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A systematic review on the muscular activation on the lower limbs with five different variations of the squat exercise

Authors:
Javier Gene-Morales at University of Valencia
Javier Gene-Morales
Jorge Flández at Universidad Austral de Chile
Jorge Flández
Álvaro Juesas at University of Valencia
Álvaro Juesas
Pedro Gargallo
Pedro Gargallo
Pedro Gargallo
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Abstract and Figures

The squat is one of the most commonly used resistance exercises for performance and health due to its biomechanical and neuromuscular similarities to a wide range of athletic and everyday activities. There is a large number of squat variations (based on the descent depth, width of the stance, bar placement) with significant biomechanical and neuromuscular differences between them. The aim of this study was to systematically review the scientific literature to gather data on the muscular activation of the lower limb during different variants of the squat exercise. High-bar squat (full range of motion, to parallel and partial range of motion), low-bar squat, front squat, overhead squat and guided squat on Smith machine were included in the analysis. 30 articles met the inclusion criteria and were reviewed. Quality of the included studies was analysed with the PEDro scale. Main findings were that in the squat exercise activation of the knee-extensors is predominant. However, different activation patterns were observed with different distances between the feet, different depths, hips rotation or flexion, intensities. For instance, low-bar squat involves a greater hip hinge and thus, provokes major activation on the hip-extensors than other squat variations. It is worth highlighting that similar activation patterns were observed between the front squat and the high-bar squat. The variation with least activation was the guided squat. The evidence presented in this study may help the strength and conditioning professionals and practitioners with the exercise selection depending on the muscular targets and the individual characteristics of the athlete. Keywords: Electromyographic activity; Resistance exercise; Quadriceps; Gluteus; Hamstrings; Calves.
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VOLUME 15 | Proc4 | 2020 |
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Supplementary Issue: Summer Conferences of Sports Science. Costa Blanca Sports Science Events, 25-26 September 2020. Alicante, Spain.
A systematic review on the muscular activation on the lower
limbs with five different variations of the squat exercise
JAVIER GENE-MORALES1,2, JORGE FLANDEZ3, ALVARO JUESAS2, PEDRO GARGALLO2, IVÁN
MIÑANA2, JUAN C. COLADO2
1
1Research Institute on Traffic and Road Safety (INTRAS), University of Valencia, Valencia, Spain
2Research Unit in Sport and Health, University of Valencia, Valencia, Spain
3Institute of Education Sciences, Austral University of Chile, Ciudad de Valdivia, Chile
ABSTRACT
The squat is one of the most commonly used resistance exercises for performance and health due to its
biomechanical and neuromuscular similarities to a wide range of athletic and everyday activities. There is a
large number of squat variations (based on the descent depth, width of the stance, bar placement) with
significant biomechanical and neuromuscular differences between them. The aim of this study was to
systematically review the scientific literature to gather data on the muscular activation of the lower limb during
different variants of the squat exercise. High-bar squat (full range of motion, to parallel and partial range of
motion), low-bar squat, front squat, overhead squat and guided squat on Smith machine were included in the
analysis. 30 articles met the inclusion criteria and were reviewed. Quality of the included studies was
analysed with the PEDro scale. Main findings were that in the squat exercise activation of the knee-extensors
is predominant. However, different activation patterns were observed with different distances between the
feet, different depths, hips rotation or flexion, intensities. For instance, low-bar squat involves a greater hip
hinge and thus, provokes major activation on the hip-extensors than other squat variations. It is worth
highlighting that similar activation patterns were observed between the front squat and the high-bar squat.
The variation with least activation was the guided squat. The evidence presented in this study may help the
strength and conditioning professionals and practitioners with the exercise selection depending on the
muscular targets and the individual characteristics of the athlete.
Keywords: Electromyographic activity; Resistance exercise; Quadriceps; Gluteus; Hamstrings; Calves.
1
Corresponding author. Department of Physical Education and Sports, University of Valencia. C/ Gascó Oliag 3, 46010,
Valencia, Spain. https://orcid.org/0000-0002-3255-3940
E-mail: juan.colado@uv.es
Abstract submitted to: Spring Conferences of Sports Science. Costa Blanca Sports Science Events, 19-20 June 2020. Alicante,
Spain.
JOURNAL OF HUMAN SPORT & EXERCISE ISSN 1988-5202
© Faculty of Education. University of Alicante
doi:10.14198/jhse.2020.15.Proc4.28
Cite this article as:
Gene-Morales, J., Flandez, J., Juesas, A., Gargallo, P., Miñana, I., & Colado, J.C. (2020). A systematic review on the muscular
activation on the lower limbs with five different variations of the squat exercise. Journal of Human Sport and Exercise,
15(4proc), S1277-S1299. doi:https://doi.org/10.14198/jhse.2020.15.Proc4.28
Proceeding
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INTRODUCTION
The squat is one of the most commonly used resistance exercises for performance and health due to its
biomechanical and neuromuscular similarities to a wide range of athletic and everyday activities (Andersen
et al., 2016; Clark et al., 2012; Kompf & Arandjelović, 2017; Schoenfeld, 2010). All variants of the squat
involve synergistic hip, knee, and ankle flexion in the descent, followed by knee and hip extension in the
ascent which finishes with the individual in the starting position (Clark et al., 2012; Escamilla et al., 2001;
Iversen et al., 2017; Schoenfeld, 2010; Vigotsky et al., 2019). However, there is a large number of squat
variations (based on the descent depth, the width of the stance, bar placement, orientation of the knee flexion
planes, and so on) with significant biomechanical and neuromuscular differences between them (Clark et al.,
2012; Kompf & Arandjelović, 2017; Schoenfeld, 2010; Van den Tillaar et al., 2014). One of the aims of the
expert research to the date has been to enlighten the strength and conditioning professionals and athletes
with the differences between these variations in terms of muscular activity (Bourne et al., 2017).
Understanding the muscular activity of each exercise is a key point in the prescription and programming of
resistance exercises depending on the individual characteristics (Bolgla & Uhl, 2005; Borreani et al., 2014;
Neto et al., 2020).
Muscular activity is often measured with surface electromyography, a method that registers the intensity and
duration of electric signals produced in the muscles (Chowdhury et al., 2013). Electrodes are placed on
specific superficial points that cover the muscle to analyse. The electromyograph gives raw data in absolute
electric signal intensity in millivolts (mV) or microvolts (μV). Typical methods to standardize the results are a)
as a relative percentage of a maximum voluntary isometric contraction (IMVC); b) as a relative percentage
of the maximum historical contraction (MVC); c) as the square root of the average power of the EMG signal
for a given period of time (root mean square; RMS) (Sinclair et al., 2015). Data in the scientific literature are
uneven and thus, comparisons between studies are sometimes difficult.
The main objective of this research was to systematically review the expert literature to gather data on the
muscular activation of the lower limb during different variants of the squat exercise. We aimed to identify the
main characteristics of each variant, the predominant muscle groups involved, and to determine the variant
with higher activation levels, through the analyses of the included studies.
METHODS
For this systematic review, the protocols of the PRISMA declaration (Hutton et al., 2015; Urrútia & Bonfill,
2010) were followed.
Search strategy
Four databases (Web of Science, PubMed, Scopus, and SportDiscus) and ProQuest (i.e. an electronic tool
containing doctoral thesis) were consulted to collect information about muscular activation. Also, the Strength
and Conditioning Journal was consulted. No temporal restrictions were used in the search. The following
terms were used: [“squat” OR “squat exercise” OR “high bar squat” OR “low bar squat” OR “overhead squat”
OR “front squat”] AND [“EMG” OR “electromyography” OR “electromyographic activity” OR “muscle
activation” OR “muscle activity”]. A third line was added with the following terms to include technical
variations: [“stance width” OR “hip rotation” OR “Smith machine” OR “deep” OR “depth” OR “parallel” OR
“partial” OR “quarter”]. Furthermore, the operator “NOT” was used in combination with the terms “balance”,
“instability”, “unstable”, “bands”, “chains”, “injury”, “injured”, “unload”, and “therapeutic” to refine the results
and exclude articles that did not follow the inclusion criteria.
