The goal of training is to deposit as much fitness as possible into your training account. Little deposits day after day add up. But once you are comfortable running almost every day and aren’t running little-paycheck-to-little-paycheck, it’s time to add some bigger deposits. It’s time to do long runs.

Long runs are where your most important physiological and psychological adaptations occur. Everything else can be perfect, but if your long runs aren’t appropriate for your race goals, you’ll never get close to your potential. Want to be a big spender on race day? Then you need to deposit some long runs into your account during training.

However, there are no get-rich-quick schemes. You need to put in the time, and plan long runs strategically to avoid compromising consistent training.

RELATED: How to Master the Long Run

Why long runs?

The body is a fickle machine, with lots of moving parts and flowing fluids. Long runs can help make you a well-oiled, finely tuned instrument by improving almost all of the elements that count.

“Long runs serve a multitude of purposes, but the most important and obvious include strengthening your muscles, tendons and ligaments; improving your aerobic endurance and efficiency; and teaching your body to use fat as a fuel source,” says Mario Fraioli, founder of Ekiden Coaching.

In other words, long runs have three main physiological objectives:

Muscular: The unique stress of long efforts is the best stimulus for musculoskeletal adaptations that enhance the resilience you need to be a trail runner.

Aerobic: Long runs help optimize oxygen utilization over time, which is key to developing as a runner. Think of the amount of aerobic stress as a linear graph starting at zero and going up to the right, with time on the x-axis. The longer and harder you go, the more area there is under the curve, and the more your body faces aerobic stress. Too much, and you break down. Too little, and you don’t reach your potential. Long runs are all about finding the sweet spot.

Metabolic: Easy long runs make you better at using fat, which burns low and slow, while adding intensity to long runs improves glycogen utilization and combining energy systems. In a race setting, you’ll almost always be using both energy systems, so long runs improve all aspects of race-day metabolism. Optimizing both systems leads to better, more efficient training and racing.

Most importantly, the unique physical stresses of long runs cannot be simulated through shorter efforts. The aerobic and musculo-skeletal strains caused by a long day on the feet really start to kick in past a certain time or distance threshold, which varies from person to person (keep reading to learn more about this).

Long runs also have a psychological component. “Running long on a regular basis will improve your confidence to cover a given distance or tackle tough terrain late in a run when your legs are smashed,” Fraioli says. Plus, when your training stoke is waning, “A long meandering run on the trails can provide a much-needed break.”

Types of Long Runs

Choosing long runs is a lot like filling up your cup at a self-serve ice cream shop. You can’t really go wrong, but some flavors might be better for your individual background than others.

For most runners, it’s all about that one focused long run, week-in and week-out, most of the year. But, as you get more advanced, you might add occasional back-to-back long runs, or, for elite athletes, even a mid-week long run.

What does “long” mean? It depends on how much you are running to begin with. In general, if you run less than 25 miles per week, it is any run longer than 10 miles; between 25 and 40 miles, any run longer than 12 miles; between 40 and 60 miles, any run longer than 14 miles; and, above 60 miles, it’s any run longer than 16 (scaling up to 18 or 20 for people nearing triple-digit mileage).

“Aim for a gradual increase in both the length and time of your long runs throughout the training cycle to prevent potential setbacks and overuse injuries,” says Tim Tollefson, who finished third at the 2016 Ultra-Trail du Mont-Blanc. “Come race day, your week-in, week-out consistency is what will deliver a strong performance.”

Sometimes, you will go much farther than that minimum threshold. For example, if you are a 40-mile-a-week runner training for a 50K, you may do a few 20-mile runs.

Here are the three basic flavors of the long run:

Long and Easy

The relaxed long run at an aerobic effort is the vanilla or chocolate flavor—tasty, but usually nothing to write a 5-star Yelp review about.

How and When
Do an easy long run every week during the initial base period of training, getting 20 to 40 percent of your weekly mileage from it. As you build toward the racing season, you can begin to push downhills or experiment with faster efforts. Then, when races are eight to 12 weeks away and you are thinking about the specific demands of race day, alternate between easy long runs and harder efforts every week.

Benefits
Easy-effort long runs work all of the key physiological elements. Aerobically, they improve efficiency and oxygen-processing power. The aerobic engine drives all performance, so these adaptations will make you a better runner at all paces and distances.

Metabolically, easy long runs burn fat, improving how well your body can operate without constant calories. This is essential for races lasting more than 90 minutes to two hours, because your body will always burn more calories than you can take in and you’ll need to call on your fat reserves early and often.

In addition, easy long runs improve musculoskeletal resilience while minimizing injury risk. The goal of running training is to bend, but not break, and long and easy is the best way to avoid snapping in half.

RELATED: Aerobic Build Weeks

Downsides
Easy long runs are low risk, medium reward. You are unlikely to get injured, and they build an essential base, but easy long runs alone are unlikely to propel a stunning breakthrough that makes you the next hot thing in trail running.

Bonus Point
I have my athletes run the downhills in long runs with purpose most of the year. While this remains an easy effort cardiovascularly, it teaches your legs to absorb the pounding and lets you exploit the downhills on race day.

