Right It: Imagine your spine as a fixed axis moving forward through the water. Keep your head down and roll your shoulders forward with each reach. "As your arm extends and you roll to that side, turn your head to sneak a breath," says Marsh.
Practice: The corkscrew
Swim three strokes of freestyle without breathing; then over-rotate your torso until you’re on your back. Take three backstrokes, and then roll back into freestyle. Alternate roll sides. Do 10 reps of 50m (10 x 50m), with 10 seconds of rest after each lap.
Mistake #2 You kick from the knees, disrupting your balance in the water and fatiguing your quadricep muscles.
Right It: Kick from the hips. Small, rhythmic flutters propel you more efficiently than large, flailing kicks, which disengage your powerful hips and upper thighs. Think of your legs as extensions of your core. Your knee should bend only slightly with each kick.
Practice: Fin sprints
Wearing foot fins, push off the wall on your back, with your arms stretched above your head and your biceps pressed against your ears. Do a 10 x 50m set, completing each 50-m swim and ensuing rest period in 1:30 intervals.
Mistake #3 You paddle with your hands instead of pulling yourself through the water using your forearms.
Right It: Anchor your hand, wrist, and forearm as you drive forward into the water. Imagine wrapping your forearm over a Swiss ball and pulling yourself over it, says Marsh. Prevent your elbow from dropping inward, which weakens the anchor and your pull power.
Practice: Closed-fist sets
Swim laps with your fists closed. A lack of grip forces you to anchor your forearms. Do a 4 x 50m set of only fist strokes; rest for 10 seconds after each 50-m lap. Then do a 6 x 50m set of full strokes on 1:30 intervals, focusing on pulling with your forearms.
Mistake #4 You treat your swim workout like a casual jog, doing longer sets at a medium pace.
Right It: Elite swimmers train by tackling "building sets," which begin slowly and end with all-out sprinting. They boost conditioning and help create fatigue-proof strokes. "Second place goes to the guy whose technique crumbles first," Marsh says.
Practice: Count strokes
Try matching your number of strokes on the first easy lap with the number in the final sprint lap. Do a 5 x 100m set on 3:00 intervals. The first 25m: long and easy. The second: Swim at 50 per cent effort. The third: 75 per cent. The final lap: 90 per cent.