Compared to Someone Who Can Squat 75 Kg, Someone Else Who Can Squat 150 Kg Has

J Strength Cond Res. Author manuscript; available in PMC 2022 Jun 20.

Published in final edited form as:

PMCID: PMC4064719

NIHMSID: NIHMS577591

Knee Joint Kinetics in Relation to Ordinarily Prescribed Squat Loads and Depths

Joshua A. Cotter

¹Section of Orthopedics, University of California, Irvine, California

Ait M. Chaudhari

ⁱⁱDepartment of Orthopedics, Ohio State University, Columbus, Ohio

³Department of Mechanical and Aerospace Engineering, Ohio Country Academy, Columbus, Ohio

^ivSports Health and Performance Establish, Ohio State University, Columbus, Ohio

Steve T. Jamison

²Section of Orthopedics, Ohio Country Academy, Columbus, Ohio

ⁱⁱⁱDepartment of Mechanical and Aerospace Engineering, Ohio State University, Columbus, Ohio

⁴Sports Wellness and Performance Constitute, Ohio State University, Columbus, Ohio

Steven T. Devor

⁵Department of Health and Practise Scientific discipline, Ohio Land University, Columbus, Ohio

^{half dozen}Department of Physiology and Cell Biological science, Ohio Country University, Columbus, Ohio

^sevenSection of Homo Nutrition, Ohio Land University, Columbus, Ohio

Abstruse

Controversy exists regarding the condom and operation benefits of performing the squat exercise to depths across ninety° of knee flexion. Our aim was to compare the net meridian external knee flexion moments (pEKFM) experienced over typical ranges of squat loads and depths. 16 recreationally trained males (n = 16; 22.seven ± 1.1 yrs; 85.4 ± 2.1 kg; 177.6 ± 0.96 cm; mean ± SEM) with no previous lower limb surgeries or other orthopedic issues and at to the lowest degree 1 year of consequent resistance training experience while utilizing the squat do performed unmarried repetition squat trials in a random lodge at squat depths of above parallel, parallel, and beneath parallel. Less than 1 calendar week before testing, ane repetition maximum (1RM) values were establish for each squat depth. Subsequent testing required subjects to perform squats at the three depths with three different loads: unloaded, fifty% 1RM, and 85% 1RM (9 total trials). Force platform and kinematic information were nerveless to summate pEKFM. To assess differences among loads and depths, a 2-gene (load and depth) repeated-measures ANOVA with significance set at the P < 0.05 level was used. Squat 1RM significantly decreased 13.6% from the higher up parallel to parallel squat and some other 3.half-dozen% from the parallel to the below parallel squat (P < 0.05). Net elevation external articulatio genus flexion moments significantly increased every bit both squat depth and load were increased (P ≤ 0.02). Slopes of pEKFM were greater from unloaded to 50% 1RM than when progressing from 50% to 85% 1RM (P < 0.001). The results suggest that that typical decreases in squat loads used with increasing depths are not plenty to offset increases in pEKFM.

Keywords: biomechanics, deep flexion, back, joint, moment

INTRODUCTION

The dorsum squat exercise is utilized in a wide variety of environments ranging from clinical rehabilitation to formal strength and conditioning programs to everyday gym environments. The squat practise is pop because of its similarity and applicability to both activities of daily living and many athletic movements, and it is a multi-joint movement that requires many large muscle groups to office together (19, 24, 32). Many wellness professionals whose focus is on performance enhancement frequently recommend the squat do to increase ligament, tendon, and os strength; develop strength, speed, and ability of the lower back, hip and knee joint musculature; and improve neuromuscular efficiency (7, 31). Yet, other health professionals whose primary focus is rehabilitation afterwards knee injury list the deep squat every bit a contraindicated exercise (5) and recommend performing the squat exercise with limited genu flexion due to the commonly held conventionalities that the squat do may elicit dangerously high forces on the articulatio genus (fifteen, 29). In spite of the big body of work performed studying the squat practice (4, 6, 9, 11, 19, 26, 29, xxx, 32, 33, 35, 36, 38, 41, 42), information technology remains difficult to reconcile the differences in recommendations between these two schools of idea due to lack of a comprehensive written report comparison squats as recommended by both (11, 29).

