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J Phys Ther Sci
J Phys Ther Sci
JPTS
Journal of Physical Therapy Science
0915-5287
2187-5626
The Society of Physical Therapy Science

2024-052
10.1589/jpts.36.551
Original Article
Motion capture-based evaluation of lower chopstick stability
Choji Yuki OTR, PhD 1 *
Saito Kotoko RPT, PhD 2
1) Occupational Therapy Course, Department of Rehabilitation, Faculty of Allied Health Science, Niigata University of Rehabilitation: 2-16 Kaminoyama, Murakami-shi, Niigata 958-0053, Japan
2) Department of Rehabilitation, Faculty of Medical Sciences, Shonan University of Medical Sciences, Japan
* Corresponding author. Yuki Choji (E-mail: choujiyuki@gmail.com)
5 9 2024
9 2024
36 9 551556
02 5 2024
12 6 2024
2024©by the Society of Physical Therapy Science. Published by IPEC Inc.
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives (by-nc-nd) License. (CC-BY-NC-ND 4.0: https://creativecommons.org/licenses/by-nc-nd/4.0/)
[Purpose] When using chopsticks with a standard grip, the lower chopstick is held firmly; the upper chopstick dominates the motion between open and closed postures. This study’s primary aim was to evaluate the stability of the lower chopstick when maneuvering with the dominant hand. The secondary goal was to test whether using chopsticks with the non-dominant hand improves the stability of the lower chopstick. [Participants and Methods] The study included 34 healthy adults as participants. Motion capture was used to assess the stability of a lower chopstick held with the dominant hand and explore the effect of training on lower chopstick stability with the non-dominant hand. [Results] Prior to non-dominant hand chopstick training, the stability of the lower chopstick was significantly greater when held with the dominant hand than when held with the non-dominant hand. However, after 10 days of non-dominant hand chopstick training, the stability of the lower chopstick held with the non-dominant hand improved significantly. [Conclusion] This study’s findings provide important insights into the effectiveness of non-dominant hand training in patients who need to use their non-dominant hands.

Chopsticks
Non-dominant hand
Pincers-pinching
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pmcINTRODUCTION

Individuals undergoing rehabilitation may need to rely primarily on their non-dominant hand owing to functional limitations or functional loss in their dominant hand. Mastering chopstick usage with the non-dominant hand poses significant challenges but has immense importance in the daily lives of these individuals1). While independent meal consumption has been recognized as a factor that influences quality of life and the significance of chopstick usage in daily life has been well established2), research on effective training methods for chopstick usage with the non-dominant hand is scarce. Through a literature review, it was found that the most prevalent training method practiced in Japan involves repeatedly transferring objects (e.g., marbles, beans, and sponges) of varying sizes, weights, and shapes from one plate to another using chopsticks3). Additionally, several studies have examined the effects of written materials outlining proper chopstick usage techniques and training devices on the improvement of chopstick usage. However, these studies primarily focused on chopstick usage with the dominant hand4,5,6). Thus, the mechanism by which individuals can enhance their skills of chopstick usage with the non-dominant hand through training remains elusive.

Chopsticks are the most fundamental and convenient dining utensils for Japanese people, and they are used daily for various meals. Chopstick holding techniques vary across countries and cultures, but there are two primary modes of holding chopsticks, namely, scissors-pinching and pincers-pinching7). The scissors-pinching mode, which is characterized by a forceful grip using the thumb and index finger, sacrifices pinching precision and chopstick stability for power. Conversely, the pincers-pinching mode, which is revered for its exceptional pinching precision and stability in Japan and China, allows effortless handling of delicate food items, such as small fish, peanuts, and tofu6,7,8,9). Therefore, the pincers-pinching mode is currently the most recommended when using chopsticks.

