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The aim of this study was to investigate the acute effects on maximal isometric force without and with two kinds of knee wraps (hard and soft) during squat exercise. Ten physical active participants were evaluated during this study. All subjects were familiarized with the isometric squat position in all conditions: without and with knee wrap (hard and soft stiffness). The squat exercise position was set up individually, guaranteeing their thigh parallel to the floor, the arms crossed on the chest, and the feet were kept always in the same position for all trials and conditions. All subjects performed three maximal isometric squat contractions in 3 different conditions: without knee wrap (WKW), with soft knee wrap (SKW) and with hard knee wrap (HKW). The peak of force was acquired at a 100Hz sampling frequency, during 3 seconds, 5 minutes of resting and all conditions were randomized. The results shows significant differences for peak force between conditions WKW and HKW (P=0.029, ES=1.27, Δ%=22%]) and WKW and SKW (P=0.038, ES=1.20, Δ%=21%]). The use of the knee wrap under the presented conditions seem to increase the maximal isometric force during the squat exercise, independent of the level of stiffness of the knee wrap.
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International Journal of Sports Science 2014, 4(2): 47-49
DOI: 10.5923/j.sports.20140402.02
Acute Effects on Maximal Isometric Force with and
without Knee Wrap During Squat Exercise
Willy Andrade Gomes, Érica Paes Serpa, Enrico Gori Soares, Josinaldo Jarbas da Silva,
Daniel Corrêa, Fernando Henrique Domingues de Oliveira, Francisco de Abreu Neto,
Gustavo Martins, Guanis de Barros Vilela Junior, Paulo Henrique Marchetti*
Department of Human Movement Sciences, Methodist University of Piracicaba, Piracicaba, São Paulo, Brazil
Abstract The aim of this study was to investigate the acute effects on maximal isometric force without and with two
kinds of knee wraps (hard and soft) during squat exercise. Ten physical active participants were evaluated during this study.
All subjects were familiarized with the isometric squat position in all conditions: without and with knee wrap (hard and soft
stiffness). The squat exercise position was set up individually, guaranteeing their thigh parallel to the floor, the arms crossed
on the chest, and the feet were kept always in the same position for all trials and conditions. All subjects performed three
maximal isometric squat contractions in 3 different conditions: without knee wrap (WKW), with soft knee wrap (SKW) and
with hard knee wrap (HKW). The peak of force was acquired at a 100Hz sampling frequency, during 3 seconds, 5 minutes of
resting and all conditions were randomized. The results shows significant differences for peak force between conditions
WKW and HKW (P=0.029, ES=1.27, Δ%=22%]) and WKW and SKW (P=0.038, ES=1.20, Δ%=21%]). The use of the knee
wrap under the presented conditions seem to increase the maximal isometric force during the squat exercise, independent of
the level of stiffness of the knee wrap.
Keywords Biomechanics, Exercise performance, Strength
1. Introduction
The knee wrap is an equipment commonly used by
weightlifters and powerlifters aiming to stabilize the knee, to
improve the strength performance (gain mechanical
advantage) or to improve the confidence during squat
exercises [1, 2]. The knee wrap is a long wrap of elastic
material (tick canvas interwoven with rubber filaments) with
approximately 2 meter long, which is wrapped around the
knees as tight as possible [3, 4]. There are some studies that
investigated both kinematics and kinetics of the squat
exercise using the knee wrap in powerlifters [5, 6] and
trained subjects [4], however little has been known about its
effects of loading capacity. Eiter et al. [5] studied the use of
knee wrap in powerlifters and analyzed the general
characteristics of the squat exercise (execution time,
percentage of the transition cycle (upward-downward
displacement) of the center of mass and the bar vertical
displacement) with and without knee wrap, with no
differences between them. Lake et al. [4] studied the use of
knee wrap in trained subjects with and without knee wrap.
The authors analyzed the ground reaction force, output of the
* Corresponding author:
dr.pmarchetti@gmail.com (Paulo Henrique Marchetti)
Published online at http://journal.sapub.org/sports
Copyright © 2014 Scientific & Academic Publishing. All Rights Reserved
mechanical force applied to the center of mass, vertical
impulse, horizontal displacement of the bar, mechanical
work and peak power. They observed that the elastic
properties of the knee wrap increased the production of
mechanical force by changing the squat technique.
In general, when the knee is flexed against an external
resistance during a squat exercise, the elastic material is
stretched during the lowering phase, returning this energy
during the lifting phase. This potenctial energy accumulated
is transferred to the lifter and added to the strength
performance of the movement in the concentric phase [1],
and this additional effect on the strength performance is also
known as carry-over. Only two studies reported the amount
of carry-over of 19.8% in elite powerlifters [6] and 25,1% in
subjects trained [3], respectively, during squat exercise.
However, little is known about the effects of different
models (stiffness) of knee wrap in the peak force during the
squat exercise and how much carry-over can actually be
related to the knee wrap instead of the stretch-shortening
cycle. Therefore, the purposes of the present study was to
compare the acute effects on maximal isometric force
without knee wrap and two kinds of knee wrap stiffness
(hard and soft) during squat exercise.
