Review: The effect of increasing loading on powerlifting movement form during the squat and deadlift
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Powerlifting often gets a bad reputation as a high-risk injury sport, but more recent studies have assessed powerlifting as low to moderate risk of injury. The highest risk for injury seems to be among lower level athletes, and injury risk includes both acute and chronic complaints. Between 33-47% of injuries studied are lower back injuries and approximately 30% are shoulder injuries. Lumbar injuries are thought to be a consequence of the extreme compressive and shear forces placed on the spine during the squat and deadlift. With weight lifted sometimes exceeding up to five times the lifter’s bodyweight, it is imperative that proper technique is used--using incorrect form exacerbates the effect of these forces on the lifter’s body.
Many of the injuries incurred in powerlifting are a result of posterior chain dysfunction, resulting in exaggerated lumbar or thoracic kyphosis. This positioning can deactivate the larger lumbar musculature, resulting in myoelectrical silence. Myoelectrical silence distributes excessive stress to the spinal ligaments, neural arch, disks, and facet joints of the lumbar spine. The knees may also be injured by increased moment arms on the knee joint, or by valgus collapse harming the ligaments that stabilize the knee. Imbalances in muscular strength or mobility often result in rotational movements at the torso, predisposing those athletes to injury. As correct form disperses compressive forces throughout the joints and reduces injury risk, it makes sense that using it should be a priority for lifters.
Training for powerlifting often includes very competition specific training, mean that lifters typically perform large amounts of training volume on the same competitive exercises. Any technical concerns are repeated at high frequency under increasing loads.
The purpose of the reviewed study was to examine the effect of increasing loading on technique during the squat and deadlift exercises. The researchers sought to determine if technical breakdowns occur at a certain percentage of lifters’ maximum capability and whether or not that threshold is correlated to athlete level. The study hoped to determine an upper ceiling of training percentages to inform coaching and training practices.
For this study, athletes were filmed on squats and deadlifts during one peaking session of their training cycle. The researchers chose a session designed to mimic a competition, and the athletes were loaded in incremental volumes until they reached their maximum weight (with rest between sets). The athletes were recorded in their normal training setting. Researchers analyzed lifts that would be considered successful in a competition for form and/or technique, comparing between loads and between individual subjects.
Six strength sport athletes made up the group of participants between 20 and 27 years of age, with a body mass between 83 and 144kgs. Athletes had completed at least two years of powerlifting-style resistance training and current powerlifting competitors. These lifters also held a minimum of a Bachelors level degree in Sports Science.
Subjects were recorded via digital video camera placed approximately 3 meters away, set on a tripod corresponding to the subject's center of mass. The camera was set in the transverse plane so it could capture both sagittal and frontal plane data. The researchers chose to use olympic weightlifting equipment rather than powerlifting equipment for testing, but do not give a reason for this choice. Lifts were performed “raw” (knee sleeves and non-supportive singlets, no knee wraps or supportive suits), and loading could be increased increments of 2.5kg to 20kg.
Percentage-loading increments were implemented using pre-determined 1RM values for each athlete. Lifters began with 50% of 1RM and increased by 10% until they reached their previous 1RM value. Rest time was greater than 5 minutes between lifts, and lifters were verbally cued and encouraged during lifts as if it were a competition.
Performance indicators: Eccentric portion and any pausing occuring at the bottom of the squat, concentric portion of the squat, concentric portion of the squat, lower back rounding (lumbar flexion), upper back rounding (thoracic flexion/kyphosis), knee valgus or varus (assessed unilaterally).
Researchers used coding software to individually analyze the performance indicators above, saving the coding into a database for each movement for further statistical analysis.
Deadlift: Total lift time considerably increased under the 100% loading condition, and total number of technical inclusions (see performance indicators above) increased significantly in both the 90% and 100% loading scenarios versus the baseline 70% loading. Lumbar flexion made up 90% of total inclusions and was significantly increased at 90% and 100% 1RM. Thoracic flexion was not significantly increased with additional load.
Squat: For the squat, lift time also increased under the 100% load. High levels of variance between participants produced no significant changes to other technical inclusions. 66% of occurrences were at the lumbar spine, 26% at the knee, and 8% at the thoracic spine.
“The investigation of high occurrence negative technique markers with increasing load is key to injury prevention both during competition and training.”
For the deadlift, the main concern is lumbar flexion at 90% and above. Based on the results of this study, 90% of one rep maximum appears to be the threshold for technique breakdown. Considering the small sample size, however, this result needs further investigation to confirm. The authors recommend assessing each athlete individually. Some of this technical breakdown is evident even in elite lifters and may be accepted as part of pushing the body to its limits.
For squats, total time under maximum load is the main trend. Though findings for other technical flaws were not significant, it was hypethosized that most were due to a lack of movement competency.
The researchers hypothesized that novice lifters are most likely to elicit poor form, but that deadlift form was more related to loading percentage than technical knowledge. Because the relationship between strength level and technique issues was not studied, this is just speculation.
Limitations: Only the length of time of technical breakdown was measured, rather than the severity. Additionally, coding relied on the athlete’s personal feeling of maximum effort. In future studies, two cameras should be used, one in the frontal plane and one in the sagittal (one in front, one to the side) **I would like to include the following as a limitation: The athletes were competitive powerlifters having their competition specific technique analyzed, but were asked to perform the lifts on competitive weightlifting equipment (a bar designed to spin and bumper plates), which would require the athlete to adjust their technique accordingly. Calibrated steel plates and powerlifting competition bars would distribute the load being lifted differently, which could certainly have an effect on lifting technique.
Based upon the results of this study, there is no loading threshold for technical breakdown in the squat, rather breakdown is based on individual lifter characteristics. Deadlifts appear to begin to break down at 90% or higher. The researchers recommend training deadlifts below 90% to decrease the risk of injury and assessing squats individually for each lifter.
Based both on the results of this study and anecdotal observations from my coaching and competitive experience, it is absolutely best to spend the vast majority of training time at loads under 90%. The results of this study provide some confirmation for my current working theory that including light work focusing specifically on improving and perfecting technique is vital to injury reduction as well as increasing strength potential on meet day by allowing the lifter to maintain good technique under higher loads. Additionally, as the researchers mention in the introduction, it is important for a lifter to include exercises that are not competition specific in their training to reduce the repetitive stress of training squats and deadlifts, but also to eliminate imbalances and increase overall athleticism.
What “style” of programming leads to the least amount of injuries, and how can coaches improve the current training program trends to best avoid lifter injury?
Most lifters can benefit from direct core training, especially the inclusion of exercises that train trunk stability during movement of the extremities (dead bugs, bird dogs, etc). What is the necessary dosage of this type of core training to effectively negate injury risk (if possible)?