Standing on the precipice of The Grand Canyon in northern Arizona, gazing out over its vastness, feeling extraordinarily small, leaves you awestruck–let alone if you’re about to test yourself by running from one rim, to the other, and back again.

Rim-to-rim-to-rim, also known as R2R2R or R3, is one of Fastest Known Time’s top 10 premier routes in the world, meaning that it’s extremely popular, highly competitive, and has more strict guidelines for fastest known time (FKT) submissions. Athletes like Jim Walmsley, Taylor Nowlin, Lars Arneson, and Addie Bracy have each put down a speedy effort on this iconic 44-mile route. 
R2R2R is an out-and-back route, packing a serious vert punch with 10,500+ feet (or more depending on whose Strava file you’re looking at) of ascent and descent. After the initial 6.6-mile, quad-busting 4,883 foot descent into the canyon from Yaki Point via the South Kaibab Trail, the route gradually climbs up from the Colorado River to the North Rim via North Kaibab Trail (14.7 miles with 6,384 ft of ascent/descent) and returns back to the South Rim in the same manner.

Looking at the two trails on a map, their steep grades might initially convince you that you’ll spend the entire day power-hiking, but in reality, the downhills and segment of trail between the two main climbs, also referred to as “The Box”, are opportunities to open up the stride! In the words of mountain runner, elite OCR athlete, and endurance coach, Josh Ried, “it’s the perfect place for a mountain runner with some road speed or a road runner with some mountain legs.”

On top of the demanding terrain, R2R2R, like any ultra, is the ultimate test of logistics and planning. The canyon’s extreme temperature swings, limited resources, and seasonal changes require runners to be prepared–winging it just won’t cut it! 

So how should a trail runner best prepare and train for a successful R2R2R attempt? How does that change when pursuing a personal record or FKT? From training volume and intensity to fueling and hydration, we’ll cover the most important aspects of preparing for a big day running across one of the world’s natural wonders…twice.

Volume: How Much to Train?

Most endurance athletes understand the mentality that more is better…to a point. Training volume is one of the most important aspects of endurance performance. 

That being said, every athlete has a personal threshold for training volume that varies based on athletic history, surrounding life circumstances, injury history, and recoverability. Since R2R2R demands runners to be fit and prepared to handle hours of moving over demanding terrain, it’s worth maintaining a minimum training volume.

Generally, for ultramarathons of the 50K to 50-mile distance, accomplishing 6 hours of running per week for 3 weeks, starting 6 weeks prior to the goal event is the minimum recommended training volume.

If possible, most of the running volume should be done on trail, but if the road or treadmill are the only options readily available, 1-2 weekly trail runs for the last 4-6 weeks prior to R2R2R is likely sufficient to build trail skill and test gear. 

When training for any endurance goal, identifying training metrics that matter most to the specific goal is the best course of action. For R2R2R, hours and vertical gain and loss are those metrics. Obsessing over weekly mileage numbers can be misleading; placing greater importance on hours and vertical gain and loss is a better approach. Mileage is far less important than hours spent running in the context of trail running because the vertical gain and loss in both a single training bout and also across a week’s time influence the amount of time a runner spends training, and thus, total training stress. 

A well-constructed training program will gradually increase running volume, being careful to avoid stressing the body with too much too soon. It’s always a good idea to plan de-load weeks every so often to allow for recovery. De-load weeks can occur every 3-5 weeks depending on the athlete’s experience and tolerance to the training. A de-load week consists of at least a 30% reduction in total running volume and a proportionate decrease in the time spent at intensity. 

Peak training volume, the most time a runner will spend running in a week, usually occurs 4-5 weeks out from the targeted R2R2R date. A peak week looks different for individuals based on their goals and prior experience. For R2R2R, here are two athlete scenarios:  

Athlete 1: Amanda is newer to trail running (less than 2 years of training) and just completed her first Spartan beast. She found out about R2R2R from a friend who is also newer to trail running. They both want to run R2R2R as a day-long adventure. They plan to keep it casual, run together, take tons of photos, and test their endurance. They currently run around 4 hours per week. 

