Training on unstable
surfaces owes most of its development to rehabilitation, where it originated. There are many unstable training surfaces
including physioballs, foam pads, inflated rubber disks, and Bosu’s. These surfaces are used on the training
floors of most gyms.
The idea behind
unstable training is that inconsistent motion stimulates sensory apparatus in
the muscles and joints leading to increased sensory input and increased muscle
activation. In addition, these movements
cause muscles on both sides of the joint to co-contract. Co-contraction occurs to some extent during
virtually all movement. When we significantly
increase co-contraction, the result is increased joint stability.
Increased co-contractions from unstable surface
training can be very useful in the treatment of ankle instability and lumbar
spine injury. However, when we use a concept originally developed
for rehabilitation, we need to carefully evaluate how and when to use this approach
in healthy or athletic populations.
For example, many
trainers have clients perform shoulder presses while sitting on a physioball or
standing on Bosu to increase core muscle activation. However, this does not produce the desired
result. Studies show that doing shoulder
presses on an unstable surface do NOT increase core muscle activation versus
the same exercise done on a stable bench.
The reason for this
result is that balanced vertical forces in alignment with the spine do not
increase core muscle activity – regardless of instability of the surface the
exercise is performed on! The use of
asymmetrical loading, such as doing a one-sided shoulder press, does increase
core activation. However, this is not
increased further by being on an unstable surface.
Horizontal limb
movements also increase core activation, but there is not a lot of evidence
that adding an unstable surface increases this benefit.
When it comes to low
back stabilization, research shows that exercises done on balls in a horizontal
position (face up or face down) does increase core muscle activity. Exercises like crunches, bridges, and push-ups
on an unstable surface will result in increased core activation.
Unstable Surface
Training does NOT work well for absolute strength and power!
When it comes to
absolute force production performing exercises such as bench press or squats on
an unstable surface is counterproductive as force production significantly
decreases when training on unstable surfaces.
When training for increased
strength and power, performing exercises on stable surfaces is a much better
choice.
This is also true for
sprint training because training on an unstable surface increases ground
contact time and decreases force production, inhibiting acceleration.
The other consideration when using unstable surfaces like a Bosu Ball is that
lifting mechanics are significantly altered.
Researchers have suggested that training on highly unstable surfaces can
actually increase the risk of knee injuries in certain populations! Not to mention the risk of injuries also
increases from hopping, jumping, and leaping on and off of unstable surfaces!
Training with Unstable
Devices vs Training on Unstable Surfaces
Training using
unstable loads like a sandbag has very different effects from training on an
unstable surface. In fact, unstable
load training has direct positive transfer to many activities of daily living
and sports because we are frequently called upon to move unstable loads
including:
Carrying shopping bags
Carrying children
Contact sports where
you are pushing, pulling and twisting against other people.
Unstable load training
with sandbags also results in increased stabilizer firing and muscle activation
that directly positively transfers to functional movement.
What role should unstable training play in developing
programming for apparently healthy and athletic populations who are not
injured?
Research suggests that
a combination of unstable and stable training will provide the best results. This brings up two more questions:
Which should come first: stable or
unstable?
What level of instability should be
used with each particular person?
The answer to the
first question is dictated by the rules of proper progression. The three primary phases of stabilization
training include:
·
“Static”
Stabilization (foundational) – meaning ability to stabilize in static postures
such as the plank.
·
“Dynamic” Stabilization (strength/endurance) –
ability to stabilize during dynamic exercises
·
“Ultra-Dynamic” Stabilization (power) –
ability to stabilize during explosive movements
Within each phase:
·
Start with bilateral (both arms or legs) strength development in stable environments because it is safer and will
increase strength more.
·
Next progress to
stable single limb challenges
·
Then progress
towards hopping and jumping skills in a stable environment
·
Then apply that
new strength and power to tasks involving postural control on unstable
surfaces such as push-ups, planks, and other stability ball exercises done with the body parallel to the floor.
When it comes to how
much instability to use with each person, the answer will depend on the goal of
the exercise and the ability of the individual.
Ideally you will use different
levels of instability according to the goal of the exercise and your ability
level. Working with a qualified trainer
is highly recommended to get the benefits of unstable training!
To learn a systematic approach to incorporating
unstable load training check out DVRT – Dynamic Variable Resistance Training
here: dvrtfitness.com