This was oral intercondylar notch and the quadriceps tendon may assumed to be due to greater deceleration needed during the increase the injury potential of the quadriceps tendon. As- sive and shear forces between the descent and ascent. Shear suming a 3. The general sive stress would be This pattern observed was as knee flexion increased, compressive large stress applied repetitively over time may cause degen- and shear forces also increased.
Hence, per- Toutoungi et al. PCL forces, which were minimize tendofemoral stress and minimize injury potential generated throughout the squat descent and ascent, progres- to the tendofemoral complex. During both the squat descent inertial, external, and muscle forces into account.
Therefore, these authors concluded that during PCL lifted the greatest load kg , and subject three exhibited rehabilitation the squat should not be performed at these the greatest forward knee movement. Shear as knee flexion increased. Negligible ACL forces between 0 force direction was not stated.
Minimum shear val- very similar to the posterior shear forces reported by Dahl- ues were approximately N for the subject that bounced kvist et al. The peak PCL forces reported by Toutoungi et al. These peak posterior shear during the barbell squat Table 1. The performed the barbell squat with an external resistance considerably smaller compressive and shear forces in this between — N.
Posterior shear forces were ob- squat Table 1. Kinematic data were captured at 50 Hz by served for all subjects throughout the descent and ascent a three-camera motion system, while a force platform was phases. These shear forces progressively increased as the used to collect kinetic data. Inverse dynamics and external knees flexed and decreased as the knees extended. The forces were used to calculate knee joint forces.
Two different cadences were used: a reconstructed PCL. Furthermore, since no anterior shear a slow cadence, where the descent and ascent phases lasted forces were observed, performing the squat may be appro- 2 s each; and b a fast cadence, where the descent and ascent priate for ACL patients. To test for fatigue, 50 continuous repetitions were completed for each load and cadence, and Patellofemoral Compressive Forces were subdivided into initial, middle, and final phases.
Excessive compressive force and stress, or repetitive occur- Hence, fatigue during the squat may increase loading of the rences of lower magnitude force and stress, may contribute cruciate ligaments. Fatigue became most apparent when the to patellofemoral degeneration and pathologies, such as subjects were approximately half way through their 50 rep- patella chondromalacia and osteoarthritis.
There are three etitions. During the squat, all these forces are performed in a slow controlled manner to minimize shear affected by knee flexion angle. Mathematically, compres- and compressive forces. Knee forces were symmetrical be- sive force is greatest at higher knee flexion angles, because tween the descent and ascent, with maximal shear and there are larger force components from the quadriceps ten- compressive forces occurring at maximum knee flexion.
Mediolateral shear forces were less than N throughout Patellofemoral compressive forces arise from contact be- all squat conditions and phases and therefore can be tween the undersurface of the patella and the femoral con- discounted. From full extension to full flexion, the patella moves Andrews et al. Patellofemoral exercises Table 1. A two-dimensional lifting model was contact has been reported to initially occur between 10 and used utilizing external forces and inverse dynamics.
The femur of squats. The descent times were 2 s for medial and lateral middle facets between approximately 30 all conditions. Because chine squat compared with the barbell squat. Hence, tified patellofemoral compressive forces during the dynamic injury potential to the cruciate ligaments may be greater squat 13,17,18,43,51, Four of these studies involved during the machine squat and during fast lifting rates.
Because these during the barbell squat Table 1. Compressive forces in- torques are resultant i. Because do so. Less quadriceps force would indeed explain why peak peak compressive forces generally occur near maximum patellofemoral compressive force was less in powerlifters, knee flexion, individuals with patellofemoral disorders because quadriceps tendon force and patellar tendon force should avoid performing the squat at high knee flexion would also be less.
However, EMG data from Wretenberg et angles. However, performing the squat in the functional al. Because for patellofemoral patients, because only low to moderate the hamstrings produce a knee flexor torque, a greater knee patellofemoral compressive forces were generated in this extensor torque would be needed.
Hence, greater quadriceps range. In addition, Escamilla et al. No significant differences in mius also generates a knee flexor torque by their duel role compressive forces were observed between the feet pointing as knee flexors and ankle plantar flexors. Compressive nemius activity has been observed during the squat forces progressively increased as the knees flexed and de- 13,17,18 , which is needed during the squat to control ankle creased as the knees extended.
No significant differences in to develop the hip and trunk extensors primarily. In contrast, compressive forces occurred between the narrow and wide many athletes use the high-bar squat to elicit more quadri- stance during the squat ascent. It can be inferred from these to perform the squat but minimize patellofemoral compres- data that narrow stance may be preferred over the wide sive force.
Moreover, the low-bar squat position of greater stance when the objective is to minimize compressive forward trunk lean has been reported to decrease potential forces. ACL strain, in part due to greater hamstring activity and less Wretenberg et al. Hence, squatting with greater for- powerlifters in quantifying compressive forces Table 1.
Furthermore, greater forward trunk which the bar was positioned across the back approximately lean also minimizes forward knee movement, which has 3—5 cm below the level of the acromion.