You can also do easy long runs without fuel, which flips the switch to fat burning sooner in the run and provides additional metabolic stimulus. Of note, some evidence points to fasted long runs as less advantageous for females.

Workout Long Runs

Workout long runs that include efforts above aerobic threshold (including long runs with intervals) are the double-dark-chocolate-peanut-butter supreme flavor—it might blow your mind, but it also might be too much for some people.

How and When
Do these only in the middle or end of a training cycle, when you have a big base of miles underneath you to prevent injury and make the effort count. Keep your workout long runs to every other week at the most unless directed by a coach, and never closer than two or three weeks before race day.

As you would with a race, recover before and after workout long runs, and don’t schedule them too often. Respect the effort and you will reap the rewards.

Benefits
Whereas easy long runs train you for further training (an important step in developing as a runner), up-tempo long runs train you for racing. The more intense efforts involve your aerobic and lactate thresholds, improving the efficiency of the energy systems you will actually use on race day.

Musculoskeletal stress is increased as well, as your body pushes in new ways that are more similar to race day. And, metabolically, you are entering new territory, where purely aerobic, fat-burning effort transitions into a mixed carbohydrate/fat-fueled effort, which makes you better at turning food into fuel.

Workout long runs are “a great way to combine workouts and gain a huge amount of strength,” says David Laney, the third-place finisher at the 2016 North Face 50-Mile. “Running fast on tired legs is key.”

Downsides
Workout long runs are hard. They require recovery before and after, which cuts into training. Injury risk goes through the roof relative to easy efforts. And both aerobic and metabolic efficiency can suffer if you do too much intense training (akin to spending so much time on the icing that you forget to bake the cake, or let the cake you did bake go stale). Used in moderation, though, workout long runs can unlock performance breakthroughs, so you can have your cake and eat it too.

Bonus Points
You can sprinkle some fast, race-paced intervals into an up-tempo long run to simulate the demands of race day. These can be done on uphills or flats to emphasize aerobic adaptations, or downhills to emphasize musculo-skeletal strength and resilience.

Or, do up-tempo long runs as progressions, starting easy and working up to harder efforts over the course of the run.

RELATED: The Importance Of Eating Enough Food

Back-to-Back Long Runs

Doubling up on long runs on consecutive days is like having ice cream for lunch and dinner—you better really enjoy it, your body better be equipped for it and you shouldn’t do it too often.

How and When
Only do back-to-back long runs if you’re racing longer than three hours, particularly in an ultra. Aim for one to four times in the 10 weeks before a long race, spaced out at least two weeks apart. Some of the top athletes I coach, like 2016 U.S. Trail 50-Mile Champion Corrine Malcolm and 2016 Western States 100-Mile 7th-place finisher Chris Mocko, have excelled after completing back-to-back long runs seven, five and three weeks out from race day.

Go into these runs rested and be sure to recover afterward. Eating becomes a competitive sport when you start training with these methods. If you are maintaining an energy deficit for long, your body will likely rebel.

Benefits
For the aerobic system, you can think of back-to-back long runs as having all the benefits of normal long runs, but multiplied by two—a linear increase.

The metabolic and musculoskeletal adaptations, meanwhile, can be exponential. The first long run creates an energy deficit that your body runs through on the second day, a unique metabolic stress that has the potential to accelerate the adaptations related to how you turn food into fuel.

But most importantly, back-to-back long runs stress every bone, tendon, ligament and muscle in a new and exciting way. If they can bounce back from that unprecedented stress, your body will be better prepared for the demands of a long race.

Malcolm attributes some of her astronomical 2016 success to back-to-backs. “They help to alleviate the quad cramping I was experiencing before I made the step up to the ultra distance this spring,” she says. “Basically, my body wasn’t used to my muscles having to contract over and over again for that long. Back-to-back long runs trained my body to continue to work through that muscular fatigue.”

Downsides
The injury risk also increases exponentially with back-to-back long runs. In addition, you probably won’t be running as efficiently or fast, so they can be detrimental for shorter races.

Bonus Points
The classic back-to-back consists of two easy long runs, but the deluxe involves a hard effort on day one, then an easy long run (possibly with some intervals) on day two. The mix of stresses will provide a massive stimulus for your body. You’ll reap the rewards in a long race—if it’s not too much.

Paraphrasing the Supreme Court’s definition of pornography, it’s hard to say when an athlete is ready for back-to-back long runs, but I know it when I see it. Consult a coach or expert friend if you are in doubt. If you are flying solo, only do back-to-backs when your staple long run starts to feel easy.

Tailor to the Distance

The race is like the big test at the end of the semester, and the long runs are the studying. If your goal is just to pass (complete the race), it means something totally different than if your goal is to ace it (perform up to your potential). What it takes to get a report card you can be proud of depends on the length of your race.

Half-Marathon and Below

To finish: Work up to 10 miles easy, with a few runs of that distance in the final six weeks of training. Once 10 miles becomes mentally doable and you go through the recovery cycle one or two times, you will have the aerobic and musculo-skeletal adaptations you need and the race should be a piece of cake.

