I have been working in the fitness industry for nearly 20 years and I still try to attend as many workshops and fitness conferences as possible. While I do see some discrepancies in what we identify as “the core musculature,” I have yet to sit through a presentation that undermines the value or importance of our CORE. 

What is the core?

In general, we can define our “core” as the group of muscles used for spinal stability and mobility. The rectus abdominis and erector spinae are responsible for spinal flexion and extension, bending forwards and backwards. Our obliques assist with spinal rotation, twisting side to side, as well as lateral flexion, bending side to side. Abdominal compression, the action involved while coughing, blowing up balloons, or bracing to move a heavy object is attained through the use of our transverse abdominis. The multifidus muscle consists of fibrous clusters that fill the space between each vertebra and is responsible for spinal stability. Whether our goals are fitness related or perhaps just maintaining the mobility necessary for daily activities, training our core musculature to work in harmony is a must! 

Hydro-Inertia®

Hydro-Inertia®, one form of dynamic-fluid resistance, utilizes water-filled devices such as the Surge® and Kamagon® Ball to generate unstable forces that must be controlled by the user. Due to the water constantly shifting and attempting to disrupt repetitive movement patterns, training with the Surge® or Kamagon® Ball can create proprioceptive-rich environments. As the user favors one side, the water flows that direction, stimulating engagement to occur in opposition. Not only does this provide instant feedback so the body can begin to balance itself, but it also triggers core musculature activation.

Four for Your Core

Here are some of my favorite core exercises that can be performed with either the Surge® or Kamagon® Ball! 

1) Push (Up) and Pull

Begin in plank position. Perform a push-up, then pull the Kamagon® or Surge® across the body. Try to keep the water as still as possible. Option: Tap the equipment instead of pulling it under the body.

2) Russian Twist

Begin in a V-sit position. Feet can be on the floor or elevated. Holding the Kamagon® Ball or Surge® with two handles, rotate side to side, oscillating the water. Option: Add a halo around the head.

3) Bicycle

Begin supine, holding the Kamagon® Ball or Surge® with two handles above the chest. Then, bring alternate knees to chest, while extending the opposition leg. Options: Hold the equipment stationary over the chest and try to stabilize the water while the legs move, or move the equipment in opposition to the legs and oscillate the water.

4) Chop

Begin standing, holding the Kamagon® Ball or Surge® with two handles. Move the Kamagon® or Surge® diagonally across the body in a forceful chopping motion, trying to crash the water down and back up to the starting position.


Lucy Waite, MS, is a master trainer for Hedstrom Fitness, BOSU®, and Schwinn Indoor Cycling. She is an instructional associate professor of health and kinesiology at Texas A & M University in College Station, TX.