Stability balls are commonly used in sports performance training programs. However, research shows that stability ball training is limited in its ability to truly enhance athletic performance for a variety of reasons (Willardson, 2007). It is important for personal trainers and coaches who work with athletes to understand the limitations of this training tool and adopt more effective ways to introduce instability into their athletic programs, including free weight training and structural multi-joint exercises.
Can Stability Ball Training Enhance Sports Performance?
A handful of studies have examined the effect of stability ball training on sports performance and found it lacking in several critical areas, as shown below.
Many trainers believe that strengthening the core enhances performance and decreases the risk of injury (Sato & Mokha, 2008). Core strengthening programs often include stability balls because of the belief that the unstable training surface will increase recruitment of stabilizers and trunk muscles (Anderson & Behm, 2004). Researchers testing these theories found that stability ball training improved core stability in swimmers, but did not improve swim times (Schibek, Guskiewicz, Prentice, Mays & Davis, 2001). A similar result was found in runners: stability ball training improved core stability but did not enhance running performance or running posture (Stanton et al., 2004).
The value of unstable training for limb muscle is uncertain (Koshida et al., 2008). A recognized limitation when strength training under unstable conditions (for example, training on a stability ball) is decreased force-generating capabilities (Nuzzo, McCaulley, Cormie, Cavill & McBride, 2008). This occurs because limb muscles assist in joint stability (Anderson et al., 2004).
Isometric force output during unstable strength training is significantly lower than during stable conditions. Because of this, some recommend that resistance training only be performed under stable conditions when the goal is to improve strength and athletic performance. An intensity level of 80% of maximum is required to result in strength gains, and this level of intensity cannot be achieved under unstable conditions (Koshida et al., 2008). In healthy subjects, the stimulus provided when strength training on stability ball training is too low in intensity to increase muscular strength and so does not seem to provide a training advantage.
Squats and deadlifts performed during stable conditions at intensities as low as 50% of 1RM demonstrated to be more challenging to the neuromuscular system than stability ball exercises. The reduced force-generation capabilities that occur during unstable training have led to the belief by some that instability training devices should only be used to supplement traditional training methods (Wahl & Behm, 2008). However, it has also been suggested that unstable training be “excluded” or “limited” because of the lack of evidence that such training improves strength or hypertrophy or improves athletic performance (McBride, 2008).
As with all types of training, specificity of training must be emphasized for optimal results when training to enhance athletic performance (Stanton et al., 2004). Exercising in a supine or prone position on the stability ball may not transfer well to sports performed primarily in standing positions (Willardson, 2007). Additionally, most athletes do not compete on an unstable surface. Instead, the instability is more often the result of interacting with an opponent (e.g. football, wrestling, soccer), or the need to place oneself in an unstable position, such as lunging to return a serve in tennis or to catch the ball in baseball. That being said, in some sports settings the use of a stability ball may increase the degree of specificity. For example, mogul skiing, shooting a puck in hockey, and surfing all involve generating forces in unstable conditions.
Thus, science does not support the popular opinion that stability ball training will enhance physical performance (Stanton et al., 2004). Because of the limitations in intensity and training specificity, some researchers suggest that sports performance might improve more readily with free weight training performed on a stable surface rather than exercising on a stability ball (Willardson, 2007).
So, What CAN Stability Ball Training Do For Athletes?
Research has shown the value of training performed on unstable surfaces for reducing the occurrence of ACL injuries (Willardson, 2007). This type of training may heighten the sensitivity of muscle spindles, resulting in a higher state of readiness to respond to perturbing forces applied to a joint. Exposing a joint to forces that are potentially destabilizing in training may be a necessary stimulus to encourage the development of effective neuromuscular compensatory patterns.
Heart Rate Response and Oxygen Consumption.
Heart rate response and oxygen consumption rates increase with stability ball training (Jakubek, 2007). As a result, sports that have an endurance component may benefit from supplementing traditional training with stability ball training.
Some Alternative Ways to Incorporate Instability into Training
Various degrees of instability are present in most, if not all, athletic activities: a wrestler trying to prevent himself from being thrown to the mat, a running back trying to break a tackle in football, a basketball player driving the lane to the basket, and a softball athlete lunging to make a catch all encounter instability in their chosen sports. Based on the concept of training specificity, introducing instability into your athletes’ training programs will better prepare them for the demands of competition. Presented below are suggestions on how to effectively introduce instability into the training programs of athletes you work with.
Free Weight Training
Instability can be influenced by both the base of support (such as a stability ball) and by the training method used. Training with free weights has been suggested to be more beneficial than training with machines for athletes due in part to the instability it offers (Anderson et al, 2004; Willardson, 2007) and this instability can be emphasized further with the use of water-filled implements because of the active fluid resistance that water provides (Hedrick, 2003).
Another way to emphasize instability in free weight training is to make frequent use of unilateral over bilateral dumbbell training. Many activities in daily life and in sport are unilateral in nature. Unilateral exercises provide a higher degree of movement specificity than bilateral training and better stimulate the trunk stabilizers (Behm et al., 2005).
Additionally, resistance training exercises can be adjusted to place additional emphasis on core stability (for example: squats and deadlifts performed with dumbbells while standing on one leg; power cleans and push presses performed unilaterally with dumbbells; trunk rotation exercises performed with cables or medicine balls).
Emphasis on Structural Multi-joint Exercises
Instead of focusing only on stability ball training, personal trainers may want to emphasize structural multi-joint exercises such as cleans, squats and deadlifts because training intensity can be continually increased by adding resistance to the training load. Another benefit of standing multi-joint exercises is that they recruit the core musculature more effectively than do stability ball exercises in a standing, functional position and movement pattern. Further, because multi-joint exercises recruit multiple major muscle groups simultaneously, they should be more time-efficient than performing multiple stability ball exercises (Nuzzo et al., 2008.).
While stability ball training does provides some limited benefits in athletic training programs — including improved core strength for injury prevention and enhanced heart rate response and oxygen consumption — it should only serve as a supplement to more effective training protocols. Athletes need to be able to generate force and train specifically for the sport they perform, and stability balls generally do not meet those needs. Standing free weight exercises better recruit the core and provide a higher level of sport specificity than do stability ball exercises, and are an excellent way to incorporate instability into a coach or personal trainer’s program design.
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