Akito Miura

Coordination modes in sensorimotor synchronization of whole-body movement: a study of street dancers and non-dancers.

This study investigated whole-body sensorimotor synchronization (SMS) in street dancers and non-dancers. Two kinds of knee bending movement in a standing position to a metronome beat were explored in terms of stability under different movement frequencies: down-movement condition (knee flexion on the beat) and up-movement condition (knee extension on the beat). Analyses of phase relation between movement and beat revealed several distinct differences between the down- and up-movement conditions, and between dancers and non-dancers. In both groups under the up-movement condition, deviation from intended phase relation at higher beat rates, and enhanced fluctuations were observed. The deviation from intended phase relation under up-movement condition, and movement fluctuations were greater in non-dancers than in dancers. Moreover, subjective difficulty rating revealed that both groups felt that the up-movement condition was more difficult at higher beat rates. These findings suggest that down and up movements are two distinguishable coordination modes in whole-body coordination, and that street dancers have superior whole-body SMS ability.

Action-perception coordination dynamics of whole-body rhythmic movement in stance: A comparison study of street dancers and non-dancers

This study investigated whether whole-body, rhythmic action-perception coordination in stance is organized in terms of dynamic principles. We observed whether phase transition and hysteresis occur during the execution of dancing movements. Nine skilled street dancers and 9 novice controls performed 2 types of rhythmic knee-bending movements to a metronome beat in the standing position. Participants performed down-on-the-beat (in which knee flexion coincides with the beat) and up-on-the-beat (in which knee extension coincides with the beat), which are both typical components of street dance. All participants were instructed not to intervene in the pattern change. The auditory stimulus beat rate increased or decreased between 60 and 220 beats per minute (bpm) in steps of 20 bpm. We calculated the phase angle of beat time that is superposed on knee movement trajectory on a phase plane. Under the up-on-the-beat condition, phase transition and hysteresis were observed. The bifurcation frequency at which phase transition occurred significantly differed between groups, indicating that dancers were able to perform up-on-the-beat at higher movement frequencies than non-dancers. This suggests that dynamical properties may differ between Dancers and Non-dancers. The present results provide additional evidence that whole-body action-perception pattern formation is governed by general and common dynamical principles.

Electromyographic analysis of lower limbs during baseball batting

Abstract Nakata, H, Miura, A, Yoshie, M, Kanosue, K, and Kudo, K. Electromyographic analysis of lower limbs during baseball batting. J Strength Cond Res 27(5): 1179–1187, 2013—We investigated the muscle activation pattern of lower limbs in baseball batting by recording surface electromyography (sEMG) from 8 muscles, the left and right rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and medial gastrocnemius (MG) muscles. The muscle activities were compared between 10 skilled baseball players and 10 unskilled novices. The batting motion was divided into 7 phases: waiting, shifting body weight, stepping, landing, swing, impact, and follow through. The timing for these phases was analyzed by using a high-speed video camera. The onset latencies of sEMG were significantly earlier in baseball players at the left-RF (p < 0.01), right-BF (p < 0.05), and left-BF (p < 0.01). The peak amplitudes of sEMG activity were greater in skilled players at the right-RF (p < 0.01), right-BF (p < 0.01), left-BF (p < 0.01), left-TA (p < 0.01), right-MG (p < 0.01), and left-MG (p < 0.05). The timing for shifting, stepping, and landing was also significantly earlier in skilled players (p < 0.05, p < 0.01, and p < 0.05, respectively). Our findings suggest that preparations for the swing are made earlier in skilled baseball players who recruit their lower muscles for the swing more effectively than novices.

