Pool Swimming Builds Cardio and Shoulders, Without the Impact

Thirty minutes of freestyle keeps your aerobic engine running and puts your upper body to work while your legs take a break from the pounding, as long as you learn to breathe in the water first.

• What a pool session trains: aerobic fitness, shoulders and lats, core, with your legs freed from your body weight.
• Why a single length leaves beginners out of breath, and how to fix it standing in the shallow end.
• Just two pieces of equipment, a kickboard and a pull buoy, to split the work between legs and arms.
• Your first 30- to 40-minute session, length by length, with rests at the wall.
• Where it fits in a running week, and what the pool leaves out.

In the water, your body stops weighing on your legs. Your heart and lungs work for thirty minutes or more while your ankles and knees rest. For runners, that makes swimming the cross-training to keep in your back pocket for high-mileage weeks, when your legs are begging for a break and your lungs aren’t, or for easing back from a nagging ache. For almost every adult, the obstacle is the same: one length in, you reach the wall gasping.

What a Pool Session Trains

Your breathing works the way it does on a long, easy run, with one difference every runner notices right away: breathing gets its own slot. On the road you breathe whenever you want. In the pool you breathe when your stroke brings your mouth out of the water, and you learn to make that window enough. At first it’s the hardest part. Then it becomes a rhythm, like your footsteps.

The work your legs do on the road shifts to your arms here. In freestyle, most of the propulsion comes from the arm stroke: your hand enters in front of your shoulder, catches the water and pulls it back under your body to the level of your thigh. The pulling comes from your shoulders and above all your lats, the broad muscles along the sides of your back that barely work when you run.

The day after your first session, you’ll find them there, along your sides, just below your armpits.

With no floor to push against, your body stays in line only if your abs and glutes hold it taut from head to toe. Picture a wooden plank floating in the water: straight, it glides; bent in the middle, it drags and the back end sinks. Then there’s rotation. With every stroke your torso turns from one side to the other, driven by the muscles around your waist.

For runners, what’s missing matters too. With no ground contact there’s no impact: your legs move without ever taking the hit that lands with every stride on the road, a few thousand times per run. Your aerobic system trains while your tendons and joints recover. Of all the activities you can pair with running, swimming takes the most load off your legs and gives the most work to your upper body, and it’s worth learning even if your stroke starts out shaky.

Getting Started With Little Technique

Breathing comes before arms and legs. Getting winded after a single length almost always comes from holding your breath rather than from your fitness: you put your face in the water, instinctively lock everything up, and when you turn your head you have to blow out and suck in within the same half second. You get half a breath, even less on the next stroke, and by the end of the length you’re as short of air as after a sprint.

You learn the fix standing in the shallow end. Breathe in through your mouth, put your face in the water and let the air out slowly, through your nose and mouth together, for three or four seconds, like letting a balloon deflate while you pinch its neck between your fingers. The bubbles rising in front of your eyes tell you it’s working: when you come up, your lungs are already empty, and there’s only one thing left to do — breathe in. Swimming works the same way. Underwater you exhale; above water you only inhale.

To get air, your head rotates instead of lifting. Turn your face to the side along with the shoulder that’s pulling back, keep your ear resting against your extended arm and one eye underwater, and breathe in with your mouth just clear of the surface. At first, breathe every two strokes, always on the same side: that’s the rhythm that lets in the most air.

Hold the kickboard with your hands on the far edge and your arms straight: face in the water, legs kicking from the hip with knees slightly bent and toes pointed, and to breathe you turn your head to the side, resting your cheek on your arm, just as you will when swimming. The pull buoy, the figure-eight float, goes between your thighs and keeps your legs up and still, so only your arms work: each stroke enters in front of the shoulder, reaches forward, pushes the water back to your thigh and exits relaxed to swing forward again.

It’s worth spending most of your first session like this, in pieces. You’ll learn faster, and you’ll climb out of the pool without feeling like you’ve just been in a fight with the water.

Where It Fits in Your Running Week

Its natural place is the day after your long run: your legs are loaded, and half an hour of easy swimming gets your body moving without adding impact on top of yesterday’s. Or it can stand in for an easy run during a recovery week. Coming back from a minor injury, it works the same way, as long as moving in the water doesn’t flare it up: it keeps your aerobic fitness switched on while your return to running moves through its phases.

The limit of swimming is the flip side of its strength. Your leg bones and tendons adapt precisely to the hit of every footstrike, and in the water that hit is missing, along with the specific strength that drives your body off the ground. The pool supports your runs. It doesn’t replace them.