Improving your VO2max or increasing your threshold is a time consuming process that we talk about all the time.  Not this time.  In this article we share 3 training tips that will increase your triathlon performance in a time efficient manner.

two athletes that are running in a triathlon race

Are you looking to increase your triathlon performance? Or maybe even preparing yourself for IRONMAN Kona? You might want to check out our webinar – Uncommon Strategies to Increase Triathlon Performance. It’s a great opportunity to learn from Sebastian Weber – Project Leader of INSCYD and take your training to the next level. Don’t miss out!

First: swim economy.  Because you can improve it while you’re doing your regular training.

Second: carbohydrate intake. Because many of you are not pushing the max amount of carb intake during training, while it’s one of the biggest limiting factors.

Third: run economy. Because every small improvement has a big impact, since it is not diminished by dense water or high speeds through air.

Swimming: increase swim economy

If you want to swim faster you can either put exponentially more energy into it, or improve your swimming technique.

Since swimming is the first discipline in triathlon, spending exponentially more energy can be a recipe for failure.

By improving your technique on the other hand, you’ll be saving energy instead. Spending less energy at a given swimming speed comes down to improving your swimming economy.

This graph shows why improving your swimming economy is such a good idea:

Energy Demand in VO2 (ml/min/kg)
Fig. 1: VO2 demand vs speed. Swimmer 1 (purple): swimming economy of an average age grouper. Swimmer 2 (yellow): swimming economy of an average competitive swimmer. Swimmer 3 (blue): swimming economy of an Olympian.

The graph shows 3 swimmers:


  1. Swimmer 1 (purple): swimming economy of an average age grouper
  2. Swimmer 2 (yellow): swimming economy of an average competitive swimmer
  3. Swimmer 3 (blue): swimming economy of an Olympian

If the age grouper wants to finish a 3.8 km swim in 60 minutes (1.05 m/s), it will require an oxygen uptake of about 40 ml/min/kg. If his VO2max equals 60 ml/min/kg, then he needs to swim at an intensity of 67% of VO2max.

While a VO2max of 60 ml/min/kg is realistic for a male triathlete who swims 3 times per week, a VO2max of 72 ml/min/kg is only found in competitive swimmers who swim at least once a day.

In other words: improving swim times by increasing VO2max is not time effective for an age grouper.

What would be effective is to fully focus on swimming technique and “shift” from the purple left economy line to the yellow middle economy line. As you can see, this would result in much faster swimming speeds, without the need to increase VO2max. Focusing on swimming technique could be part of the existing swim training program.

The good news: the lower your VO2max, the bigger the effect of technique training. This becomes clear in figure 1: at high VO2max values, the three curves converge.

Normative data swim economy

You can also use figure 1 to compare the data with your own swim economy.

The image shows that an average age group triathlete has a VO2 demand of 40 ml/min/kg at roughly 1.05 m/s (triathlon swim in 57 min.), while an Olympian would swim faster than 1.3 m/s (triathlon swim in 46 min.) at that energy demand.

In DER KONA CODE, Sebastian Weber says that the energy demand (VO2 demand) should be below 38 ml/min/kg per m/s swimspeed, to qualify for KONA. You can use this normative data to understand what you need to work on to get the ideal metabolic profile.

Measure swimming economy

If you don’t know your current swimming economy, then you don’t know how much you can improve. 

Also: to understand whether your technique training is improving your economy, you need to regularly measure changes in the swim economy. Not only from a feedback point of view, but also from a motivational point of view.

Measuring the swimming economy is not as hard as it may seem.

It requires a couple of sub-maximal swim efforts, a post-effort VO2 measurement and a pre- and post lactate measurement. These measurements enable you to differentiate aerobic and anaerobic energy supply.

Measurement of oxygen uptake determine energy requirements in swimming. These measurements can take place post-effort.
Measurement of oxygen uptake determine energy requirements in swimming. These measurements can take place post-effort.

You can also use this test to find out which swimming suit is increasing your economy most.

Once you have the data, simply import it into the INSCYD software and you’ll get the swimming economy. INSCYD also enables you to compare the swimming economy against other swimmers.

Fig. 2: Swimming economy: how fast can you swim with a given energy expenditure? In this INSCYD graph you can see how fast 2 swimmers (athlete A (red) and athlete B (black)) swim with a given energy expenditure. You can compare them against each other and against a control group.
Learn more about the details of performance testing in swimming via our swim use case and webinar.

If you want to implement this and other effective training practices, don’t hesitate to book a free consultation with us. We’d be happy to discuss how to implement these techniques into your training program in a way that works for you and your athlete. Schedule a free consultation with our team of experts.


What we call economy in swimming is similar to aerodynamics in cycling: going as fast as possible with the least amount of energy.

Aerodynamics are super important in cycling. However, once you have found an aerodynamic position that you can maintain during the whole ride, there’s not much to do about it.

So let’s focus on another opportunity for a faster finish time.

Energy availability during a triathlon

A triathlon requires a lot of energy. This energy mainly comes from fat and carbohydrates.

Regardless of body fat percentage, we all have enough fatty acids available. Carbohydrates are the bottleneck.

There are two sources of carbohydrates:


  1. Carbohydrates stored in the muscles. Also known as glycogen.
  2. Carbohydrates which you supply via food and drinks during exercise

Let’s start with glycogen.

It’s important to note that glycogen cannot leave the muscle cell. If your legs run empty on glycogen, you cannot transport glycogen from your arms to your legs.

When it comes to glycogen, the goal is to make sure your glycogen levels are as high as possible. You can do this by eating and resting well before a race. Although glycogen levels have an upper limit, there is still a great benefit in knowing your glycogen levels. Here’s why. 

