Imagine you are completely sedentary and you have been for some time. Then one day you decide to train for a 10K running event. The specific training method you choose is Yoga—30 minutes a day, six days a week. To assess the effectiveness of this program, you actually do a 10K beforeyou start on it and then repeat the race eight weeks later. On this second occasion, you cover the distance more than five minutes faster than you did the first time.

When you tell a runner friend about your success, she says, “Yoga? That’s a terrible way to train for a 10K!”

“Obviously not,” You retort. “Did you miss the part about me lowering my time by more than five minutes?”

As absurd as this hypothetical scenario is (absurd but not unrealistic–a previously sedentary person who did a ton of Yoga would substantially lower his or her 10K time), I see athletes commit the same logical error in slightly less absurd ways all the time. It just doesn’t seem to cross the minds of some athletes that there’s a difference between effective and optimal. I’ll give you three concrete examples of methods that typically yield some improvement for the athletes who adopt them but not as much improvement as they would give from adopting proven best practices.

HIIT-Focused Training

In 2013, fitness writer Christopher Solomon wrote a feature article for Outside on his experience of training for a marathon with the CrossFit Endurance method, which relies heavily on high-intensity interval training. Having run a 3:45 marathon five years before, Solomon set a goal of running 3:20 after 13 weeks of CFE training and wound up completing his target event in 3:39.

“Did CFE deliver?” he wrote. “Yes, mostly.” . . . “Would I use CFE to train for my next race? Yes, mostly.”

When I read this article I felt a powerful urge to contact Solomon and offer to train him for his next marathon with the 80/20 method that I favor. It was obvious to me that Solomon had committed the mistake of conflating effective with optimal method and I was quite certain he could get much better results from adopting the endurance training method that has been proven both in the real world and in controlled scientific studies to yield better results than any alternative: 80/20.

The reason athletes often do improve when they switch from their current training approach (which, for the typical recreational endurance athlete, consists of spending 50 to 60 percent of total training time at low intensity, 40 to 50 percent at moderate intensity, and 0 to 5 percent at high intensity) to a HIIT-focused method is twofold. First, this shift often corrects, at least partially, the common and costly problem of getting stuck in the so-called moderate intensity rut. Second, athletes who are stuck in the moderate-intensity rut typically do little to no training at truly high intensities, which are beneficial and which HIIT-focused training methods require.

But again, just because athletes often improve a bit when they try a HIIT-focused training program doesn’t mean they wouldn’t improve more on an 80/20 program. This was demonstrated in a 2014 study conducted by researchers at Salzburg University, who found that athletes who trained in the moderate-intensity rut for nine weeks saw their performance in a time-to-exhaustion test improve by 6.2 percent, whereas athletes who did HIIT-focused training for an equal period improved by 8.8 percent in the same test, and those who did nine weeks of approximately 80/20 training improved by a whopping 17.4 percent—almost double the amount that the HIIT group did.

Low-Carb Diets

It is my belief, based on my observations, that a majority of endurance athletes who adopt very low-carb diets have a bad experience and soon abandon them. But some report getting good results, and many who do wrongly interpret these results as proof that low-carb diets are best for every endurance athlete, or at least for them individually.

In the typical success case, the athlete who goes low-carb loses a substantial amount of weight and achieves a nominal to modest improvement in performance. These anecdotal reports are backed up by some formal studies, including a 2017 study out of Middle Tennessee State University in which eight middle-aged, recreationally competitive male runners lost an average of 5.5 pounds and lowered their 5K times by an average of 2 percent after three weeks on a low-carb diet.

Why isn’t this proof that low-carb diets are best? Leaving aside the fact that this particular study lacked a control group, a runner who loses 5.5 pounds by any reasonable means should lower his 5K time by substantially more than 2 percent. The fact that these runners did not indicates that some negative effect of the low-carb diet partially counteracted the performance benefit of losing weight. Other research indicates this negative effect is impaired exercise economy.

If a low-carb diet was the only way to lose weight, it might still be the best diet for endurance athletes. But it’s not the only way to lose weight. Athletes can enjoy the advantages of both weight loss and adequate carbohydrate intake simply by reducing their intake of low-quality carbohydrate sources (e.g., refined grains) and other low-quality food types (e.g., foods with added fats) and continuing to eat high-quality carb sources (e.g., starchy vegetables). This high-quality, carbohydrate-centered approach to eating for endurance is what the pros do and is, in fact, the best diet for virtually all endurance athletes.

Meathead-Style Strength Training

Recently I created a custom training plan for a client who had a background in personal training but had recently gotten really into running and wanted me to help him achieve a sub-three-hour marathon. Unsurprisingly, his existing strength-training routine relied heavily on exercises such as bench presses and dumbbell shoulder presses that are counterproductive for runners and was utterly lacking in single-leg exercises, balance work, and exercises targeting small but important stabilizing muscles such as the hip external rotators. When I suggested to my client that he modify his strength workouts to make them better resemble those that elite runners do, he pushed back, saying he had good reason to believe he was benefitting from the workouts he was doing.

Sigh.

Now, I will admit that it’s hard to prove that the strength-training methodology practiced almost universally among elite runners today is optimal and that alternatives such as bodybuilding-style strength-training and CrossFit are suboptimal (it’s very tricky to execute a study that would do the job), but I’m confident these things are true. A runner who replaces bench presses and the like with more functional options will lose excess upper-body muscle mass and thereby lower the energy cost of running at any given pace. And a runner who strengthens important but neglected stabilizing muscles will be rewarded with a boost in running economy and reduced injury risk.

No recreational endurance athlete should feel obligated to do things the most effective way. If you want to do HIIT-focused training because it’s fun or adopt a low-carb diet because it’s trendy or lift weights like a bodybuilder because you like how it makes you like with your shirt off, be my guest. But if you want to realize your full potential as an endurance athlete, understand that there’s a difference between effective and optimal and keep this distinction in mind when making decisions about how to train and eat.