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Lower muscle co-contraction in flutter kicking for competitive swimmers
Abstract
The purpose of this study was to examine the difference in muscle activation pattern and co-contraction of the rectus and biceps femoris in flutter-kick swimming between competitive and recreational swimmers, to better understand the mechanism of repetitive kicking movements during swimming. Ten competitive and 10 recreational swimmers swam using flutter kicks at three different velocities (100%, 90%, and 80% of their maximal velocity) in a swimming flume. Surface electromyographic signals (EMG) were obtained from the rectus (RF) and biceps femoris (BF), and lower limb kinematic data were obtained at the same time. The beginning and ending of one kick cycle was defined as when the right lateral malleolus reached its highest position in the vertical axis. The offset timing of muscle activation of RF in the recreational swimmers was significantly later at all velocities than in the competitive swimmers (47-48% and 26-33% of kick time of one cycle for recreational and competitive swimmers, respectively), although the kinematic data and other activation timing of RF and BF did not differ between groups. A higher integrated EMG of RF during hip extension and knee extension induced a higher level of muscle co-contraction between RF and BF in the recreational swimmers. These results suggest that long-term competitive swimming training can induce an effective muscle activation pattern in the upper legs.
... Among 16 included studies in this review, 13 papers investigated muscle activity during swimming phase, including performing in 100m (Puce et al., 2021;Rouard and Clarys, 1995;Stirn et al., 2011) or 200m FC swim (Figueiredo et al., 2013a;Figueiredo et al., 2013b;Ikuta et al., 2012;Lauer et al., 2013), 25m swim (Martens et al., 2015a; or semi-tethered swim (Caty et al., 2007), and swimming in the flume with arms only or flutter kick in competitive swimmer only (Lomax et al., 2014;Matsuda et al., 2016). One study has investigated and compared the trunk muscle activity during both sprinting (4 x 50m FC) and middledistance (400m) swim (Andersen et al., 2021). ...
... Concerning the selection of body parts for investigation, the most frequently investigated was the upper body (n = 11), lower body (n = 8) and then followed by the trunk muscles (n = 5), the total number is more than 14, as some papers investigated more than one body part in their research. Most of the studies conducted their measurement in unilateral side (n=12) and mainly investigated right side's muscles (n = 8) (Andersen et al., 2021;Caty et al., 2007;Figueiredo et al., 2013b;Ikuta et al., 2012;Lauer et al., 2013;Lomax et al., 2014;Stirn et al., 2011;Yamakawa et al., 2017) , but some studies did not clearly mention what side they were investigated (n = 5) (Figueiredo et al., 2013a;Kobayashi et al., 2016;Matsuda et al., 2016;Pereira et al., 2015;Rouard and Clarys, 1995). While 2 studies conducted bilaterally (n = 2) (Martens et al., 2016) (both left and right muscles selected), however, some studies (Pereira et al., 2015;Puce et al., 2021) investigated the side according to their hand dominance. ...
... With regard to the quantity of muscle selection, the highest number of muscles included was Ikuta's study (Ikuta et al., 2012) that authors selected 11 muscles to evaluate the muscle fatigue during 100m FC, while the least number was 2 muscles selected in 6 studies (Caty et al., 2007;Lauer et al., 2013;Lomax et al., 2014;Martens et al., 2015a;Matsuda et al., 2016) with different study objectives. With respect to upper body parts, in total 12 muscles were selected among those included studies. ...
This systematic review is aimed to provide an up-to-date summary and review on the use of surface electromyography (sEMG) in evaluating front crawl (FC) swim performance. Several online databases were searched by different combinations of selected keywords, in total 1956 articles were retrieved, and each article was assessed by a 10-item quality checklist. 16 articles were eligible to be included in this study, and most of the articles were evaluating the muscle activity about the swimming phases and focused on assessing the upper limbs muscles, only few studies have assessed the performance in starts and turns phases. Insufficient information about these two phases despite the critical contribution on final swimming time. Also, with the contribution roles of legs and trunk muscles in swimming performance, more research should be conducted to explore the overall muscle activation pattern and their roles on swimming performance. Moreover, more detailed description in participants’ characteristics and more investigations of bilateral muscle activity and the asymmetrical effects on relevant biomechanical performance are recommended. Lastly, with increasing attention about the effects of muscles co-activation on swimming performance, more in-depth investigations on this topic are also highly recommended, for evaluating its influence on swimmers.
... 18,19 Outra técnica de análise que vem ganhando campo é a utilização da eletromiografia de superfície. [20][21][22] Não obstante, menos tradicionais são as análises que contam com cálculos das forças que afetam o nadador. 12,23 Porém, a base das avaliações dos membros inferiores continua sendo as avaliações por cinemática, as quais retiram das imagens as conclusões esperadas. ...
... 12,23 Porém, a base das avaliações dos membros inferiores continua sendo as avaliações por cinemática, as quais retiram das imagens as conclusões esperadas. 15 [20][21][22]38,42,46 Com relação aos temas, pode-se perceber que a maioria dos artigos avaliou as fases dos movimentos das pernas e dos braços na natação, como as flutuações de velocidade intracíclica e coordenação entre estes. 3,18,20,26,40,41,52,55,56,58 Ainda nas coordenações, alguns estudos fizeram comparações entre nadadores de elite e iniciantes. ...
... 3,18,20,26,40,41,52,55,56,58 Ainda nas coordenações, alguns estudos fizeram comparações entre nadadores de elite e iniciantes. 4,22,27,42,43,50,57,60 As variáveis fisiológicas, em detrimento das biomecânicas, também foram bem estudadas. Os artigos buscaram diferenças na cinemática e no custo de energia entre os nados e a utilização dos membros inferiores. ...
Atualmente se sabe que a velocidade da natação é uma função da propulsão gerada a partir dos membros inferiores e não apenas dos membros superiores. No entanto, por anos, a ação das pernas, durante o nado, teve sua importância mitigada. Dessa forma, o objetivo deste trabalho foi levantar, por meio de uma revisão integrativa da literatura, o estado da arte acerca da importância dos membros inferiores na natação. Esta pesquisa foi delimitada na ação das pernas de superfície e pernas subaquáticas, excluindo-se as análises das saídas e viradas. Foram analisados estudos indexados nas seguintes bases de dados: Web of Science, PubMed, Scopus, Lilacs e SciELO. A sistematização de busca incluiu leitura de títulos, resumos e artigos na íntegra, encontrados por meio de blocos de descritores que combinaram termos principais e secundários. Um total de 154 artigos foi encontrado, dos quais 55 foram incluídos para análise qualitativa. Os resultados mostraram que os estudos sobre a utilização dos membros inferiores na natação possuem baixo valor amostral e descrição heterogênea dos níveis dos participantes. O nado peito e as ondulações subaquáticas são as variáveis mais estudadas. Preconiza-se examinar a eficácia de outras variáveis antropométricas, cinemáticas e de coordenação para entender melhor a produção da velocidade máxima e considerar a importância de técnicas individuais na ação das pernas na natação. Ainda, no campo da utilização dos membros inferiores na natação, existem algumas lacunas, as quais os próprios artigos apontam. Essas demandas ficam por conta da força gerada por esses segmentos, além da discussão da importância em se considerarem fatores individuais na ação das pernas para os nadadores.
... Furthermore, flexor and extensor muscles in the trunk, thigh, and leg are required to contract alternately during dolphin kicking (McLeod, 2010). In other cyclical movements requiring reciprocal activation between agonist and antagonist muscles, co-activation between the muscles assumes an inefficient muscular activation pattern (Fujii, Kudo, Ohtsuki, & Oda, 2009;Heuer, 2007;Matsuda et al., 2016). Winter (2009) suggested that an obvious co-contraction is inefficient in a dynamic movement because agonist and antagonist muscles fight against each other without producing a net movement. ...
... That study investigated the muscular activation pattern during flutter kicking, and reported that the activation pattern between agonist and antagonist muscles in the thigh and leg of skilled swimmers was more reciprocal compared to that of novice swimmers. Matsuda et al. (2016) investigated the co-activation between the RF and BF Table 3 The correlation coefficients (r) between the co-active phase of each muscle pair (rectus abdominis-erector spinae; RA-ES, rectus femoris-biceps femoris; RF-BF, tibialis anterior-gastrocnemius; TA-GAS) and the average swimming velocity or the Froude efficiency. during flutter kicking, and reported that co-activation during the phase of hip extension and knee flexion in competitive swimmers was significantly lower than that in recreational swimmers. ...
... On the other hand, we also considered that the co-activation of agonist and antagonist muscles might be reduced by training. Matsuda et al. (2016) investigated the activation pattern between the RF and BF during flutter kick swimming in skilled swimmers and novices, and reported that the co-activation level of two muscles in skilled swimmers was low compared to that of novice swimmers. Therefore, if a swimmer wants to increase the kick frequency of the underwater dolphin kick, the swimmer should train to reduce muscular co-activation during underwater dolphin kick swimming at the supra-maximum kick frequency. ...
