Weightlifting movements (WMs) such as the clean and jerk and snatch are believed to have performance enhancement benefits for a variety of athletes (14). In addition to these WMs, derivatives including the front squat, back squat, and overhead squat can provide an appropriate training stimulus for the athletic development in many athletes if performed properly (20,26). Unfortunately, the fear of injury while performing these WMs may deter some athletes from implementing them in a strength and conditioning program.
Although injuries can be common in sport and training (14), appropriate strengthening programs have been suggested as tools to decrease this injury risk (14,20). In the field of strength and conditioning, physical therapists, athletic trainers, strength coaches, and other health professionals are well suited to understand the demands WMs place on the body, and specifically, the joints. To date, there is a lack of succinct range of motion (ROM) detail provided in the literature that provides a full understanding of what ROM is needed at each joint to successfully perform these WMs. In addition, assessments that test for the ROM needed during these WMs are limited.
One way strength and conditioning specialists have attempted to gain a better understanding of movement and injury risk is through athlete assessments. Most of the assessments that exist evaluate strength, endurance, and global movement quality (42). By using standardized tools, strength and conditioning professionals who work with athletes at every level are better able to assess how an athlete moves with the goal of decreasing the potential for injury.
Despite what is currently described in the literature, to the authors' knowledge, no assessment exists that is geared specifically toward WM. Although USA Weightlifting recommends assessing flexibility with a front squat, overhead squat, snatch-grip deadlift, and a military press (11), there are few objective measures established that describe the ROM requirements specific to WMs. The lack of consistent measurement guidelines along with the lack of agreed on motion requirements, as well as the absence of a way to appropriately apply these guidelines across a large population, results in uncertainty for strength and conditioning professionals when deciding to return an injured athlete to WMs, or to effectively assess athletes before embarking on a WM program.
Therefore, the purpose of this article is to investigate WMs, including the associated biomechanics and forces at key joints, and describe the ROM requirements necessary to perform them safely. In addition, based on these motion demands, an assessment tool will be proposed to grossly evaluate the motions of each lift, then quickly and objectively determine whether an athlete's mobility is sufficient to begin WM or return an athlete to WM after injury.
As one of the most basic movements in athletics, the squat is not only an integral component of weightlifting, it is a functional movement required in daily activity (29,30). The squat allows an athlete to propel themselves vertically and horizontally through space and is an excellent tool for the athletic development (36,37). A deep squat, which is required in WMs, is one where the hip crease travels below the top of the knee (16,19). Figure 1 demonstrates the bottom position of a deep squat with focus on full mobility at the ankles, knees, and hips.
A properly functioning ankle joint with large amounts of dorsiflexion is essential for an appropriate deep squat (23,25). From a biomechanical perspective, the goal during a deep squat is to keep the tibia as vertical as possible to limit tibiofemoral shear (16,36). However, as weight is added to the squat, maintaining a vertical tibial position becomes more difficult and ankle dorsiflexion peaks (16).
If a deep squat is performed without adequate dorsiflexion, compensations including increased flexion at the hips, lumbar spine, and trunk can result (19). These compensations decrease the moment arm of the erector spinae muscles and increase intervertebral disc shear forces (19). This can lead to a calculated increase in compressive forces of 6–10 times body weight in the spine and may predispose an athlete to lumbar disc injury (6). An increase in spinal flexion angle can also result in a linear increase in both the compressive and shear forces on the lumbar bodies and intervertebral discs during a back squat from 3100 to 7340 N, with loads ranging from 0.8 to 1.6 times an athlete's body weight (6). This may increase the risk of disc dysfunction (6,19). Although it may not be obvious initially, these biomechanical issues demonstrate how a deep squat performed with limited dorsiflexion can increase the risk of potential injury.
