Zones and Stages of Cardio Training

Matthew Barrett
Oct 23
4 min read

Move Safe, Get Fit: A Trainer’s Guide to Smarter, 5-Stage Cardio

When most people think of "cardio," they picture long, boring slogs on the treadmill or elliptical. It's often seen as a necessary evil for burning calories. But what if your cardio programming was just as precise, progressive, and personalized as your strength training?

As a trainer, I approach cardiovascular conditioning with a plan. It’s not just about "doing cardio"; it's about doing the right cardio for your body, your goals, and your current fitness level. Here’s a look at how I build a smarter cardio plan from the ground up.

Part 1: Safety First (The Corrective Exercise Lens)

Before we even talk about stages, zones, or intensity, my first priority is safety.

I always look at cardio through the lens of corrective exercise. Why? Because performing a repetitive motion like running, cycling, or rowing with underlying movement compensations is a fast track to injury.

If your ankles collapse, your knees cave in, or your back rounds, doing that thousands of times over 30 minutes will only reinforce the problem. We don't want to burn calories at the expense of tearing an ACL or developing chronic low-back pain.

So, Step 1 is always to assess your movement patterns. We ensure you can move well, and if not, we build a plan to correct it. Only then do we start adding intensity and duration.

Part 2: Finding Your "Just Right" (How We Measure Intensity)

Once we know you're moving safely, we need a way to measure intensity. Just "going hard" isn't a plan. We need data. While tools like Heart Rate Reserve (HRR) exist, I find they can be less reliable. Instead, I focus on two key methods:

1. Rate of Perceived Exertion (RPE)

This is the simplest and most accessible tool. It's a 1-10 scale where you rate how hard you feel you're working. It teaches you to listen to your body.

1: Very Light (watching TV)
3-4: Moderate (can talk easily)
5-6: Heavy (can still talk, but in shorter sentences)
7-8: Very Heavy (can only manage a few words)
9-10: Very, Very Heavy (all-out effort, can't talk)

2. Ventilatory Threshold (VT1 & VT2)

This is a more clinical way to measure your body's response to exercise.

VT1 (Ventilatory Threshold 1): This is the point where breathing starts to become more rapid. You can still talk, but you'll notice you're "winded." This is the dividing line between easy and moderate-intensity work.
VT2 (Ventilatory Threshold 2): This is the point where you can no longer speak comfortably. You've crossed into high-intensity work, and your body is relying heavily on anaerobic energy.

The 4 Training Zones

These measurements allow us to create precise training zones. Everything we do will be targeted to one of these zones.

Zone 1: Below VT1 (RPE 3-4). This is your "recovery" or "easy day" pace. You can hold a full conversation.
Zone 2: From VT1 to the midpoint before VT2 (RPE 5-6). This is your "challenging but sustainable" pace. Great for building aerobic endurance.
Zone 3: From the midpoint to just below VT2 (RPE 7-8). This is "hard" work. You're breathing heavy and can't say much.
Zone 4: At and above VT2 (RPE 9-10). This is an all-out sprint or "max effort" that can only be held for a very short time.

Part 3: The 5 Stages of Cardio (Finding Your Perfect Fit)

With our safety check and intensity zones established, we can now find the right stage for you. This progressive 5-stage model ensures you're always working at a level that is productive, not destructive.

Stage 1: Building a Base

Who it's for: Sedentary or deconditioned individuals, or anyone just starting their fitness journey.
The Goal: To build a solid aerobic base, improve recovery, and get the body used to consistent work.
What it looks like: All training is done in Zone 1 (RPE 3-4). It's all about consistency and duration, not intensity.

Stage 2: Introducing Intervals

Who it's for: Individuals who want to improve health, manage weight, or reduce body fat. This is where most people live.
The Goal: To increase the aerobic and anaerobic capacity and burn more calories.
What it looks like: We spend most of the workout in Zone 1, but we introduce short intervals into Zone 2 (RPE 5-6). For example: 3 minutes in Zone 1, followed by 1 minute in Zone 2, and repeat.

Stage 3: Building Endurance

Who it's for: Moderately-to-highly conditioned clients who want to improve their performance and endurance.
The Goal: To increase the body's ability to handle harder work for longer periods.
What it looks like: This is a more advanced interval workout that rotates through three zones. For example: A warmup in Zone 1, followed by intervals that climb from Zone 2 up into Zone 3 (RPE 7-8), and then back down.

Stage 4: Performance Peaks

Who it's for: Advanced clients and athletes who are highly conditioned and focused on peak performance.
The Goal: To develop maximum anaerobic power and push the limits of performance.
What it looks like: This is true High-Intensity Interval Training (HIIT). Workouts involve intervals that push all the way into Zone 4 (RPE 9-10), with longer recovery periods in Zone 1. This stage is extremely demanding and not appropriate for most general-fitness clients.

Stage 5: Elite Sport

Who it's for: Elite athletes.
The Goal: To maximize sport-specific power and performance.
What it looks like: This is a complex program that combines all four zones in a way that directly mimics the demands of a specific sport.