The American College of Sports Medicine (ACSM) recommends that when engaging in resistance preparation, the apparently healthy developed should "perform every exercise through a full range of movement" (16). Working through a full range of move allows for strength adaptations to occur at every bending the articulation moves through, which may reduce injury potential in those ranges. In addition, utilizing total range of motion maintains flexibility for articulation integrity. Some coaches even utilize the deep squat as an assessment tool for lower body flexibility and symmetry of motility (8). In add-on, squatting type activities are widespread in many cultures where squatting beneath parallel is commonplace when toileting or resting (28). Even though many health professionals agree that working through total range of move is important, the genu articulation, and specifically the squat, are oftentimes seen as exceptions to the rule.

Many wellness professionals frequently recommend limiting squat depth to parallel or higher nether the assumption that doing so will reduce the potential of knee laxity and minimize harmful forces at the human knee joint (21), still some studies accept called into question the assumptions regarding muscle activation and articulatio genus laxity. In an electromyography study, Caterisano et al. plant that increasing squat depth but resulted in increased relative contribution of the gluteus maximus (4). In a study of instrumented laxity, Chandler et al. reported no difference in knee joint laxity following an 8 week training program including either above parallel or below parallel squats (half-dozen). Chandler et al. besides plant that both powerlifters and weightlifters had less laxity, i.e. "tighter" knees, than controls (half-dozen). The concern for harmful forces at the knee centers on peak patellofemoral articulation reaction force (pPFJRF), which may lead to patellofemoral pain syndrome (PFPS) by overloading the cartilage, potentially leading to cartilage degeneration and subsequent subchondral bone degeneration (23). PFPS is ane of the nigh common disorders of the articulatio genus, bookkeeping for nearly 30% of all knee injuries treated in sports medicine clinics and influencing both athletes and non-athletes akin (10, 13, 23). If the human relationship between pPFJRF and PFPS is correct, it would exist benign to empathise how pPFJRF is influenced past variations in the squat exercise.

Previous biomechanical analyses have indicated that increased pPFJRF is coupled with increased knee flexion angles (nine, 33). In squats up to 90° of knee flexion without an external load and with a load of 35% of subject's body weight, pPFJRF was constitute to increase linearly with peak external knee flexion moments (pEKFM) in untrained males (38). Dahlkvist et al. estimated increases in pPFJRF while squatting to total depth in an anarchistic squat with no external load where the heels practise not remain on the ground (9). In dissimilarity, when comparing squats with genu flexion angles of 70°, xc°, and 110° in trained females, Salem and Powers found no differences in pEKFM or pPFJRF with an 85% one repetition maximum (1RM) load (35). It is difficult to translate these conflicting reports on genu loading due to the large variations betwixt studies in load and technique. In addition, when basing loads off of 1RM values, 1RM values for each squat depth are not often independently tested. In studies using a conventional squat movement, pEKFM was found to be the major contributor of both pPFJRF as well every bit patellofemoral stresses (35, 38). Given the strong understanding between pEKFM and pPFJRF at flexion angles where both accept been experimentally observed and the lack of data on pPFJRF above 110° of knee flexion, for this report we examined pEKFM as a surrogate for pPFJRF.

Our aim was to compare pEKFM during the squat with loads and depths that are often prescribed in both rehabilitation and force training programs, including depth-specific 1RM measurements. To achieve our aim we tested the hypothesis that back squat 1RM will decrease with increased depth (i.eastward. above parallel 1RM > parallel 1RM > below parallel 1RM) and this decrease in 1RM would allow pEKFM to remain constant for load- and depth- matched squats (i.e. pEKFM for to a higher place parallel with 85% higher up parallel 1RM ≈ pEKFM for below parallel squat with 85% below parallel 1RM).

