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Trindade TB, Alves RC, de Sousa NMF, Lopes C, de Castro BM, Rosa TS, Prestes J. Acute Effect of the "Zero Point" Method on Muscle Thickness and Muscle Damage in Trained Men. Sports (Basel) 2023; 12:6. [PMID: 38251280 PMCID: PMC10819921 DOI: 10.3390/sports12010006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Revised: 11/26/2023] [Accepted: 11/28/2023] [Indexed: 01/23/2024] Open
Abstract
The "zero point" method allows for lower intensities for an exercise session without impairing the total training volume. This study aimed to compare the effects of the "zero point" versus the traditional method on muscle responses and muscle damage in trained men. Fifteen experienced men (age: 27.7 ± 6.4 years; body mass: 78.4 ± 11.4 kg; height: 174.8 ± 4.9 cm; experience: 5.86 ± 4.7 years; relative bench press strength: 1.38 ± 0.17 kg·kg-1) were subjected to two exercise protocols in a randomized order and separated by a week. The traditional and "zero point" methods were applied in the bench press, with loads of 70% and 50% of one repetition maximum (1RM), respectively, for 10 sets until concentric failure, with 3-min intervals between sets. The zero point method displayed a higher number of repetitions and time under tension than the traditional method, with no difference in the total training volume, echo intensity, algometry, lactate, and myoglobin. For the muscle thickness, no differences between the groups were presented, except for the deltoid muscle thickness, in which a higher post-training volume was observed compared to traditional training. The "zero point" method increases the demand on the deltoid muscles in the bench press exercise, but not on the pectoralis and triceps brachii.
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Affiliation(s)
- Thiago B. Trindade
- Department of Physical Education, Catholic University of Brasilia, QS 07, Lote 01, Taguatinga, Brasilia 71966-700, DF, Brazil; (N.M.F.d.S.); (B.M.d.C.); (T.S.R.); (J.P.)
| | - Ragami C. Alves
- Department of Physical Education, Federal University of Paraná, Curitiba 80050-540, PR, Brazil;
| | - Nuno Manuel Frade de Sousa
- Department of Physical Education, Catholic University of Brasilia, QS 07, Lote 01, Taguatinga, Brasilia 71966-700, DF, Brazil; (N.M.F.d.S.); (B.M.d.C.); (T.S.R.); (J.P.)
| | - Charles Lopes
- Department of Physical Education, Methodist University of Piracicaba, Piracicaba 13420-835, SP, Brazil;
- Faculty Adventist of Hortolândia, Hortolândia 13184-010, SP, Brazil
| | - Bruno Magalhães de Castro
- Department of Physical Education, Catholic University of Brasilia, QS 07, Lote 01, Taguatinga, Brasilia 71966-700, DF, Brazil; (N.M.F.d.S.); (B.M.d.C.); (T.S.R.); (J.P.)
| | - Thiago S. Rosa
- Department of Physical Education, Catholic University of Brasilia, QS 07, Lote 01, Taguatinga, Brasilia 71966-700, DF, Brazil; (N.M.F.d.S.); (B.M.d.C.); (T.S.R.); (J.P.)
| | - Jonato Prestes
- Department of Physical Education, Catholic University of Brasilia, QS 07, Lote 01, Taguatinga, Brasilia 71966-700, DF, Brazil; (N.M.F.d.S.); (B.M.d.C.); (T.S.R.); (J.P.)
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Krishnan C. Effect of paired-pulse stimulus parameters on the two phases of short interval intracortical inhibition in the quadriceps muscle group. Restor Neurol Neurosci 2020; 37:363-374. [PMID: 31306142 DOI: 10.3233/rnn-180894] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
BACKGROUND Short interval intracortical inhibition (SICI) is commonly used to assess inhibition in the motor cortex and is known to be affected by the paired-pulse stimulus parameters (i.e., interstimulus interval [ISI], conditioning stimulus intensity [CSI] and test stimulus intensity [TSI]) used during testing. While the effects of stimulus parameters are well-studied in the upper-extremity, evidence in the lower-extremity is lacking. OBJECTIVE To comprehensively examine the effects of alterations in paired-pulse stimulus parameters on the two phases of SICI in the quadriceps muscle group. METHODS Seventeen adults (8 males, 9 females) volunteered to participate in this study. SICI was examined over a range of CSIs (70-90% active motor threshold [AMT]), TSIs (100-140% AMT), and ISIs (1.0-3.0 ms) using both EMG and torque responses elicited by transcranial magnetic stimulation (TMS). RESULTS The results indicated that SICI at 1.0 ms ISI was best revealed with a CSI of 70% and TSI ≥110% AMT, whereas SICI at 2.5 ms ISI was best revealed with a CSI of 80-90% and a TSI of ≥130% AMT. Unlike upper-extremity muscles, evaluating SICI with a CSI of 70% AMT and an ISI of 1.0 ms produced the greatest inhibition for all TSIs. In general, inhibitory effects were contaminated by facilitatory effects when using a TSI of 100% AMT. CONCLUSIONS The amount of inhibition was dependent on the stimulation parameters used during testing. A CSI of 70% AMT, ISI of 1.0 ms, and TSI of ≥110% AMT appear to be optimal for measuring SICI in the quadriceps muscle; however, other parameters can be used if careful consideration is given to the described interaction between the parameters.