The weightlifters been shown to increase knee shear forces 3. Unfortunately, employed a high-bar squat position, in which the bar was a greater forward trunk lean may increase the injury risk to positioned across the back at approximately the level of the back musculature and ligamentous structures. Compressive forces generally increased as knee Nisell and Ekholm 43 employed competitive powerlift- flexion increased.
The large disparity in normalized values ers to quantify compressive forces during the barbell squat between weightlifters and powerlifters is probably due to ascent Table 1. Like the three previous barbell squat stud- technique variations, such as low and high bar positions. The extended. Although the mean peak compressive force was primary reason for this is to lift more weight, because 7. Consequently, the low-bar squat position produced pressive force were Dahlkvist et al.
Like the four previous studies 17,18,43,68 , com- squat 6,13,17,18,25,27,34,38,40,54,55,58,65,68— Eleven of pressive forces progressive increased as the knees flexed these studies performed the barbell squat with an external load and decreased as the knees extended, peaking near maxi- 17,18,34,40,54,55,58,65,68—70 , whereas the remaining five mum knee flexion.
Normalized values from Dahlkvist et al. The pri- 13 and Reilly and Martens 51 were approximately 4 mary knee muscles utilized during the squat are the quad- times greater than normalized values from Escamilla et al.
Quadriceps activity progressively increased as the knee 13 and Reilly and Martens Although these loads are higher than 18,27,40,55,58, Hence, descending barbell squat.
Patellofemoral joint con- Escamilla et al. By using 18 , Wretenberg et al. The these contact areas and squat ascent compressive force data lower activity observed in the rectus femoris compared with from Escamilla et al. Increased activity from MPa, 2. The rectus femoris knee flexion, compressive force has been shown to remain is probably more effective as a knee extensor during the relatively constant 17,18, Hence, stress may decrease at squat when the trunk is more upright, because it is in a larger knee flexion angles, because patellofemoral contact lengthened position compared with when the trunk is tilted area continues to increase.
Therefore, per- Hamstring activity from Escamilla et al. These authors reported peak hamstring patellofemoral pathologies. This can be a potential Stuart et al. The lower tion techniques should be employed when performing the hamstring activity in these studies is probably due to their squat, in which training is divided into light, medium, and subjects lifting a lower percentage of their 1 RM.
Subjects heavy intensity cycles throughout the year. Several stud- To determine which muscles are being developed during the ies have reported greater overall hamstring activity during squat and to what degree, it is helpful to quantify muscle activity the ascent compared with the descent 17,18,27,34,40, Their study varied the descent and concentrically during the ascent, as com- foot angle by changing forefoot inversion and eversion monly is believed.
In reality, they may actually be working rather than changing forefoot adduction and abduction. If they are indeed working eccentrically during the descent Hence, data from these studies show that varying foot angles and concentrically during the ascent, as is traditionally be- do not appear to affect quadriceps, hamstrings, or gastroc- lieved, then data from the above studies would be in accord nemius activity during the squat.
In any case, the hamstrings probably do stance on knee muscle activity during the squat not change length much throughout the squat. Hence, in 1,18,34, In addition, these authors to be more effective in generating force throughout the reported no significant differences in quadriceps or ham- entire squatting movement. Tesch 59 , using magnetic resonance imaging creased as the knees extended.
Because the ankle dorsiflexes during narrow and wide stance squats. Anderson et al. These results imply that ankle plantar flexion. However, because the gastrocnemius increasing knee flexion angles during the BW squat elicited is a biarticular muscle, its length may not change much greater activity of the VMO relative to the VL. One addi- throughout the squat, because it shortens at the knee and tional study 6 investigated the effects of moving the feet lengthens at the ankle during the descent, and lengthens at forward while performing a machine squat exercise.
This the knee and shortens at the ankle during the ascent. Normal tibial in- hamstrings, or gastrocnemius activity between the two foot ternal rotation in knee flexion and tibial external rotation in angles. Signorile et al. They found no attempts to externally rotate.
This is supported Costigan and significant differences in VM, VL, and rectus femoris ac- Reid 12 , who demonstrated that during the squat the tibia tivity among the three foot positions. Ninos et al. No significant dif- squat are supported in part by cruciate and collateral knee ferences were observed in quadriceps VM and VL or ligaments, which help provide knee stability. The ACL and hamstrings semimembranosus, semitendinosus, and biceps PCL provide anteroposterior knee stability, while the MCL femoris activity between the two foot angles.
Hung and and LCL provide mediolateral knee stability. MCL, especially with severe internal rotation of the femur This is important because excessive anteroposterior or me- relative to the tibia.
Because the MCL attaches to the medial diolateral knee translation measurements may indicate knee meniscus, a twisting strain to the MCL may tear or detach instability due to damage to the cruciate or collateral liga- the medial meniscus from its adjacent fibrous capsule. Part ments.
