How Long is Long?

A long run, bike and swim are all staples of a triathlete’s schedule. But what constitutes long? How far should an athlete go? Obviously it’s dependent on the goal event: an Ironman triathlete needs more than a sprint specialist. Focussing on long distance racers, how much time should be invested in a single session?

You may have been told you need to cover a certain mileage before race day. You must ride 112 miles or run a marathon. Is that really essential? I understand arguments about the confidence gained by covering the distance, but are you insufficiently trained if you’ve not ridden more than one hundred miles in training? And I’m not suggesting one hundred miles is essential; there’s no magic number.

We should be cautious focussing on specific distance goals for long sessions. We need to develop our endurance fitness, to build the length of time we can sustain aerobic activity. There’s no special distance that produces the fitness for an Ironman. If you never ride more than fifty miles then it will be a challenge, but covering 112 doesn’t guarantee success.

Long sessions train the body during periods of fatigue and reduced glycogen. Strong stresses that develop fitness and drive adaptations for sustained aerobic activity. From the cellular level up the body becomes better able to fuel and sustain activity over time. You finish a marathon because long runs have caused these changes, not because you ran 26.2 miles before.

Recovery is what should determine your longest sessions. You need to train long, but how well you can train overall matters. An athlete training for his first Ironman posed the original question. Is there any point running for more than 2.5 hours in training? Ironman veterans were telling him he needed to run for three, but he knew that would heavily fatigue him; the following day’s training would suffer.

I’ve run for three hours and subsequent training has suffered. I’ve run for 2.5 hours and the following days were fine. So I rarely run more than 2.5 hours because I know that it sets me back. That extra half hour on my feet may induce more adaptations for aerobic endurance, but being able to train well the next day is better still. Marginal gains from thirty minutes too far are lost in subsequent sessions.

With recovery in mind the limitations on distance vary across the disciplines. Swimming is low impact, recovery time relatively short. An Ironman athlete can cover race distance at least once in training without significant consequence. Stronger swimmers should reach that target regularly, but at least one 3.8km swim is a worthwhile confidence boost. As long as you can train well with a long swim in the program give it a go.

I progress my athlete’s long rides up to around six hours, if they have that time. For some this will be close to or over the 112 miles, but for all it’s a significant distance. The physiological adaptations from six hours of riding are sufficient for Ironman racing. For most the gains of going on to cover 112 miles won’t warrant the time.

I specifically prefer more rides in the four hour range. There’s an opportunity to work harder and practice race pacing or feeding without huge fatigue. The bulk of my longer rides fall between three and four hours, most of it at a solid pace. The longest rides are more occasional and I wouldn’t push them until I was confident of fitness.

Running is the area of biggest concern. Not surprising given the larger fatigue impact and bigger injury risk. It is rare for athletes I coach to run beyond 2.5 hours; those that do, do so rarely. If an athlete can run for three hours, maintaining quality and follow it with good sessions I’ll let them occasionally go that far. If they fade strongly, they aren’t ready for the distance; if they struggle in the coming days, it isn’t an effective way to train them.

There are no strict rules. No minimums or maximums. Going further will produce greater training stress, but has to be balanced with recovery. When recovery is impaired and subsequent sessions affected you need to consider the value of that distance. It’s not wrong to go longer, but it’s not essential either; don’t be tied to specific mileage goals. You do not need to complete an Ironman in training to race it.

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From nutrition to pacing - a collection of CoachCox blog posts focused specifically on Ironman training and racing.


  • Ian Tivey

    The length of the longest session is also dependent on other training being done outside of those long sessions (i.e. for someone working Mon-Fri, during the week). There are loads of examples of reports of top marathoners having never ran more than 16 miles in training yet are able to run <2:10 marathons. These guys are running 150 miles a week though, so the level of continual fatigue is huge. For weekend warriors perhaps they do need to do the 100+ mile rides and 3 hour runs in order to become exposed to the level of glycogen depletion required for adaptation. If you're getting in 20+ hours a week of well rounded training then I agree that the longer sessions do not need to be of such length because the muscles will be depleted from the first pedal stroke/stride.

  • Fair points Ian.

    Higher volume of training does effectively mean more time is spent in a glycogen depleted state. That said even for a weekend warrior I’m just not keen on really long runs. I’m a little less concerned by long bikes, though there’s a point where if the pace is dropped to handle the duration I feel some value is lost. It’s never long slow, always long steady and there should be a distinction.

    The issue with very long sessions for the weekend warrior is they can be particularly distinct from all the rest of the training. They’re quite and extreme change from regular training sessions. If you mostly do at most an hour per weekday, it needs time to build to doing 6+ hour rides or 3 hour runs at the weekend. That time to develop the endurance is certainly something I could have covered more. With any long session, but particularly running, an athlete needs to build up to the duration. When someone talks of the value of 3 hour runs, how much of the benefits actually came from the long runs building up to 3 hours?

    As I say, no right answer. I do have one athlete who has had 3 hour runs in their training schedule and a couple who have done marathons earlier in the year. They work or fitted with those athlete’s aims. It’s all individual in the end.