XTERRA Couch to Trail – Breaking Down the Build Phase



By 5x XTERRA Age Group World Champ Mimi Stockton

Last month, we discussed the four different phases of periodization training and how each one has their respective place in the overall plan. Now I’m here to delve into the second phase – the build phase.

Did you know that what happens during the build phase has a greater influence on your race performance than any other phase in your training plan? For some, the build phase can be a daunting and uncertain period of training. And while it’s a bit more difficult to describe the details of the build phase than it is the base phase, it’s paramount to understand the nuances of this phase and to get it right.

As we discussed last week, base training is relatively straightforward and has similarities across the board for all athletes regardless of the race distance and sometimes even the sport. There is a lot more wiggle room to play around because the focus is typically about accumulating general fitness– by working on aerobic endurance, building strength and fine-tuning technique.

Building VO2Max

During the build phase however, there is a definite training shift and the workouts become more about prepping your for the race (or races) you’re going to undertake. This phase will prepare your mind and body for the rigors of the more specialized training to come. It requires more focus on specific systems and the types of workouts vary greatly. In this phase the primary objective is to maximize aerobic power and start building the top end. We want to put our energies into increasing muscular and anaerobic endurance.

VO2 max intervals are a staple of this period and it’s important to get the timing of these workouts right. While it takes a long time to build a solid base – there’s almost no such thing as too much base – building top end power only takes a short amount of time and can fizzle out quickly if incorrectly planned. The last thing you want to do is hit your peak top end power 2-3 weeks before your A race. (Remember, you don’t want to be race ready in March if your race is in June!)

Since top end power takes less time to build and takes a greater toll on the body in terms of effort and fatigue, the build phase is typically much shorter than the base phase. Easy, right? Not so fast! In order to be effective during this phase, to push your body to the max, you must have spent some quality time constructing a solid base, otherwise you will not be able to withstand the higher loads and efforts of the build phase.

Go Hard When It Counts

So what does the build phase look like? Well, for starters, you never want to jump from easy aerobic workouts into all out interval smash festivals. By the time you are ready to enter the build phase, you should already have begun to incorporate some elements of build training into the last couple weeks of your base training phase. For example, during a bike workout, mixing in short 30 second to one minute anaerobic efforts to the end of each long interval will help prep the body for the harder efforts required during the build phase.

It’s important to recognize that the build phase doesn’t mark a radical change in the types of workouts you do but rather a gradual addition of top end efforts and workouts. You should still be doing endurance and aerobic efforts and workouts during this phase to maintain the base you’ve already built. Long Saturday off-road rides coupled with a threshold bike workout during the week are sufficient for this purpose.

Also, a very common mistake many athletes (especially beginners) make during the build phase is to make the “easy” sessions moderately hard (Zone 3), thinking this will improve their overall fitness. The mindset is “if I go easy, I’m not doing anything beneficial.” It’s the same mindset we find during the base phase. But this thinking needs to change. What happens when the “easy” workouts turn into moderately hard or even hard efforts is the next day when you actually do have a hard threshold workout scheduled, your body will not be prepared to do it.

Your body then gets stuck doing all the workouts in Zone 3–the “grey zone,” and no progress is ever made. The potential for fitness gains are made after the hard workouts, when you’re resting and recovering from the hard threshold and anaerobic sessions. So the harder the hard workouts, the easier the easy ones must be, otherwise everything becomes grey and progress ceases. Keep reminding yourself that you shouldn’t make every single session hard with a high intensity, otherwise you’ll be permanently exhausted and will probably end up either injured or burned out. When you’re between key workouts, you either need to allow recovery or do a low-intensity (Zone 1-2) workout.

How to Eat in Build Phase

One area of training that commonly gets overlooked is nutrition. Nutrition is always important and is considered the 4th discipline of racing. As an athlete, you are constantly pushing your body and expecting it to perform. You cannot expect it to do that without the proper fuel. Think of food as fuel to keep that engine humming and your muscles firing. Your body might readily welcome cupcakes and potato chips after a tough workout, but it will certainly perform better the next day if it has avocados and salmon instead.

The energy demands on your high volume or high intensity days will be higher than on your recovery days. This means you likely shouldn’t eat the same IHOP pancake breakfast on your day off that you do after a hard bike session that includes high intensity hill repeats. Just like we periodize our training, you should periodize your daily eating for optimal fueling habits. Also, during the build phase is when you want to experiment with race day nutrition. Too many athletes leave this until the last minute, making poor decisions based on little experience, and DNF because they got their nutrition wrong. Don’t be that athlete! Practice taking in different nutrition options during a hard interval bike workout or a hill run. And do it often! Practice makes perfect.

Where the Fun Begins

For many athletes, the build phase is when the fun begins! It is the period where you ratchet up the volume and/or intensity of your training and truly see what your body can handle. Strength training is still important during this phase, but should supplement the workouts, not replace them.

The build phase leads up to the peak phase, which we will cover in the next Couch to Trail installment. Upon entering the peak phase, you should be in race shape and be able to complete the distances of your XTERRA race. The peak phase is about maintaining this level of fitness while keeping your body fully energized for race day.


The XTERRA Couch to XTERRA training series is presented by SheriAnne Little and five-time XTERRA age group world champion Mimi Stockton of Next Level Endurance. Their new 12-week “Couch-to-XTERRA” training program is designed to do just that, get aspiring athletes off the couch, into training, and to the start line of an XTERRA. Check out their upcoming training camp in Scottsdale, Arizona set for April 26-29 at https://nextlevelendurance.net/camps or email them at info@nextlevelendurance.net.