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A kinematic model of performance in the parallel squat by champion powerlifers

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Abstract

The purpose of this study was to formulate a kinematic model of performance in the parallel squat, based on the movement characteristics of world class powerlifters, and to determine if the model could be utilized to assess technique differences between high and less-skilled subjects. Two trials were recorded via high-speed cinematography from a side view of twenty-four Ss during the 1974 U.S. Senior National A.A.U. Powerlifting Championships. Vertical and horizontal displacement patterns of three joint centers and the center of the bar were determined for the best trial of each S. These data were subsequently used to calculate desired linear and angular coordinates, velocities and accelerations for body segments and bar. Results indicated that although there was some variability in most kinematic parameters, vertical bar velocity was found to be very similar among competitors, even for Ss of different bodyweight. Consequently, the vertical velocity of the bar was selected as the parameter around which performance could be modeled in the parallel squat. A model was formulated by plotting the mean values in vertical bar velocity for all Ss scaled to a common time base. The resultant model was contrasted with vertical bar velocity data for less-skilled Ss to assess typical performance errors.

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... Considering this complexity, it is of no surprise that a sticking point has been repeatedly observed in the squat in numerous studies. Indeed, in the academic literature, the phenomenon of the sticking point was first reported and studied in the squat [52]. In particular, McLaughlin et al. [52] examined kinematic characteristics of the squat performed by highly skilled powerlifters, and observed that the sticking point across the studied sample occurred at approximately a thigh angle relative to the ground of 30 . ...
... Indeed, in the academic literature, the phenomenon of the sticking point was first reported and studied in the squat [52]. In particular, McLaughlin et al. [52] examined kinematic characteristics of the squat performed by highly skilled powerlifters, and observed that the sticking point across the studied sample occurred at approximately a thigh angle relative to the ground of 30 . What is more, they observed a remarkable uniformity across the sample in this regard, as witnessed by the standard deviation of the angle of only AE2 . ...
... This interaction was examined in depth by Escamilla et al. [44], who also performed a stratification of the studied sample into three groups by their stance width (normalised by shoulder width): narrow, medium, and wide. The first interesting finding of this work is the much greater thigh angle at the sticking point than that reported by McLaughlin et al. [52] and Hales et al. [53]: approximately 49 . Also contrasting the findings summarised before, Escamilla et al. observed a significantly greater variability of the sticking point thigh angle across lifters of AEð5 -6Þ . ...
Article
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Ever since it was first observed and especially so in recent years, the phenomenon of the so-called "sticking point'" in resistance training has attracted a substantial amount of sports and exercise science research. Broadly speaking the sticking point is understood as the position in the range-of-motion of a lift at which a disproportionately large increase in the difficulty to continue the lift is experienced. Hence the sticking point is inherently the performance bottleneck and is also associated with an increased chance of exercise form deterioration or breakdown. Understanding the aspects of lifting performance which should be analysed in order to pinpoint the cause of a specific sticking point and therefore devise an effective training strategy to overcome it, is of pervasive importance to strength practitioners and instrumental for the avoidance of injury and continued progress. In this paper we survey a range of physiological and biomechanical mechanisms which contribute to the development of sticking points, and led by this insight review and analyse the findings of the existing observational research on the occurrence of sticking points in three ubiquitous exercises: the bench press, the squat, and the deadlift. The findings of our analysis should be used to inform future research and current resistance training practice.
... There is concern however, as to potential for injury during its performance (Lander et al., 1986). This potential for injury can be minimized by maintaining proper squatting form (Chandler & Stone, 1991;Escamilla & Krzyzewski, 2001;McLaughlin, Dillman, & Lardner, 1977). ...
... While the squat has been highly used in the conditioning of athletes, concerns have often been voiced as to its potential to cause injury (Lander et al., 1986). However, safety can be maximized through the use of correct form (Chandler & Stone, 1991;Escamilla & Krzyzewski, 2001;McLaughlin et al., 1977). Consequently, proper form should be taught to those who are learning the squat, so they can reap the benefits of performing this exercise while minimizing the risk of injury. ...
... As previously mentioned, squatting with proper form is very important (Chandler & Stone, 1991;Escamilla & Krzyzewski, 2001;McLaughlin et al., 1977). Consequently, the present section outlines twelve aspects of proper form for the squat as broken down by the author of this paper. ...
... This may indicate that when using an SS, which might restrict motion, it would possibly influence the use of additional hip musculature, thereby increasing force, velocity, and power. A study examining national level powerlifters in comparison to recreationally trained lifters indicated that powerlifters moved their knees anteriorly to a lesser degree and generated more knee extensor torque (9). Thus, restricted anterior motion of the knee, possibly as a result of using an SS, might increase the generation of both knee and hip torque. ...
... The SS allows for a higher velocity at all intensities compared with the NSS condition. These results coincide with past research (9) and the initial hypothesis that the suit would enhance these variables. Although there was a difference in peak concentric force within the 2 conditions, they were not significant. ...
... It is likely that the SS allowed the lifters to remain more upright during the squat relative to their hip position compared with the NSS squats that caused the anterior inclination of the torso (4) and possibly excess vertical displacement. McLaughlin et al. (9) found similar results when examining a highly trained powerlifter; they found that trunk, hip, and knee horizontal displacements were greater in the less skilled group and could elicit a decrease in performance. This suggests that SS helps to minimize these variables and help increase squatting performance. ...
Article
The purpose of this investigation was to examine various kinetic and kinematic variables associated with squats without and with the use of a squat suit. No previous investigation has examined the effect of a squat suit on squat performance. Participants were 8 elite or professional level male powerlifters (height = 178.59 ± 3.5 cm; body mass = 106.8 ± 30.4 kg; age = 25 ± 2.2 yrs; mean 1RM =197.7±53kg). Subjects participated in three testing sessions, with the first session involving a one repetition maximum squat (1RM) without a squat suit. Session two and three involved a testing session completing two trials in the squat at three intensities (80, 90, and 100% of 1RM) either without (NSS) or with a squat suit (SS). The session and order of the intensities were all randomized. Force-, velocity-, and power-time graphs were calculated from data from a force plate and two linear position transducers attached to the barbell. Peak eccentric force was significantly higher during SS at 100% of 1RM (NSS-100 = 3196.2 ± 470.6, SS-100 = 3369.7 ± 589.9 N). Peak concentric velocity was significantly higher during SS in comparison to NSS at all intensities. Peak concentric power was significantly higher during SS at 80% of 1RM (NSS-80 = 1566.5 ± 388.4 W, SS-80 = 1770.4 ± 483.2 W) and 90% of 1RM (NSS-90 = 1493.1 ± 296.2 W, SS-90 = 1723.8 ± 449.5 W). The current investigation has demonstrated significantly different kinetic and kinematic characteristics between squats without and with a squat suit which could ultimately aid in enhancing squat performance.
... The barbell back squat requires balance and stability to perform it symmetrically between the left and right sides of the body. Unlike gait studies with an extensive history of examining asymmetry issues, bilateral resistance exercises, such as the barbell back squat, are often assumed to be symmetrical between both sides of the body (3,8,16,17). ...
... The basic biomechanics of the barbell back squat were first analyzed among elite level power lifters over 3 decades ago (16,17). Typical image analysis at the time was a 2-dimensional (2D) approach to establish a baseline of biomechanical characteristics. ...
... Typical image analysis at the time was a 2-dimensional (2D) approach to establish a baseline of biomechanical characteristics. The barbell back squat is characterized as a sagittal plane movement and lower extremity joints are primary sources of the movement: dorsiflexing the ankle about 30°, flexing the knee to near 90°, and flexing the hip to a range of 85-110°as a lifter reaches peak descent position (3,8,16). Joint kinetic analyses were also performed to understand the mechanical loads in the lower extremity joints, and from those, the greatest joint torque was identified at the initiation of the ascent phase of the squat (6,17). ...
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The purpose of this study was to investigate the influence of weight distribution (WtD) asymmetry on the biomechanics of a barbell back squat. This study included 2 groups of trained individuals who were separated based on a WtD test (n = 14 in each group). They performed the barbell back squats with 2 resistance levels (60 and 75% of 1 repetition maximum) to measure vertical ground reaction force (GRF), tilting, and rotational angular bar displacements. A symmetry index (SI) score of the vertical GRF and the 2 bar displacements were examined to identify the group difference. Results showed that the unequal WtD group displayed a higher vertical GRF SI score (p < 0.05) and greater degrees of the tilting (p < 0.05) and rotational (p < 0.05) angular bar displacements. The 2 resistances did not influence the magnitude of the dependent variables, and no interactions were found. The unequal WtD captured at the WtD test carried over to the SI score during the back squat test. The unequal WtD was also a partial factor of displaying greater bar displacements. The lack of postural control to distribute body weight evenly should be treated properly to gain levelness before participating in high volume of resistance training, and coaches should be conscious of moving in a symmetrical fashion with minimal bar displacements in tilting and rotational manner.
... Numerous squat studies have been conducted to identify stress levels in the knee and low back area (6,8,9,21). Past biomechanics research on the barbell back squat analyzed mechanical differences between high-skilled and low-skilled powerlifters (19,20). More recent publications have examined a variety of biomechanical variables such as joint moments, mechanical powers, muscle activity, and trajectory of the barbell with various stance widths and intensity levels (6,8,18,27). ...
... One 60-Hz digital camera (PV-GS55, Panasonic, Osaka, Japan) was placed at a height of approximately 1.3 m and positioned 5 m to the left of a wooden platform to capture 2dimensional (2D) movements of each subject in the sagittal plane. Reflective markers were placed on the left side of each subject's fifth metatarsal joint (toe), lateral malleolus (ankle), lateral femoral epicondyle (knee), and greater trochanter (hip) (9,19,20). An additional marker was placed at the end of the barbell. ...
... These 5 points created segments of trunk, thigh, shank, and foot ( Figure 2). A segment from the hip to the end of the barbell was used to approximate the trunk segment because the end of the barbell is in a fixed position at the shoulder joint (9,19,20). The video data were directly imported into the Vicon Motus version 9.2 software (Centennial, CO, USA) for motion analysis. ...