To date, there are seven known studies that examined of this torn meniscus can become displaced toward the how the dynamic squat affects anteroposterior or mediolat- center of the joint space and become lodged between the eral knee stability 5,10,21,28,37,49, Based on these in fected anteroposterior and mediolateral knee stability.
This is typically and cruciate ligaments. Klein 28 first investigated the strain on knee stability 9. The 28 , using the same mediolateral collateral ligament testing deep squat group was comprised of competitive weight- instrument to measure collateral ligament stability. Sixty- lifters, all of which practiced the deep squat exercise in nine male subjects were randomly assigned to eight differ- training and competition.
The control group was comprised ent treatment groups involving variations of the deep and of subjects from beginning weight training, basketball, parallel squat consisting of low and high lifting loads and and gymnastic classes from local universities. None of the speeds. Comparing the 8 wk.
For each training session each subject performed one results within the deep squat group, the LCL was stretched set of 10 repetitions, for a total of repetitions for the 8 to a greater extent than the MCL.
Furthermore, there was wk. All subjects were pretested 1 wk before beginning their No significant differences were found within any of the left MCL instability. Although Henning et al. ACL elongation within the joint due to the posterior thigh musculature com- was expressed relative to fiber elongation using a force of ing in contact with the calf muscle at the bottom position of N during a Lachman test.
The one legged squat pro- the squat. These in vivo re- as the Lachman test, jogging 2. As previously dis- ceptible to injury and abnormal stretch during the deep cussed, Beynnon et al. As the femur internally rotated at the beginning of and just after performing the squat, playing basketball, and the ascent, the posterior medial meniscus is forced toward running.
Four groups of subjects 37 male and 18 female the center of the joint space. This can place strain on the with healthy knees were used, comprised of sedentary con- inner medial meniscus, causing it to tear. Nine sedentary controls were measured before and powerlifters showed tighter knees than the control group, after a 2-h time interval. Twenty-four athletes performed the whereas the weightlifting group showed no significant dif- powerlifting squat, lifting an average of 1. When mean of 24 repetitions.
Ten basketball players were tested groups were subdivided by skill, low-skilled weightlifters before and immediately after a strenuous 1. Because the immediately after a sanctioned km run. The percent significant differences seen were all less than 2 mm, perhaps change between the pretest and posttest for anterior laxity, the 8-wk program 2—3 times per week was not long enough posterior laxity, and total anteroposterior laxity, respec- to elicit meaningful changes.
Significant increases in anteroposterior Interestingly, the control group, who had very little or no laxity were observed in the basketball players and distance squatting experience, consistently had the loosest knees. The powerlifters had the smallest lifters were tighter than the controls for four of the nine percent change in total anteroposterior laxity, with a de- measurements.
The authors concluded that the squat did not crease in posterior laxity from pretest to posttest. Resting have negative effects on knee stability and may be consid- anteroposterior laxities among the groups were also re- ered safe in terms of not causing permanent stretching of the corded.
Distance runners had significantly less anterior lax- ligaments. Because the exercise on anteroposterior knee translation in professional greatest anteroposterior laxity was found in basketball play- football players. Conclusions: The squat was shown to be an effective exercise to employ during cruciate ligament or patellofemoral rehabilitation. For athletes with healthy knees, performing the parallel squat is recommended over the deep squat, because injury potential to the menisci and cruciate and collateral ligaments may increase with the deep squat.
The squat does not compromise knee stability, and can enhance stability if performed correctly. Finally, the squat can be effective in developing hip, knee, and ankle musculature, because moderate to high quadriceps, hamstrings, and gastrocnemius activity were produced during the squat.
Abstract Purpose: Because a strong and stable knee is paramount to an athlete's or patient's success, an understanding of knee biomechanics while performing the squat is helpful to therapists, trainers, sports medicine physicians, researchers, coaches, and athletes who are interested in closed kinetic chain exercises, knee rehabilitation, and training for sport.
Results Citations. Topics from this paper. Posterior muscle of thigh structure Structure of quadriceps femoris muscle sports medicine specialty.
Exercise Gastrocnemius muscle structure Kinetics. Citation Type. Has PDF. Publication Type. More Filters. Knee Orthoses for Sports-Related Issues. Atlas of Orthoses and Assistive Devices. Biomechanics of Front and Back Squat exercises.
Squat constitutes one of the most popular exercises to strengthen the muscles of the lower limbs. It is considered one of the most widely spread exercises for muscle sport training and is part of the … Expand. Journal of strength and conditioning research. Highly Influenced. View 6 excerpts, cites background. Knee biomechanics during squat rising with patella alta and after distal transfer of tibial tubercular surgery. Objective: Patella alta has commonly seen in prior adolescent cerebral palsy population with crouch gait pattern.
Unfortunately, for the treatments of patella alta and crouch gait, the outcomes of … Expand. View 3 excerpts, cites background. Applied Sciences. This study examined the differences of knee joint forces between lowering to, or rising from squat, and typical final postures of squatting and kneeling.
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