METHODS

Experimental Arroyo to the Trouble

To investigate the effect of commonly prescribed squat loads and depths on pEKFM, 9 combinations of differing loads and depths were analyzed. The iii pre-determined depths consisted of the thigh being above parallel, parallel, and below parallel to the ground. These depths were divers equally follows: the above parallel squat, to 90° of knee flexion; the parallel squat, to where the inguinal pucker falls just below the proximal patella; and the below parallel squat or deep squat, to when the backs of the thighs come up into contact with the calves. Normalized loading weather condition were calculated based on the 1RM loads determined at each of the iii depths. The iii loads chosen for each depth were unloaded, 50% 1RM, and 85% 1RM. An unloaded squat may be prescribed during rehabilitation from injury or during the initial periods of learning. Loads of fifty% 1RM and 85% 1RM are oft used for power and strength preparation, respectively. The order of the ix trials was randomly chosen for each subject. Peak external knee flexion moments were determined for each trial.

Subjects

Sixteen salubrious, recreationally trained males (north = 16; 22.7 ± ane.1 yrs; 85.4 ± two.1 kg; 177.6 ± 0.96 cm; mean ± SEM) with no previous lower limb surgeries or other orthopedic bug and at to the lowest degree i year of consistent resistance training experience while utilizing the squat exercise participated in the report. All subjects were visually assessed for the power to squat at full depth without hurting and with appropriate technique including the maintenance of having both heels in contact with the ground and proper lumbar lordosis throughout the whole motion. Experimental protocols were approved by the Institutional Review Board at The Ohio Country University and written informed consent was obtained by each field of study following a total presentation of procedures.

Procedures

Data were nerveless during two separate sessions with greater than 24 hours and less than 1 week between sessions. All testing was conducted during the months of January-March. Subjects were instructed to maintain their typical daily routine in regards to hydration, nutrition, and sleep and to not engage in any heavy physical activity several days prior to testing. One repetition max (1RM) testing was performed during the commencement session following recommendations set forth by the National Force and Conditioning Clan (iii). Subjects performed their normal warm-up typically done before squatting. The above parallel squat depth was determined by measuring xc° of articulatio genus flexion using a goniometer placed at the knee (Effigy 1A). The parallel squat depth was determined when the inguinal crease barbarous just below the proximal patella (17) (Effigy 1B). The below parallel squat depth was determined when the subject sabbatum fully in a squat position where the hamstrings come into contact with the calves (Figure 1C). Subjects were instructed to accept a natural opinion. Guild of 1RM testing was not randomized and started with the below parallel squat and concluded with the to a higher place parallel squat equally generally the 1RM is lower for the below parallel squat. Subjects were given every bit much fourth dimension as they desired betwixt attempts merely took no less than 1 minute for each rest interval. Previous research has found that residue intervals as short as 1 minute do not bear upon 1RM back squat operation when a repeated 1RM attempt is fabricated (25). Test-retest reliability for 1RM back squat testing has resulted in an intraclass correlation coefficient of r = 0.94 (P < 0.05) (25). Following 1RM testing, the 2nd session was scheduled between 24 hours and 7 days later on.

Above parallel (A); parallel (B); and below parallel (C) back squat.

A especially designed "light drape" device (Imprint Engineering science Corp., Minneapolis, MN), visible signal light and programmable logic controller (Allen-Bradley Corp., Milwaukee, WI) were used to provide feedback to the subject area to control squat depth and to limit whatsoever bouncing or inconsistencies in the amount of time in the bottom squat position for both 1RM and motility capture testing (Effigy 2). The light curtain is a device that senses when an object passes through a rectangular "curtain" of infrared light betwixt the two parts of the device. The position of the pall was adapted to the barbell acme for each subject field corresponding to each of the squat depths. The visible signal low-cal indicated to the bailiwick when to descend, when to hold in the bottom position, and when to ascend once more. This technique ensured that each subject consistently descended to the advisable depth for each trial and stayed at that depth for one second before ascending back to standing.

Light curtain setup. Sagittal view (A); posterior view (B).

