Overhead Squat Dysfunction – Arms Do Not Stay Vertically Overhead

Primary Plane- Transverse, Sagittal
During overhead squat motion, if the arms do not remain vertical while holding the dowel, then this is scored as a dysfunction. This KAMS system assesses if the shoulder, elbow, and wrist are in line in the transverse plane.

The ability to extend the arms overhead during the movement of the overhead squat is essential in maintaining an ideal center of mass of the weight over the body. Glenohumeral mobility, scapular stability, and thoracic mobility are key in this assessment. When the arms do not reach vertically overhead, this places the body in an anterior chain muscle recruitment strategy and compensations tend to occur in the upper, mid and lower body. Thoracic mobility is often the key factor that restricts the arms from reaching vertical. Extension of the thoracic spine allows for extension and external rotation clearance of the glenohumeral joint.

Corrective Strategies
Lengthen the anterior shoulder flexors, such as the pectoralis major/minor, anterior deltoid, bicep.
Lengthen shoulder internal rotators such as the latissimus dorsi, teres major, subscapularis.
Lengthen scapular elevators such as the upper trapezius, levator scapulae.
Strengthen the scapular retractors such as the low/mid trapezius, serratus anterior.
Mobilize the thoracic spine in extension (sagittal plane)Strengthen the shoulder girdle external rotators such as the teres minor, posterior deltoid, infraspinatus.


Non-contact ACL injuries are becoming more and more prevalent in sport, especially in these sports that involve pivoting and jumping. Research indicates that most ACL injuries are non-contact based and are often caused by stability imbalance from left to right leg, flexibility imbalance from left to right leg, and by “over-dominance” of the quadriceps muscles (Andrews et. al 1996; Hewett et. al 2002).

Coordination and trunk control are also factors that can lead to an increase in the risk of ACL injury, as the shifting one’s center of mass can influence the torque of the knee (Myer, 2008). It is the compensatory strategies on the entire body at the point of foot strike or foot landing that affect the torsional forces of the knee and predispose ligamentous structures, such as the ACL, to be at risk of injury.

The ability to stabilize the core, and specifically the femur, through glute stability prevents the common “medial knee collapse” and “anterior patellar shear” that are risk factors for ACL injuries. When hamstrings do not properly activate and there is an overactivation of the quadriceps muscles (anterior chain) there is an increased anterior translation force at the tibiofemoral joint. Proper hamstring activation reduces the anterior translation force of the tibia on the femur, and thus reduces the force placed on the ACL. Glute stability also aids in reducing medial femoral rotation and subsequent valgus collapse at the knee joint. When the glutes and hamstring are strong and are activating properly, the posterior chain can eccentrically contract and load the force without anterior patellar shear and additional stress on the ACL.

NOTE: Females have a much higher incidence of ACL injuries as compared to men.

Single-Leg Vertical Jump Biomechanics and Injury Prevention – CLINICAL SIGNIFICANCE

Single-Leg Vert Jump

Biomechanics and Injury Prevention

Jumping and landing mechanics play a significant role in injury prevention in sport. The forces produced by jumping and landing have been associated with a number of injuries, such as patellar tendon pathologies, ankle ligament sprains, and ACL tears, if proper mechanics are not demonstrated (Shimokochi and Shultz, 2008). Studies have shown that athletes expose their bodies to ground reaction forces that are 5-7 times their body weight when they are landing from a vertical jump (Dufek and Bates, 1990). Most athletes are able to perform repetitive jumping without any complications, however if they lack proper technique or present with a musculoskeletal misalignment they significantly increase their risk of injury (Steele, 1990). Such dysfunctions, such as medial collapse of the knee, internal rotation of the hip, and a dropping of one side of the pelvis, are compensations worth exploring as potential risk factors and are signs of weakness in the kinetic chain (Joyce and Lewindon, 2016).

With research showing an importance of less than a 10-15% asymmetry from left to right when single leg jumping to prevent injury, it is equally important that the body is able to disperse and attenuate the ground reaction forces to prevent such injuries as ligament ruptures, bone bruises, cartilage damage, and meniscus injuries when single leg landing (Yeow, Lee and Goh, 2011).

A study conducted by Yeow et. al determined which joints dissipate the most force when single-leg landing and results concluded that the hip and ankle were the major energy dissipators in the sagittal plane, whereas in the frontal plane the knee was the main energy dissipator upon landing (Yeow, Lee, and Goh, 2011). When landing, the lower body should act as a shock absorbing spring to transfer the ground reaction forces up through the kinetic chain in a controlled manner to avoid overloading any particular area or structure in the body. Typically, if an individual has range of motion deficiencies, the landing portion of the single leg vertical leap will appear as “stiff”, which increases the amount of load the body will have to withstand. Therefore, it is important that the individual bends their ankles, knees, and hips during any landing task to avoid a stiff landing.

