Ironman Swim Training: Endurance Or Interval Sessions?

  • By Paul Moore
  • Published July 20, 2011

The 3.8K swim of an Ironman is, without a doubt, a long way to go. But is it necessary for Ironman athletes to spend most of their time doing straight, slow swims to prepare for the distance, or are they better off sticking to interval work? We put our resident swim expert, Sara McLarty, up against Trey McKinnon, a certified coach.

Trey: With regard to beginner to intermediate long-distance athletes, I feel there is little substitute for endurance training. While a sprinter can get by on short build sets, the endurance swimmer has to get accustomed to the continuous activity so that he or she will be successful not only in the swim, but also the long bike and run.

Sara: I agree that any novice triathlete needs to build up endurance. But swimming non-stop tends to be treated like a “chore.” By giving a beginner sets and intervals to complete in the pool, he or she can be assigned short-term goals.

Trey: I agree that long, slow sets in the pool can be truly mind-numbing, but they allow the athlete to build the aerobic base and muscular endurance necessary to complete the IM-distance swim without compromising technique—which often happens when the swimmer gets too fatigued. To break up the monotony, I have my athletes finish each 100 with a fast 25 to start, or to have them time and record their long sets to track their progress.

Sara: Long bike rides and long runs will provide all the endurance training they need. Every training programme, no matter the athlete or race, needs to have variation in intensity. No one does the swim at one pace, so by swimming interval sets, athletes will be more prepared for what they will be feeling in the race. Plus swimming is low-impact and is perfect for high-intensity workouts with little fear of injuries.

Not all interval training has to be short distance with long rest. Here’s an example:
2–4 times through the set
[3×100 swim, strong effort, with 15 seconds rest; 2×200 pull, smooth effort, work on perfect technique, with 30 seconds rest]
1400–2800 metres total

Trey: I agree that swimming is low-impact, but that doesn’t mean it won’t take the same toll on glycogen stores and contribute to overall fatigue. And fitness in one discipline doesn’t equate to fitness in another. A hard interval swim can wipe a novice out, no matter how aerobically fit they are on the bike and the run.

While I like to have my novice athletes work in the upper zones periodically, it should be used in proportionate doses. You wouldn’t have an Ironman athlete spend the majority of his or her run or bike in training zone 4 or 5; you spend the greater percentage of time on zone 2 base work.

Final Thoughts:
Both have a place in your swim training, even at the Ironman level. You need to get used to being horizontal in the water for a long period of time, so some straight, long sessions should be part of your training, But intervals are necessary to make speed gains and keep things interesting!

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Paul Moore

Paul Moore

Paul Moore is the Online Editor for Triathlete Europe. When not glued to a computer he can be found writing books - most recently Ultra Performance: The Psychology of Endurance Sports and The World's Toughest Endurance Challenges. Both are available on Amazon. Paul has also written Ultimate Triathlon: A complete training guide for long-distance triathletes which is also available on Amazon.