Motion capture analysis was conducted during the 2d session. Retro-reflective markers (B&L Engineering, Santa Ana, CA) were attached to the legs of each subject with 2-sided latex-free agglutinative tape utilizing a modified Point-Cluster Technique (Pct) (1, 12) (Effigy three). This technique has shown comparable results to those obtained with intra-cortical pins placed into the femur and tibia (ane) and has been used to written report knee kinematics during walking and seated leg extension (12), run-to-cut maneuvers (20), and with ACL-reconstructed and uninjured contralateral knees (37). The modifications included a marker placed at the manubrium, every bit well every bit a ring of eight markers placed on the iliac spine including the anterior and posterior superior iliac spines, iliac crests, and the midpoints between iliac crest and posterior superior iliac spine markers. Nine full trials were randomly assigned, each containing a unique combination of squat depth (above parallel, parallel, or below parallel) and load (unloaded, 50% 1RM and 85% 1RM of the squat depth beingness performed). Unloaded squat trials consisted of the subject squatting with a PVC pipe held in the same position as a barbell to best mimic the normal squatting style for each subject. Loaded squats utilized a standard Olympic barbell and weight plates. Subjects were encouraged to use the aforementioned squatting manner that they typically use in training. All subjects utilized a high bar technique with heels remaining in contact with the floor, a natural stance (43.91 ± six.7 cm between markers on the posterior attribute of the heel; across all trials), a forward or upward gaze, and maintained lumbar lordosis throughout the squat. Marker motion and footing reaction force data were recorded using an eight camera Vicon MX-F40 system (Oxford Metrics, Oxford, U.k.), two Bertec 4060-x force plates (Bertec Corporation, Columbus, OH), and Vicon Nexus software (Oxford Metrics, Oxford, UK). 3-dimensional marker data was filtered using a General Cantankerous-Validation (GCV) Woltring filter (forty) within Vicon Nexus. Custom scripts in MATLAB (The Mathworks, Natick, MA) and Vicon Bodybuilder (Oxford Metrics, Oxford, UK) were then used to summate genu kinematics and kinetics, post-obit previously-described methods for processing point-cluster information (ane) and calculating cyberspace external joint reaction moments (2), using conventions for tibiofemoral kinematics described past Grood and Suntay (eighteen). Meridian external knee flexion moments (Nm) were normalized by trunk weight (BW, N) and meridian (ht, k) to obtain pEKFM (%BW*ht) used for analysis (27). Slopes of the pEKFM vs. %1RM curves were too calculated for analysis.

Marking placement utilizing the Point-Cluster Technique.

Statistical Analyses

A one-manner repeated measures ANOVA was used to compare 1RM at each squat depth. Two separate 2-way repeated measures ANOVA (depth*load and depth*load progression) were used to compare pEKFM and slopes. T-tests were used as a post-hoc assay when a pregnant F-ratio was observed from the ANOVA. A Bonferroni correction was used for multiple comparisons. All data analyses were performed using SPSS version nineteen.0 (IBM SPSS Statistics Inc., Chicago, IL). Significance levels were set at P < 0.05. All data are presented as mean ± SEM.

RESULTS

Pregnant differences were found for squat 1RM at each depth (F_{1.50, 21.88} = 61.21, P < 0.001). The largest 1RM was found for the above parallel squat at 150.42 ± 4.92 kg decreasing to 129.97 ± four.82 kg and 125.28 ± 4.34 kg (P < 0.05) for the parallel and below parallel squats, respectively (Figure 4).

Squat 1RM values. Data are presented every bit mean ± SE (due north = 16). Significant divergence (* P < 0.05; *** P < 0.001) betwixt 1RM values.

Significant main effects were found for load (F_{1.35, 20.29} = 191.36, P < 0.001) and depth (F_{ane.23, xviii.38} = 45.69, P < 0.001) in addition to a significant interaction effect for depth*load (F_{1.93, 28.87} = 10.18, P = 0.001) for pEKFM (Effigy 5). Increases in either load or depth for the back squat exercise significantly increased pEKFM. Inside each %1RM or squat depth, each signal was significantly different from the other two (P ≤ 0.02; Effigy 5).