In this study, we investigated the effects of increased kick frequency on the propelling efficiency and the muscular co-activation during underwater dolphin kick. Participants included eight female collegiate swimmers. The participants performed seven 15-m underwater dolphin kick swimming trials at different kick frequencies, which is 85, 90, 95, 100, 105, 110, and 115% of their maximum effort. The Froude (propelling) efficiency of the dolphin kick was calculated from the kinematic analysis. The surface electromyography was measured from six muscles (rectus abdominis, erector spinae, rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius). From the EMG data, the co-active phase during one cycle in the trunk, thigh, and leg was evaluated. Our results show that the Froude efficiency decreased at the supra-maximum kick frequency (e.g. 100%F: 0.72 ± 0.03 vs. 115%F: 0.70±0.03, p < .05). The co-active phase in the trunk, thigh, and leg increased with increasing the kick frequency (e.g. 85%F vs. 115%F, p < 0.05). Furthermore, it was observed that there was a negative relationship between the trunk co-active phase and the Froude efficiency (r = −0.527, p < 0.05). Therefore, both the propelling efficiency and the muscular activation pattern became inefficient when the swimmer increased their kick frequency above their maximum effort.
... Some swimmers have a "high elbow" action characterized by a flexed elbow that positions the hand below the level of the elbow throughout the recovery from the instant of hand exit to the instant of hand entry, which could contribute to body roll efficiency (Yanai 2004). In swimming textbooks, it is common to see the high elbow recovery recommended as a means of reducing the moment of inertia of the upper limbs about a vertical axis of the body and thereby reducing the tendency for counter rotations that affect the alignment of the body and increase resistive drag (Maglischo 2003). However, some excellent world champions, including the American middle-and long-distance swimmer Janet Evans, had a style in which the elbow was considerably extended throughout recovery. ...
... Several other researchers have echoed this effect of the flutter kick in front crawl swimming. Vorontsov and Rumyantsev (2000) and McCullough et al. (2009) stated that one role of the leg movements is to neutralize forces created by the arm stroke and Maglischo (2003) believes that the flutter kick helps to stabilize the hips. Sanders and Psycharakis (2009) explored the possibility that the trunk plays a very active role in the transmission of motion to the feet in front crawl swimming. ...
This chapter explores the cooperative coordination of segmental motions that optimizes performance in front crawl swimming. The chapter reveals how understanding of swimming technique and performance has advanced through the application of technology. The mystery of how propulsion is achieved in human swimming is being unraveled through observation of water flow associated with upper and lower limb motions using particle image velocimetry (PIV) and computational fluid dynamics (CFD) combined with video-based three-dimensional analysis of swimming motions. These methods are supplemented with direct pressure measurement of forces acting on the hands and feet and in combination provide input for computer simulations and programmed swimming actions of robots. Improved understanding of the mechanisms of propulsion emerging from these coordinated approaches will translate into improved coaching methods for sprint and distance swimming with consideration of the energy cost and physiological constraints.
... Some swimmers have a "high elbow" action characterized by a flexed elbow that positions the hand below the level of the elbow throughout the recovery from the instant of hand exit to the instant of hand entry, which could contribute to body roll efficiency (Yanai 2004). In swimming textbooks, it is common to see the high elbow recovery recommended as a means of reducing the moment of inertia of the upper limbs about a vertical axis of the body and thereby reducing the tendency for counter rotations that affect the alignment of the body and increase resistive drag (Maglischo 2003). However, some excellent world champions, including the American middle-and long-distance swimmer Janet Evans, had a style in which the elbow was considerably extended throughout recovery. ...
... Several other researchers have echoed this effect of the flutter kick in front crawl swimming. Vorontsov and Rumyantsev (2000) and McCullough et al. (2009) stated that one role of the leg movements is to neutralize forces created by the arm stroke and Maglischo (2003) believes that the flutter kick helps to stabilize the hips. Sanders and Psycharakis (2009) explored the possibility that the trunk plays a very active role in the transmission of motion to the feet in front crawl swimming. ...
This chapter explores the cooperative coordination of segmental motions that optimizes performance in front crawl swimming. The chapter reveals how understanding of swimming technique and performance has advanced through the application of technology. The mystery of how propulsion is achieved in human swimming is being unraveled through observation of water flow associated with upper and lower limb motions using particle image velocimetry (PIV) and computational fluid dynamics (CFD) combined with video-based three-dimensional analysis of swimming motions. These methods are supplemented with direct pressure measurement of forces acting on the hands and feet and in combination provide input for computer simulations and programmed swimming actions of robots. Improved understanding of the mechanisms of propulsion emerging from these coordinated approaches will translate into improved coaching methods for sprint and distance swimming with consideration of the energy cost and physiological constraints.
... Based on this result, we presume that muscle synergy of ankle muscles would be a major factor of a highly developed motor strategy for postural control. Our presumption is supported by findings of previous reports that highly developed motor strategies are related to low co-contraction between agonists and antagonists in various voluntary movements (Aoki & Kinoshita, 2001;Bazzucchi, Riccio, & Felici, 2008;Fujii, Kudo, Ohtsuki, & Oda, 2009;Furuya & Kinoshita, 2007;Matsuda et al., 2016). For instance, skilful hands showed less co-activation of antagonists during repetitive movements such as finger tapping (Aoki & Kinoshita, 2001), stroking a piano key (Furuya & Kinoshita, 2007) and drumming (Fujii et al., 2009) than non-skilful hands. ...
... For instance, skilful hands showed less co-activation of antagonists during repetitive movements such as finger tapping (Aoki & Kinoshita, 2001), stroking a piano key (Furuya & Kinoshita, 2007) and drumming (Fujii et al., 2009) than non-skilful hands. Trained swimmers and tennis players also showed lower co-contraction of antagonist muscles in swimming, kicking (Matsuda et al., 2016) and isokinetic elbow flexion exercise than novices (Bazzucchi et al., 2008), respectively. Considering the independent activation of ankle plantar flexors in EA, development of this motor control strategy would be of considerable value for training of athletes requiring a high level of body balance. ...
This study aimed to investigate specific muscle synergies in elite ice hockey players indicating highly developed postural control strategies used to restore balance against unexpected external perturbations. Seven elite athletes (EA) on the women’s national ice hockey team and 7 non-athletes (NA) participated in this study. Based on trajectories of centre of mass (COM), analysis periods were divided into an initial phase (a balance disturbance after perturbation onset) and a reversal phase (a balance recovery response), respectively. Muscle synergies were extracted at each phase by using non-negative matrix factorization. k-means cluster analysis was performed to arrange similar muscle synergies in all participants. EA showed significantly shorter recovery period of COM and smaller body sway than NA. In the initial phase, we identified 2 EA-specific synergies related to ankle plantar flexors or neck extensors. In the case of an NA-specific synergy, co-activation of the ankle plantar flexors and dorsiflexors was found. In the reversal phase, no specific muscle synergies were identified. As the results, EA-specific muscle synergies showed low co-activation strategy of agonists and antagonists in ankle and neck extensors. Our results could provide critical information for rehabilitation strategies in athletes requiring high postural stability.
... In animal models, the pattern of muscle contraction elicited during swimming could explain the differences found between femur and tibia cortical geometry. In humans, freestyle kicking during swimming primarily recruits the hip flexors and extensors, since knee flexion and extension generates a less propulsive force [99,100]. Gluteus maximus, biceps femoris and rectus femoris, which all have insertions at the femur, are more intensely recruited than gastrocnemius and tibialis anterior during the swimming kick [101]. ...
Background
The effect of swimming on bone health remains unclear, namely due to discrepant findings between studies in humans and animal models.
Objective
The aim of this systematic review and meta-analysis is to identify the available evidence on the effects of swimming on bone mass, geometry and microarchitecture at the lumbar spine, femur and tibia in both humans and rodent animal models.
Methods
The study followed PRISMA guidelines and was registered at PROSPERO (CRD4202236347 and CRD42022363714 for human and animal studies). Two different systematic literature searches were conducted in PubMed, Scopus and Web of Science, retrieving 36 and 16 reports for humans and animal models, respectively.
Results
In humans, areal bone mineral density (aBMD) was similar between swimmers and non-athletic controls at the lumbar spine, hip and femoral neck. Swimmers' tibia diaphysis showed a higher cross-sectional area but lower cortical thickness. Inconsistent findings at the femoral neck cortical thickness were found. Due to the small number of studies, trabecular microarchitecture in human swimmers was not assessed. In rodent models, aBMD was found to be lower at the tibia, but similar at the femur. Inconsistent findings in femur diaphysis cross-sectional area were observed. No differences in femur and tibia trabecular microarchitecture were found.
