How Do You Know If You Need Endurance Training or Sprint Intervals?

Most athletes follow generic training plans without knowing what their body actually needs. Some pile on endless base miles when they need high-intensity work. Others hammer intervals when they need aerobic development. What if a simple test could tell you exactly which type of training your physiology demands?

Using muscle oxygen monitoring, you can identify whether your focus should be endurance base building or interval-focused training. Here's how to decode what your muscles are telling you.

Why Do Most Athletes Train the Wrong Energy System?

The problem with most training approaches is that they assume everyone needs the same thing. Coaches prescribe 80/20 training or pyramidal models without knowing if your aerobic system is actually your limitation.

Some athletes have excellent aerobic engines but poor high-intensity capacity. Others can generate massive power but lack the aerobic base to sustain it. Training the wrong system wastes months of effort and leaves performance gains on the table.

What Equipment Do You Need for Accurate Assessment?

Not all muscle oxygen monitors are created equal. To get reliable training guidance, you need a device that:

• Measures accurately from 0-100% (not just relative changes)
• Provides real SmO2 values (not arbitrary units or indices)
• Can isolate muscle-specific signals (not mixed tissue readings)

The Moxy Monitor meets these criteria, providing the precision needed for training decisions. Without accurate 0-100% scaling, you can't apply the thresholds that determine your training focus.

How Do You Ensure Proper Sensor Placement?

Accurate readings depend on correct sensor placement:

For Cycling/Running:

• Place on the vastus lateralis (outer thigh)
• Position halfway between hip and knee
• Ensure sensor sits flat on muscle belly
• Avoid areas with excessive body fat or hair

For Upper Body Work:

• Use biceps or triceps muscle belly
• Avoid placement over joints or tendons
• Secure firmly but don't restrict blood flow

Poor placement leads to inaccurate readings and wrong training prescriptions.

What Test Should You Perform?

You have two testing options:

Option 1: Step Test Protocol

• 3-minute stages at increasing intensity
• Start easy, increase power/pace each stage
• Continue until exhaustion
• Monitor SmO2 throughout

Option 2: 3-1 Assessment

• 3-minute work intervals
• 1-minute rest between stages
• Increase intensity each work period
• Track SmO2 during work and recovery

Both protocols can provide insights to your aerobic and anaerobic capabilities through muscle oxygen patterns but if you are trying to identify which system to focus on the 3-1 assessment is preferred. 

How Do You Interpret Your High SmO2 Values?

During easy stages of your test, look at your highest SmO2 readings during work and rest:

SmO2 BELOW 60% During Easy Efforts = More Cardiovascular Development Needed

Low SmO2 values during easy exercise indicate poor oxygen delivery capacity. Your cardiovascular system can't efficiently transport oxygen to working muscles, even at low intensities.

Why This Happens:

• Limited cardiac output
• Poor capillarization
• Inadequate blood volume

The Solution: Base Building and Heat Training

When your easy-pace SmO2 stays below 60%, you need aerobic system development:

• Long, steady sessions at comfortable intensities
• Higher training volume at low to moderate intensities
• Consistent aerobic stress to drive cardiovascular adaptations
• Patience - these adaptations take 6-12 weeks to develop
• Heat Training: Heat training is a very powerful way of improving your cardioavascular system, follow the 5, 50, 5 rule. Exercise in the heat at a rating of perceived exertion of 5, 50 minutes a day, for 5 weeks or more.
• Complete 4-5 Sessions per week (ensure 1 higher intensity session each week for a more rounded training program). 

Think of this as building your aerobic engine. You can't run high-performance software on inadequate hardware.

How Do You Analyze Your Low SmO2 Values?

During high-intensity stages, examine your lowest SmO2 readings:

SmO2 DOESN'T DROP BELOW 50% = Sprint Training Needed

If your SmO2 never drops below 50% during hard efforts, your muscles aren't efficiently extracting oxygen. You have plenty of delivery but poor utilization.

Why This Happens:

• Limited mitochondrial capacity
• Poor oxygen extraction efficiency
• Underdeveloped high-end power
• Insufficient neuromuscular recruitment

The Solution: Sprint Training with Repeat Desaturation

When your high-intensity SmO2 stays above 50%, focus on:

• Short, intense intervals that drive SmO2 very low
• Brief work periods (15-90 seconds)
• Long recovery until SmO2 reaches peak values (60-120+ seconds)
• Repeat desaturation to train oxygen extraction

The goal is to teach your muscles to efficiently use available oxygen and develop anaerobic power systems.

What Does Repeat Desaturation Training Look Like?

This specific protocol targets oxygen utilization:

The Structure:

• Work hard enough to drive SmO2 below 30% if possible
• Stop the interval when SmO2 plateaus at its lowest point (even if it’s above 30%)
• Rest completely until SmO2 returns to peak values
• Repeat 4-8 times per session - start with 4 and build
• Do 2-3 Sessions per week - start with 2 and build

Example Workout:

• 30-second all-out efforts
• Complete rest until SmO2 peaks (usually 2-4 minutes)
• Repeat 6 times
• Focus on driving SmO2 as low as possible each interval

What If You Need Both Types of Training?

Some athletes show limitations in both areas:

• Low SmO2 during easy efforts (need aerobic base)
• Poor desaturation during hard efforts (need sprint work)

The Periodization Approach:

• Address aerobic limitations first with 4-6 weeks of base building
• Add 1 Sprint workout per week
• Retest to confirm improvements in easy-pace SmO2 values
• Add sprint work on top of volume building once aerobic base is established
• Maintain balance between systems moving forward

Building the aerobic foundation first provides the platform for effective high-intensity training.

How Often Should You Reassess Your Training Needs?

Your limitations change as you adapt to training. Retest every 6-8 weeks to:

• Track improvements in your limiting factor
• Identify when to shift training focus
• Ensure you're always targeting the right system
• Avoid stagnation from training the same way too long

Why Does This Approach Work Better Than Generic Plans?

Traditional training prescriptions are based on population averages, not your individual physiology. This muscle oxygen approach:

• Identifies your actual limitations instead of assumed ones
• Provides objective markers for training decisions
• Tracks physiological adaptations in real-time
• Prevents wasted training time on irrelevant systems

What's Your Next Step?

Stop guessing what type of training you need. One properly executed test with accurate muscle oxygen monitoring can redirect months of training toward what actually matters for your performance.

Whether you discover you need more aerobic base or better oxygen utilization, you'll finally have a clear roadmap for training that matches your physiology. Your muscles have been telling you what they need – now you know how to listen.

Want to learn more about how to use Muscle Oxygen for training and racing? Download our FREE eBook Training and Racing with Moxy