Normalized summit external knee joint flexion moments (%BW*ht) vs. normalized weight on the bar (%1RM). Data are presented as hateful ± SE (northward = 16). All trials were significantly different (P ≤ 0.02).

To cheque the consistency of articulatio genus flexion angle at unlike depths, peak knee flexion angles were calculated for each of the nine weather condition (Table 1). On average, subjects squatted to a knee flexion angle of 98.73 ± i.54° for the above parallel squat, 123.70 ± ii.03° for the parallel squat, and 140.51 ± two.00° for the below parallel squat. Significant differences were found in the knee flexion angle for the in a higher place parallel and parallel squats as load increased. During the in a higher place parallel squats, genu flexion angle decreased as the load increased from unloaded to 50% 1RM (P = 0.001) and again to 85% 1RM (P = 0.014). Subjects also squatted with a knee flexion angle of ~5° less during the parallel squats with an 85% 1RM load compared to the unloaded and 50% 1RM trials (P < 0.05). No differences were seen in human knee flexion angles for the below parallel squats.

Table ane

Peak knee flexion angles.

	No Load	fifty% 1RM	85% 1RM	Boilerplate
Above Parallel	105.05 ± 1.44	97.33 ± 1.99**	93.82 ± i.81***†	98.73 ± 1.54
Parallel	125.07 ± 2.46	125.51 ± 2.12	120.51 ± 1.92*††	123.70 ± ii.03
Below Parallel	139.89 ± 2.09	141.78 ± 2.13	139.87 ± 2.23	140.51 ± ii.00

Analysis of pEKFM slopes (the 6 lines in Figure five) demonstrated significant main effects for increases in load (unloaded-50 vs. fifty–85, F_{1, xv} = 26.42, P < 0.001) and squat depth (F_{2, 30} = eleven.09, P < 0.001). A significant load*depth interaction result was also observed (F_{2, 30} = v.88, P = 0.007) (Effigy vi). The average gradient of pEKFM for all three depths from unloaded to 50% 1RM was 70% college than the boilerplate slope from fifty% 1RM to 85% 1RM. Specifically, higher up parallel (P = 0.007), parallel (P = 0.001) and beneath parallel (P < 0.001) squats prove significantly steeper slopes of pEKFM while progressing from unloaded to 50% 1RM than from l% 1RM to 85% 1RM (Effigy 6, marked with ‡‡,‡‡‡). Additionally, the below parallel squat has a significantly steeper slope of pEKFM while progressing from unloaded to 50% 1RM compared to the parallel and above parallel squats (P ≤ 0.004, Effigy 6, marked with††).

Bar graphs of the slopes of the normalized peak external knee flexion moments (%BW*ht) vs. weight on the bar from Effigy 4. Data are presented as mean ± SE (n = xvi). Meaning differences were observed in the average slopes across all depths (***, 0–fifty% vs. 50–85%, P < 0.001), between beneath parallel and the other depths when increasing from 0–50% (†† P < 0.01), and at each depth (0–50% vs. 50–85%, ‡‡ P < 0.01; ‡‡‡ P < 0.001).

DISCUSSION

The present written report demonstrates that the typical decreases in squat load seen with increasing squat depth were not plenty to get-go the increases in pEKFM seen with increasing knee flexion. As either load or depth is increased, pEKFM also increased. Therefore our hypothesis was non supported. Moreover, increases in load on the bar from unloaded to 50% 1RM exhibit college slopes of increased pEKFM than when increasing load from 50% 1RM to 85% 1RM. Although it is currently unknown what threshold of pinnacle or repetitive forces would be detrimental to the human knee joint, the data reported here tin be used to help design and implement programs utilizing the dorsum squat exercise.

Our findings are somewhat contrary to previous research involving the squat practice conducted by Salem and Powers who found no difference in external knee flexion moments (reported as internal human knee extension moments) at seventy°, 90°, and 110° of knee flexion utilizing a load of 85% 1RM (38). The authors did not specify whether depth-specific 1RM values were found, but if they only determined a single 1RM for the whole study, that lone would business relationship for the differences between their data and ours. Other potential reasons for these contradictory results may be that the previous study had a pocket-sized sample size of 5 subjects and utilized female person collegiate athletes.