Article
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The purpose of this study was to validate a higher degree of foot segment angle by wearing the weightlifting (WL) shoes and to determine the kinematic differences between WL shoes and running shoes during the barbell back squat. College-aged individuals volunteered to participate in this study (N = 25). After warm-up, subjects performed 60% of 1RM barbell back squat. Reflective markers were placed on lower extremity joints and end of the bar to create segments to analyze kinematics of the barbell back squat from a 2-dimensional view. Three separate repeated measure analyses of variance were used at p = 0.05. Results showed that there was a difference between the footwear conditions; foot segment angle of 3.5° (p < 0.05) and trunk lean of 22 mm (p < 0.05) were captured when wearing WL shoes. However, thigh segment peak flexion angle was not statistically different (p = 0.37). Wearing WL shoes seems to be beneficial in reducing the overall trunk lean, because this position is believed to reduce the amount of shear stress in the lower back area. Back squat with WL shoes also increased foot segment angle and possibly contributes to greater muscle excitation in knee extensors. Weightlifting shoes did not help reach thigh segment closer to horizontal as compared with the running shoe condition. It is recommended that WL shoes be used by those who are prone to displaying a forward trunk lean and who aim to increase knee extensor activation.
... Previous literature in the area of powerlifting focuses on knee mechanics because an elevated risk of injury to this area exists (3,10). Mechanical effectiveness is related to an individual's experience and can be determined with a biomechanical analysis among groups with different skill levels (4,8,9). Squat technique may determine victory in a powerlifting competition and may predispose an athlete to injury. ...
... The current study revealed that patterns of performance differ among groups with different skill levels. McLaughlin et al. (9) substantiated these patterns in prior research. The authors proposed that a model of performance of highly and less skilled powerlifters should be determined to have a better understanding on how to maximize performance for competition and to determine ''typical'' errors for various skill levels for improved safety. ...
... However, the knee joint angular velocity for the descent and ascent was examined, rather than vertical bar velocity. In addition, McLaughlin et al. (9) found that trunk, hip, and knee horizontal displacements were greater in the less skilled group. In the current research, relative knee angular displacement was considered, and the less skilled group had a greater knee angular displacement when compared with the highly skilled group. ...
Article
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The purpose of this study was to measure and analyze kinematic differences between competitive collegiate (CLG, n = 9) powerlifters, competitive high school (HS, n = 9) powerlifters, and novice (NV, n = 11) powerlifters during a maximal squat to determine the effect of skill level on performance. All powerlifters performed 3 squats, with the final squat being their 1 repetition maximum. Kinematic data (descent, ascent, total lift times, knee angle magnitude, knee angular velocity, and knee angular acceleration) was measured using 2-dimensional motion analysis equipment. Differences in mean peak kinematic values between the 3 groups were analyzed using a 1-way multivariate analysis of variance, p <or= 0.05. Differences were found between the NV and HS in the time to ascent, the total lift time, the normalized time to peak (NTTP) in knee angular velocity from the "sticking point" to the "lockout," and the NTTP in knee angular acceleration during the ascent. A difference was found between the CLG and HS in the peak knee angular velocity between the bottom of the lift and the sticking point. Differences were also found in the rate of acceleration upward after coming out of "the hole" between the CLG and NV and CLG and HS. A difference was found in the rate of peak deceleration upward to the sticking point between the CLG and NV. To avoid injury and to achieve optimum results in powerlifting, lifting technique must be optimized. The HS and NV accumulated several significant differences in NTTP during the ascending phase. However, the major finding between the 3 groups was in the rate of acceleration upward after coming out of the hole. Coaches should focus their training programs on increasing strength in unskilled powerlifters for the purpose of increasing acceleration from the bottom of the lift.
... Because segment and barbell accelerations are very small while lifting maximum or near maximum loads, joint moments can accurately be calculated using quasi-static models (12,14,18,19,21). Lander et al. (14) found that joint moments varied less than 1% between quasi-static and dynamic analyzes during the squat exercise with near maximum loads. ...
... Nevertheless, the amount of bend in the bar was minimal. The vertical bar velocity curve shown in Figure 3 is the same general pattern observed during maximum or near maximum loads during the squat (18), but different than the vertical bar velocity curve presented by McGuigan and Wilson (17). This discrepancy in the deadlift may be due the fact that the lifters in McGuigan and Wilson (17) completed the deadlift in approximately half the time it took the lifters in the current study ( Table 3). ...
... From Table 4, the mean 1st peak bar velocity was approximately 40 -50% greater than the mean 2nd peak bar velocity. These data are different compared to a 1 RM squat (18), in which lifters typically reached their maximum vertical bar velocity at their 2nd peak vertical bar velocity. During the 1 RM squat, the mean 2nd peak bar velocity was approximately 40 -50% greater than the mean 1st peak bar velocity (18), which is opposite the findings from the current study. ...
Article
Strength athletes often employ the deadlift in their training or rehabilitation regimens. The purpose of this study was to quantify kinematic and kinetic parameters by employing a three-dimensional analysis during sumo and conventional style deadlifts. Two 60-Hz video cameras recorded 12 sumo and 12 conventional style lifters during a national powerlifting championship. Parameters were quantified at barbell liftoff (LO), at the instant the barbell passed the knees (KP), and at lift completion. Unpaired t-tests (P < 0.05) were used to compare all parameters. At LO and KP, thigh position was 11-16 degrees more horizontal for the sumo group, whereas the knees and hips extended approximately 12 degrees more for the conventional group. The sumo group had 5-10 degrees greater vertical trunk and thigh positions, employed a wider stance (70 +/- 11 cm vs 32 +/- 8 cm), turned their feet out more (42 +/- 8 vs 14 +/- 6 degrees). and gripped the bar with their hands closer together (47 +/- 4 cm vs 55 +/- 10 cm). Vertical bar distance, mechanical work, and predicted energy expenditure were approximately 25-40% greater in the conventional group. Hip extensor, knee extensor, and ankle dorsiflexor moments were generated for the sumo group, whereas hip extensor, knee extensor, knee flexor, and ankle plantar flexor moments were generated for the conventional group. Ankle and knee moments and moment arms were significantly different between the sumo and conventional groups, whereas hip moments and moments arms did not show any significantly differences. Three-dimensional calculations were more accurate and significantly different than two-dimensional calculations, especially for the sumo deadlift. Biomechanical differences between sumo and conventional deadlifts result from technique variations between these exercises. Understanding these differences will aid the strength coach or rehabilitation specialist in determining which deadlift style an athlete or patient should employ.
... Given the widespread use of the squat among athletes, there are several studies that have analyzed the biomechanics of the gesture with the aim of improving performance and preventing injuries (1,3,(12)(13)(14)(15)(16)(17)(18). In fact, it is recommended to perform the squat, which is a closed kinetic chain exercise, with minimal anterior knee displacement in order to optimize performance and reduce the risk of injury (19)(20)(21)(22). ...
... The forward tilt of the trunk also allows a greater contribution from the back muscles. However, some studies have shown that experienced squatters can achieve better results and more favorable kinematics by keeping the trunk more upright (14,29). ...
Article
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Introduction: This study aimed to evaluate the angular kinematics of the hip, knee, ankle, and the linear kinematics of the barbell during the back squat (BS) at different load intensities in powerlifters and weightlifters. Methods: Seventeen athletes were recruited (n = 14 powerlifters; n = 3 weightlifters). The 1-RM of the BS of each participant was calculated and, 1-week after, each participant was asked to perform 5 trials of the BS at different load intensities (i.e., 60%, 70%, 80%, 90%, 100%) of the 1-RM. An action camera recorded the execution of each BS trial in the sagittal plane and, afterward, the videos were analyzed by measuring the range of motion (ROM) of hip, knee, and ankle for the angular kinematics, and the timing, distances, speeds, and accelerations of the barbell for the linear kinematics. Results: Regarding the angular kinematics, no significant differences were found in the parameters in the starting and ending positions among the 5 trials, while a significant decrease was found in the hip relative angle (p = 0.026) in the maximum flexion position as load intensity increased. Regarding the linear kinematics, a significant difference was found in the descent acceleration (p = 0.049) in the descent phase, while a significant difference was found in the ascent speed (p < .001) and vertical speed of ascent (p < .001) in the ascent phase, which decreased as load intensity increased. Discussion: Our findings show that the angular and linear kinematics of BS change as load intensity increases.
... According to this traditional dogma, anterior knee movement should be limited in the sagittal plane once a vertical line with the tips of the feet is achieved [1,2]. Widely accepted instructions for proper knee positioning during barbell squats [2,3] are based on previous studies [4][5][6] that showed that anterior knee displacement (AKD) past the toes is associated with greater shearing forces in the knees, specifically the tibiofemoral joints [4], and that moving the knees anteriorly to a lesser extent during squatting generates lower knee extensor torque [5]. Based on these findings, it has become standard practice to maintain the shin as vertical as possible and that "maximal forward movement of the knees should place them no more than slightly in front of the toes" when squatting in order to lessen the shear stress placed on the knee [3]. ...
... Restricting the natural AKD leads to altered knee-hip coordination [6], which is associated with increased trunk flexion in the thoracic and lumbar spine [10]. This form of evasive movement can lead to increased tensile stress on the intervertebral ligaments [35,36] and has been consequently discouraged by various authors [37,38]. ...
Article
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Based on seminal research from the 1970s and 1980s, the myth that the knees should only move as far anterior during the barbell squat until they vertically align with the tips of the feet in the sagittal plane still exists today. However, the role of both the hip joint and the lumbar spine, which are exposed to high peak torques during this deliberate restriction in range of motion, has remained largely unnoticed in the traditional literature. More recent anthropometric and biomechanical studies have found disparate results regarding anterior knee displacement during barbell squatting. For a large number of athletes, it may be favorable or even necessary to allow a certain degree of anterior knee displacement in order to achieve optimal training outcomes and minimize the biomechanical stress imparted on the lumbar spine and hip. Overall, restricting this natural movement is likely not an effective strategy for healthy trained individuals. With the exception of knee rehabilitation patients, the contemporary literature suggests it should not be practiced on a general basis.
