Mechanisms of Mobility

Enhancing mobility has become popularized amongst gyms and fitness enthusiasts. Prior to exercise, mobility exercises are emphasized to increase ankle, shoulder, and hip mobility. Though, the definition of mobility is contextual. Broadly defined, mobility is the ability to move or be moved freely and easily [1]. Mobility is usually just addressed at the joint level. Mobility of the joint is the ability of that joint to move actively through a range of motion. Whether exercises aimed at optimizing ankle mobility, shoulder mobility, or hip mobility, a combination of neuromuscular control and flexibility are required dynamically moving, stabilizing, and positioning the joint. 

Though, mobility is also important in just the general movement of the human body as a whole (ie. functional mobility). The Center for Disease Control (CDC) estimates that 40.4 million people in the United States have physical functioning difficulty which equates to approximately 16.3%. To put this further into perspective, 19.4 million (approximately 8%) adults are unable, or find it difficult, to walk a quarter mile [2]. This demonstrates that many individuals exhibit a lack of functional mobility [3,4]. In clinical populations, those who suffer from diseases like Parkinson’s or arthritis experience limited mobility as spastic tremors or joint pain and inflammation impairs gait (walking) [3,4]. Aging, injury, and autoimmune diseases like Multiple Sclerosis also negatively impact mobility at both the joint and whole body level making activities of daily living like walking and climbing stairs challenging… they have lost their ability to freely and easily move [5-7]. This broader outlook on mobility suggests that a lack of mobility or working on mobility may look different to each person.

It is important to note that joint mobility and muscle flexibility are two factors that significantly impact overall functional mobility. As previously mentioned, when referring to joint mobility, it is the ability of the joint to actively move through a range of motion. Meaning, it takes a coordination of some muscles contracting and others relaxing to move smoothly through a range of motion. This differs from passively moving through a range of motion which may be more so related to muscle flexibility, given that no structural limitation exists. Flexibility has been defined as the ability of a muscle to lengthen and allow joints to move through a range of motion [8]. Flexibility and mobility are often commonly used interchangeably. Though they are similar, their definitions are truly unique and different.  

At PowerDot, our wireless bluetooth technology is scientifically designed to optimize all facets of human performance, and that includes mobility. PowerDot provides users with the ability to utilize both Neuromuscular Electrical Stimulation (NMES) or Transcutaneous Electrical Nerve Stimulation (TENS) all in one device. PowerDot’s FDA approved device and technology is the most advanced in the area of human performance providing a safe and effective means for anyone, from clinical to athletic populations, to enhance all aspects of mobility. The NMES technology enhances musculoskeletal fitness to improve functional and joint mobility while the TENS technology nullifies pain, removing mobility limitations associated with chronic daily pain [9,10]. Muscle cells within the human body are adaptable and their performance may be further enhanced by implementing daily use of PowerDot.

Active Versus Passive Range of Motion and Joint Arthrokinematics

As previously mentioned, mobility requires neuromuscular control to actively move the joint through a range of motion. Flexibility, being the ability of the muscles to passively lengthen, impacts this range of motion. Thus, mobility requires an aspect of flexibility. So, emphasizing both passive and active range of motion is essential to enhancing mobility. 

Each joint has a passive and active range through which it may move. The passive ranges are met by an external force being applied, moving the joint through a range of motion. Meaning, the individual does not actively engage any muscles to move the joint. An example of this would be static stretching. When bending over and touching (or at least trying to touch) your toes, gravity and your upper body/trunk are providing the external force thus passively moving the joints further into trunk and hip flexion. 

Active ranges of motion are attainable through the application of internal muscular force stimulated by the nervous system (hence, neuromuscular control). Though, mobility takes into consideration an aspect of the muscles stretching over the joint. A key distinction from flexibility is that it also takes into account how far the joint moves within the joint capsule which brings us to osteokinematics and arthrokinematics. 

When discussing mobility, it is important to explore beyond the gross movements of the limbs (our boney movement) meaning beyond osteokinematics, defined as the gross movement that happens between two bones. The movement of the human skeleton takes place at the joints where two bones articulate or come together. And it is this articulation we aim to improve when working on joint mobility, meaning focus is emphasized on arthrokinematics. Arthrokinematics refers to the movement of joint surfaces. Upon further examination of the joints, we see that they articulate (come together) with a concave and convex side. Concave is like the cave, it is rounded inward and where the convex side (rounded surface) of another bone goes into.