2. Methods
Subjects
48 Willy Andrade Gomes et al.: Acute Effects on Maximal Isometric Force
with and without Knee Wrap During Squat Exercise
Ten physical active participants were evaluated during this
study (age 24±3 years, body mass 79.9±9kg, height
175.7±3cm). All subjects were engaged in regular resistance
training routine (hypertrophy loads: 3-4 exercises for lower
limbs, 8-12 maximum repetitions) including squat exercise
(2 sessions per week) for not less than one year. The number
of subjects was determined by using the same variable from
our pilot study, and ten subjects were showed to be necessary
based on alpha level of 0.05 and a power (1-β) of 0.80 [7].
All subjects who participated in this study had no previous
trunk or lower limbs surgery/injury and they were evaluated
with a minimum of 48 hours without training sessions. All
the participants were instructed about the potential risks
involved, read and signed an institution-approved
informed-consent form before participating in the study. The
study was approved by the ethics committee of Methodist
University of Piracicaba (Protocol: 76/12).
Procedures
Initially, all subjects were familiarized with the isometric
squat position in all conditions: without and with knee wrap
(hard and soft stiffness). The squat exercise position was set
up individually, guaranteeing their thigh parallel to the floor,
the arms crossed on the chest, and the feet were always kept
in the same position for all trials and conditions. A load cell
(CEFISE biotecnologia esportiva, Nova Odessa, Brazil) was
attached perpendicularly to the ground and in subject’s hip
by using a belt. Then, each subject performed three maximal
isometric squat contractions in 3 different conditions:
without knee wrap (WKW), with soft knee wrap (SKW) and
with hard knee wrap (HKW). For the placement of the knee
wrap we used a spiral technique as described by Coutinho [6],
always by the same researcher. The peak of force was
acquired by CEFISE software at a 100Hz sampling
frequency, during 3 seconds and 5 minutes between
contractions and conditions. All conditions were randomized
and collected in one session. All the data were analyzed with
a customized program written in Matlab (Mathworks Inc.,
EUA). The peak of force was filtered with a 4th-order 10 Hz
low-pass zero-lag, Butterworth filter.
Statistical Analyses
Normality and homogeneity of variances within the data
were confirmed by the Shapiro-Wilk and Levene tests,
respectively. To compare the effects of using knee wrap
(WKW, SKW and HKW) a repeated measures ANOVA
were employed. Post-hoc comparisons were performed by
using the Bonferroni test. Cohen’s formula for effect size
(ES) was used and the results were based in the following
criteria: <0.35 trivial effect; 0.35-0.80 small effect; 0.80-1.50
moderate effect; and >1.5 large effect, for recreational
trained according to Rhea [8]. An alpha of 5% was used for
all statistical tests. The ICC was test for all trials for each
conditions (WKW= 0.96; HKW= 0.96; SKW= 0.98).
3. Results
There were significant differences between peak force and
conditions: WKW and HKW (P=0.029, ES=1.27, Δ%=22%])
and WKW and SKW (P=0.038, ES=1.20, Δ%=21%]).
However, it was not observed significant differences
between kinds of knee wraps (P=0.98). Figure 1 shows the
mean and standard deviations of the peck force values for the
three testing conditions.
Figure 1. Mean ± standard deviation of the peak of force during isometric
squat for different conditions (without knee wrap, high knee wrap and soft
knee wrap, respectively). *P<0.05
4. Discussion
The aim of this study was to compare the effect by using
different models of knee wrap (hard and soft) in peak force
of trained subjects while performing a maximum voluntary
isometric contraction (MVIC) in the squat exercise. There
were differences between the conditions HKW and WKW (P
<0.029) and between conditions WKW x SKW (P <0.038),
resulting in a carry-over of 22% (ES = 1.27) and 21% (ES =
1.20) respectively, corroborating the findings of Harman and
Frykman [3].
Related to carry-over effect observed during our study, we
could verify an increase in the external load, that was due to
the elastic energy stored in the knee wrap material under
mechanical deformation [6]. The knee wrap is composed of
elastomeric material and polyester, and it has the ability to
suffer large deformations and return elastically to its original
shape, as springs. This elastic effect is due to the crosslink of
the polymer, which, when stretched, results in a force
capable of returning the material strands to their original
conformations without any permanent deformation (plastic
deformation) [9]. So, this elastic energy can be transferred
into kinetic energy and added to the lifter [6].
Curiously, we did not observe any difference on the force
of peak between the models of knee wrap (hard x soft). This
similarity can be related to the number of laps to involve the
knees. The soft knee wrap allowed a higher number of laps
when compared to hard knee wrap (approximately, two laps).
Probably, the higher number of laps, in the soft knee wrap,
can result in a higher number of elastic fibers in parallel,
adding elastic energy and compensating the greater
resistance of the hard knee wrap [10]. This hypothesis is
based on the principle of laminated composites cited by
International Journal of Sports Science 2014, 4(2): 47-49 49
Callister [9], which states that the sum of composite layers
stacked one on top of the other, resulting in a relatively high
resistance. According to specifications of the manufacturer
both wraps are composed of 70% polyester and 30%
elastodiene. However, factors such as the arrangement or
orientation of the fibers have a significant influence on the
strength and other properties of fiber reinforced composites
[9]. It is important to emphasize that, for both models (SKW
and HKW), we used the same placing technique by the same
investigator. The present study analyzed the maximal
isometric squat exercise aiming to verify the carry-over
effect without elastic components of the muscle
(stretch-shortening cycle, SSC). Previous studies analyzed
the squat exercise with and without knee wrap in a dynamic
condition. However, the carry-over effect can be influenced
by the combination of both, SSC and elastic energy of the
knee wrap [11], in addition to that the velocity of motion
execution can affect the SSC response [12].