To perform: Work up to doing the race distance at least weekly; elite athletes may go up to 20 miles. Starting around 10 weeks from race day, make your long run a workout every other week.

The Workouts:

The Steady Eddy

2 miles easy, 10 miles moderate, 2 miles easy. This workout focuses on aerobic and lactate threshold, improving your endurance.

The Grinder

3 miles easy, 10 x 3 minutes hard/3 minutes at the fastest pace you can hold while still recovering, 3 miles easy. This works lactate threshold and touches your VO2 max, improving the main energy systems you will be using on race day.

The Holy Guacamole

3 miles easy, 2 x 20 minutes hard with 5 minutes easy in between, 4 x 2 minutes close to all-out with 2 minutes easy between, 3 miles easy. This workout is too spicy for most, but will launch your legs to some scintillating adaptations if you are ready for it.

Marathon and 50k

To finish: Work up to a 16-miler, 18-miler and 20-miler at an easy effort sometime in the final seven weeks of training. Trying to do a marathon without at least one 20-miler will buy you a ticket aboard the pain train.

To perform: Work up to consistent 20-milers, so that you have zero fear of the distance, including some easy back-to-backs. In the final six weeks, do two rzzuns between 20 and 25 miles at a moderate effort with intervals. After one or both of these workout long runs, do another long easy run of 16 to 20 miles.

The Workouts:

The Cruisey Suzie

1 mile easy, 16 to 22 miles moderate with downhills at race effort, 1 mile easy. The workout is a butt buster that works aerobic threshold and simulates the demands of long races.

5 x 1 – minute hills, 3 miles at race effort. This run gets your climbing legs in gear and teaches you to run hard on tired legs.

Stairway to Heaven

3 miles easy, 5 x 3 min hills hard (run down moderately for recovery), 3 miles easy, 5 x 2-minute hills, 3 miles easy, 5 x 1-minute hills, 3 miles at race effort. This run gets your climbing legs in gear and teaches you to run hard on tired legs.

The Rollercoaster

20 to 25 miles with a moderate 2 minutes every 5 minutes starting 20 minutes into the run. This workout keeps you engaged and has you running fast over varied terrain.

50 Miles and 100k

To finish: Work up to consistent 20-milers, and be ready to hike on race day. Running these distances requires you to make training a high priority. You can do serious damage to your body in these events if you are under-prepared.

To perform: Work up to consistent 20-milers, including a few back-to-back easy 20-milers. Then, add two to four 40-to-55-mile weekends with workouts three to eight weeks before race day. Only run these distances for peak performance if you are durable and talented at eating. You need to be resilient, a fat-burning machine, an aerobic monster and mentally tough as nails.

The Workouts:

The Smart Bart

50K easy on day one, followed by 16 to 25 miles easy on day two (ideally around four weeks out). This will ensure your body is ready to handle everything race day throws at it.

The Race

Run a 50K race at least four weeks before your goal race. Races work everything, including mental toughness.

The Combo Platter

Do one of the workouts from the marathon or 50K section and add a few extra easy/moderate miles. Or, do the workout as is, then run an easy 16 to 25 miles the following day. This works every energy system and has less injury risk than a race, but more stimulus than two easy runs.

100 Miles

To finish: Work up to two to four 40-to-55-mile weekends, and be ready to suffer. 100 miles is a whole new world of hurt. There is no way to really prepare someone for that other than to say: “Be ready. Be smart. Keep going. But don’t die.”

To perform: Build a base of consistent 20-milers, then do two to three 40-to-65-mile weekends, and at least one extra-long run (preferably as a race) between 35 miles and 100K. Kaci Licktieg, winner of the 2016 Western States 100, raced a 50-miler six weeks before race day, then ran 70-plus miles at the Western States Training Camp the following weekend. “I wanted the bulk of my long runs more than four weeks out so it gave me enough time to adapt and recover,” she says.

The goal: Prepare your metabolic and musculoskeletal systems for all-day efforts, which requires some close-to-all-day efforts in training. The brain needs to be worked most of all, so use the extra-long runs to practice positivity.

The Workouts:

The Sorry Laurie

35 to 40 miles easy, running downhills at a tick above race effort to prepare your body for the pounding of race day. You may be sorry you committed to a 100-miler by the end of this long training run.

The Race

Preferably a 50-miler or 100K, at least six to eight weeks before race day for most athletes. There’s nothing like a dress rehearsal to prepare you for the big dance. You’ll need a week or two to recover, so keep it under control and focus on long-term health during the race (by fueling properly) and after (with a cautious ramp-up to full training).

The Happy Meal

Combine one of the workouts from the 50-miler/100K section with an extra-long run of 20 to 35 miles the next day. It will either build mental and physical resilience, or you’ll go crazy and get hurt. But that’s 100-mile ultrarunning for you.

David Roche partners with runners of all abilities through his coaching service, Some Work, All Play. With Megan Roche, M.D., he hosts the Some Work, All Play podcast on running (and other things), and they wrote a book called The Happy Runner.