4 intensity swim levels you should include in your freestyle training

Tri swim coach Rory Buck explains four different intensity levels, and why and how you should be adjusting your front crawl pace in your swim workouts.

Swimmer perfecting his swim pacing in training

Do you find your swim workouts boring? Haven’t seen much of an improvement in your speed or swim fitness recently? If so, it’s little wonder you haven’t been motivated to hit the water as often as you should.


Changing up the intensity in your swim workouts may give you the boost in motivation you need. By varying your speed and intensity, you’ll make each swim workout a little more exciting (no more boring laps). You’ll also build rock solid swim fitness (hello faster pace for longer)!

Why Vary Intensity?

Aside from the fact that swimming at one pace for an hour is mind-numbingly boring, changing up your speeds has a very clear training benefit. The purpose of training is to bring about physical changes in the body. The goal is to train to be be able to deal with the physical stress you will experience on race day.

These physical changes come about when you place your body under training stress. We can manipulate the training stress you place on your body by changing the pace or intensity that you swim at. Different intensities create different types of stress.

Most triathletes I talk with are very familiar with these concepts. They apply them to intervals on the bike bike or tempo run workouts. But for one reason or another they struggle to carry the concepts over to their swimming.

By changing up the intensity in the water, you can create workouts that are stimulating, interesting AND that will help you get faster.

Swimming at different speeds will give you the endurance to hold a consistent pace… the speed to take a gap or find your own space off the start… and the control to know how fast you are swimming. Get the balance right and you will be hitting T1 positioned further up the pack and feeling much fresher.

Let me introduce you to 4 different intensity levels I work through with my swimmers. With this knowledge you’ll be ready to create highly effective workouts that will get you excited about your next trip to the pool!

1. Recovery Pace

Relaxed easy swimming

Speed: Slow

Zone: 1

RPE: 1-2

Your recovery pace is the like a slow morning walk on the beach. When you’re swimming at a recovery pace you should have absolutely no problem breathing. You should feel your whole body relax in the water and your movement should be slow and methodical.

We generally use recovery swimming in the cool down of our workouts. From time to time we’ll include it early in the warm up too (this feels especially good after a long bike ride or run).

Even though the pace is slow, you should still focus on swimming with good technique. There isn’t a great deal of training stress at this pace so we can use the time to master our technique.

Example of a short, easy recovery set:

4 x 50m easy + fins

 Pro Tip:

Set your watch to ‘drill mode’ or turn it off during your recovery sets so you aren’t tempted to push the pace up. Recovery means recovery!

2. Endurance Pace

– Steady sustainable pace

Speed: CSS Pace (Critical Swim Speed Pace), + 5

Zone: 2

RPE: 3-4

An endurance pace should feel similar to your jogging pace. When you’re swimming at this pace you’ll feel comfortable. You should be able to find a groove and keep a low heart rate. It shouldn’t be particularly challenging – it’s a pace you could hold all day.

We use this pace during drill sets and technique focused workouts. We’ll also swim at this pace to help us recover between challenging speed or CSS sets.

If you are training for a full distance Ironman, you may do some of your key sets at this pace. It’ll build your stamina and improve oxygen delivery to your muscles.

Example of an endurance set:

●  2-6 x

[1 x 100m Drill 1 x 400m Perfect Technique Freestyle]

*Rest 10-15 seconds between repeats (if that’s not enough rest you’re swimming faster than your endurance pace)

Pro Tip:

A lot of technique focused triathletes spend too much time swimming at this pace. Here are two signs you’re doing too much endurance pace swimming:

1. There isn’t much of a difference between your sprint and long distance pace.

2. You feel more than comfortable swimming any race distance (750m to 3.8km). But despite good technique and consistent training you aren’t getting any faster.

3. Threshold Pace

Hard sustainable pace

Speed: CSS Pace

Zone: 3/Low 4

RPE: 5-7

Threshold pace swimming tends to be the magic key that will move you way up the pack on race day. Swimming at threshold pace gives you the best return on investment for your time in the water. When you are swim at threshold pace you will be breathing heavily, but you should still feel comfortable early on in the workout. As the set progresses however, you will start to feel more and more uncomfortable.

Doing intervals at threshold pace builds muscular endurance, sustainable speed and stamina. The combination of these three makes it perfect for triathletes wanting to build their swim fitness.

Threshold swimming will also give you a keen awareness of your pacing. Swim too fast early on in a threshold set and you are guaranteed to suffer later. You won’t make that mistake too many times before you learn what the right pace is!

Like fine red wine, too much of a good thing isn’t always a good thing. While swimming at your threshold pace gives you the biggest bang for your buck when developing your swim fitness, your body will adapt to your threshold pace. You need to test or adjust your threshold pace every 4-6 weeks to ensure you are getting the full benefit.

An example of a threshold set:

●  10 x 150 @ CSS Pace

*Take 10-15 seconds rest between each 100

Pro Tip:

If you are consistently swimming at threshold pace and you are not seeing improvements in your speed, there may be one of three reasons why:

1. Your threshold pace is incorrect.

 Solution: Retest your Threshold Pace. Work off your new pace and see if you break through the plateau.

2. You are not swimming consistently enough.

 Solution: Swim a minimum of 3x per week for a month and see if you break through the plateau. Already doing that? Add an extra swim workout every week.

3. You have a fundamental technique problem.

Solution: Technique will set the limit on where your fitness will take you. If it’s a technique problem, get a video analysis done to identify what’s holding you back.

Front crawl technique: the key components

Open-water swim technique: the key components

4. Speed Pace

Fast pace that cannot be sustained

Speed: CSS Pace – 3 or more seconds

Zone: 5

RPE: 8-10

This is fast swimming. When doing speed work you will find it difficult to maintain the intensity without long rest.  You’ll feel out of breath and your muscles will burn!

We use speed sets to develop top end speed. That top end speed comes in handy during a race start or when you need to take a gap or make a break. We also use it to develop mental toughness.

It’s important to include some speed swimming in your workout plans but we use this type of intensity sparingly. Swimming fast with long rest in every workout isn’t the most appropriate way to train for any triathlon race distance. A little bit here and there will keep you sharp but too much speed work and you’re not to going feel great on the back end of your race swim.

An example of a speed set:

● 4 x 75m Sprint

*Rest 2-3 minutes between each 75m

How Can You Apply This To Your Training?

Now that you understand the four basic swim speeds you should be able to create much more interesting workouts. Not only will your workouts be less boring but they will also be more effective. You can use the knowledge you’ve just gained to help you target your weakness and turn it into a strength:

● Can you swim for miles and miles at one pace but can’t find any speed? Do more threshold training and speed work

● Can you nail your threshold sets but struggle to maintain your pace in the last 10-15 minutes of your 3.8k IM swim? Spend more time swimming at your endurance pace with less rest.

● Are you exhausted after swimming 25m and need to rest for a minute before you start the next length? Slow down! Do more endurance swimming and threshold training.

If you were varying your intensity on your interval rides and tempo runs, now you know how to change it up in the pool too.

Swimming at each of the 4 different intensities will give you the endurance you’re looking for… the speed want… and the pace control you know you need.

Get swimming!


Rory Buck is a triathlon swim coach helping time-starved and swim weak triathletes revamp their swimming. He is the head coach of SwimFast Dubai and creator of ICanSwimFast.com, which helps triathletes like you develop efficient technique, build better endurance and grow unshakable open water confidence! Read his free detailed guide: The Fundamentals of Triathlon Swimming  You can follow Rory on @ICSwimFast