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Affiliation(s)
- Chandramouli Krishnan
- NeuRRo Lab, Department of Physical Medicine and Rehabilitation, Michigan Medicine, Ann Arbor, MI, USA.,Michigan Robotics Institute, University of Michigan, Ann Arbor, MI, USA.,School of Kinesiology, University of Michigan, Ann Arbor, MI, USA.,Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
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Coordination amongst quadriceps muscles suggests neural regulation of internal joint stresses, not simplification of task performance. Proc Natl Acad Sci U S A 2020; 117:8135-8142. [PMID: 32205442 DOI: 10.1073/pnas.1916578117] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Many studies have demonstrated covariation between muscle activations during behavior, suggesting that muscles are not controlled independently. According to one common proposal, this covariation reflects simplification of task performance by the nervous system so that muscles with similar contributions to task variables are controlled together. Alternatively, this covariation might reflect regulation of low-level aspects of movements that are common across tasks, such as stresses within joints. We examined these issues by analyzing covariation patterns in quadriceps muscle activity during locomotion in rats. The three monoarticular quadriceps muscles (vastus medialis [VM], vastus lateralis [VL], and vastus intermedius [VI]) produce knee extension and so have identical contributions to task performance; the biarticular rectus femoris (RF) produces an additional hip flexion. Consistent with the proposal that muscle covariation is related to similarity of muscle actions on task variables, we found that the covariation between VM and VL was stronger than their covariations with RF. However, covariation between VM and VL was also stronger than their covariations with VI. Since all vastii have identical actions on task variables, this finding suggests that covariation between muscle activity is not solely driven by simplification of overt task performance. Instead, the preferentially strong covariation between VM and VL is consistent with the control of internal joint stresses: Since VM and VL produce opposing mediolateral forces on the patella, the high positive correlation between their activation minimizes the net mediolateral patellar force. These results provide important insights into the interpretation of muscle covariations and their role in movement control.
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de Oliveira VB, de Oliveira LF, Menegaldo LL. Estimation of vastus intermedius electromyography: Comparison of three methods and their impact on the knee isometric extension moment predicted by an EMG-Driven model. ISOKINET EXERC SCI 2018. [DOI: 10.3233/ies-182167] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Affiliation(s)
- Viviane B. de Oliveira
- Biomedical Engineering Program, COPPE, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Liliam F. de Oliveira
- Biomedical Engineering Program, COPPE, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
- School of Physical Education and Sports, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Luciano L. Menegaldo
- Biomedical Engineering Program, COPPE, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
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Akagi R, Fukui T, Kubota M, Nakamura M, Ema R. Muscle Shear Moduli Changes and Frequency of Alternate Muscle Activity of Plantar Flexor Synergists Induced by Prolonged Low-Level Contraction. Front Physiol 2017; 8:708. [PMID: 28979212 PMCID: PMC5611407 DOI: 10.3389/fphys.2017.00708] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Accepted: 09/01/2017] [Indexed: 11/20/2022] Open
Abstract
During prolonged low-level contractions, synergist muscles are activated in an alternating pattern of activity and silence called as alternate muscle activity. Resting muscle stiffness is considered to increase due to muscle fatigue. Thus, we investigated whether the difference in the extent of fatigue of each plantar flexor synergist corresponded to the difference in the frequency of alternate muscle activity between the synergists using muscle shear modulus as an index of muscle stiffness. Nineteen young men voluntarily participated in this study. The shear moduli of the resting medial and lateral gastrocnemius muscles (MG and LG) and soleus muscle (SOL) were measured using shear wave ultrasound elastography before and after a 1-h sustained contraction at 10% peak torque during maximal voluntary contraction of isometric plantar flexion. One subject did not accomplish the task and the alternate muscle activity for MG was not found in 2 subjects; therefore, data for 16 subjects were used for further analyses. The magnitude of muscle activation during the fatiguing task was similar in MG and SOL. The percent change in shear modulus before and after the fatiguing task (MG: 16.7 ± 12.0%, SOL: −4.1 ± 13.9%; mean ± standard deviation) and the alternate muscle activity during the fatiguing task (MG: 33 [20–51] times, SOL: 30 [17–36] times; median [25th–75th percentile]) were significantly higher in MG than in SOL. The contraction-induced change in shear modulus (7.4 ± 20.3%) and the alternate muscle activity (37 [20–45] times) of LG with the lowest magnitude of muscle activation during the fatiguing task among the plantar flexors were not significantly different from those of the other muscles. These results suggest that the degree of increase in muscle shear modulus induced by prolonged contraction corresponds to the frequency of alternate muscle activity between MG and SOL during prolonged contraction. Thus, it is likely that, compared with SOL, the alternate muscle activity of MG occurs more frequently during prolonged contraction due to the greater increase in fatigue of MG induced by the progression of a fatiguing task.
