The purpose of the present study was to examine whether the fixation distance in real three-dimensional space affects manual reaction time to peripheral visual stimuli. Light-emitting diodes were used for presenting a fixation point and four peripheral visual stimuli. The visual stimuli were located at a distance of 45cm and at 25° in the left, right, upper, and lower directions from the sagittal axis including the fixation point. Near (30cm), Middle (45cm), Far (90cm), and Very Far (300cm) fixation distance conditions were used. When one of the four visual stimuli was randomly illuminated, the participants released a button as quickly as possible. Results showed that overall peripheral reaction time decreased as the fixation distance increased. The significant interaction between fixation distance and stimulus location indicated that the effect of fixation distance on reaction time was observed at the left, right, and upper locations but not at the lower location. These results suggest that fixating at far distance would contribute to faster reaction and that the effect is specific to locations in the peripheral visual field. The present findings are discussed in terms of viewer-centered representation, the focus of attention in depth, and visual field asymmetry related to neurological and psychological aspects.

According to recent motor control studies, it is important to know probabilistic structure of his/her own motor errors to choose an optimal motor plan (i.e., where you aim at) to maximise the expected gain. In this study, we questioned if pitching form determines the probabilistic structure of pitching errors in baseball pitchers. Eighteen collegiate baseball pitchers with various pitching forms including right-and left-handed overarm, sidearm and underarm throwers threw 100 pitches aiming at a target located 90 cm above the ground. Two dimensional distribution of pitch location was fitted by using bivariate normal distribution and 95% confidence ellipse was calculated. In order to quantify the pitching form, the direction of the throwing arm trajectory in frontal plane was calculated. The direction of the long axis was dependent on each participant's pitching form (e.g., right overarm pitchers pitched along a right-up-left-down ellipse and left overarm pitchers pitched along a left-up-right-down ellipse). This was confirmed by circular correlation analysis (P = 0.98). These results suggest that different mechanisms, potentially errors in pitching mechanics and errors in ball release timing, might contribute to errors along the long axis and those along the short axis.

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.

The aim of this study was to examine whether the intracyclic velocity variation (IVV) was lower in elite swimmers than in beginner swimmers at various velocities, and whether differences may be related to arm coordination. Seven elite and nine beginner male swimmers swam front crawl at four different swimming velocities (maximal velocity, 75%, 85%, and 95% of maximal swimming velocity). The index of arm coordination (IDC) was calculated as the lag time between the propulsive phases of each arm. IVV was determined from the coefficient of variation of horizontal velocity within one stroke cycle. IVV for elite swimmers was significantly lower (26%) than that for beginner swimmers at all swimming velocities (p< 0.01, 7.28 1.25% vs. 9.80 1.70%, respectively). In contrast, the IDC was similar between elite and beginner swimmers. These data suggest that IVV is a strong predictor of the skill level for front crawl, and that elite swimmers have techniques to decrease IVV. However, the IDC does not contribute to IVV differences between elite and beginner swimmers.

We previously estimated the timing when ball game defenders detect relevant information through visual input for reacting to an attacker's running direction after a cutting manoeuvre, called cue timing. The purpose of this study was to investigate what specific information is relevant for defenders, and how defenders process this information to decide on their opponents' running direction. In this study, we hypothesised that defenders extract information regarding the position and velocity of the attackers' centre of mass (CoM) and the contact foot. We used a model which simulates the future trajectory of the opponent's CoM based upon an inverted pendulum movement. The hypothesis was tested by comparing observed defender's cue timing, model-estimated cue timing using the inverted pendulum model (IPM cue timing) and cue timing using only the current CoM position (CoM cue timing). The IPM cue timing was defined as the time when the simulated pendulum falls leftward or rightward given the initial values for position and velocity of the CoM and the contact foot at the time. The model-estimated IPM cue timing and the empirically observed defender's cue timing were comparable in median value and were significantly correlated, whereas the CoM cue timing was significantly more delayed than the IPM and the defender's cue timings. Based on these results, we discuss the possibility that defenders may be able to anticipate the future direction of an attacker by forwardly simulating inverted pendulum movement.

