Intro to Triathlons Pt. 2: The HOW of Transition from Marathons to Tri’s
Last week, we learned about why triathlons might be the logical next step for you after you’ve done a marathon. This week, we’ll look into the basics of triathlon training to get you started on your journey!
Before we begin, here’s a little warning: despite balancing your training out, triathlons tend to have a higher injury incidence than endurance running, both during training and on race day.
According to Triathlete, “A recent study of ultra-endurance runners, cyclists, and triathletes found a self-reported overall injury prevalence of 50%, with the highest number of injuries per athlete reported by triathletes. A 2022 review study reported an overuse injury rate of 37-91% and an acute injury rate of 24-27% in triathletes.”
This being said, take care of yourself out there, listen to your body, and don’t skimp on recovery, proper meals, and good sleep!
Minimal gear that you’ll actually need
The first question you might have when it comes to triathlon training is what gear you’ll actually need to get into the sport. The good news is that you don’t need $500+ specialized tri suit right off the bat!
Don’t immediately spend a fortune on new race kit. You don’t even know yet if you’ll like triathlons! Borrow, rent, or buy used gear at first. Do one race, then spend money once you know you’re in.
Make your runner-to-triathlete transition simple
If you’re juggling work, school, friends, and being a person, the goal is a plan that doesn’t take over your life. DISCLAIMER: this is only a very rough suggestion of a training plan. I recommend working with a coach to figure out what works best for you and keep your training productive and safe.
You should start your training at least 16 weeks out from a race, despite what an overly optimistic AI overview tells you. Especially for the more extreme distances, many people will go for up to 30 weeks of focused training, on top of already having several years’ worth of baseline fitness.
Weekly load
Aim for 4–6 sessions per week, with most sessions lasting 45–75 minutes. You should go for one longer weekend ride and keep running moderate, especially if you’re getting back into training after a marathon.
A simple weekly structure might look something like this, with the distance/time starting on the lower end and increasing as you progress in your training. You might also skip brick days at the start and only focus on one sport a day before you start stacking workouts.
- Mon: Rest day
- Tue: Bike (easy to moderate) + short easy run (10–20 min)
- Wed: Swim (with drills)
- Thu: Bike (steady) or short bike intervals (controlled)
- Fri: Rest day or strength training
- Sat: Long ride (build time) + short brick run (10–25 min)
- Sun: Easy run (30–60 min) plus low-stress swim
To help you succeed, add time on the bike first, start swim technique early, and keep run intensity under control.
Swim: the fastest way to improve is technique
Many people are just okay swimmers. Yes, you can be good at swimming in the ocean during a holiday or you’ve done swimming as cross-training, but chances are, what’ll be slowing you down is technique. I knew I was an okay open-water swimmer who could stay in the water for an hour without any issue, but I still decided to take an adult swim class to improve my technique. I recommend you do the same, but for starters, focus on:
- Relaxed exhale underwater. The body will panic if you hold your breath too much.
- Long body position. Try to float rather than beat the water into submission.
- Smooth, controlled strokes. It might feel slow at first but will make you faster and save energy.
- Bilateral breathing (every three strokes) is optional, but helpful long-term.
Again, if you can take a few lessons or join a masters/tri swim group, you’ll improve way faster than grinding alone. Also, your goal for race one should be calm + steady, not fast.
Bike: build comfort and endurance before speed
Start with easy rides focused on time in saddle and find your comfortable cadence. Become a good friend with your gears—don’t grind heavy gears nonstop. You should keep the same cadence on a lower gear rather than push through a higher gear and let your legs lose momentum.
Do one longer ride weekly and practice fueling on it. There are also other basic skills to improve in:
- Cornering and braking smoothly.
- Drinking and eating while riding. The ride will be your best option to stay on top of your nutrition.
- Riding in a straight line. You’d be surprised how many people actually weave when they ride a bike!
- Clipping in/out if you go clipless later
A note on “clipless” if you’re confused just as much as I was before; they’re not your normal, everyday bike pedals as it might sound. In the past, you used to have to clip into the front of the pedal using straps. Now, with modern shoes and pedals, you lock your shoes into a bolted-on cleat. If you think about it, you’re right, they aren’t really “clipless,” but the name stuck.
Run: you already know how to do it, now run smart off the bike
When training for a triathlon, you’ll need to shift your runner mindset a little. Focus on shorter, steadier runs and don’t stack hard run workouts on top of hard bike days.
You’ll be doing lots of what’s know as brick days. That’s when you stack two different sports on top of each other. When doing brick runs, start easy for 5–10 minutes, focus on quick cadence and small steps, and don’t chase pace, chase rhythm.
If you’re coming straight off a marathon build, tri training is a great way to maintain fitness while cutting impact.
