Objective Assessment of Physical Activity at Home Using a Novel Floor-Vibration Monitoring System: Validation and Comparison With Wearable Activity Trackers and Indirect Calorimetry Measurements.

BACKGROUND: The self-monitoring of physical activity is an effective strategy for promoting active lifestyles. However, accurately assessing physical activity remains challenging in certain situations. This study evaluates a novel floor-vibration monitoring system to quantify housework-related physical activity. OBJECTIVE: This study aims to assess the validity of step-count and physical behavior intensity predictions of a novel floor-vibration monitoring system in comparison with the actual number of steps and indirect calorimetry measurements. The accuracy of the predictions is also compared with that of research-grade devices (ActiGraph GT9X). METHODS: The Ocha-House, located in Tokyo, serves as an independent experimental facility equipped with high-sensitivity accelerometers installed on the floor to monitor vibrations. Dedicated data processing software was developed to analyze floor-vibration signals and calculate 3 quantitative indices: floor-vibration quantity, step count, and moving distance. In total, 10 participants performed 4 different housework-related activities, wearing ActiGraph GT9X monitors on both the waist and wrist for 6 minutes each. Concurrently, floor-vibration data were collected, and the energy expenditure was measured using the Douglas bag method to determine the actual intensity of activities. RESULTS: Significant correlations (P<.001) were found between the quantity of floor vibrations, the estimated step count, the estimated moving distance, and the actual activity intensities. The step-count parameter extracted from the floor-vibration signal emerged as the most robust predictor (r2=0.82; P<.001). Multiple regression models incorporating several floor-vibration-extracted parameters showed a strong association with actual activity intensities (r2=0.88; P<.001). Both the step-count and intensity predictions made by the floor-vibration monitoring system exhibited greater accuracy than those of the ActiGraph monitor. CONCLUSIONS: Floor-vibration monitoring systems seem able to produce valid quantitative assessments of physical activity for selected housework-related activities. In the future, connected smart home systems that integrate this type of technology could be used to perform continuous and accurate evaluations of physical behaviors throughout the day.

Laterality in Body Coordination of Professional and Amateur Ballet Dancers While Performing a Single Pirouette with Pointe Shoes.

OBJECTIVE: Imbalances in muscle strength coordination owing to lateral preference may be a risk factor for injury in dancers. Postural control is essential for the basic turn in ballet (pirouette), owing to its lateral asymmetry. Since dance with pointe shoes demands greater range of motion, muscle strength, and balance control compared to dancing with flat shoes, pointe shoes may further add to the risk and cause an imbalance between the preferred and non-preferred legs during pirouette. In this study, we examined lateral differences in professional and experienced amateur ballet dancers during single pirouettes with pointe shoes to understand the multiple elements involved in lateral balance control in pirouettes. METHODS: Eight female professionals and seven female amateur ballet dancers performed single pirouettes in pointe shoes on both the preferred and non-preferred sides. To understand the body coordination laterality in single pirouettes, statistical parametric mapping was performed for the trunk, hip, knee, ankle angle, and center of mass-center of pressure inclination angle timeframe data during the pirouette in three phases: turn with double-leg (Phase 1), single-leg (Phase 2), and finish turning with a single-leg (Phase 3). In addition, the hop-up time was calculated as the percentage when the foot is not in contact with the ground in Phases 2 and 3. RESULTS: There were no lateral differences in trunk and lower limb angles in either group. Professional dancers showed slightly more inclination towards the stance leg during left rotation at the beginning of the movement (Phase 1) with longer hop-up time in Phase 2, whereas amateur dancers tended to tilt forward during the left turn (Phases 1 and 2) with longer hop-up time in Phase 3. CONCLUSION: It is notable that the COP-COM inclination angle was adjusted by hop-up and it caused the lateral differences in both professional and amateur dancers during a single pirouette with pointe shoes. This study highlights elements to consider in laterality when monitoring pirouette performance with pointe shoes.

Differences in the Rotation Axis Between Professional and Experienced Amateur Ballet Dancers During pirouette en dehour in Classical Ballet With Wearing Pointe Shoes: A Pilot Study.

Introduction: En pointe, in which weight is placed on the tiptoes, is a fundamental practice for female ballet dancers with pointe shoes. The center of mass (COM) is maintained over the base of support and the relative position of COM to the center of pressure (COP) is especially important when conducting a pirouette in ballet. A pirouette is a fundamental turn in classical ballet with flat shoes and pointe shoes. The investigation of the turn with pointe shoes would be favorable for understanding the movement with limited base of support. Herein, we aimed to determine the differences in the ability to perform pirouettes with pointe shoes between professional and amateur ballet dancers. Methods: This study included 8 professional and 9 amateur ballet dancers. The dancers performed a single pirouette, and the movement was captured and analyzed in 3 phases: turning with double-leg support (TDS), turning with single-leg support in pre-swing (TSSp), and turning with single-leg support in mid-swing (TSSm). The analysis focused on the inclination between the vertical angle and the COP-COM line, the vertical maximum reaction force, and the jump-up time in each phase. Results: The results showed no significant differences between the TDS and TSSp. However, professional ballet dancers exhibited significantly lesser posterior inclinations (professional; 2.05° ± 0.90°, amateur; 3.88° ± 1.67°) and jump-up time (professional; 0%, amateur; 1.4% ± 1.3%) than amateur dancers during TSSm. Conclusion: Overall, the findings suggest that professional dancers exhibit superior control skills regarding the COP-COM line than amateur dancers during TSSm. These results may be attributed to the fact that professional dancers can maintain the COM as close to the upright as on the COP without jumping during TSSm. This enables professional dancers to conduct the movements esthetically and continue on to the other movements in the dance phase.