... Resistance training programs involve methods used to increase force and power output (Haff et al., 2001;Kraemer et al., 2002;Zink et al., 2006;Reid et al., 2012;Straight et al., 2016). The squat is one of the most frequently used exercises for the development of strength and power of the lower limb muscles (McLaughlin et al., 1977;Rahmani et al., 2001;Kellis et al., 2005;Schoenfeld, 2010;Buzgó et al., 2014;Vecchio, 2018). The biomechanics of squatting has a lot in common with components of everyday movements, such ascending and descending stairs, sitting down, and standing up, and it has its place in the field of rehabilitation (Lynn et al., 2012;List et al., 2013;Buzgó et al., 2014;Lorenzetti et al., 2018;Vecchio, 2018). ...
... Conversely, if the lift focuses on maximum force production to elicit an increased motor unit recruitment, the maximal velocity is compromised (Hutschison et al., 2019). Peak force (acceleration) has been shown to occur at the onset of the concentric action (McLaughlin et al., 1977;Elliott et al., 1989), which thus leads to more variation in the force curve, greater changes in momentum (Cronin et al., 2001) and, thus, may be one of the reasons for an extended deceleration phase. The point of the concentric phase at which peak velocity occurs is reduced with a decrease in load. ...
Article
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The purpose of this study was to compare the stability of the range of squat motion and the efficiency of the bottom position of squatting among athletes of different squat performancelevels. Two groups of trained male subjects, non-squatters (NS G ; n=24; age=22.6±2.8 y; body height (BH)=180.5 ± 6.5 cm; body weight (BW)=75.4 ± 11.3 kg) and squatters (S G ; n=19; age=24.3±1.2 y; BH=183.2 ± 4.4 cm; BW=85.5 ± 10.9 kg), performed a progressive loading diagnostic test duringa high-bar back squat with a calf raise via a linear position transducer and dynamometricforce plate. The load was derived from the BW of a subject (0-100% of BW). The stability of the range of squat motion and the efficiency of the bottom position of the squat was measured by parameters such as the eccentric range of squat motion related to BH, the variation coefficient of eccentric range of motion (ROM), and power output during the concentricand the acceleration phases. Significant differences between groups were found in the eccentric range of squat motion and in the eccentric range of squat motion related to BH with a greater range of motion for S G. The NS G group showed a significantly greater variation in the coefficient of eccentric range of squat motion and the percentage shift of the peak force during the concentric phase. The mean power outputs during the concentric and acceleration phases and peak force production during the concentric phase were significantly greater for S G. There was a significantly greater force by the athletes and barbell (F W) and peak force ratio forthe bottom position of the squat (Fmax BPS) for the S G in favour of Fmax BPS for each load. For the F W and peak force during the concentric phase (Fmax CONC) ratio, significant differences between groups were also observed for each load with a larger ratio for S G in favour of Fmax CONC. Our results suggest that a person who effectively masters the squat can subsequently generate greater force and higher power output during the concentric and the acceleration phases of a squat. We also predict more stable ROM when performing a squat, especially when increasing external resistance, which can contribute to reducing the risk of injury during the training process.
... More specifically, skilled competitive collegiate powerlifters have been shown to display significantly longer time to descent and significantly higher knee peak angular velocity between the bottom of the lift and the sticking point compared to competitive high school powerlifters and novice powerlifters (Miletello, Beam, & Cooper, 2009). These results are further supported by the work of McLaughlin et al. that also show a longer descent time in world-class powerlifters as compared to less skilled powerlifters (McLaughlin, Dillman, & Lardner, 1977). Collectively, this points towards the importance of acknowledging inter-individual differences in the execution of the back squat exercise, as this may contain important information that can be used in the process of performance optimization. ...
... All participants demonstrated a clear double peak in vertical barbell velocity during the concentric phase and achieved the maximum vertical barbell velocity at the second peak, which is similar to previous results (Escamilla et al., 2001;McLaughlin et al., 1977). Similarly, when we correlated the trials obtained at 90% of 1RM with the 1RM trial, we found good to very good correlation coefficients. ...
Article
The purpose of this study was to explore the level of inter- and intra-individual variability in the kinematic profiles of the back squat movement among skilled weightlifters. Ten competitive weightlifters volunteered for participation in this study. Barbell velocity (VBarbell) and angular velocity of the ankle (ωAnkle), knee (ωKnee) and hip joint (ωHip) were obtained by kinematic recording of six trials at 90% of 1RM in the back squat. Inter-individual variability was assessed by analysing inter-individual differences in the velocity curves through the statistical parametric mapping method. Intra-individual variability was assessed through a correlation analysis between the barbell velocity curves of each trial for each participant. Partial least squares regression analysis, was performed to relate changes in intra-individual variability to movement and anthropometric characteristics. Significant inter- and intra-individual differences were identified in VBarbell, ωAnkle, ωKnee, and ωHip (p ≤ 0.05). Having a short trunk and thigh, and a long shin in combination with greater anterior-posterior displacement of the barbell and slower velocities during the acceleration phase increased intra-individual movement consistency over movement variability. The results of the present study clearly demonstrate that skilled weightlifters display both significant inter- and intra-individual variability in the successful execution of the back squat.
... These factors may contribute to understanding why the LBBS might allow for greater loads to be lifted. However, these joint angle results are not definitive, and there are mixed results in the literature for the size of HBBS and LBBS trunk angles at peak hip flexion (Donnelly, Berg, & Fiske, 2006;Escamilla et al., 2001;Flanagan & Salem, 2007;Hales, Johnson, & Johnson, 2009;Hooper et al., 2014;Kobayashi et al., 2010;McKean, Dunn, & Burkett, 2010;McLaughlin, Dillman, & Lardner, 1977;Swinton, Lloyd, Keogh, Agouris, & Stewart, 2012) (Tables 1 and 2). Lastly, it is common for Olympic weightlifters and powerlifters to wear special weightlifting/squat shoes/boots when performing the BBS (International Weightlifting Federation, 2015;Sato, Fortenbaugh, & Hydock, 2012;Sato, Fortenbaugh, Hydock, & Heise, 2013). ...
... These factors may contribute to understanding why the LBBS typically allows for greater loads to be lifted. However, these kinematic findings are not definitive and there are mixed results in the literature for the size of HBBS and LBBS trunk angles at peak hip flexion(Donnelly, Berg, & Fiske, 2006;Escamilla et al., 2001;Flanagan & Salem, 2007;Hales, Johnson, & Johnson, 2009;Hooper et al., 2014;Kobayashi et al., 2010;McKean, Dunn, & Burkett, 2010;McLaughlin, Dillman, & Lardner, 1977; Swinton, Lloyd, Keogh, Agouris, & Stewart, 2012). Similarly, no conclusive differences between the HBBS and LBBS ankle joint angles can be drawn, in reference to prior literature(Flanagan & Salem, 2007;Hales, Johnson, & Johnson, 2009;Kobayashi et al., 2010;Sato, Fortenbaugh, & Hydock, 2012; Swinton, Lloyd, Keogh, Agouris, & Stewart, 2012).As the position of the barbell on the trapezius influences the joint angles of the BBS, there is also a resultant influence on the GRF produced. ...
Thesis
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The barbell back-squat is one of the most common exercises in strength and conditioning practice; especially in Olympic weightlifting and powerlifting. There are two main bar placements within the back-squat; the high-bar and low-bar positions. The high-bar position, favoured by Olympic weightlifters, closely resembles the upright body position of the two competition lifts of the sport; the snatch and clean and jerk. The low-bar position, favoured by powerlifters, typically allows greater loads to be lifted by utilising the posterior-chain musculature during the back-squat (one of the three competition lifts in the sport). Unfortunately, little research exists comparing the high-bar back-squat with the low-bar back-squat, and no research has examined either lift above 90% of one repetition maximum. Furthermore, no authors have biomechanically compared the high-bar back-squat to the Olympic lifts (e.g. snatch and clean and jerk). The aims of this thesis were to (1) review the current literature and quantitatively assess the kinetic and kinematic findings among the limited research; (2) compare and contrast the high-bar back-squat and low-bar back-squat up to maximal effort; and (3) assess the differences and/or similarities between the high-bar back-squat and the Olympic lifts. Through an extensive literature review, the high-bar back-squat was found to commonly present a larger hip angle, smaller knee angle and equivalent ankle angle compared to the low-bar back-squat; inferring the high-bar placement creates a more upright truck position for the lifter and requires more quadriceps muscle activation. Experimentally, these findings were confirmed with the high-bar back-squat producing larger hip angles and smaller knee angles compared to the powerlifters (16–21% larger and 10–12% smaller, respectively) and low-bar controls (16–21% larger and 10–12% smaller, respectively). While the Olympic weightlifters and powerlifters lifted similar relative loads, the low-bar controls were able to lift 2.5–5.2% larger relative loads compared to the high-bar controls. As expected, the high-bar back-squat also showed similar kinematics to the snatch and the clean but substantially different kinetics across all loads lifted. Performing a back-squat with a low-bar placement, situates the lifter (advanced and recreational) in a stronger position to lift larger loads compared to the high-bar placement. The establishment of a more advantageous kinematic posture during the low-bar back-squat could potentially maximise the utilisation of the stronger posterior hip musculature thus increasing the stability and moment arm at the hip. The low-bar back-squat therefore appears to provide the best chance of lifting the largest relative load. The kinematic similarities in posture between the high-bar back-squat and the Olympic lifts suggests the potential of similar trunk, hip and thigh muscular activity of key stabilising muscles and repetitive positional alignment in the “catch” position. The differing kinetics however, are more likely due to technical differences between the high-bar back-squat, snatch and clean; wherein the Olympic lifts require additional elements of upper-body strength and stability. The high-bar back-squat does appear to yield an efficient carryover to the Olympic lifts as a suitable supplementary exercise; provided the technical components of the lifts are maintained.