Conclusion
Swimming seems to affect bone health differently according to anatomical region. Studies in both humans and rodent models suggest that tibia cortical bone is negatively affected by swimming. There was no evidence of a negative effect of swimming on other bone regions, both in humans and animal models.
... Los nadadores avanzan por las fuerzas propulsivas que producen sus extremidades, siendo mayor la velocidad cuando hay un buen rendimiento en el movimiento de piernas. El movimiento de las extremidades inferiores comienza en la cadera y va descendiendo por la rodilla hasta llegar a tobillo y pie 4 . Sin embargo, se ha encontrado poca bibliografía que se centre en los efectos que provoca este deporte en tobillo, siendo más frecuente encontrar investigaciones sobre dolor de espalda y hombro del nadador 5 . ...
... Because of the complexity of the movement in an aquatic environment, the measurement of surface electromyography characteristics of swimmers was not easy to carry out. Previous studies had examined the difference in muscle activation pattern and cocontraction of upper or lower limbers compared the different muscular activation between different levels of swimmers [9][10][11][12][13][14]. However, these studies focused mostly on front crawl swimming and merely mentioned other effect on muscle activation such as different swimming speed. ...
Objective
To investigate effect of flow speeds on the upper limb muscular activity of butterfly swimmers training in a flow environment. A comparison of kinematic characteristics and muscular activity of upper limbs were made when the swimmers training with different flow speeds in a swimming flume. The purpose was to provide a basis for scientifically formulating special swimming training advice for athletes' training in flow environment.
Methods
Ten youth female butterfly swimmers participated in the study with the speed of 70%, 80%, and 90% level of their max speeds. A stroke cycle was divided into four phases (entry, pull, push, and recovery). The kinematic parameters of upper limbs (stroke rate, stroke length, duration of each phase in a stroke cycle) and muscular activity (onset timing, integrated electromyography (iEMG), contribution ratio) of four muscles (Biceps brachii (BB), Triceps brachii (TB), Pectoralis major (PM), and Latissimus dorsi (LD)) were collected and analyzed in different stroke phases.
Results
There was no significant difference between stroke rate and stroke length with different flow speeds. There were significant differences among the duration of the four stroke phases. The entry phase had the longest duration, the pull phase had the shortest duration, the push phase was longer than the recovery phase, and the recovery phase was shorter than the entry phase. The BB and PM were activated significantly earlier at 90% of target speed than at 80% of target speed, while the TB was activated significantly later than other two speeds. The muscular contribution ratio of the PM was highest in the pull phase and lowest in the pushing phase. The muscular contribution ratio of the BB was significantly lower in the pushing phase than in other three stroke phases. The muscular contribution of the TB was significantly higher in the recovery phase than in other three stroke phases. The muscular contribution ratio of the LD was highest in the pushing phase, and it was significantly higher in pushing phase and recovery phase than in pull phase.
Conclusions
(1) When butterfly athletes training with 70%, 80% and 90% of their max speed in a flow environment, it didn't make significant differences between the kinematic or muscle activation characteristics of the upper limbs movement except the muscle onset timing. (2) Stroke phase was the main factor of the duration and the muscle contribution ratio during butterfly arm stroke for young athletes.
... Olstad et al. (2017) investigated muscle activity in the upper and lower limbs during breaststroke swimming at 60, 80, and 100% effort and reported that the mean activation pattern remained similar across the different effort levels, but the muscles showed longer activation periods relative to the stroke cycle and increased the intensity of muscle activity with increasing effort. Matsuda et al. (2016) investigated muscle activity in the rectus and biceps femoris during flutter kicking and reported that the intensity of thigh muscles increased with increasing swimming velocity, but that the co-activation level between the muscles did not change. Thus, the intensity of muscle activity in the areas related to specific swimming motions increased with increasing swimming velocity. ...
This study aimed to investigate the changes in kinematics and muscle activity with increasing swimming velocity during underwater undulatory swimming (UUS). In a water flume, 8 male national-level swimmers performed three UUS trials at 70, 80, and 90% of their maximum swimming velocity (70, 80, and 90%V, respectively). A motion capture system was used for three-dimensional kinematic analysis, and surface electromyography (EMG) data were collected from eight muscles in the gluteal region and lower limbs. The results indicated that kick frequency, vertical toe velocity, and angular velocity increased with increasing UUS velocity, whereas kick length and kick amplitude decreased. Furthermore, the symmetry of the peak toe velocity improved at 90%V. The integrated EMG values of the rectus femoris, biceps femoris, gluteus maximus, gluteus medius, tibialis anterior, and gastrocnemius were higher at 90%V than at the lower flow speeds, and the sum of integrated EMGs increased with increasing UUS velocity. These results suggest that an increase in the intensity of muscle activity in the lower limbs contributed to an increase in kick frequency. Furthermore, muscle activity of the biceps femoris and gastrocnemius commenced slightly earlier with increasing UUS velocity, which may be related to improving kick symmetry. In conclusion, this study suggests the following main findings: 1) changes in not only kick frequency but also in kicking velocity are important for increasing UUS velocity, 2) the intensity of specific muscle activity increases with increasing UUS velocity, and 3) kick symmetry is related to changes in UUS velocity, and improvements in kick symmetry may be caused by changes in the muscle activity patterns.
... Although no multi-task effect was apparent when controlling the kick frequency with a metronome (Yamakawa et al., 2017b), it was observed that the muscle co-activation increased when increasing the kicking frequency above the preferred frequency. Based on the lower muscle co-activation showed by more skilled swimmers in flutter kicking than in recreational swimmers (Matsuda et al., 2016), it was suggested that a training period might be required to reduce such muscular co-activation and obtain performance improvements (Yamakawa et al., 2017a). ...
The prominence of undulatory underwater swimming (UUS) has been clearly observed during recent international events. Improvement of this phase is important for overall performance. The aim of this systematic review was to identify the key factors that modulate UUS performance and provide coaches and sports science practitioners with valuable and practical information to optimise it. PubMed, Web of Science, Scopus, and SPORTDiscus databases were searched up to 14 October 2021. Studies involving competitive swimmers and which included UUS performance assessment were considered. Methodological quality assessment was conducted for the included articles. From the 193 articles screened, 15 articles were included. There was a substantial body of research conducted on kicking frequency, vertical toe and body wave velocity, angular velocity of the joints, distance per kick, joint amplitudes and mobility, and body position in UUS performance. However, further investigation is required for muscle activation and muscle strength influence. The results from this review contribute to understanding of how to optimise UUS performance, identifying the key aspects that must be addressed during training. Specifically, the caudal momentum transfer should be maximised, the upbeat duration reduced, and the frequency that best suits swimmers' characteristics should be identified individually.
... Jumping involves activation of a number of leg muscles, notably the quadriceps and hamstrings (Charoenpanicha et al., 2013). Flutter kicking during freestyle swimming also involves activation of the quadriceps and hamstrings (Matsuda et al., 2016), but in ways that are fairly different from how those muscles are employed during jumping. If observers' perceptions of actors' maximum jumping reach heights improve after viewing the actor squat to lift a weight (a behavior that involves the same muscles as jumping, and involves similar movements), and after viewing the actor flutter kick (a behavior that involves the same muscles as jumping, but involves different movements), but not twisting at the waist (a behavior that involves different muscles than jumping), then that would support that related, but not identical, behaviors that are informative about a given affordance involve muscle groups that are used during actualization of that affordance. ...
A considerable amount of research has worked toward enabling robot caregivers to perform various tasks for individuals in need of assistance. However, little, if any, research has aimed to enable robot caregivers to determine when individuals need help performing tasks. One way to develop such robots is to start with what is already known about people determining whether other people can perform a task without help. Ecological Psychologists conceptualize that task in terms of people perceiving other people’s affordances. There is an extensive and growing literature concerning the perception of others’ affordances, which has provided many important insights. Hence, our long-term goal is to develop robot caregivers that perceive people’s affordances in ways that are similar to how people perceive others’ affordances, which will require a considerable amount of research. As a first step, we have carefully reviewed the Ecological Psychology literature concerning how people perceive other people’s affordances and discuss how such knowledge might inform the design of robot caregivers. In addition, we identify areas that, if further researched, would shed additional light on how to design robot caregivers that perceive people’s affordances, and move us toward a fuller understanding of how people perceive other people’s affordances.
... For joint angle analysis, the four local coordinate systems in trunk, thigh, leg and foot segments were defined, and the joint angles were calculated as Cardan angle using these coordinate systems (Robertson, 2004). In this study, one dolphin kick cycle was divided into four phases according to Matsuda et al. (2016): 1) the phase involves hip flexion with knee flexion (Phase A), 2) the phase involves hip flexion with knee extension (Phase B), 3) the phases involves hip extension with knee extension (Phase C) and 4) the phase involves hip extension with knee flexion (Phase D). The relative duration (%) normalized by the cycle duration in each phase were calculated. ...