For employing the pincers-pinching mode when using chopsticks, a sequence of steps is typically followed10). First, the bottom chopstick, which is also called the “fixed” chopstick, is placed between the base of the thumb and index finger. It is kept resting on the first joint of the ring finger and the second joint of the thumb for stability. Second, the top chopstick, which is sometimes referred to as the “movable” chopstick is picked. It is held alongside the middle finger and gripped with the tips of the thumb and index finger. Finally, the index and middle fingers are used to move the “movable” chopstick up (open) and down (closed) to pick up food. The “stationary” chopstick should remain in place for stability. Figure 1Fig. 1. The operation of chopsticks.

provides an illustration of the procedure for chopstick usage. When picking up an object with chopsticks, the upper and lower chopsticks must be controlled independently, demanding a higher level of dexterity when using chopsticks than when using other common hand tools. Thus, a relatively extended learning and practice period is required to achieve proficiency in chopstick usage.

The successful use of chopsticks in the pincers-pinching mode has been widely recognized to depend on the stability of the lower chopstick6,7,8,9). In previous studies, test participants were asked to hold an upper normal chopstick and a lower inked chopstick, and the amount of ink transferred to their ring finger during chopstick operation was used as an indirect measure of lower chopstick stability11, 12). Additionally, Yokubo et al.13) reported a method of visually counting the number of rotations of each chopstick to assess the stability of the lower chopstick during a cutting operation. However, no simple tool exists to directly evaluate lower chopstick stability during chopstick usage. The primary objective of this study was to assess the stability of the lower chopstick held with the dominant hand, using motion capture. The secondary objective was to validate whether training to use chopsticks with the non-dominant hand enhances lower chopstick stability. The stability of the lower chopstick was considered as its state of being securely anchored and immobile while holding food during traditional chopstick usage. This stability ensures that the lower chopstick remains firmly fixed in place, allowing for precise manipulation of the upper chopstick without any unwanted movement or instability, and it enables effective grasping of food items and facilitates a smoother dining experience.

PARTICIPANTS AND METHODS

This study recruited 40 healthy adult volunteers who habitually used chopsticks with the pincers-pinching mode. All participants were right-handed according to the Edinburgh Handedness Inventory14). Of the 40 volunteers, 34 (16 male and 18 female volunteers) were eventually included in the study and 6 were excluded owing to early withdrawal. The mean age of the 34 participants was 23.26 ± 9.34 years. Moreover, their mean right and left hand lengths were 170.68 ± 8.99 mm and 171.00 ± 8.81 mm, respectively. This study was approved by the Ethics Committee of Niigata University of Rehabilitation (number: 193). Prior to data collection, participants were informed about the study’s purpose and procedures. All participants provided verbal and written consent for data recording using a motion capture system with a video camera. The authors adhered to the ethical principles of information anonymity and confidentiality throughout the research.

Motion capture technology has emerged as a crucial tool in human motion recognition and motor function assessment for rehabilitation purposes15). Human motion capture systems, which employ motion-sensing position sensors strategically placed on key body segments, capture real-time posture information during human movement. Characteristic parameters of the movement process are extracted through data fusion and computation, enabling objective real-time tracking of human motion. However, high costs and complex setups, including stringent lighting conditions and multiple cameras surrounding the subject, have restricted the application of motion capture systems primarily to laboratory settings. The TT-Z tablet tracker (Library Co., Ltd., Tokyo, Japan) offers a promising solution as it uses a simplified measurement approach based on markers attached to body parts. The study employed this tablet tracker to evaluate the stability of the lower chopstick held with the dominant hand and to investigate the effect of training to use chopsticks with the non-dominant hand on lower chopstick stability.

A motion capture system based on the TT-Z tablet tracker with position sensors was employed (Fig. 2Fig. 2. The tablet tracker TT-Z.

), and it specializes in capturing finger movements. The system not only enables precise measurement of the distance between two measurement points and the angle based on three measurement points but also automatically tracks the accurate positions of these points, allowing for the evaluation of lower chopstick stability during chopstick usage. Color markers with three distinct colors (light blue, blue, and green) and a diameter of 9 mm (3 M Japan Ltd., Tokyo, Japan) were attached to the measurement points. A light blue marker and a green marker were affixed to the tip of the ring finger and the contact surface between the lower chopstick and the ring finger, respectively, to calculate the distance between the two points. Subsequently, a light blue marker, a green marker, and a blue marker were attached to the contact surface between the lower chopstick and the ring finger, the contact surface between the lower chopstick and the index finger, and the center of the metacarpal bone of the index finger, respectively, to determine the three-point angle (Fig. 3Fig. 3. The distance between two points and the angle between three points.