Athlete 2: Cameron is an experienced trail runner with almost 5 years of experience and many successful obstacle course races under their belt. Cameron wants to push their limits in the canyon, aiming for the best time given their current training volume of 8 hours of running per week. 

For Amanda, logging the same amount of vertical ascent and descent as R2R2R in a 7-day period will likely allow her to achieve her goal. This means that her 1-2 peak week(s) might consist of 44 miles and 10,500 feet of climbing and descent. 

In Cameron’s peak week(s), the same amount of mileage, vertical gain, and loss should be targeted in a 2-day period instead of 7. 

However, all of this isn’t to say that a R2R2R training plan should focus solely on climbing and descending. 

The Box, the section of trail that extends over the Colorado river between South Kaibab and North Kaibab, is surprisingly runnable. After descending South Kaibab and reaching the Black Bridge to cross the river, the grade gently climbs at an average of 3.9% for just over 6 miles prior to climbing up North Kaibab. 

After descending North Kaibab, if the quads aren’t too smashed, the slight 3.9% downhill grade in The Box is the perfect opportunity to let the legs turnover and shed some time. With these mellow grades and non-technical segments, efficiency and speed are an asset. In fact, Lars Arneson, the men’s unsupported R2R2R FKT holder, said that if he was to go back and train for the route again, he would have added speedwork to the end of his long runs and incorporated more hilly road running. “Being able to open it up on the downhill without taking a ton of damage to the quads would have made a huge difference on the final climb,” he reflects. 

Addie Bracy, the women’s unsupported FKT holder and Nike Trail athlete, emphasized the importance of being well-rounded in one’s running fitness when tackling R2R2R. For her, “It was helpful to feel fit and strong in a variety of areas because the R2R2R has it all. There’s steep downhills, there are long rolling runnable sections, and there are long, steep climbs.”

Above: Lars Arneson currently holds the men’s unsupported R2R2R FKT. He ran the route in 6 hours, 38 minutes, and 42 seconds. Arneson roughly lopped 15 minutes off of Dakota Jones’ 2011 record.

Intensity: How Hard to Train?

One of the common misconceptions about ultrarunning is that all of the training should be slow and easy because that’s a “race-specific intensity”. However, even ultrarunners need intensity! 

Easy running volume certainly has its place in a R2R2R training plan. But so do workouts that push and stress our endurance and strength. Lactate threshold workouts, downhill skill sessions, and long runs are like puzzle pieces that, when placed correctly, can make the whole picture of R2R2R come together seamlessly. 

Above: to prepare for the steep grades like this that you’ll encounter in the Grand Canyon, consider using an uphill treadmill for some of your lactate threshold workouts. Photo credit: DJ Fox.

Lactate Threshold: the lactate threshold is the point during exercise where lactate (the byproduct of anaerobic glucose metabolism) begins to accumulate in the muscles faster than it is cleared. As lactate accumulates in muscle, so do hydrogen ions. It is a myth that lactic acid causes muscle fatigue. In reality, the hydrogen ions lower the pH and interfere with muscle function.

Simply put, the higher our lactate threshold is, the longer we can work at a high intensity before needing to slow down. In the context of R2R2R, a high lactate threshold would allow a runner to move faster on the flats and ascents without paying dearly for it later. 

Workouts to improve lactate threshold:

• Tempo Runs: workouts that usually consist of 20-60 minutes of intensity right below or at lactate threshold. Rate of perceived effort (RPE) should stay in the 6-7 range. Tempo runs can be one solid block of effort or broken down into segments, but generally, they are longer in duration than intervals.
  • Example:  65-minute run with 20 minutes easy to warm up followed by a 30 minute tempo and 15 minute cooldown.
• Intervals: shorter bouts of intensity followed by a recovery period. Lactate threshold intervals usually consist of a 4:1 work to rest ratio. Intervals are designed to allow runners to work at or above lactate threshold for a short period of time without flooding their muscles with hydrogen ions and compromising recovery.
  • Example: 60-minute run with 20 minutes easy to warm up followed by 5 x 6 minutes with 3 minutes moving recovery between reps. 10 minute cooldown.

Both tempo runs and intervals stimulate neuromuscular, metabolic, and cardiovascular adaptations that help you to hold faster paces for longer.

How often to train lactate threshold? 

