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The effect of the pressure level of sports compression pants on dexterity and movement-related cortical potentials
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The effect of the pressure level of sports compression pants on dexterity and movement-related cortical potentials Les effets des niveaux de pression des pantalons de compression sur les processus de préparation d’un mouvement volontaire H. Lee a, K. Kim b, Y. Lee a,b,∗ a b
Department of Clothing and Textiles, Chungnam National University, Deajeon, Republic of Korea Department of Bio and Brain Engineering, KAIST, Deajeon, Republic of Korea
Received 6 September 2016; accepted 13 March 2017
KEYWORDS Compression pants; Clothing pressure; Agility; MRCPs; Response time
∗
Summary Objectives. — The present study sought to determine how basic motor skills, such as agility, and the brain’s reaction to perception handling are affected by the pressure level of compression pants. Equipment and methods. — Twelve subjects wore three different compression pants and undertook sidestep tests to evaluate agility. For the analysis of movement-related cortical potentials, electroencephalography was conducted while participants performed an exercise involving the pressing of a foot-operated switch in response to randomly repeated sound stimuli. Results. — When wearing the CG2 model pants, the pant that applied the highest pressure among the three, enhanced agility (P < 0.042). Further, the amplitude of movement-related cortical potentials increased the most at Fz and Cz (Fz: P = 0.020 and Cz: P = 0.027). While there was no significant statistical difference in response time among the experimental pants, the average time was reduced. It can be conjectured that the pressure the compression pants applies on the skin and muscles affects the nervous system, increasing the agility and activity of motor-related information processing by enhancing the focus on the performance. It was therefore concluded that the pressure level of compression pants is a variable of influence on the motor branch of the nervous system. © 2017 Elsevier Masson SAS. All rights reserved.
Corresponding author. E-mail address: [email protected] (Y. Lee).
http://dx.doi.org/10.1016/j.scispo.2017.03.006 0765-1597/© 2017 Elsevier Masson SAS. All rights reserved.
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MOTS CLÉS Pantalon de compression ; Niveau de pression ; Agilité ; Activité corticale
Résumé Objectifs. — Cette recherche a pour but de montrer comment les compétences motrices basiques, comme l’agilité et la réaction cérébrale dans le processus de la préparation de l’action d’un mouvement volontaire, sont influencées par le niveau de pression des pantalons de compression. Équipement et méthode. — Douze sujets ont porté trois types différents de pantalon de compression et ont procédé à des tests de type « pas chassés » dans le but d’évaluer l’agilité. En ce qui concerne l’analyse des mouvements liés aux potentiels corticaux, les sujets du test étaient sous électroencéphalogramme pendant la réalisation d’un exercice qui consistait en un changement brusque de mouvement de pied en réponse à des stimuli sonores émis au hasard. Résultats. — Le modèle de pantalon CG2, modèle qui a appliqué le plus de pression parmi les trois testés, améliore l’agilité (p < 0,042). De plus, l’amplitude des mouvements liés aux potentiels corticaux a le plus augmenté à Fz et Cz (Fz : p = 0,020 et Cz : p = 0,027). Même s’il n’y avait pas de différence statistique signifiante pendant le temps de réponse, le temps moyen a été réduit. Nous pouvons supposer que la pression des pantalons de compression, appliquée à la peau et aux muscles, a un effet sur le système nerveux ce qui augmente l’agilité et l’activité du processus informatif lié à la motricité et améliore ainsi la performance. Il a donc été conclu que le niveau de pression des vêtements de compression varie selon son influence sur la branche motrice du système nerveux. © 2017 Elsevier Masson SAS. Tous droits r´ eserv´ es.
1. Introduction Compression garments have been increasing in popularity among the general public as well as among professionals because of their ability to enhance muscular power, strength, endurance, proprioception, and injury management [1—5]. Therefore, most previous research in this area concerns the kinetic, physiological, and psychological effects of wearing compression garments, such as enhancing lactate removal, reducing muscle oscillation, increasing torque, and positively influencing psychological factors. These experiments focused on particular activities, for example, exercise on a bicycle ergometer or cycling [2,6], vertical jump [3,4,7], running [5,8,9], repeated-sprint [10], netball [11], cross-country skiing [12], ball-throwing [10]. In consequence, the relationship between compression garments and basic motor skills were previously yet to be established. Properties related to basic motor skills employed during sports activities include muscular power, endurance, agility, and elaboration. Of these, agility and elaboration fall within the purview of the nervous system, which perceives, identifies, recognizes, and decides, reacting according to the environment and situation [13]. Especially, agility is one of the main elements of strength concerned with the nervous system, and means the ability to perform a certain activity in the minimal time given. Therefore, it can be expressed as the latency of response, the time taken to perform a single activity, and the number of repetitions of an activity [14]. Generally, successful performances in many sports, including soccer, tennis, and basketball, require recognition and appropriate reaction. Therefore, facilitating agile changes of motion as that of an instantly reactive human body is an important strategy by which athletic performance may be enhanced. To test agility, individuals can select and refine movements based on task-relevant cues, including an opponent and/or external object [15,16].