Although we know that dorsiflexion motion is paramount in successfully performing a deep squat, a range associated with a weight-bearing measure is not agreed on in the literature. Further compounding the problem, there is no consensus at present regarding the best way to assess ankle dorsiflexion ROM for a deep squat (28). Open-chain goniometric measures are an option, but they are not representative of the demands placed on the joint in a loaded, functional position. However, the weight-bearing lunge test (WBLT) seems to replicate these demands well (28). To perform the test, an athlete stands facing the testing wall barefoot with the great toe of the testing foot 10 cm away from the wall (28). With the heel in contact with the ground, the athlete flexes forward at the knee in an attempt to make contact with the wall while avoiding a pronation strategy as described by Denegar and Miller, which can present as increased subtalar eversion, demonstrated by a drop in arch height, and/or midfoot abduction, demonstrated by increased toeing out (10,17). With a successful attempt, the athlete is progressed 1 cm further away from the wall, and the test is repeated. If unsuccessful, the athlete is progressed 1 cm closer to the wall. This process is continued until an athlete's maximum distance away from the wall is obtained. Figure 2 shows a side view of the WBLT with shoes removed to determine heel-off point.
The WBLT has many advantages. First, it is easy to perform, requiring minimal training and equipment (28). Next, it possesses face validity, as the weight-bearing position assumed closely resembles the ankle position during a deep squat. Furthermore, the test yields a highly reproducible measure and demonstrates good concurrent validity with goniometric and digital inclinometer measurements (28).
The WBLT demonstrates excellent interrater reliability and is highly reproducible with an intraclass correlation coefficient (ICC) of 0.96–0.99 (28). These values are compared with standard goniometric measures that have ICC values ranging from 0.62 to 0.99, and with digital inclinometer measures demonstrating ICC values of 0.89–0.98 (28). Finally, the WBLT seems to correlate well with other functional assessments such as the anterior reach distance as part of the Leg Motion system (4) and the Y-balance test (22).
In addition to the high reliability of the test, evidence links values from the WBLT with the functional mobility required to perform a deep squat. Work by Kasuyama et al. found that WBLT scores of 10.75 cm on the right and 11.25 cm on the left are specifically correlated with the ability to perform a deep squat in 71 healthy males (23). Therefore, to successfully perform a deep squat, we can expect that an athlete has approximately 10.75 cm when performing a WBLT.
THE SQUAT—KNEE AND HIP
Historically, deep squatting has been proposed to increase joint laxity, shear force, and compressive force at the knee (9,32). However, neither theory is supported by the current literature (16,19). The anterior translation at the tibiofemoral joint resulting in shear force, is actually believed to decrease as squat depth increases beyond 60° of knee flexion (13,37) because of the cocontraction of the quadriceps and hamstring musculature (17,36). This suggests that increased squat depth may decrease shear force at the knee, rather than increase it. Furthermore, the greatest anterior shear forces experienced during a squat at the anterior cruciate ligament (ACL) are seen during flexion of 0°–60° and are roughly 95 N (13). In comparison, normal gait activities place approximately 303 N of force on the ACL, which is far from reported failure values (38).
Finally, compressive forces at the tibiofemoral and patellofemoral joints are believed to increase with increasing squat depth (13,36). Despite increasing compressive forces at the tibiofemoral joint, conclusive evidence has not shown an increased degeneration of meniscal or chondral tissues as a result of deep squatting (19,36). At the patellofemoral joint, however, contact with the odd facet of the patella and the wrapping effect of the quadriceps tendon can enhance load distribution and result in decreased, rather than increased patellofemoral forces at angles greater than 90° (13,19). Because of this enhanced load distribution, peak patellofemoral compressive forces are actually experienced at 85° of knee flexion on descent (4548 N) and 95° of knee flexion on ascent (4042 N) during a loaded squat (13). Therefore, loaded squats >95° do not necessarily lead to increased compressive forces at the patellofemoral joint and actually may result in decreased compressive force at flexion angles greater than 90°. Table 1 shows compressive forces experienced by the tibiofemoral joint during a weighted squat. It compares these values at various joint angles and shows how force is distributed to the quadriceps and patellar tendons. Relative failure loads are also reported to compare each tissue tolerance with load. As these data suggest, the load associated with a deeper squat on the structures of the tibiofemoral joint is well within their respective tissue tolerance.
