By Dave Scott

Q: “I’m training for an Ironman. To be prepared for the swim, do I need to swim the whole Iron-man distance, 2.4 miles straight, in a workout? How often should I do that? What other kinds of swim workouts could I do in place of 2.4 miles and still be ready?

— J.S., NYC, NY.

Dave Scott: This is a good question. I’ve had a number of athletes ask if they need to do the whole Iron-man distance in a swim session and if they need to do it regularly.

First of all, yes, you should swim the full distance a few times in training. The reason is primarily to check on three items: 1. Shoulder and upper back fatigue: can you go the distance and maintain solid mechanics? 2. Do your lower back and mid back tighten up during the swim? Keeping your head low, maintaining a soft flutter kick with minimal knee flexion, and not overreaching on your entry will help prevent muscular overload. 3. Do your hip flexors get tight and add to the lower back strain? Drawing your belly in lightly, without impairing your breathing and while maintaining the low head position, will stop the hip flexors from being overactive on the swim.

I’ll use an example of an athlete that I coached for the world championships in Kona. His hip flexors tightened up three-quarters of the way through the swim during the race. The tightness affected his lower back and his hamstrings, and when he got on the bike, he was unable to fire his gluteals. His hip flexors were overactive, putting stress on his lower back. Consequently, he lost about 25 percent of his power. In hindsight, it was really a coaching error of mine to not have him swim the entire distance during his Ironman preparation. The reminders noted above would have allowed him to focus on maintaining proper mechanics when he started to feel fatigue.

If you’ve got three or four months to build up to your Ironman, then you’ll want to include three to five swim sessions of 2.4 miles during that period.

MORE: Dave Scott on Using Anaerobic Endurance Training to Boost Performance.

Some people do this every week, but a better idea is to include different kinds of sets in your swim training. The benefits of the following sessions will improve your Ironman swim fitness.

Include a mixed lactate threshold (LT) set once a week for the entire three- to four-month training block. The range of the mixed LT set is 1,800 to 2,800 meters. A mixed lactate threshold set means a percentage of the workload is at LT and a portion is 2–5 percent below LT. The combination of mixing LT work and slightly below threshold work increases the percentage of fast-twitch 2a muscle fibers. At high intensity, the 2a muscle fibers, which have a higher contractile force and burn muscle glycogen at a higher rate, will assist the slow-twitch fibers. The end result is your economy and speed will be improved. I use this type of training with all my athletes—elite to first-timers. For beginners, LT is around the highest sustainable pace they can hold for 20 minutes. That goes up to 60 minutes for elite athletes.

Here’s an example: 6 × 300 meters with 10–30 seconds of rest between repeats. The first 300 meters would be at race pace, or even slightly faster. The second 300 meters is at sub-threshold, about 2–5 percent slower than your threshold pace. And the third 300 meters is at your threshold pace, so a very hard effort. Repeat that sequence twice. Now we’ve got a pretty challenging 1,800-meter block. You can increase the distance, or lengthen or shorten the repeats, as your training progresses.

You can also alternate this type of training by week. On the odd weeks, repeat a shorter distance of 75–300 meters, like the example above. On the even weeks, try longer segments, such as 5 × 400 meters or a ladder of 800-600-400-400-600. If the pace falls off the desired mixed LT range, then increase the recovery between the repeats.

Do anaerobic endurance (AE) sets two or three times per week minimum. I often suggest doing one AE set in each swim session, up to five times per week. A lot of athletes and coaches scoff at this suggestion and ask, “I’m doing an Ironman, why would I want to do something fast and hard?” Because you still want to stimulate those fast-twitch muscle fibers. And opening up the neuromuscular pathways is vital to maintaining fluidity and economy at all speeds. I include these sessions with all the athletes I coach.

An example is: 6–10 × 25–100 meters, with 20 seconds to 1 minute of rest. You could do a mixed set of 4 × 25, 4 × 50, 1 × 75, 1 × 100. As the segments get longer and you become more fatigued, take more rest to keep the quality very high.

These can also be implemented in the reverse order or by mixing the distances.

Include VO2 max sets in your Ironman swim training. You’re going to get a huge return on this intensity, because the segment length requires a combination of anaerobic and aerobic energy systems, tolerating high levels of muscle acidity, resynthesizing the acidity, and stimulating the faster fibers. Additionally, it’s going to enhance the powerhouse of the cell: the mitochondria. Include these sessions regularly for a four- to seven-week block, stop for two weeks, and then bring it back into your program with six weeks to go to your race.

An example is: A 12- to 18-minute set, for example 6 × 2.5 minutes, with an active recovery of 3 minutes between each effort. The distance will vary based on your ability, so for some people that might be 100 meters and for others it might be 300 meters. These are not as fast as the anaerobic endurance sets, because the segment length is longer. The ideal segment length is 3–7 minutes, with shorter segments where you’re trying to maintain the output. For example, with my elite athletes, we have done the following set: 3 × 75 meters on an ascending sendoff of 55 seconds, 1 minute, 1:05—holding the same speed throughout (which is around 50 seconds for 75 meters for the elite athletes) and then going straight into 225 meters. Again, the goal is to match the same speed on the 225 meters as you held on the 75s. It’s a very difficult set! Allow 3–8 minutes to recover and then repeat the set two or three times.

All these workouts will give you a good return on your Ironman swim training. I also would suggest something unique, which I do with my swim group. I include hard backstroke to work the rotator cuff and muscles of the posterior chain. We also do head-up breaststroke pulling for the same reason, plus it puts a load on your lats, which will come in handy in the 2.4 miles. And we use paddles, sometimes integrated in the other sets for 400–1,000 meters. Again, it’s trying to increase the load and tension to activate the fast-twitch muscle fibers.

The four types of workloads described above—steady-state swim, mixed LT, anaerobic endurance and VO2 max—can be included weekly leading up to the race. During race week, the mixed LT and AE sets are key, but reduce the volume by 50–60 percent. All these things prepare you properly for the 2.4-mile swim without putting your to sleep in your workouts. Put some intensity in it!

Dave Scott is a Six-Time Ironman World Champion. For more info on Dave and his camps, visit DaveScottinc.com