The purpose of this study was to clarify about the changes of the kinematics during underwater undulatory swimming (UUS) with increasing the swimming velocity. Eight male collegiate swimmers performed three UUS trials at the 70%, 80% and 90% velocity of their maximum effort swimming velocity in a water flume. For motion analysis, a motion capture system was used to collect the three-dimensional coordinates. Using the collected coordinates, the kinematic parameters were analyzed in each trial. As the main results, the kick frequnecy increased and the relative duration of the un-propusive phase with hip extension and knee felxion decreased with increasing swimming velocity. Furtheremore, since the peak hip external roation velocity increased with increasing swimming velocity, it was considered that the hip external rotation velocity during the downward kicking related to controll the swimming velocity during underwater undulatory swimming.
Electromyography has been used for half a century as a method for evaluating muscle activity during swimming. In swimming research, surface electromyography is mainly measured, and from the data, it is possible to know which muscles at what timing and how much are active during swimming motions. In some previous studies, surface electromyography was also used to evaluate muscle coordination and muscle fatigue. In recent years, with the technological evolution of surface electromyography system, it has become much easier than before to measure muscle activity during swimming. Therefore, some recent studies have attempted muscle synergy analysis using data obtained by measuring multiple muscles. As the future prospect, it is expected that electromyography studies combined with other analytical methods, the studies focusing on swimming styles other than front crawl, and the ones analyzing the effects of trainings on muscle activity will be reported.
The purpose of this study was to investigate the effect of knee extension/flexion and fatigue on muscle co-activation of the Rectus Femoris (RF) and Biceps Femoris (BF) during the eggbeater kick. Ten national level male water polo players executed eggbeater kicks at maximum effort for the duration of the test. The eggbeater kick cycle was divided into four phases (FLX1, FLX2, EXT1, EXT2). Surface electromyographs were recorded from RF and BF. EMG activity normalized to the maximum voluntary isometric contraction, muscle co-activation (CCI) and angular velocity (AV) of the right and left knee were calculated. Highest levels of RCCI and LCCI were observed during final phase of flexion (FLX2) and initial phase of extension (EXT1) (p < 0.05). FLX2 and final phase of extension (EXT2) revealed the highest AV during the cycle. A decrease in CCI was observed with fatigue for FLX2 while AV was reduced for all phases. During the cycle RF and BF act as agonist/antagonist to accelerate and decelerate knee flexion/extension. The high AV and low CCI levels observed for EXT2 might increase joint instability and consequent risk of injury. This knowledge provides a better understanding of the mechanisms involved in stabilizing and controlling the knee during underwater movement.
Muscular coactivation can help stabilise a joint, but contrasting results in previous gait studies highlight that it is not clear whether this is metabolically beneficial. The aim was to assess the relationship between the metabolic cost of running and muscular coactivation across different running speeds, in addition to assessing the reliability and precision of lower limb muscular coactivation.
Eleven female recreational runners visited the laboratory on two separate occasions. On both occasions subjects ran at three speeds (9.1, 11 and 12kmh(-1)) for six minutes each.
Oxygen consumption and electromyographic data were simultaneously recorded during the final two minutes of each speed. Temporal coactivations of lower limb muscles during the stance phase were calculated. Five muscles were assessed: rectus femoris, vastus lateralis, biceps femoris, tibialis anterior and gastrocnemius lateralis.
Nonparametric correlations revealed at least one significant, positive association between lower limb muscular coactivation and the metabolic cost of running for each speed. The length of tibialis anterior activation and muscular coactivation of the biceps femoris-tibialis anterior and gastrocnemius lateralis-tibialis anterior decreased with speed.
These results show that longer coactivations of the proximal (rectus femoris-biceps femoris and vastus lateralis-biceps femoris) and leg extensor (rectus femoris-gastrocnemius lateralis) muscles were related to a greater metabolic cost of running, which could be detrimental to performance. The decrease in coactivation in the flexor and distal muscles at faster speeds occurs due to the shorter duration of tibialis anterior activation as speed increases, yet stability may be maintained.
Abstract The aim of this study was to examine the influence of leg kick on the pattern, the orientation and the propulsive forces produced by the hand, the efficiency of the arm stroke, the trunk inclination, the inter-arm coordination and the intra-cyclic horizontal velocity variation of the hip in sprint front crawl swimming. Nine female swimmers swam two maximal trials of 25 m front crawl, with and without leg kick. Four camcorders were used to record the underwater movements. Using the legs, the mean swimming velocity increased significantly. On the contrary, the velocity and the orientation of the hand, the magnitude and the direction of the propulsive forces, as well as the Froude efficiency of the arm stroke were not modified. The hip intra-cyclic horizontal velocity variation was also not changed, while the index of coordination decreased significantly. A significant decrease (13%) was also observed in the inclination of the trunk. Thus, the positive effect of leg kick on the swimming speed, besides the obvious direct generation of propulsive forces from the legs, could probably be attributed to the reduction of the body's inclination, while the generation of the propulsive forces and the efficiency of the arm stroke seem not to be significantly affected.
The aims of this study were (1) to evaluate changes in muscle activity associated with physiological fatigue and decreased swimming velocity (SV) during 200 m of front crawl swimming, and (2) to examine the relationship between the decreased SV and changes in kinematic or electromyogram parameters. Twenty swimmers participated in a 4 × 50-m swim test. The surface EMG of 11 muscles (7 in the upper limbs and 4 in the lower limbs) was measured and the mean amplitude value (MAV) for one stroke cycle was obtained. The SV and arm angular velocity (AAV) of shoulder flexion during the first (early stroke) and second (late stroke) half of the underwater arm stroke were analyzed using an underwater camera. The AAV, the MAV of flexor carpi ulnaris (FCU), biceps brachii (BB), and triceps brachii during the early stroke, and the MAV of rectus femoris decreased along with a decrease in SV. In contrast, the MAV of the pectoralis major (PM) increased significantly in the final 50 m. The rate of change in MAVs (ΔMAVs) of FCU, BB and latissimus dorsi during the early stroke, and ΔMAV of biceps femoris were significantly correlated with ΔSV and/or ΔAAV. Positive correlations were identified between ΔMAVs of several muscles. However, no negative correlations were observed between ΔMAVs. These results suggest that the decrease in SV was related to decreases in the activities of several muscles that coordinated with each other, and that a compensating strategy occurred between PM and other muscles in the final 50 m.
Subjects made a fast elbow extension movement to designated target in response to a go signal. In 45% of trials a stop signal was presented after the go signal, to which subjects were asked to stop the movement as rapidly as possible. The interstimulus interval (ISI), or time interval between the go and stop signals, was randomly varied between 0 and 200 ms. Electromyographic (EMG) activity was recorded from biceps brachii and triceps brachii. Subjects could sometimes completely inhibit initiation of the movements when the ISI was 0 ms, but could rarely do so when the ISI exceeded 100 ms. For responses that were initiated but stopped on the way, the amplitude of the movement decreased linearly as the time interval (=modification time) from the stop signal to EMG onset increased. The peak velocity increased linearly as the movement amplitude increased. This tendency was similar to those previously reported in step-tracking movements with various amplitudes. In spite of the similarity in the kinematics of the movement, the EMG pattern was different from that of step-tracking movement. While the initial agonist burst (AG1) decreased linearly after the modification time exceeded 100 ms, the antagonist burst (ANT) increased compared with the go trial for the modification time from 0 to 200 ms and decreased after the modification time exceeded 300 ms. This change of activation is analogous to functional modification of middle-latency reflex EMG response to load, or cutaneous perturbation. In conclusion, it is suggested that adaptive mechanisms, which would functionally modify the reflex responses, are also continuously working during voluntary movements in response to sudden changes in environmental information.
This study was designed to determine trial-to-trial and day-to-day reproducibility of isometric force and electromyogram activity (EMG) of the knee extensor muscles in water and on dry land as well as to make comparisons between the two training conditions in muscle activity and force production. A group of 20 healthy subjects (12 women and 8 men) were tested three times over 2 weeks. A measurement session consisted of recordings of maximal and submaximal isometric knee extension force with simultaneous recording of surface EMG from the vastus medialis, vastus lateralis and biceps femoris muscles. To ensure identical measurement conditions the same patient elevator chair was used in both the dry and the wet environment. Intraclass correlation coefficients (ICC) and coefficients of variation (CV) showed high trial-to-trial (ICC = 0.95-0.99, CV = 3.5%-11%) and day-to-day reproducibility (ICC=0.85-0.98, CV=11%-19%) for underwater and dry land measurements of force and EMG in each muscle during maximal contractions. The day-to-day reproducibility for submaximal contractions was similar. The interesting finding was that underwater EMG amplitude decreased significantly in each muscle during maximal (P < 0.01-P < 0.001) and submaximal contractions (P < 0.05-P < 0.001). However, the isometric force measurements showed similar values in both wet and dry conditions. The water had no disturbing effect on the electrodes as shown by slightly lowered interelectrode resistance values, the absence of artefacts and low noise levels of the EMG signals. It was concluded that underwater force and EMG measurements are highly reproducible. The significant decrease of underwater EMG could have electromechanical and/or neurophysiological explanations.