Several studies have shown the importance of active flexion of the lower limb in order to absorb the energy from the ground reaction forces (Podraza and White, 2010). When this flexion occurs, it places muscles such as the quadriceps in an ideal loading position, which reduces the forces transmitted up through the kinetic chain (Podraza and White, 2010).

When landing, the motor control system is able to anticipate and recruits necessary muscles required for landing before hitting the ground as a way to dissipate the forces through the lower limb (Whitting et al., 2009). Ideally, during the landing phase of a vertical leap, the hamstrings will activate before the quads, as a way to counterbalance the pull from the quadriceps muscles, which avoids anterior tibial translation, therefore protecting from ACL injury (Steele and Brown, 1999).

A study conducted by Pollard et al. found that female soccer players that show low flexion in the lower extremities during landing, also show increased frontal plane loading at the knee, which places them at greater risk of knee injury (Pollard et al., 2006). This lack of flexion is thought to leave the individual with using passive mechanisms to withstand the force putting structures in the knee at increased risk of injury (Pollard et al., 2006). However, excessive lower limb flexion has also been shown to increase stress on the patellar tendon potentially leading to patellar tendinopathy (Bisseling et al., 2008).

Single-Leg Vert Jump and Performance – CLINICAL SIGNIFICANCE

Single-Leg Vert Jump

Single-Leg Vert Jump and Performance

The Vertical Leap assessment will reveal the power capabilities of the individual, while also challenging their ability to incorporate coordination, motor control, and balance. The single leg vertical leap test is often used in sports performance assessments, as well as in return to play protocols. This particular type of jump is called a “countermovement jump”, which requires the individual to quickly lower themselves into the desired position, without any pause at the bottom, and driving through the ground vertically to maximize their recorded height (Liebenson, 2014). This test is unique in the way that it allows for us to recognize any asymmetries in an individual’s performance from left to right. Research has found that < 10-15% difference between sides should be present to reduce the risk of injury and also before returning to play after an injury (IMPELLIZZERI et al., 2007) (Wilk et al., 1994).

Jump and hopping assessments have been used for years in both sports performance evaluations, to determine power output, and return to play protocols. The vertical leap requires balance, motor control, and synchrony between mobility and stability.  Jumping is a movement that is required in many sports, such as track-and-field, volleyball, basketball, and diving, to name a few. The particular vertical leap we are using in this assessment is called a single leg countermovement jump. This requires the individual to quickly bend the knees and descend to the desired position and then accelerate upward. This movement requires the utilization of the strength-shortening cycle (SSC) (Liebenson, 2014). As the individual goes through the movement, eccentric muscle shortening occurs and stores elastic energy that is then released upon concentric muscle contraction. Studies have shown a significant correlation between vertical leap capabilities and athletic performance in sprinting (Marques et al., 2011).

The thought behind the strong relationship between the vertical leap and sprinting is due to both movements requiring activation of the SSC (Liebenson, 2014). Additionally, the NFL has been using the vertical jump test along with the 40-yard dash, 225lb bench test, broad jump, pro agility shuttle, and 3-cone drill to assess their athletes in the combine. A study found a statistically significant correlation showing increased vertical jump performance with those who were drafted vs those who were not in the NFL (Sierer et al., 2008).

Single Leg Vert Jump – Using the Kinetisense System for the Analysis of the Single Leg Vert Jump Test

Single-Leg Vert Jump

Using the Kinetisense System for the Analysis of the Single Leg Vert Jump Test

Using the Kinetisense System for the Single Leg Vertical Jump:

  1. Instruct the patient/client to stand at a shoulder width stance in line with the Kinect camera.
  2. Click “start” with the patient/client standing straight facing the camera.
  3. Instruct the patient/client to jump on the indicated foot (noted at the bottom left of the screen) as high as they can.
  4. Click “save” at the bottom right of the screen.

The system will automatically move on to the next foot when the first assessment is saved. Repeat the above instructions for the next assessment.

Single-Leg Vert jump – Overview

Single-Leg Vert Jump


The KAMS single leg vertical jump test analyzes the power of lower extremities and compares the power of the dominant leg to the non-dominant leg.

There are very few sports that incorporate a strict 2 leg vertical leap, yet this test is often used in many performance evaluations. Movements such as running, skating, or even doing a basketball layup are predominantly performed on 1 leg.

This test will reveal asymmetries in power from right to left and give insight into compensatory patterns of the entire neuromusculoskeletal chain that are recruited to make up for these asymmetries.

Balance and Performance – CLINICAL SIGNIFICANCE

Single Leg Balance



From a performance standpoint, vestibular balance is a key assessment in regards to functional movement. Balance and its associated patterns of movement give insight to the core pelvic and trunk stability, as well as strategies that are employed to establish or maintain a centrated COM (center of mass).  The pelvis is the keystone for the entire body, with many of the myofascial slings passing through this area of the body. Poor balance is often an indicator of the lack of stability and strength of the posterior chain, specifically the gluteus medius, gluteus maximus, hamstrings, gastrocs and soleus muscles.