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Eligibility criteria
Studies that examined muscle activation on the lower limb in squats written in Spanish or English were
included in the analyses. Inclusion criteria were a) including healthy subjects with no recent history of injury;
b) using stable surfaces to perform the squats; c) using a barbell with load. On the other hand, exclusion
criteria were a) using variable resistance (i.e. elastic bands, chains) to load the exercise; b) analysing muscle
activity of the upper limb or trunk; c) performing an isometric squat.
Article selection and data processing
Studies
Screening of titles and abstracts was initially carried out to identify potentially relevant studies. A standardized
form was used to assess the eligibility of each article considering the inclusion-exclusion criteria. Figure 1
shows the flow diagram that summarizes the study selection process after the reading of the titles and
abstracts of the initial search.
Figure 1. Flow diagram that summarizes the study selection process from the first search to the final selection.
Squat variations
After carefully reading the selected articles five squat variations were selected for the analysis by agreement
between the authors. Some squat variations found in the literature and excluded from the analysis were the
unilateral squat, Bulgarian squat, and wall squat. The five squat variations included were (see Figure 2):
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High-bar squat (26 studies): the bar is placed across the shoulder on the trapezius, slightly above the level
of the acromion and the posterior aspect of the deltoids (Schoenfeld, 2010; Vigotsky et al., 2019; Wretenberg
et al., 1996).
Front squat (5 studies): the bar is held in front of the chest at the clavicle (Bautista, 2019; Schoenfeld, 2010).
Overhead squat (2 studies): bar is held with both hands, fully extended elbows, and externally rotated
shoulders (Bautista, 2019).
Guided squat on Smith machine (2 studies): the bar is guided and thus, it only can be moved up and down
(different variations of the squat can be performed on the Smith machine, however for this study, we
considered a high bar squat; Clark et al., 2012).
Low-bar squat (1 study): the bar is placed slightly below the level of the acromion (Schoenfeld, 2010;
Wretenberg et al., 1996).
Figure 2. From left to right: a) high-bar squat, b) front-squat, c) overhead squat, d) low-bar squat. The guided
squat is not pictured as for this study, the placement of the bar was the same as in the high-bar squat.
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The high bar squat was in turn divided in full range of motion (ROM; i.e. the hips are lower than the knees),
to parallel (i.e. lowering until the femur is parallel to the ground, approximately 90º of knee movement), and
partial range of motion (i.e. half the ROM of a parallel squat, a quarter of a full ROM squat, approximately
45º of knee movement). Also, different technical variants of the squat exercise such as stance width and hip
rotation planes were included to enrich the analyses.
Muscles analysed
As mentioned in the objective, this study focuses on the muscles of the lower limb. After a thorough reading
of the selected articles, the authors selected the muscles to be included in the analysis. These muscles were
a) gluteus maximus, b) gluteus medialis, c) hip adductors, d) vastus lateralis, e) vastus medialis, f) rectus
femoris, g) biceps femoris, h) semitendinosus, i) tibialis anterior, j) gastrocnemius and k) soleus. Muscles “a,
b, and c” act mainly on the hips; muscles “d, e, and f” are part of the quadriceps and are mainly involved in
the knee-extension; muscles “g and h” are part of the hamstrings and their contraction mainly affect the
knees; the tibialis anterior (muscle “i”) is an ankle dorsiflexor; and finally, the muscles “j and k” are part of the
calves and their action provoke an ankle extension. Previous expert literature (Netter, 1999) can be consulted
for further information on the included muscles and anatomy.
Electromyographic values
EMG values are unequally reported among the expert literature, not only on the units used (millivolts,
microvolts, percentage of isometric maximum voluntary contraction, percentage of maximum voluntary
contraction, percentage of root mean square values) but also on the measured phase (concentric and
eccentric, mean of the set, mean of a repetition). In this review, the authors standardized the values when
possible to facilitate the comprehension and the comparison between studies. For instance, values in
millivolts were transformed into microvolts. Also, results of concentric and eccentric phases were averaged
to obtain a single value.
Quality assessment
The quality of the included studies was analysed using the PEDro scale (Maher et al., 2003). The scale was
modified to fit the design of the included studies (see Table 3). Points 2 and 3 were unified into one point that
assessed the randomization of the exercise conditions performed. Point 4 had to be excluded due to not
including studies with control and experimental groups. Finally, points 5, 6, and 7 were also excluded due to
the impossibility of blinding subjects or researchers. The resultant scale to evaluate the quality of the articles
was composed of 6 items.
RESULTS
30 articles met the inclusion criteria and were reviewed (Figure 1). As abovementioned (see “data processing
and analysis-squat variations” section), the most widely studied variation of the squat exercise was the high-
bar squat (26 studies), followed by the front-squat (5 studies), the overhead squat, and guided squat (both
analysed by 2 studies), and finally the low-bar squat (1 study). The main muscular group involved in all the
variations was the quadriceps, with some differences between each squat variation, and also between
different technical modifications (i.e. ROM, stance width, hip rotation, feet placement).
Due to the considerable amount of variations and exercise conditions, the results section will be divided into
six subsections: one for each squat variation, and one including the technical modifications of the exercise
(i.e. stance width, hip rotation). Furthermore, Table 1 includes the main characteristics of the included studies
(i.e. sample characteristics, exercise condition, measured muscles, and main results), and Table 2 presents
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reported EMG values. EMG values are presented in different units (i.e. absolute values, IMVC, MVC, RMS),
and thus caution should be applied when comparing values between studies.
High-bar squat
A major part of the studies found the main activity on the vastus lateralis, vastus medialis, and rectus femoris,
in this order (Aspe & Swinton, 2014; Contreras et al., 2015, 2016; da Silva et al., 2017; Delgado et al., 2019;
Ebben et al., 2009; Eliassen et al., 2018; Gorsuch et al., 2013; Hammond et al., 2016; Iversen et al., 2017;
Korak et al., 2018; Robbins, 2011; Schwanbeck et al., 2009; Wu et al., 2019; Yavuz et al., 2015). Only one
study found major activation on the biceps femoris than on each of these three aforementioned muscles
(Andersen et al., 2014). Regarding the activation on the gluteus and hamstrings, while some authors
observed a greater activation on the gluteus maximus (Caterisano et al., 2002; Fauth et al., 2010; McCurdy
et al., 2018), others reported a higher activity on the hamstrings (Andersen et al., 2014; Delgado et al., 2019;
Gullett et al., 2009). Only three authors reported activation levels on the muscles of the calves when
performing a high-bar squat (Aspe & Swinton, 2014; da Silva et al., 2017; Schwanbeck et al., 2009).
Front squat
Muscle activity in this squat variation followed similar patterns to other squat variations (i.e. major activation
on the vastus lateralis and medialis). Korak et al. (2018) reported similar activation levels on the rectus
femoris and gluteus maximus. Opposite to the aforementioned authors, Gullet et al. (2009) found higher
activation levels on the hamstrings (semitendinosus: 140% of the IMVC) than on the quadriceps (vastus
lateralis: 60% of the IMVC; vastus medialis: 81% of the IMVC; rectus femoris: 59% of the IMVC).
Overhead squat
Two studies analysed this variation of the squat exercise (Aspe & Swinton, 2014; Bautista, 2019). As
happened with the rest of the variations, major activation levels were found on the vastus lateralis in both
studies. As secondary muscles, Aspe & Swinton (2014) reported higher activation levels on the gluteus (61%
of the MVC) than on the biceps femoris (54% of the MVC). Bautista (2019) found lower activation levels on
the biceps femoris (31% of the IMVC) but did not analyse the gluteus maximus.
