Balance is physical equilibrium or the ability to maintain stability produced by even distribution of weight on each side of a vertical axis. In humans, there are three factors that influence balance. These are:
Some authors argue that there is a fourth component that influences balance which is a psychological component: the fear of falling. For our purposes and for the athletic population, we will address only the three factors listed above. Of those factors, pathokinematics has the largest influence on the somatosensory system or proprioception. So prior to talking about the impact pathokinematics has on the somatosensory system or proprioception, we must first define proprioception.
Proprioception is the sense of the relative position of neighboring parts of the body, joint position and the strength of effort being employed during movement. This complex sense is provided by multiple systems (Neuroscience, 2nd edition, by Purves et al. 2001) including the inner ear (bony labyrinth) and sensory receptors in the joint capsule, in the musculotendinous junction (golgi tendon organ) and within the muscle (muscle spindle). Stimulation of these systems contributes to our sense of awareness of where our body is in space. Several factors that can negatively impact this input are injury, pain and/or abnormal movements (bad technique) performed over time. With regard to this last factor, we need to remember that poor movement patterns repeated over time result in repetitive stimulation of these systems in these altered positions. This, in a sense, “teaches” the fibers that this is the “correct movement or posture” when in fact, it is not.
The same is true with pathokinematics over time. The body becomes accustomed to moving in this way, and the athlete senses that this is normal movement---it “feels” right. Again, let’s use the example of the athlete above who squats with the obvious lateral shift. Because he has trained his body over the span of months to squat in this way (or he has allowed himself, knowingly or unknowingly, to squat in this way) his body perceives this as “normal.” When moved into a more anatomically correct movement pattern, he feels awkward, weak and perceives the positions and motions as abnormal. This is due in part to the proprioceptors in his lower extremity. They must be re-trained to sense this “new” position as correct relative to space.
So, let’s examine this concept in more depth as it relates to performance by looking at proprioception or balance in the core and hip (marked in red in the photograph). A decrease in proprioception and balance in the core and hip can lead to many performance limitations, and we see this especially in many of our female athletes. Such a deficiency in proprioception can present itself in the form of an inability of the athlete to disassociate lumbar spine motion from hip motion, as in the example of lumbopelvic disassociation. Also if one has weak hips, particularly in the stabilizing muscles of the hip such as the gluteus medius and other smaller and/or deeper stabilizers, (gluteus minimus, gemelli, obturators, tensor fasciae latae, quadratus femoris), we might expect to see a reduction in the ability of the athlete to balance, especially during single limb activities.
In an unpublished 2009 study, a group of examiners assessed 3 different movement screens commonly used in sports medicine and implemented these during collegiate and high school physicals over the span of 3 years. Subjects consisted of 600 male and female athletes ranging in age of 15 years old to 20 years old. One of screens used during this study was the Star Excursion Balance Test. One of the key movements being assessed during this test by examiners was posterior medial movement (shown above). This motion requires a significant amount of proprioception in the hip as well as gluteus medius strength in order to stabilize the knee in a closed kinetic chain situation like this one. Male athletes performed favorably on this movement with 80% of subjects able to perform the test to within 10 cm of the contralateral limb. Female athletes performed less favorably, with less than 55% of subjects able to perform the test to within 10 cm of the contralateral limb. Most examiners noted that females would first lose control at the hip and fall into a trendelenburg (versus pronating at the foot first) which would be followed by loss of control at the knee which would lead to the knee moving into a valgus position.
One of the questions one might ask at this point is whether or not it is the pathokinematics that lead to significant reductions in balance and lower extremity control over time or is it the reductions in balance and lower extremity control that lead to pathokinematics? Again, it is the question of the egg before the chicken or the chicken before the egg. Although we don’t know the answer to this question, we do know is that both present together in a majority of cases and if we improve proprioception, then we also see a corresponding improvement in pathokinematics. And, of course improved balance, body control and movement all lead to athletic performance improvement and reduction in injuries.
The last performance related area we would like to address that is directly affected by pathokinematics is reaction time. Before we discuss the impact of pathokinematics on reaction time, let’s review some basic concepts on reaction time. Reaction time, in the most simplistic terms, is a combination of:
Understanding the components of reaction time and the factors which positively or negatively impact reaction time gives us a better understanding of how pathokinematics can play a role in limiting performance by increasing reaction time. For example, if an athlete demonstrates significant pathokinematics resulting in altered length tension relationships, decreased efficiency of movement, poor proprioception, and decreased endurance, then one can easily see how reaction time would be negatively impacted. This is especially true and more evident in later phases of the game when an athlete’s pathokinematics may become more pronounced and the efficiency of the system becomes compromised to an even greater degree due to fatigue and other contributing factors.
In sports in which speed and explosive movements are important, reaction times are imperative to overall athletic performance. Improvement of factors that result in decreased efficiency throughout the system and the resulting efficient transfer of energy across that system, can and will result in the reduction of time from initiation of a given movement to full execution of that movement[viii]. By improving the strength and endurance of the entire kinetic chain, we can capture, conduct and channel all available power generated by the athlete more effectively and efficiently, and by improving this energy transfer, we thus improve performance.
Reaction time, like all of the other sports performance fundamentals discussed in this chapter, including pain and pain prevention, efficiency, energy conservation, endurance, power, speed, flexibility, balance and lower extremity control, has a direct correlation to pathokinematics. In addition, it’s important to note that each of these performance considerations is affected by the others. This results in a powerful compounding effect when any one or more is present. In other words, when pathokinematics lead to a deficit in any one of these or any other sports performance area, all other areas are affected as well.