Why Core Strength is so Important for Triathlon

They’re not just for looks, guys and gals. Your abdominal section, or better yet your entire core, is the proverbial backbone of triathlon’s three disciplines – excuse the confusing anatomical metaphor.

Many triathletes might assume strengthening their arms and legs will generate the most benefits since these are the extremities that directly impact your movement in the swim, bike, and run. However, putting all of your focus there would be a mistake.

The core may arguably be the most important muscle group to strengthen in triathlon. But why is core strength so essential for your progress as a successful triathlete? The short answer is posture and form.

Core Strength for your Swim
Swimming requires a stable trunk and streamlined position for the most efficient technique. Streamlining, as you may already know, more or less means “punching” as small a hole as possible through the water. This means you need to keep your body as straight as possible in order to fit through such a tiny fictional hole. And a well-aligned body demands good posture.

Effective posture comes from a strong core in both the upper and lower abs as well as the glutes. Triathletes with a weak core tend to fishtail with their hips and legs from side to side, which creates more drag. Paradoxically, the best swimmers have a relaxed and fluid arm and kick action while engaging a tight and strong core at the same time. While extremely difficult, this keeps you straight like a torpedo.

Additionally, you’ve probably heard that to swim efficiently you need to generate body roll by rotating your hips. Body roll, or swimming on your side, is what allows you to efficiently pull and kick for forward propulsion. Interestingly, most of your body rotation comes from the core muscles, particularly the obliques. So be sure to do those side plank land exercises!

Core Strength for your Bike

Posture is going to remain the theme here. Have you ever experienced back pain during a triathlon bike leg? Think about the way you sit at work. If you’re slouched, chances are your back is going to start hurting after a couple hours. An upright posture protects your lower back muscles and also advances your ability to breathe easier and take in more oxygen.

In the same vein of swimming, triathletes with a weak core are susceptible to a poor pelvic position on the saddle, which results in side-to-side movement. Have you ever seen a triathlete rocking from side-to-side as they pedal? This is bad form and is usually due, in part, to poor core strength.

Martin Evans, strength and conditioning coach at British Cycling, says it elegantly: “When you cycle, you need to be able to create force from your legs, and transfer that force through your trunk and through to your upper body.” This means if your core isn’t strong enough to handle the force transferred from your legs, then you’re going to tire quicker. When that happens, your cycling form begins to fall a part and that directly affects power transfer.

Core strength will allow you to handle the output generated by your legs so you can stay in the proper triathlon bike position for the entirety of the race. You’ll protect your back muscles, you’ll increase your oxygen intake, and you’ll stay efficient longer.

Core Strength for your Run

Not to sound like a broken record, but guess why core strength for your triathlon run is so important? You guessed it – for better posture and form.

When your foot hits the ground, a shockwave of force is sent up through your trunk and torso. For the triathlete, especially at this stage in the race, having a conditioned core will hold your torso and trunk upright and aligned for the best form. When our core is weak or tired, we tend to wobble in our hips and upper body and this deflects energy that should be geared back towards our legs.

Core strength is most important for the really long-distance triathlete preparing for IRONMAN. We all tire at the end of a marathon. And when your body fatigues, your posture and form begins to suffer. Not only does this slow you down, but it can also lead to all sorts of injuries.

A built-up core works to hold these fatiguing muscle groups together longer so you can continue running upright and with proper technique throughout the entirety of the triathlon race.


For the triathlete, a strong core goes a long way to ensure that your body posture, form, and technique are stable and controlled longer for each discipline of the race.


For those of you who have recognized the importance of a strong core, what are your favorite core strength training exercises?

JARED MILAM is a professional triathlete, TriDot coach, and member of the Tri4Him Pro Team. He has 16 years of competitive running experience and 11 years of competitive triathlon experience with a half Iron PR of 3:59 and a full Iron PR of 8:30. Coaching under the TriDot system since 2011, Jared loves working with aspiring triathletes of all ages and performance levels.

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