Guided squat on Smith machine
In one study, activation patterns were the same as those reported in the high-bar squat (Schwanbeck et al.,
2009). In the study of Blanpied et al. (1999) major activation levels were observed on the gluteus maximus
than on the quadriceps or the hamstring. The effects of a technical modification (i.e. feet placed in line with
the body or ahead) when performing a guided squat are presented in the following section.
Low-bar squat
The study of McCaw and Melrose (1999) was the only one that analysed the activation levels in a low-bar
squat and met the eligibility criteria. The main activity was observed on the vastus lateralis and medialis,
followed by the rectus femoris. Lower activity on the hip adductors and gluteus in comparison to the
quadriceps was observed, the activity of these last two muscles being similar. The lowest activation levels
were detected on the biceps femoris. Further analyses of this squat variation were based on technical
modifications as shown further below (see “technical modifications” section).
Technical modifications
Range of motion
The comparison between three different depths (i.e. partial, parallel, and full squats) yielded similar activation
patterns, with controversial results observed on the gluteus activation. While Caterisano et al. (2002)
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observed a slightly higher activation on the gluteus in the full-ROM squats in comparison to the other two
modalities, other authors found no differences, or even higher gluteus activity values in the parallel squats
(da Silva et al., 2017; Hammond et al., 2016). The effect of this technical modification was only assessed in
the high-bar squat.
Stance width
This technical modification was included in the analysis of the high-bar (Escamilla et al., 2001; Paoli et al.,
2009) and the low-bar (McCaw & Melrose, 1999) squat. The main effect of having a wider stance was a
higher activation on the gluteus (McCaw & Melrose, 1999; Paoli et al., 2009). Variations on the stance width
did not produce an effect on the activation of the quadriceps, hamstring, and gastrocnemius (Escamilla et al.,
2001).
Hip rotation
Different hip rotations (i.e. orientation plane of the foot or knees) were only tested in high-bar squats. The
main results of this technical modification were an increase in the activity of the hip adductors (Pereira et al.,
2010). No significant effects of different hip rotations on the quadriceps were observed (Boyden et al., 2000).
Feet placement in line with the body or ahead
This technical modification was only tested in the guided squat, as this machine allows the subject to place
the feet in line with the body or ahead. When the feet were placed in line with the body major activity on the
quadriceps (i.e. normal activity pattern of a high-bar squat) was observed. In turn, when the feet were placed
in front of the body line, higher activity was detected on the gluteus and hamstrings compared to the
quadriceps (Blanpied, 1999).
Table 3. Quality assessment of the included studies.
Author (year)
1
2
3
4
5
6
Total
Bautista (2019)
+
+
+
+
+
+
6
Andersen (2019)
+
+
+
+
+
+
6
Delgado (2019)
+
+
+
+
+
+
6
Wu (2019)
+
+
+
+
+
+
6
Korak (2018)
+
+
+
+
+
+
6
Elliasen (2018)
+
+
+
+
+
+
6
McCurdy (2018)
+
+
+
+
+
+
6
Iversen (2017)
+
-
+
+
+
+
5
da Silva (2017)
+
+
+
+
+
+
6
Contreras (2016)
+
+
+
+
+
+
6
Hammond (2016)
+
+
+
+
+
+
6
Contreras (2015)
+
+
+
+
+
+
6
Yavuz (2015)
+
+
+
+
+
+
6
Aspe (2014)
+
+
+
+
+
+
6
Van den Tillar (2014)
+
-
+
+
+
+
5
Andersen (2014)
+
+
+
+
+
+
6
Gorsuch (2013)
+
+
+
+
+
+
6
Lynn (2012)
+
+
+
+
+
+
6
Robbins (2011)
+
+
+
+
+
+
6
Pereira (2010)
+
+
+
+
+
+
6
Fauth (2010)
+
+
+
+
+
+
6
Gene-Morales, et al. / Muscular activation with squat exercises JOURNAL OF HUMAN SPORT & EXERCISE
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Ebben (2009)
+
+
+
+
+
+
6
Schwanbeck (2009)
+
+
+
+
+
+
6
Gullett (2009)
+
+
+
+
+
+
6
Paoli (2009)
+
+
+
+
+
+
6
Caterisano (2002)
+
+
+
+
+
+
6
Escamilla (2001)
+
+
+
+
+
+
6
Boyden (2000)
+
+
+
+
+
+
6
Wright (1999)
+
+
+
+
+
+
6
Blanpied (1999)
+
+
+
+
+
+
6
McCaw (1999)
+
+
+
+
+
+
6
DISCUSSION
This study aimed to gather data on the muscular activation of the lower limb during five different variations of
the squat exercise (i.e. high-bar squat, front squat, overhead squat, guided squat, and low-bar squat), looking
forward to identifying the main muscle group involved and the variation with the higher activation levels. In
the following lines, the main findings are going to be compared and discussed following the scientific body of
knowledge.
In summary, almost all the studies found the major activity on the anterior thigh muscles, which are involved
in the knee extension and are part of the quadriceps (vastus lateralis, vastus medialis, and rectus femoris),
with the highest activation observed on the vastus lateralis. Only Andersen et al. (2014) and Gullet et al.
(2009), reported higher activation levels on the hamstrings than on the quadriceps, in the front squat and
high-bar squat, respectively. These uneven results may be due to the secondary function of the hamstrings
as hip extensors (Netter, 1999). Also, the hamstrings (biceps femoris, semitendinosus, semimembranosus)
are not actual antagonists in the squat exercise, but contract with the quadriceps in their function of stabilizing
the tibia and the knee joint (Schoenfeld, 2010). However, hamstrings activation should be only moderate
during the squat performance (Escamilla et al., 2001). Regarding the comparison between the gluteus and
hamstrings, there is some controversy on which has a higher activation (see “results: high-bar squat” section,
and Table 2). Attending to the squat biomechanics, the gluteus act as a powerful hip extensor and also as a
knee and hip stabilizer. Gluteus activation mainly depends on the force arm length which is conditioned by
different technique factors such as the depth, the stance width (McCaw & Melrose, 1999; Paoli et al., 2009;
Schoenfeld, 2010). Concerning the calves, low activation levels have been observed in comparison to the
thigh muscles. Attending to their main functions (Netter, 1999), these lower levels of activation may reside in
the use of stable surfaces to perform the squat and the limited contribution of the ankle muscles in the squat
movement.
As can be seen in the results, there are technical and electromyographical variations when the position of
the bar changes (Pham et al., 2020). For instance, the load in the performance of a high-bar squat, a front
squat, or an overhead squat, is shared between the knees and the hips (Comfort et al., 2018), with the main
focus on the vastus lateralis and medialis as knee extensors (Aspe & Swinton, 2014; Contreras et al., 2015,
2016; Delgado et al., 2019; Ebben et al., 2009; Hammond et al., 2016). In turn, a higher hip involvement has
been reported in the low-bar squat (Glassbrook et al., 2017, 2019; Wretenberg et al., 1996). In this variation,
the trunk inclination is greater, and thus, gluteus and hip extensors activity is enhanced in comparison to
other variations of the squat exercise. However, the low-bar squat stills a knee-extensors dominant exercise
(McCaw & Melrose, 1999). Further research on the electromyographic activity of this squat variation is
needed to better understand the neuromuscular processes involved.
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Comparing the activation levels of each variation
Firstly, it is important to bear in mind that higher levels of muscle activation are enhanced in the squat exercise
with increasing loads (Aspe & Swinton, 2014; Boyden et al., 2000; McCaw & Melrose, 1999; Paoli et al.,
2009). The lever arm between the external load (i.e. the barbell) and the centre of mass of the body plays an
important role in this regard (Gullett et al., 2009).
