Training for a half Ironman (officially called Ironman 70.3) takes most first-timers 16 to 20 weeks of structured preparation. The race covers 70.3 miles total: a 1.2-mile swim, a 56-mile bike ride, and a 13.1-mile run, completed back to back. That’s a serious endurance effort, but it’s very achievable if you build your fitness progressively and train all three disciplines consistently throughout the plan.
What a Typical Week Looks Like
A 20-week plan for a first-timer generally includes three swims, two to three bike rides, two to three runs, and one brick workout per week. The brick replaces a standalone bike or run session, so you’re not doing 10 workouts every week. In practice, that means training six or seven days with one full rest day.
Early weeks are lighter than you might expect. A solid starting point is roughly 3,900 yards of swimming, 2 hours and 45 minutes of cycling, and 1 hour and 45 minutes of running per week. That’s around 7 to 8 hours total. By the time you hit peak training around week 17, those numbers climb to approximately 6,700 yards of swimming, 5 hours and 20 minutes of cycling, and just over 3 hours of running. Peak weeks land somewhere around 10 to 12 hours, depending on your pace.
The weekly structure typically rotates. One week might emphasize longer rides, the next might shift the longer session to a brick workout. This rotation prevents burnout in any one discipline and keeps your body adapting.
Build Your Aerobic Base First
The single most important thing you can do in the first 8 to 10 weeks is build aerobic endurance at a low intensity. In heart rate terms, that means training at roughly 65 to 75 percent of your maximum heart rate, often called Zone 2. At this effort level, you should be able to hold a conversation without gasping.
Zone 2 training doesn’t feel impressive. You’ll run slower than you think you should. You’ll spin easier gears on the bike. But the physiological payoff is enormous: your body grows more mitochondria (the structures inside cells that produce energy), gets better at burning fat as fuel, and clears lactate more efficiently. All of this means you can sustain a faster pace later without working harder. USA Triathlon coaches recommend ignoring pace and power numbers during these sessions and simply staying in the right heart rate range. Over weeks, you’ll notice you’re covering more ground at the same heart rate.
A common mistake is going too hard on easy days. If every ride and run feels moderately difficult, you’re probably training in a gray zone that’s too hard to recover from but too easy to build real speed. Keep easy days genuinely easy so your body can absorb the harder sessions.
Why Brick Workouts Matter
A brick workout stacks cycling and running back to back with no rest in between. The name comes from what your legs feel like when you start running after 30, 60, or 90 minutes on the bike: heavy, stiff, and uncooperative. That sensation fades with practice, which is exactly the point.
Bricks train your neuromuscular system to switch from pedaling to running mechanics, and they let you rehearse the actual transition you’ll perform on race day. In the early weeks of training, bricks should be heavily weighted toward one discipline. You might ride for 60 to 90 minutes at a steady effort and then run just 10 to 15 minutes at an easy pace. The goal is simply to experience the transition, not to crush yourself.
As your fitness builds, the run portion gets longer and more race-specific. A typical late-stage brick for a half Ironman might be a 2.5 to 3 hour ride followed immediately by a 30 to 45 minute run with segments at your target race pace. Some athletes practice running the first 8 minutes easy, then settling into race pace intervals, which mirrors how you’d want to pace the run leg on race day after 56 miles on the bike.
Most plans include a brick workout every other week. That’s enough to build the adaptation without piling too much fatigue on top of your other training.
Fueling During Training and Racing
Nutrition is the fourth discipline of triathlon, and it’s the one most first-timers underestimate. During the race itself, a good starting target is 60 to 70 grams of carbohydrates, 400 to 600 milligrams of sodium, and 24 to 28 ounces of fluid per hour. If you have a sensitive stomach or you’re new to eating during exercise, start with 40 to 50 grams of carbs per hour and increase gradually over your training weeks.
Some athletes can tolerate up to 90 to 100 grams of carbs per hour, but that level isn’t necessary for most people racing a 70.3. What matters more is consistency: taking in fuel at regular intervals on the bike rather than waiting until you feel hungry or bonked. By the time you feel depleted, you’re already behind.