... However, improvements in resistance training are not solely explained by increases in muscular strength (24). Consequently, a skill component to resistance training must also be considered for performance gains (18,24). The purpose of this article is to examine evidence for a skill component to resistance training and provide practical suggestions for coaching resistance exercises. ...
... Currently, the literature on the role of learning in complex resistance training exercises such as the squat, hang clean, snatch, deadlift, bench press, overhead press, or pullups is lacking. However, McLaughlin et al. (18) observed that among very experienced powerlifters, it is possible to distinguish athletes as highly skilled or less skilled. The most skilled lifters were able to maintain a better biomechanical position throughout the lift. ...
Article
ENHANCED MUSCULAR STRENGTH IS BENEFICIAL TO ATHLETES BECAUSE OF IMPROVED RATE OF FORCE DEVELOPMENT. FOR ATHLETES TO PROGRESS IN RESISTANCE TRAINING, IT IS OF PARAMOUNT IMPORTANCE THAT PROPER FORM IS TAUGHT. THERE ARE MANY ASPECTS OF WEIGHT LIFTING THAT CONTRIBUTE TO SUCCESSFUL PERFORMANCE. HAVING PROPER FORM IS ONE OF THESE ASPECTS. IT IS THE COACH'S JOB TO TEACH RESISTANCE TRAINING EXERCISES THAT REQUIRE SKILL AND ALSO TO MAXIMIZE PERFORMANCE FOR THE EXERCISES THEY ARE TEACHING. THIS REVIEW COVERS EXERCISE SELECTION, MODELING, FOCUS OF ATTENTION, AND AUGMENTED FEEDBACK FOR THE SPORT AND PERFORMANCE COACH.
... Both experience (Chandler & Stone, 1991;Dunn et al., 1984;McLaughlin, Dillman & Lardner, 1977, McLaughlin et al., 1978 and sex (Fry, Housh, Hughes & Eyford, 1988;Fry, Kraemer, Bibi & Eyford, 1991;Lynn & Noffal, 2012;McKean et al., 2010a;McKean, Dunn & Burkett, 2010b) have been demonstrated to influence squat technical models, and also responses to loading (McKean et al., 2010a). With this in mind it would seem unlikely that WS would offer the same outcome for all athletic groups. ...
... Consequently, a trunk lean strategy is necessary to maintain their centre of mass over their base of support to avoid falling, a common error observed in novice populations during the squat (Chandler & Stone, 1991;Dunn et al., 1984;McLaughlin et al., 1977). The differences in squat kinematics suggest that the novice group may adopt a trunk lean strategy at a reduced squat depth when compared to experienced lifters. ...
Article
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Weightlifting shoes (WS) are often used by athletes to facilitate their squat technique; however, the nature of these benefits is not well understood. In this study, the effects of footwear and load on the mechanics of squatting were assessed for 32 participants (age: 25.4 ± 4.4 years; mass 72.87 ± 11.35 kg) grouped by sex and experience. Participants completed loaded and unloaded back squats wearing both WS and athletic shoes (AS). Data were collected utilising a 3D motion capture system synchronised with a force platform and used to calculate kinematic and kinetic descriptors of squatting. For both load conditions, WS gave significantly (P < 0.05) reduced ankle flexion and increased knee flexion than AS, as well as a more upright trunk and greater knee moment for the unloaded condition. In addition, the experienced group experienced a significantly greater increase in knee and hip flexion with WS than the novices when unloaded. These results are consistent with the idea that WS permit a more knee flexed, upright posture during squatting, and provide preliminary evidence that experienced squatters are more able to exploit this effect. Decisions about footwear should recognise the effect of footwear on movement and reflect an athlete's movement capabilities and training objectives.
... Similar findings were reported by Behrens et al. [50] who showed that caffeine consumption increased power performance of the plantar flexor muscles but did not increase MVC strength. One plausible reason may be that maximal and near-maximal squat performance is limited by the sticking region (area where bar velocity is minimal) located superior to the bottom parallel position close to an absolute thigh angle of approximately 30° [ 51]. Surpassing the sticking region increases the likelihood of completing a successful repetition as bar velocity increases during the remainder of the range of motion until the deceleration phase ensues [51]. ...
... One plausible reason may be that maximal and near-maximal squat performance is limited by the sticking region (area where bar velocity is minimal) located superior to the bottom parallel position close to an absolute thigh angle of approximately 30° [ 51]. Surpassing the sticking region increases the likelihood of completing a successful repetition as bar velocity increases during the remainder of the range of motion until the deceleration phase ensues [51]. Although power and velocity were higher during each repetition, it is possible the greater power did not transfer through the sticking region when fatigue reached maximal levels. ...
Article
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Background: Little is known concerning the potential ergogenic effects of p-synephrine supplementation. Therefore, the purpose of the present study was to examine the effects of supplementation with p-synephrine alone and in combination with caffeine on free-weight resistance exercise performance. Methods: Twelve healthy, college-aged men performed a control (CT) resistance exercise protocol consisting of 6 sets of squats for up to 10 repetitions per set using 80 % of their one repetition-maximum (1RM) with 2 min of rest in between sets. Each subject was randomly assigned (in double-blind, balanced manner) to a treatment sequence consisting of use of 3 supplements: p-synephrine (S; 100 mg), p-synephrine + caffeine (SCF; 100 mg of p-synephrine plus 100 mg of caffeine), or a placebo (P). For each supplement treatment (separated by 1 week), subjects consumed the supplement for 3 days prior to each protocol and the morning of each protocol, and subsequently did not consume any supplements for 3 days following (i.e. wash-out period). On each protocol day, subjects reported to the lab at a standard time, consumed a supplement, sat quietly for 45 min, performed the resistance exercise protocol, and sat quietly for 30 min post exercise. Performance (repetition number, force, velocity and power), blood lactate, and ratings of perceived exertion (RPE) data were collected during each protocol. Results: Supplements SCF and S produced a significantly (P < 0.05) greater number of repetitions performed than CT (by 11.0 ± 8.0 %) and P (by 6.0 ± 7.0 %) and a 10.6 ± 12.0 % greater increase in volume load per protocol than CT and P. Most of the differences were seen during the last 3 sets. Mean power and velocity for all 6 sets were significantly higher in SCF compared to CT and P by ~6.2 ± 8.0 %. No supplement effects were observed in RPE or blood lactate, and no adverse side effects were observed or reported. Conclusions: S and SCF augmented resistance exercise performance (total repetitions, volume load) without increasing blood lactate or RPE. The addition of caffeine in SCF increased mean power and velocity of squat performance. These results indicate supplementation with S and SCF can enhance local muscle endurance during resistance exercise.
... Unlike clinical analysis of gait, bilateral resistance exercises, such as the back squat, were assumed to be symmetrical for years (Donnelly, Berg, & Fiske, 2006;Fry, Smith, & Schilling, 2003;McLaughlin, Dillman, & Lardner, 1977). The exercise is used to increase muscular strength in the lower extremity and trunk, and it requires balance and stability to perform it symmetrically between the left and right sides of the body without compromising unwanted bar movement. ...
... The exercise is used to increase muscular strength in the lower extremity and trunk, and it requires balance and stability to perform it symmetrically between the left and right sides of the body without compromising unwanted bar movement. The back squat is predominantly a sagittal plane exercise with about 30 degrees (°) of ankle dorsiflexion, near/over 90° of knee flexion, depending on the depth of the squat, and 85 to 110° of hip flexion (Donnelly et al., 2006;Fry et al., 2003;McLaughlin et al., 1977). Along with the kinematics of the lower extremity, other studies addressed joint torques, mechanical powers, and superficial muscle activities (Escamilla, Fleisig, Lowry, Barrentine, & Andrews, 2001;Zink, Perry, Robertson, Roach, & Signorile, 2006). ...
Conference Paper
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The aim of the study was to analyze the ML knee displacement and its influence on barbell tilt and rotation displacement from the back squat. Based on the weight distribution (WtD) test, 13 were in the equal WtD group and 14 were in the unequal WtD group. All subjects performed 75% of 1RM barbell back squat with reflective markers on selected locations for motion analysis. Medial-lateral (ML) knee displacement, barbell tilt and rotation displacements were considered. The results showed a statistically significant difference between groups (p<0.01), but no significant difference in ML knee displacement of the left and right sides (p=0.63). There were no correlations between ML knee displacement asymmetry and barbell tilt (p=0.12) and rotational displacement (p=0.07), indicating frontal knee action may not explain unwanted barbell movements in back squat. INTRODUCTION: Unlike clinical analysis of gait, bilateral resistance exercises, such as the back squat, were assumed to be symmetrical for years (Donnelly, Berg, & Fiske, 2006; Fry, Smith, & Schilling, 2003; McLaughlin, Dillman, & Lardner, 1977). The exercise is used to increase muscular strength in the lower extremity and trunk, and it requires balance and stability to perform it symmetrically between the left and right sides of the body without compromising unwanted bar movement. The back squat is predominantly a sagittal plane exercise with about 30 degrees (°) of ankle dorsiflexion, near/over 90° of knee flexion, depending on the depth of the squat, and 85 to 110° of hip flexion (Donnelly et al., 2006; Fry et al., 2003; McLaughlin et al., 1977). Along with the kinematics of the lower extremity, other studies addressed joint torques, mechanical powers, and superficial muscle activities (Escamilla, Fleisig, Lowry, Barrentine, & Andrews, 2001; Zink, Perry, Robertson, Roach, & Signorile, 2006). However, practitioners are also interested in other components of the squat kinematics such as frontal plane motion of the knee. After observing how strength and conditioning and weightlifting coaches check their athletes' technique, it appears that many of them use a frontal and/or diagonal position to check lifting technique, including the motion of the knee. From scientific literature, a study reported knee varus and valgus motions activate knee extensor muscles differently (Sogabe, 2009), but no further information on the threshold of the knee varus and valgus range of motion was discussed. Based on the practitioners' viewpoint as well as recent scientific study, it is speculated that carefully observing frontal plane knee kinematics may have an important role on detecting other portions of unwanted movement from the barbell back squat. The current literature, however, has not established a normal range of frontal plane knee displacement and the consequences of that motion on the back squat. Practitioners would then be better prepared to observe and comment on knee motion during the back squat. Therefore, the purpose of the study was to analyze the medial-lateral (ML) knee displacement characteristics from populations who display equal weight distribution (WtD) and unequal WtD to determine if a difference exists. Further analysis was done by investigating the relationship between the level of knee displacement asymmetry and barbell tilt and rotation during the barbell back squat. The study hypothesized; a) similar ML knee displacement from left and right sides are present from equal WtD group, but not from unequal WtD group, b) unequal WtD group who displays unequal ML knee displacement between left and right sides would be related to higher barbell tilt and rotation during the back squat. The significance of the study
... However, other health professionals whose primary focus is rehabilitation after knee injury list the deep squat as a contraindicated exercise (5) and recommend performing the squat exercise with limited knee flexion due to the commonly held belief that the squat exercise may elicit dangerously high forces on the knee (15,29). In spite of the large body of work performed studying the squat exercise (4,6,9,11,19,26,29,30,32,33,35,36,38,41,42), it remains difficult to reconcile the differences in recommendations between these two schools of thought due to lack of a comprehensive study comparing squats as recommended by both (11,29). ...
