Training in an unstable environment is not a new concept.  It was originally utilized for many centuries by a variety of populations.  For example, martial artists trained in a variety of unstable environments to enhance their stability, balance, strength and power.  For example, training barefoot in the sand and walking on different types of wooden poles placed in the ground were some of the simple forms of unstable training environments.  The end result created athletic bodies with unbelievable power and strength which are characteristics all coaches try to develop in their athletes.  Scientific research shows the efficacy of unstable training environments.  As an example, a recent study was conducted and showed an increase in core muscle recruitment during an abdominal curl when it was performed in an unstable environment compared with a stable surface.  When Spindel Sports Academy employs a functional training program, we use unstable training environments to enhance performance through enhanced stability and balance.   Here are two traditional exercises that we modified to include unstable training environments. 

Notice the feet are balancing on an unstable surface.  This causes the lower extremities to work harder by recruiting more muscle fibers.

A traditional push up becomes more difficult due to the fact the legs are not supporting the body.  As a result, the abdominal muscles must "fire up" to help stabilize the lower and upper body.  More muscles are recruited in this unstable push up.