Backstroke is a full-body exercise that recruits muscles from your shoulders to your ankles, with the heaviest work falling on your lats, chest, and triceps during the pull and your quads and glutes during the kick. Because you swim face-up with your arms rotating behind you, backstroke places unique demands on the upper back and posterior chain that other strokes don’t match.
Upper Body: The Pull Phase
Your arms do the bulk of the propulsion work in backstroke, and two muscle groups carry most of that load. Your latissimus dorsi (the broad muscles spanning your mid and lower back) and your pectorals (chest muscles) generate the force needed to push backward against the water. These are the largest, strongest muscles in your upper body, which is why they handle the heaviest part of each stroke cycle.
As your hand moves through the pull and approaches your hip, the triceps take over. They extend your elbow to finish the stroke and generate the hand speed you need to recover your arm cleanly over the surface. This makes backstroke particularly effective for building tricep strength compared to strokes where the arm stays underwater during recovery.
The reverse arm movement in backstroke also activates the deltoids (shoulders) more than freestyle does. Because your arm enters the water above your head and sweeps downward while you’re on your back, the shoulder muscles work through a wide range of motion in a direction most people rarely train on land. This is one reason swimmers and coaches often recommend backstroke for balancing out the forward-dominant patterns of freestyle.
Lower Body: The Flutter Kick
Backstroke uses a continuous flutter kick, and each direction of the kick targets different muscles. The up-kick, when your leg drives toward the surface, is powered by your hip flexors and quadriceps. This phase actually provides most of the propulsive force from your kick, so quad strength and endurance directly affect how fast you move.
The down-kick, when your leg pushes away from the surface, engages your hamstrings and glutes. While the down-kick contributes less raw propulsion, it plays a critical role in keeping your hips elevated near the waterline. If your hips sink, you create significantly more drag, which slows you down regardless of how strong your pull is. A balanced kick keeps your body in a streamlined position and reduces the resistance you fight with every stroke.
Core: The Engine Behind Everything
Your core muscles do double duty in backstroke. First, they stabilize your hips so your legs have a solid platform to kick from. Without a stable core, generating force through the kick is inefficient. U.S. Masters Swimming compares it to firing a cannon from a canoe: if the base is unstable, the power goes nowhere useful. Your rectus abdominis (the “six-pack” muscles) and obliques are constantly working to create that stability.
Second, your core drives body rotation. Backstroke isn’t flat on the water; your torso rolls side to side with each stroke to let your arms enter and exit efficiently. The internal and external obliques, along with the erector spinae (the muscles running along your spine) and smaller spinal stabilizers, coordinate this rotation while keeping your body position tight. These muscles are active on every single stroke cycle, which makes backstroke an excellent sustained core workout even though it doesn’t feel like a crunch or a plank.
How Backstroke Compares to Freestyle
Backstroke and freestyle share many of the same muscles, but the emphasis shifts. Freestyle tends to load the chest and the front of the shoulders more heavily, while backstroke recruits more from the lats, rear deltoids, and upper back. The reverse arm path in backstroke is essentially the opposite motion of freestyle’s pull, which is why alternating between the two strokes gives you more balanced upper-body development than either one alone.
For people who sit at a desk all day, this distinction matters. Freestyle reinforces the same forward-shoulder posture you already hold at a computer. Backstroke counteracts it by strengthening the muscles along your posterior chain, including the erector spinae, lats, and rear delts, that pull your shoulders back and support spinal alignment.
Calorie Burn and Training Intensity
Backstroke burns slightly fewer calories than freestyle but still qualifies as a solid workout. A 155-pound person burns roughly 223 calories per 30 minutes of moderate swimming, with that number jumping to around 372 calories at vigorous intensity. Freestyle comes in around 300 calories per 30 minutes, with backstroke and breaststroke close behind. The gap narrows as you swim harder, and for most recreational swimmers the difference is small enough that choosing the stroke you’ll actually sustain for a full session matters more than optimizing calorie burn per lap.
Muscles Worked at a Glance
- Lats and pecs: primary power for the underwater pull
- Triceps: finish the pull and drive arm recovery
- Deltoids: control arm entry and exit through a wide range of motion
- Quadriceps and hip flexors: power the up-kick, your main source of kick propulsion
- Glutes and hamstrings: drive the down-kick and keep hips near the surface
- Rectus abdominis and obliques: stabilize the hips and control body rotation
- Erector spinae and spinal stabilizers: maintain body position and support rotation
Because backstroke demands constant engagement from so many muscle groups at once, it works well as both a primary training stroke and a recovery stroke between harder freestyle sets. The supine position takes pressure off the neck and allows you to breathe freely, which means you can sustain effort longer and accumulate more total muscle engagement per session than you might in a stroke that requires breath timing.