5. Conclusions
The acute effect on maximal isometric force during squat
exercise was to present an effective carry-over during the
squat exercise by using the knee wrap. For coaches, athletes
and sport science practitioners the use of knee wrap under the
presented conditions seem to increase the maximal isometric
force during the squat exercise, independent of level from
stiffness of knee wrap.
Conflict of Interest
There were no conflicts of interest for conducting this
study.
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Equilibrium, Motion, and Deformation. 2 ed1998, New York:
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... Because heavy loads are typically borne during the back squat exercise, many athletes choose to perform their squat activities using external supports [4]. Knee wraps and knee sleeves are commonly adopted by those involved in competitive and recreational resistance training [5]. As described by Lake et al. [3], knee wraps are typically made from thick canvas with interwoven rubber filaments to provide elasticity. ...
... Knee wraps and sleeves are utilised to mediate a mechanical advantage during the back squat exercise [5]. They are adopted by both competitive and recreational lifters to enhance performance during the squat exercise [3]. ...
... There was also a significant increase in gluteus maximus muscle activity when wearing knee wraps but only at 60% 1RM, and a significant increase in peak knee flexion at both 60 and 90% 1RM. Gomes et al. [5] examined the effects of hard and soft knee wraps on the peak vertical ground reaction force (GRF) produced during an isometric squat. This study showed that peak vertical GRF was significantly greater in both hard and soft knee wraps compared to performing without wraps. ...
Article
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Purpose The aim of the current investigation was to comparatively examine the effects of knee wraps/sleeves on kinetics, three-dimensional kinematics and muscle forces during the barbell back squat. Methods Fifteen male lifters completed squats at 70% of their 1 repetition maximum, in four different conditions (nothing, competition knee wrap, training knee wrap and knee sleeve). Three-dimensional kinematics were measured using an eight-camera motion analysis system, ground reaction forces using a force platform and muscle forces using musculoskeletal modelling techniques. Differences between conditions were examined using one-way repeated measures ANOVA. Results The results showed that the integral of the quadriceps (nothing = 58.30, competition = 51.87 and training wrap = 53.33 N/kg s), hamstring (nothing = 39.01, competition = 35.61 and training wrap = 33.97 N/kg s), gluteus maximus (nothing = 24.29, competition = 22.22 and training wrap = 21.03 N/kg s), gastrocnemius (nothing = 7.25, competition = 5.97 and training wrap = 6.39 N/kg s) and soleus muscles (nothing = 15.49, competition = 12.75 and training wrap = 13.64 N/kg s) during the ascent phase was significantly greater in the nothing condition compared to both knee wraps. In addition, whilst knee wraps and knee sleeves significantly improved perceived knee stability, perceived comfort was significantly reduced in the knee wraps and improved in the knee sleeve. Conclusions Taking into account the reduced muscle kinetics, knee wraps may diminish lower extremity muscle development. Therefore, knee sleeves may be more efficacious for athletes who regularly utilise the back squat for their training goals, although further longitudinal analyses are required before this can be fully established.
... Diversos estudos investigaram os efeitos do uso da banda elástica no desempenho. [4][5][6][7][8][9] Gomes et al., 6 verificaram um aumento de 21 e 22% no pico de força durante o agachamento isométrico máximo com diferentes modelos de banda elástica (Soft e Hard, respectivamente). Marchetti et al., 9 também verificaram aumento no pico de força durante o agachamento isométrico máximo, independentemente da técnica de colocação da banda elástica (em espiral: 10,8% em "X": 13,6%). ...
... Diversos estudos investigaram os efeitos do uso da banda elástica no desempenho. [4][5][6][7][8][9] Gomes et al., 6 verificaram um aumento de 21 e 22% no pico de força durante o agachamento isométrico máximo com diferentes modelos de banda elástica (Soft e Hard, respectivamente). Marchetti et al., 9 também verificaram aumento no pico de força durante o agachamento isométrico máximo, independentemente da técnica de colocação da banda elástica (em espiral: 10,8% em "X": 13,6%). ...
... 1,8 Assim, pesar de diversos estudos evidenciarem aumento do desempenho quando a banda elástica foi utilizada, tais estudos investigaram apenas seus efeitos no complexo articular de joelho e durante a realização do exercício agachamento. 1,2,[4][5][6][7][8][9] Sendo assim, o objetivo do presente estudo foi investigar os efeitos agudos do uso da banda elástica de cotovelos no desempenho de força máxima e submáxima, no volume absoluto e percepção subjetiva de esforço/desconforto durante o exercício supino reto livre. A hipótese principal considera que o uso da banda elástica de cotovelos aumenta o desempenho máximo e submáximo do exercício supino, assim como afeta negativamente a percepção de esforço. ...