The vestibular system is of great importance for the ability to coordinate both basic and advanced movements.  The vestibular system provides important information to the central nervous system of the spatial positioning of the body.  The proper integration of vestibular and visual afferent input provides the foundational information that is required for the efferent activation of the core and non-core muscles.  

Performance in a sport often requires stability, mobility, explosive strength, coordination, and speed.  The ability to process the spacial information of the body in its respective environment is required to that these other efferent processes can occur, based on the respective demand of the sport at the specific time of demand.

The vestibular system can and should be trained through balance and proprioceptive training and is foundational to performance.  Balance is foundational to functional movement and performance.


Single Leg Balance



The single leg balance test assesses multiple aspects of the patient’s/client’s functional abilities. Approximately 85% of the normal gait cycle involves the standing on one leg (Liebenson and Yeomans, 2007). This test will challenge the motor control and balance of the client. The client’s kinesthetic awareness will be tested as they attempt to maintain balance and coordination with their eyes closed. This test particularly has strong implications for the elderly population, as proprioception, balance, and coordination typically diminish with age.

A single leg balance (eyes open) test that is less than 30 seconds has been shown to increase the risk of falling, whereas greater than 30 seconds has been shown to decrease the risk of a fall (Hurvitz). Aside from activities of daily living, clients should have adequate body awareness and motor control to reduce their risk of injury while training or competing. The Kinetisense software will demonstrate any pelvic shift or loss of motor control.

Research has found that patients that report SI joint pain during a single leg stance had delayed firing of muscles on the symptomatic side, specifically the internal obliques, multifidi, and gluteus maximus, while the biceps femoris was found to be activated much sooner (Hungerford, Gilleard and Hodges, 2003). EMG testing revealed that the muscle firing patterns on the symptomatic side differed significantly from the asymptomatic side. It was found that the delayed firing of the multifidi and internal obliques decreased their ability to serve as stabilizing muscles at the lumbopelvic region (Hungerford, Gilleard and Hodges, 2003). It was also found that the early activation of the biceps femoris may be present due to a compensation for a delay in the firing of the gluteus maximus, which is responsible for extension at the hip and force closure of the SI joint via the sacrotuberous ligament and thoracolumbar fascia (Hungerford, Gilleard and Hodges, 2003; see Page, Frank and Lardner, 2010).

Research has shown that poor balance may be associated with low back pain. The study looked at the excessive movement of anterior and posterior sway during a single leg balance test and correlated this to the presence of low back pain (Byl and Sinnot, 1991). A similar study also noted that a deficit in balance abilities is correlated to an increased risk of developing low back pain (Takala and Viikari-Juntura, 2000).

Single Leg Balance – Overview

Single Leg Balance


The combination and integration of afferent and efferent neuro-proprioception of the vestibular systems (balance eyes closed).

  1. Frontal plane ankle and knee stability.
  2. Frontal plane lumbar/pelvic/hip stability.
  3. Frontal plane mid and upper trunk stability
  4. Frontal plane shoulder and neck stability
  5. Transverse plane ankle and knee stability
  6. Transverse plane lumbar/pelvic/hip stability
  7. Transverse plane mid and upper trunk stability
  8. Transverse plane shoulder and neck stability
  9. The single leg balance test has implications for the following:
  10. Fall Risk
  11. Foot pain (plantar fascitis)
  12. Ankle pain
  13. Ankle instability
  14. Knee pain and instability
  15. Hip pain and instability
  16. Low back pain
  17. Trunk weakness
  18. Gait

Reverse Lunge Dysfunction – Ankle Hyperpronation (L and/or R)

Reverse Lunge

Reverse Lunge Dysfunction

Ankle Hyperpronation (L and/or R)

Primary Plane – Transverse, Coronal (Frontal)
During the assessment, if the patient/client’s ankle of the stationary (non-sliding) foot collapses into hyperpronation, then this is scored as a dysfunction.


Athletes that lack proper proprioception and stability in the ankle will often collapse in on the arch and cause abnormal valgus forces on the medial structures of the ankle. This not only increases the likelihood of ankle and foot injury, but also increases the likelihood of knee, hip, and low back injury.
The inline lunge is predominantly a sagittal plane movement and lack of mobility of the knee and hip in this plane can predispose the ankle of the stationary leg to collapse into hyperpronation.
The lack of iliofemoral stability in the coronal plane can cause internal rotation of the femur and create a medial collapse of the knee (knee valgus) with ankle hyperpronation.

Corrective Strategies

  1. Strengthen the tibialis anterior.
  2. Strengthen the plantar arch (medial longitudinal arch, lateral longitudinal arch, transverse arch).
  3. Strengthen the glute complex (glute max, glute medius). 
  4. Mobilize external rotation at the talocrural joint.
  5. Mobilize external rotation at the iliofemoral joint.
  6. Lengthen the hip adductors.