Eight male subjects were asked to swim 25 m at maximal velocity while the use of the arm(s) and legs was alternately restricted. Four situations were examined using one arm (1A), two arms (2A), one arm and two legs (1A2L) and both arms and legs (2A2L, normal swim) for propulsion. A significant mean increase of 10% on maximal velocity was obtained in 1A2L and 2A2L compared to 1A and 2A. A non-significant 4% effect was obtained in 1A. This study focused on the actual contribution of leg kick in the 10% gain in maximal velocity. It was clear that the underwater trajectory of the wrist was modified by the action of the legs (most comparisons P < 0.001). Therefore it was thought that the legs enhanced the generated propulsive force by improving the propulsive action of the arm. The arm action was quantified by selecting typical phases from the filmed trajectory of the wrist, namely forward (F), downwards (D) and backwards (B). Although there was a tendency for individual changes in kinematic parameters (F, D and B) to occur with individual changes in velocity when 2A was compared to 2A2L, no relationship was found between the relative changes in F, D and B and relative changes in velocity. This was illustrated by describing the responses of three individuals who could represent three patterns of contribution by legs and arms to propulsion in high speed swimming.
Theoretical and psychophysical studies have suggested that humans learn to make reaching movements in novel dynamic environments by building specific internal models (IMs). Here we have found electromyographic correlates of internal model formation. We recorded EMG from four muscles as subjects learned to move a manipulandum that created systematic forces (a "force field"). We also simulated a biomechanical controller, which generated movements based on an adaptive IM of the inverse dynamics of the human arm and the manipulandum. The simulation defined two metrics of muscle activation. The first metric measured the component of the EMG of each muscle that counteracted the force field. We found that early in training, the field-appropriate EMG was driven by an error feedback signal. As subjects practiced, the peak of the field-appropriate EMG shifted temporally to earlier in the movement, becoming a feedforward command. The gradual temporal shift suggests that the CNS may use the delayed error-feedback response, which was likely to have been generated through spinal reflex circuits, as a template to learn a predictive feedforward response. The second metric quantified formation of the IM through changes in the directional bias of each muscle's spatial EMG function, i.e., EMG as a function of movement direction. As subjects practiced, co-activation decreased, and the directional bias of each muscle's EMG function gradually rotated by an amount that was specific to the field being learned. This demonstrates that formation of an IM can be represented through rotations in the spatial tuning of muscle EMG functions. Combined with other recent work linking spatial tunings of EMG and motor cortical cells, these results suggest that rotations in motor cortical tuning functions could underlie representation of internal models in the CNS.
This study aimed to evaluate muscle function and kinematics during commonly used knee rehabilitation exercises performed in water.
Maximal effort single extension and flexion trials in still water and repeated extension-flexion trials in flowing water in barefoot condition were analysed from 18 healthy participants (8 men, 10 women).
Despite the fact that water exercises are widely used, there are only few studies involving biomechanical and hydrodynamical analysis of aquatic exercises in rehabilitation.
Electromyography of the quadriceps (vastus medialis, vastus lateralis) and hamstring muscles (biceps femoris, semitendinosus) and angular velocities of the movements were recorded under water.
In the repeated extension-flexion exercises the early reduction of agonist activity occurred concurrently with a high level of activity of the antagonists. In the single trial exercises the level of antagonistic activity was low throughout the range of motion, whereas the level of agonist activity was higher during the final phase of the range of motion as compared with the repeated exercises. Angular velocity patterns and values were similar between the two types of exercises.
The present data demonstrated that the flowing properties of water modified the neuromuscular function of the quadriceps and hamstring muscles acting as agonists and antagonists in the knee flexion-extension exercises.
The purposes of this study were: (1) to provide descriptive temporal and force data for fast alternate tapping by the index and middle fingers ('double-finger mode'), and to compare it with one finger fast tapping ('single-finger mode'); (2) to determine any differences in the dynamic motor function of individual fingers with these tapping tasks; and (3) to determine any differences between the single-finger mode and tapping with the whole hand ('hand mode'). Eleven healthy males tapped force transducer(s) for 7 s as fast as possible using their dominant hand. The double-finger mode had a greater peak force and a 50% faster tapping frequency than the single-finger mode. There was no correlation between the single-finger and double-finger modes in the temporal data. Tapping with two fingers thus seems to be organized with a motor strategy that is different from that with one finger, and can possibly capture an individual's additional or different motor function. A comparison between the two fingers revealed that the index finger had a significantly faster tapping frequency, indicating the superiority of the index finger over the middle finger in terms of dynamic motor function. The hand mode had a significantly faster tapping frequency with greater peak force than the single-finger mode. A distinction is essential between these two modes.
The proximal-to-distal segmental sequence has been identified in many sports activities, including baseball pitching and ball kicking. However, proximal-to-distal sequential muscle activity has not been identified. The aims of this study were to establish whether sequential muscle activity does occur and, if it does, to determine its functional role. We recorded surface electromyograms (EMGs) for 17 muscles from the upper extremity and abdomen during overarm throwing and detected the onset and peak times as indices of muscle activity. The following electromyographic properties were commonly identified in the participants. First, sequential muscle activity was observed from the scapular protractors to the shoulder horizontal flexors and from the shoulder horizontal flexors to the elbow extensor, but not from the elbow extensor to the wrist flexor or forearm pronator. Secondly, the external oblique contralateral to the throwing arm became activated before the ipsilateral external oblique. This sequence is considered to be very effective for the generation of high force and energy in the trunk. Thirdly, the ipsilateral external oblique began its activity almost at foot strike. Finally, the main activity of the rectus abdominis appeared just before the point of release.
We examined the preferred mode of arm coordination in 14 elite male front-crawl swimmers. Each swimmer performed eight successive swim trials in which target velocity increased from the swimmer's usual 3000-m velocity to his maximal velocity. Actual swim velocity, stroke rate, stroke length and the different arm stroke phases were then calculated from video analysis. Arm coordination was quantified by an index of coordination based on the lag time between the propulsive phases of each arm. The index expressed the three coordination modes in the front crawl: opposition, catch-up and superposition. First, in line with the dynamic approach to movement coordination, the index of coordination could be considered as an order parameter that qualitatively captured arm coordination. Second, two coordination modes were observed: a catch-up pattern (index of coordination= -8.43%) consisting of a lag time between the propulsive phases of each arm, and a relative opposition pattern (index of coordination= 0.89%) in which the propulsive phase of one arm ended when the propulsive phase of the other arm began. An abrupt change in the coordination pattern occurred at the critical velocity of 1.8 m. s(-1), which corresponded to the 100-m pace: the swimmers switched from catch-up to relative opposition. This change in coordination resulted in a reorganization of the arm phases: the duration of the entry and catch phase decreased, while the duration of the pull and push phases increased in relation to the whole stroke. Third, these changes were coupled to increased stroke rate and decreased stroke length, indicating that stroke rate, stroke length, the stroke rate/stroke length ratio, as well as velocity, could be considered as control parameters. The control parameters can be manipulated to facilitate the emergence of specific coordination modes, which is highly relevant to training and learning. By adjusting the control and order parameters within the context of a specific race distance, both coach and swimmer will be able to detect the best adapted pattern for a given race pace and follow how arm coordination changes over the course of training.
With the aim of computing a complete energy balance of front crawl, the energy cost per unit distance (C = Ev(-1), where E is the metabolic power and v is the speed) and the overall efficiency (eta(o) = W(tot)/C, where W(tot) is the mechanical work per unit distance) were calculated for subjects swimming with and without fins. In aquatic locomotion W(tot) is given by the sum of: (1) W(int), the internal work, which was calculated from video analysis, (2) W(d), the work to overcome hydrodynamic resistance, which was calculated from measures of active drag, and (3) W(k), calculated from measures of Froude efficiency (eta(F)). In turn, eta(F) = W(d)/(W(d) + W(k)) and was calculated by modelling the arm movement as that of a paddle wheel. When swimming at speeds from 1.0 to 1.4 m s(-1), eta(F) is about 0.5, power to overcome water resistance (active body drag x v) and power to give water kinetic energy increase from 50 to 100 W, and internal mechanical power from 10 to 30 W. In the same range of speeds E increases from 600 to 1,200 W and C from 600 to 800 J m(-1). The use of fins decreases total mechanical power and C by the same amount (10-15%) so that eta(o) (overall efficiency) is the same when swimming with or without fins [0.20 (0.03)]. The values of eta(o) are higher than previously reported for the front crawl, essentially because of the larger values of W(tot) calculated in this study. This is so because the contribution of W(int) to W(tot )was taken into account, and because eta(F) was computed by also taking into account the contribution of the legs to forward propulsion.