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Affiliation(s)
- Ryota Akagi
- College of Systems Engineering and Science, Shibaura Institute of TechnologySaitama, Japan.,Graduate School of Engineering and Science, Shibaura Institute of TechnologySaitama, Japan
| | - Takahito Fukui
- College of Systems Engineering and Science, Shibaura Institute of TechnologySaitama, Japan
| | - Masato Kubota
- Graduate School of Engineering and Science, Shibaura Institute of TechnologySaitama, Japan
| | - Masashi Nakamura
- Graduate School of Engineering and Science, Shibaura Institute of TechnologySaitama, Japan
| | - Ryoichi Ema
- Graduate School of Engineering and Science, Shibaura Institute of TechnologySaitama, Japan.,Japan Society for the Promotion of Science (JSPS)Tokyo, Japan
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García-Vaquero MP, Ruiz-Pérez I, Barbado D, Vera-Garcia FJ. Electromyographic and Kinematic Analysis of the Flexion-Rotation Trunk Test. J Strength Cond Res 2017; 34:3386-3394. [PMID: 28796125 DOI: 10.1519/jsc.0000000000002168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
García-Vaquero, MP, Ruiz-Pérez, I, Barbado, D, and Vera-Garcia, FJ. Electromyographic and kinematic analysis of the flexion-rotation trunk test. J Strength Cond Res 34(12): 3386-3394, 2020-Although most trunk endurance field protocols are performed in the sagittal or frontal planes, the flexion-rotation trunk (FRT) test combines trunk flexion with rotation, which may be relevant to rotation-related sports. The aim of this study was to describe the trunk and hip muscle activation and fatigue and the range of hip flexion of this test. Twenty-seven physically active males and females performed the FRT test after a period of practice. Electromyographic (EMG) signals were bilaterally collected from the rectus abdominis (RA), internal oblique (IO), and rectus femoris (RF), and hip flexion amplitude was measured using a biaxial electrogoniometer. Because the fast Fourier transform algorithm requires stationary EMG signals, subjects performed a 6-second isometric trunk flexion-rotation repetition just before and just after the test execution (preexecution and postexecution repetitions, respectively). Rectus abdominis showed the highest mean activation levels (approximately 30% maximal voluntary isometric contractions [MVC]) in the preexecution repetition, followed by IO (approximately 20% MVC). Also, the mean power frequency (MPF) significantly decreased from the pre-execution to the postexecution repetition for RA and IO, which shows abdominal muscle fatigue. Although each trunk flexion-rotation repetition involved an average 8-14° hip flexion, the RF activation was lower than 10% MVC, and no significant MPF reduction (i.e., no muscle fatigue) was observed for this muscle. In addition, significant negative correlations were found between the FRT test scores and the normalized EMG amplitudes of RF. Based on these results, the FRT test seems a valid field protocol to assess abdominal muscle endurance in trunk flexion-rotation exertions.
