning of a run, your parasympathetic nervous system relaxes its grip, allowing your heart rate to rise to about 100 beats per minute. As you increase intensity, the sympathetic nervous system takes over, boosting heart rate further to deliver more oxygen to your muscles. Initially, Type 1 muscle fibers handle the work, using oxygen to produce energy through aerobic metabolism. As intensity ramps up, Type 2a fibers join in, using glycolysis, which produces lactate as a byproduct.

When the body reaches the point where lactate production begins to outpace its clearance—known as ventilatory threshold 1 or the aerobic threshold—you’re typically in Zone 3. Training in this zone builds your aerobic engine without overwhelming your muscles with fatigue.

As you push harder, moving into Zone 4, you hit your lactate threshold, the point at which exercise becomes anaerobic. This is your aerobic ceiling, where the body struggles to keep up with the demands for oxygen, and lactate starts to accumulate faster than it can be cleared. Training at or slightly above this threshold can significantly improve your body’s ability to sustain higher intensities.

Finally, at maximum effort, you reach VO2 Max—your body’s maximum capacity to use oxygen. This is where the work feels hardest, and fatigue sets in quickly.

Which Zone, and When?

When planning your training, context is everything. Consider your experience level, current fitness, and target race or adventure when deciding which zones to focus on.

Zone 2 training is often hailed as the “golden” zone for distance runners. Many experts recommend spending about 80% of your training time in this zone, as it builds a strong aerobic base without risking mechanical breakdown. Early in a training block, most of your running should be within Zones 1 and 2, allowing your cardiovascular system to adapt safely.

Once you’ve built a solid foundation, you can start incorporating harder efforts from Zone 3. This zone is crucial for marathon training, where the intensity is higher, but still primarily aerobic. Workouts in Zone 3 might include tempo runs or long intervals at marathon pace. Workouts at this intensity help you build strength and endurance for race day.

As you progress, Zone 4—threshold training—becomes important, especially for shorter races like 5Ks and 10Ks. Zone 4 intervals help your body handle the demands of faster paces, improving your ability to sustain high efforts.

Throughout your training, remember that these zones are tools, not rules. Use them to guide your workouts, but be flexible and adjust based on how your body responds. The goal is to find the right balance that prepares you for your next running challenge.

In summary, heart rate zone training offers a structured approach to running that can help you achieve your goals. Whether you’re aiming for a marathon or just looking to improve your fitness, zone training has benefits for all runners. By understanding how your body responds at different intensities and applying that knowledge to your training, you can make the most of each run and set yourself up for success.

References

Power, S. K., Howley, E. T., & Quindry, J. (2008). Exercise Physiology: Theory and Application to Fitness and Performance. McGraw Hill: New York, NY.

Looking for more information about different training intensities? Check out: “Why Running Slow Helps You Run Fast with Coach Dan Lyne“.