As a runner, you know those days when you feel like you’re running through sand. You’re well-acquainted with runs that leave you gasping for air, and others that make you call it quits early. But what if I told you that by learning to prime the right energy systems (your body has three, by the way), you could build a running performance that made for “no bad days?” Or okay, okay—fewer bad days.

Like shifting gears in your car, certain workouts will activate certain energy systems in your body. This happens on autopilot because your body’s just that cool, but once you get to know what activities prompt your muscles to tap into different power sources, you can get smart about programming your workouts. To make it easier for you, I have provided a go-to guide on how to structure your weekly workouts, what types of workouts to do, and when to do them based on your trifecta of energy systems.

Your body’s 3 energy systems—and how to tap into each one

1. ATP-PC System (Anaerobic)

Your body enlists the anaerobic system for activities like quick explosive sprints. This system uses a small amount of ATP (adenosine triphosphate, an energy-carrying chemical) which is stored in your muscles, as an immediate energy source.

2. Lactic Acid System (Anaerobic)

The anaerobic system produces energy from muscle glycogen, a form of sugar that’s easily stored by the muscles. This is the burning sensation you feel when you do HIIT training or on tempo runs.

3. Aerobic System (Aerobic)

This system produces ATP and provides the energy that your body releases from burning fat and glucose during low-impact cardiovascular activity. (Think: Walking, casual biking, or swimming.)

To maximize your energy systems, train hard. Recover harder.

Train hard, recover harder. When you work out, you create tiny microtears in your muscle fibers. As soon as you are done working out, and especially when you enter REM sleep at night, your body naturally repairs these muscle fibers, and as a result, builds new, stronger muscle.

It follows that if you don’t give your body the proper time it needs to recover, you won’t be able to preserve the work you’ve put in—which is how you reach peak performance! This is why runners taper before a marathon, and why bodybuilders work different muscle groups on different days. So take those rest days after speed work, hard weight training sessions, or after long endurance runs.

A typical weekly schedule could look like for an endurance athlete

Monday: Hill sprints or regular sprints and core work

If you’ve got access to a treadmill, try this sprinter’s workout

Tuesday: Rest day

Rest days are key. If you want to get stronger you have to take at least one to two rest days every week. On these rest days, low-impact activities like walking, range of motion workouts, and flexibility work are totally fine.

Wednesday: Endurance run (4 to 10-plus miles)

Stop static stretching before you run (I repeat: stop static stretching before you run). Dynamic stretching, utilizing quick, fast-twitch movements like single-leg hops, jump squats, and high knees, before you run, helps to prepare your body for the impact of running more effectively than static stretching.

Static stretching actually elongates your muscles, decreasing your muscle’s overall elasticity (or their ability to contract and fire). Think about muscle elasticity in the impact phase in your stride cycle: When your foot hits the ground, you don’t want your body weight to be absorbed into the ground with a heavy landing. Instead, you want to be able to propel, or “spring,” off of the ground, using your muscle’s elasticity and power.

In order to prepare your bones and joints for this type of impact, it’s important to fire up your glutes, hamstrings, and quads through dynamic movements before you run. In doing so, your body is going to run more efficiently. Once you’re done with your endurance run, you’re ready for that static stretching.

Try this dynamic warm-up before your next run: 

Thursday: Strength training

Repeat after me: Lifting weights does not slow you down. If running is the only movement pattern you utilize in your training, you won’t be able to effectively optimize your stride strength, hip integrity, and overall efficiency, as effectively as you would be able to if you were also incorporating lateral, vertical, and isolated movement patterns with strength training.

Adding weight training to your weekly regimen will not only help to increase your lean muscle mass, but will also help you increase your core strength, reduce fatigue on endurance runs, and improve your overall running economy. Think: Kettlebell flows, bodyweight core movements, and compound movements with dumbbells like deadlifts, thrusters, and squats.

Try my six-minute core workout for a quick take on strength training:

Friday: Active recovery runs (30 to 40 minutes)

If you want to run fast, you have to run slow. Slow, easy runs are called “aerobic” runs, and distance runners should have at least one ranging from 40 to 60 minutes every week. With this type of run, the goal is to keep your pace about 20 to 30 seconds slower than your average pace, and your heart rate under 170 bpm.

Running slow isn’t always “fun,” and at times, you may even feel discouraged you aren’t going “hard” and “getting the most out of your workout,” but running in a low heart rate zone, with a steady effortless “conversation pace,” is imperative for reaching peak performance as an endurance athlete. It primes your aerobic foundation, which is the foundation of all cardiovascular training, and also has other benefits, like lowering your resting heart rate. Look at aerobic running as a means to produce ATP for your body so that you can perform well on your high-intensity days.

Saturday: Rest day

Sunday: Active recovery run (40 to 60 minutes)

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