In contrast, observation of brain activity during sports activities can be utilized as a source of basic data upon which to base methods for optimizing sports efficiency. Higashiura et al. (2010) recorded in mm/s units the changes brain activity related to motion prediction by using electroencephalogram (EEG) and event-related potentials (ERPs) [17]. Movement-related cortical potentials (MRCPs) are evoked potentials evident immediately prior to motor action performance and are defined as neural potentials associated with self-paced, voluntary movements. MRCPs are of great interest because they are expected to help identify the neural mechanisms underlying preparation, initiation, execution, and feedback control [18—20]. MRCPs are negative evoked potentials of the brain that could be utilized in the evaluation of cognitions underpinning the prediction of future activities through anticipation and recognition during action preparation [21]. However, research related to compression garments and the nervous system are scarce because of the difficulty of processing noise data in motion postures and the absence of appropriate experimental protocol. Therefore, the purpose of this research was to measure the changes in basic motor skills and brain reaction that result from wearing compression pants. Using compression pants with different pressure levels, their effect on agility was determined. Furthermore, the cognitive processes occurring from when the motor reaction expectant stimulus was applied to when the action was performed were analyzed. The effects of compression pants’ pressure levels on advanced central nervous system functions such as perception and recognition were examined in relation to external/internal event reaction times.
2. Research method 2.1. Subjects Twelve university students of, on average, 24 ± 2.2 years of age, 178.9 ± 5.3 cm in height, 75 ± 4.9 kg in weight, and
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Figure 1
Experimental pants (CG, CG1, and CG2) — modified from Lee et al. (2016).
with no specific sports training experience were selected as research subjects. The number of subjects was determined based on previous studies [5,8,9,22,23] indicating that 10—14 subjects could draw meaningful differences among experimental garments. Prior to the experiment, for the subjects’ safety and the protection of their rights, approval from the National Bioethics Committee (201408-SB-04101) was obtained for this study. The subjects participated of their own volition after ample explanation was given regarding the experiment. Subjects were prohibited from intensive exercise, alcohol consumption, and smoking, and were to sustain regular sleeping times prior to the experiment.
2.2. Compression pants The compression pants used represent the three experimental garment variables CG, CG1, and CG2, each a tricot of 92% polyester and 8% polyurethane used previously by Lee et al., 2016 [24]. Each model is designed to apply different levels of pressure; CG applied 0.44—0.58 kPa at the knees, and 0.48—0.68 kPa at the thighs; CG1 applied 0.95—1.03 kPa at the knees, and 0.53—0.71 kPa at the thighs; and CG2 applied 1.67—2.12 kPa at the knees, and 0.80—1.14 kPa at the thighs. The compression pants look as in Fig. 1 when worn on mannequins.
Figure 2
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2.3. Agility and MRCP experiment design The twelve subjects performed sidestep tests and underwent MRCP experiments while wearing the three types of compression pants. To mitigate the order effect, the order in which each subject wore each model of compression pants was differed between subjects using the Latin square method, and the experiment followed the protocol outlined in Fig. 2. The subjects took a 5-minute rest upon arriving at the laboratory before wearing the first compression pants. The first sidestep test was carried out once before a 10minute break, after which the second test was conducted, another 10-minute break was permitted before the third and final test. This protocol was the first set of experiments using the first compression pants, and it was carried out for the other two models in the form of a second and third set of experiments. A break of 5 minutes between the first and second sets was permitted. The subject stood with legs apart in the center of three parallel lines of 1.2 m distance apart from each other. Upon the cue of ‘‘start’’, the first count was measured when the right-hand line was crossed, the second count when the subject returned to the centerline, and upon crossing the left-hand line, the third count was measured. The above motions were performed as fast as possible for 20 seconds. The brainwave measurements were conducted before each subject performed the exercise and action
Protocol of the experiment for evaluating agility and the movement-related cortical potentials experiment.
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performance evaluation. The MRCP experiment was performed 1 week after the agility experiment, as per the defined protocol (Fig. 2). Five minutes’ break was given before the experiment, and EEG and electromyography (EMG) electrodes were attached to the subject. The motions required for MRCP measurement were performed followed by a 5-minute rest. This was the first set of one model of compression pants, and after changing into the second and third models, the second and third sets of the experiment were performed, respectively. As in the agility test, the break time between first set and second set was 5 minutes. The motion performed by the subject during the measurement of MRCPs was as depicted in Fig. 3: the subject wore the compression pants and sat down on a chair, his right leg horizontal to a footrest. Then, the subject raised the right foot, with the leg kept straight to press the foot switch upon hearing the beep sound emitted from the table on the right-hand side. The subject was instructed to press the foot switch as quickly and accurately as possible. The beep sound was designed to sound 32 times at arbitrary intervals of 1 to 5 seconds.