Practice your race nutrition during long rides and brick workouts. Use the same products you plan to consume on race day. Your gut is trainable, and athletes who rehearse their fueling strategy in training almost always have smoother races than those who wing it.
The Taper: Resting Before Race Day
The taper is the period before the race where you reduce training volume so your body can fully recover and arrive at the start line fresh. For an important half Ironman, a 17-day taper works well for most age-group athletes.
A common approach drops volume in three steps. The first week of the taper, you train at about 70 percent of your recent average weekly volume. The second week drops to 50 to 65 percent. Race week sits at just 25 to 35 percent, with most of those sessions front-loaded early in the week so the last two or three days before the race are very light. You keep the intensity of individual sessions relatively normal during the taper. You’re cutting how much you do, not how hard individual efforts feel. Short, sharp intervals keep your legs responsive while the reduced volume lets accumulated fatigue drain away.
Tapering feels strange. You’ll have extra energy and might worry you’re losing fitness. You’re not. The adaptations from months of training are locked in, and the rest is what allows you to actually access them on race day.
Recovery and Sleep
Training breaks your body down. Recovery is when the actual fitness gains happen. The most powerful recovery tool is sleep, and most athletes don’t get enough of it during heavy training blocks.
A practical way to find your ideal sleep duration: keep your wake-up time the same but go to bed an hour earlier for four days. If you still feel groggy waking up, shift bedtime another 30 minutes earlier. If you can’t fall asleep at the earlier time, push it 15 minutes later. Continue adjusting until you find the sweet spot where you fall asleep easily and wake up feeling genuinely rested. Even a 20 to 30 minute nap on a heavy training day can significantly improve alertness and recovery.
Beyond sleep, easy spinning on the bike or a short walk on rest days keeps blood flowing without adding stress. Foam rolling, stretching, and simply staying off your feet when possible all contribute. The athletes who recover best are the ones who treat rest with the same discipline they bring to workouts.
Dialing In Your Transitions
Transitions are the periods between disciplines: T1 (swim to bike) and T2 (bike to run). For age-group athletes, sloppy transitions can easily add 5 to 10 minutes to your race time, which is more than most people gain from weeks of speed work.
Keep your transition area minimal. You need your bike, helmet, sunglasses, bike shoes, running shoes, a race belt with your number, nutrition, and bike bottles. That’s it. Hang your bike from the saddle on the rack. Place your helmet open-side-up on your aerobars with sunglasses inside it so you grab everything in one motion. Lay your running shoes in front of the bike with laces loosened or use elastic laces that don’t need tying.
On race morning, note exactly where your spot is. Find a landmark like a tree, light pole, or row number, and count how many rows from the swim entrance you are. After swimming 1.2 miles, your brain will be foggy and the transition area will look different from the athlete’s-eye-view you had when setting up at 5 a.m. A clear mental map saves you from wandering past hundreds of bikes in a daze.
Practice transitions during your brick workouts. Time yourself going from bike to run, and you’ll quickly identify what slows you down. Most of it comes down to keeping things simple and eliminating decisions. If everything is laid out in the order you’ll grab it, the whole process becomes automatic.
Putting the Plan Together
A 20-week half Ironman training plan breaks roughly into three phases. The first 8 to 10 weeks focus on building your aerobic base with gradually increasing volume at low intensity. The next 6 to 8 weeks are the build phase, where you add race-specific intensity: tempo rides, threshold runs, longer bricks, and open-water swims. The final 2 to 3 weeks are your taper.
If you’re coming from a running background, you’ll likely need to invest more time in swimming technique early on. If cycling is your weakness, prioritize longer rides on weekends. The beauty of a 20-week timeline is that it gives you room to address your limiters without neglecting your strengths.
Consistency matters more than any single workout. Missing one long ride won’t derail your race. Missing three weeks because you got injured doing too much too soon absolutely will. Build gradually, recover deliberately, practice your nutrition, and trust the process. By race day, the fitness will be there.