Threshold Training: Nutrients To Fuel Your Workout

By: Heidi Harris, RD-N, CD-N, LD-N

Before We Begin:

Hello! My name is Heidi. I’m a Registered Dietitian, certified strength training and conditioning coach and certified SpinPower® instructor. Today, I want to talk with you about a common theme in both strength training and endurance exercises like cycling, running and swimming: Threshold Training. We’ll focus on nutrients to help fuel you as an athlete to your next level of optimal performance.‡

What is Threshold Training?

You may have heard of threshold training if you’ve ever researched strategies on preparing for a long-distance run, bike ride or maybe even a 500 meter freestyle swim. Threshold training is all about making small, gradual gains that lead to great outcomes and individualized improvements to help you accomplish your training goals.Threshold training is a type of individualized training program that utilizes five different training zones and a personalized threshold to help athletes yield greater athletic progress and performance without running the risk of over-exercising.1

In simpler terms, a threshold is some form of exercise intensity where your physiology shows a marked change.2 A good way to visualize threshold training is by first imagining you’re running a 5k at your usual jogging pace. You’re running, your breathing is steady and measured, you’re exerting energy and have a steady stream of sweat, but it’s feeling manageable and controlled. Now, imagine you are running that same 5k but this time, at an all-out sprint. Your breathing is heavy, your heart is racing. That stitch in your side kicked in somewhere around the 1.5 mile marker.

The distance didn’t change.

The person running the 5k didn’t change.

You’ve run a 5k before.

You’ve even practiced sprints before.

So… what changed?

This marked physiological change and increased effort output by the athlete is part of the zone training within the exercise methodology: threshold training.1 To make it concise, the level of effort required to run a 5k at an all-out sprint requires a certain level of energy output and a certain amount of power provided by the athlete. Once the athlete can no longer continue at this pace and can no longer maintain this level of effort or energy output, they need to break or back off their pace and decrease their effort output– this is the moment where they’ve reached their personal threshold.3

Once this threshold has been determined, athletes and trainers can work together to create personalized threshold trainings to help improve their effort and overall athletic performance without overdoing it. You’ve probably heard of threshold training before, but maybe in a different way. In running terms, it’s often referred to as your T-pace and in cycling it’s often referred to as PST (or your personal spinning threshold).2,3 Either way, the ability to nutritionally fuel for your threshold training may help optimize your physical performance. ‡

Threshold Training: The Zones

To effectively prepare for threshold training, we need to first understand the different energy zones that occur before, during and after you’ve reached your personal threshold. Threshold training consists of 5 different zones. Zone 1 through the first half of Zone 3 include up to 85% of your maximum heart rate and falls within the aerobic energy zone. This zone utilizes fat for fuel and requires oxygen to generate ATP (adenosine-triphosphate).3

Zone 3 is where your personal threshold lives. This is because there is a change that happens during Zone 3 of training. Each athlete is different (which is why we call it our personal threshold), but in general Zone 3, our bodies transition from oxygen as a component of generating ATP to the anaerobic phase of energy training, or not using oxygen to create the energy currency, ATP. ATP acts as a form of energy currency in the body.4 When this change occurs, your personal threshold has been met.

In the second half of Zone 3 to Zone 4, 105% to 120% of your maximum heart rate, is part of the anaerobic energy zone which means that the body stops using fat for fuel and reliance on oxygen to generate ATP via mitochondrial pathways and transitions to using glycogen, the storage form of glucose, and generates ATP without relying on oxygen.5 There’s more science to that, but for the purpose of focusing on threshold training, we’ll leave it at that. To know when you’ve met the Zone 4 of threshold training, look for signs of sucking down air. Breathing becomes difficult and challenging during this zone. You are sweating and maintaining a pace that you can’t handle for long periods of time.

Zone 5 is reserved for those quick bursts of intense energy output. This zone remains within the anaerobic zone and includes 120% heart rate to your maximum heart rate and the metabolite Creatine within the muscles is the primary resource to generate ATP.3

Threshold Training: Fueling the Aerobic Zones:

Considering Zone 1 through the first half of Zone 3 focuses on the aerobic energy zone using fat for fuel, why don’t we focus on some nutrients to help support us in this aerobic phase of threshold training?5‡

Remember when drinking beet juice was a major craze before a long run or a major endurance exercise program? Okay, I know that’s kind of a throwback and there’s more to the story than just beet juice, but let’s not throw beets entirely out the window. Beetroots are an excellent source of nitrites.

• Our Klean Pre-Workout provides 140mg of TruBeet® — all-natural nitrates derived from beetroot.
• Some studies indicate that athletes who supplemented with beetroot extract increased time to exhaustion during high-intensity interval training which led to improved stamina and endurance and reduced oxygen consumption during submaximal exercise.6,7,8‡
• Nitrate supplementation has been clinically shown to support cardiovascular function, possibly by sparing ATP and enhancing muscle kinetics.7,8‡