2.4. MRCP data collection and analysis The EEG, EMG, and response trigger signals required for the analysis of MRCPs were measured using the 8-channel polygraph system BIOS-S8 (BioBrain Inc., Daejeon, Korea). The attachment points for EEG electrodes were selected according to Jasper’s (1958) 10—20 System of Electrode Placement, specifically sites Fpz, Fz, Cz, Pz, C3, and C4 [25]. The reference electrode and ground electrode were attached at A1
Figure 4
Figure 3 Illustration of the experimental setup used for the movement-related cortical potentials experiment.
and A2, the rear of each earlobe. For EMG measurements, bipolar patch-type electrodes were attached at the rectus femoris muscle belly. EEG was assigned six channels, EMG was assigned two, and the response trigger signal was assigned one. The measured analog signals were standardized to 250 Hz, converted into digital signals, and sent to the computer. The digital EEG, EMG, and response trigger signals were filtered using bio-signal time series analysis program BioScan
Normalized movement-related cortical potentials and trigger trace.
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Sports compression pants and dextery (BioBrain Inc., Korea) and rendered into brainwave rhythm data according to frequency. Afterwards, a spectrum value reflecting the quantitative brainwave rhythm was computed. Then, as in Terada et al.’s (1995) research, to obtain the MRCPs index, data were trimmed according to response trigger perspective [22]. Ensemble averaging was then performed on these data, resulting in the MRCPs’ waveform, from which the peak amplitude was derived. Analysis of all the data was performed through a big data analysis cloud computing software, BioScan-Cloud (BioBrain Inc., Korea), producing the required information in accordance with the time of the event. As demonstrated in Fig. 4, MRCPs generated prior to activation of the muscles for motor performance were analyzed. The amplitude of each waveform from when the sound stimulus was presented to when the negative peak was reached was extracted. In addition, to compute the subjects’ response time, the time difference from when the sound stimulus was presented to induce motion to when the subject reacted was calculated.
2.5. Statistical analysis The mean and standard deviation of all measured variables were computed using SPSS 20.0 (IBM, New York, USA). The sidestep measurements were analyzed using repeated measures ANOVA. In the case of the statistical processing of MRCP elements, differences in the amplitudes and response times of each MRCP component among the garments were statistically analyzed by the Freidman test for each electrode placement (Fpz, Fz, Cz, C3, C4, and Pz). Statistical significance was defined as P < 0.05.
3. Results 3.1. Agility Fig. 5 compares the average of the number of sidesteps achieved while wearing each compression pants. In all cases, agility increased in the second trial compared to the first (P < 0.042), and a statistically significant difference was identified between compression pants (P < 0.027). When wearing CG2, the pants with the highest pressure level, agility increased significantly from 21.19 ± 1.6 kPa in the first trial to 21.56 ± 1.9 kPa in the second trial. Wearing CG2, which applied relatively high pressure to the legs, affects
Figure 6 5.
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Figure 5 Comparison of agility, as determined by the sidestep experiment, measured for each compression garment.
the nervous system, which in turn awakens and enhances focus on the sidestep test, thereby increasing agility. However, no interaction was found between the compression pants and difference in the number of sidesteps among trials.
3.2. Amplitude of MRCPs Fig. 6 shows averaged MRCPs that underwent movingweighted-average-smoothing. Time zero is when the beep stimulus was presented, and it can be seen that thereafter the recordings of every EEG electrode were negative. Through quantitative analysis of MRCP amplitude, some differences were identified between compression garments. Comparing the amplitude of MRCPs at every electrode placement in Fig. 7, MRCP amplitude associated with CG2 increased the most of all the pants tested. Friedman’s test showed that amplitude increased in the descending order of CG2, CG1, CG, with significant differences at Fz and Cz (P = 0.020 and P = 0.027, respectively). It may therefore be deduced that a compression pants that applies a high pressure level facilitates the performance of the task of deftly reacting to an auditory stimulus. It can also be said that the high pressure pants assist in activating the cognitions of perception and recognition central to performing physical tasks.
Averaged waveforms of movement-related cortical potentials recorded at each of the electrode placements of subject
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Figure 7
Average amplitude of movement-related cortical potentials for each garment. Error bars represent S.D.
Figure 8 Average response times of the motion performance task for each tested garment.
3.3. Response time Average response times for each of the tested garments are shown in Fig. 8. When wearing CG2, the compression garment with the highest pressure level, the response latency was the lowest (0.61 seconds), but this difference was not statistically significant (P = 0.121). However, response time decreased as the pressure level increased, and therefore, it can be said that quick response time was related to wearing CG2. CG2 was associated with enhanced speed, a major element of sport and a property of the nervous system. However, in the present study, this difference did not reach statistical significance.