Comparing our information to previously reported data for squatting is challenging due to the wide range of squatting styles, feel levels of subjects, loads utilized, and methodological differences. A summary of comparison data on studies that have reported pEFKM can exist establish in Table ii. The largest values for pEFKM were institute by Escamilla et al. in a study of Masters level powerlifters (14). They reported values as loftier equally 756 Nm for a 1RM squat with a wide stance. Although the loads were nearly double that of the to a higher place parallel back squat with an 85% 1RM load in our report, the pEKFM were over 4 times every bit high. Some of the everyman values were reported by Wallace et al. (38). Body weight squats with the hands behind the head and barbell squats utilizing 35% of the discipline's body weight (24.85 ± 5.6kg) to 90° of knee flexion gave pEKFM of 0.62 and 0.88 Nm/kg respectively. Comparatively, we observed pEKFM values that were nigh double although our knee flexion angles were ~10° larger and our loaded trial was ~3 times greater (75.21 ± 9.83kg) accounting for the differences.

Table 2

Comparing of studies that quantified height human knee moments for the squat. Data are presented equally mean ± SE.

Author	No. of Subjects	Gender	Mean Height (cm)	Hateful Weight (kg)	Feel Level	Exercise Description	Mean Load (kg)	Load Description	Elevation Knee Flexion	Accented Peak Knee Moment (Nm)	Relative Tiptop Knee Moment (Nm/kg) [%BW * ht]
Cotter - Electric current Report	16	One thousand	177.6 ± 0.96	85.4 ± 2.1	>one year of squat training	Dorsum Squat - To a higher place Parallel	0	No Load	105.05 ± 1.44	103.75 ± four.79	ane.21 ± 0.04 [7.21 ± 0.33]
							76.28 ± 2.47	50% 1RM	97.33 ± 1.99	152.53 ± 7.37	1.78 ± 0.06 [ten.59 ± 0.51]
							128.13 ± iv.21	85% 1RM	93.82 ± 1.81	178.51 ± 5.78	2.09 ± 0.04 [12.40 ± 0.40]
						Back Squat - Parallel	0	No Load	125.07 ± 2.46	118.02 ± 6.22	ane.38 ± 0.05 [8.xx ± 0.43]
							65.91 ± 2.48	50% 1RM	125.51 ± 2.12	177.82 ± 10.ix	2.07 ± 0.08 [12.35 ± 0.76]
							110.65 ± iv.12	85% 1RM	120.51 ± 1.92	195.67 ± 7.96	2.29 ± 0.07 [thirteen.59 ± 0.55]
						Back Squat - Below Parallel	0	No Load	139.89 ± two.09	129.03 ± 7.22	one.51 ± 0.06 [8.96 ± 0.fifty]
							63.78 ± 2.17	50% 1RM	141.78 ± 2.13	213.66 ± 13.75	2.48 ± 0.ten [14.84 ± 0.95]
							106.53 ± three.76	85% 1RM	139.87 ± 2.23	246.29 ± 14.61	2.87± 0.12 [17.xi ± 1.01]
Escamilla (xiii)	13	M	176.7 ± ane.9	82.iv ± vi.0	Main's level Powerlifters	Narrow Stance Squat	208.three ± 15.2	1RM	106 ± 2.ii	573 ± 49.6
	13	Grand	173.6 ± 2.0	93.1 ± six.9		Mid Opinion Squat	229.two ± 17.nine		102 ± 1.9	627 ± 64.six
	13	M	174.3 ± i.9	97.5 ± vii.8		Wide Stance Squat	238.7 ± 15.0		99 ± 2.8	756 ± 65.2
Gullet (18)	xv	9M 6F	171.2 ± 1.7	69.7 ± 1.vi	>1 year of squat training	Back Squat - Parallel	61.8 ± 4.8	lxx% 1RM			one.0 ± 0.ten
						Front end Squat - Parallel	48.5 ± three.6	70% 1RM			0.7 ± 0.05
Nissell and Ekholm (27)	one	M	181	110	Experienced Powerlifter	Back Squat - Parallel	0	No Load	120	83.3
							100	~30% 1RM	120	145
							250	~70% 1RM	120	233.3
Robertson (31)	half-dozen	K	184	83.65	Experienced Weightlifters	Dorsum Squat	93.i	80% 1RM	120	100
Salem and Powers (32)	v	F	178 ± 4.7	73 ± 4.5	3 Basketball/2 Volleyball Intercollegiate Athletes	Shallow Squat	53 ± 5.4	85% 1RM	72.eight	127.4
						Medium Squat			91.5	128.7
						Deep Squat			109.7	138.iv
Salem (33)	8	7M 1F		93.3 ± half-dozen.four	~xxx weeks after ACLr	Back Squat - Involved Leg	32.65	35% of body weight	106.98 ± three.68		ane.02 ± 0.eleven
						Back Squat - Uninvolved Leg			109.55 ± 4.06		1.28 ± 0.10
Wallace (34)	15	6M 9F	171 ± 2.3	72 ± 4.1	Healthy Adults	Unloaded Squat	0	Hands backside head	90		0.62 ± 0.03
						Loaded Barbell Squat	24.85 ± 1.four	35% of body weight	ninety		0.88± 0.0.03
Wilk (35)	10	M	177 ± 2.eight	93 ± four.iv	Experienced Weightlifters	Parallel Squat	147 ± 12.three	4 reps with 12RM weight	104 ± 3.five	150 ± 12.half dozen
Wretenberg (37)	six	1000	170.8 ± 3.3	87 ± 8.ii	Powerlifters	Parallel Squat	154.2 ± 8.6	65% 1RM	111 ± ii.0	92 ± 20.1
						Deep Squat			126 ± one.6	139 ± 26.2
	8	M	177.0 ± 2.7	82 ± 3.9	Weightlifters	Parallel Squat	101.9 ± 9.8	65% 1RM	116± ane.7	131 ± half-dozen.1
						Deep Squat			138± ane.ane	191 ± 14.4