... Generalizing the present results beyond young, healthy, recreationally trained males should be done with care. A number of technique differences between elite powerlifters classified as low-skill or high-skill have been previously found (26). It remains unknown whether larger differences exist between elite and recreational weightlifters, or whether differences between males and females exist in squatting mechanics. ...
Article
Controversy exists regarding the safety and performance benefits of performing the squat exercise to depths beyond 90° of knee flexion. Our aim was to compare the net peak external knee flexion moments (pEKFM) experienced over typical ranges of squat loads and depths. Sixteen recreationally trained males (n = 16; 22.7 ± 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 least one year of consistent resistance training experience while utilizing the squat exercise performed single repetition squat trials in a random order at squat depths of above parallel, parallel, and below parallel. Less than one week before testing, one repetition maximum (1RM) values were found for each squat depth. Subsequent testing required subjects to perform squats at the three depths with three different loads: unloaded, 50% 1RM, and 85% 1RM (nine total trials). Force platform and kinematic data were collected to calculate pEKFM. To assess differences among loads and depths, a two-factor (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 above parallel to parallel squat and another 3.6% from the parallel to the below parallel squat (P < 0.05). Net peak external knee flexion moments significantly increased as 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 enough to offset increases in pEKFM.
... To perform a comparative analysis, a common phenomenon specific to each of the individual lift types was needed to serve as a marker for distinguishing differences between the lifts. The event, described as the ''sticking point,'' was selected because it has been reported to occur in various weight lifting movements, including the back squat and the deadlift (6,15,16). The sticking point of a movement is where the upward momentum of the barbell is momentarily decreased or stopped. ...
... Bar velocities quantified during the ascent phase of the squat implies the net extensor moment is diminished at the ''sticking point'' region ( Figure 1). In addition, the mean absolute knee angle (Table 3) reported at the sticking point is similar to past research findings (16). ...
Article
Many individuals involved in the sport of powerlifting believe that the squat and deadlift have such similar lifting characteristics that the lifts yield comparable training results. The aim of this study was to compare and contrast biomechanical parameters between the conventional style deadlift and the back squat performed by 25 lifters competing in regional powerlifting championship. The 3-dimensional analysis incorporated 4 60 Hz synchronized video cameras for collecting data from 25 participants. Parameters were quantified at the sticking point specific to each lift. Kinematic variables were calculated at the hip, knee, and ankle. Paired (samples) t-tests were used to detect significant differences in the kinematic mean scores for the different lift types. The statistical analysis revealed significant differences exist between the squat (0.09 m/s) and the deadlift (0.20 m/s) vertical bar velocities. Differences were found for angular position of the hip, knee, and ankle between lifts. The sticking point thigh angles were quantified as 32.54 +/- 3.02 and 57.42 +/- 4.57 for the squat and deadlift, respectively. Trunk angles were 40.58 +/- 6.29 (squat) and 58.30 +/- 7.15 (deadlift). The results indicate the back squat represents a synergistic or simultaneous movement, whereas the deadlift demonstrates a sequential or segmented movement. The kinematic analysis of the squat and the conventional deadlift indicate that the individual lifts are markedly different (p < 0.01), implying that no direct or specific cross-over effect exists between the individual lifts.
... The squatting exercise, performing a knee bend while carrying a weight on the shoulders, is an often used and important method for hip, knee, and back muscle training (3,18,22,23). Many athletes in different disciplines use this type of exercise as the basic exercise to strengthen the leg muscles, and the method is considered supreme for this purpose by many coaches (4,29). ...
... The patello-femoral compression force was calculated to give an apprehension of the force magnitudes. Forces in the hip and knee depend not only on the moment of force, but also on joint angle (22,24,25). For a constant moment of force joint compression forces increase with increasing flexion angle. ...
Article
Eight Swedish national class weightlifters performed "high-bar" squats and six national class powerlifters performed "low-bar" squats, with a barbell weight of 65% of their 1 RM, and to parallel- and a deep-squatting depth. Ground reaction forces were measured with a Kistler piezo-electric force platform and motion was analyzed from a video record of the squats. A computer program based on free-body mechanics was designed to calculate moments of force about the hip and knee joints. EMG from vastus lateralis, rectus femoris, and biceps femoris was recorded and normalized. The peak moments of force were flexing both for the hip and the knee. The mean peak moments of force at the hip were for the weightlifters 230 Nm (deep) and 216 Nm (parallel), and for the powerlifters 324 Nm (deep), and 309 Nm (parallel). At the knee the mean peak moments for the weightlifters were 191 Nm (deep) and 131 Nm (parallel), and for the powerlifters 139 Nm (deep) and 92 Nm (parallel). The weightlifters had the load more equally distributed between hip and knee, whereas the powerlifters put relatively more load on the hip joint. The thigh muscular activity was slightly higher for the powerlifters.
... 4 The comparison of the performance of world-class and less experienced athletes of powerlifting revealed that more skilled athletes also take longer to descend, indicating more control. 4,41 ...
Article
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Background It is important to assess the quality of fundamental movements, to discover deficits, evaluate mobility, balance, and stability, and identify movement dysfunction and asymmetries. However, little research has been performed on the assessment of fundamental movements with bodybuilders. Purpose The purpose of this research was to examine the quality of professional and amateur bodybuilders’ functional movements and the quality of the back squat performance. A secondary purpose was to discern whether greater experience in bodybuilding was associated with better scores on the back squat assessement (BSA). Study design Cross-Sectional Cohort Methods Twenty-six athletes were recruited to participate. The group of professional bodybuilders consisted of five men and six women, a total of 11 athletes. The group of amateur bodybuilders consisted of seven men and eight women, a total of 15 athletes. The Functional Movement Screen™ (FMS™) was used to assess the seven included fundamental patterns that evaluate an individual’s neuromuscular control, mobility, balance, and stability. The BSA was used to assess the quality of movement, dysfunction, deficit, or compensation during the squat exercise. Statistical analyses applied non-parametric tests (Wilcoxon, Mann-Whitney U, and Friedman’s) for dependent and independent samples, with significance set at p<0.05, and the Spearman correlation coefficient and Chi-square test were used to assess relationships between quantitative and qualitative variables. Results Overall, athletes with a higher total FMS™ score performed better on the BSA as well. The professional athletes scored 2.58 points higher than the amateurs on total FMS™ scores (p<0.001). Professional athletes scored better on the BSA than amateurs (p<0.001). A statistically significant, positive moderate correlation was revealed between the FMS™ total score and the squat total score (r=0.68; p=0.005). Conclusions A higher FMS™ score in bodybuilders is associated with a higher BSA score. Professional bodybuilders have higher FMS™ scores and higher BSA scores than amateurs. Greater experience in bodybuilding is associated with the compliance with several BSA criteria: trunk position, frontal knee alignment, tibial translation angle, foot position in all three back squat variations with different external loads, and descent with the training weight. Level of Evidence 3b
... Successful RT performance is not due solely to muscular strength. 18,19 Both load and task difficulty must be considered. Higher loads increase the muscular demands (i.e., Table 2. ...
Article
Resistance training (RT) is a form of exercise that provides numerous health benefits. One barrier to participation may be the technical demands associated with some exercises. While recommendations for RT, including the number of repetitions, sets, rest, and training loads are established, recommendations for exercise selection have not been addressed. We used a Delphi-type method in three iterative surveys. In the first survey, 17 experts rated the technical complexity of 77 different strength training exercises as having low, moderate, or high technical demands. A second survey was generated based on the first, such that exercises receiving a majority high complexity vote were removed. In the second survey, experts rated the remaining exercises as either appropriate or too advanced for a novice. Exercises were deemed appropriate if 70% agreement was reached. Lastly, experts rated exercises as being appropriate for adults over the age of 60. Experts agreed that 41 different exercises were appropriate for novices and that 32 of the exercises were appropriate for novice adults over the age of 60. Our findings provide recommendations for program design to compliment already established recommendations for RT of repetitions, sets, rest periods, and training loads.
... This could be interpreted that absolute load lifted may account for this difference between subject groups. Logically, the mechanical disadvantage experienced in the "sticking region" of the BS, which occurs generally in the early part of the concentric phase and is marked by a decrease in velocity, would be more extreme while squatting 200kg than with 100kg regardless of strength level (Kompf & Arandjelović, 2017;McLaughlin, Dillman, & Lardner, 1977;van den Tillaar, Andersen, & Saeterbakken, 2014). From a practical standpoint, it appears that weaker individuals may either have faster lifting velocities due to lower absolute load or an inability to lift at a slower pace which denies their use of heavier loads. ...