The purpose of this study was to establish the characteristics of the movement patterns common to flutter kicking of skilled swimmers and to determine how the movement patterns of swimmers at different levels of a "learn-to-swim" programme differ from those of skilled swimmers. Also, the nature of the skill afforded the opportunity to investigate learning of a cyclical multi-joint task from a motor control perspective. The underwater motion of nine children representing three levels of a "learn-to-swim" programme and 10 skilled swimmers were video-recorded while performing nine cycles of prone flutter kicking. Kinematics including joint angular motion and coordination of joint actions were calculated. Fourier analysis was applied to determine the frequency composition of the vertical undulations of the hip, knee, and ankle and to calculate the velocity of the body wave travelling caudally from hip to ankle. Fourier analysis also enabled investigation of biological noise, as distinct from variability. The results indicated the desired joint angles and coordination towards which learners could be guided. An index based on the ratio of hip - knee and knee - ankle body wave velocities showed that the inter-joint coordination of most learners was not appropriate for effective flutter kicking. There was strong evidence to suggest that skilled performance in flutter kicking is characterized by sequencing of joint actions to produce a single sinusoidal body wave moving caudally with not decreasing and preferably increasing velocity, low biological noise, and small variability.
In this study, we examined Spatial-temporal gait stride parameters, lower extremity joint angles, ground reaction forces (GRF) components, and electromyographic activation patterns of 10 healthy elderly individuals (70+/-6 years) walking in water and on land and compared them to a reference group of 10 younger adults (29+/-6 years). They all walked at self-selected comfortable speeds both on land and while immersed in water at the Xiphoid process level. Concerning the elderly individuals, the main significant differences observed were that they presented shorter stride length, slower speed, lower GRF values, higher horizontal impulses, smaller knee range of motion, lower ankle dorsiflexion, and more knee flexion at the stride's initial contact in water than on land. Concerning the comparison between elderly individuals and adults, elderly individuals walked significantly slower on land than adults but both groups presented the same speed walking in water. In water, elderly individuals presented significantly shorter stride length, lower stride duration, and higher stance period duration than younger adults. That is, elderly individuals' adaptations to walking in water differ from those in the younger age group. This fact should be considered when prescribing rehabilitation or fitness programs for these populations.
The purpose of this study was to compare the cycling technique of triathletes and cyclists on the basis of the cocontraction of selected muscles of the lower limbs and economy at different cadences. The economy (EC) and percent cocontraction from nine triathletes and eight cyclists were compared at 60, 75, 90 and 105 rpm cadences. Tests were performed on two separate days. The maximal oxygen uptake was measured and the second ventilatory threshold (VO(2VT)) was estimated on the first day using a stationary bicycle. On the second day the four different cadences were tested at approximately 5% below the VO(2VT). The EMG activity of the rectus femoris (RF), biceps femoris (BF) and vastus lateralis (VL) was recorded and the EMG signal was normalized using the 60 rpm dynamic contraction. The percent cocontractions were calculated from RF/BF and VL/BF muscles. The EC was also calculated. The results showed that cyclists were significantly more economic, indicating that they exerted more power with less VO(2), and presented significantly lower percent cocontraction than triathletes (p<0.05). Thus, the results suggest that the cyclists had a better technique than the triathletes. The simultaneous use of the percent cocontraction and economy seems to be a good performance indicator for cyclists and triathletes.
This study describes the effect of hand acceleration on hydrodynamic forces acting on the human hand in angular and general motions with variable hand accelerations. Even if accelerations of a swimmer's hand are believed to have an important role in generating hydrodynamic forces on the hand, the effect of accelerations in angular and general motions on hydrodynamic forces on the swimmers hand has not been previously quantified. Understanding how hand acceleration influences force generation can provide useful information to enhance swimming performance. A hand-forearm model attached to a tri-axial load cell was constructed to measure hydrodynamic forces acting only on the hand when the model was rotated and accelerated in a swimming flume. The effect of acceleration on hydrodynamic forces on the hand was described by comparing the difference between accelerating and non-accelerating hands in different flow conditions. Hydrodynamic forces on the accelerating hand varied between 1.9 and 10 times greater than for the non-accelerating hand in angular motion and varied between 1.7 and 25 times greater than for the non-accelerating hand in general motion. These large increases occurred not only during positive acceleration phases but also during negative acceleration phases, and may be due to the added mass effect and a vortex formed on the dorsal side of the hand. This study provides new evidence for enhanced stroke techniques in swimming to generate increased propulsion by changing hand velocity during a stroke.
Propulsion in swimming is achieved by complex sculling movements with elbow quasi-fixed on the antero-posterior axis to transmit forces from the hand and the forearm to the body. The purpose of this study was to investigate how elbow muscle coactivation was influenced by the front crawl stroke phases. Ten international level male swimmers performed a 200-m front crawl race-pace bout. Sagittal views were digitized frame by frame to determine the stroke phases (aquatic elbow flexion and extension, aerial elbow flexion and extension). Surface electromyograms (EMG) of the right biceps brachii and triceps brachii were recorded and processed using the integrated EMG to calculate a coactivation index (CI) for each phase. A significant effect of the phases on the CI was revealed with highest levels of coactivation during the aquatic elbow flexion and the aerial elbow extension. Swimmers stabilize the elbow joint to overcome drag during the aquatic phase, and act as a brake at the end of the recovery to replace the arm for the next stroke. The CI can provide insight into the magnitude of mechanical constraints supported by a given joint, in particular during a complex movement.
In this study, we investigated muscle cocontraction during a street dance movement task to provide evidence that the level of muscle cocontraction is associated with degree of proficiency in whole-body sensorimotor synchronization movement. dancers and nondancers were required to synchronize a knee-bending movement in a standing position to a metronome beat. The dancer group showed significantly smaller variability of temporal deviation (defined as the peak knee-flexion time minus beat onset time), and lower level of muscle cocontraction analyzed by electromyographic data of the agonist and antagonist muscles of the upper and lower leg than did the nondancer group. In addition, multiple regression analyses revealed that the group effect significantly predicted the level of muscle cocontraction. These results show that the level of muscle cocontraction in the lower limbs during whole-body sensorimotor synchronization movement is associated with the degree of proficiency of the movement.
This study attempted to assess and compare the amount of cocontraction present in thigh and leg muscles in three groups of children during treadmill walking and running. Thirty children, aged 7-8 (n = 10), 10-12 (n = 10) and 15-16 (n = 10) years, performed 4-min bouts of submaximal treadmill exercise at two walking and four running speeds, assigned in a randomized order. Three seconds of EMG data were collected during the final minute of each bout from the vastus lateralis (VL), hamstrings (H), tibialis anterior (TA) and soleus (S). The processed linear envelopes of VL and H, and likewise of TA and S, were overlapped and a cocontraction index calculated (area of overlap divided by the number of data points) for thigh and leg segments, respectively. Cocontraction was highest for the youngest children and lowest for the oldest, for both thigh and leg, whether expressed in terms of absolute speed or as a percentage of each child's VO(2 max). Larger amounts of cocontraction may help to explain the higher metabolic cost of locomotion for younger children, when compared with adolescents and adults.
In unstationary swimming (changing velocity), some of the water around the swimmer is set in motion. This can be thought of as an added mass (M(a)) of water. The purpose of this study was to find added mass on human swimmers and investigate the effect of shape and body size. Thirty subjects were connected to a 2.8m long bar with handles, attached with springs (stiffness k = 318 N/m) and a force cell. By oscillating this system vertically and registering the period of oscillations it was possible to find the added mass of the swimmer, given the known masses of the bar and swimmer. Relative added mass (M(a)%) for boys, women and men were, respectively, 26.8 +/- 2.9%, 23.6 +/- 1.6% and 26.8 +/- 2.3% of the subjects total mass. This study reported significantly lower added mass (p < 0.001) and relative added mass (p < 0.002) for women compared to men, which indicate that the possible body shape differences between genders may be an important factor for determining added mass. Boys had significantly lower (p < 0.001) added mass than men. When added mass was scaled for body size there were no significant differences (p = 0.996) between boys and men, which indicated that body size is an important factor that influences added mass. The added mass in this study seems to be lower and within a smaller range than previously reported (Klauck, 1999; Eik et al., 2008). It is concluded that the added mass in human swimmers, in extended gliding position, is approximately 1/4 of the subjects' body mass.