Similar to the knee, current literature does not support an association between a deep squat and hip injuries. A squat to parallel with an external load demonstrates hip joint torques of 28.2 N·m (16). These forces are expected to increase with depth, but these values are not believed to reach harmful levels at the joint (29,30). In addition, as greater squat depths are achieved, athletes with femoroacetabular impingement (FAI) are believed to reach close to their maximal ROM at the hip (29,30). Interestingly though, Lamontagne et al. suggest that patients with diagnosed FAI do not experience any difference in ROM in a deep squat preoperatively or postoperatively, compared with control groups (29,30). This may suggest that if injuries at the hip do occur during WMs, they are likely not related to bony morphology, but rather to the surrounding soft tissues and their potential to limit mobility at the hip (1,29,30). Regardless, although not directly related to injuries at the hip (25), decreased hip motion during a squat may lead to compensations and injuries previously discussed with respect to the low back (16).
Although hip mobility is often not the limiting factor during a deep squat, researchers have determined that deeper squats are correlated with greater hip flexion angles compared with squats of lesser depths (8). There is no consensus regarding the hip ROM required for a safe, deep squat. No test is presently used that measures both knee and hip joints simultaneously in the positions required during the performance of a deep squat. Current literature suggests that a deep squat requires greater than 135° of knee flexion (19,29) and 95°–116° of hip flexion (1,12). Passive knee flexion values of 120°–140° are reached with the approximation of the calf and the posterior thigh in supine (19), whereas passive hip flexion values of 137° have been reported during supine single knee to chest measures (41). Individually, each of these measures demonstrates sufficient passive motion to perform a deep squat; when combined, these measures resemble a single, easy to perform assessment, the supine knees-to-chest, holding shins test (SKTC) (7).
The SKTC is performed with the athlete in supine on a flat, immobile surface. The athlete is asked to bring both knees to their chest while pulling the shins toward the pelvis. To passively establish the ROM requirements described above, the thighs should approximate with the lower rib cage and the hamstrings with the calves as seen in Figure 3. If unsuccessful, the athlete changes the pull from the shins to the backs of the thighs. Figure 4 shows this as the athlete again tries to approximate the thighs to the lower rib cage screening only the hips. The ability to complete this second task but not the first, suggests adequate hip mobility but may point to limitations with knee flexion ROM.
THE JERK AND SNATCH—MOVEMENT
The jerk and snatch provide the development of muscle synchronization, coordination, power, speed, and strength (20,26) that can carry over into most sports. The jerk and snatch lifts require an athlete to move a load from either the shoulder or ground to an overhead position, respectively. The ROM requirements through the lower extremities to appropriately assume the catch position of a snatch, shown in Figure 5, are the same as those described previously for the squat, shown in Figure 1 (4).
In the overhead position of a jerk and snatch, the shoulder joint complex, thoracic spine, and wrist must function through large ranges of motion to limit potential injuries. Athletes who routinely perform overhead lifts average 202° of active shoulder flexion (3). This value seems to be above average, as a study by Barlow shows that in a population of resistance trained individuals, shoulder flexion averages 180° (2). These values both seem to be greater than average population flexion values and are much higher than other data referenced in the literature, as normative shoulder flexion ranges from 164° to 178° and wrist extension ranges from 68.5° to 78.4° (3,18,39). Conversely, it may be that those successful with these WMs inherently have more motion than the general population allowing them to excel at these specific WMs. However, at this point, we cannot definitively determine what ROM is required because there has been no assessment proposed to screen for either the shoulder or wrist motion required to safely perform these WMs.
THE JERK AND SNATCH—SHOULDER COMPLEX
The importance of both stability and mobility cannot be understated with respect to preventing injuries at the shoulder during training (2). Scapulothoracic stability is necessary to create a stable base for optimal glenohumeral joint function (24). The importance of stability at the scapulothoracic articulation is therefore critical in the overall functioning of the shoulder joint complex in relation to WMs, but is beyond the scope of this article. However, once stable, the shoulder complex with contributions from the acromioclavicular joint, the sternoclavicular joint, the scapulothoracic articulation, and the thoracic spine (7), must also function through a great ROM to successfully perform the jerk and snatch. Figure 5 demonstrates the ROM required at the shoulder complex and wrist complex in the catch position of a snatch.