Differences in Center of Pressure Displacement and Lower Limb Muscle Activity During Relevé Descending Phase Comparing Flat Shoes and Pointe Shoes.

AIMS: In classical ballet, dancers may wear flat shoes and pointe shoes. To consider the kinematic changes between flat shoes and pointe shoes to prevent injuries, it is essential to focus on the fundamental ballet movement of standing on pointe. This study aimed to clarify the differences in the center of pressure (COP) displacement and lower limb muscle activity during the descending phase of a relevé when wearing pointe shoes versus flat shoes. METHODS: Ten amateur ballet dancers volunteered for this study and performed a reléve wearing flat shoes and pointe shoes. We measured the COP displacement by using a footplate and electromyographies of the tibialis anterior, soleus, lateral gastrocnemius, and peroneus longus muscles during the relevé descending phase. These data were compared using a paired t-test or Wilcoxon signed-rank sum test. RESULTS: The COP significantly shifted to the lateral side when dancers were wearing pointe shoes compared to wearing flat shoes (p<0.05). The muscle activity of the tibialis anterior and soleus muscles was significantly higher by 5.7% and 5.3%, respectively, when ballet dancers were wearing pointe shoes compared to flat shoes (p<0.05). However, there were no differences in both lateral gastrocnemius and peroneus longus. CONCLUSION: Greater muscle activities in the tibialis anterior and soleus muscles when wearing pointe shoes than when wearing flat shoes were associated with a larger lateral displacement of the COP. To control the COP displacement during the descending phase of a relevé, the muscle activity of the peroneus longus, which is antagonist of tibialis anterior muscle, and soleus muscles should be increased.

Rotational Movement of the Upper Limbs Associated with the Aesthetic Appreciation of Ballet.

OBJECTIVE: This study aimed to identify the structure of upper limb movements in ballet dancers that affect the audience's perception of the aesthetics and to examine if upper limb rotational movement is a factor contributing to the aesthetics of ballet. METHODS: This study comprised 3-dimensional movement analysis and subjective evaluation of 12 female ballet dancers. Thirty-three reflective markers were affixed to their bodies. Their upper limb movements, which are bodily expressions mimicking a swan's flapping movement, were captured and viewed by 34 observers with previous ballet experience (i.e., university students majoring in dance education). The joint angle and velocity of each body part were calculated from the coordinates of the markers. The observers subjectively evaluated the videos through four pairs of categories: "beautiful-ugly," "like-dislike," "interesting-not interesting," and "good-bad," on a five-point semantic differential scale. Two groups were extracted based on the "beautiful-ugly" rating and compared using an independent t-test. An exploratory factor analysis was performed on the kinematic parameters that showed significant differences. RESULTS: Five factors were identified: amplitude of rotational movement, speed of upward arm movement, amplitude of movement in the distal upper limbs, apparent speed of the downward arm movement, and speed of the internal rotation movement. CONCLUSION: The results sup¬ported the hypothesis that rotational movement of the upper limbs is a factor contributing to the aesthetics of upper limb movements in ballet and will be useful for understanding the intrinsic aesthetics of upper limb movements in ballet.

Both Upper and Lower Limb Movements Contribute to Aesthetics of the Piqué Arabesque in Ballet.

This study aimed to identify the factor structures-which are the predominant frameworks for describing the basic dimensions of a concept-that contribute to the aesthetics of body position in ballet. This study was composed of three-dimensional movement analysis and subjective evaluation. Fourteen ballet dancers participated in the three-dimensional movement analysis. Thirty-six reflective markers were attached to the dancers' bodies, after which the dancers performed a piqué arabesque, a position in which the weight transfers from one leg to the other. This movement was captured using eight optical cameras and one video camera. Biomechanical parameters, such as the joint angle and velocity of each body part, were calculated from the coordinates of the markers. Twenty-eight videos recorded in the three-dimensional movement analysis were viewed by 51 observers with ballet experience. The observers subjectively evaluated the videos through four category pairs-"beautiful-ugly," "like-dislike," "interesting-not interesting," and "good-bad"-on a five-point semantic differential scale. Two groups, the top and bottom 30%, were extracted based on the "beautiful-ugly" rating and compared using an independent t-test. In addition, exploratory factor analysis was performed on the biomechanical parameters that showed significant differences. Five factors were identified: "stability of the right distal upper limb and upper body," "torso displacement speed," "stability of the left distal upper limb and line of the support leg," "height of the gesture leg," and "stability of the support leg around the hip joint and line of the limbs on the gesture leg side." These results indicate that the movements of both upper and lower limbs contributed to the aesthetics of the ballet position of piqué arabesque. These findings will be useful for ballet teachers and dancers to understand the intrinsic aesthetics of movements.