To study elbow muscle load sharing we investigated the effect of external flexion-extension (FE) and pronation-supination (PS) moments and elbow angle on muscle activation and oxygen consumption (V O(2)). Two data sets were obtained. First, (n=6) electromyography (EMG) of elbow flexors (long and short heads of biceps brachii, brachioradialis, brachialis) and extensors (long and short heads of triceps brachii and anconeus) was recorded in all combinations of FE and PS moments at three force levels and four elbow angles (50 degrees , 70 degrees , 90 degrees and 110 degrees ). Second, (n=4) EMG and V O(2) of three muscles (both heads of biceps and lateral head of triceps) were measured simultaneously during a subset of the above conditions. Joint angle and therefore both moment arm and muscle length influenced both EMG amplitude and the load sharing between muscles. The principles behind load sharing, however, were difficult to quantify, since it was impossible to distinguish between all individual aspects that affect muscle activity. We found a linear relationship between EMG and V O(2), while joint angle had no major effect. Although in general subjects showed comparable muscle activation patterns, there were also considerable inter-individual differences, which might be explained by the use of different optimisation strategies or differences in morphology.
The present study investigated a skill-level-dependent interaction between gravity and muscular force when striking piano keys. Kinetic analysis of the arm during the downswing motion performed by expert and novice piano players was made using an inverse dynamic technique. The corresponding activities of the elbow agonist and antagonist muscles were simultaneously recorded using electromyography (EMG). Muscular torque at the elbow joint was computed while excluding the effects of gravitational and motion-dependent interaction torques. During descending the forearm to strike the keys, the experts kept the activation of the triceps (movement agonist) muscle close to the resting level, and decreased anti-gravity activity of the biceps muscle across all loudness levels. This suggested that elbow extension torque was produced by gravity without the contribution of agonist muscular work. For the novices, on the other hand, a distinct activity in the triceps muscle appeared during the middle of the downswing, and its amount and duration were increased with increasing loudness. Therefore, for the novices, agonist muscular force was the predominant contributor to the acceleration of elbow extension during the downswing. We concluded that a balance shift from muscular force dependency to gravity dependency for the generation of a target joint torque occurs with long-term piano training. This shift would support the notion of non-muscular force utilization for improving physiological efficiency of limb movement with respect to the effective use of gravity.
Studies of rapid unimanual tapping have assumed that the human rate limit for voluntary rhythmic movement is 5-7 Hz, which corresponds to an inter-tap interval (ITI) of 150-200ms. In fact, the winner of a recent contest to find the world's fastest drummer (WFD) can perform such movements using a handheld drumstick at 10 Hz, which corresponds to an ITI of 100 ms. Because the contest measured only the number of taps by the WFD, we examined the stability of the ITI and the underlying wrist muscle activity of the WFD. By comparing the performance and wrist muscle activity of the WFD with those of two control groups (non-drummers (NDs) and ordinary skilled drummers (ODs)), we found that the WFD had a relatively stable ITI and more pronounced reciprocal wrist muscle activity during the 10-Hz performance. Our result indicates that very fast, stable tapping performance can be achieved by keeping the wrist joint compliant rather than stiff.
In order to measure active drag during front crawl swimming a system has been designed, built and tested. A tube (23 m long) with grips is fixed under the water surface and the swimmer crawls on this. At one end of the tube, a force transducer is attached to the wall of the swimming pool. It measures the momentary effective propulsive forces of the hands. During the measurements the subjects' legs are fixed together and supported by a buoy. After filtering and digitizing the electrical force signal, the mean propulsive force over one lane at constant speeds (ranging from about 1 to 2 m s-1) was calculated. The regression equation of the force on the speed turned out to be almost quadratic. At a mean speed of 1.55 m s-1 the mean force was 66.3 N. The accuracy of this force measured on one subject at different days was 4.1 N. The observed force, which is equal to the mean drag force, fits remarkably well with passive drag force values as well as with values calculated for propulsive forces during actual swimming reported in the literature. The use of the system does not interfere to any large extent with normal front crawl swimming; this conclusion is based on results of observations of film by skilled swim coaches. It was concluded that the system provides a good method of studying active drag and its relation to anthropometric variables and swimming technique.
Treadmills are often used in research projects to simulate overground locomotion, assuming that locomotion is similar on a treadmill and overground. The purpose of this investigation was to determine whether a treadmill could be used to simulate overground locomotion. Twenty-two subjects ran on four different surfaces: overground and three treadmills that differed in size and power. The kinematics of the right leg and foot were studied using two high-speed Locam cameras (lateral and posterior view). The subjects ran in two different shoes at four different speeds (3.0-6.0 m.s-1). The differences in the kinematics between treadmill and overground running could be divided into systematic and subject dependent components. Subjects systematically planted their feet in a flatter position on the treadmill than overground. Most of the lower extremity kinematic variables, however, showed inconsistent trends for individual subjects, depending on the individual subject's running style, running speed, and shoe/treadmill situation. The differences were substantial. It is not yet understood how the human locomotor system adapts to a particular treadmill running situation. However, it is concluded that individual assessment of running kinematics on a treadmill for shoe or shoe orthotic assessment may possibly lead to inadequate conclusions about overground running.
Little consensus exists in the literature regarding methods for determination of the onset of electromyographic (EMG) activity. The aim of this study was to compare the relative accuracy of a range of computer-based techniques with respect to EMG onset determined visually by an experienced examiner. Twenty-seven methods were compared which varied in terms of EMG processing (low pass filtering at 10, 50 and 500 Hz), threshold value (1, 2 and 3 SD beyond mean of baseline activity) and the number of samples for which the mean must exceed the defined threshold (20, 50 and 100 ms). Three hundred randomly selected trials of a postural task were evaluated using each technique. The visual determination of EMG onset was found to be highly repeatable between days. Linear regression equations were calculated for the values selected by each computer method which indicated that the onset values selected by the majority of the parameter combinations deviated significantly from the visually derived onset values. Several methods accurately selected the time of onset of EMG activity and are recommended for future use.
Treadmills are often used in research to analyse kinematic and physiological variables. The success of transfering the results to overground running depends on the comparability of the values between the two situations. The aim of the present study was to compare the kinematics and muscle activities in overground and treadmill running. Ten male physical education students with experience in treadmill running were asked to run with a speed of 4.0 and 6.0 m/s both overground and on a Woodway treadmill. The 3D-kinematics of the limbs were studied using a two camera video tracking system. Additionally the surface EMG of six lower limb muscles and the pattern of ground contact of the right foot was registered. Both the activities of the leg muscles and several kinematic variables showed systematic changes from overground to treadmill running. On the treadmill the subjects favoured a type of running that provided them with a higher level of security. The swing amplitude of the leg, the vertical displacement and the variance in vertical and horizontal velocity were lower in treadmill running. The angle between shoe sole and ground at foot impact was also lower and the forward lean of the upper body was higher in running on the treadmill compared with the overground mode. Most of the subjects reduced their step length and increased stride frequency in treadmill running. Furthermore, the contact time in treadmill running was shorter than for overground running. The above mentioned kinematic variables were significantly different (p < 0.05). The EMG patterns of the leg muscles were generally similar between overground and treadmill modes, but some minor differences could consistently be identified.
The purposes of this study were to quantify the rotational effect of buoyant force (buoyant torque) during the performance of front crawl and to reexamine the mechanics of horizontal alignment of the swimmers. Three-dimensional videography was used to measure the position and orientation of the body segments of 11 competitive swimmers performing front crawl stroke at a sub-maximum sprinting speed. The dimensions of each body segment were defined mathematically to match the body segment parameters (mass, density, and centroid position) reported in the literature. The buoyant force and torque were computed for every video-field (60fields/s), assuming that the water surface followed a sine curve along the length of the swimmer. The average buoyant torque over the stroke cycle (mean=22Nm) was directed to raise the legs and lower the head, primarily because the recovery arm and a part of the head were lifted out of the water and the center of buoyancy shifted toward the feet. This finding contradicts the prevailing speculation that buoyancy only causes the legs to sink throughout the stroke cycle. On the basis of a theoretical analysis of the results, it is postulated that the buoyant torque, and perhaps the forces generated by kicks, function to counteract the torque generated by the hydrodynamic forces acting on the hands, so as to maintain the horizontal alignment of the body in front crawl.
Electromyograms (EMGs) recorded during head-out immersion have demonstrated reduced signal amplitudes and decreased EMG/force ratios for both maximal and submaximal isometric contractions compared with measurements on dry land. Similar EMG changes have been found in spaceflight. Hypothesis: This study was designed to examine neuromuscular function in the legs during immersion with special reference to reflex sensitivity.
Recordings were made during plantarflexion in air and water. EMGs were recorded from surface and/or internal electrodes on the soleus (SOL) and medial gastrocnemius (MG) muscles during maximal voluntary contraction (MVC). Hoffman and Achilles tendon reflexes were measured during submaximal plantarflexion (50% MVC) in air and water.
During immersion, MVC decreased 13% while EMG amplitude of the plantarflexor muscles decreased by 29% and 35% for SOL and MG, respectively. A similar trend was observed in measurements of Hofman and Achilles tendon reflexes.