Physical activity level (PAL) is associated with all-cause mortality in the elderly. However, few studies have attempted to clarify the relationship between lifestyle and PAL in the elderly. This study aimed to examine the determinants of PAL in the elderly in terms of behavioral patterns and exercise intensity, and to validate the simplified physical activity record (sPAR).

The purpose of this study is to examine the characteristics of gait patterns in human preferred sideways locomotion at increasing speeds. Fifteen healthy young males were asked to step sideways on a treadmill at various speeds of 1.3-6.1 km/h. The times of foot contact and take-off were analyzed. Three gait patterns were observed. At slow speeds, all of the subjects performed a walk-like pattern. When the treadmill speed exceeded approximately 3.5 km/h, the subjects preferred gait patterns with a flight phase. Most of the subjects performed an asymmetric gait pattern that was similar to a forward gallop, whereas only two out of fifteen subjects performed a run-like gait pattern. Because the left and right legs are positioned along the movement direction, it might be more efficient to divide roles between the leading and trailing limbs at high speeds: the leading limb functions to produces breaking and vertical force, and the trailing limb mainly absorbs the impact of foot contact and generates propulsive forces.

The purpose of the present study was to examine the timing for the detection of relevant information in the final running direction of attackers' cutting manoeuvres. Skilled basketball players and novices performed sidestep and reach tasks in response to a ready-go choice stimuli using light-emitting diode (LED) task and video stimuli (video task) wherein skilled ball players executed cutting manoeuvres. The time at which the defenders first obtained relevant visual information was estimated by subtracting the visuo-motor processing time, acquired from the reaction time in the LED task, from the reaction time in the video task. Skilled basketball players reacted to and reached towards the target faster than novices, whereas the estimated video cue timings for the skilled players were not different from those for the novices. The results suggest that the anticipation of attacker's direction in this task would be a general visuo-motor skill, even without previous specialised perceptual training. Combined with the results from the reaction performance in the video task, we conclude that novices are afforded shorter times and more uncertain information before their stepping when they are in a one-on-one ballgame defensive scenario because their sidestepping takes a relatively long time.

The aim of this study was to evaluate and quantify differences in muscle distribution in athletes of various ball sports using segmental bioelectrical impedance analysis (SBIA). Participants were 115 male collegiate athletes from four ball sports (baseball, soccer, tennis, and lacrosse). Percent body fat (%BF) and lean body mass were measured, and SBIA was used to measure segmental muscle volume (MV) in bilateral upper arms, forearms, thighs, and lower legs. We calculated the MV ratios of dominant to nondominant, proximal to distal, and upper to lower limbs. The measurements consisted of a total of 31 variables. Cluster and factor analyses were applied to identify redundant variables. The muscle distribution was significantly different among groups, but the %BF was not. The classification procedures of the discriminant analysis could correctly distinguish 84.3% of the athletes. These results suggest that collegiate ball game athletes have adapted their physique to their sport movements very well, and the SBIA, which is an affordable, noninvasive, easy-to-operate, and fast alternative method in the field, can distinguish ball game athletes according to their specific muscle distribution within a 5-minute measurement. The SBIA could be a useful, affordable, and fast tool for identifying talents for specific sports.

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.

Background: Little is known about hip joint stiffness during walking (dynamic joint stiffness) and the effect of hip impairments on biomechanical alterations of other joints in patients with total hip arthroplasty.Methods: Twenty-four patients (mean age 61.7 years) who underwent unilateral (n = 12) or bilateral total hip arthroplasty (n = 12) and healthy subjects (n = 12) were recruited. In addition to kinematic and kinetic variables, dynamic hip joint stiffness which was calculated as an angular coefficient of linear regression of the plot of the hip flexion moment vs. hip extension angle during the late stance of gait, was measured. Group differences were compared using one-way ANOVA and Tukey's post-hoc test, and relationships between primary hip impairments and secondary gait impairments were found using partial correlation coefficients adjusted for gait speed and stride length.Findings: Dynamic hip joint stiffness was 47% higher on the side with the more pronounced limp in patients with bilateral arthroplasty than in healthy controls. In the same patients, increased dynamic hip joint stiffness was significantly associated especially with increased ankle plantarflexion moment on the ipsilateral side. In patients with unilateral arthroplasty, decreased hip power was significantly related to increased ankle plantarflexor power, only on the non-operated side.Interpretation: We found that dynamic hip joint stiffness was an important factor in assessing relationships between hip impairments and dynamics in other joints, especially in patients with bilateral total hip arthroplasty. The effects of altering hip joint stiffness on gait biomechanics need to be explored. (C) 2011 Elsevier Ltd. All rights reserved.