Before getting into the concave and convex rule of joint movement, it is important to note that the angular movement of bones on the joint surfaces occur as a result of a combination of rolls, slides/glides, and spins [11]. Rolling, gliding, and spinning occur at the joints in human movement to help to keep the joint centered and in alignment. For instance, when the concave surface is fixed and the convex surface moves on it, like glenohumeral abduction (raising your arm out to your side), the rolling and gliding are in opposite directions. If the moving joint surface rolls but does not glide then there would be separation and impingement in some parts of the joint capsule [11]. When the concave surface moves on a fixed convex surface then the roll and glide will be in the same direction. This would be something like sitting down doing knee extension. Movement is happening at the tibia (shin) and so the glide and roll are in the same direction, again, to keep the joint centered. This would be different from a closed-chain exercise like the back squat as the femur is moving on a fixed tibia. So the convex side is moving on the concave tibia. The importance of understanding how movement is occurring within our joints specifically allows us to examine the joint movement and determine the mobility issue and address it aiming to improve articular mobility, strength, and neurologic control. 

Mobility Versus Flexibility

Mobility and flexibility are targeted differently so it is important to address each one. Before getting into mobility, let’s first discuss the areas in which flexibility may be improved as we now understand flexibility may be of importance for mobility. Two common and heavily researched areas, in regards to enhancing flexibility, are static stretching and resistance training. Static stretching is a common mode of stretching where someone holds a stretch for approximately 30 seconds. It is well supported in the literature that static stretching has numerous beneficial effects like increasing range of motion, decreasing injury, pain relief, and improved athletic performance [12-17]. Relatively new to the study of flexibility is the impact of resistance training. Until recently, it used to be thought that resistance training would make someone bulky and actually decrease flexibility and passive range of motion. Though, after 5-weeks of resistance training, both a world champion body builder and Olympian increased flexibility [18]. When comparing those who perform resistance training versus those that just do static stretching, no differences in flexibility were displayed, meaning both groups improved [19]. These findings reveal that resistance training with full range of motion exercises is as beneficial at increasing flexibility as static stretching alone and may be more beneficial in regards to mobility and dynamic stability of a joint through active ranges of motion [20]. 

Mobility at the joint may be enhanced by performing joint mobilization therapy as well as strengthening exercises to the muscles around the joint [21-23]. Joint mobilization therapy is when a clinical professional, like a physical therapist, works on the arthrokinematics of the joint causing a gliding, rolling, or spinning motion to the joint. Some individuals may utilize self-mobilization techniques with a band. This form of manual therapy has the potential to not only increase active range of motion but also increase strength [22-24]. Alongside joint mobilization therapy, to further optimize mobility, strength training has also demonstrated to increase active range of motion, thus contributing to improved mobility [21].

Let’s examine a practical example of hip mobility in dancers and how, though flexibility and mobility may be trained differently, mobility does require the ability of muscles to lengthen. It is evident that dancers are flexible, however, it is important that they actively move through a large range of motion as key dance movements require high degrees of hip flexion (forward), external rotation (backward), and abduction (to the side) [25]. Active range of motion has been identified as a better indicator of dancing performance than passive range of motion [26,27]. Though, weak hip flexors and increased parasympathetic nervous system activation (causing internal resistance in the agonist muscle) reduces active range of motion [25,28]. Thus, strengthening the hips flexors and stretching the antagonists (hip extensors) have been targets for achieving key positions in dancers [21]. So, it is evident that there is this neuromuscular control of both engaging and disengaging certain muscles to move through a greater range of motion, thus improving mobility.  

PowerDot Enhances Human Body and Joint Mobility


PowerDot harnesses the technology of both NMES and TENS all in one device operated by using an app on your phone. There are no wires or going back and forth between various devices. Utilizing bluetooth technology, the power to enhance human body and joint mobility is in the palm of your hands on an app on your phone, all with PowerDot. 


TENS and NMES are commonly used and prescribed to positively impact joint and human movement mobility. NMES training in those with joint pain (like from arthritis) not only increases muscular strength and size, but reduces pain, stiffness, and functional limitations which may contribute to further improving joint mobility by recruiting a large number of muscle fibers [29]. Stronger muscles may also help provide a mechanical solution by aligning the joints of the body, thus decreasing pain caused by improper joint alignment and movement [30]. Via muscular contractions, NMES facilitates faster neuromuscular stimulation and upregulates circulation decreasing viscous resistance which may enhance active range of motion and joint mobility. 


However, just using TENS has been shown to significantly reduce pain more so than exercise [9]. It is understandable that pain limits mobility, both functional and joint mobility, as pain prevents people from being active and moving their joints. TENS sends frequency signals and releases endorphins that reduces central neuron sensitization, decreasing pain associated with movement [10,31].


Given the positive physiological responses from NMES and TENS, it is clear that these modalities may further enhance human movement and joint performance by addressing mobility. Try PowerDot here for free for 30-days and take your mobility to the next level.




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