Your VO2 Max Drops Faster Than It Improves. Here’s the Easiest Way to Maintain It.
Fitness doesn’t stick with you forever, nor does it magically disappear all at once. But your absolute top gear is usually the first thing to go when your training stalls.
Coming back after a two-week running hiatus following a race, your easy runs will still feel normal. You can still cover miles and settle into comfortable training paces with relative ease. But when you try to surge up a hill or hit a fast interval pace, power may feel like it costs more energy than you’re used to spending.
This noticeable increase in effort could result from your VO2 max—how much oxygen your body can use during hard exercise—taking a slight dip.
VO2 max is integral to running performance because it helps hard efforts feel easier. But it turns out, it takes much longer to improve VO2 max than it does to lose it. Ahead, experts explain why this happens, and how to maintain the fitness that helps you run faster for longer.
Why VO2 Max Drops Faster Than It Improves
Boosting VO2 max requires consistent training over time—months of time. Losing some of that capacity can happen much quicker.
“Early on, you can see about a 5-ish percent drop [in VO2 max] within a couple weeks [after you stop training],” Kevin Sprouse, DO, a sports medicine physician, founder of Podium Sports Medicine, and medical advisor for Eternal, previously told Runner’s World.
Now, taking two weeks off won’t erase your fitness completely, which explains why you may feel only a little rusty when you try to hit your fast training paces after time away. Your aerobic system adapts to what you repeatedly ask it to handle, so when the demand drops, your body no longer has the same reason to maintain its highest aerobic capacity, Sprouse says.
On the other hand, the timeline for improving your VO2 max depends largely on where you’re starting from.
Beginners and fully deconditioned runners (months to years off of training) often see changes sooner because they have more room to improve. For example, someone following a couch-to-5K program might see significant improvement in their VO2 max within the first six to 10 weeks of training, Todd Buckingham, PhD, an exercise physiologist at PTSportsPRO in Grand Rapids, Michigan, previously told Runner’s World. Research also shows sedentary adults significantly improved their VO2 max after just eight weeks of aerobic training.
However, runners who already train regularly often need more time to see meaningful change. Sprouse says a typical recreational runner who has been active but wants to get more serious about training probably needs at least three months. For elite or highly trained runners, it may take even longer, if the number moves at all.
Regardless of where you are, spending two months to see a VO2 max boost is a long time compared to the two to three weeks it takes to lose it.
What Happens When Your VO2 Max Drops
A slightly lower VO2 max doesn’t mean you’re suddenly unable to run. It just means your upper-end aerobic capacity isn’t as high as it was when you were training consistently—which is why the first noticeable changes may come during high-intensity efforts.
“I think most runners have experienced taking a couple weeks off, and you’re still pretty fit,” Sprouse says. “Sometimes you feel really fresh, but the top end just isn’t there. You could still perform really well in a longer distance event [if your VO2 max falls], but you might struggle to run a mile at your top gear.”
It also matters what your time off looks like. Stopping structured training is different from being completely sedentary. Daily movement—like yard work or walking the dog—can help maintain some baseline fitness, Sprouse explains. But it doesn’t replace running, especially the workouts that maintain your aerobic peak.
The Easiest Way to Maintain VO2 Max
Avoiding a VO2 max decline doesn’t mean cramming in a bunch of high-intensity workouts as soon as you see a slight dip in your reading. The best way to maintain your VO2 max is simply to keep running, avoiding long gaps in exercise and erratic training.
“Performance is the result of what you put into the training,” Janet Hamilton, an exercise physiologist and Georgia-based run coach, and founder of Running Strong, previously told Runner’s World.
You may think you’ve trained consistently only to look back and realize you missed more than just a few key workouts or let several low-volume weeks stack up.
Fortunately, the solution is simple: Keep up a regular schedule.
During race training, that means skipping as few workouts as possible. While you don’t need to stay in peak race shape year-round, you do need enough consistent running to give your systems a reason to hold onto the fitness you’ve built.
Buckingham says slower, zone 2 running helps support capillary and mitochondrial development, while Sprouse says some higher-intensity work is still needed to stress those systems and keep them functioning near their highest capacity.
Our maintenance plans call for four days of running per week in the offseason to maintain your fitness. Of those four days, three are easy, zone 2 efforts to support aerobic adaptations, and one is a harder workout just to have you touch on higher intensities.
Matt Rudisill is an Associate Service Editor who has been with Runner's World since 2025. A Nittany Lion through-and-through, Matt graduated from Penn State in 2022 with a degree in journalism and worked in communications for the university's athletic department for three years as the main contact and photographer for its nationally-ranked cross country and track & field teams. Matt was also heavily involved in communications efforts for Penn State football, men's basketball, and women's gymnastics. In his role with Runner's World, Matt has interviewed Olympians, world champions, and countless experts in the field to create service content that helps runners of all ages and experience levels train smarter and race faster. When he’s not out jogging, Matt can be found tweeting bad takes about the Phillies or watching movies.