Properly challenging the core musculature through resistance and stability training techniques for adaptations related to sport performance is currently a topic of debate. To ascertain what methods could be considered optimal, one must first understand muscle action inherent to the core region of the body. The core does not simply refer to the abdominal musculature as many believe, but is actually a functional group of muscles that act on the spine and pelvis. The core of the human body constitutes all of the lumbopelvic musculature and is utilized to maintain proper body alignment and protect the spine. A few of the major muscle groups and functional connective tissues that are emphasized when enhancing core function include: the rectus abdominis, internal and external obliques, erector spinae which serve prime movement and phasic energy transfer and the diaphragm, thoracolumbar fascia, multifidus, transverse abdominis and pelvic floor which stabilize both static and dynamic action. These groups are further coupled with muscle actions of the hip including both flexors and extensors. When stability, range of motion, and/or balance in one (or any number) of these muscle groups becomes compromised, an individual may have reduced ability to efficiently transfer force through the trunk to the upper or lower extremities. Essentially, force capacity may be lost during movements utilizing the entire kinetic chain. Due to the need for ground reaction force transfer, energy loss along the kinetic chain presents a predominant challenge in optimizing the efficiency of the often complex movements demanded in competitive sports. For this reason core stabilization has been indicated as an important aspect of athletic conditioning.
There are a few differing training methods presented in modern literature that propose to challenge core stability, endurance, and strength; and consequently enhance sport performance. The primary methods are; utilizing isometric stabilization exercises, training on unstable surfaces, and utilizing resisted exercises that significantly engage the core musculature through complex, multi-joint movements with added dynamics such as asymmetrical loading or single limb instability/balance requirements.
The majority of the initial methods for functional core training made its appearance out of the rehabilitation sector. Isometric stabilization exercises such as planks and bridges were employed by health professionals such as physical therapists to enhance dynamic function for athletes and the general population alike. It has been repeatedly demonstrated in recent literature that isometric stabilization exercises and like rehab-based methods used to improve core stabilization are beneficial for reducing lower back pain and carrying out activities of daily living (ADLs) with greater ease. The basic issue with these types of exercises translating into improvements in sport performance is the movements don’t match. Stabilizing the pelvic and performing tasks of daily living are very controlled with instability meeting the basic requisites for locomotion. On the other hand those seen in competitive events are almost always multi-joint and complex in nature; performed at much faster velocities and require greater endurance and stability over broader ranges of motion. Based on these facts isometric holds have limited transfer into improvements of human performance.
Another large portion of core stability based training has been focused on utilizing various pieces of equipment to add greater instability to common movements such as a squat or shoulder press. Implements such as stability balls, stability disks, Bosu balls, trampolines, foam rollers, and balance boards are commonly utilized to add a balance or proprioceptive component to familiar exercises and their applicable variations. Utilization of stability balls and other similar modalities may provide additional benefits such as with the stability ball abdominal crunch where greater range of motion may be attained when compared to crunches from the floor. This being said, seated bilateral dumbbell press on the ball yields minimal core activation compared to sitting on a bench. Whereas in other seated or isolated exercises using the stability ball such as chest press on the ball demonstrate additional core activation. When closed kinetic chain exercises are examined where a modality of instability is used under the feet or hands, the ability to produce force is significantly reduced and much of the instability compensations may simply occur in the ankles or wrists. This again may not have optimal translation for enhancements in sport performance if it is the only method used. Ground-based sports generally do not present the same type of proprioceptive demand or force requirements from unstable surfaces. Being able to stand on a Bosu and perform bicep curls, does not necessarily indicate an individual will maintain adequate core stability or power to effectively perform a single leg jump with rotation and simultaneous overhead arm extension to successfully attain possession of the ball for a rebound during a competitive basketball game.
Recent literature supports these statements based on comparisons between (body resisted) isolated and isometric movements and loaded closed chain movements. Stability activities such as the side plank or superman exercises fail to exert the same core activation as compound lifts such as the deadlift and back squat exercises. The compound lifts actually allow greater activation of the core musculature than isolated (semi)statics. The activation of the core musculature is further challenged when the lifts combined ground reaction force with asymmetrical loading as seen in the suitcase (single arm) deadlift and sandbag squats (single shoulder loaded). Likewise it appears greater trunk activity is encouraged from side loading and rotational exercises rooted in the ground such as the diagonal low to high cable chop.
It appears that the majority of modern research points toward core strength and stability having an effect on sport performance, but the methods used to enhance it should attempt to replicate the movement patterns and force production demands seen in the actual sport. This can be done in whole or in part and should have consistency to movement planes and velocities. Although static stability training can improve techniques used for more dynamic training actions, it is the challenges to dynamic stability that seem to transfer optimally to sports performance. Complex movements utilizing the entire kinetic chain, such as a medicine ball reverse lunge with rotation into unilateral hip flexion with an overhead press, allow for the activation of core musculature while challenging similar proprioceptive and force transfer demands encountered on a traditional field or court. This general concept was recently reinforced in a number of research studies published in the Journal of Strength and Conditioning Research. In one study, researchers found that greater levels of core muscle strength correlated to faster running times in a 5000-m run. In another study, compound lifts using multiple muscle groups enhanced core stability to a greater degree than isolated isometric movements thought to focus solely on core musculature. Introductory core stability training can initially focus on isometric planks and bridges to develop baseline endurance, but it seems that subsequent training techniques should have a dynamic component to it for optimal applicability within the sports realm. The general concept to consider is that the body functions as a single unit during sport rather than segments. Even if the weakest links in the unit are being addressed; optimal adaptations will occur with replication of synchronized and dynamic body segment activation, once baseline isometric endurance is achieved.