In the low-bar squat the lever arm is relatively shorter, and the position of the bar (below the acromion) is
more biomechanical favourable than in the rest of the variations (Glassbrook et al., 2017, 2019; Wretenberg
et al., 1996; see figure 2). Due to these abovementioned facts, the low-bar squat is the variation in which
higher loads can be used, and thus, higher activation levels may be achieved. No significant differences were
observed between the activation in a high-bar squat and a front squat (Gullett et al., 2009; Korak et al., 2018)
and thus, both would be classified at the same level after the low-bar squat. These authors reported similar
knee extension momentum, and comparable gluteus implication has been reported in both variations of the
squat exercise (Neto et al., 2020). Concerning the overhead squat, lower muscle activity on the lower limb
has been observed in comparison to the aforementioned variations. This is due to the greater involvement of
the upper body to hold the bar and stabilize the spine during the execution (Aspe & Swinton, 2014; Bautista,
2019). Moreover, there are many factors such as the strength and shoulder mobility, which limit the load used
in this exercise. Understanding that load increases entail increases in activation level (Aspe & Swinton, 2014;
Boyden et al., 2000; McCaw & Melrose, 1999; Paoli et al., 2009), this squat variation would be positioned
after the low-bar squat, the high-bar, and the front squat. Finally, Schwanbeck et al. (2009), Blanpied (1999),
and Clark et al. (2012) in their revision of the literature pointed the guided squat as the variation provoking
the lowest activation levels. One possible explanation for these results would be the nature of a guided
exercise, eliminating most of the activity of the stabilizers.
Technical factors involved
Apart from the total load used, the depth has been shown to influence muscle activity patterns and the level
of activation. In this line, lower activation levels were observed in partial squats (i.e. approximately 45º of
knee movement) compared to the parallel or full range of motion squats (Gorsuch et al., 2013; Hammond et
al., 2016). Similarly, Paoli et al. (2010) observed in their study that a reduction in the ROM decreased muscle
activation levels on the shoulder when performing a military press. This finding relates to ours and
strengthens the idea that a greater ROM entails a greater muscle activation. In terms of the influence of the
ROM on the muscle activity pattern, no significant conclusions could be extracted from the analyses, with
contrary findings among the reviewed articles (Caterisano et al., 2002; da Silva et al., 2017; Hammond et al.,
2016; Neto et al., 2020). The stance width is another parameter that influences the muscle activity patterns
in the squat. For instance, the hamstrings, gluteus maximus, and the hip adductor have all shown significantly
greater activity in the wider stance squat compared with the narrow stance (Escamilla et al., 2001; McCaw &
Melrose, 1999; Paoli et al., 2009). One of the main functions of the gluteus maximus is hip abduction (Netter,
1999) and thus, a wider stance facilitates this action of the gluteus. No other muscle activity was altered with
varying stance widths (Escamilla et al., 2001). Finally, the rotation of the hips has been shown to increase
the activation of the hip adductors (Pereira et al., 2010), with no significant changes in the activation patterns
of the rest of the analysed muscles (Boyden et al., 2000).
Limitations
The included studies have some limitations that should be listed. In this regard, none of the studies indicate
what type of isometric contraction (e.g. pushing or holding; Schaefer & Bittmann, 2017) performed the
subjects to obtain the isometric maximum voluntary contraction to standardize the results. In this line, it is
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worth mentioning that standardization values are uneven, and this may entail a problem when trying to
compare and discuss results. Also, one study found significant differences between the upper and lower
fibres of the gluteus (Contreras et al., 2016). These differences between fibre bundles of the same muscle
may condition the EMG results and thus, measurement procedures should be clearly stated in future studies.
Finally, and even all the procedures of the present review were carefully carried out it is not free of limitations.
The standardization made in the values by the authors may limit the analysis of each phase of the execution
(i.e. eccentric and concentric). Future studies should review the literature comparing the activation in each
phase. Also, the disparities between the included studies may carry to limited comparisons and extraction of
conclusions. Finally, our inclusion criteria did not include variable resistance or different bar-types. These
factors may provide the strength and conditioning professionals and athletes to further understanding of squat
exercises.
CONCLUSION
This study highlights the importance of studying the neuromuscular acute effects of the squat to deeply
understand the exercise and its variations and individualize resistance exercise programs. In brief, we
observed that the squat, independently of the variation performed, is a knee-extensor dominant exercise.
Different variations entailed different activation pattern, and activation levels. The low bar squat was the
variation with higher activation levels due to the possibility of using a higher load. This movement has a
considerable involvement of the hip muscles. High-bar squat and front squat provoked similar activation
patterns due to having a similar lever arm. In this regard, the lever arm is greater in the overhead squat and
thus, the activation levels are lesser (due to a limited capacity of using a high load). Finally, the guided squat
was the variation with lower activation levels due to not require stabilization. The evidence presented in this
study may help the strength and conditioning professionals and practitioners with the exercise selection
depending on the muscular targets and the individual characteristics of the athlete.
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... Therefore, we desire to obtain a suitable WBR design by imitating critical human bio-mechanics. Specially, we note that the squat serves as one of the most common motions in athletic and daily activities, such as load lifting [20]. To improve the torque effectiveness and increase load capability, we designed our robot by analyzing the typical barbell squat of human demonstrated in Fig. 3a. ...
... With this assumption, the OCP in (20) can be transformed into a combination of a finite-horizon time-varying LQR (TVLQR) problem parameterized by z(t),z(t), 0 < t < t s and an infinite-horizon LQR problem with z = z d ,z = 0 for t > t s . Then (20) can be transformed into the following finite-horizon linear predictive controller: ...
... With this assumption, the OCP in (20) can be transformed into a combination of a finite-horizon time-varying LQR (TVLQR) problem parameterized by z(t),z(t), 0 < t < t s and an infinite-horizon LQR problem with z = z d ,z = 0 for t > t s . Then (20) can be transformed into the following finite-horizon linear predictive controller: ...
Design and Control of a Bio-inspired Wheeled Bipedal Robot
Preprint
Full-text available
  • Aug 2023
Wheeled bipedal robots (WBRs) have the capability to execute agile and versatile locomotion tasks. This paper focuses on improving the dynamic performance of WBRs through innovations in both hardware and software development. Inspired by the human barbell squat, a bionic mechanical design is proposed and implemented as shown in Fig. 1. It distributes the weight onto its hip and knee joints to improve the effectiveness of joint motors while maintaining a relatively large workspace of the base link. Meanwhile, a novel model-based controller is devised, synthesizing height-variable wheeled linear inverted pendulum (HV-wLIP) model, Control Lyapunov Function (CLF) and whole-body dynamics for theoretically guaranteed stability and efficient computation. Compared with other alternatives, as a more accurate approximation of the WBR dynamics, the HV-wLIP can enable more agile response and provide theory basis for WBR controller design. Experimental results demonstrate that the robot could perform human-like deep squat, and is capable of maintaining tracking CoM velocity while manipulating base states. Furthermore, it exhibited robustness against external disturbances and unknown terrains even in the wild.
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... Pain and discomfort may negatively affect training and are considered a problem for powerlifters, and have been suggested to be related to factors such as inappropriate lifting technique and lifting with the joints towards their end range of motion [5]. The traditional squat requires coordinated flexion of the hips, knees, and ankles when descending prior to extension during the upwards phase, to return to the initial position [12]. If performed appropriately, the squat is considered a safe, functional movement with transfer to both sports performance and daily living [13], which has sparked interest in the investigation of the mechanics of the squat [14]. ...
... Biomechanics 2023, 4, FOR PEER REVIEW 2 inappropriate lifting technique and lifting with the joints towards their end range of motion [5]. The traditional squat requires coordinated flexion of the hips, knees, and ankles when descending prior to extension during the upwards phase, to return to the initial position [12]. If performed appropriately, the squat is considered a safe, functional movement with transfer to both sports performance and daily living [13], which has sparked interest in the investigation of the mechanics of the squat [14]. ...
... Despite a large number of exercises and barbells suggested as alternatives to the traditional back squat with an Olympic barbell, differences in biomechanics and EMG are often observed [12,14,18]. The safety squat bar has been suggested to be more ergonomic for the shoulders while requiring less inclination of the torso [14]. ...