Tempo runs are generally a bit less stressful on the body than intervals, making them a nice entry point for intensity. Although intervals are shorter than tempos, it can be tempting to run intervals faster and go a bit too hard. Most runners shouldn’t exceed 2-3 lactate threshold workouts per week.

At least one session should be run on an incline to prepare for those serious canyon grades. 

Downhill Skill Sessions: while uphill running is a matter of engine, downhill running is a game of durability and skill, and like any skill, it requires practice! R2R2R is a unique route because of its initial steep descent on South Kaibab. Usually, trail runners are tackling routes that make them climb prior to descending. But the canyon is essentially an upside down mountain, so running downhill while fresh can get you in trouble if you haven’t conditioned your body to the demands of running downhill and then uphill on compromised legs.

Above: South Kaibab trail is riddled with sections of built-in steps that can challenge your ability to run smoothly downhill. 

Workouts to improve downhill running technique and durability:

• Dowhill pickups: these are short bursts of speed that expose runners to intense downhill running in small doses–similar to flat strides. Downhill pickups are perfect for beginners and can be a perfect entry point for downhill skill.
  • Example: 1-2-hour easy run with 6x30s downhill pickups on trail with 90 seconds  of easy running between each pickup. 

• Trail Fartlek: “fartlek” is Swedish for “speed play” and is one of the most versatile workouts for trail because it allows you to run with the terrain, picking up the pace as it calls to you. In a fartlek, you can alternate between easy, moderate, and fast running for periods of time. Similar to intervals, a fartlek is intended to have you work a pinch above lactate threshold intensity for short bouts. However, a fartlek allows for more flexibility with work and rest ratios. Fartleks are both beginner friendly and also beneficial to more advanced runners.
  • Example: 90-minute trail run on rolling terrain with 20 minutes easy running to warm up. Then, begin a 30-minute fartlek alternating between easy running on the ascents, moderate on the flats, and moderate to hard on the descents. Finish with 40 minutes of easy running.

• Compromised Tempo Run: After completing a long climb and descent, you can take to the flats and test your ability to run fast on tired legs. While it might not be a beginner-friendly workout, this is an ideal session for experienced athletes seeking to run their best time for R2R2R.
  • Example: 90-minute trail run on steep and/or technical terrain with at least one long climb and descent followed by a 20-30 minute tempo on flat trail or road. 

• Gym-Based Downhill Simulations: if you do not have access to downhill trails there are some non-running gym workouts that can help prepare the legs for all that downhill impact but they’re still a distant second to downhill running and should take a backseat to actual downhill exposure. Weighted movements such as squats and lunges along with unweighted movements such as box jumps, depth jumps, and split squat jumps can all improve the durability (and strength, of course) in the legs making the canyon vert, both up and down, a bit more manageable.  

How often should you practice downhill running? 

Since downhill skill sessions can present a high risk for injury, they should be done sparingly in training–potentially once every 7-10 days. 

The Long Run: often one of the most glorified aspects of ultrarunning and trail running in general, the long run is a vital component to a successful R2R2R, but it shouldn’t be overemphasized in the larger context of a training plan. Depending on the athlete, terrain, and effort, weekly long runs that extend beyond 3-4 hours can compromise recovery and present greater injury risk.

Runners who want to get the most out of their training for R2R2R might consider implementing regular 2-2.5 hour trail runs and gradually working up to one or two trail runs of 3-4 hours in duration. 

Although not every long run must address all features listed below, consider trying to address each feature at least once during a R2R2R training block.

Important Features of the Long Run:

• Demanding enough to build mental fortitude and strategies for pacing
• Familiarizes you with the sensation of running on tired legs 
• Long enough to test nutrition and hydration strategy under fatigue
• Occurs on specific enough terrain and under similar environmental conditions that allows you to test footwear, clothing, packs/belts, etc.

The final two features are the most important for an endeavor like R2R2R because of the limited resources beyond Phantom Ranch. Once you have dipped below the South Rim and crossed the river, you are committed to a big day. A proper (and well-tested) fueling and hydration strategy can be the difference between a fun, challenging adventure and a sloggy death march.