4. Discussion This research investigated the effect of compression pants’ pressure level on the brain’s information handling process
in relation to agility, a basic motor skill key to sport. Current commercial sports compression garments are designed to apply partial or differential pressure according to their intended purpose and are marketed with an emphasis on the fact that they offer certain benefits to one’s sporting performance. These methods of designing compression garments with differential pressure, partial pressure, and pressure level support certain muscles, allowing the wearer to focus on performing the task at hand. As a result, it can be said that agility is enhanced by excluding needless effort during sports activities and delivering precise nervous orders to the necessary muscles. Doan et al. (2003) stated that the elasticity of compression garments reduces activation of antagonistic muscles through pressure upon running and produces torques supporting the hamstrings [3]. Zhou (2013) stated that functions of compression garments, such as enhanced mobility, muscle support, and protection from joint damage vary according to their level of elasticity [26]. Lee et al. (2016) also classified compression pants with different pressure levels into those that function to protect the body against impact from landing and those that function to access the full potential of muscle capabilities through kinematic and kinetic evaluation [24]. Bringard et al. (2006) showed that a compression garment exerting a pressure of 3.06 kPa over the gastrocnemius muscle increases muscular oxygenation [9]. In addition, Scanlan et al. (2008) found that compression garments that apply high pressure on the limbs (gastrocnemius, 2.31 kPa; vastus lateralis, 1.99 kPa) significantly improve muscle oxygenation economy during a 1-h cycling time trial [27]. In practice, when Choi et al. (2014) measured the brainwaves of participants as they walked wearing compression garments of different pressure levels, the participants reported significantly less relaxation when wearing higher pressure garments, a variable that also showed a positive correlation with cognitive load index, relative beta wave emitted upon awakening, and concentration index [28]. The results of this research also show significant increases in agility when wearing the compression garment with the highest pressure level, CG2. This may
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Sports compression pants and dextery be explained similarly to the previously discussed study, in contrast, as agility is a fundamental component of quick decision making, nervous and muscular coordination, and muscle contraction speed of the central nervous system. The present research analyzed MRCPs to further understand the relationship between the brain’s information handling process and the brain’s reaction. This study found that wearing CG2 while performing the voluntary movement of leg raises increased the amplitude of MRCPs at Cz and Fz and reduced the response time. Increased MRCP amplitude has been interpreted in several different ways in the literature. In research by Taylor (1978) measuring the preparation transition between sections that have acquired certain actions and have been experimented by, it is claimed that when motion tasks are acquired and are repeatedly carried out, MRCP amplitude increases in tandem with performance enhancement [29]. It is therefore also reported that this amplitude increase reflects the subjects’ motor task performance proficiency. In addition, MRCP amplitude is proportional to preparation level, since amplitude and latency require further preparation procedures when one performs smooth motion tasks compared to fast motion tasks [30,31]. However, some researchers argue that as sports education and technique acquisition are performed, the success rate of MRCPs increases, but the amplitude decreases. Wright (2012) argues in his report on 5 weeks of research regarding the brain’s change in the motion preparation process involved in playing the guitar that the motor readiness potential decreases as the negative slope decreases [32]. This study also found that guitar-playing proficiency improved with practice. Moreover, professional athletes and pianists are more skilled at performing the tasks of their respective professions, but not at tasks in general, thereby shortening the neural circuit and allowing effective cortex activities, ultimately reducing the amplitude of the MRCPs [33—35]. In these studies, motor cortex activity decreased as kinesthetic memory was reinforced and automatized, and as skill was enhanced, but it is argued that this was because effective task performance was carried out. However, unlike the studies above, where sports education was an independent variable, this study was carried out with compression garments as a variable, thus requiring a different interpretive approach. In short, this study adopted a new perspective on MRCPs by setting compression garments as an independent variable. Specific experimental protocols were designed to observe agility and amplitude of MRCPs and response time affected by the independent variable. In order to examine effects of compression garments exclusively, experimental subjects were limited to non-athletes. The order of wearing experimental garments was planned using a Latin square to control and eliminate any effect caused by it. Different sound stimuli were computer programmed to be played for each experiment. Therefore, it was expected that the only independent variable that had significant influence on the research results would be pressure levels of the experimental garments. Our study could show that the effect of repeated learning was trivial because there was only a small standard error in each experiment when each average and standard deviation was statistically processed. We found that agility and response time are enhanced when wearing CG2, and the amplitude of MRCPs is increased,
7 signifying focused activation of motor information handling processes such as perception and recognition, therefore implying successful performance of the motion tasks. As explained beforehand, the pressure applied on the legs through compression pants increased alertness and focus on motor task performance, thereby enhancing motor information processing in the brain. As known from previous studies on compression garments, skin pressure exerted by compression garments has physiologically, dynamically and psychologically beneficial effects on the wearer. It could be interpreted from our study that pressure level of compression garments causes significant differences to MRCPs, which enable the beneficial effects mentioned above for the wearer.
5. Conclusions In this study, wearing CG2, the compression pants with the highest pressure level, enhanced agility and response time as well as increased the amplitude of MRCPs. This implies that the pressure level of compression pants is a major variable in clothing design that impacts the brain’s perception handling processes and motor skills. Furthermore, the function of compression garments differed according to their elasticity and pressure level. Most commercialized compression garments available up to the present day have focused on marketing and advertising based on their various functions. However, this research implies that compression pants with relatively low pressure levels may not be able to perform these functions maximally. Moreover, pressure level may change according to not only the size of the clothing, but also body measurements, thus calling for caution in the generalization of their functions. The present study also analyzed the effect of compression pants on the nervous system through brainwave measurements, a feature that sets this study apart from previous research. However, owing to the limited selection of garment models and motor tasks tested in this study, a more comprehensive investigation in this research domain is warranted. Moreover, there will be a significant benefit in performing a similar research study as a follow-up.
Disclosure of interest The authors declare that they have no competing interest.
Acknowledgements This study was supported by research fund of Chungnam National University in 2015.