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Saito A, Ando R, Akima H. Effects of prolonged vibration to vastus intermedius muscle on force steadiness of knee extensor muscles during isometric force-matching task. J Electromyogr Kinesiol 2016; 31:48-54. [PMID: 27668572 DOI: 10.1016/j.jelekin.2016.09.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 09/06/2016] [Accepted: 09/16/2016] [Indexed: 11/15/2022] Open
Abstract
Afferent inputs from Ia fibers in muscle spindles are essential for the control of force and prolonged vibration has been applied to muscle-tendon units to manipulate the synaptic input from Ia afferents onto α-motor neurons. The vastus intermedius (VI) reportedly provides the highest contribution to the low-level knee extension torque among the individual synergists of quadriceps femoris (QF). The purpose of the present study was to examine the effect of prolonged vibration to the VI on force steadiness of the QF. Nine healthy men (25.1±4.3years) performed submaximal force-matching task of isometric knee extension for 15s before and after mechanical vibration to the superficial region of VI for 30min. Target forces were 2.5%, 10%, and 30% of maximal voluntary contraction (MVC), and force steadiness was determined by the coefficient of variation (CV) of force. After the prolonged VI vibration, the CV of force at 2.5%MVC was significantly increased, but CVs at 10% and 30%MVCs were not significantly changed. The present study concluded that application of prolonged vibration to the VI increased force fluctuations of the QF during a very low-level force-matching task.
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Affiliation(s)
- Akira Saito
- Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, Japan.
| | - Ryosuke Ando
- Graduate School of Education and Human Development, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan; Japan Society for the Promotion of Science, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo, Japan
| | - Hiroshi Akima
- Graduate School of Education and Human Development, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan; Research Center of Health, Physical Fitness & Sports, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan
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Akima H, Ando R. Oxygenation and neuromuscular activation of the quadriceps femoris including the vastus intermedius during a fatiguing contraction. Clin Physiol Funct Imaging 2016; 37:750-758. [DOI: 10.1111/cpf.12370] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 03/30/2016] [Indexed: 11/27/2022]
Affiliation(s)
- Hiroshi Akima
- Research Center of Health; Physical Fitness & Sports; Nagoya University; Nagoya Japan
- Graduate School of Education & Human Development; Nagoya University; Nagoya Japan
| | - Ryosuke Ando
- Graduate School of Education & Human Development; Nagoya University; Nagoya Japan
- Japan Society for the Promotion of Science; Chiyoda, Tokyo Japan
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9
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Saito A, Akima H. Neuromuscular Activation of the Vastus Intermedius Muscle during Isometric Hip Flexion. PLoS One 2015; 10:e0141146. [PMID: 26488742 PMCID: PMC4619471 DOI: 10.1371/journal.pone.0141146] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Accepted: 10/04/2015] [Indexed: 11/26/2022] Open
Abstract
Although activity of the rectus femoris (RF) differs from that of the other synergists in quadriceps femoris muscle group during physical activities in humans, it has been suggested that the activation pattern of the vastus intermedius (VI) is similar to that of the RF. The purpose of present study was to examine activation of the VI during isometric hip flexion. Ten healthy men performed isometric hip flexion contractions at 25%, 50%, 75%, and 100% of maximal voluntary contraction at hip joint angles of 90°, 110° and 130°. Surface electromyography (EMG) was used to record activity of the four quadriceps femoris muscles and EMG signals were root mean square processed and normalized to EMG amplitude during an isometric knee extension with maximal voluntary contraction. The normalized EMG was significantly higher for the VI than for the vastus medialis during hip flexion at 100% of maximal voluntary contraction at hip joint angles of 110° and 130° (P < 0.05). The onset of VI activation was 230–240 ms later than the onset of RF activation during hip flexion at each hip joint angle, which was significantly later than during knee extension at 100% of maximal voluntary contraction (P < 0.05). These results suggest that the VI is activated later than the RF during hip flexion. Activity of the VI during hip flexion might contribute to stabilize the knee joint as an antagonist and might help to smooth knee joint motion, such as in the transition from hip flexion to knee extension during walking, running and pedaling.
