Introducing Intervals

New to triathlon yet scared of the swim? Fear not, as intervals are your pool-based friend and are guaranteed to boost swim speed

Dad chucked me in the deep end when I was little more than a baby,” explains two-time Ironman UK winner Dan Halksworth. “That was the spur to join the local swimming club that I’m still a part of today.”

There’s been no lack of graft since, but Halksworth, 29, happily admits that being raised in a family steeped in beach life eased the path to becoming one of the best swimmers in triathlon. But not everyone has the freedom to acquaint themselves with the water at such a young age, and when assessing the challenge of tri the landlubber’s greatest fear is often the swim. The good news is that most worries can be swiftly allayed and, and it’s always a great time to learn new skills without worrying about losing fitness.

pool beginnings

“Swimming in the pool is the best place to start,” says Halksworth, who has been one of the sports best swimmers throughout his career. “Open-water swimming – especially in the sea – can be daunting, but in the pool you’re never far away from something to hold on to.”

Employing a coach or investing in video analysis of your stroke will help with technical improvements, but when planning your own workouts, interval swimming is the way to go. “If you just swim up and down all day long, you will plateau,” adds Halksworth. “Reps increase speed and fitness.”

Intervals also provide structure, and whether concentrated on technique, speed or endurance, help maintain focus through the session; it can be easy for the mind to wander when following a black line on the bottom of the pool.

There are many other advantages. An onus on swimming different speeds cultivates an understanding of how much effort is required to up the pace (remember, you have both the bike and run to follow) and will develop a
change of gears – useful when stepping up to open-water racing where there might be a need to accelerate out of trouble.

Intervals also give the chance to benchmark for the different triathlon distances and monitor improvement, plus there’s less chance of technique slipping because you reset after every short rep as opposed to taking on one fatigue-inducing slog. Most importantly, though, whatever type of interval set you’re doing, they will simply help you swim faster on triathlon race day in both the pool and open water.

Where to start

Beginners can set their own levels or pluck up the courage to join club sessions. “I would always recommend swimming with a Masters swim squad,” says Halksworth. “It means you have a coach that can put you in the correct lane, look at technique and give you the positive reinforcement that often swimmers need.”

“Alternatively,” continues Halksworth, “swimming a timed 500m, for example, working out the pace per 100m and then doing a simple set of 10 x 100m with a 10sec rest between each rep works. Adapt distances depending on the length of your race and each month repeat a timed swim to see how you’re progressing.”

While front crawl is the domain of most triathletes, it’s good to mix up the training by adding a variety of strokes and even swim aids where possible. “When I coach juniors I always include medley sessions,” says Halksworth. “Working the areas in the pool you’re weak at can vastly improve strength and in turn technique. Kick drills, paddles and pullbuoy work will make you much stronger and more efficient. I also like to work on technique before we start using training tools, because if you can’t pull through the water correctly then using a pair of paddles could cause injury a few months down the line.”

When drawing up your own training plan, Halksworth believes it’s important to add in over-distance sessions. “It will make swimming the distance you’re racing easier,” he says. “Aim to build up distance and intensity to the event and always remember to have a rest day. With increased swimming you often get a lot of tightness in your back and chest, so take time to see a good massage therapist, too.”

The sessions, above right, lay out the different ways you can use intervals to improve your performance. Dan also provides a sample two-week beginner plan, below, that’ll help develop your swim in the off-season.

Five sample swim sessions

Dan Halksworth’s sets to help improve endurance, speed and technique, increase the strength of swim specific muscles, and help with recovery.


Warm-up 10 x 25m alternate freestyle/backstroke

Main set 5 x 100m freestyle, 20secs rest per interval

Cool-down 4 x 50m choice of stroke


Warm-up 200m choice of stroke, pick-up pace
either into or out of the turn

Main set 12 x 25m as: 12.5m fast, focusing on increasing arm speed; 12.5m easy, 30secs rest
per interval

Cool-down 200m very easy


Warm-up 3 x 100m in 25m swim/drill/kick/swim

Main set 14 x 25m alternating drill/swim. Try and change drills (ie. Single arm/catch-up/water polo)

Cool-down 200m easy but still focus on technique


Warm-up 200m swim

Main set 5 x 100m as: 100m breathing every 2 strokes; 100m breathing every 3 strokes; 100m pullbuoy; 100m pull and paddles; 100m breathing every 4 strokes

Cool-down 5 x 50m easy


Warm-up 5 x 50m freestyle

Main set 4 x 100m mixing strokes but all very easy

Cool-down 6 lengths to loosen up