Swimmers spend a lot of time in the water, hauling up and down the pool, seeking improvement in the freshly chlorinated water.
They also spend a significant amount of time on dryland, whether that’s lifting weights, bounding and leaping with plyometrics, or with core training.
And lots of swimmers will do long planks, endless crunches, and leg raises stacked on leg raises because they know intuitively that on some level, core training can help them swim faster.
But does it, for real? Fortunately, some research gives us a strong indication of how this plays out.
Core Training Improves Swim Speed
Researchers took 20 national-level swimmers and split them into two groups. Over twelve weeks, one group did core training three times per week, while the other didn’t. All swimmers continued their swim training as normal.
The core training workouts were around 30 minutes long, and included core exercises that swimmers should be quite familiar with:
- Front plank
- Side plank
- Bird Dog
- Leg raises
- Overhead squat
The exercises were selected to maximize transfer in the pool. Hence the anti-movement core exercises like planks, side planks, and Bird dogs. Unilateral/asymmetrical movements were also included to better reflect the demands of freestyle swimming.
Few of the exercises revolved around trunk flexion, which better reflects the demands of swimming. Although crunches are great for the six-pack, swimmers don’t crunch their way up and down the pool.
Swimmers in the core group steadily increased the number of repetitions, sets, and resistance over the course of the twelve weeks.
So what happened at the tail end of the intervention?
The core training group improved 50m freestyle times by around 2% more than the swimmers who stuck to the swim-only training.
To put that into perspective, that’s roughly 0.60 seconds for the average swimmer in this study. In a 50 freestyle, six-tenths can feel like an eternity and can be the difference between making finals and watching them from the bleachers.
And the best part is that this was achieved without a single additional meter done in the pool or overhauling their swim training.
Core Endurance Also Improved
Swimmers could hold static core positions for longer at the end of the study. Probably not a big shock there—when you train something, you tend to improve it.
But core endurance is one of the sneaky-important metrics for swimmers because the trunk muscles are highly recruited when swimming.
From controlling undulation in butterfly to managing body roll in the long-axis strokes, the trunk muscles are constantly stiffening, stabilizing, and transferring force between the upper and lower body.
Example: a separate study by Puce et al. (2023) with swimmers measured muscle activity in a swim-to-exhaustion trial. The muscles hardest hit as swimmers swam into a proverbial wall of exhaustion?
Not the lats, pecs, traps or legs—the erector spinae, the muscles that keep the spine stable and long—showed the most fatigue of any muscle group.
As fatigue creeps up on us, the core becomes one of the first muscle groups that loses its ability to hold the line, making it harder to maintain technique, body position, and transfer force efficiently.
How the Core Supports Faster Swimming
One of the key takeaways from this study—and core training in general—is to remember that core training doesn’t magically make the arms and legs stronger in the water.
Instead, it helps you make better use of the strength you already have.
This distinction is important because it helps reframe what the benefits of core training are for swimmers:
Better force transfer
At its best, the trunk acts as a bridge between the upper and lower body. Every stroke begins with force generated by the arms and legs, but with a stable trunk, some of that force leaks away.
Along with faster swimming, the core-trained swimmers showed increased muscle activity in the obliques and lats. The trunk fired harder and transmitted more force to where it mattered.
Improves coordination
Swimming is a highly complex skill that requires your arms, trunk, and legs to work together. Clean timing and coordination make this much easier, and trunk is what organizes and coordinates all of this movement.
Protecting technique under fatigue
Fatigue comes for us all in the water, and a stable and strong trunk keeps it at bay for as long as possible. A well-trained core helps you keep your technique in place for longer, leading to faster, more efficient swimming.
And yes, faster swimming.
More studies have come out since the Weston et al. study that show the effects of core training on swim speed:
- Karpinksi et al. (2020) saw that a six-week core training intervention with national-level swimmers improved 50m freestyle performance.
- Khiyami et al. (2022) found significant improvements in 50 free time trial performance after six weeks of core training—the age group swimmers dropped a staggering ~1.4s after the intervention compared to the control group.
When swimmers use the right core training exercises and train intentionally, good things happen in the pool.
The Bottom Line
Core training isn’t about building a mid-section made of carved granite. It’s about building a trunk that can stabilize the body, transfer lots of force, and maintain technique when it matters.
Swimmers who train the core smartly had the chance to swim more efficiently, be more resilient under fatigue, and ultimately, crank out faster times on the clock.
The challenge isn’t deciding whether you should be doing core training.
It’s using the right exercises, progressing them in a way that makes sense, and fitting them into your swim training for maximal returns and performance.
