For marathon runners, the quest for a reliable race-day predictor is nearly as enduring as the 26.2-mile race itself. Among the myriad of formulas and benchmark workouts, Yasso 800s stand out as a legendary, almost mythical, training session used by athletes to forecast their potential marathon finish time. Developed by Bart Yasso, the former Chief Running Officer at Runner’s World, this workout involves running ten 800-meter repeats on a track, typically several weeks before race day. The core principle is deceptively simple: the average time in minutes and seconds for the 800-meter intervals is believed to correlate directly to a marathon finish time in hours and minutes, making it a powerful tool for goal setting and a formidable test of fitness.
What Are Yasso 800s?
At its heart, the Yasso 800s workout is a specific type of interval training designed for marathoners. It consists of a main set of ten repetitions of 800 meters, which is equivalent to two laps around a standard 400-meter track.
The “magic” of the workout lies in its predictive power. You take your average time for completing each 800-meter run, expressed in minutes and seconds, and translate that figure into hours and minutes. This new number becomes your predicted marathon finish time.
For example, if your goal is to run a 3-hour and 45-minute marathon, you would aim to run each of your ten 800-meter repeats in 3 minutes and 45 seconds. If you successfully complete the workout and your average time is indeed 3:45, the Yasso formula predicts you are in shape to run a 3:45:00 marathon.
A crucial, and often overlooked, component of the workout is the recovery period. Between each 800-meter repeat, you should perform a recovery jog for the exact same duration as the preceding interval. So, if you ran your 800 meters in 3:45, your recovery jog should also last for 3:45 before you begin the next repeat. This equal work-to-rest ratio is what makes the workout so challenging and effective.
The Origin and the Science (or Lack Thereof)
The workout gets its name from Bart Yasso, a running icon who discovered the correlation somewhat by accident over his decades of running and coaching. He noticed that his 800-meter repeat times consistently mirrored his marathon finish times and began sharing the concept with other runners, who found similar results. It quickly grew into one of the most famous workouts in the running community.
It is critical, however, to understand that Yasso 800s are more of a well-tested observation than a scientifically validated formula. There are no peer-reviewed studies that confirm its predictive accuracy across all runners. Its effectiveness is largely anecdotal, though the anecdotes are plentiful and compelling.
The physiological reason it seems to work is that it rigorously tests your body’s ability to run at a high intensity for a sustained period. The pace of a Yasso 800 is significantly faster than your marathon pace, likely falling near your VO2 max pace—the intensity at which your body consumes the maximum amount of oxygen. By performing multiple repeats with controlled recovery, you powerfully stimulate improvements in your aerobic capacity, lactate threshold, and running economy.
Why It’s Not a Perfect Predictor
While Yasso 800s can be a useful benchmark, they are not a guarantee of race-day success. The workout has several key limitations that every runner should acknowledge.
First, it heavily favors runners who are naturally strong at middle-distance events. An athlete with a strong anaerobic system might crush this workout but lack the muscular endurance and mental fortitude to hold a steady pace for 26.2 miles. Conversely, a runner who is an aerobic “diesel engine” might struggle with the fast pace of the 800s but be perfectly capable of grinding out a solid marathon.
Second, the workout completely ignores several critical components of marathon success. It tells you nothing about your nutrition and hydration strategy, your ability to handle race-day nerves, or how your body will respond to the specific terrain of the course. Most importantly, it doesn’t replace the single most important workout for marathon success: the long run.
How to Properly Execute the Yasso 800s Workout
To get the most out of this session, whether as a predictor or simply a fantastic workout, you must perform it correctly. This is a highly demanding workout and should only be attempted after you have established a solid running base over several months.
Step 1: The Warm-Up
Never jump into a speed workout cold. Begin with 15 to 20 minutes of very easy jogging to increase blood flow to your muscles. Follow this with a series of dynamic stretches, such as leg swings, high knees, and butt kicks, to prepare your body for fast running. Finish your warm-up with four to six “strides”—short, 100-meter accelerations—to prime your neuromuscular system.
Step 2: Determine Your Pace
Use your goal marathon time to set your target for each 800-meter repeat. If your goal is a 4:15:00 marathon, your target is 4 minutes and 15 seconds per 800m. If your goal is a sub-3-hour marathon, say 2:55:00, your target is 2 minutes and 55 seconds.
Step 3: The Main Set and Recovery
Head to a 400-meter track for the most accurate measurement. Run your first 800-meter repeat at your goal pace. As soon as you finish, start your recovery jog. If your 800m took 4:00, you will jog slowly for 4:00. The recovery should be a true, easy jog, not a walk. The goal is active recovery, which helps clear metabolic waste while keeping your heart rate from dropping too much.
Step 4: Build Up Over Time
Do not attempt to run all ten repetitions the first time you try the workout. This is a common mistake that can lead to injury or burnout. Instead, build up to it gradually throughout your training cycle.
A good progression might look like this:
- 10-12 weeks before marathon: 4-5 x 800m
- 8-10 weeks before marathon: 6-7 x 800m
- 6-8 weeks before marathon: 8-9 x 800m
- 4-5 weeks before marathon: 10 x 800m
Your final, full 10-repetition workout should be performed no later than three to four weeks before your race to allow for adequate recovery and tapering.
Step 5: The Cool-Down
After your final repetition and recovery jog, perform a thorough cool-down. This should include at least 10 to 15 minutes of very slow jogging to help your body flush out metabolic byproducts and gradually return to a resting state. Follow this with light static stretching, holding each stretch for 30-45 seconds.
Beyond Prediction: The True Value of Yasso 800s
Even if you are skeptical of its predictive power, the Yasso 800s workout is an incredibly valuable addition to any marathon training plan. When you separate it from the marathon-time correlation, you are left with a classic VO2 max interval session, which is a cornerstone of endurance training.
This workout builds fitness in several key ways. It improves your running economy, meaning you use less oxygen to run at a given speed. It also boosts your VO2 max, raising the ceiling of your aerobic potential. Finally, grinding out those last few intervals when you are already deeply fatigued is a powerful mental exercise, building the grit required to push through the final, grueling miles of a marathon.
Treating it as a tough workout rather than a pass-fail test can relieve the pressure and allow you to reap its physiological benefits. If your times are a little slow, it simply indicates an area for improvement. If they are fast, it provides a great confidence boost.
Conclusion
Yasso 800s have earned their legendary status in the running world for a reason. They offer a simple, elegant, and surprisingly effective way to gauge your marathon fitness and set a realistic race-day goal. While its predictive accuracy is more art than science, its value as a fitness-building workout is undeniable. By incorporating Yasso 800s intelligently into a well-rounded training plan that also prioritizes long runs and recovery, you are not just chasing a prediction; you are actively building the speed, strength, and mental toughness needed to make that prediction a reality.
