Training for a Half Ironman (70.3) is equal parts endurance, nutrition, and smart pacing. Over the last few months, I’ve spent countless hours in the pool (plus on the bike and run) to prepare. Below is the nutrition and timing strategy I’m trying out for race day.
I normally like to show my work, but I pulled all my Strava/training data into postgres, used sql to get all my run, bike, and swim data over the last year and did some regressions to understand my pace with common formulas. This post is just the plan, the code, etc is in other posts.
Based on recent ~2–2.5 km swims, I’m estimating 40 minutes for the 1.2‑mile portion. That’s a comfortable pace—fast enough to set up a solid bike, but not so hard that I’m gasping in transition.
I’m guessing 3 minutes or so for transition, factoring in wetsuit removal and the hustle to the bike. My training rides suggest an average 16–17 mph pace over rolling terrain. This translates to 3 hr 15 min–3 hr 30 min for the race, depending on conditions (wind, elevation, etc.). Guessing ~2 minutes to rack the bike, throw on running shoes, and grab nutrition. From run data, I’m aiming for ~8:30–9:00 per mile pace off the bike, targeting 1:50–2:00. If I nail the bike intensity and nutrition, I should stay closer to 1:50–1:55. Overall, that means ~6 hours total, give or take 15–30 minutes, depending on transitions, weather, and race‑day magic. Bah, I think I can do so much better, but this is the attempt.
My fueling strategy focuses on sustaining consistent carbohydrate intake throughout the race by aiming for around 60–90 grams of carbs per hour on the bike, then scaling down slightly to 40–60 grams per hour on the run. To achieve this, I prepared each 750 mL Gatorade bottle with approximately 80 grams of carbohydrate (mixing six tablespoons, or about three‑eighths of a cup of powder), providing 320 calories per bottle.
To save anyone else the time, I’m showing my math for one thing, nutrition.
To ensure each of my \( 750\,mL \) bottles contains approximately \( 80\,g \) of carbohydrates, I used the nutritional information on my Gatorade container. The container specifies a relationship between tablespoons (Tbsp), milliliters (mL), and grams of carbohydrates:
$$ 1.6667\,\text{Tbsp} \,=\, 24.64465726\,\text{mL} \quad\Longrightarrow\quad 22\,\text{g carbs}. $$
From this, I can derive:
$$1\,\text{Tbsp} = \frac{22\,\text{g carbs}}{1.6667} \approx 13.2\,\text{g carbs}.$$
and $$1\,\text{Tbsp} \approx 14.78\,\text{mL}.$$
My goal is to reach about \( 80\,g \) of carbohydrate per bottle. Hence the number of tablespoons, \( N_\text{Tbsp} \), needed is:
$$N_\text{Tbsp} = \frac{80\,\text{g carbs}}{13.2\,\text{g carbs/Tbsp}} \approx 6\,\text{Tbsp}.$$
In terms of volume:
$$6\,\text{Tbsp} \times 14.78\,\text{mL/Tbsp} \approx 88.7\,\text{mL} \quad\approx\, 0.375\,\text{cup}.$$
Therefore, by adding roughly 6 tablespoons of Gatorade powder (about 3/8, cup or 90 mL of powder) to 750 mL of water, I obtain a mix that delivers about 80g of carbohydrates (and roughly 320kcal). This mixture provides a consistent carbohydrate concentration (approximately 6–8%), which is both palatable and effective for fueling during long training sessions or races.
Drinking one bottle per hour meets my baseline carb goal of about 80 grams per hour on the bike. For additional carbohydrate or if I want to reach closer to 90 grams per hour, I incorporate Maurten gels that each provide roughly 25 grams of carbs. These gels also become key during the run, where I take one every 20–30 minutes to match my target of 40–60 grams of carbs per hour.
Recent sweat tests show that my fluid loss rate varies significantly with both temperature and activity intensity. For example, a higher‑intensity run in warm, dry conditions (76 °F and 28% humidity) resulted in losing about 3.1 lb of body weight in just over an hour—roughly 1.4 L (48 oz) per hour. Conversely, a cooler bike session (53 °F, 68% humidity) saw losses closer to 1.0 L (34 oz) per hour, while a shorter ride at 54 °F and 69% humidity required only about 0.5 L (16–17 oz) per hour. These data suggest I should plan fluid intake anywhere between 0.5 and 1.4 L per hour, depending on the temperature, humidity, and how hard I’m pushing.
Given all this, I plan to drink around 24 ounces (one 750 mL bottle) per hour while cycling, then switch to 12–20 ounces per hour on the run. Gatorade supplies a good amount of sodium and it’s a cool 56 degrees tomorrow so I don’t need more.
I had a carb‑rich dinner the tonight, followed by a light breakfast containing about 80–100 grams of carbs two to three hours before the start, plus 16–20 ounces of fluid to begin the day well‑hydrated. In transition one, I can take an extra gel if I feel I need a boost before heading out on the bike, and transition two simply involves a quick fluid sip, changing shoes, and picking up the gels I’ll need on the run.
Let’s see how this goes …. Ok. Race report. The swim was cancelled since the water was too choppy. Disappointing. Additionally, it was pouring monsoon bad at the start. It was confusing. The whole transition zone was empty with people walking their bikes away. Folks were taking shelter next to the port a potties. I got soaked and sought refuge in the nearby hotel.
When the race started, I was surprised to be passing a lot of folks in fancy bikes with those cool aero helmets. Using the aero bars wasn’t that comfortable and with a 30mph crosswind, the bike was sliding around. Lots of folks were fixing flats and the course had some crazy sharp turns and narrow sections. The worst was the bridge where I was on the very edge of stability.
The overriding dynamic was that I needed to pee. Like miles 18 to 26, then miles 48 to 56 were intensely uncomfortable. The only option was two longer waits for a temp toilet. The impact was that the aero bars were super uncomfortable. Despite the wind, etc. I nailed my time with 3 hr ride and convinced I could have done 20 min faster if I could keep fluids in and not be so afraid of the aero bars. My average heart rate was around 120, lots of room to go faster. Power was around 200W. Nutrition was incredible. Never hungry, tank was full. Just too full of water.
The run was awesome. Just cranked in 7:30s and counted down the miles with HR around 165 to 170. Ended with lots in the tank and did a couple mile cool down on the bike. Watch time was 1:38 for the 1/2 marathon.
Now time to get better at this. This was way way different than my ultra.
References:
- Josh Gordon
- Ben Boehm
- Jeukendrup, A. E. (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine, 44(Suppl 1), 25–33.
- Burke, L. M., Hawley, J. A., Wong, S. H., & Jeukendrup, A. E. (2011). Carbohydrates for training and competition. Journal of Sports Sciences, 29(sup1), S17–S27.