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RESUMO Introdução: A banda elástica é muito utilizada por diferentes tipos de atletas e por praticantes de treina-mento de força recreacionais, no intuito de melhorar o desempenho no levantamento de cargas. Objetivo: Investigar os efeitos agudos do uso da banda elástica de cotovelos no desempenho de força, no volume absoluto e percepção subjetiva de esforço durante o exercício supino reto livre. Métodos: Na primeira visita, foi realizada a familiarização com o exercício supino reto livre com banda (CB) e sem banda (SB) elástica de cotovelos. Na segunda visita, foi realizado o teste de 1RM no exercício supino reto livre, nas condições CB e SB. Na terceira visita, foi realizado o teste de repetições máximas até a falha concêntrica (RMs) a 70% de 1RM (CB e SB). Após cada teste, os sujeitos foram questionados quanto a sua percepção subjetiva de esforço (PSE) e de desconforto (PSD). Teste t de student pareado foi utilizado para comparar os valores de 1RM e RMs, com e sem banda elástica. Para a PSD e a PSE foram utilizadas análises descritivas. Resultados: No teste de 1RM foi verificado um aumento significante para a condição CB, quando comparado à condição SB (P<0,05). No teste de RMs e cálculo do volume absoluto, foi verificado um aumento significante para a condição CB (P<0,05). A PSE não apresentou diferenças em todas as condições testadas (P>0,05). A PSD apresentou alto grau de des-conforto apenas com banda elástica em todas as condições. Conclusão: A banda elástica de cotovelos aumenta a carga levantada no teste de 1RM e o número de repetições máximas durante o exercício supino reto livre e, consequentemente, no volume absoluto. A banda elástica não altera a percepção subjetiva do esforço, mas aumenta o desconforto durante o exercício.
... 3,4 A BEJ, de forma geral, funciona como um agente ergogênico que através da deformação elástica do material acumula energia elástica e potencial gravitacional (durante a fase descendente do agachamento) e consequentemente, aumenta sua capacidade de carregamento na fase ascendente, esse efeito de força adicional é conhecido como carry over. 1 Apesar da BEJ ser extensamente utilizada no treinamento de força, apenas três estudos investigaram o efeito carry over da BEJ na produção de força, sendo um estudo com o agachamento dinâmico em powerlifters (19,8%), 5 um estudo com sujeitos treinados em força durante o agachamento passivo (25,1%) 3 e um estudo em sujeitos treinados em força durante o agachamento isométrico máximo (21-22%). 6 Adicionalmente, Lake et al., 4 ± 5,17), sexo masculino, entrenado en fuerza (> 1 año). Fueron realizadas tres contracciones máximas voluntarias extensoras de rodilla (MVIC), de cinco segundos por 10 segundos de intervalo entre intentos para cada condición experimental: control (C), con las vendas eláticas de rodillas (EKW), y con tensor (T). ...
... Os resultados mostram que a banda elástica apresentou um efeito carry over ~74,21% maior do que a condição controle e 79,37% maior do que o tensor. Estes achados corroboram com os resultados obtidos por Harman e Frykman 3 e Gomes et al., 6 que verificaram um efeito carry over de ~25% durante o agachamento passivo (sob suspensão) e de 22% durante o agachamento isométrico máximo, respectivamente. No entanto, o efeito carry over verificado no presente estudo foi consideravelmente maior do que o observado nos estudos supracitados. ...
... 20 Já durante a realização do exercício agachamento isométrico máximo, a resistência externa é composta por aproximadamente 87% do peso corporal 20 (tronco, membros superiores, pescoço e cabeça). Assim, entende-se que o efeito carry over produzido pela banda pode ser afetado pelo tipo de exercício realizado, visto que a banda utilizada nesse experimento foi da mesma marca e modelo da utilizada por Gomes et al., 6 Entre as condições controle e tensor não foram observadas diferenças significantes, concluindo que as características mecânicas da órtese não contribuíram para o efeito carry over como verificado também por Marchetti et al., 12 Por outro lado, tanto o pico de força quanto o impulso foram maiores para a condição controle do que para a condição banda (12,2% e 8%, respectivamente), não corroborando com os achados de Gomes et al., 6 que verificou um aumento no pico de força de 22 e 21% (carry over) durante o agachamento isométrico máximo com banda. No entanto, o presente estudo avaliou o efeito da BEJ durante o exercício extensão de joelho removendo o efeito de força adicional produzido pela banda (efeito carry over). ...
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Introdução: A banda elástica de joelhos (BEJ) é um equipamento utilizado por powerlifters, weightlifters e sujeitos treinados em força, com o objetivo de estabilizar a articulação do joelho e aumentar o desempenho da força (efeito carry over). Objetivo: Comparar os efeitos do uso da banda elástica de joelhos na atividade muscular de vasto lateral (VL) e na força de extensores de joelhos, durante a contração voluntária máxima iso-métrica (CVMI) na cadeira extensora. Métodos: Participaram do estudo 18 sujeitos saudáveis (idade: 25,56 ± 4,84 anos, massa corporal total: 81,83 ± 8,73 kg, estatura: 176 ± 5,17 cm), do gênero masculino, treinados em força (> 1 ano). Foram realizadas três contrações voluntárias máximas (CVMI's de extensores de joelho, de cinco segundos por 10 segundos de intervalo entre as tentativas, para cada condição experimental: controle (C); com banda elástica de joelhos (BEJ); e com tensor (T). Foram avaliados o desempenho de extensores de joelho e a atividade muscular de VL. Uma ANOVA com medidas repetidas foi utilizada para comparar as variáveis dependentes (carry over; pico de força, IEMG e Impulso). Resultados: Para o carry over, o uso da BEJ apresentou maior valor (74,21%) quando comparada a condição controle (P<0,001, d=0,96) e 79,37% maior do que o tensor (P<0,001, d=0,97). O pico de força foi 12,2% maior na condição C comparado à BEJ (P=0,018, d=0,71). Para o impulso, a condição controle apresentou um aumento de 8% comparado ao uso da BEJ (P=0,015, d=0,62). Para a IEMG não foram observadas diferenças significantes. Conclusão: O uso da banda elástica de joelhos aumentou a capacidade de produção de força durante a extensão de joelho. A remoção do efeito mecânico proveniente do carry over, durante a CVMI, reduz o desempenho de força dos extensores de joelho, mas não a ativação muscular do VL. Nível de Evidência I; Estudos terapêuticos-Investigação dos resultados do tratamento.