INSCYD provides you with the amount of glycogen available per sport, based on body composition.
Fig. 3: INSCYD provides you with the amount of glycogen available per sport, based on body composition.

Let’s assume INSCYD shows you have a glycogen availability of 400 grams in the legs. For the sake of simplicity, we split 400 grams of glycogen equally between cycling and running.

If your bike split on a 180km (full triathlon) ride equals 5:00 hours, you have 40 grams of glycogen available per hour (200g ÷ 5h).

The INSCYD Fat & Carbohydrate combustion graph shows exactly how much cycling power you can produce when you have 40 grams of carbohydrates available per hour (fig. 4 A). Situation A shows that this specific athlete burns 40 grams of carbs at 160 watts.

Even with the best aerodynamics, it’s going to be impossible to ride 180km within 5:00h when producing only 160 watts.

This is where nutrition comes into play.

Energy intake during a triathlon

There’s an upper limit to aerodynamics. There’s an upper limit to glycogen stores. And as you can imagine, there’s an upper limit to energy intake.

To be a bit more precise: there’s an upper limit to absorption from the intestine into the blood.

60 grams of carbohydrates per hour was assumed to be the upper limit. However, if you combine glucose and fructose, the upper limit increases to about 90 grams of carbohydrates per hour. 

Consuming such high amounts of carbohydrates does require training! The good news is: yes, you can train your gut to maximize carbohydrate intake. Here’s how effective that is.

Remember no food intake resulted in a max average power of 160 watts (fig. 4 A)? With a carb intake of 60g/h, that goes up to 235 watts (fig. 4 B). If you’re able to absorb 90g/h, power can go up to 255 watts (fig. 4 C).

The INSCYD Fat & Carbohydrate combustion graph
Fig. 4: Carbohydrate consumption as a function of cycling performance. Assuming a glycogen availability of 200g and a cycling time of 5 hours (see text). Without carb intake, the max average power is 160w (A). With a carb intake of 60 g/h, the max average power increases to 235w (B). With a carb intake of 90 g/h, the max average power increases to 255w (C). Metabolic Profile: Male, 180cm, 75kg, 12% Fat, VO2max 60ml/min/kg, VLamax 0.5 mmol/l/s, efficiency: 23%.
Learn more about the effect of carb intake on your race performance via this article: How Carbohydrate combustion determines Pacing and Fueling.

Discover how to make small improvements that have a big impact on your performance in triathlon. Watch our upcoming triathlon webinar and learn some uncommon strategies to help you achieve your goals!

Running: increase run economy

The importance of energy intake remains during the run. But as we said, there’s an upper limit. So what can you focus on once you reach this limit?

Similar to swim economy and cycling aerodynamics: running economy!

Running economy is a very interesting parameter, because contrary to swimming or cycling, improvements in running economy are not diminished by dense water or high speeds through air.

When you’re able to increase your running economy, you can run faster for a given amount of carbohydrate intake. A 10% increase in running economy can save almost 30 minutes in a marathon (fig. 5)!

INSCYD Fat & Carbohydrate combustion graph
Fig. 5: Impact of running economy on carbohydrate combustion. Dashed line: poor running economy (> 13 ml/min/kg oxygen demand per m/s), solid line: good running economy (< 12 ml/min/kg oxygen demand per m/s). The poor economy (A) results in a speed of 3 m/s. The good economy (B) results in a speed of almost 3.4 m/s – with the same carbohydrate consumption. This difference corresponds to a time advantage over the marathon distance of approx. 27 minutes! Metabolic Profile: Male, 180cm, 75kg, 12% Fat, VO2max 60ml/min/kg, VLamax 0.5 mmol/l/s.

Measure running economy

What applies to swimming economy applies to running economy: you need to measure it to know how much you can improve it. Also: you need to track it over time to understand if your technique training has the desired effect.

The test protocol is also very similar: sub-maximal efforts with VO2 and lactate measurements.

Measuring VO2 in the field using an entirely face worn Analyzer by

With INSCYD you can choose to test the running economy in a lab, under standardized conditions, or in the field, where training and racing takes place. Learn more about the pros and cons of indoor vs outdoor testing for runners via this article: Indoor vs Outdoor testing for runners: which is better?

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In summary, we learned that:

1. Improving your swimming technique – and therefore swim economy – can be a much more effective and less time consuming way to improve your swim performance than trying to increase VO2max. To avoid wasting time on the wrong swim technique training, you do need to measure and track swim economy over time. Swim economy tests are getting more accessible, with INSCYD software.

2. Cycling aerodynamics are important, but there’s another big opportunity while riding your bike: energy intake. The more carbohydrates you can absorb, the faster you’ll go. It’s that simple. While the majority of triathletes is only able to absorb 30-40 grams per hour, you can train your gut to increase this number up to 90 grams per hour. No extra training time 

3. Improvements in running are super interesting, because they are not diminished by dense water or high speeds through air. Improving your running economy is therefore one of the best time investments. It can shave off 30 minutes of your marathon time. Similar to swimming economy, you do need to measure and track the run economy over time. Luckily, run economy tests are getting more accessible, with INSCYD software.

Now it’s time to put these tips into practice!

Looking to implement these tips in your training program? INSCYD can help! Coaches and Labs can become INSCYD certified to provide the ultimate training experience for athletes. And athletes, you can find an INSCYD Coach or Lab to apply these tips to your own training program. Contact INSCYD today to learn more.

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Don’t let your athletes settle for anything less than their absolute best. Book a Free Demo with INSCYD today and experience firsthand how you can elevate your coaching game.



Athletes why train with generic plans when you can have a program tailored to your unique physiology? INSCYD is the key to unlocking your full potential. Find your dedicated INSCYD coach or lab here. 

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