Intra- and Inter-individual Movement Variability of Upper Limb Movements of Ballet Dancers.

OBJECTIVE: This study examined intra- and inter-individual variability in upper limb movements of ballet dancers when performing flapping swan-wing movements, and it assessed differences in joint angles of upper limbs between dancers of different skill levels. METHODS: 23 female ballet dancers (3 professional, 6 advanced, and 14 intermediate dancers) and 21 age-matched females without previous dance experience participated in this study. Thirty-three reflective markers were attached to each participant's trunk and upper limbs, and the flapping upper limb motions from Swan Lake were subsequently captured with eight optical cameras. Peak values of upper limb joint angles (shoulder, elbow, and wrist joint) were obtained, and intra- and inter-individual movement variability of each joint angle were compared between groups. RESULTS: In joint angles of the shoulder, elbow, and wrist, there were few differences among professional, advanced, and intermediate groups. The intra-individual movement variability in upward arm movements was significantly larger for professional and control groups than for advanced and intermediate groups, while in downward arm movement, variability became significantly smaller as technical level increased. Moreover, inter-individual movement variability was larger in the upward arm movement as technical level increased, and smaller in the downward arm movement for the professional group. The results suggested that the upward arm movements reflect dancers' individual expression, while the downward arm movements reflect their technical competence at this swan-like movement. CONCLUSION: The complicated swan-like movements performed by skilled dancers in this study indicate that they execute expressive and technical components in sequence.

On the skilled plantar flexor motor action and unique electromyographic activity of ballet dancers.

The study aimed to compare the ability of dance and non-dance subjects to perform fine control of a simple heel-raising/lowering movement, and to determine if there are any differences in motor unit activity in the primary plantar flexor muscles during the movement. Subjects were instructed to accurately track a sinusoidal trace with a heel-raising and lowering movement at four controlled frequencies (1, 0.5, 0.25, and 0.125 Hz). The ankle joint angle was used to characterize movement errors from the target. Surface electromyography was recorded from the soleus and medial gastrocnemius muscles. One trial including five sinusoidal traces was divided into two phases: an up phase and a down phase. To characterize motor unit activity of the plantar flexor muscles, a wavelet transform was applied to electromyographic signals recorded in each phase. For both phases, errors in movement accuracy were lower in dancers than in controls (8.7 ± 4.6 vs. 11.5 ± 6.8%, P < 0.05) regardless of the frequency of the sinusoidal wave traced. During the down phase, peak power of soleus electromyographic signals at ~ 10 Hz was statistically larger in control subjects than in dancers (10.4 ± 0.7 vs. 6.3 ± 0.4% total power, P < 0.05). These results indicate that dancers have a higher degree of motor skill in a heel raise tracking task and exhibit adaptations in the motor unit activity during skilled dynamic movements.

Gender differences in muscle blood volume reduction in the tibialis anterior muscle during passive plantarflexion.

Physical flexibility, such as joint range of motion and muscle extension, may influence muscle blood volume. Women have been shown to have a greater degree of flexibility than men. We examined whether there is a gender difference in the relationship between fascicle length and muscle blood volume or oxygenation in untrained men and women. In 16 untrained men and thirteen untrained women, we measured the total-[haemoglobin (Hb) + myoglobin (Mb)] (total-[Hb + Mb]) and relative oxy-[Hb + Mb] after calibrating baseline and arterial occlusion deoxygenation levels with near-infrared spectroscopy. Also, fascicle length was measured with B-mode ultrasonography at the tibialis anterior muscle during passive plantarflexion. Increases in fascicle length from baseline (ankle joint angle 120°, composed from the caput fibulae, the malleolus (pivot), and the distal epiphysis of the fifth metatarsal bone) were greater in women than in men during plantarflexion of 140° and 160° and the maximal angle without pain. However, the decreases in total-[Hb + Mb] and relative oxy-[Hb + Mb] from baseline were not different between women and men at any degree of plantarflexion. Moreover, fascicle length and total-[Hb + Mb]/muscle thickness (men > women) showed a similar relationship, with muscle thickness increasing capillary compression. These findings indicate the possibility of a mechanical function underlying muscle blood volume during muscle stretching, which is greater in women than in men.

Corticospinal excitability of the ankle extensor muscles is enhanced in ballet dancers.

We tested the corticospinal excitability of the soleus muscle in ballet dancers to clarify whether the presumed long-term repetition of the specific plantarflexion results in changes of excitability in this neural pathway. We compared motor evoked potentials of the soleus muscle at rest and during isometric contraction of the plantar flexors in dancers and non-dancers. The amplitudes of motor evoked potentials elicited by transcranial magnetic stimulation during contraction were examined against the background electromyographic activity. A regression line was calculated for each subject. Results showed that the slope of the regression line is significantly greater in the dancer group than in the control group, suggesting that the corticospinal tract of ballet dancers has adapted to long-term repetition of plantarflexion in daily ballet training.