... Several studies have investigated the effects of using the elastic wrap in performance. [4][5][6][7][8][9] Gomes et al., 6 verified a 21 and 22% increase in peak force during maximum isometric squatting with different elastic band models (Soft e Hard, respectively). Marchetti et al., 9 also observed an increase in peak force during maximum isometric squatting, regardless of the technique of elastic wrap placement (in spiral: 10,8% in "X": 13,6%). ...
... Several studies have investigated the effects of using the elastic wrap in performance. [4][5][6][7][8][9] Gomes et al., 6 verified a 21 and 22% increase in peak force during maximum isometric squatting with different elastic band models (Soft e Hard, respectively). Marchetti et al., 9 also observed an increase in peak force during maximum isometric squatting, regardless of the technique of elastic wrap placement (in spiral: 10,8% in "X": 13,6%). ...
... 1,8 So, although several studies showed an increase in performance when the elastic wrap was used, such studies only investigated its effects on the knee joint complex and during the exercise of the squat exercise. 1,2,[4][5][6][7][8][9] Therefore, the objective of the present study was to investigate the acute effects of elbow wrap on maximal and submaximal strength performance, absolute volume and Rating of perceived exertion/discomfort during the bench press exercise. The main hypothesis considers that the use of elastic wrap of elbows increases the maximum and submaximal performance of the bench press exercise, as well as negatively affects the perception of effort. ...
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Introduction: The elastic wrap is widely used by different types of athletes and recreational practitioners of strength training in order to improve weightlifting performance. Objective: The objective was to investigate the acute effects of elbow wrap on strength performance, absolute volume, and rating of perceived exertion/discomfort during the bench press (BP) exercise. Methods: The experimental protocol was divided into three laboratory sessions. At the first session, a bench press familiarization phase was performed with (EW) and without (WEW) elastic elbow wrap. During the second session, the 1RM test was carried out in the bench press exercise under both EW and WEW conditions. At the third session, the repetition maximum (RM) test at 70% of 1RM (EW and WEW) was performed until concentric failure. After each session, subjects were consulted about their rate of perceived exertion (RPE), and discomfort (PSD). A paired student t-test was used to compare the values of 1RM and RMs with and without elastic wraps. Descriptive analysis was used for RPE and PSD. Results: For the 1RM test, there was a significant increase for the EW condition when compared to WEW (p<0.05). In the RMs test and absolute volume calculation, there was a significant increase for the EW condition (p<0.05). RPE did not differ in any of the conditions tested (p>0.05). PSD presented a high degree of discomfort with elastic wraps in all conditions. Conclusion: Elastic elbow wraps increase the load lifted in the 1RM test, and the maximum number of repetitions during the BP exercise, and consequently, the absolute volume. The elastic elbow wrap does not alter the subjective perception of effort, but it increases discomfort during exercise.
... 3,4 The EKW, in general, works as an ergogenic agent that through elastic deformation of the material accumulates elastic energy and gravitational potential (during the descending phase of the squat) and consequently increases its loading capacity in the ascending phase, additional force effect known as carry over. 1 Although EKW was extensively used in strength training, only three studies investigated the EKW's carry over effect on strength production, with a dynamic squatting study in powerlifters (19,8%), 5 a study with strength-trained subjects during passive squatting (25,1%) 3 and a study in subjects trained in strength during maximum isometric squatting (21-22%). 6 Additionally, Lake et al., 4 compared the effect of EKW use on kinetic and kinematic variables during squatting in subjects trained in strength. In this study was study the soil reaction force, the mechanical force production applied to the center of mass, the vertical impulse, the horizontal displacement of the bar, the mechanical work and the power peak. ...
... The results show that the elastic wrap presented a carry over effect ~ 74.21% higher than the control condition and 79.37% higher than the tensor. These findings corroborate the results obtained by Harman e Frykman 3 and Gomes et al., 6 who verified a carry over effect of ~ 25% during passive squatting (under suspension) and 22% during maximum isometric squat, respectively. However, the carry over effect found in the present study was considerably higher than that observed in the aforementioned studies. ...
... However, the carry over effect found in the present study was considerably higher than that observed in the aforementioned studies. 3,6 It is probable that EKW contributed with a greater mechanical magnitude during extension of knees in the extensor chair due to the lower external resistance involved during the task (leg and foot segments), which are equivalent to approximately 9.6 and 3.4 % of body weight, respectively. 20 While performing the maximal isometric squatting exercise, the external resistance is composed of approximately 87% of body weight 20 (trunk, upper limbs, neck and head). ...
