Training Zones are a way to classify and categorize training. They distinguish between variations of hard and easy. Some coaches use a 3-zone model, others 5-zone. To determine your zones, you do an assessment, and regular assessments will give you metric feedback to measure your progress. 

There are four ways to measure intensity: pace, heart rate, power, and rate of perceived effort. Power is your absolute measure of work, heart rate is a variable to measure how your body is responding to that work, and the subjective measurement of effort gives you feedback relative to other sessions. 

Once you have chosen which method of monitoring intensity in your training plan (and you may use more than one), you need establish personal intensity zones for that specific metric, which is done through lactate threshold testing or the 1k swim test, 20-30 minute bike test, and 5k-10k run test within your plan.

Lactate threshold is defined as the exercise intensity at which lactate, an intermediate product of glucose metabolism, begins to accumulate in the blood. In practical terms, it’s the highest exercise intensity that can be sustained for up to 60 minutes. The most reliable test for use in identifying appropriate individual training intensities are those that pinpoint the lactate threshold (LT).  In simple terms,  your threshold is simply a repeatable measure of your current fitness. Adding your latest  threshold to TrainingPeaks helps you to track your improvements and enables you to create your own accurate training zones.

Our training plans on training peaks, use workout builder so you can sync the detail on training peaks to your monitoring device. Once you determine your predicted threshold,  you can enter it in the training peaks calculator to determine your zones. Once you have a set of accurate training zones, you’ll be able to see exactly how hard or easy to swim during your workouts, based on your own current fitness. 

Intensity used in our training plans is based on using rate of perceived effort since everyone does not own a power meter or heart rate monitor to guide intensity and I believe if you use those tools, you should also learn Rate of Perceived Effort. There are no magic zones, or magic paces/power outputs/ or lactate readings. Everything is a stimulus that can potentially lead to an adaptation.

The testing protocols within your plan allow you to use any or all of the above.  Each metric  has certain advantages and disadvantages. Power is an output, pace is an outcome, and heart rate is an indicator. 

• Power is the output, and represents actual work performed regardless of terrain, grade, or environmental factors.
• Pace indicates the speed, or outcome and varies with terrain, grade and environmental factors 
• Heart rate represents how your heart is responding to the output and environment and varies with weather, nutrition, sleep, caffeine to name a few

Examples of how each is applied to a training session  

• During a hilly ascent on the bike or run,  the output (power) will be high, heart rate might be elevated while the outcome (speed) will be low. In this case, power is best to monitor intensity, then heart rate, not pace
• During training on a hot day,  your heart rate might be very high, while power and pace are low, and remain elevated even when you stop at a stoplight with zero power or speed.  For this reason, power is considered superior to pace, and pace can be superior to heart rate to measure intensity. 

The best measure of intensity and training load is the train with a power meter because it provides instant feedback on cycling and running output and is not compromised by terrain or temperature.

Pace is useful because it’s a performance-relevant variable. You are racing the clock or a competitor. Just understand, pace becomes unreliable when you’re running uphill or downhill.

Heart rate measures how your body is responding to training, it is not an output or outcome. It is useful because it helps triathletes avoid the single most common training mistake: pushing too hard in workouts that are supposed to be done at low intensity (Zones 1 and 2). But heart rate is not a reliable way to monitor intensity during short efforts at high intensity because heart rate lags behind abrupt changes in pace. HR for a given effort is also easily influenced by environmental factors, such as temperature. 

Rate of Perceived Effort is your subjective sense of how hard you are training is important because it ultimately determines how fast you go in events. You may set time-based goals, but perceived effort has the final say in deciding whether you actually do maintain your goal pace or speed up or slow down. Whenever possible, use technology to help you learn RPE and use RPE to help you understand metrics. RPE is the only reliable method to measure intensity of short duration. For example, when running short intervals up hills, Pace zones are invalid and the interval may be too short for Heart Rate to “catch up.” 

If you do not have a power meter, a combination of RPE, pace heart rate is best, using RPE to monitor pace and heart rate as you get more experience you will be happy to understand all three.

There’s nuance in training so embrace it and get creative for hard and easy workout details. Your goal is to stress the body, rest to adapt. Don’t drive yourself nuts measuring things that may understand and may not matter.