Above: To demonstrate the canyon’s temperature extremes, these two photos were taken on the same day in early April. Frigid snow and wind at the top of the South Rim followed by sunshine and cactus blossoms after crossing the Colorado River.

R2R2R Fueling & Hydration

As runners in the modern era, it’s widely thought that we’re living in the midst of a fueling revolution. While professional cycling is likely to thank for this advancement in running, most trail runners aren’t used to smashing 90+ grams of carbohydrate each hour. 

Yet when it comes to tackling a monster route like R2R2R, it might just be the perfect opportunity to try your hand at leveling up in the fueling department–particularly if your goal extends beyond route completion and aims at a faster performance.

When it comes to creating a nutrition and hydration plan for R2R2R, it’s best to start with estimating your completion time. 

• On average, runners require 12-16 hours to complete R2R2R. 
• Elite runners finish between 8 and 10 hours–unless they’re Jim Walmsley who ran it in less than 6 hours. 

Environmental factors like heat can play a role in how long the route will take, so it is wise to bring more nutrition and hydration than you anticipate needing.

Above: Josh Ried refills one of his soft flasks at Manzanita rest station–right before the climb up North Kaibab starts to get really steep. Photo credit: DJ Fox

Nutrition Specifics: 

For R2R2R, consuming at least 250 calories per hour is a must (roughly 60g of carbohydrate per hour). Runners who will be pushing their limits will require more calories per hour and a greater proportion of which will come from carbohydrates (versus fat and protein) than those who are casually running R2R2R. From a calorie perspective, this can look like 400 calories per hour–or 100+ grams of carbs! Keep in mind that athletes consuming these sky-high carbohydrate numbers are spending plenty of time training their guts to be able to tolerate it! The average ultrarunner, on the other hand, requires between 50 and 75g of carbohydrate per hour. If you find yourself struggling to recover from long runs, you might be on the higher end of the carbohydrate needs, so don’t be afraid to fuel! 

While protein isn’t a primary fuel source for exercise and carbohydrates should be the main priority, a small amount of protein can be helpful for circumventing some muscle damage and perhaps even central nervous system fatigue that occurs in long bouts of exercise. If protein is tolerated by your gut during exercise, the general recommendation is for runners to ingest 0.25 grams of protein per kilogram of bodyweight per hour. 

If you’re considering fueling with real food in place of or in addition to gels and drink mixes, keep the environmental conditions in mind. Grand Canyon temperatures can range from 44 to 70 degrees in spring and fall– the two most popular seasons for running R2R2R. Choose foods that will be both palatable and edible in a wide range of temperatures. Texture is also a factor–is it easy to chew and swallow regardless of temperature and running intensity? Does it require water to wash it down or is it easy to take in without water?

Above: a sample of Lars’ nutrition strategy for his FKT

Lars ran into this kind of nutrition conundrum during his FKT. Prior to going to the Grand Canyon, Lars had done a lot of his training in the mountains, off-trail and at low intensity, fueling with Clif bars. When he decided to attempt R2R2R, his nutrition plan that worked well in training didn’t translate perfectly. “I remember running up to the North Rim and checking what I had left for food only to realize that it was mostly bars and that I had no appetite nor enough water to eat them,” he reflects. 

With all of the awesome sports nutrition options on the market now, there’s bound to be something to satisfy every runner’s palate. Thefeed.com is a great place to trial out single serving products and find what works for you.  

Hydration Needs:

Hydration is even more important than nutrition for R2R2R. Coming back from bonking is one thing, but trying to dig oneself out of a dehydration hole can be nearly impossible–if not downright dangerous. 

For ultramarathons, 450-750 milliliters of fluid each hour with 500-700 milligrams of sodium per liter is the general guidance to prevent dangerous dehydration and hyponatremia. These large ranges exist because of individual variation and environmental conditions, so at first glance, they may not seem incredibly helpful. 

To get a better idea of one’s personalized hydration needs, it can be useful to perform a fluid loss estimation. Once runners have an idea of how much fluid they lose under certain conditions and intensities, they can use the information to modify hydration goals for R2R2R. 