Article
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Purpose: The purpose of this study was to investigate the influence of relative strength levels on load-velocity relationships in the back squat (BS). Methods: Healthy male participants (N=18) experienced in the BS performed at relative intensity (as %1RM) intervals of their estimated one-repetition maximum (1RM) up to their maximal effort. Participants were then grouped according to relative strength (1RM/body mass) into weak or strong. A comparison was made using a 2x8 (group by relative intensity) repeated-measures analysis of variance (RM-ANOVA) to identify group effects and intensity zone effect on mean concentric velocity (MCV) of the BS. Results: A significant within-subjects difference was shown between weak vs. strong [F(2.973,57.568) = 298.604, p < .001]. However, contrary to what was hypothesized, weaker participants tended to perform at higher velocities across all intensity zones. Group difference on MCV was different in trend, but not found as significance [F(1,16) = 3.212, p = .092]. Conclusion: Although group difference was not found as significant effect, strength and conditioning professionals should be advised that velocity characteristics of the BS may differ between individuals of different strength levels throughout %1RM ranges. Periodic testing and monitoring of individual athletes may be required in order to capture physical gain due to strength improvement and use of velocity as a tool for training prescription.
... As a closed chain exercise, the squat has gained wide acceptance for core stabilization and strengthening the lower body muscles (Schoenfeld 2010). Previously, the lower limb joint kinematics have been described as well as the impact of variations in squatting technique (McLaughlin et al. 1977;Escamilla et al. 2001a;Swinton et al. 2012). Most of these studies have focused on the knee biomechanics with the aim of enhancing the strength performance and minimizing the injury risk (Wilk et al. 1996;Salem et al. 2003;Adouni and Shirazi-Adl 2009;Bersini et al. 2016). ...
Article
The goal of this study was to report deep squat hip kinetics in young, athletic adults using a personalized numerical model solution based on inverse dynamics. Thirty-five healthy subjects underwent deep squat motion capture acquisitions and MRI scans of the lower extremities. Musculoskeletal models were personalized using each subject’s lower limb anatomy. The average peak hip joint reaction force was 274 percent bodyweight. Average peak hip and knee flexion angles were 107° and 112° respectively. These new findings show that deep squatting kinetics in the younger population differ substantially from the previously reported in vivo data in older subjects.
... During the back squat, technique, bar position (i.e., high bar, or low bar), and depth determine whether Table 2 Physical testing battery for rugby union forwards Strength and Conditioning Journal | www.nsca-scj.com optimal scrummaging joint angles are matched during the descent and ascent phases of the squat (22,30,52). During the conventional deadlift, these optimal scrummaging angles occur when the bar passes the knees (ankle angle) and at the midthigh position (knee and hip angles) (22). ...
Article
Optimal scrum performance in Rugby Union requires the forward-pack to produce a large sustained coordinated horizontal impulse. Training horizontal impulse and force for scrummaging is not easily simulated with traditional resistance training exercises (e.g. squat, deadlift, and clean). Therefore, it is proposed that the inclusion of heavy horizontally resisted exercises (e.g. sled push and scrum machine) within a given training phase be included to provide a greater transfer of force to the rugby scrum. This article (A) provides an overview of the physical demands and biomechanics of scrummaging, and (B) provides strength training guidelines to improve scrummaging force production.
... These factors may contribute to understanding why the LBBS might allow for greater loads to be lifted. However, these joint angle results are not definitive, and there are mixed results in the literature for the size of HBBS and LBBS trunk angles at peak hip flexion (19,26,27,33,39,44,46,52,53,80) (Tables 1 and 2). These discrepancies in joint angles may result from differences in participant age, training experience, strength, anthropometry, or the presented joint angle (i.e., presenting unprocessed segment angles or specific joint angles known as "absolute" or "relative" angles respectively) ( Figure 2). ...
Article
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The back-squat is a common exercise in strength and conditioning, for a variety of sports. It is widely regarded as a fundamental movement to increase and measure lower-body and trunk function, as well as an effective injury rehabilitation exercise. There are typically two different bar positions used when performing the back-squat; the traditional 'high-bar' back-squat (HBBS) and the 'low-bar' back-squat (LBBS). Different movement strategies are employed to ensure that the center-of-mass remains in the base-of-support for balance during the execution of these lifts. These movement strategies manifest as differences in 1) joint angles, 2) vertical ground reaction forces and, 3) the activity of key muscles. This review showed that the HBBS is characterized by greater knee flexion, lesser hip flexion, a more upright torso and a deeper squat. The LBBS is characterized by greater hip flexion and therefore a greater forward lean. However, there are limited differences in vertical ground reaction forces between the HBBS and LBBS. The LBBS can also be characterized by greater muscle activity of the erector spinae, adductors and gluteal muscles, whereas the HBBS can be characterized by greater quadriceps muscle activity. Practitioners seeking to develop the posterior-chain hip musculature (i.e. gluteal, hamstring and erector muscle groups) may seek to utilize the LBBS. In comparison, those seeking to replicate movements with a more upright torso, and contribution from the quadriceps may rather seek to employ the HBBS in training.
... These findings have been validated through enhanced performance in Olympic lifters who trained with loads that were between 10 and 30% above their CON 1 repetitions maximum (RMs) across 6 weeks (13). Addition-ally, in powerlifters, a slower ECC movement was observed in better performances in the bench press and squat exercises during competitions (28,32). Thus, preliminary evidence in resistance exercise research suggests that ECC overload can enhance lifting performance. ...
... A sticking point is defined as the most strenuous movement of a repetition, typically occurring soon after the transition from the eccentric to concentric phase (18). The sticking point of an exercise can be seen with the initial decrease in vertical barbell velocity (15). Research trying to locate the sticking point of the conventional deadlift found that typically bar velocity began to decrease during the initial pull on the barbell, with the sticking point occurring below the knees of the lifter (14). ...
Article
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Bishop, A, DeBeliso, M, Sevene, TG, and Adams, KJ. Comparing one repetition maximum and three repetition maximum between conventional and eccentrically loaded deadlifts. J Strength Cond Res 28(7): 1820-1825, 2014-This study determined if an eccentrically loaded deadlift yields a higher 1 repetition maximum (1RM) and 3RM than a conventional deadlift and if the 1RM conventional and eccentrically loaded deadlift can be accurately estimated from the 3RM (3RM = 93% of 1RM). Division 1 football players (n = 15; 20.3 +/- 1.9 years; 95.8 +/- 18.2 kg; 184.4 +/- 6.6 cm) participated. Deadlift 1RM and 3RM were measured in the conventional and eccentrically loaded deadlift. Dependent t-tests showed no significant difference between the 3RM and 1RM conventional deadlift and the 3RM and 1RM eccentrically loaded deadlift (p = 0.30 and p = 0.20, respectively). Pearson correlation between the 1RM conventional deadlift estimate and 1RM conventional deadlift actual was r = 0.91 (p <= 0.01); a dependent t-test indicated the 1RM conventional deadlift estimate was significantly less than the 1RM conventional deadlift actual (p = 0.007). Pearson correlation between the 1RM eccentrically loaded deadlift estimate and 1RM eccentrically loaded deadlift actual was r = 0.84 (p <= 0.01); a dependent t-test indicated the 1RM eccentrically loaded deadlift estimate was nearly significantly less than the 1RM eccentrically loaded deadlift actual (p = 0.061). Results suggest that conventional and eccentrically loaded deadlifts may be interchangeable within a training program; this may elicit the benefits of using a broader variety of ground-based multijoint compound movements in an athlete's strength and power training. Additionally, because of differences between predicted and actual 1RM scores in the deadlift, strength coaches should prioritize actual 1RM testing of their athletes to optimize deadlift training loads across the RM continuum.
... Many studies on the sticking point examined the stage in a lift at which the sticking point was observed for different exercises [6,9,13,54,55]. These findings can offer valuable insight into different strategies that can be employed to improve performance. ...
Article
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In the context of resistance training the so-called "sticking point" is commonly understood as the position in a lift in which a disproportionately large increase in the difficulty to continue the lift is experienced. If the lift is taken to the point of momentary muscular failure, the sticking point is usually where the failure occurs. Hence the sticking point is associated with an increased chance of exercise form deterioration or breakdown. Understanding the mechanisms that lead to the occurrence of sticking points as well as different training strategies that can be used to overcome them is important to strength practitioners (trainees and coaches alike) and instrumental for the avoidance of injury and continued progress. In this article we survey and consolidate the body of existing research on the topic: we discuss different definitions of the sticking point adopted in the literature and propose a more precise definition, describe different muscular and biomechanical aspects that give rise to sticking points, and review the effectiveness of different training modalities used to address them.
... The squat is a functional, multiple-joint exercise that has received considerable biomechanical evaluation. Investigations have examined the kinematics (20), kinetics (21), and muscle recruitment patterns (17) of the squat at various joints (13) for different stances and loads (5); however, investigations have not characterized these parameters in elders using variations of the exercise. ...
Article
Purpose: Squatting activities may be used, within exercise programs, to preserve physical function in older adults. This study characterized the lower-extremity peak joint angles, peak moments, powers, work, impulse, and muscle recruitment patterns (electromyographic; EMG) associated with two types of squatting activities in elders. Methods: Twenty-two healthy, older adults (ages 70 – 85) performed three trials each of: 1) a squat to a self-selected depth (normal squat; SQ) and 2) a squat onto a chair with a standardized height of 43.8 cm (chair squat; CSQ). Descending and ascending phase joint kinematics and kinetics were obtained using a motion analysis system and inverse dynamics techniques. Results were averaged across the three trials. A 2 2 (activity phase) ANOVA with repeated measures was used to examine the biomechanical differences among the two activities and phases. EMG temporal characteristics were qualitatively examined. Results: CSQ generated greater hip flexion angles, peak moments, power, and work, whereas SQ generated greater knee and ankle flexion angles, peak moments, power, and work. SQ generated a greater knee extensor impulse, a greater plantar flexor impulse and a greater total support impulse. The EMG temporal patterns were consistent with the kinetic data. Conclusions: The results suggest that, with older adults, CSQ places greater demand on the hip extensors, whereas SQ places greater demand on the knee extensors and ankle plantar flexors. Clinicians may use these discriminate findings to more effectively target specific lower-extremity muscle groups when prescribing exercise for older adults.
... A common guideline for the barbell squat is to prevent the knees from moving out beyond a vertical line over the toes. The instructions for proper knee position during squats, which were established in Europe by the National Strength and Conditioning Association (NSCA) (7,14), are based on previous studies (4,25,26). The NSCA position paper (7) further states that, with some exceptions, the shin should remain as vertical as possible. ...