Human locomotion is not only forward and backward, we can move sideward as well. Different from forward locomotion, an asymmetric gait pattern was sometimes preferred in side stepping, however, no studies have investigated human sideward locomotion. PURPOSE: To clarify the sideward gait pattern on a treadmill. METHODS: Six male participants were asked to step sideward on a treadmill. The treadmill speed was increased between 1.3 and 6.1 km/h in 0.3 km/h steps of 20s duration each. Participants performed three trials. Participants were instructed to use their preferred gait patterns at all times, and not to cross each foot. No feedback was given on time and speed. Foot contact and take-off timings were visually inspected by using a 300-fps video camera. P1 and P2 were proportions of double support or flight phase (P1: proportion of the time from the trailing foot contact to the leading take-off, P2: proportion of the time from the leading foot contact to the trailing take-off) to the entire stride period. Relative phase was an index of gait symmetry defined as the time from the trailing foot contact to the leading foot contact relative to the entire stride period. RESULTS: A walk-like gait pattern with double support (positive P1 and P2) and symmetric foot contact (relative phase: 0.52±0.03 at 2.2 km/h) was observed in all the participants for the treadmill speed of ∼3.5±0.5km/h (mean±SD). As the treadmill speed increased, five of the six participants showed an asymmetric gallop-like gait pattern. For example, P1 and P2 and relative phase were -0.16±0.03, 0.15±0.01 and 0.35±0.01 at 6.1km/h. On the other hand, over 4.0±0.2km/h the other one showed a symmetric run-like gait pattern. For example, P1 and P2 and relative phase were -0.21±0.01, -0.11±0.01 and 0.46±0.01 at 6.1km/h. CONCLUSIONS: In five out of the six participants, an asymmetric gait pattern was observed and similar to galloping, which is naturally used by quadrupeds at high speeds. Because of the restricted lateral range of motion of the hip and knee joint, the roles of accelerating and decelerating the center of mass might have to be distributed into the trailing and leading limbs, which results in the observed gallop-like asymmetric sideward locomotion.

Patients with hip osteoarthritis (OA) have difficulty with mediolateral postural control. Since the symptom of hip OA includes joint pain, which mostly occurs upon initial movement, patients with hip OA might have disabling problems with movement initiation. This study aimed to identify the movement strategy during the anticipatory postural adjustments in the lateral step motion in patients with hip OA. We studied 18 female subjects with unilateral hip OA and 10 healthy subjects, and measured temporal, kinetic, and kinematic variables. Patients with hip OA required a longer duration of anticipation phase than the control subjects, the total duration of lateral stepping was not different between the groups. Displacement of the center of mass to the supporting (affected) side during the anticipation phase was not different between the two groups. These findings suggest that, in patients with hip OA, the center of mass slowly moved to the affected side. Furthermore, patients with hip OA showed greater shift of the trunk to the supporting side than did the control subjects. These movement characteristics might contribute to the achievement of both protection of the affected hip joint and quickness in the subsequent lateral step in patients with hip OA.

the present study examined the synchronization error (SE) of drum kit playing by professional drummers with an auditory metronome, focusing on the effects of motor effectors and tempi. Fifteen professional drummers attempted to synchronize a basic drumming pattern with a metronome as precisely as possible at tempi of 60, 120, and 200 beats per minute (bpm). In the 60 and 120 bpm conditions, the right hand (high-hat cymbals) showed small mean SE (∼2 ms), whereas the left hand (snare drum) and right foot (bass drum) preceded the metronome by about 10 ms. In the 200 bpm condition, the right hand was delayed by about 10 ms relative to the metronome, whereas the left hand and right foot showed small SE (∼1 ms). The absolute values of SE were smaller than those reported in previous tapping studies. In addition, the time series of SE were significantly correlated across the motor effectors, suggesting that each limb synchronized in relation to the other limbs rather than independently with the metronome.