Finger-to-beat coordination skill of non-dancers, street dancers, and the world champion of a street-dance competition

The coordination of body movements to a musical beat is a common feature of many dance styles. However, the auditory–motor coordination skills of dancers remain largely uninvestigated. The purpose of this study was to examine the auditory–motor coordination skills of non-dancers, street dancers, and the winner of a celebrated international street dance competition, while coordinating their rhythmic finger movements to a beat. The beat rate of a metronome increased from 1.0 to 3.7 Hz. The participants were asked to either flex or extend their index fingers on the beat in each condition. Under the extend-on-the-beat condition, both the dancers and non-dancers showed a spontaneous transition from the extend-on-the-beat to the flex-on-the-beat or to a phase wandering pattern. However, the critical frequency at which the transition occurred was significantly higher in the dancers (3.3 Hz) than in the non-dancers (2.6 Hz). Under the flex-on-the-beat condition, the dancers were able to maintain their coordination pattern more stably at high beat rates compared to the non-dancers. Furthermore, the world champion matched the timing of movement peak velocity to the beat across the different beat rates. This may give a sense of unity between the movement and the beat for the audience because the peak velocity of the rhythmic movement works as a temporal cue for the audiovisual synchrony perception. These results suggest that the skills of accomplished dancers lie in their small finger movements and that the sensorimotor learning of street dance is characterized by a stabilization of the coordination patterns, including the inhibition of an unintentional transition to other coordination patterns.

Motor control of rhythmic dance from a dynamical systems perspective: a review

While dancers and dance educators express great interest in motor control as it relates to rhythmic dance, the subject remains largely uninvestigated. In order to advance our understanding of motor control, a theoretical framework called the dynamical systems approach (DSA) has been used. The DSA was originally developed to describe mathematically the principle of synchronization patterns in nature and their change over time. In recent decades, researchers studying human motor control have attempted to describe the synchronization of rhythmic movement using a DSA. More recently, this approach has been applied specifically to rhythmic dance movements. A series of studies that used the DSA revealed that when people synchronize rhythmic movement of a body part 1. with a different body part, 2. with other peoples movement, or 3. with an auditory beat with some phase differences, unintentional and autonomous entrainment to a specific synchronization pattern occurs. However, through practice dancers are able to overcome such entrainment and dance freely. These findings provide practical suggestions for effective ways of training in dance education. The DSA can potentially be an effective tool for furthering our understanding of the motor control utilized in rhythmic dance.

Modulation of individual auditory-motor coordination dynamics through interpersonal visual coupling

The current study investigated whether visual coupling between two people producing dance-related movements (requiring whole-body auditory-motor coordination) results in interpersonal entrainment and modulates individual auditory-motor coordination dynamics. Paired participants performed two kinds of coordination tasks – either knee flexion or extension repeatedly with metronome beats (Flexion-on-the-beat and Extension-on-the-beat conditions) while standing face-to-face or back-to-back to manipulate visual interaction. The results indicated that the relative phases between paired participants’ movements were closer to 0° and less variable when participants could see each other. In addition, visibility of the partner reduced individual differences in the dynamics of auditory-motor coordination by modulating coordination variability and the frequency of phase transitions from Extension-on-the-beat to Flexion-on-the-beat. Together, these results indicate that visual coupling takes place when paired participants can see each other and leads to interpersonal entrainment during rhythmic auditory-motor coordination, which compensates for individual differences via behavioural assimilation and thus enables individuals to achieve unified and cohesive performances.

Electromyographic activity of lower limbs to stop baseball batting

Abstract Nakata, H, Miura, A, Yoshie, M, and Kudo, K. Electromyographic activity of lower limbs to stop baseball batting. J Strength Cond Res 26(6): 1461–1468, 2012—We investigated the muscle activation pattern of the lower limbs for the stopping motion of baseball batting by recording surface electromyography (EMG) from 8 muscles, the left and right rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and medial gastrocnemius (MG) muscles. First, muscle activities for ‘Swing’ and ‘Stopping’ trials were examined in 10 skilled baseball players and 10 unskilled novices. Second, the characteristics of EMG activities for ‘Stopping’ were compared between the 2 groups. The peak latencies of EMG were significantly shorter in ‘Stopping’ than in ‘Swing’ at the right-TA, left-BF, and left-MG between both groups. The peak amplitudes of EMG activity were significantly larger in ‘Swing’ than in ‘Stopping’ at the right-TA, left-BF, and left-MG in both groups. In addition, the peak amplitudes of EMG activity for ‘Stopping’ were significantly larger in the players than in novices at the right-RF and right-TA. The characteristics of EMG activity clearly differed between ‘Swing’ and ‘Stopping,’ and between baseball players and nonplayers, indicating that evaluating the EMG activity in batting enables the understanding of proficiency. Our findings should help players, novices, and coaches to optimize batting performance.

