I stumbled into a water fitness class once when I didn’t know the open-swim schedule at the gym (and actually came back the next day because it was a blast!) . I remember it being more of a workout than I had anticipated. It looks like a lot of jumping and playing with pool toys, but if done correctly, water fitness can be an intense form of exercise.
However, I do remember a little red flag going up during the barbell curls. And nothing against the instructor, because she was really fun and energetic, but she was giving the fitness class some incorrect information.
In this article, I want to draw some attention to the difference between dryland and water fitness exercises that resemble the same movement but actually work opposite muscle groups. Let’s take a look at the Tricep Extension.
Notice for the Dryland Tricep Extension with a traditional dumbell, the force of gravity is pulling the weight straight down (obviously). The direction of motion is shown as an arrow, and the direction of contraction is moving with the direction of motion and against the direction of the force caused by gravity.
This is known as a concentric contraction, when the direction of movement and the force produced by the muscle are aligned in the same direction causing a shortening of the muscle during contraction. I’ve highlighted the triceps in this picture to illustrate the muscles contracting during this exercise. Now let’s see what happens underwater with a floating barbell.
Underwater, notice how the force produced by the floating barbell is basically opposite to that force produced by the dryland weight. This is because the floating barbell floats (duh) and is causing a force aiming straight up to the surface of the water.
If you did the exact same movement as in the previous picture, the weight would not only be a lot easier to lift–the weight would be lifting itself and your arm would have to contract to slow it down. In fact, this is precisely what is happening with the underwater tricep extension movement. In this case the force produced by the ‘weight’ and the motion are in the same direction. And this time, the direction of motion and the direction of contraction are in opposite directions.
When this happens, your triceps aren’t even contracting (and if they are, it’s with very little force). Because the float weight is lifting itself to the surface, your biceps are contracting in the opposite direction while they are slowly getting longer. This is called an eccentric contraction, a contraction in the opposite direction of motion that causes the muscle to get longer while producing force.
Here’s another way to think about it: For this example the lead weight will still be a lead weight, but the floating barbell will be a balloon filled with helium. To lift the lead weight, you produce force upward in the direction of the motion (force up + movement up = concentric). To slowly lift the helium balloon, all you have to do is decrease the amount of force you are already using to hold the string (force down + movement up = eccentric).
In summary, whenever you are using floating weights in aquatic fitness classes, be aware of the direction of force produced by whatever it is you are holding. If it has a natural tendency to move upward, lifting it will not be the same as lifting a dumbell on land. Your tricep extensions may not be working your triceps at all!