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ORIGINAL ARTICLE
The effect of the pressure level of sports compression pants on dexterity and movement-related cortical potentials Les effets des niveaux de pression des pantalons de compression sur les processus de préparation d’un mouvement volontaire H. Lee a, K. Kim b, Y. Lee a,b,∗ a b
Department of Clothing and Textiles, Chungnam National University, Deajeon, Republic of Korea Department of Bio and Brain Engineering, KAIST, Deajeon, Republic of Korea
Received 6 September 2016; accepted 13 March 2017
KEYWORDS Compression pants; Clothing pressure; Agility; MRCPs; Response time
∗
Summary Objectives. — The present study sought to determine how basic motor skills, such as agility, and the brain’s reaction to perception handling are affected by the pressure level of compression pants. Equipment and methods. — Twelve subjects wore three different compression pants and undertook sidestep tests to evaluate agility. For the analysis of movement-related cortical potentials, electroencephalography was conducted while participants performed an exercise involving the pressing of a foot-operated switch in response to randomly repeated sound stimuli. Results. — When wearing the CG2 model pants, the pant that applied the highest pressure among the three, enhanced agility (P < 0.042). Further, the amplitude of movement-related cortical potentials increased the most at Fz and Cz (Fz: P = 0.020 and Cz: P = 0.027). While there was no significant statistical difference in response time among the experimental pants, the average time was reduced. It can be conjectured that the pressure the compression pants applies on the skin and muscles affects the nervous system, increasing the agility and activity of motor-related information processing by enhancing the focus on the performance. It was therefore concluded that the pressure level of compression pants is a variable of influence on the motor branch of the nervous system. © 2017 Elsevier Masson SAS. All rights reserved.
Corresponding author. E-mail address: [email protected] (Y. Lee).
http://dx.doi.org/10.1016/j.scispo.2017.03.006 0765-1597/© 2017 Elsevier Masson SAS. All rights reserved.
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MOTS CLÉS Pantalon de compression ; Niveau de pression ; Agilité ; Activité corticale
Résumé Objectifs. — Cette recherche a pour but de montrer comment les compétences motrices basiques, comme l’agilité et la réaction cérébrale dans le processus de la préparation de l’action d’un mouvement volontaire, sont influencées par le niveau de pression des pantalons de compression. Équipement et méthode. — Douze sujets ont porté trois types différents de pantalon de compression et ont procédé à des tests de type « pas chassés » dans le but d’évaluer l’agilité. En ce qui concerne l’analyse des mouvements liés aux potentiels corticaux, les sujets du test étaient sous électroencéphalogramme pendant la réalisation d’un exercice qui consistait en un changement brusque de mouvement de pied en réponse à des stimuli sonores émis au hasard. Résultats. — Le modèle de pantalon CG2, modèle qui a appliqué le plus de pression parmi les trois testés, améliore l’agilité (p < 0,042). De plus, l’amplitude des mouvements liés aux potentiels corticaux a le plus augmenté à Fz et Cz (Fz : p = 0,020 et Cz : p = 0,027). Même s’il n’y avait pas de différence statistique signifiante pendant le temps de réponse, le temps moyen a été réduit. Nous pouvons supposer que la pression des pantalons de compression, appliquée à la peau et aux muscles, a un effet sur le système nerveux ce qui augmente l’agilité et l’activité du processus informatif lié à la motricité et améliore ainsi la performance. Il a donc été conclu que le niveau de pression des vêtements de compression varie selon son influence sur la branche motrice du système nerveux. © 2017 Elsevier Masson SAS. Tous droits r´ eserv´ es.
1. Introduction Compression garments have been increasing in popularity among the general public as well as among professionals because of their ability to enhance muscular power, strength, endurance, proprioception, and injury management [1—5]. Therefore, most previous research in this area concerns the kinetic, physiological, and psychological effects of wearing compression garments, such as enhancing lactate removal, reducing muscle oscillation, increasing torque, and positively influencing psychological factors. These experiments focused on particular activities, for example, exercise on a bicycle ergometer or cycling [2,6], vertical jump [3,4,7], running [5,8,9], repeated-sprint [10], netball [11], cross-country skiing [12], ball-throwing [10]. In consequence, the relationship between compression garments and basic motor skills were previously yet to be established. Properties related to basic motor skills employed during sports activities include muscular power, endurance, agility, and elaboration. Of these, agility and elaboration fall within the purview of the nervous system, which perceives, identifies, recognizes, and decides, reacting according to the environment and situation [13]. Especially, agility is one of the main elements of strength concerned with the nervous system, and means the ability to perform a certain activity in the minimal time given. Therefore, it can be expressed as the latency of response, the time taken to perform a single activity, and the number of repetitions of an activity [14]. Generally, successful performances in many sports, including soccer, tennis, and basketball, require recognition and appropriate reaction. Therefore, facilitating agile changes of motion as that of an instantly reactive human body is an important strategy by which athletic performance may be enhanced. To test agility, individuals can select and refine movements based on task-relevant cues, including an opponent and/or external object [15,16].