Interpersonal visual interaction induces local and global stabilisation of rhythmic coordination

Perceptual coupling between people can lead to the spontaneous synchronisation of their rhythmic movements. In the current study, we hypothesised that the sight of a co-actor generates anchoring (local stabilisation around specific spatiotemporal points within movement cycles), and that such anchoring supports the occurrence and stability of spontaneous interpersonal synchronisation (global stabilisation across cycles). To test these hypotheses, we re-examined previously published data from a study where participants were required to perform auditory-motor coordination of whole-body movements with versus without visual contact. Paired participants performed two kinds of coordination task - either knee flexion or extension repeatedly with auditory metronome beats (Flexion-on-the-beat and Extension-on-the-beat conditions) while standing face-to-face or back-to-back to manipulate visual interaction. The analysis of individual movement trajectories showed that visual interaction led to decreased variability along the entire trajectory, except the maximum extension position. The results also indicated that the strength of this anchoring was correlated with the degree to which the variability of interpersonal phase relations decreased with visual coupling, suggesting that local stabilisation supported global interpersonal stabilisation. Therefore, the sight of a co-actor generates anchoring effects that may play a crucial role in the stabilisation of spontaneous interpersonal synchronisation.

Differences in the Head Movement During Baseball Batting between Skilled Players and Novices

Abstract Nakata, H, Miura, A, Yoshie, M, and Kudo, K. Differences in the head movement during baseball batting between skilled players and novices. J Strength Cond Res 26(10): 2632–2640, 2012–We investigated the pattern of head movement during baseball batting in 8 skilled players and 9 unskilled novices, using a high-speed video camera. The 2 directions of head movement were analyzed as an X-axis (from the home plate to the pitchers plate) and Z-axis (vertical downward). On the X-axis, peak latency, peak value, the distance from the peak to the value at bat-ball impact, and data variability were compared between the 2 groups. On the Z-axis, peak latency, downward distance, and data variability were analyzed. Peak latency on the X-axis occurred significantly earlier in baseball players than in novices (p < 0.001), and the difference between the minimum peak and impact was significantly larger in the players (p < 0.05). The variability in peak latency on the X-axis was significantly larger in the novices (p < 0.05). The variability in peak value on the Z-axis was also significantly larger in the novices (p < 0.05). Our findings showed that the significant differences in head movement between the 2 groups should help baseball players, beginners, coaches, and strength and conditioning professionals to improve performance, be effectively applied to actual practice, and enhance coaching for batting.

Upper rate limits for one-to-one auditory–motor coordination involving whole-body oscillation: a study of street dancers and non-dancers

ABSTRACT The capacity for auditory–motor coordination (AMC) is shared by several species, among which humans are most flexible in coordinating with tempo changes. We investigated how humans lose this tempo flexibility at their upper rate limit, and the effect of skill level on this phenomenon. Seven skilled street dancers, including a world champion, and 10 non-dancers were instructed to bend their knees according to a metronome beat in a standing position at eight constant beat frequencies (3.8–5 Hz). Although maximum frequency of movement during the task was 4.8 Hz in the non-dancers and 5.0 Hz in the dancers, the rate limit for AMC was 4.1 Hz in the non-dancers and 4.9 Hz in the dancers. These results suggest that the loss of AMC was not due to rate limit of movement execution but rather to a constraint on the AMC process. In addition, mediation analysis revealed that a kinematic bias (i.e. the extent of knee flexion during the task) causally affected the extent of phase wandering via mediating factors (e.g. the extent to which movement frequency was reduced relative to the beat frequency). These results add evidence that gravity acts as constraint on AMC involving vertical rhythmic movement. Summary: Upper rate limits for one-to-one auditory–motor coordination do not occur because of a bottleneck of perceptual and biomechanical rate limits but as a result of constraints on the coordination process.