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Affiliation(s)
- Akira Saito
- Graduate School of Education and Human Development, Nagoya University, Nagoya, Aichi, Japan
- Japan Society for the Promotion of Science, Chiyoda, Tokyo, Japan
- * E-mail:
| | - Hiroshi Akima
- Graduate School of Education and Human Development, Nagoya University, Nagoya, Aichi, Japan
- Research Center of Health, Physical Fitness & Sports, Nagoya University, Nagoya, Aichi, Japan
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Saito A, Ando R, Akima H. Effects of prolonged patellar tendon vibration on force steadiness in quadriceps femoris during force-matching task. Exp Brain Res 2015; 234:209-17. [DOI: 10.1007/s00221-015-4447-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 09/16/2015] [Indexed: 11/25/2022]
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Saito A, Akima H. Knee joint angle affects EMG–force relationship in the vastus intermedius muscle. J Electromyogr Kinesiol 2013; 23:1406-12. [DOI: 10.1016/j.jelekin.2013.08.009] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 07/31/2013] [Accepted: 08/28/2013] [Indexed: 12/01/2022] Open
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Akima H, Saito A. Activation of quadriceps femoris including vastus intermedius during fatiguing dynamic knee extensions. Eur J Appl Physiol 2013; 113:2829-40. [DOI: 10.1007/s00421-013-2721-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Accepted: 08/27/2013] [Indexed: 10/26/2022]
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Kishibuchi K, Kouzaki M. Medial gastrocnemius is a key muscle for involuntary alternate muscle activity of plantar flexor synergists. Neurosci Lett 2013; 550:145-9. [PMID: 23831351 DOI: 10.1016/j.neulet.2013.06.052] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Revised: 06/10/2013] [Accepted: 06/24/2013] [Indexed: 11/19/2022]
Abstract
Redundant and/or complicated muscle activations between synergist muscles have been demonstrated during low-level sustained contractions. Identification of a key muscle for this phenomenon allows for the simplification of motor control during prolonged contraction. In this study, we have identified a key muscle for involuntary alternate muscle activity of plantar flexor muscles based on a physiological tremor sequence that was recorded over 120 min. Two epochs where the muscle activity of medial gastrocnemius abruptly increased with decrease in other synergists (case ON) and vise verse (case OFF) were analyzed. Our results indicated that involuntary alternate muscle activity was associated with changes in physiological tremor of ankle angular acceleration when the muscle activity of medial gastrocnemius decreased in case OFF. In particular, the activity of the medial gastrocnemius muscle, but not the activity of other synergists, was accompanied by physiological tremor, demonstrating that the medial gastrocnemius is a key muscle for involuntary alternate muscle activity in plantar flexor synergists. In addition, weaker correlations between muscle activities and physiological tremor were found in case ON than case OFF. We suggest that, if the central nervous system can employ this unique muscle strategy, redundant and/or complicated neuromuscular activities will be reduced because of the existence of the key muscle.
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Affiliation(s)
- Kaoru Kishibuchi
- Laboratory of Neurophysiology, Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan
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Akima H, Saito A. Inverse activation between the deeper vastus intermedius and superficial muscles in the quadriceps during dynamic knee extensions. Muscle Nerve 2013; 47:682-90. [DOI: 10.1002/mus.23647] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/21/2012] [Indexed: 11/07/2022]
Affiliation(s)
| | - Akira Saito
- Graduate School of Education and Human Development; Nagoya University; Nagoya; Japan
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Saito A, Watanabe K, Akima H. The highest antagonistic coactivation of the vastus intermedius muscle among quadriceps femoris muscles during isometric knee flexion. J Electromyogr Kinesiol 2013; 23:831-7. [PMID: 23489717 DOI: 10.1016/j.jelekin.2013.02.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Revised: 02/04/2013] [Accepted: 02/13/2013] [Indexed: 11/26/2022] Open
Abstract
Although the possibility that the vastus intermedius (VI) muscle contributes to flexion of the knee joint has been suggested previously, the detail of its functional role in knee flexion is not well understood. The purpose of this study was to examine the antagonist coactivation of VI during isometric knee flexion. Thirteen men performed 25-100% of maximal voluntary contraction (MVC) at 90°, 120°, and 150° knee joint angles. Surface electromyography (EMG) of the four individual muscles in the quadriceps femoris (QF) was recorded and normalized by the EMG signals during isometric knee extension at MVC. Cross-talk on VI EMG signal was assessed based on the median frequency response to selective cooling of hamstring muscles. Normalized EMG of the VI was significantly higher than that of the other synergistic QF muscles at each knee joint angle (all P<0.05) with minimum cross-talk from the hamstrings to VI. There were significant correlations between the EMG signal of the hamstrings and VI (r=0.55-0.85, P<0.001). These results suggest that VI acts as a primary antagonistic muscle of QF during knee flexion, and that VI is presumably a main contributor to knee joint stabilization.
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Affiliation(s)
- Akira Saito
- Graduate School of Education and Human Development, Nagoya University, Japan.
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