A Biomechanical Comparison between Squatbar® and Olympic Barbell
Article
Full-text available
  • Jun 2023
When performing the traditional barbell back squat, athletes may experience discomfort in the shoulders or be limited by shoulder mobility. The Squatbar® is a barbell designed to be ergonomic to the shoulders but has never, in the scientific literature, been compared to the traditional Olympic barbell. Thus, the current study investigated kinematics, kinetics, and myoelectric activity (EMG) between the Squatbar® barbell and the Olympic barbell when performing a one-repetition maximum (1-RM) back squat. Twelve strength-trained men (body mass: 83.5 ± 7.8 kg, age: 27.3 ± 3.8 years, height: 180.3 ± 6.7 cm) performed a 1-RM squat with both the Olympic and Squatbar® barbells. The paired samples t-test revealed significantly more weight was lifted with the Olympic barbell compared to the Squatbar® barbell (148 ± 21 kg vs. 144.5 ± 20 kg) and was accompanied by greater shoulder external rotation (74 ± 7.5° vs. 59.6 ± 9.2°). No differences in joint kinematics of the lower limbs, kinetics, or EMG were observed between the two barbells. The results of the current study indicate the Squatbar® to be a suitable substitution for the Olympic barbell for athletes with reduced shoulder mobility when performing the squat. It was concluded that the Squatbar® induces similar kinetics, kinematics, and EMG when compared to the Olympic barbell, except for reducing external rotation of the shoulder.
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... Lower-body dynamic strength was assessed with a 1RM parallel squat [29,30]. Before attempting the 1RM, subjects performed three sub-maximal sets of 1-6 repetitions with light-to-moderate loads. ...
... This measure is also reported in the literature as the degree of mechanical tension [18]. The four exercises performed were the back and front half-squat [29,37], forward lunge and deadlift [15]. According to previous research [38], rest intervals of 3 min between sets were ensured in both training methods. ...
Exploring of two different equated instability resistance training programs on measure of physical fitness and lower limb asymmetry in pre-pubertal weightlifters
Article
Full-text available
  • Mar 2023
Background Although previous research in pediatric populations has reported performance enhancements following instability resistance training, the effects of different volumes on measures of balance, strength and power and lower limb asymmetry remain unclear. Objective To compare the effect of two 8-week instability resistance training programs (IRT1: 2 sets x 8 repetitions, 20% one-repetition maximum (1RM); IRT2: 2 sets x 4 repetitions, 40% 1RM) in balance (center of pressure displacements), 1RM, single-leg jumps, and inter-limb asymmetry of prepubescent weightlifters. Methods Thirty-two male athletes (10.94 ± 0.47 yrs, 17.05 ± 0.14 kg/m², and 6.44 ± 0.93% bodyfat) voluntarily participated and combined IRT (front and back squat, lunge, and deadlift) with their usual weightlifting training. Nonparametric tests evaluated the differences between pre- and post-intervention. Results Significant improvements were encountered in all the variables for both groups (effect sizes [ES] from 0.46 to 2.60), except the inter-limb asymmetry and the velocity of displacement of the center of pressure, which did not improve in IRT2. It is also worth highlighting that in the single-leg jumps and center of pressure displacements, whereas no significant differences were observed between IRT1 and IRT2 in the baseline, significant differences appeared in the follow-up measurements. Conclusion IRT combined with weight-lifting training improves prepubescent weightlifters’ performance; therefore, strength and conditioning coaches may consider including unstable devices with low loads into an overall conditioning program and warm-ups for prepuberal male weightlifters to promote their physical fitness and potentially decrease inter-limb asymmetry. Trial registration This study does not report results related to healthcare interventions using human participants; therefore, it was not prospectively registered.
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... Lower-body dynamic strength was assessed with a 1RM parallel squat [30,31]. Before attempting the 1RM, subjects performed three sub-maximal sets of 1-6 repetitions with light-to-moderate loads. ...
... This measure is also reported in the literature as the degree of mechanical tension [38]. The four exercises performed were the back and front half-squat [30,39], forward lunge and deadlift [40]. Bearing in mind that fatigue can decrease the power output and increase the risk of injury [41], rest intervals of 3 minutes between sets were ensured. ...
Exploring of Two Different Equated Instability Resistance Training Programs on Balance and Muscle Strength and Power Performance in Pre-pubertal Weightlifters
Preprint
Full-text available
  • Aug 2022
Background Although previous research in pediatric populations has reported performance enhancements following instability resistance training, the effects of different volumes on measures of balance, strength and power and lower limb asymmetry remain unclear. Objective to compare the effect of two 8-week instability resistance training programs (IRT1: 2 sets x 8 repetitions, 20% one-repetition maximum (1RM); IRT2: 2 sets x 4 repetitions, 40%1RM) in the strength (1RM), power (single-leg jumps), inter-limb asymmetry and balance (center of pressure displacements) of prepubescent weightlifters. Methods Thirty-two male athletes (10.94 ± .47 yrs, 17.05 ± .14 kg/m2 and 6.44 ± .93% body-fat) voluntarily participated and combined IRT (front and back squat, lunge and deadlift) with their usual weight-lifting training. Non-parametric tests evaluated the differences between pre- and post-intervention. Results Significant improvements were encountered in all the variables for both groups (effect sizes [ES] from 0.46 to 2.60), except the inter-limb asymmetry and the velocity of displacement of the center of pressure, which did not improve in IRT2. It is also worth highlighting that in the single-leg jumps and center of pressure displacements, whereas no-significant differences were observed between IRT1 and IRT2 in the baseline, significant differences appeared in the follow-up measurements. Conclusion IRT combined with weightlifting specific training improves the performance of prepubescent weightlifters and, therefore, strength and conditioning coaches may consider including unstable devices with low loads into an overall conditioning program and warm-ups for pre puberal male weightlifters to promote their physical fitness and potentially decrease inter-limb asymmetry. Trial registration This study does not report results related to health care interventions using human participants and therefore it was not prospectively registered.
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... A partial high-bar back squat [35] was performed with 30 kg and 40 kg according to previous research [33]. The range of movement was standardized with a goniometer from the standing position of the participants to 90 • of knee flexion. ...
An Integrated Approach to Explore Interlimb Asymmetries, Neuromuscular Parameters, and Injuries in Semiprofessional Soccer Players
Article
Full-text available
  • Nov 2024
Interlimb asymmetries have been widely studied with controversial results, suggesting that the magnitude of asymmetries is highly task-dependent and could be related to injury risk. This study aimed to establish an optimal method for assessing asymmetries and evaluate interlimb power performance and range of motion asymmetries in injured and non-injured male semiprofessional soccer players. A prospective and descriptive design was applied, and 20 male semiprofessional soccer players participated. The players underwent a battery of screening tests (i.e., countermovement jump [CMJ], half-squat, hip abduction and hip adduction isometric force, knee flexion and extension isokinetic torque, and lower limb range of movement). The healthy players had a greater range of motion in the hip extension and ankle flexion of the dominant leg and hip abduction and knee flexion of the non-dominant leg. However, the injured players exhibited greater asymmetry in hip abduction maximum isometric strength. These findings suggest the importance of establishing a comprehensive method to assess the range of motion interlimb asymmetries related to injury risk in semiprofessional soccer players.
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... The Squat, as a natural functional movement of the body, is a strength exercise at the same time. Athletes use it to improve their performance and, in the case of clinical patients, to improve their health in everyday activities (26). In clinical settings, the squat strengthens lower-body muscles and connective tissue after jointrelated injury (27). ...
