Stable to unstable is a training progression, which is commonly misunderstood.
The mistake many make with stability training is that many coaches forget stable to unstable is in fact a training progression.
Just as slow to fast , closed to open & low to high are.
This may be related to the speed of the movement, the external factors influencing the exercise (other players, external load etc) or the amount of repetitions completed.
Many of these training variable progressions are generally adhered to, however stability training seems to be one that isn't.
It's a common theme for trainers, physios, coaches to get players straight onto a bosu ball to do a single leg squat with kettle bells overhead whilst wearing a weight jacket…………...ok well not to that extreme but you get the picture!
Can my player stabilize themselves on a stable surface?
Many players that I have worked with find it hard to balance on one leg one a stable surface. This is without the addition of a bosu ball, wobble board or stability ball. Stability training on a stable surface would be sufficient for these players.
Will adding an unstable surface affect the form of the exercise?
Don't get me wrong I realize that squatting on a wobble board is going to be harder than on a stable surface so maintaining technique will be harder. However are your players able to carry out the given exercise correctly so it is able to have its intended effect?
For example, if a player performs a single leg deadlift on a stable surface with a neutral spine and correct hip angle, then a coach adds a bosu ball. Are they able to hit the same hip angle and load the hamstrings appropriately or are they just flexing the spine and performing a partial range squat??
Are there other ways of progressing the exercise that may be more appropriate?
Instead of adding an unstable surface to balance on the player may react better to other progressions being used first.
Getting the player to close their eyes or adding perturbation to the exercise are two ways of progressing an exercise. The addition of perturbation to stability exercises can relate to the unexpected nature of forces impacted on players during a game. The unconscious reaction of the player and the stabilizing muscles are tested, as they would be in a game situation.
Changing the speed of the exercise can also increase the difficulty. Increasing the speed of a single leg exercise with a focus on stability at the end of each movement may be more appropriate for players. The opposite also being true, if we slow the movement right down the stabilizer muscles have to be worked harder.
Am I adding this progression for the benefit of me or the player?
If a player struggles with balancing on one leg why would we add a bosu ball to make it harder?
Unfortunately this is a common sight. The selection of an exercise or choice of a training progression has to be of the benefit of the player not the coach. Many coaches are utilizing drills and exercises so they can film it and put it on social media rather than trying to progress the player. A single leg squat on a kettle bell with a weight jacket on whilst holding a barbell may get more 'likes' than a player completing a hop and hold or bodyweight single leg squat but what is more beneficial to the player and their performance on the pitch?!
Can we change the position of the player or change the centre of mass?
Taking a player from a wide stance split squat to narrow stance split squat will narrow the athlete's base of support and place more instability on the exercise. Possibly a more 'sport specific' option than squatting on a wobble board as the stresses are more aligned with what will be endured during a game. Adding lateral resistance through bands or cables can challenge players through multiple planes which again is game relevant.
There are times in a program that training on unstable surfaces can be extremely beneficial. The use and timing of that this is used comes down to the coaching eye and the art of coaching.
Don't fall into doing an exercise because it'll look good on social media, keep the results of the athlete the priority!