How to Avoid a DNF in Your First 70.3 (Half Ironman): 9 Hard-Earned Lessons from a Certified Triathlon Coach
- 7 days ago
- 5 min read
Training for your first 70.3 is one of the most exciting challenges in endurance sports. But finishing isn’t a guarantee. Every year, thousands of first-time 70.3 athletes struggle with pacing, nutrition, heat, and open water—many ending with the dreaded DNF (Did Not Finish) instead of a medal.
As a coach and athlete who has lived this sport for 20 years, I speak from first-hand experience: I’ve made the mistakes, coached through them, and watched countless athletes transform from nervous first-timers to confident finishers.
If you’re planning to race your first 70.3, here are the nine truths I wish every athlete knew—truths that dramatically improve your chances of finishing strong.
1. Start Early: You Need at Least 6 Months of Training for a 70.3
A six-month 70.3 training plan provides enough time to safely build swim, bike, and run volume without risking injury or burnout. Many DNS (Did Not Start) and DNF outcomes happen because athletes compress the timeline and rush the build. I've actually turned away athletes who have come to me for coaching wanting to do Waco 70.3 only 10 weeks out from race day. I am not doing the sport justice if I chose to coach someone who didn't put in the required work for that distance. The only exception to this is someone who is just coming off several long course races, has a strong base, and is a very seasoned athlete.
2. Bike Fitness Is the Make-or-Break for First-Time 70.3 Athletes
The biggest mistake beginners make is underestimating the bike. So many first timers are reluctant to actually do their long rides outside. They have sort of become "married" to their trainer and feel overwhelmed going out on the road, and when they finally get outside, they see that they are only riding 13 mph (which can cause you a DNF) and realize how much work they need to do. Riding in a straight line, reaching for a water bottle, avoiding traffic, pedaling into the wind- these are all real skills that the bike trainer can't teach a cyclist. I tell athletes all the time- the race is outside and you should be too! .Whenever you have an opportunity to choose outside over the trainer, go outside!
3. Nutrition Is the Fourth Discipline (Most DNFs Are Nutrition Related)
Ask any experienced triathlon coach what takes out first-timers and they’ll say the same thing: nutrition and hydration.
Under-fueling, under-salting, over-heating, or GI distress can derail even the best training plan. The key to your nutrition plan is your sweat test- knowing how much fluid you lose and how to replace it. They best way to see what works is to practice! Get to know how much carbs, fluids, and sodium your body needs in race conditions to have success. Practice your nutrition strategy during every long ride and brick session—never experiment on race day. If you're not sure how all this works, get step by step instructions by investing $37 in my Complete Guide to Triathlon Nutrition here:
4. Get out in the open water- often
Pool times don’t always transfer to open water swimming. The comfort of swimming in a shallow, clear, warm pool is a lot different than choppy cold 60 degree water. Acclimate yourself to the open water as much as possible. Take a buddy and an ankle buoy and find a lake or river that is safe to practice in. Wear your wetsuit and practice getting in and out of it while there. You can't beat the confidence that comes with feeling good about your 2100 or 4200 swim.
5. Do a Swim Stroke Analysis with a Coach
The swim is what prevents many from entering into the sport of triathlon. If you are a non-swimmer or someone with very little experience the best thing you can do is a Swim Stroke Analysis with me. In this short test I have you swim 100 yards (a timed effort) and I video you swimming 4 lengths of the pool. I look at all parts of your swim stroke from different angles and make recommendations on how you can glide through the water with less effort and more efficiency. I take your videos and go through frame by frame then show you places where your form needs correction. You can get your Swim Stroke Analysis by clicking the purple button below. I can do this remotely as long as I have good clean video from you. After you sign up, I will explain how I need the person shooting the video to stand in order to give me quality swimming data.
6. Know the Cutoff Times and Where You Stand
I show every athlete the 70.3 cutoff times up front so they know exactly how much time they have to complete the swim, bike, and run with success. For example, if swimming is your struggle, you need to be out of the water at 1 hour and 10 minutes which is close to 3 min per 100 yards of swimming. I try to get the athlete to shoot for numbers below the actual cutoff to have some wiggle room in case something goes wrong. There is nothing worse than being pulled off the course as a DNF that you could have prevented by knowing your swim, bike and run times.
7. Practice Running on Tired Legs.
You will need to do at least 2-3 bike- to- run efforts each week while training for a 70.3. Running on tired legs teaches pacing, nutrition, timing, transitions, and muscular resilience.
You don't need to run for a long time during your brick- just 15 minutes is fine. The more you run off the bike on tired legs, the easier this will be on race day.
8. Gear and Logistics Matter More Than Beginners Think
From wetsuits to tire pressure to transition bags, small details matter. Race day is not the time for “I hope this works.” Test your gear ahead of time: bike fit, shoes, wetsuit, nutrition plan (this is a big one) helmet, bottles, goggles, sunglasses, etc. Leave nothing out.
Practicing your logistics reduces race-day stress and improves execution. I tell athletes to start packing at the beginning of the week. Start by laying out all of your gear then deciding which bag you will put it in etc. This keeps you from being up all night before race day in a panic at a time when good sleep is important.
9. Hire a Triathlon Coach.
Taking on a 70.3 is no easy feat. The worst thing you can do is download a free plan from google that was made for someone's grandma. Work with someone who knows the ins and outs of triathlon and iron distance racing. You will have questions (lots of them) along the way. As a coach I feel it is my job to keep an athlete out of the DNF woods. Working with a coach is a surefire way to train safely and know where you stand with your numbers. If you are looking for an experienced ironman coach, you have come to the right place. Click the purple button below and let's set up a quick call to talk about your goals and how I can help.
Final Thoughts: Respect the Distance and You Will Finish Strong
A 70.3 finish is one of the most rewarding milestones in endurance sports. Most DNFs are preventable with an experienced coach, time, preparation, a good nutrition plan, pacing, open water confidence, and realistic expectations.
Whether your goal is to finish, PR, or use a 70.3 as a stepping stone to a full Ironman, treat the distance with respect. I’ve coached athletes through all stages of the journey and I promise—your first 70.3 finish line is worth every hour you put into it.
Mary Timoney
Ironman University Certified Coach
USA Triathlon Coach
ACSM Trainer
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