Effects of an integrative warm-up method on the range of motion, core stability, and quality of squat performance of young adults
Article
Full-text available
  • Mar 2024
Introduction This research aims to determine the effects of an integrative warm-up method on the range of motion in joints of the lower extremities, the strength of the stabilizer trunk muscles, and the quality of the basic movement patterns in older adolescents. Methods The study sample consisted of 88 male students (age 20.1 ± 0.5). They were randomly divided into four groups: one control group (CG) (n = 17; 180.8 ± 7.9 cm; 82.3 ± 8.3 kg) and three experimental groups (EG): EG1 (n = 23; 180.9 ± 7.0 cm; 78.5 ± 9.5 kg), EG2 (n = 31; 182.2 cm ± 7.3 cm; 79.5 ± 11.5 kg), and EG3 (n = 17; 183.3 ± 4.9 cm; 77.5 ± 11.8 kg). The participants were subjected to a 6-week experimental treatment: EG1 once, EG2 twice, and EG3 three times a week. The experimental treatment consisted of four sub-phases representing the integrative warm-up Method: 1) Inhibition (self-myofascial release using a foam roller); 2) Lengthening (Static stretching in a maximum range of motion position); 3) Activation (Positional isometrics muscle activation of the trunk and gluteus); 4) Integration (Integrated all the previous phases into one complex movement pattern). Based on the covariance analysis (ANCOVA), statistically significant treatment effects were observed and positive changes were determined in all experimental groups. Results The differences between groups were observed in the following variables: Overhead Squat Assessment (p = 0.000; ηp2=0.318), range of motion of left hip flexion (p = 0.000; ηp2=0.371), range of motion of right hip flexion (p = 0.000; ηp2=0.051) and range of motion of right hip extension (p = 0.051; ηp2=0.088), Double Leg Lowering Test (F = 2.411; p = 0.014; ηp2=0.014) and range of combined motion (plantar and dorsiflexion) of left ankle joint (p = 0.000; ηp2=0.299). There was no significant difference in the Plank Test (F = 1.007; p = 1.007; ηp2=0.035), range of combined motion (plantar and dorsiflexion) of right ankle joint (p = 0.088; ηp2=0.170) and range of motion of left hip extension (p = 0.158; ηp2=0.060). The participants of CG statistically significantly differed from EG1, EG2, and EG3 in the squat performance after the applied treatment. Discussion The effect of the treatment was the occurrence of a transformational processes in almost all measured variables. It can be concluded that the integrative method is effective and applicable in practice for both young adults and recreational athletes.
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... Participants were taken through a progressive warmup which allowed for discussion and practise of minimum knee flexion (90°) to be considered a standardised repetition [71,72]. Participants were encouraged to hold onto the handles to anchor themselves into the chair, to brace, and were asked to maintain contact with their head, shoulders, back, and pelvis against the chair during the repetitions. ...
Comparison of low-dose maximal-intent versus controlled-tempo resistance training on quality-of-life, functional capacity, and strength in untrained healthy adults: a comparative effectiveness study
Article
Full-text available
  • Mar 2024
Lack of physical activity is a global issue for adults that can lead to sedentary behaviour and a higher prevalence of health complications and chronic diseases, resulting in reduced quality-of-life (QoL) and functional capacity (FC). A potential strategy to mitigate this inactivity is low-dose resistance training (RT); however, physiological, and psychological responses are limited in evidence. Twenty untrained participants aged 30–60 years old (mean ± SD age 42 ± 7 years, mass 77 ± 13 kg, stature 166 ± 8 cm; 18 females and two males) were recruited and randomly assigned to maximal velocity-intent (MI, n = 10) or controlled-tempo (CT, n = 10) RT according to CONsolidated Standards of Reporting Trials (CONSORT) guidelines. Participants attended one training session per week for 6 weeks, consisting of five sets of five repetitions at 60% of one-repetition maximum (1RM) leg press. The interventions differed only during the concentric phase, with MI group pushing with maximal intent, and CT group pushing in a time-controlled manner (3 s). Outcome measures assessed pre- and post-RT included body mass, body mass index (BMI), strength-to-mass ratio, bipedal balance, 6-minute walk test (6MWT), 30-second sit-to-stand (30s-STS), timed up and go (TUG), and leg press 1RM. Time effects were observed for all demographics and FC-related outcomes, such as identical reductions in mass and BMI (− 2%), improvements in strength-to-mass ratio (25%) leg press 1RM (22%), 6MWT (3%), and 30s-STS (14%), as well as a 9% improvement in both TUG-clockwise and anticlockwise. Results show low-dose once-weekly RT is effective in improving QoL, FC, and strength in untrained healthy adults, regardless of modality. Positive responses from participants suggest an increased likelihood of consistent participation for low-dose once-weekly RT over more intense modalities. Retrospective ClinicalTrials.gov ID (TRN): NCT06107855, 24/10/2023.
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... For instance, in the sports biomechanics literature, it has been noted that high-force deadlift and squat exercises may affect the kinematics of the trunk and lower extremities and the patterns of muscle coactivation [12,13,14]. The biomechanical variety of physical activities can alter joint mechanics and accompanying muscular activity, affecting exercise responses [15]. ...
The effects of stance width during barbell hip thrust on power and velocity output among adolescent Silat athletes
Article
Full-text available
  • Oct 2023
Background and Study Aim. In the physically demanding combat sport of Silat, strength and power dominate. Consequently, applying various stance widths during barbell hip thrusts may tailor athletes' lower-body exercises to individual needs. This has the potential to optimize performance. The aim of this study is to investigate the impact on performance of power, speed, and stance width among Silat combat athletes. Material and Methods. Participants performed 10RM tests in three stance widths: wider than shoulder width (WSW), normal shoulder width (NSW), and narrower than shoulder width (NRW). This was done using a 72-hour counterbalance cross-over study design. Power and velocity were measured and analyzed using a mixed ANOVA design. Results. The results indicated a significant main effect of stance width on power (F(2,56) = 3.086, p < 0.05) and velocity (F(2,56) = 3.683, p < 0.03) output. Both males and females demonstrated the highest power in NRW (M = 413.26, SD = 131.76; M = 239.53, SD = 111.16), followed by WSW and NSW. A strong positive correlation between power and velocity was observed for all stance widths: WSW (r(28) = 0.77, p < 0.001), NSW (r(28) = 0.79, p < 0.001), and NRW (r(28) = 0.89, p < 0.001). NRW was associated with superior power production, while WSW facilitated higher velocity. Conclusion. The results of this study demonstrate the importance of considering a variety of stance width techniques during exercise due to their effects on power and velocity during the barbell hip thrust exercise. Coaches can tailor training programs with a velocity-targeted strength and conditioning approach to enhance performance and competitiveness. Further research should investigate different athlete groups and age levels to refine training methodologies.
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... From these items, central and peripheral pathways involved in performance and fatigue are explained (Taylor et al., 2016). Accordingly, as exercise training leads to morphological, biochemical, and functional adaptations, training variables may be cautiously selected for maximizing the desired effects (Gene-Morales, Flandez, et al., 2020;Gene-Morales, Gené-Sampedro, et al., 2020;Halson, 2014). ...
Effects of an elastomeric technology garment on different external and internal load variables: A pilot study
Article
Full-text available
  • Jan 2023
Resistance training is one key method for improving physical conditioning. With this purpose, Menatechpro System® has designed an avant-garde garment that includes elastomeric technology that may stimulate the neuromuscular system in a better way, but a deeper knowledge of its effects is needed. Objective: To explore the effects of a new garment with elastomeric technology on upper-limb performance, and neuromuscular, perceptual, and cardiovascular responses in two upper-extremities exercises. Methodology: Fit young men trained in resistance exercises performed a seated shoulder press (80% of one-repetition maximum) and push up (bodyweight) until muscle failure with the garment that incorporates the elastomeric technology versus a placebo garment without it. The number of repetitions, mean propulsive velocity, mean and peak muscle activation, rate of perceived effort and perceived velocity, and heart rate were analysed. Possible differences were obtained with a two-way mixed ANOVA of repeated measures with post-hoc analysis. Results: Compared with a placebo garment, the use of this new garment with elastomeric technology improved positively the physical performance and muscular activation during the exercises analysed (p ≤ .05). Conclusion: Menatechpro System®'s elastomeric technology integrated into the garment could provide an optimal neuromuscular stimulus for the development of the performance during the upper extremity training.