Residual hip impairments, such as decreased hip muscle moment and power during walking, have been reported in patients with total hip arthroplasty (THA). Meanwhile, greater ankle power has also been reported in these patients. We investigated the interaction between hip and ankle joints during walking to determine the effects of different ankle pushoff instructions on hip biomechanics in patients with THA. Twenty-four women (age, 60.8±5.5 years) were randomly assigned to walking exercise groups with either decreased pushoff or increased pushoff. Patients in the decreased pushoff group and increased pushoff group were given the instructions “push less with your foot when you walk” and “push more with your foot when you walk,” respectively. Exercises lasted approximately 10–15min. A series of gait-related parameters were analyzed during pre-exercise, exercise, and post-exercise session. In the decreased ankle pushoff group, hip flexor power absorption and hip/ankle power ratio were higher during post-exercise than during pre-exercise. An increase in hip power from −9.8% to 32.1% was identified. The effect of increase in the hip power by the decreasing ankle pushoff was higher in the patients with greater ankle pushoff in their natural gaits. The patients in the increased ankle pushoff group showed decreased hip flexion angle and hip muscle moment and power after the walking exercise, although ankle pushoff was not increased. Walking exercise with decreased ankle pushoff may help improve the distribution of muscle power between hip flexors and ankle plantarflexors during walking in patients with THA.

This study aimed to investigate attentional demand during single-leg landing after a jump. The experiment was set up as dual-task test. Twelve healthy male participants were instructed to make a two-leg jump with right-leg landing as softly as possible. The flight time of the jump was set to 300ms through sufficient practice. As a cognitive task, the participants were asked to push the right or left custom-made button as soon as a go-signal was presented. The timing when the go-signal presented varied from 0 to 300ms from the take-off. Catch trials in which the go-signal was not presented were randomly inserted. The results showed that the maximum vertical ground reaction force after touchdown was greater under the dual-task condition than in the single-task condition. Increase in the maximum vertical ground reaction force was consistent regardless of the timing of presenting the go-signal, and the same effect was observed in the catch trials. These results indicate that the effect of dual tasking was caused by attentional allocation to the choice reaction time task. Athletes may be exposed a large ground reaction forces during landing while performing cognitive tasks.

PURPOSE: Muscle tissue contains a large part of water in the body. Thus, it will be important to measure not only total muscle volume, but also muscle cell component or volumes of intra-cellular water volume (ICW) and extra-cellular water volume (ECW). The purposes of this study were 1) to examine how ICW and ECW in the upper and lower leg change with age and mobility disability, comparing the healthy younger- and older-old elderly and the mobility-disability elderly, and 2) to identify whether ICW, and ECW/ICW in the muscles of the lower extremities could discriminate the mobility ability independently of muscle strength. METHODS: A total of 287 elderly (57-96 yr, 93 men and 194 women; including 58 subjects using ambulatory day-care service in the public Long-Term Care insurance system participated in the study. The regional muscle mass, ICW, and ECW in the upper and lower leg were estimated using segmental multi-frequency bioelectrical impedance spectroscopy (segmental BIS). The regional muscle mass, ICW, and ECW were calculated only from the resistances of segmental BIS and the length. Habitual and maximal gait speeds, chair-stand (sit-to-stand) frequency, maximal stepping rate, and maximal isometric knee extension strength were measured. Three-way (group × gender × region) ANOVAs, structural equation modeling (SEM), receiver operator characteristic (ROC) analysis, and multiple stepwise regression analysis were applied. RESULTS: ICW were significantly decreased with aging and mobility disability (p<.001). On the contrary, ECW were significantly increased in the lower leg (p<.01), but not significantly changed in the upper leg (p =.14). In the final SEM model, the ECW/ICW was significantly related to the performance score of mobility ability in the lower limbs. In the regression analysis, ICW and ECW/ICW were significantly selected as independent factors to predict gait speed and the frailty of muscle strength (p<.001). The contribution rate of the resistance parameters of the segmental BIS showed no differences from muscle strength. CONCLUSIONS: The results suggested that the expansion ratio of the ECW masks actual muscle cell atrophy in the elderly. Muscle mass and quality assessed using segmental BIS will be effective to monitor the nutrition status and physical functions in the elderly.