How to Improve as an Endurance Athlete: The Metrics That Matter Most

Are you training for your first Ironman? Want to get faster at the 70.3 distance or marathon? Or maybe you just want to feel fitter and healthier without figuring it all out on your own? You’re not alone—and you’re in the right place. Join Coach Chris Newport as she dives into how to improve as an endurance athlete, including following the right metrics to better measure your progress.

Improving as an endurance athlete isn’t just about working harder—it’s about working smarter. And to do that, you need to be tracking the right things. In this blog/podcast, we’re breaking down the most important performance metrics you should be paying attention to if you want to build fitness, avoid burnout, and see results.

Training Load: Volume, Intensity & Thresholds

Training creates stress on your body. When that stress is applied in the right dose and followed by adequate recovery, you get stronger. But go too hard or too long without rest, and you risk overreaching—or even overtraining.

Start with these fundamentals:

Training Volume: How much time or distance you’re training each week.
Intensity: How hard you’re working, often tracked via heart rate or power.
Heart Rate Zones: These must be individualized, ideally tested—not just estimated. Learn more about our metabolic testing here.
Power Zones (Cyclists): Based on FTP or a field test and should be updated regularly.

Your training needs to challenge you without crushing you—and proper zone setting is the hallmark to any training plan.

Recovery & Readiness: Tools to Track Adaptation

You don’t get stronger during the workout, you get stronger after your RECOVER from it. That’s why recovery metrics are just as important as training metrics.

Here’s a few to track:

HRV (Heart Rate Variability): Measures nervous system recovery. Higher = better readiness.
Sleep Quality: Your #1 recovery tool. Poor sleep undermines every part of your training (and your metabolism, brain health and more)
Resting Heart Rate (RHR): Elevated RHR can indicate fatigue or illness.
Subjective Well-Being: Don’t ignore things like mood, motivation, and soreness. We have our athletes use this in several of the software tools we use (measured in easy-to-understand “smiley” face).

Training Stress Scores (TSS, CTL, ATL, TSB)

If you’re using TrainingPeaks, like we do with our athletes, you have access to some incredibly helpful metrics (assuming you have premium, which we provide free of charge for our athletes):

TSS (Training Stress Score): Combines intensity + duration to quantify workout load.
CTL (Chronic Training Load): Tracks long-term training trends (your “fitness”).
ATL (Acute Training Load): Tracks recent fatigue (your “tiredness”).
TSB (Training Stress Balance): Indicates your current form/readiness to perform.

Together, these help you monitor progress over time and adjust your plan as needed.

Technique, Strength & Gear

Performance gains aren’t just about fitness. They’re also about efficiency. Small changes in technique, strength, or gear can lead to big improvements.

Consider:

Form & Technique: Swimming stroke, running gait, bike fit—all impact efficiency.
Mobility & Strength: Regular assessments help prevent injury and support power.
Gear: proper fitting running shoes made of optimal materials for your goals, the right crank arm length for your body, and the best cooling vest are a few to name.

These can be hard to evaluate on your own. This is where a coach (and sometimes a PT or bike fitter) can really make a difference.

Advanced Metrics for the Data Nerds

If you love digging into the numbers, here are a few more to consider:

Fueling & Hydration Logs: Crucial for energy, recovery, and race-day success. This is part of what we do in the Fueling & Hydration Bootcamp.
Menstrual Cycle Tracking (for women): Hormonal shifts can impact energy, sleep, and strength. We dig more into this in our Longevity program.
Environmental Stress: Acclimating to heat, humidity, or altitude can change training response. Again, we dig into this in the Fueling & Hydration Bootcamp (since they all affect hydration status).

The Bottom Line: Don’t Just Train—Measure What Matters

Improvement in endurance sports doesn’t happen by accident. It happens when you set goals, track the right things according to those goals, listen to your body, communicate with your coach (or have the self-awareness and discipline to evaluate yourself) and adjust your plan accordingly. And if you’re tired of guessing, we’re here to help.

Work with Us

Our 1-on-1 endurance coaching services give you the guidance, accountability, and strategy to train smarter—not harder. Want to learn more? Learn more and apply for limited spots here.