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... A Smith machine (Powerline, PSM14X, Body-Solid, Chicago, IL, USA) was used to perform parallel squats [23]. Elastic bands (CLX bands, TheraBand ® ; Hygenic Corporation, Akron, OH, USA) or weight plates (ranging from 1.25 to 20 kg; Olive, Manresa, Spain) were used to load the barbell. ...
The Use of Elastic Bands in Velocity-Based Training Allows Greater Acute External Training Stimulus and Lower Perceived Effort Compared to Weight Plates
Article
Full-text available
The objective was to compare the mean propulsive velocity (MPV), maximum power (PMAX), heart rate, and rate of perceived exertion (RPE) during the parallel squat using elastic bands (EB) or weight plates (WP) to load the bar. The effect of relative strength on the dependent variables was analysed. Additionally, the potential of the RPE to predict external load parameters was assessed. Eighteen trained volunteers squatted at 40%, 55%, 70%, and 85% of their one-repetition maximum with EB and WP (a total of eight sets) in random order. Dependent variables were measured at the first and last repetition (i.e., 10% velocity loss). Two identical sessions were conducted to assess the reliability of measurements. Compared to WP, EB allowed a significantly greater number of repetitions, MPV, and PMAX, and significantly lower RPE. The RPE of the first repetition was a significant predictor of the external load of the set. The RPE showed good repeatability and was not influenced by the relative strength of athletes. In conclusion, compared to WP, the use of EB allows for greater external load with reduced internal load responses in a wide spectrum of load-based intensities. The potential implications of these novel findings are discussed in the manuscript.
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Gluteus Maximus Activation during Common Strength and Hypertrophy Exercises: A Systematic Review
Article
Full-text available
  • Mar 2020
  • J SPORT SCI MED
The gluteus maximus (GMax) is one of the primary hip extensors. Several exercises have been performed by strength and conditioning practitioners aiming to increase GMax strength and size. This systematic review aimed to describe the GMax activation levels during strength exercises that incorporate hip extension and use of external load. A search of the current literature was performed using PubMed/Medline, SportDiscuss, Scopus, Google Scholar, and Science Direct electronic databases. Sixteen articles met the inclusion criteria and reported muscle activation levels as a percentage of a maximal voluntary isometric contraction (MVIC). The exercises classified as very high level of GMax activation (>60% MVIC) were step-up, lateral step-up, diagonal step-up, cross over step-up, hex bar deadlift, rotational barbell hip thrust, traditional barbell hip thrust, American barbell hip thrust, belt squat, split squat, in-line lunge, traditional lunge, pull barbell hip thrust, modified single-leg squat, conventional deadlift, and band hip thrust. We concluded that several exercises could induce very high levels of GMax activation. The step-up exercise and its variations present the highest levels of GMax activation followed by several loaded exercises and its variations, such as deadlifts, hip thrusts, lunges, and squats. The results of this systematic review may assist practitioners in selecting exercised for strengthening GMax.
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Comparison Between Back Squat, Romanian Deadlift, and Barbell Hip Thrust for Leg and Hip Muscle Activities During Hip Extension
Article
Full-text available
  • Jul 2019
Delgado, J, Drinkwater, EJ, Banyard, HG, Haff, GG, and Nosaka, K. Comparison between back squat, romanian deadlift, and barbell hip thrust for leg and hip muscle activities during hip extension. J Strength Cond Res XX(X): 000-000, 2019-This study compared muscle activities of vastus lateralis (VL), biceps femoris (BF), and gluteus maximus (GM) during the back squat (SQ), Romanian deadlift (RDL), and barbell hip thrust (BHT) exercises performed with the same load (60 kg) and at one repetition maximum (1RM). Eight men with a minimum of 1 year's lower-body strength training experience performed the exercises in randomized order. Before each exercise, surface electromyography (EMG) was recorded during a maximal voluntary isometric contraction (MVIC) and then used to normalize to each muscle's EMG during each trial. Barbell hip thrust showed higher GM activity than the SQ (effect size [ES] = 1.39, p = 0.038) but was not significantly different from RDL (ES = 0.49, p = 0.285) at 1RM. Vastus lateralis activity at 1RM during the SQ was significantly greater than RDL (ES = 1.36, p = 0.002) and BHT (ES = 2.27, p = 0.009). Gluteus maximus activity was higher during MVIC when compared with the 60 kg load for the SQ (ES = 1.29, p = 0.002) and RDL (ES = 1.16, p = 0.006) but was similar for the BHT (ES = 0.22, p = 0.523). There were no significant differences in GM (ES = 0.35, p = 0.215) and BF activities (ES = 0.16, p = 0.791) between 1RM and MVIC for the SQ. These findings show that the RDL was equally as effective as the BHT for isolating the hip extensors, while the SQ simultaneously activated the hip and knee extensors.
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Optimizing Squat Technique - Revisited
Article
Full-text available
  • May 2018
The back squat is the cornerstone of many strength and conditioning programs, with increases in back squat strength associated with improvements in athletic performance. a variety of back squat techniques have been described throughout the literature and can be observed on social media and in strength and conditioning facilities, with no current consensus regarding optimal technique. basedoncurrently available evidence, a full depth squat, with a natural foot position, approximately shoulder-width apart, with unrestricted anterior movement of the knees, an upright trunk, with a forward and upward gaze is recommended. these recommendations should permit individualization based on individual anthropometrics. for a video abstract of this article, see supplemental digital content 1 (See video, http://links.lww.com/scj/a241).
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Biomechanical, Anthropometric, and Psychological Determinants of Barbell Back Squat Strength
Article
Full-text available
  • Feb 2018
Previous investigations of strength have only focused on biomechanical or psychological determinants, while ignoring the potential interplay and relative contributions of these variables. The purpose of this study was to investigate the relative contributions of biomechanical, anthropometric, and psychological variables to the prediction of maximum parallel barbell back squat strength. Twenty-one college-aged participants (male = 14; female = 7; age = 23 ± 3 years) reported to the laboratory for two visits. The first visit consisted of anthropometric, psychometric, and parallel barbell back squat one-repetition maximum (1RM) testing. On the second visit, participants performed isometric dynamometry testing for the knee, hip, and spinal extensors in a sticking point position-specific manner. Multiple linear regression and correlations were used to investigate the combined and individual relationships between biomechanical, anthropometric, and psychological variables and squat 1RM. Multiple regression revealed only one statistically predictive determinant: fat free mass normalized to height (standardized estimate ± SE = 0.6 ± 0.3; t(16) = 2.28; p = 0.037). Correlation coefficients for individual variables and squat 1RM ranged from r = -0.79-0.83, with biomechanical, anthropometric, experiential, and sex predictors showing the strongest relationships, and psychological variables displaying the weakest relationships. These data suggest that back squat strength in a heterogeneous population is multifactorial and more related to physical rather than psychological variables.
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Multiple-joint exercises using elastic resistance bands vs. conventional resistance-training equipment: A cross-over study
Article
Full-text available
  • Jun 2017
Previous studies indicate that elastic resistance bands (ERB) can be a viable option to conventional resistance-training equipment (CRE) during single-joint resistance exercises, but their efficacy has not been established for several commonly used multiple-joint resistance exercises. Thus, we compared muscular activation levels in four popular multiple-joint exercises performed with ERB (TheraBand®) vs. CRE (Olympic barbell or cable pulley machines). In a cross-over design, men and women (n = 29) performed squats, stiff-legged deadlifts, unilateral rows and lateral pulldown using both modalities. Multilevel mixed-effects linear regression analyses of main and interaction effects, and subsequent post hoc analyses were used to assess differences between the two resistance-training modalities. CRE induced higher levels of muscle activation in the prime movers during all exercises (p < .001 for all comparisons), compared to muscle activation levels induced by ERB. The magnitude of the differences was marginal in lateral pulldown and unilateral rows and for the erector spinae during stiff-legged deadlifts. In squats the quadriceps femoris activations were substantially lower for ERB. The differences between ERB and CRE were mostly observed during the parts of the contractions where the bands were relatively slack, whilst the differences were largely eliminated when the bands became elongated in the end ranges of the movements. We conclude that ERB can be a feasible training modality for lateral pulldowns, unilateral rows and to some extent stiff-legged deadlifts, but not for the squat exercise.
