Training for a half distance when you come from running

What your running actually buys you

A real aerobic base, tendons and bones that already tolerate impact, and the habit of training week after week — which is the part most newcomers lack. It also buys you the last leg: the run is where age-group races are won and lost, and you arrive with the engine for it. What it does not buy you is water skill, or the specific durability to be on a bike for hours. Those are trained, not transferred, and they are the reason your first block will feel like a step backwards in running terms while you are in fact getting fitter overall.

The half-marathon pace illusion

The single most common mistake a runner makes in this format is planning the run leg off their standalone half-marathon pace. You will run meaningfully slower, and how much slower depends almost entirely on how you rode. Train for that specifically: do your race-pace running immediately off the bike rather than as one more fresh-legs tempo, and rehearse the first three kilometres deliberately, because that is where most run legs are thrown away by setting off at a pace the bike has already spent.

The bike is the race

The half-distance bike leg is long enough that the intensity you hold on it sets the ceiling of everything after. It is ridden at a sustained moderate effort — tempo, not threshold — and the discipline of staying there while people ride past you is most of the skill. If you have a power meter, hold a target band and watch it rather than your legs, which will happily lie to you in the first hour. If you do not, ride by heart rate and feel, keeping in mind that cycling heart rates sit a few beats lower than running ones, so reusing your running zones on the bike puts you too hard all day.

What happens to your running week

Fewer runs, and that is the right trade. Two to four a week is the usual shape, and three is the common one: a quality session, a long run, and an easy run or the run leg of a brick. The count matters less than the placement — your hard run must not sit against your hardest ride, or you have built a two-day block that neither discipline benefits from. And the easy sessions have to be genuinely easy in all three sports, not just in running: the familiar principle of keeping the large majority of your training comfortable applies to the whole week, and the bike is where triathletes quietly break it.

The swim, from surviving it to training it

Most runners start by wanting to know whether they can cover the distance. Answer that first — in a pool, without stopping — then stop treating the swim as a hurdle and start training it, because two sessions a week held for a whole block change it more than any single heroic effort. Once you can swim the distance comfortably, a two-distance pool test gives you a critical speed and your sets get real targets instead of vague laps. The 200/400 m test is its own guide.

What Coach Leo does here, and what it will not claim

Leo sizes the block on the legs of your race rather than on a distance you typed, and for a half distance that means at least three rides and two swims a week alongside the runs your history says you actually do. All three sports count toward one training load, so a heavy week on the bike reads as a heavy week and your running eases instead of stacking. The bricks arrive in the closing weeks, on the long-ride day. What Leo will not do is tell you your finish time: it does not estimate an overall triathlon time, does not project splits, does not model your power without a power meter, and does not coach your stroke from a video. The full picture is on the half-distance page and on Coach Leo for triathletes, and the brick guide covers the session this format lives on.

Frequently asked questions