Why and how low-intensity training works for runners

By Henry Howard

Run slow to run fast.

It’s a concept that can sound odd to some newer runners. But in recent years there has been growing understanding and research that supports the approach that an 80/20 mix — 80% of weekly training at low intensity, 20% at high intensity — is the proper balance.

There are various scientific studies that support this approach. In 2000, “Nature” published a large-scale study that involved collecting data from devices worn by more than 14,000 runners for a combined 1.6 million sessions. The study compared VO2max between runners.

V̇O2 max is the maximum rate of oxygen consumption measured during incremental exercise. It’s a way to measure the potential top speed of runners.

The data analysis showed faster runners, based on race times, trained at a significantly lower average intensity than slower runners. Specifically, runners whose VO2max pace was around 5:20 per mile performed their easy runs at about the same pace as runners whose VO2max pace was around 6:40 per mile.

Other studies have applied more of a cause and effect, rather than analyzing data to formulate a conclusion.

Another recent study took 30 experienced recreational runners and used their performance times in a 10K time trial before and after training. The goal was to compare the improvements in the groups based on their training.

Runners were assigned into one of two training groups. Half of the participants were in the high intensity group, performing 50% of their training at low intensity, 25% at moderate intensity (tempo) and 25% at high intensity (hills, strides or intervals). The second group, the low intensity group, did 80% of training at low intensity, none at moderate and 20% at high intensity. All runners did the same total mileage, between 50K and 65K weekly, and trained for a total of 10 weeks.

After the training, the runners performed a 10K time trial and the data was compared with their first one. On average, the low-intensity group improved their 10K time trial by 41 seconds more than those in the high-intensity group.

Here are some common questions and answers to low-intensity training, or easy running:

Question: What is considered low-intensity training?

Answer: I advise my athletes to run the majority of their runs at a conversational pace. If you can speak a few sentences clearly without any labored breathing or pausing, you are doing it right.

Question: When should I do low-intensity training?

Answer: There are a lot of variables to consider here such as the athlete’s fitness level, injury history, age and goals. But let’s say an athlete is doing four or five runs a week. Two of those runs should be overall harder efforts. For example, a weekend long run with some sort of speedwork and a midweek track session or hill workout. The other runs during the week should be either 100% easy/low intensity or have minimal hard efforts as part of an overall easy run. This could be a 5-mile run with fartleks, hill repeats or some other activity that generates quick leg turnover in short bursts.

Question: I want to get faster. Shouldn’t I be running fast?

Answer: Yes, with a structured approach. But too much hard training leads to injury, compromised recovery and elevated stress levels, especially for masters athletes. We’re not in high school any more when we could recover from six days of consecutive hard workouts. As we age our bodies need more time to recover. For endurance athletes, these low-intensity workouts help build volume, promote recovery and build speed over time in combination with the higher intensity activities.

Question: Shouldn’t this approach vary based on the athlete’s goal race?

Answer: Absolutely. That’s where a good coach comes in and adapts the concept to variables including your fitness level, running goals, age, the course and other factors. While the majority of running will be easy, a good coach will strategically use the weekend long run and short, hard intervals during the week to prepare the athlete for the race specifics, based on his or her own individual’s age, fitness level and more.

Question: Is it possible to go too slow?

Answer: Theoretically, yes. But almost all athletes, especially recreational athletes and age-groupers, generally do their easy runs at too hard a pace. (I’m likely guilty of this at least some of the time, to be honest.) Don’t worry about going too slow in your training. Instead, focus on running easy — conversational pace — for the majority of your running time in order to get the most benefit. When it comes to doing your intervals or other speed work, that’s the time to let it loose.

Note: I earned my coaching certificate from the Road Runners Club of America and now coach runners of all skill levels. My athletes have qualified for the Boston Marathon, run their first marathons and ultras, set PRs and achieved other lofty goals. If you are looking for an experienced coach and runner, I currently have openings available. Contact me here and we can set up a no-obligation phone call to see if we are a good fit.