Although there are similarities, underwater walking is very different from regular walking, especially when it comes to shock absorption, muscle activity and energy expenditure.
Every time you step, shock is transferred from the ground, through your feet, and up your legs. According to MayoClinic.com, repetitive stress on certain joints can cause orthopedic injuries like osteoarthritis. Osteoarthritis can cause pain and swelling in your joints, making walking on hard surfaces very painful.
The “International Journal of Aquatic Research and Education” published a 2010 study that showed that underwater treadmill walking significantly reduced pain in patients with osteoarthritis. Researchers believed that the reduction in pain was due to less shock in the patients joints due to the buoyancy of the water.
Muscle activity is much higher while walking on an underwater treadmill. Due to higher density, you have to work much harder to move through the water than air. Michael Johnson, 13-time Olympic and World Championship gold medalist, trains up-and-coming sprinters with underwater treadmills. Johnson enjoys underwater treadmills because they can give an intense workout due to extremely high muscle activity, while being easy on the athlete’s body. A 2005 study published in the journal “Gait and Posture” showed a very specific underwater walking method for strengthening supportive muscle. They found that walking backwards on an underwater treadmill significantly increase activity of the paraspinal muscles — lower back stabilizers — and the vastus medialis — a major knee stabilizer — compared to regular walking.
The “American Journal of Sports Medicine” conducted a study that showed that walking on a treadmill on waist-deep water can double your oxygen consumption compared to walking on a regular surface. Increased oxygen consumption causes your body work very hard and utilize energy stores. This means you will burn far more calories walking on an underwater treadmill than you will walking on a normal surface.