Maximal Aerobic Speed (MAS): Why It Matters for Percentage-Based Running Programs
Why MAS Matters in Training Programs Using Percentage Runs
When designing running programs, whether for team sports, endurance athletes, or individual performance, one of the most misunderstood concepts is Maximal Aerobic Speed (MAS). While athletes and coaches often rely on perceived effort, pace, or heart rate zones, MAS offers a scientifically precise way to structure training intensity. Here is why MAS is critical when using percentage runs in training programs.
What is MAS?
MAS is the minimal speed at which an athlete reaches their VO₂ max, the maximum rate at which the body can consume oxygen during intense exercise. In simpler terms, it is the fastest pace you can maintain whilst still relying predominantly on your aerobic energy system.
Knowing your MAS allows you to prescribe training intensities that are accurate, individualized, and effective, rather than guessing based on time, distance, or subjective effort.
Why Percentage Runs Are Popular
Many programs structure running sessions around percentage-based paces, such as 50%, 60%, 80%, 95%, or 100% of MAS. This method allows for individualization because every athlete has a unique fitness profile. Running 15 km/h might be easy for one person and unsustainable for another, so using percentages of MAS ensures each athlete trains at the right intensity for them.
Precision training is another benefit, as running at the exact physiological intensity needed to stimulate adaptation helps athletes improve efficiently without overtraining. Consistency is also improved since all athletes train at comparable relative intensities, which is especially important for team sports with mixed fitness levels.
How Do You Know What 50%, 60%, or 80% of Max Effort Is?
Many athletes rely on “max effort” as a subjective guide, but this can be misleading. The most accurate way to determine percentages of maximal effort is to use MAS as the reference. For example, if your MAS is 16 km/h, 50% MAS equals 8 km/h, 60% MAS equals 9.6 km/h, and 80% MAS equals 12.8 km/h. This ensures every percentage effort is truly relative to your current fitness.
Fitness changes over time, so percentages of MAS from previous months might no longer reflect your ability. At The Sports Recovery Hub, we take the guesswork out of it. Using 1.5 km or 2 km time trials, we regularly update your MAS and calculate your current training percentages. This ensures your 50%, 60%, 80%, or 95% sessions are always accurate and tailored to your fitness.
MAS also correlates strongly with certain heart rate zones. For instance, 50–60% MAS corresponds to a light aerobic or recovery pace, 70–80% MAS aligns with a moderate aerobic or tempo pace, and 90–100% MAS targets VO₂ max and high-intensity intervals. Combining heart rate monitoring with MAS provides an additional check on effort.
Finally, perceived effort can serve as a backup. Rating of Perceived Exertion (RPE) roughly aligns with percentage MAS. A 50% MAS session corresponds to an RPE of 3–4 out of 10 (easy), 60% MAS corresponds to RPE 4–5 out of 10 (comfortable), and 80% MAS corresponds to RPE 6–7 out of 10 (challenging but sustainable). Using MAS ensures your percentages are anchored in actual performance data, not guesswork.
Quick Reference Table: Percentage MAS, Pace, and Perceived Effort
Note: Paces are calculated based on an example MAS of 16 km/h. Your MAS may differ, which is why our MAS check-in sessions using 1.5 km or 2 km time trials are essential to update your percentages accurately.
How MAS Improves Training Programs
Running slightly below MAS, around 85–90%, enhances aerobic capacity without inducing excessive fatigue. This builds a strong aerobic base for recovery, repeated sprints, and long-duration performance. Running at or slightly above MAS targets VO₂ max development, maximizing cardiovascular adaptations. Structuring intervals based on percentages of MAS ensures the intensity is high enough to improve fitness but sustainable enough to complete the session.
Without MAS, athletes may overestimate pace or intensity, which can lead to fatigue, poor recovery, or injury. Using percentage MAS provides a controlled, evidence-based framework to balance stress and recovery. As fitness improves, MAS increases. By recalculating percentages of MAS periodically with our check-in sessions, we can adjust intensity over time, ensuring continuous improvement and avoiding plateaus.
Practical Example
Consider a 4 × 4-minute interval session. If an athlete’s MAS is 16 km/h and the session intensity is set to 95% of MAS, their running pace will be 16 × 0.95, which equals 15.2 km/h. Using MAS ensures the athlete is running hard enough to stimulate VO₂ max adaptations without risking excessive fatigue from running arbitrarily fast.
Conclusion
Using MAS to structure percentage runs is not just a training gimmick; it is a science-backed approach that enhances aerobic capacity, prevents injury, and ensures each athlete trains at their ideal intensity. By understanding what 50%, 60%, or 80% of your maximal effort truly is, and keeping your percentages updated through our MAS check-in sessions, you can train smarter, avoid overtraining, and maximize performance gains.
Measuring MAS and building your programs around it is the difference between running blindly and running with purpose.
Email us about our MAS calculation services today: tmbcsports@gmail.com