Article
Lorenzetti, S, Gülay, T, Stoop, M, List, R, Gerber, H, Schellenberg, F, and Stüssi, E. Comparison of the angles and corresponding moments in the knee and hip during restricted and unrestricted squats. J Strength Cond Res 26(10): 2829-2836, 2012-The aim of this study was to compare the angles and corresponding moments in the knee and hip during squats. Twenty subjects performed restricted and unrestricted squats with barbell loads that were 0, ¼, and ½ their body weight. The experimental setup consisted of a motion capture system and 2 force plates. The moments were calculated using inverse dynamics. During the unrestricted squats, the maximum moments in the knee were significantly higher, and those in the hip were significantly lower than during restricted squats. At the lowest position, the maximum knee flexion angles were approximately 86° for the restricted and approximately 106° for the unrestricted techniques, whereas the maximum hip flexion angle was between 95° and 100°. The higher moments in the hip during restricted squats suggest a higher load of the lower back. Athletes who aim to strengthen their quadriceps should consider unrestricted squats because of the larger knee load and smaller back load.
... he squat is one of the most frequently used resistance exercises for strength development in both athletic and rehabilitation settings. As a result of its widespread use, the exercise has been the focus of a large number of biomechanical studies ([10][11][12]19,21,23,24,28). The results present the squat as a complex movement that requires coordinated actions of the torso and all major joints of the lower extremities (10,20). ...
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The purpose of this study was to compare the biomechanics of the traditional squat with 2 popular exercise variations commonly referred to as the powerlifting squat and box squat. Twelve male powerlifters performed the exercises with 30, 50, and 70% of their measured 1 repetition maximum (1RM), with instruction to lift the loads as fast as possible. Inverse dynamics and spatial tracking of the external resistance were used to quantify biomechanical variables. A range of significant kinematic and kinetic differences (p < 0.05) emerged between the exercises. The traditional squat was performed with a narrow stance, whereas the powerlifting squat and box squat were performed with similar wide stances (48.3 ± 3.8, 89.6 ± 4.9, 92.1 ± 5.1 cm, respectively). During the eccentric phase of the traditional squat, the knee traveled past the toes resulting in anterior displacement of the system center of mass (COM). In contrast, during the powerlifting squat and box squat, a more vertical shin position was maintained, resulting in posterior displacements of the system COM. These differences in linear displacements had a significant effect (p < 0.05) on a number of peak joint moments, with the greatest effects measured at the spine and ankle. For both joints, the largest peak moment was produced during the traditional squat, followed by the powerlifting squat, then box squat. Significant differences (p < 0.05) were also noted at the hip joint where the largest moment in all 3 planes were produced during the powerlifting squat. Coaches and athletes should be aware of the biomechanical differences between the squatting variations and select according to the kinematic and kinetic profile that best match the training goals.
... The presented analysis of effective force-length and force-velocity characteristics highlights the complexity introduced by the body's biomechanics in inferring from observable performance the optimal target for specialized training with the aim of overcoming the ''weakest link'' in a particular lift. The spectrum of functional variations that can be produced is increased far further for complex lifts involving many contribution muscles, the force characteristic of each being modulated according to different biomechanics (McLaughlin et al. 1977(McLaughlin et al. , 1978. As a consequence rigourous comparison of different partial ROM training strategies is firmly placed outside the reach of qualitative analysis and due to practical constraints also that of empirical study. ...
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The occurrence of so-called sticking points in a lift is pervasive in weight training practice. Biomechanically complex exercises often exhibit multi-modal variation of effective force exerted against the load as a function of the elevation and velocity of the load. This results in a variety of possible loci for the occurrence of sticking points and makes the problem of designing the optimal training strategy to overcome them challenging. In this article a case founded on theoretical grounds is made against a purely empirical method. It is argued that the nature of the problem considered and the wide range of variables involved limit the generality of conclusions which can be drawn from experimental studies alone. Instead an alternative is described, whereby a recently proposed mathematical model of neuromuscular adaptation is employed in a series of computer simulations. These are used to examine quantitatively the effects of differently targeted partial range of motion (ROM) training approaches. Counter-intuitively and in contrast to common training practices, the key novel insight inferred from the obtained results is that in some cases the most effective approach for improving performance in an exercise with a sticking point at a particular point in the ROM is to improve force production capability at a different and possibly remote position in the lift. In the context of the employed model, this result is explained by changes in the neuromuscular and biomechanical environment for force production.
... Bar speed was set at a constant 0.40 m/s during all tests, based on the mean bar speed of a typical squat movement (24). The isokinetic protocol was used in order that, for a given time, muscle length changes occurring as a result of the movement would be somewhat similar across tests and their influence on contractile performance thus controlled. ...
Article
To isolate any difference muscular contraction history may have on concentric work output, 40 trained male subjects performed three separate isokinetic concentric squats that involved differing contraction histories, 1) a concentric-only (CO) squat, 2) a concentric squat preceded by an isometric preload (IS), and 3) a stretch-shorten cycle (SSC) squat. Over the first 300 ms of the concentric movement, work output for both the SSC and IS conditions was significantly greater (154.8 +/- 39.8 and 147.9 +/- 34.7 J, respectively; P < 0.001) compared with the CO squat (129.7 +/- 34.4 J). In addition, work output after the SSC test over the first 300 ms was also significantly larger than that for the corresponding period after the IS protocol (P < 0.05). There was no difference in normalized, integrated electromyogram among any of the conditions. It was concluded that concentric performance enhancement derived from a preceding stretch of the muscle-tendon complex was largely due to the attainment of a higher active muscle state before the start of the concentric movement. However, it was also hypothesized that contractile element potentiation was a significant contributor to stretch-induced muscular performance under these conditions.
... Studies have shown (35,36) that expert squatters, such as experienced powerlifters, perform better and have more favorable kinematics (more erect trunk, less horizontal hip and bar displacement, and less vertical bar velocity during the descent) and kinetics (less trunk torques and greater extensor dominant thigh torques) compared with novice squatters. Escamilla et al. (17) used powerlifters and bodybuilders experienced in performing the barbell squat in order to examine knee biomechanics while squatting (Table 1). ...
Article
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. The purpose of this review was to examine knee biomechanics during the dynamic squat exercise. Tibiofemoral shear and compressive forces, patellofemoral compressive force, knee muscle activity, and knee stability were reviewed and discussed relative to athletic performance, injury potential, and rehabilitation. Low to moderate posterior shear forces, restrained primarily by the posterior cruciate ligament (PCL), were generated throughout the squat for all knee flexion angles. Low anterior shear forces, restrained primarily by the anterior cruciate ligament (ACL), were generated between 0 and 60 degrees knee flexion. Patellofemoral compressive forces and tibiofemoral compressive and shear forces progressively increased as the knees flexed and decreased as the knees extended, reaching peak values near maximum knee flexion. Hence, training the squat in the functional range between 0 and 50 degrees knee flexion may be appropriate for many knee rehabilitation patients, because knee forces were minimum in the functional range. Quadriceps, hamstrings, and gastrocnemius activity generally increased as knee flexion increased, which supports athletes with healthy knees performing the parallel squat (thighs parallel to ground at maximum knee flexion) between 0 and 100 degrees knee flexion. Furthermore, it was demonstrated that the parallel squat was not injurious to the healthy knee. 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.
... Squatting with a mass on the shoulders is one of the most widely used training exercises for the development of strength in the lower leg extensor muscles (McLaughlin et al. 1977), or for general ®tness and rehabilitation exercises (Beynnon and Johnson 1996). In general, the load is set at a percentage of the maximum weight the individual can lift once with proper form and technique (the one-repetition maximum). ...
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The purpose of this study was to describe the force/velocity and power/velocity relationships obtained during squat exercise. The maximal force (F0) was extrapolated from the force/velocity relationship and compared to the isometric force directly measured with the aid of a force platform placed under the subject's feet. Fifteen international downhill skiers [mean (SD) age 22.4 (2.6) years, height 178 (6.34) cm and body mass 81.3 (7.70) kg] performed maximal dynamic and isometric squat exercises on a guided barbell. The dynamic squats were performed with masses ranging from 60 to 180 kg, which were placed on the shoulders. The force produced during the squat exercise was linearly related to the velocity in each subject (r2 = 0.83-0.98, P < 0.05-0.0001). The extrapolated F0 was 23% higher than the measured isometric force (P < 0.001), and the two measurements were not correlated. This may be attributed to the position of the subject, since the isometric force was obtained at a constant angle (90 degrees of knee flexion), whereas the dynamic forces were measured through a range of movements (from 90 degrees to 180 degrees). The power/velocity relationship was parabolic in shape for each subject (r2 = 0.94-0.99, P < 0.01-0.0001). However, the curve obtained exhibited only an ascending part. The highest power was produced against the lightest load (i.e., 60 kg). The maximal power (Wmax) and optimal velocity were never reached. The failure to observe the descending part of the power/velocity curve may be attributed to the upper limitation of the velocities studied. Nevertheless, the extrapolation of Wmax from the power/velocity equation showed that it would be reached for a load close to body mass, or even under unloaded conditions.
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We investigated the associations and differences between dynamic strength index (DSI) calculated from different types of vertical jump (countermovement jump; CMJ and squat jump; SJ) and different isometric knee joint angles (30, 60 and 90°), and associations with force-velocity (FV) profile and its constituent variables (maximal theoretical force (V0), power (Pmax) and velocity (V0) and the slope of the FV relationship (Sfv), on a sample of young athletes and active participants (n = 28). There were moderate associations between Pmax and all DSI values (r=0.42-0.69; p<0.05), V0 and all DSI values from CMJ and DSI30 from SJ (r=0.43-0.56; p<0.05), while Sfv was associated only with DSI30 and DSI90 in CMJ (r=0.40-0.43; p<0.05). This suggests that DSI and FV methods provide similar information and can be used in a similar manner to direct an individual's training.
