Polarized training is an approach to running in which the majority of training is performed at a low intensity, while a smaller portion is done at moderate and high intensities. It is sometimes described by the 80/20 rule, meaning roughly 80% of training is easy and 20% is moderate to hard. However, the ideal balance is not an exact ratio. The key principle is to spend most training time at low intensity while using higher-intensity training strategically and sparingly.
One of the biggest challenges for runners is learning to slow down. Moderate-intensity running can become habitual because it feels productive without being extremely difficult. Although running at this intensity too frequently usually does not cause a runner to regress, it can reduce the rate of improvement and eventually contribute to a training plateau. In contrast, high-intensity training is an important part of improving performance, but a little goes a long way. Excessive high-intensity training places significant stress on the body and can contribute to chronic fatigue and declining performance.
The physiological foundation of running performance is aerobic capacity, or the body’s ability to take in oxygen and use it to produce energy. Low- and high-intensity training affect the aerobic system in complementary ways. Large amounts of low-intensity running can be performed because it creates relatively little physiological stress, while its benefits continue to accumulate as training volume increases. High-intensity workouts provide powerful training stimuli, but increasing their quantity beyond what the body can recover from does not necessarily produce additional benefits.
Low-intensity, high-volume training also develops fatigue resistance and the ability to tolerate prolonged discomfort. Fast workouts may produce greater discomfort, but the discomfort ends relatively quickly. Long, easier workouts expose runners to a slower, prolonged form of fatigue that is more similar to what can be experienced during racing. This type of training teaches the mind to remain comfortable with discomfort that lasts for a long time. Prolonged low-intensity exercise can also create substantial mental fatigue, reinforcing the ability to continue performing when tired.
Another major benefit of consistent running is improved running economy. Running economy is similar to fuel economy in a car: it describes how much oxygen a runner needs to maintain a particular speed. With training, runners generally become more economical, requiring less oxygen to maintain the same pace. Running form is highly individual because every runner’s body is different, and an efficient stride does not look exactly the same from person to person. Rather than consciously controlling every aspect of the stride, runners tend to develop a more efficient, self-optimizing movement pattern through consistent practice.
As runners become fitter and more experienced, their movements often become more relaxed and variable. Skilled athletes do not need to devote as much conscious attention to controlling their movements, allowing their stride to become freer and more natural. Running more, provided that it is increased gradually and appropriately, can accelerate the development of this relaxed, smooth running style.
Managing Intensity
Running intensity can be monitored using perceived effort, heart rate, and pace. Perceived effort is particularly useful at the beginning of a workout for determining whether the intended intensity is appropriate. As the workout progresses and fatigue increases, pace or heart rate can help maintain the desired intensity while allowing perceived effort to naturally rise.
Polarized training also works best when combined with the hard/easy principle. Hard workouts should not be placed back-to-back. Instead, demanding sessions should be separated by easier recovery or foundation runs. This allows the body to absorb the training stimulus and reduces the risk of excessive fatigue.
Training in Cycles
Running improvement does not come from continuously increasing training stress. The body needs periods of recovery and adaptation. Training should therefore be organized into cycles rather than treated as an endless progression of harder workouts. A training cycle may gradually increase workload over several weeks before reducing the load during the final week to allow recovery and prepare the runner for the next cycle.
This can be accomplished through step cycles, in which each week becomes slightly more demanding than the previous one until the final week, when training load is deliberately reduced. Training should also be progressive overall, with each training block moving the runner closer to peak race readiness.
Run More—but Gradually
One of the most effective ways to improve as a runner is simply to run more. Increasing low-intensity volume provides a large amount of aerobic stimulus without the same level of stress associated with frequent hard workouts. However, increasing running volume too quickly also increases injury risk. The goal is therefore to add volume gradually while allowing the body enough time to adapt.
Cross-training can help overcome the limitations of running volume. Non-impact aerobic activities provide additional cardiovascular training without adding the same repetitive impact forces associated with running. A minimalist approach might add one cross-training session to an existing running schedule, while a more aggressive approach could include multiple cross-training sessions each week. The latter can be particularly useful for for runners who are injury-prone or who need to limit running impact.
Useful forms of cross-training include pool running, bicycling, elliptical training, antigravity treadmill running, slideboarding, and uphill treadmill walking.
Overall Principle
Polarized training is ultimately about finding the right distribution of stress. Most training should be easy enough to support high volume, recovery, aerobic development, fatigue resistance, and improved running economy. A smaller amount of carefully placed moderate- and high-intensity work provides the stimulus necessary to develop speed and race-specific fitness.
The goal is not to follow an exact 80/20 formula. Instead, aim to run predominantly easy, train hard when it matters, separate hard sessions with easy days, increase training gradually, use cycles and recovery periods, and supplement running with cross-training when necessary. By avoiding the trap of running moderately hard all the time, runners can accumulate more useful training while reducing unnecessary fatigue and creating a stronger foundation for long-term performance.
Source: 80/20 Running by Matt Fitzgerald