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Introduction: The elastic knee wrap (EKW) is a device used by powerlifters, weightlifters and subjects undergoing strength training with the aim of stabilizing the knee joint and increasing the development of strength (carryover effect). Objective: To compare the effects of elastic knee wrap use on muscular activity of the vastus lateralis (VL) and on knee extension force during maximum voluntary isometric contraction (MVIC) on the knee extensor chair. Methods: The study included 18 healthy male strength trained (>1 year) subjects (age: 25.56 ± 4.84 years, total body mass: 81.83 ± 8.73 kg, height: 176 cm ± 5.17). Three five-second maximum voluntary isometric contractions (MVICs) of the knee extensors were performed with a 10-second interval between attempts, for each experimental condition: control (C), with elastic knee wrap (EKW), and with tensor (T). The performance of the knee extensors and VL muscle activity were evaluated. A repeated measures ANOVA was used to compare the dependent variables (carryover, peak force, IEMG and Impulse). Results: For carryover, the use of EKW presented a higher value (74.21%) than the control condition (p <0.001, d = 0.96) and was 79.37% higher than the tensor (p <0.001, d = 0.97). Peak force was 12.2% higher in condition C compared to EKW (p = .018, d = 0.71). For impulse, the control condition presented an increase of 8% compared to EKW use (p = .015, d = 0.62). No significant differences were observed for IEMG. Conclusion: Elastic knee wrap use increased strength production capacity during knee extension. The removal of the mechanical effect originating from carryover during MVIC reduces the strength performance of the knee extensors, but not the muscular activation of the VL. Level of Evidence I; Therapeutic studies - Investigation of treatment results.
... In this case, the passive tension of the KT is the additional force produced by the material proprieties, and might be added to the contractile force to produce improvement in performance. [39][40][41][42] Therefore, the purpose of this study was to measure the acute effects of KT in static rest, and during knee extension maximal voluntary isometric contraction (MVIC) performance in resistance trained men. The null hypotheses of the present study are: (1) KT will not affect passive tension during static rest; and (2) KT will not affect muscle activation or force output during an MVIC. ...
... 50 This additional effect on strength is known as passive tension of the material. [39][40][41][42] To the best of authors' knowledge, this was the first study to analyze passive tension during the rest condition with the knee flexed. This might help to evaluate any significant additional aid in performance that occurs from the KT. ...
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Background: Kinesiology Tape (KT) is widely used in sports rehabilitation and by those performing physical activity, however, there is no consensus in the scientific literature about its effectiveness on performance, strength or muscle activation. Purpose: The purpose of this study was to measure the acute effects of KT in static rest, and during knee extension maximal voluntary isometric contraction (MVIC) performance in resistance trained men. Study Design: Observational, descriptive, comparative. Methods: Eighteen young, healthy, trained males (age: 25±6 years, height: 176.0±5 cm, and mass: 81.8±8.0 kg) volunteered to participate. Initially, they were in a relaxed sitting position of 90 degrees knee flexion with their limb supported by the machine lever arm to measure passive tension of the tissues of the knee joint. Then, they performed three MVIC trials of five seconds each with a three-minute rest between trials, in four randomized experimental conditions, with 10-min rest between conditions: (a) control, no taping; (b) Knee Sleeve; (c) KT; and (d) sham. During all MVICs, peak force, impulse, and muscle activation of the vastus lateralis (integrated electromyography [IEMG] and median frequency) were measured. Results: Repeated measures ANOVAs revealed no statistical differences between conditions for passive tension (p>0.05), peak force (p>0.05), impulse (p>0.05), IEMG (p>0.05), or median frequency (p>0.05). Conclusion: KT does not influence passive tension during static position at 90 degrees of knee flexion. KT does not affect quadriceps activation or force production during a maximal voluntary isometric contraction in the same position.
... All KWs were new and not previously used. The "spiral figure" wrapping technique was used on both legs (3,8,14). The same researcher applied the wraps as tightly as possible immediately before each trial, standardizing the number of wrap revolutions to 9 per subject. ...
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Gomes, WA, Brown, LE, Soares, EG, da Silva, JJ, Silva, FHDdO, Serpa, ÉP, Corrêa, DA, Vilela Junior, GdB, Lopes, CR, and Marchetti, PH. Kinematic and sEMG analysis of the back squat at different intensities with and without knee wraps. J Strength Cond Res 29(9): 2482-2487, 2015-The purposes of this study were to measure the acute effects of knee wraps (KWs) on knee and hip joint kinematics, dynamic muscle activation from the vastus lateralis (VL) and gluteus maximus (GM), and rating of perceived exertion (RPE) during the back squat exercise at 2 different intensities. Fourteen resistance-trained men (age: 24 ± 4 years, height: 176 ± 6 cm, body mass: 81 ± 11 kg, back squat 1 repetition maximum [1RM]: 107 ± 30 kg, 3 ± 1 year of back squat experience) performed 1 set of 3 repetitions under 4 different conditions, to a depth of approximately 90 degrees of knee joint flexion, and in random order: KWs at 60% 1RM (KW60), KWs at 90% 1RM (KW90), without knee wraps (NWs) at 60% 1RM (NW60), and NWs at 90% 1RM (NW90). The dependent variables obtained were vertical and horizontal bar displacement, peak joint angle in the sagittal plane (hip and knee joints), concentric and eccentric muscle activation (by integrated electromyography) from the VL and GM, and RPE. For muscle activity, there were significant decreases in the VL NWs at 60% 1RM (p = 0.013) and a significant increase NWs at 90% 1RM (p = 0.037). There was a significant increase in VL muscle activity at 90% 1RM, when compared with 60% 1RM (KW: p = 0.001, effect size (ES) = 1.51 and NW: p < 00.001, ES = 1.67). There was a decrease in GM muscle activity NWs only at 60% 1RM (p = 0.014). There was a significant increase in GM muscle activity at 90% 1RM, when compared with 60% 1RM (KW: p < 0.001 and NW: p < 0.001). For peak hip joint flexion angle, there was significant decreases between intensities (90% 1RM < 60% 1RM) only to NWs condition (p = 0.009), and there was greater knee flexion NWs for both intensities: 60% 1RM (p < 0.001) and 90% 1RM (p = 0.018). For normalized vertical barbell displacement, there were significant differences between intensities when using KWs (p = 0.022). There were significant differences in RPE between 60 and 90% 1RM for each condition: KWs (p < 0.001) and NWs (p < 0.001). In conclusion, the use of KWs results in decreased muscle activation of the VL at the same intensity (90% 1RM).