In contrast, observation of brain activity during sports activities can be utilized as a source of basic data upon which to base methods for optimizing sports efficiency. Higashiura et al. (2010) recorded in mm/s units the changes brain activity related to motion prediction by using electroencephalogram (EEG) and event-related potentials (ERPs) [17]. Movement-related cortical potentials (MRCPs) are evoked potentials evident immediately prior to motor action performance and are defined as neural potentials associated with self-paced, voluntary movements. MRCPs are of great interest because they are expected to help identify the neural mechanisms underlying preparation, initiation, execution, and feedback control [18—20]. MRCPs are negative evoked potentials of the brain that could be utilized in the evaluation of cognitions underpinning the prediction of future activities through anticipation and recognition during action preparation [21]. However, research related to compression garments and the nervous system are scarce because of the difficulty of processing noise data in motion postures and the absence of appropriate experimental protocol. Therefore, the purpose of this research was to measure the changes in basic motor skills and brain reaction that result from wearing compression pants. Using compression pants with different pressure levels, their effect on agility was determined. Furthermore, the cognitive processes occurring from when the motor reaction expectant stimulus was applied to when the action was performed were analyzed. The effects of compression pants’ pressure levels on advanced central nervous system functions such as perception and recognition were examined in relation to external/internal event reaction times.
2. Research method 2.1. Subjects Twelve university students of, on average, 24 ± 2.2 years of age, 178.9 ± 5.3 cm in height, 75 ± 4.9 kg in weight, and
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Sports compression pants and dextery
Figure 1
Experimental pants (CG, CG1, and CG2) — modified from Lee et al. (2016).
with no specific sports training experience were selected as research subjects. The number of subjects was determined based on previous studies [5,8,9,22,23] indicating that 10—14 subjects could draw meaningful differences among experimental garments. Prior to the experiment, for the subjects’ safety and the protection of their rights, approval from the National Bioethics Committee (201408-SB-04101) was obtained for this study. The subjects participated of their own volition after ample explanation was given regarding the experiment. Subjects were prohibited from intensive exercise, alcohol consumption, and smoking, and were to sustain regular sleeping times prior to the experiment.
2.2. Compression pants The compression pants used represent the three experimental garment variables CG, CG1, and CG2, each a tricot of 92% polyester and 8% polyurethane used previously by Lee et al., 2016 [24]. Each model is designed to apply different levels of pressure; CG applied 0.44—0.58 kPa at the knees, and 0.48—0.68 kPa at the thighs; CG1 applied 0.95—1.03 kPa at the knees, and 0.53—0.71 kPa at the thighs; and CG2 applied 1.67—2.12 kPa at the knees, and 0.80—1.14 kPa at the thighs. The compression pants look as in Fig. 1 when worn on mannequins.
Figure 2
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2.3. Agility and MRCP experiment design The twelve subjects performed sidestep tests and underwent MRCP experiments while wearing the three types of compression pants. To mitigate the order effect, the order in which each subject wore each model of compression pants was differed between subjects using the Latin square method, and the experiment followed the protocol outlined in Fig. 2. The subjects took a 5-minute rest upon arriving at the laboratory before wearing the first compression pants. The first sidestep test was carried out once before a 10minute break, after which the second test was conducted, another 10-minute break was permitted before the third and final test. This protocol was the first set of experiments using the first compression pants, and it was carried out for the other two models in the form of a second and third set of experiments. A break of 5 minutes between the first and second sets was permitted. The subject stood with legs apart in the center of three parallel lines of 1.2 m distance apart from each other. Upon the cue of ‘‘start’’, the first count was measured when the right-hand line was crossed, the second count when the subject returned to the centerline, and upon crossing the left-hand line, the third count was measured. The above motions were performed as fast as possible for 20 seconds. The brainwave measurements were conducted before each subject performed the exercise and action
Protocol of the experiment for evaluating agility and the movement-related cortical potentials experiment.
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performance evaluation. The MRCP experiment was performed 1 week after the agility experiment, as per the defined protocol (Fig. 2). Five minutes’ break was given before the experiment, and EEG and electromyography (EMG) electrodes were attached to the subject. The motions required for MRCP measurement were performed followed by a 5-minute rest. This was the first set of one model of compression pants, and after changing into the second and third models, the second and third sets of the experiment were performed, respectively. As in the agility test, the break time between first set and second set was 5 minutes. The motion performed by the subject during the measurement of MRCPs was as depicted in Fig. 3: the subject wore the compression pants and sat down on a chair, his right leg horizontal to a footrest. Then, the subject raised the right foot, with the leg kept straight to press the foot switch upon hearing the beep sound emitted from the table on the right-hand side. The subject was instructed to press the foot switch as quickly and accurately as possible. The beep sound was designed to sound 32 times at arbitrary intervals of 1 to 5 seconds.