All these joints need to move in conjunction with one another and deficiencies at one may lead to problems elsewhere. Shoulder injuries in a resistance trained population are well documented and account for 22–36% of total reported injuries (26,27). Reduced shoulder flexion along with incorrect technique while exercising have been identified as risk factors that may contribute to this injury prevalence (2,27).
Previous shoulder ROM tests have been described in the literature (21), but most rely on subjective assessments to help identify movement compensations (35). An objective test that may provide insight into an athlete's ability to achieve the overhead position of the jerk and snatch is the reverse wall slide (RWS). This test largely eliminates subjective insights and relies on specific objective criteria that can be graded using pass-fail criteria.
First described by Sahrmann in 2002, the RWS assesses an athlete's ability to achieve a controlled overhead position while maintaining a stable, neutral spine (35). The assessment attempts to determine whether an athlete can achieve 180° of shoulder elevation in the frontal plane, which has been reported as a requirement for overhead exercises (21).
The test position starts with the athlete's back to the wall and the heels 6 cm away from the wall (35). The entire spine, from the occiput to the lumbar region rests against the wall and the rib cage is pulled down to eliminate excessive lumbar lordosis. The elbows should start at 90° of flexion with the shoulders abducted and externally rotated to 90° (40). Figure 6 shows the starting position of the test from a front view and Figure 7 shows the starting position from the side with shoes removed to better measure distance from the heel to wall. Keeping the elbows and dorsal surface of the hands in contact with the wall, the athlete slides the arms up overhead until the elbows are fully extended. Although the end position is not accurately described, a good potential stopping point may be when the upper extremity is in the plane of the lower trapezius as in a “Y” position, and when the biceps are approaching contact with the ears, as seen in Figures 8 and 9 where a fully flexed or abducted position of the glenohumeral joint is shown. This position will limit compensations through the lumbar and thoracic spine that both tend to extend to compensate for limitations in shoulder flexion and abduction (2,27). In addition, the end position described above replicates the positional requirements needed in attaining the overhead position assumed in many WMs. Currently, there are no available data describing this measure's reliability.
THE JERK AND SNATCH—WRIST
As the shoulder provides the majority of the mobility required for the performance of the jerk and snatch, the wrist serves a dual purpose allowing the large ranges necessary for object manipulation, but more importantly, it provides a stable base to accommodate the large forces associated with performing these lifts. As with the other joints already discussed, there is no clear evidence in the literature describing the wrist ROM necessary for WMs, nor is there an accepted gold standard for a quick, easily performed assessment of wrist motion in a closed chain position.
Similar to the position the wrist assumes during a gymnastics handstand, the wrist assumes a hyperextended and compressed position during WMs (34) such as at the beginning of a jerk. This position is known as the front-rack position demonstrated in Figure 10. Despite the lack of normative data for wrist ROM required to assume this position, greater than 95° of passive wrist extension is recommended, based on the largest reported values in a healthy population (31). However, comparing the ROM values presented in Table 2, a weightlifting population seems to demonstrate greater active motion abilities (15), which again may predispose success in their chosen sport. It is suspected that because of the positional requirements WMs demand, these athletes have adapted to better handle the ranges and loads they encounter to avoid injury, compared with those who do not routinely resistance train and assume these wrist positions (3). Furthermore, it is speculated that passive ROM in this population will be greater than their active motion (3,31). As a result, passive wrist extension ROM of at least 95° for athletes participating in WMs seems appropriate.
The literature has yet to draw a conclusion on whether a lack of motion at the wrist can lead to increased injury rates in the weightlifting population. However, gymnasts are another group of athletes who routinely require great degrees of motion in conjunction with the transmission of larger forces through their wrists that may be examined for comparison. The prevalence of wrist injuries like this in gymnasts is high with 46–87% of gymnasts reporting either a wrist injury or developing chronic wrist pain at some point in their career (31,34). Despite these similar wrist requirements, the number of injuries in weightlifting seems to be minimal. Calhoon and Fry (5) reported that wrist injuries comprised only 10% of injuries in elite level Olympic lifters over a 6-year period.