Article
Knee wraps (KW) can be used as an ergogenic aid during the back squat to increase training volume and load. Previous investigations have examined carry‐over effect during the back squat, though the amount of torque produced at the knee due to the KWs remains unknown. Therefore, this investigation examined the influence of KWs on passive torque production, and its relationship to knee circumference. Nine resistance trained men performed two, 5s passive isometric knee extensions with (KW) and without (UW) knee wraps at nine different angles (70°,75°,80°,85°,90°,95°,100°,105°, and 110°). Data were analyzed via two‐way repeated measures ANOVA to assess differences between conditions, while Pearson Product‐Moment correlations were used to assess the relationship between torque production and knee circumference. A significant interaction was observed for passive torque, revealing differences between all angles in KW (p≤0.05), while differences during UW were only observed at angles greater than 90° (p≤0.05). Paired samples t‐tests indicated differences between conditions at every angle except 70° (p≤0.05). Knee circumference was not correlated to torque production at any angle (r = ≤ 0.411, p > 0.272). These results demonstrate the applicability of KW to passively increase torque produced at the knee during extension, independent of knee circumference.
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INTRODUÇÃO: A banda elástica pode afetar o desempenho durante exercícios de alta intensidade, reduzindo a ativação muscular, o que pode influenciar o efeito de potencialização pós-ativação, que depende de alta intensidade para o exercício subsequente que visa potência. Objetivo: Verificar os efeitos agudos no desempenho do salto com contramovimento (SCM) após o agachamento em alta intensidade com e sem o uso da banda elástica de joelhos em sujeitos treinados em força. MÉTODOS: Participaram do estudo 14 homens (idade: 24 ± 4 anos, estatura: 176 ± 6 cm, massa corporal: 81 ± 11 kg, 1RM: 107 ± 30 kgf), treinados em força (>3 anos). Foram realizados três SCM antes e após três meio-agachamentos a 90% de 1RM nas condições com e sem a banda elástica de joelhos. Durante o SCM foram avaliados ativação muscular (IEMG) do vasto lateral (VL), glúteo máximo (GM), tempo de salto (TS) e impulso (IMP) por meio da força vertical de reação do solo (FRSv). RESULTADOS: Os resultados mostraram que para o TS foi verificada diferença significante entre as condições pós-meio-agachamento (com e sem banda) (P = 0,044, TE = 1,02), sendo que os maiores valores foram observados para a condição sem banda. Para a IEMG de VL foi verificada diferença significante entre as condições pré e pós o meio-agachamento (com banda) (P = 0,029, TE = 1,68), sendo que os maiores valores foram observados para a IEMG com banda. Para a IEMG de GM e para o IMP não foram verificadas diferenças significantes entre as condições. CONCLUSÃO: Após a utilização da banda elástica de joelhos durante o exercício agachamento, ocorreu uma redução na participação do vasto lateral durante o salto com contramovimento, afetando o tempo de contato, mas não a produção de impulso, e consequente desempenho.