2.4. MRCP data collection and analysis The EEG, EMG, and response trigger signals required for the analysis of MRCPs were measured using the 8-channel polygraph system BIOS-S8 (BioBrain Inc., Daejeon, Korea). The attachment points for EEG electrodes were selected according to Jasper’s (1958) 10—20 System of Electrode Placement, specifically sites Fpz, Fz, Cz, Pz, C3, and C4 [25]. The reference electrode and ground electrode were attached at A1
Figure 4
Figure 3 Illustration of the experimental setup used for the movement-related cortical potentials experiment.
and A2, the rear of each earlobe. For EMG measurements, bipolar patch-type electrodes were attached at the rectus femoris muscle belly. EEG was assigned six channels, EMG was assigned two, and the response trigger signal was assigned one. The measured analog signals were standardized to 250 Hz, converted into digital signals, and sent to the computer. The digital EEG, EMG, and response trigger signals were filtered using bio-signal time series analysis program BioScan
Normalized movement-related cortical potentials and trigger trace.
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Sports compression pants and dextery (BioBrain Inc., Korea) and rendered into brainwave rhythm data according to frequency. Afterwards, a spectrum value reflecting the quantitative brainwave rhythm was computed. Then, as in Terada et al.’s (1995) research, to obtain the MRCPs index, data were trimmed according to response trigger perspective [22]. Ensemble averaging was then performed on these data, resulting in the MRCPs’ waveform, from which the peak amplitude was derived. Analysis of all the data was performed through a big data analysis cloud computing software, BioScan-Cloud (BioBrain Inc., Korea), producing the required information in accordance with the time of the event. As demonstrated in Fig. 4, MRCPs generated prior to activation of the muscles for motor performance were analyzed. The amplitude of each waveform from when the sound stimulus was presented to when the negative peak was reached was extracted. In addition, to compute the subjects’ response time, the time difference from when the sound stimulus was presented to induce motion to when the subject reacted was calculated.
2.5. Statistical analysis The mean and standard deviation of all measured variables were computed using SPSS 20.0 (IBM, New York, USA). The sidestep measurements were analyzed using repeated measures ANOVA. In the case of the statistical processing of MRCP elements, differences in the amplitudes and response times of each MRCP component among the garments were statistically analyzed by the Freidman test for each electrode placement (Fpz, Fz, Cz, C3, C4, and Pz). Statistical significance was defined as P < 0.05.
3. Results 3.1. Agility Fig. 5 compares the average of the number of sidesteps achieved while wearing each compression pants. In all cases, agility increased in the second trial compared to the first (P < 0.042), and a statistically significant difference was identified between compression pants (P < 0.027). When wearing CG2, the pants with the highest pressure level, agility increased significantly from 21.19 ± 1.6 kPa in the first trial to 21.56 ± 1.9 kPa in the second trial. Wearing CG2, which applied relatively high pressure to the legs, affects
Figure 6 5.
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Figure 5 Comparison of agility, as determined by the sidestep experiment, measured for each compression garment.
the nervous system, which in turn awakens and enhances focus on the sidestep test, thereby increasing agility. However, no interaction was found between the compression pants and difference in the number of sidesteps among trials.
3.2. Amplitude of MRCPs Fig. 6 shows averaged MRCPs that underwent movingweighted-average-smoothing. Time zero is when the beep stimulus was presented, and it can be seen that thereafter the recordings of every EEG electrode were negative. Through quantitative analysis of MRCP amplitude, some differences were identified between compression garments. Comparing the amplitude of MRCPs at every electrode placement in Fig. 7, MRCP amplitude associated with CG2 increased the most of all the pants tested. Friedman’s test showed that amplitude increased in the descending order of CG2, CG1, CG, with significant differences at Fz and Cz (P = 0.020 and P = 0.027, respectively). It may therefore be deduced that a compression pants that applies a high pressure level facilitates the performance of the task of deftly reacting to an auditory stimulus. It can also be said that the high pressure pants assist in activating the cognitions of perception and recognition central to performing physical tasks.
Averaged waveforms of movement-related cortical potentials recorded at each of the electrode placements of subject
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Figure 7
Average amplitude of movement-related cortical potentials for each garment. Error bars represent S.D.
Figure 8 Average response times of the motion performance task for each tested garment.
3.3. Response time Average response times for each of the tested garments are shown in Fig. 8. When wearing CG2, the compression garment with the highest pressure level, the response latency was the lowest (0.61 seconds), but this difference was not statistically significant (P = 0.121). However, response time decreased as the pressure level increased, and therefore, it can be said that quick response time was related to wearing CG2. CG2 was associated with enhanced speed, a major element of sport and a property of the nervous system. However, in the present study, this difference did not reach statistical significance.
