While high-intensity interval sessions get all the attention, there are certain powerful physiological adaptations that only result from long, slow rides.
It’s tempting to want to ride hard all the time. Fast group rides are fun; and it takes only a few high-intensity interval sessions to see significant gains. So it’s understandable to want to abstain from doing any more long, slow rides—especially if the weather is cold and gray.
But if all you ever do are intervals, your progress will plateau before you reach your full potential. That’s because certain key physiological and metabolic adaptations can only be developed by consistently riding slow for prolonged periods of time.
Endurance base rides are not filler. They’re not an old-fashioned remnant of the Merckx era. They are the building blocks that form the foundation, or base, of the fitness pyramid.
“These rides change our physiology and metabolism to meet the demands of the sport of cycling,” says physiologist Ryan Kohler of Rocky Mountain Devo coaching, and the former director of the University of Colorado Sports Medicine and Performance Center. “They have the ability to transform a person of general ability into someone who can compete in this endurance sport.”
The science: fueling the engine
The primary focus of base training is to improve our ability to perform for long periods of time at a steady, moderate pace. To do this, we must build our oxygen-consuming slow-twitch muscle fibers—our aerobic engine—which use fat as their primary fuel source.
To do that, we must isolate those slow-twitch fibers for long periods of time. And that’s where the long, slow rides come in. This improves the body’s ability to use fat as energy during steady efforts, which has several benefits.
Even the skinniest cyclist has a nearly endless supply of fat to use as fuel at the cellular level. Thus, by relying on fat as fuel, we delay the use of carbohydrate stores, which are more limited, for when we need them most—during attacks, sprints, and other high-intensity efforts when we utilize our fast-twitch fibers.
Another adaptation that takes place during long rides: an improved ability to use lactate as fuel. For a time, lactate had a poor reputation among endurance athletes, but it is actually a powerful fuel source. In fact, in research conducted by Dr. Iñigo San Millán, the head of performance at the UAE-Team Emirates WorldTour team, an athlete’s ability to maintain blood lactate levels is one of the best measures of performance.
Interestingly, fast-twitch fibers produce a ton of lactate; slow-twitch fibers use it for fuel. In highly trained athletes, the research indicates there are high levels of both a protein that pumps lactate out of fast-twitch fibers, and a second related molecule that allows slow-twitch fibers to absorb lactate.
Two hours isn’t enough to be considered a “long” ride, especially for athletes who ride regularly. Research suggests that at least three hours are necessary to produce cellular changes.
And guess what improves our ability to “shuttle” lactate from one cell type to the other? That’s right—long, slow rides. It’s not until athletes fatigue slow-twitch fibers during long rides, according to San Millán, that we see these big improvements in lactate shuttling capacity.
Finally, other research suggests that the fatigue produced during long rides forces certain fast-twitch fibers to work differently—that is, it forces fast-twitch fibers to work aerobically once our slow-twitch fibers wear out.
This forced aerobic work builds a resistance to fatigue in the fast-twitch fibers. This improves our ability to repeat intense efforts. And, again, it’s only because of the prolonged moderate-intensity exercise that we see these molecular changes.
The perfect base ride
The scientific findings make it clear why base rides are so important. Now we can focus on how to execute these powerful rides—because it isn’t as simple as just riding along for a few hours.
First, two hours isn’t enough to be considered a “long” ride, especially for athletes who ride regularly. Research suggests that at least three hours are necessary to produce the types of cellular changes detailed here.
In terms of intensity, these rides should be done at roughly 60-75 percent of maximum heart rate. If you want to get a more accurate understanding of the pace or zone, you’ll want to perform a physiological test in a lab or a virtual test. In any case, the first couple hours should feel conversational, but after that they will become increasingly fatiguing. That’s when glycogen stores will be depleted and your fibers will begin to use fat for fuel.
While high-intensity intervals produce gains in a matter of weeks, the adaptations from long, slow rides can take years to fully develop. Therefore, it’s best to do base rides regularly, throughout the year, more often during base training and every 7-10 days through other phases of the season.
To maximize gains, consider doing an “overload block” involving consecutive days of long, slow riding.
“Try a three or four-day block, staying in zone 2, at least two to three hours at a time,” Kohler says. “That will give you the consistency and frequency to get a good aerobic overload.”