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RESUMO Introdução: A banda elástica pode afetar o desempenho durante exercícios de alta intensidade, redu-zindo a ativação muscular, o que pode influenciar o efeito de potencialização pós-ativação, que depende de alta intensidade para o exercício subsequente que visa potência. Objetivo: Verificar os efeitos agudos no desempenho do salto com contramovimento (SCM) após o agachamento em alta intensidade com e sem o uso da banda elástica de joelhos em sujeitos treinados em força. Métodos: Participaram do estudo 14 homens (idade: 24 ± 4 anos, estatura: 176 ± 6 cm, massa corporal: 81 ± 11 kg, 1RM: 107 ± 30 kgf), trei-nados em força (>3 anos). Foram realizados três SCM antes e após três meio-agachamentos a 90% de 1RM nas condições com e sem a banda elástica de joelhos. Durante o SCM foram avaliados ativação muscular (IEMG) do vasto lateral (VL), glúteo máximo (GM), tempo de salto (TS) e impulso (IMP) por meio da força vertical de reação do solo (FRSv). Resultados: Os resultados mostraram que para o TS foi verificada diferença significante entre as condições pós-meio-agachamento (com e sem banda) (P = 0,044, TE = 1,02), sendo que os maiores valores foram observados para a condição sem banda. Para a IEMG de VL foi verificada diferença significante entre as condições pré e pós o meio-agachamento (com banda) (P = 0,029, TE = 1,68), sendo que os maiores valores foram observados para a IEMG com banda. Para a IEMG de GM e para o IMP não foram verificadas diferenças significantes entre as condições. Conclusão: Após a utilização da banda elástica de joelhos durante o exercício agachamento, ocorreu uma redução na participação do vasto lateral durante o salto com contramovimento, afetando o tempo de contato, mas não a produção de impulso, e consequente desempenho. Palavras-chave: força muscular, desempenho atlético, treinamento de resistência. ABSTRACT Introduction: Knee wraps can affect the muscular performance during high-intensity exercises by reducing muscle activation, which may influence the effect of post-activation potentiation, which depends on high intensity for the following power exercise. Objective: To investigate the acute effects on the performance with counter-movement jump (CMJ) after high-intensity squat with and without the use of knee wraps in resistance trained subjects. Methods: The study included 14 men (aged 24±4 years, height: 176±6cm, weight: 81±11kg, 1RM: 107±30kgf) resistance trained (>3 years). Three SCM were performed before and after three back squats at 90% of 1RM with and without the knee wraps. During the CMJ muscle activation (IEMG) of the vastus lateralis (VL) and gluteus maximus (GM), jump time (JT), and impulse (IMP) through the force of vertical ground reaction (FRSV) were evaluated. Results: The results show statistically significant differences for JT between post-back-squat conditions (with and without wrap) (P=0.044, TE=1.02), whereas the highest values were observed without knee wrap. For IEMG of VL significant difference between pre and post-conditions after back squat (with knee wrap) (P=0.029, TE=1.68) was observed, and the highest values were observed for the IEMG with knee wrap. No significant differences between conditions were observed for IEMG of GM and IMP. Conclusion: After using the knee wraps during the squat exercise, there was a reduction in the involvement of the vastus lateralis during the jump with counter-movement, affecting the contact time, but not the production of impulse and consequent performance.
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This paper reviews the research findings regarding the force and length changes of the muscle-tendon complex during dynamic human movements, especially those using ultrasonography and computer simulation. The use of ultrasonography demonstrated that the tendinous structures of the muscle-tendon complex are compliant enough to influence the biomechanical behavior (length change, shortening velocity, and so on) of fascicles substantially. It was discussed that the fascicles are a force generator rather than a work generator; the tendinous structures function not only as an energy re-distributor but also as a power amplifier, and the interaction between fascicles and tendinous structures is essential for generating higher joint power outputs during the late pushoff phase in human vertical jumping. This phenomenon could be explained based on the force-length/velocity relationships of each element (contractile and series elastic elements) in the muscle-tendon complex during movements. Through computer simulation using a Hill-type muscle-tendon complex model, the benefit of making a countermovement was examined in relation to the compliance of the muscle-tendon complex and the length ratio between the contractile and series elastic elements. Also, the integral roles of the series elastic element were simulated in a cyclic human heel-raise exercise. It was suggested that the storage and reutilization of elastic energy by the tendinous structures play an important role in enhancing work output and movement efficiency in many sorts of human movements.
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"Bridging the Gap" is a continuing feature of the NSCA Journal. Various topics are presented with companion articles addressing the physiological and/or research basis, as well as the practical applications. In this way, the NSCA Journal continues to bridge the gap between sports researchers and sports practitioners. See page 36 for the practical application of these concepts. (C) 1990 National Strength and Conditioning Association
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The number of individuals to include in a research study, the sample size of the study, is an important consideration in the design of many clinical studies. This article reviews the basic factors that determine an appropriate sample size and provides methods for its calculation in some simple, yet common, cases. Sample size is closely tied to statistical power, which is the ability of a study to enable detection of a statistically significant difference when there truly is one. A trade-off exists between a feasible sample size and adequate statistical power. Strategies for reducing the necessary sample size while maintaining a reasonable power will also be discussed.
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In order to improve the applicability of research to exercise professionals, it is suggested that researchers analyze and report data in intervention studies that can be interpreted in relation to other studies. The effect size and proposed scale for determining the magnitude of the treatment effect can assist strength and conditioning professionals in interpreting and applying the findings of the strength training studies.
Revisão dos efeitos biomecânicos do uso de banda elástica no joelho durante o agachamento no levantamento básico
  • W A Gomes
  • M Coutinho
  • P H Marchetti
Gomes, W.A., M. Coutinho, and P.H. Marchetti, Revisão dos efeitos biomecânicos do uso de banda elástica no joelho durante o agachamento no levantamento básico.. Revista Centro de Pesquisas Avançadas em Qualidade de Vida., 2013. 5(3): p. 1-15.
Ciência e engenharia de materiais: uma introdução
  • J W D Callister
Callister, J.W.D., Ciência e engenharia de materiais: uma introdução. Vol. 7. 2008, Rio de Janeiro: LTC.
Knee wraps affect squat performance
  • J Lake
  • P Carden
  • K Shorter
Lake, J., P. Carden, and K. Shorter, Knee wraps affect squat performance. Journal of Strength and Conditioning Research, 2012. 8(1): p. 1-16.
De volta ao básico: powerlifting -treinamento funcional, esporte de alto rendimento e prática coporal para todos
  • M Coutinho
Coutinho, M., De volta ao básico: powerlifting -treinamento funcional, esporte de alto rendimento e prática coporal para todos.2011, São Paulo: Editora Phorte.