How to estimate fluid loss:

1. Pre-exercise weigh-in: use a reliable body weight scale and weigh in with minimal clothing 
2. Run and monitor food and fluid intake: during the run, keep track of any fluids, electrolyte powders, or nutrition consumed during. *If you use the restroom during the test you should also consider that in the weight loss.
3. Post-exercise weight: weigh in on the same scale in the same amount of clothing as the pre-run weigh in
4. Calculate fluid loss: convert the pounds lost to ounces (1 lb=16 oz).  
5. Estimate hourly loss: divide total fluid loss by the duration of the run in hours. This is the rough estimation of how much fluid should be taken in each hour during exercise. 
6. Consider metabolic needs: not all of the fluid lost during exercise is due to sweat. Roughly 20-30% of fluid loss is the result of metabolic processes. 

If you constantly struggle with GI distress during longer runs and races, it might be useful to get a sweat test to identify your sweat sodium concentrations. On the two ends of the spectrum, salty sweaters might be unaware of how much salt they actually need, whereas less salty sweaters may be consuming too much salt.

Similar to nutrition, hydration might require some trial and error in training. Some runners may thrive on salt tabs while others find them to be gut bombs that cause over-drinking. Finding what works might take a few repetitions, so practicing your hydration strategy multiple times before attempting R2R2R is likely to lead to a more positive experience in the canyon.

Above: DJ Fox descends North Kaibab trail. With over 10,000 feet of climbing and descending on the R2R2R route, the body takes a considerable beating. Strength is an asset in the canyon. Photo credit Josh Ried.

Resistance Training: Building Canyon-Worthy Legs & Core

Resistance training (AKA lifting weights) for runners is riding a wave of rightfully earned popularity, and those training to run R2R2R are well-advised to hop on the bandwagon.

Resistance exercise not only helps to prevent injuries, but it also improves running economy–the term for a runner’s efficiency at using oxygen and energy for a given speed.  

Women’s supported R2R2R FKT holder and Adidas Terrex athlete, Taylor Nowlin, acknowledged the important role that her consistent lifting routine played in her overall readiness for the route. When done in conjunction with long climbs, descents, and speedwork, a well-constructed lifting program can make a runner’s R2R2R experience much more enjoyable–particularly when it comes to the final climb out on South Kaibab.

World’s Toughest Mudder 2022 Champion and endurance coach, DJ Fox recently completed R2R2R with Josh Ried as a training run, and even he can attest to how tough the final climb up to the South Rim is.

“You don’t realize how steep it is while you’re bombing your way to the bottom on fresh legs. Then 30 miles later when it’s time to climb out, you have a nearly 5,000-foot wall in front of you. What a way to finish,” DJ reminisces.  

Resistance training for R2R2R should focus on building a strong core, hips, and legs. Heavy squats or lunges, single leg deadlifts, and step ups are a few potential starting points. For core workouts, mix it up between stabilizing movements like planks and hollow holds and those that work the core’s ability to produce force–such as weighted trunk rotations or low-to-high cable chops.

Although resistance training is not an absolute requirement for success, it is an aspect of R2R2R training that will support your ability to keep moving efficiently in the late stages of fatigue that are bound to happen on an adventure in the Grand Canyon.

Training for R2R2R In a Nutshell

• Identify your goals–are you looking to finish the route and have a 12-16 hour adventure or are you pushing the pace hoping to set a personal record or FKT? Your goals inform your training.
• Run enough volume to prepare your body for the demands of the route, but don’t over do it. Take rest days and down weeks to recover from the stress of training. 
• Vary your training paces and efforts. Use long runs, tempos, intervals, and downhill skill work to bring all of the fitness components together.
• Practice several times with your gear, hydration, and nutrition you plan to use for R2R2R
• Prepare to bring enough fuel and hydration for your estimated finish time and then a little extra
• Build a strong core and hips to prepare yourself for the impact of the steep grades 
• Research and understand the logistical challenges of the canyon (water pump status, trail closures, mule trains, weather variation, etc.) before you go

For additional resources and helpful information on R2R2R, check out the Grand Canyon Rim to Rim to Rim (R2R2R) Facebook Group, the Grand Canyon National Park “Plan Your Visit” Webpage, and Trail Run Project’s R2R2R Route. 

What is your R2R2R goal? Share it with us in a reply below!