To assess wrist extension ROM in athletes performing WMs and perhaps avoid compensation at other joints, a reproducible, weight-bearing test that simulates the motion and loading demands of the jerk and snatch is required. The weight-bearing box test (WBBT) may be the best assessment tool available. To perform the test, the athlete starts by facing their fingers away from them on a flat surface with a straight elbow. With the palm resting flat on the test surface, fingers extended, the athlete begins to bear weight through the wrist ensuring that the palm remains in contact with the test surface. The athlete then shifts their weight forward toward the fingers until the palm begins to rise. At the point which the palm first loses contact with the test surface, the position of the forearm is noted in relation to an imaginary vertical plane shown in Figure 11.
If the forearm does not reach or pass beyond the vertical plane, the athlete can reposition their hand, so fingers 2–5 are passively flexed over the edge of the box at the metacarpal phalangeal joints as in Figure 12. This places the musculature of the finger flexors on slack and isolates the motion to the osseous structures of the wrist to a greater degree. The same weight-bearing progression is then retested to determine whether a difference exists. This position mimics the muscle length requirements seen in the clean and jerk and snatch movements, as the fingers are allowed to flex around the barbell. As a result, this slackened position of the WBBT may most accurately assess the demands on the wrist during the jerk and snatch lifts.
The goal of an assessment tool is to determine whether an individual has the mobility, stability, endurance, strength, and motor control to participate in athletic and training activities. By identifying imbalances and asymmetries that may predispose an athlete to injury, strength and conditioning professionals may be able to reduce a portion of that risk. Currently, no comprehensive system to assess the ROM requirements in a weightlifting population, performing WMs such as the clean and jerk and the snatch, has been proposed. By using the tests described, the ROM required at the ankle, knee, hip, shoulder, and wrist to safely perform a deep squat, a clean and jerk, and a snatch can be quickly assessed in functional positions. Using a pass/fail criteria like that outlined in Table 3, a strength and conditioning professional can determine whether an athlete is appropriate, from a ROM standpoint, to begin or return to these types of lifts. This article is proposing the use of the WBLT, the SKTC, the RWS, and the WBBT together as a potential assessment tool that may fill this void.
One of the limitations not addressed in detail throughout this article is the use of a heeled weightlifting shoe. This specialized footwear would likely decrease the necessary ankle dorsiflexion ROM requirements during squatting. The use of a heeled weightlifting shoe may be one way a strength and conditioning professional can address ankle mobility limitations in an athlete identified during the WBLT. Another limitation of this article is the use of the WBBT. As described, this test does not precisely resemble the wrist during the front-rack position of the jerk or the terminal overhead positions of the jerk and snatch. However, if an athlete passes the WBBT, the mobility requirements of the wrist flexors would be more than sufficient to cover the mobility requirements of the WMs. In this position, the flexor mass is maximally stretched and therefore would be able to tolerate the WM. Finally, it is not the purpose of this assessment tool to prevent participation in WMs if an athlete is not successful in passing the tests. Rather, its purpose is to provide the strength and conditioning professional a means to determine the ROM an athlete possesses and whether limitations are present that may need to be addressed to increase the potential for success and decrease the risk of injury when performing WMs.
Use of this assessment tool may help to prevent injury by identifying athletes who have, at the very least, the motion required to perform certain lifts and those who do not. This assessment further provides strength and conditioning professionals focused joints for the prescription of other therapeutic exercises to assist the athlete in gaining the motion required to perform WMs safely. Finally, this assessment provides an objective way to reevaluate an athlete's progress. This assessment can then assist a strength and conditioning professional in the decision-making process regarding whether an athlete can advance or may need to be referred to a different provider within the sports medicine team.
The 4 tests: the WBLT, SKTC, RWS, and WBBT, when performed together can provide an objective and reproducible way to assess motion in the key joints necessary for an athlete to safely and appropriately perform WMs and in turn, potentially reduce the risk of injury and improve sport performance overall.
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Keywords:© 2018 by the National Strength & Conditioning Association
assessment; athlete; injury prevention; weightlifting