The present report showed that the slope of pEKFM was greater when progressing from an unloaded squat to squatting with a 50% 1RM than when progressing from 50% 1RM to 85% 1RM with the greatest slope seen for the below parallel squat. This of import finding suggests that as beginners or individuals in a rehabilitation program brand initial progressions in load and depth, caution should be expressed every bit increases in pEKFM occur at greater rates during these times. Farther research should examine the human relationship between pEKFM and load across the entire range of weight on the bar from unloaded to 100%1RM.

Currently, the information in this study can be a useful guide to those involved in prescribing the squat practice. Progression can be maximized by incorporating the principle of "progressive overload," or the gradual increase of stress placed upon the torso (22), which should be considered when prescribing the squat exercise. In order to control for pEKFM while still working towards full range of movement move, these results suggest that a squat progression should first with unloaded above parallel squats and progress to deeper squats before the addition of load. Squat progression should over again go along from higher up parallel squats to deeper squats once a load has been added.

Every bit noted in Table 1, subjects only squatted to a consistent depth for the below parallel squat. This has important safety implications for the squat exercise. Considering that increased squat depth requires reduced loads, going below an intended depth may pb to a failed repetition and a potential increased risk of injury. When loads were increased to 85% 1RM, subjects squatted approximately 5–10° less during the above parallel and parallel squats. This may be done to subtract the difficulty of the exercise as loads become heavier. With below parallel squats where the thighs come into contact with the calves, in that location is a natural stopping point as a lower depth cannot exist achieved. This eliminates the possibility of unintentionally going beneath the intended depth where there is an increased probability of a failed repetition.