Race-day flow for your first triathlon
- Pick up your race packet (often day before)
- Arrive at the start early, set up transitions
- Put on your markings
- Warm up and line up
- Start your race, often in waves or rolling start
- Swim, T1, bike, T2, run, finish, celebrate
Transitions
Transitions will likely be a brand new thing for you, unless you’ve done an ultramarathon with drop bags. However, they are an integral part of any triathlon and it pays to have practiced at least a little bit. It’s actually pretty easy to lose a lot of time during a transition!
Finish the bike feeling like you could have gone harder. You’ll thank yourself on the run.
Fueling
On the bike, have small, frequent carbs + water/electrolytes. During T2 before the run, have a quick sip and maybe a gel if that’s your normal. The bike portion of a tri is your best chance to stay on top of your nutrition plan.
Common first-tri mistakes marathoners make
1. Overrunning, under-biking, under-swimming
Triathlons reward balance. There’s a chance you’ll feel like you’re not running enough. Trust the process and don’t overdo it. Fun fact: when training for my first hundred miler, my coach had me on a more triathlon-like training plan than an ultramarathon one. I didn’t run nearly as much as I thought I had to. And yet I ran my hundred miler. To reiterate: you don’t need to run nearly as much as you’ll think you do.
Going too hard on the bike because it feels easy
It’s scarily easy to overdo it on the bike without even realizing. You only find out half a mile into your run that you’ve… become the architect of your own undoing, to say it nicely. Especially during your first tri, take the bike easy!
Ignoring swim technique
You can’t “fitness” your way through poor form and panic. As we’ve established before, good technique on the swim will take you further (and faster) than aggressively flailing through the water.
Trying new gear on race day
Test your wetsuit, nutrition, pedals, shoes, and everything else well in advance, and not just once. Conditions change and you’ll want to know how your gear and body behave so you won’t be surprised on race day.
Underestimating recovery
Even though tri training is in theory easier on the legs, three sports still add lots of fatigue. Nutrition, recovery, and sleep will matter as much if not more than when training for a marathon. Skimp on recovery and you’ll get injured.
How to pick your first race
You might be a master at marathons but you’re a beginner at triathlons, and a little bit of humility will help you not only successfully complete but enjoy your first one. It’s not about the distance as much as it is about expectations and receiving advice.
For your first tri, I’d recommend you look for beginner-friendly events with clear course marking and solid safety support. Generous cutoffs and a flatter bike and run course might also be a good idea. A big one is local logistics so you’re not adding travel stress.
If swimming makes you nervous, try a pool triathlon or a calm-water lake instead of an ocean swim, or a well-organized open-water race with lots of support (kayaks, lifeguards, clear buoys).
Set a “first tri” goal like “finish feeling strong,” “don’t panic in the swim,” “make my transitions smooth,” or “enjoy the day.” This will help ensure your first tri won’t also be your last.
Your marathon was the base, triathlon is the upgrade
Let’s wrap things up. Your marathon training built the endurance foundation. Triathlon adds variety, protects your body with cross-training, and gives you a fresh challenge that doesn’t feel like rerunning the same training cycle.
Keep it low-pressure. Start with a sprint or Olympic, use minimal gear, follow a simple plan, and treat race one as fun practice. Now, book a couple swim sessions, and do one easy bike-to-run brick this week to see if triathlons migh be for you. Then pick a race date and enjoy!
Frequently Asked Questions
What is a triathlon and how does it differ from running a marathon?
A triathlon is a multi-sport race. It’s made up of three disciplines done back-to-back: swimming, biking, and running. It combines endurance from three sports in one event with continuous timing from start to finish.
Why is triathlon a good next challenge after a marathon?
Triathlon can help you get new motivation. You’ll learn new skills like swimming and cycling and help reduce impact stress on joints compared to high-mileage running. Training for a tri brings variety and less mental grind than another run-heavy marathon training cycle.
What triathlon distances are good for marathon runners?
Common tri distances include Sprint (shorter, beginner-friendly), Olympic (~1500m swim, 40k bike, 10k run), and Half Ironman or 70.3 (1.9k swim, 90k bike, 21.1k run). The Olympic distance is often recommended as the ‘real triathlon,’ and is good if you’re looking for a manageable challenge without overwhelming training.
Do I need expensive gear to participate in my first triathlon?
No, you don’t need expensive equipment. For your first triathlon, basic swim comfort, a safe bike with helmet, and willingness to learn transitions and pacing are sufficient. A tri suit is nice but not required.
What are T1 and T2?
T1 is short for “transition 1” and referst to the first change from swimming to biking. T2 is the second transition from biking to running. If you can efficiently manage these transitions, you’ll find more success in your tri!
How should I choose my first triathlon?
Choose based on your available training time, swim ability, injury history, and personal goals. If you want your first tri to be fun, starting with Sprint or Olympic distances is ideal. Be honest about your schedule and comfort level with swimming before you commit.