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Technical Aspects and Applications of the Low-Bar Back Squat
Article
  • Dec 2019
The low-bar back squat (LBBS) is a barbell squat variation that emphasizes hip musculature through use of forward lean. This characteristic, among others, allows greater loads to be lifted and can facilitate rehabilitation in a compromised knee joint. Correct technique should be instructed to promote proper execution. This article aims to discuss the anatomical and technical differences between the high-bar back squat and LBBS, define LBBS-specific technique, and provide practitioners strategies to select the best version for their lifters.
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Effect of Loading Devices on Muscle Activation in Squat and Lunge
Article
  • Jan 2019
Context: Squats and lunges are common exercises frequently applied in muscle-strengthening and therapeutic exercises. The loading devices are often used to increase the training intensity. Objective: To determine the effect of loading devices on muscle activation in squat and lunge and to compare the differences in muscle activation between squat and lunge. Design: Cross-sectional cohort. Participants: Nineteen healthy, male, recreationally active individuals without a history of lower limb injury. Interventions: Each participant performed 10 repetitions of a squat under 5 conditions: unloaded, barbell, dumbbell, loaded vest, and kettlebell, and 10 repetitions of a lunge under 4 conditions: unloaded, barbell, dumbbell, and loaded vest. Main outcome measures: The electromyography signals of quadriceps, hamstrings, tibialis anterior, gastrocnemius lateralis and medialis were measured. One-way repeated-measure analysis of variance was used to compare the difference among different loading conditions. Paired t test was used to compare the difference between squat and lunge. Results: The muscle activation in the loaded conditions was significantly higher than that in nonloaded conditions in squat and lunge. Compared with the barbell, dumbbell, and loaded vest conditions, the semitendinosus showed significantly higher activation, and the tibialis anterior showed significantly lower activation in kettlebell condition in squat. No significant difference in muscle activation was found among barbell, dumbbell, and kettlebell conditions in lunge. In addition, quadriceps and hamstring activities were significantly higher in lunge than in squat. Conclusions: Muscle activation was affected by the loading devices in squat but not affected in lunge. Kettlebell squat could be suggested for targeting in strengthening medial hamstring. Progressive strengthening exercise could be recommended from squat to lunge based on sequential activation level.
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Muscle Activation Patterns of Lower-Body Musculature Among 3 Traditional Lower-Body Exercises in Trained Women.
Article
  • Oct 2018
The deadlift and back and front squats are common multijoint, lower-body resistance exercises that target similar musculature. To our knowledge, muscle activity measured using surface electromyography has never been analyzed among these 3 exercises. Furthermore, most literature examining this topic has included male participants creating a void in the literature for the female population. Knowledge of lower-body muscle activation among these 3 exercises can aid coaches, trainers, and therapists for training and rehabilitative purposes. Trained women (n = 13) completed 2 days of testing including a 1-repetition maximum (1RM) estimation, an actual 1RM, and 3 repetitions at 75% 1RM load for the deadlift and back and front squats. Muscle activity of the 3 repetitions of each muscle was averaged and normalized as a percentage to the 1RM lifts for the deadlift and front and back squats. Five separate repeated-measure analysis of variances were performed indicating muscle activity of the gluteus maximus (GM) differed among the 3 exercises (p = 0.01, (Equation is included in full-text article.)= 0.39). Specifically, post hoc analysis indicated greater muscle activity during the front squat (M = 94%, SD = 15%) compared with the deadlift (M = 72%, SD = 16%; p ≤ 0.05) in the GM. No significant differences were observed among the lifts in the vastus medialis, vastus lateralis, biceps femoris, and rectus femoris. Strength and conditioning specialist and trainers can use these findings by prescribing the front squat to recruit greater motor units of the GM.
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COMPARISON OF BILATERAL AND UNILATERAL SQUAT EXERCISES ON BARBELL KINEMATICS AND MUSCLE ACTIVATION
Article
  • Aug 2018
  • Int J Sports Phys Ther
Purpose/background: Bilateral squats are commonly used in lower body strength training programs, while unilateral squats are mainly used as additional or rehabilitative exercises. Little has been reported regarding the kinetics, kinematics and muscle activation in unilateral squats in comparison to bilateral squats. Therefore, the purpose of this study was to compare muscle activity, kinetics, and barbell kinematics between unilateral and bilateral squats with the same external load per leg in experienced resistance-trained participants. Methods: Fourteen resistance-trained males (age 23 ± 4years, body mass 80.5 ± 8.5kg and height 1.81 ± 0.06m) participated. Barbell kinematics and surface electromyography (EMG) activity of eleven muscles were measured during the descending and ascending phase of each repetition of the squat exercises. Results: Total lifting time was longer and average and peak velocity were lower for the bilateral squat (p<0.001). Furthermore, higher muscle activity was found in the three quadriceps muscles, biceps femoris (ascending phase) and the erector spinae (ascending phase) in the bilateral squat, while greater activation for the semitendinosis (descending phase) (p=0.003) was observed for the unilateral squat with foot forwards. In the ascending phase, the prime movers showed increased muscle activity with repetition from repetition 1 to 4 (p≤0.034). Conclusions: Unilateral squats with the same external load per leg produced greater peak vertical ground reaction forces than bilateral squats, as well as higher barbell velocity, which is associated with strength development and rate of force development, respectively. The authors suggest using unilateral rather than bilateral squats for people with low back pain and those enrolled in rehabilitation programs after ACL ruptures, as unilateral squats are performed with small loads (28 vs. 135 kg) but achieve similar magnitude of muscle activity in the hamstring, calf, hip and abdominal muscles and create less load on the spine. Level of evidence: 1b.
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Gluteus Maximus and Hamstring Activation During Selected Weight-Bearing Resistance Exercises
Article
  • Oct 2017
McCurdy, K, Walker, J, and Yuen, D. Gluteus maximus and hamstring activation during selected weight-bearing resistance exercises. J Strength Cond Res XX(X): 000-000, 2017-The purpose of this study was to compare the gluteus maximus (GM) and hamstring group (HG) electromyographic (EMG) activation levels among selected weight-bearing resistance exercises. Eighteen young adult females with previous resistance training experience completed the study. Strength was assessed on the bilateral squat (BS) (3 repetition maximum [RM]), modified single-leg squat (MSLS) (3RM), and stiff-leg deadlift (SLDL) (8RM) to determine an 8RM load for all lifts. Surface EMG was collected after 48 hours of rest using wireless Trigno IM Sensors using EMMA software (Delsys), which also collected and synchronized 3D hip and knee motion. A maximum voluntary isometric contraction was determined for the GM and HG to normalize the EMG data. During EMG data collection, 3 repetitions were completed using an 8RM load on all 3 exercises. Gluteus maximus EMG was significantly greater than HG EMG on the BS (40.3 vs. 24.4%, p < 0.001), MSLS (65.6 vs. 40.1 %, p < 0.012), and SLDL (40.5 vs. 29.9 %, p < 0.047). The MSLS produced significantly greater HG EMG (p = 0.001) compared with the SLDL, whereas the SLDL was significantly greater (p = 0.004) than the BS. The MSLS GM EMG was also significantly greater (p < 0.001) than the SLDL and BS, whereas no difference was found between the SLDL and BS. Comparing the activation of the 2 muscle groups in all exercises, the GM seems to be the primary muscle recruited whereas the MSLS seems to produce greater GM and HG activation. The data indicate that it would be most beneficial to include the MSLS during GM and HG training.
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