Although this report adds important insight into how load and depth impact forces nearly the knee, understanding the limitations of this study will allow for proper interpretation of the results. The retro-reflective marker movement that occurred with the deeper squats may have affected values reported in this study. As depth increased, the cluster of markers on the thigh became visibly plain-featured, potentially causing fault in the estimated human knee flexion bending. Due to the fact that changed dynamics calculations proceed upward from the human foot, error due to thigh deformation should accept had minimal effect on the estimation of pEKFM, but deformations of the foot or shank are a potential source of fault in pEKFM. Additionally, co-contraction from the hamstrings and gastrocnemius with the quadriceps was not considered. Co-contraction would crusade pPFJRF to increase without a change in the pEKFM, lessening the value of pEKFM as a surrogate. Optimal placement of markers on the thigh and pelvis as well as including the effects of co-contraction should be considered for hereafter studies.

All data were presented in response to one repetition for each given load and depth. Subjects were not in a fatigued state and therefore application of the results should be made accordingly. pEKFM will likely change as subjects become fatigued and their squat technique suffers.

Thigh-dogie contact generally occurs during deeper squat depths of approximately 130° of knee flexion. Thigh-calf contact produces a moment in the same direction as that of the quadriceps muscle group thereby decreasing the bodily cyberspace flexion moment at the knee, causing an overestimation of pEKFM in this study. Recent research has shown that tibiofemoral compressive force, shear forcefulness, and patellar tendon force decreased while squatting to full depth where thigh-dogie contact occurred (42). Hereafter studies should consider thigh-calf contact using force per unit area sensors or the like when examining knee forces during high flexion activities.

Generalizing the present results across immature, healthy, recreationally trained males should be done with care. A number of technique differences betwixt aristocracy powerlifters classified every bit low-skill or high-skill accept been previously found (26). Information technology remains unknown whether larger differences exist between elite and recreational weightlifters, or whether differences between males and females be in squatting mechanics. Moreover, the recreationally trained males in this study varied in their functioning of the squat. 4 of the subjects were not able to increment 1RM load as squat depth decreased from a below parallel to a parallel squat. Advanced lifters may show greater differences betwixt 1RM loads at varying depths, which could result in altered pEKFM. Subjects differing in historic period, gender, superlative, weight, experience level and wellness status may exhibit altered biomechanics in comparing to the presented results.

The main finding of this study is that the 1RM decreases seen with increasing depth are not enough to first the increases in pEKFM at loads consisting of unloaded, 50% 1RM and 85% 1RM. While progressing from unloaded to l% 1RM, slopes of pEKFM are lxx% greater than when progressing from 50% 1RM to 85% 1RM loads. To our knowledge this is the first study investigating pEKFM utilizing a range of typical loads and depths found in rehabilitation and functioning preparation settings. Health and fettle professionals are advised to use the data presented here in addition to private assessments to determine how to best comprise the squat exercise into rehabilitation and grooming programs.

PRACTICAL APPLICATIONS

The back squat is a commonly prescribed exercise due to its similarity to activities of daily living and many sporting activities too equally being a multi-joint movement incorporating large musculus groups. The hypotheses were that back squat 1RM would decrease with increased depth, and that this decreased 1RM would let pEKFM to remain constant for load- and depth-matched squats. However, reducing the load based on the subtract in 1RM was not enough to allow pEKFM to remain constant, i.e. a 50% 1RM squat to parallel yet resulted in greater pEKFM than a 50% 1RM squat to to a higher place parallel when utilizing the 1RM for each depth. Based on these findings, the professional designing a progression for a client should take into account the large increase in knee loading from an unloaded squat to a load consisting of a 50% 1RM, equally forces increase at the greatest rate during these loads. The largest forces about the knee were plant with the 85% 1RM load at the below parallel depth. Proper progressions should be designed to allow the client to adapt to the increasing forces at the articulatio genus. Close supervision and correct spotting techniques should be incorporated, specially at depths in which the thighs practice not come into contact with the calves, equally going below the intended depth may event in failed attempts. Given the age, gender, height, weight, feel level and health status of the subjects involved in this study, extrapolating the results to those with differing characteristics should be done charily. The information here should be used every bit a reference point for programme design involving the squat exercise later on a comprehensive individualized assessment has been completed.

Acknowledgments

The authors would similar to thank all the subjects for graciously volunteering their time and try. Additionally, the authors are grateful for the volunteer students and their tremendous aid in completing this report.

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Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4064719/

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