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The purpose of the study was to compare the kinematics of the barbell back squat between two footwear conditions and to evaluate the results with respect to recommendations put forth in the National Strength and Conditioning Association position statement for proper squat technique. Twenty-five subjects with 5 - 7 years of resistance training experience participated. Selected kinematics were measured during a 60% of 1RM barbell back squat in both barefoot and athletic shoe conditions. Paired-samples T tests were performed to compare the two footwear conditions. Significant differences were found in trunk (50.72±8.27 vs. 46.97±9.87), thigh (20.94±10.19 vs. 24.42±11.11), and shank segment angles (59.47±5.54 vs. 62.75±6.17), and knee joint angles (81.33±13.70 vs. 88.32±15.45) at the peak descent position. Based on the kinematic analysis of the barefoot squat, two kinematic advantages are countered by two disadvantages. Coaches and instructors should acknowledge these results with respect to a performer's capability, and be aware the advantages and disadvantages of barefoot squat from a kinematic perspective.
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Erweiterter Überblicksartikel mit detaillierter Diskussion über die korrekte Übungsausführung der tiefen Kniebeuge 1. Mechanische Belastung und Beanspruchung des tibio- und patellofemoralen Gelenks in Abhängigkeit von Kniebeugetiefe und Lasthöhe 2. Kniegelenk- und Wirbelsäulenbelastung in der Kniebeuge in Abhängigkeit von der Übungsausführung 3. Mechanische Festigkeitswerte von passiven Strukturen des Kniegelenks und der Wirbelsäule und deren Anpassungen an Krafttraining 4. Verletzungsrisiken und Überlastungsschäden des passiven Bewegungsapparates der Wirbelsäule 5. Trainingspraktische Empfehlungen
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Summary Functional training and specific strength training are widely used terms. In the last two decades a lot of strength training interventions were named functional of specific in the field of fitness training and competitive sports. This occurred without any substantive reason beside the argument that the interventions are kinematically and kineticly related to sport specific movements or actions of daily living. The main problem while using the words functional and specific in this way is, that this does not consider the physiological background of what makes a movement or training intervention specific. This article tries to show some problems that exist while using the words functional and specific in the field of strength training from a physiological perspective. Zusammenfassung Funktionelles und spezifisches Krafttraining stellen im Bereich des Fitnesstrai-nings und des Leistungssports zwei in den letzten zwei Jahrzehnten weit ver-breitete Begriffe dar. Die inhaltliche Begründung für die Verwendung der Be-griff funktionell und spezifisch beschränkt sich in der Regel auf die Aussage, dass sich das Krafttraining an kinematischen und kinetischen Merkmalen sportartspezifischer und / oder alltäglicher Bewegungen orientiert. Ein großes Problem bei dieser Betrachtungsweise ist jedoch, dass diese außer Acht lässt, was aus physiologischer Sicht eine Bewegung oder Trainingsintervention spe-zifisch macht. Innerhalb dieses Beitrags soll der Versuch unternommen wer-den die Probleme, die die Verwendung der Begriffe funktionell und spezifisch 45 in Kombination mit dem Wort Krafttraining beinhalten, vor dem Hintergrund ei-ner physiologischen Betrachtungsweise aufzuzeigen.
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This study determined if an eccentrically loaded deadlift yields a higher 1RM and 3RM than a conventional deadlift; and if the 1RM conventional and eccentrically loaded deadlift can be accurately estimated from the 3RM (3RM = 93% of 1RM). Division One football players (n=15; 20.3 ± 1.9 yrs; 95.8 ± 18.2 kg; 184.4 ± 6.6 cm) participated. Deadlift 1RM and 3RM were measured in the conventional and eccentrically loaded deadlift. Dependent t-tests showed no significant difference between the 3RM and 1 RM conventional deadlift and the 3RM and 1RM eccentrically loaded deadlift (p=0.30 and p=0.20, respectively). Pearson correlation between the 1RM conventional deadlift estimate and 1RM conventional deadlift actual was r=0.91 (p<0.01); a dependent t-test indicated the 1RM conventional deadlift estimate was significantly less than the 1RM conventional deadlift actual (p=0.007). Pearson correlation between the 1RM eccentrically loaded deadlift estimate and 1RM eccentrically loaded deadlift actual was r=0.84 (p<0.01); a dependent t-test indicated the 1RM eccentrically loaded deadlift estimate was nearly significantly less than the 1RM eccentrically loaded deadlift actual (p=0.061). Results suggest that conventional and eccentrically loaded deadlifts may be interchangeable within a training program; this may elicit the benefits of utilizing a broader variety of ground based multi-joint, compound movements in an athlete's strength and power training. Additionally, due to differences between predicted and actual 1RM scores in the deadlift, strength coaches should prioritize actual 1RM testing of their athletes in order to optimize deadlift training loads across the RM continuum.
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The purpose of this study was to compare the knee extensor demands and low back injury risks of the front and back squat exercises. Highly strength-trained college-aged males (n = 8), who performed each type of squat (Load = 75% of front squat one repetition maximum), were filmed (50 fps) from the sagittal view. The body was modeled as a five link system. Film data were digitized and reduced through Newtonian mechanics to obtain joint forces and muscle moments. Mean and individual subject data results were examined. The maximum knee extensor moment comparison indicated similar knee extensor demands, so either squat exercise could be used to develop knee extensor strength. Both exercises had similar low back injury risks for four subjects, but sizable maximum trunk extensor moment and maximum lumbar compressive and shear force differences existed between the squat types for the other subjects. The latter data revealed that with the influence of trunk inclination either exercise had the greatest low back injury risk (i.e., with greater trunk inclination: greater trunk extensor demands and lumbar shear forces, but smaller lumbar compressive forces). For these four subjects low back injury risk was influenced more by trunk inclination than squat exercise type.
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Sumario: The present investigation, undertaken to determine the relationships that exist among variables typically associated with lifting research (posture and time factors ) and that of knowledge of load magnitude, found force and moment differences that could be attributed to the strategy selected by the worker based upon experience levels when allowed to assume a freely chosen posture
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Resultant forces and torques on the joints of 11 females were studied as the subjects performed two manual materials handling tasks in their industrial environment. The subject's activities were recorded by high speed (102 frames per second) 16mm cinematography and the data analysed by a static and dynamic biomechanical model.Statistically significant differences were found between the results of the static and dynamic analyses. Slower filming rates were simulated and were found to show fewer significant differences between the static and dynamic analysis as the data sampling rate decreased. A kinematic analysis of the experienced and inexperienced lifters revealed a great deal of intra-subject variability as well as inter-subject variability indicating that the subjects varied their motion patterns as they lifted or lowered several 14 kg loads. For submaximal tasks such a variation in lifting patterns would allow the subjects to develop muscular load sharing which would help reduce localized muscle fatigue associated with repetitive lifting activities.
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A sagittal-plane model of the knee, which takes account of the movements of the flexion axis relative to the femur and tibia and considers the possibility of antagonistic and synergistic muscle action, is used to determine the values of the forces transmitted by the muscles, cruciate ligaments and intra-articular surfaces during the clean phase of the clean-and-jerk weightlift. The theoretical analyses demonstrate that it is geometrically and mechanically possible for the knee musculature to unload and thereby protect the cruciate ligaments throughout a substantial portion of the lift. The price to be paid for this protection, in the case of the co-contraction of antagonistic muscles, is larger muscle and tibio-fermoral contact forces. The application of synergistic muscle action, however, results in smaller individual muscle and intra-articular contact forces.
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Altering foot stance is often prescribed as a method of isolating muscles during the parallel squat. The purpose of this study was to compare activity in six muscles crossing the hip and/or knee joints when the parallel squat is performed with different stances and bar loads. Nine male lifters served as subjects. Within 7 d of determining IRM on the squat with shoulder width stance, surface EMG data were collected (800 Hz) from the rectus femoris, vastus medialis, vastus lateralis, adductor longus, gluteus maximus, and biceps femoris while subjects completed five nonconsecutive reps of the squat using shoulder width, narrow (75% shoulder width), and wide (140% shoulder width) stances with low and high loads (60% and 75% 1RM, respectively). Rep time was controlled. A goniometer on the right knee was used to identify descent and ascent phases. Integrated EMG values were calculated for each muscle during phases of each rep, and the 5-rep means for each subject were used in a repeated measures ANOVA (phase x load x stance, alpha = 0.05). For rectus femoris, vastus medialis, and vastus lateralis, only the load effect was significant. Adductor longus exhibited a stance by phase interaction and a load effect. Gluteus maximus exhibited a load by stance interaction and a phase effect. Biceps femoris activity was highest during the ascent phase. The results suggest that stance width does not cause isolation within the quadriceps but does influence muscle activity on the medial thigh and buttocks.
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The purpose of this study was to assess the validity of a new device to evaluate isometric strength during multi-joint exercise such as the squat or bench press. The device used an electric motor-driven bar to simultaneously generate and measure forces during weight lifting exercises. This new device and a force platform measured the forces generated by either the motor on a fixed telescopic steel girder (passive condition) or a subject pushing vertically against the bar from three squat positions (active condition). In the passive condition, 252 measurements were made, with 3 trials for 6 bar heights and 14 bar loads. In the active condition, 8 young physically active students (age, height and body mass were 25.1 +/- 2.6 years, 179.3 +/- 7.2 cm and 82.0 +/- 9.9 kg, respectively) performed 3 maximal isometric strength (MIS) trials in each of the 3 squat exercise positions (parallel, half and quarter squat), and 3 additional MIS trials in one position randomly assigned two weeks later to test inter-day reliability. In the passive condition, no differences were observed between the forces measured by the force platform and the new device. The coefficient of linear regression (r) and the coefficient of variation (CV) were 1 and below 0.23%, respectively. In the active condition, the peak MIS measured was 2828 N and the values of r and CV were above 0.982 and below 5.96%, respectively. The assessment of inter-day reliability showed an r value of 0.984 and a CV of 3.98%. This study demonstrated that the new electric motor-driven exerciser provides valid and reliable data when used to generate forces and measure isometric strength throughout the load and motion ranges commonly used in squat exercise.
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