Head-out immersion induced a deterioration of neuromuscular function, perhaps by triggering inhibitory mechanisms. The origin of these mechanisms seems to be related mainly to effects of partial weightlessness, but hydrostatic pressure should also be considered.
One defining characteristic of skilled motor performance is the ability to complete the task with minimum energy expenditure. This experiment was designed to examine practice effects on coordination and control, metabolic energy expenditure, and muscle activation. Participants rowed an ergometer at 100 W for ten 16-min sessions. Oxygen consumption and perceived exertion (central and peripheral) declined significantly with practice and movement economy improved (reliably) by 9%. There was an associated but non-significant reduction in heart rate. Stroke rate decreased significantly. Peak forces applied to the ergometer handle were significantly less variable following practice and increased stability of the post-practice movement pattern was also revealed in more tightly clustered plots of hip velocity against horizontal displacement. Over practice trials muscle activation decreased, as revealed in integrated EMG data from the vastus lateralis and biceps brachii, and coherence analysis revealed the muscle activation patterns became more tightly coordinated. The results showed that practice reduced the metabolic energy cost of performance and practice-related refinements to coordination and control were also associated with significant reductions in muscle activation.
This study was designed to describe and clarify muscle activities which occur while walking in water. Surface electromyography (EMG) was used to evaluate muscle activities in six healthy subjects (mean age, 23.3 +/- 1.4 years) while they walked on a treadmill in water (with or without a water current) immersed to the level of the xiphoid process, and while they walked on a treadmill on dry land. The trials in water utilized the Flowmill which has a treadmill at the base of a water flume. Integrated EMG analysis was conducted for the quantification of muscle activities. In order to calculate the %MVC, the measurement of maximal voluntary contraction (MVC) of each muscle was made before the gait analysis, thus facilitating a comparison of muscle activities while walking in water with those on dry land. The %MVCs obtained from each of the tested muscles while walking in water, both with and without a water current, were all found to be lower than those obtained while walking on dry land at a level of heart rate response similar to that used when walking on dry land. Furthermore, the %MVCs while walking in water with a water current tended to be greater when compared to those while walking in water without a water current. In conclusion, the present study demonstrated that muscle activities while walking in water were significantly decreased when compared to muscle activities while walking on dry land, that muscle activities while walking in water tended to be greater with a water current than without, and that the magnitude of the muscle activity in water was relatively small in healthy humans. This information is important to design water-based exercise programs that can be safely applied for rehabilitative and recreational purposes.
Trunk dynamics, including stiffness, mass and damping were quantified during trunk extension exertions with and without voluntary recruitment of antagonistic co-contraction. The objective of this study was to empirically evaluate the influence of co-activation on trunk stiffness. Muscle activity associated with voluntary co-contraction has been shown to increase joint stiffness in the ankle and elbow. Although biomechanical models assume co-active recruitment causes increase trunk stiffness it has never been empirically demonstrated. Small trunk displacements invoked by pseudorandom force disturbances during trunk extension exertions were recorded from 17 subjects at two co-contraction conditions (minimal and maximal voluntary co-contraction recruitment). EMG data were recorded from eight trunk muscles as a baseline measure of co-activation. Increased EMG activity confirms that muscle recruitment patterns were different between the two co-contraction conditions. Trunk stiffness was determined from analyses of impulse response functions (IRFs) of trunk dynamics wherein the kinematics were represented as a second-order behavior. Trunk stiffness increased 37.8% (p < 0.004) from minimal to maximal co-activation. Results support the assumption used in published models of spine biomechanics that recruitment of trunk muscle co-contraction increases trunk stiffness thereby supporting conclusions from those models that co-contraction may contribute to spinal stability.
The aim of this study was to evaluate the stabilisation of the wrist joint and the ad hoc wrist muscles activations during the two principal phases of the freestyle stroke. Seven male international swimmers performed a maximal semi-tethered power test. A swimming ergometer fixed on the start area of the pool was used to collect maximal power. The electromyography signal (EMG) of the right flexor carpi ulnaris (FCU) and extensor carpi ulnaris (ECU) was recorded with surface electrodes and processed using the integrated EMG (IEMG). Frontal and sagittal video views were digitised frame by frame to determine the wrist angle in the sagittal plane and the principal phases of the stroke (insweep, outsweep). Important stabilisation of the wrist and high antagonist muscle activity were observed during the insweep phase due to the great mechanical constraints. In outsweep, less stabilisation and lower antagonist activities were noted. Factors affecting coactivations in elementary movements, e.g. intensity and instability of the load, accuracy and economy of the movement were confirmed in complex aquatic movement.
Movements of the dominant and nondominant hand have been claimed to differ with respect to how they take intersegmental dynamics into account. Consistent with this claim, movements of the dominant hand are hypothesized to better exploit the intrinsic limb dynamics, whereas movements of the nondominant hand are controlled to make the intrinsic dynamics ineffective as far as this is possible. For rapid finger oscillations this hypothesis implies a higher level of co-contractions in the nondominant than in the dominant hand. Replicating previous findings on finger tapping, finger oscillations of the dominant hand were faster and less variable than those of the nondominant hand. More importantly, the variance of the relative difference between myoelectric signals of antagonistic muscles and thus the power of reciprocal myoelectric activity was smaller in the nondominant hand, indicating a relatively higher level of co-contractions than in the dominant hand. In addition, a spectral decomposition of the total power of the relative-difference signal revealed stronger relative power in the frequency band of the finger oscillations in the dominant than in the nondominant hand. These findings are consistent with the hypothesis that for the dominant hand more accurate feedforward control is possible based on a more accurate internal model of limb dynamics.
Roles played by the proximal-to-distal sequencing (PDS) of the multi-joint limb in a relatively slow target-aiming task by the arm were investigated using keystroke motion on the piano. Kinematic recordings were made while experts (N=7) and novices (N=7) of piano players performed an octave keystroke at four linearly-scaled loudness levels with a short tone production (staccato) technique. The temporal relationship of the peak angular velocity at the shoulder, elbow and wrist joints showed a clear PDS organization for the experts, but not for the novices. The result thus confirmed that the PDS occurred in a slow and skilled multi-joint movement. The summation effect of segmental speed in terms of increment of the peak segmental angular velocity was equal for both groups. Similarly, no group difference was found for the total kinetic energy produced by the upper limb during keystroke. The role of the PDS in piano keystroke thus cannot be explained by the exploitation of speed-summation effect and mechanical efficiency. Compared to the novices, the experts had a longer period and a greater magnitude of deceleration at the shoulder and elbow joints while their adjacent distal joints were accelerating. These results indicated that greater inertial forces had been generated to descend the forearm as well as the hand for the experts. A dominant role of the PDS in pianists can therefore be to effectively exploit motion-dependent interaction torques at the forearm and hand, and thereby reducing muscle-dependent torques to make the keystroke more physiologically efficient.
This study sought to determine the characteristics of gait patterns and muscle activity in the lower extremities of elderly women during underwater treadmill walking against water flow. Eight female subjects (61.4+/-3.9 y) performed underwater and land treadmill walking at varying exercise intensities and velocities. During underwater walking (water level at the xiphoid process) using the Flowmill, which has a treadmill at the base of a water flume, the simultaneous belt and water flow velocities were set to 20, 30 and 4 m.min(-1). Land walking velocities were set to 40, 60 and 80 m.min(-1). Oxygen uptake and heart rate were measured during both walking exercises. Maximum and minimum knee joint angles, and mean angular velocities of knee extension and knee flexion in the swing phase were calculated using two-dimensional motion analysis. Electromyograms were recorded using bipolar surface electrodes for five muscles: the tibialis anterior (TA), medial gastrocnemius (MG), vastus medialis (VM), rectus femoris (RF) and biceps femoris (BF). At the same exercise intensity level, cadence was almost half that on land. Step length did not differ significantly because velocity was halved. Compared to land walking, the maximum and minimum knee joint angles were significantly smaller and the mean angular velocity of knee extension was significantly lower. Knee extension in the swing phase was limited by water resistance. While the muscle activity levels of TA, VM and BF were almost the same as during land walking, those of MG and RF were lower. At the same velocity, exercise intensity was significantly higher than during land walking, cadence was significantly lower, and step length significantly larger. The knee joint showed significantly smaller maximum and minimum angles, and the mean angular velocity of knee flexion was significantly larger. The muscle activity levels of TA, VM, and BF increased significantly in comparison with land walking, although those of MG and RF did not significantly differ. Given our findings, it appears that buoyancy, lower cadence, and a moving floor influenced the muscle activity level of MG and RF at the same exercise intensity level and at the same velocity. These results show promise of becoming the basic data of choice for underwater walking exercise prescription.
Quantifying muscle activity during locomotion in water is an emerging area of research. This article discusses the methods for quantifying muscle activity and summarizes key research findings of muscle activity during locomotion in water. The article is focused on comparing muscle activity during locomotion in water and on dry land.