4. Discussion This research investigated the effect of compression pants’ pressure level on the brain’s information handling process
in relation to agility, a basic motor skill key to sport. Current commercial sports compression garments are designed to apply partial or differential pressure according to their intended purpose and are marketed with an emphasis on the fact that they offer certain benefits to one’s sporting performance. These methods of designing compression garments with differential pressure, partial pressure, and pressure level support certain muscles, allowing the wearer to focus on performing the task at hand. As a result, it can be said that agility is enhanced by excluding needless effort during sports activities and delivering precise nervous orders to the necessary muscles. Doan et al. (2003) stated that the elasticity of compression garments reduces activation of antagonistic muscles through pressure upon running and produces torques supporting the hamstrings [3]. Zhou (2013) stated that functions of compression garments, such as enhanced mobility, muscle support, and protection from joint damage vary according to their level of elasticity [26]. Lee et al. (2016) also classified compression pants with different pressure levels into those that function to protect the body against impact from landing and those that function to access the full potential of muscle capabilities through kinematic and kinetic evaluation [24]. Bringard et al. (2006) showed that a compression garment exerting a pressure of 3.06 kPa over the gastrocnemius muscle increases muscular oxygenation [9]. In addition, Scanlan et al. (2008) found that compression garments that apply high pressure on the limbs (gastrocnemius, 2.31 kPa; vastus lateralis, 1.99 kPa) significantly improve muscle oxygenation economy during a 1-h cycling time trial [27]. In practice, when Choi et al. (2014) measured the brainwaves of participants as they walked wearing compression garments of different pressure levels, the participants reported significantly less relaxation when wearing higher pressure garments, a variable that also showed a positive correlation with cognitive load index, relative beta wave emitted upon awakening, and concentration index [28]. The results of this research also show significant increases in agility when wearing the compression garment with the highest pressure level, CG2. This may
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Sports compression pants and dextery be explained similarly to the previously discussed study, in contrast, as agility is a fundamental component of quick decision making, nervous and muscular coordination, and muscle contraction speed of the central nervous system. The present research analyzed MRCPs to further understand the relationship between the brain’s information handling process and the brain’s reaction. This study found that wearing CG2 while performing the voluntary movement of leg raises increased the amplitude of MRCPs at Cz and Fz and reduced the response time. Increased MRCP amplitude has been interpreted in several different ways in the literature. In research by Taylor (1978) measuring the preparation transition between sections that have acquired certain actions and have been experimented by, it is claimed that when motion tasks are acquired and are repeatedly carried out, MRCP amplitude increases in tandem with performance enhancement [29]. It is therefore also reported that this amplitude increase reflects the subjects’ motor task performance proficiency. In addition, MRCP amplitude is proportional to preparation level, since amplitude and latency require further preparation procedures when one performs smooth motion tasks compared to fast motion tasks [30,31]. However, some researchers argue that as sports education and technique acquisition are performed, the success rate of MRCPs increases, but the amplitude decreases. Wright (2012) argues in his report on 5 weeks of research regarding the brain’s change in the motion preparation process involved in playing the guitar that the motor readiness potential decreases as the negative slope decreases [32]. This study also found that guitar-playing proficiency improved with practice. Moreover, professional athletes and pianists are more skilled at performing the tasks of their respective professions, but not at tasks in general, thereby shortening the neural circuit and allowing effective cortex activities, ultimately reducing the amplitude of the MRCPs [33—35]. In these studies, motor cortex activity decreased as kinesthetic memory was reinforced and automatized, and as skill was enhanced, but it is argued that this was because effective task performance was carried out. However, unlike the studies above, where sports education was an independent variable, this study was carried out with compression garments as a variable, thus requiring a different interpretive approach. In short, this study adopted a new perspective on MRCPs by setting compression garments as an independent variable. Specific experimental protocols were designed to observe agility and amplitude of MRCPs and response time affected by the independent variable. In order to examine effects of compression garments exclusively, experimental subjects were limited to non-athletes. The order of wearing experimental garments was planned using a Latin square to control and eliminate any effect caused by it. Different sound stimuli were computer programmed to be played for each experiment. Therefore, it was expected that the only independent variable that had significant influence on the research results would be pressure levels of the experimental garments. Our study could show that the effect of repeated learning was trivial because there was only a small standard error in each experiment when each average and standard deviation was statistically processed. We found that agility and response time are enhanced when wearing CG2, and the amplitude of MRCPs is increased,
7 signifying focused activation of motor information handling processes such as perception and recognition, therefore implying successful performance of the motion tasks. As explained beforehand, the pressure applied on the legs through compression pants increased alertness and focus on motor task performance, thereby enhancing motor information processing in the brain. As known from previous studies on compression garments, skin pressure exerted by compression garments has physiologically, dynamically and psychologically beneficial effects on the wearer. It could be interpreted from our study that pressure level of compression garments causes significant differences to MRCPs, which enable the beneficial effects mentioned above for the wearer.
5. Conclusions In this study, wearing CG2, the compression pants with the highest pressure level, enhanced agility and response time as well as increased the amplitude of MRCPs. This implies that the pressure level of compression pants is a major variable in clothing design that impacts the brain’s perception handling processes and motor skills. Furthermore, the function of compression garments differed according to their elasticity and pressure level. Most commercialized compression garments available up to the present day have focused on marketing and advertising based on their various functions. However, this research implies that compression pants with relatively low pressure levels may not be able to perform these functions maximally. Moreover, pressure level may change according to not only the size of the clothing, but also body measurements, thus calling for caution in the generalization of their functions. The present study also analyzed the effect of compression pants on the nervous system through brainwave measurements, a feature that sets this study apart from previous research. However, owing to the limited selection of garment models and motor tasks tested in this study, a more comprehensive investigation in this research domain is warranted. Moreover, there will be a significant benefit in performing a similar research study as a follow-up.
Disclosure of interest The authors declare that they have no competing interest.
Acknowledgements This study was supported by research fund of Chungnam National University in 2015.
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