).

Disposable bamboo chopsticks (length: 200 mm, weight: 8 g), which are readily available and widely used in Japan (Fig. 4Fig. 4. Experimental chopsticks.

), were employed in this study. All motion capture measurements were conducted at Toyama Rehabilitation Medical Health and Welfare College.

Participants were seated in a chair (height: 435 mm) at a desk (height: 700 mm) and instructed to hold a pair of chopsticks with either their dominant or non-dominant hand. They were instructed to place their elbows on the desk and keep their forearms pronated at an angle of 45°. The chopsticks were initially held in a closed posture (Fig. 2).

The stability of the lower chopstick held with the dominant hand was assessed using the distance between the two measurement points and the three-point angle assessed with the TT-Z system during repetitive motions involving the open and closed postures of the chopsticks. Additionally, the number of contacts between the tips of the upper and lower chopsticks during the repetitive motions was evaluated. The test participants were instructed to repeatedly open and close the chopsticks in accordance with a rhythmic beep sound (beep per second) emitted from the TT-Z system for a duration of 30 s. They were asked to complete one entire motion of opening and closing the chopsticks per second. The movement of the chopsticks was recorded from the front of each participant, using the TT-Z system with a video camera. The distance between the two measurement points and the three-point angle were analyzed using the TT-Z system, while the number of contacts between the tips of the upper and lower chopsticks was determined by analyzing the recorded videos. Participants were instructed to maintain an angle greater than 0° between the upper and lower chopsticks in the open posture. Measurement was terminated if the chopsticks were dropped or the starting closed posture could not be maintained.

Subsequently, participants underwent training to use chopsticks with the non-dominant hand. The training consisted of 10-minute training sessions performed 10 times over a 10-day period. During the initial intervention, the first author (CY) demonstrated the correct placement of the fingers and the appropriate movement of chopsticks. Each participant received a manual for correctly using chopsticks for further self-training at home. The training protocol, which was based on the Isshiki training method6), included instructions on proper chopstick grip, basic chopstick movement between the open and closed postures, and the principle of keeping the lower chopstick stationary while moving only the upper chopstick. Data were collected at the pre-intervention, mid-intervention (day 5), and post-intervention (day 10) stages. The number of contacts between the tips of the upper and lower chopsticks, the distance between the two measurement points, and the three-point angle were measured thrice at each time point using the TT-Z system. Participants who did not complete the training did not attend the posttraining assessment and were excluded from the study.

All statistical analyses were performed using the SPSS statistical software package (version 27.0.1; IBM Corp., Armonk, NY, USA). One-way analysis of variance (ANOVA) with Bonferroni correction was conducted for the collected data at each time point (pre-, mid-, and post-intervention). The significance level was set at 0.05, and a p-value of <0.05 was considered statistically significant.

RESULTS

The average number of contacts of the tips of the upper and lower chopsticks held with the dominant hand was 30.00 ± 0.00 times. The average distance between the two measurement points was 9.98 ± 9.39 mm, and the average three-point angle was 95.45 ± 11.87°.

The study compared the data obtained from 34 participants who underwent training to use chopsticks with the non-dominant hand at the pre-, mid-, and post-intervention stages. One-way ANOVA revealed a significant effect of training on lower chopstick stability during chopstick usage with the non-dominant hand. Adjusted Bonferroni post-hoc tests demonstrated a significant improvement in the average number of contacts of the tips of the upper and lower chopsticks held with the non-dominant hand, with an increase from 21.12 ± 12.10 times at the pre-intervention stage to 26.32 ± 7.76 times at the mid-intervention stage and 28.53 ± 4.54 times at the post-intervention stage. The distance between the two measurement points also exhibited significant improvement (p<0.05), reaching a mean value of 10.16 ± 5.77 mm at the mid-intervention stage and 10.12 ± 7.74 mm at the post-intervention stage. Moreover, the three-point angle showed significant improvement (p<0.05), with a mean value of 94.25 ± 13.11° at the mid-intervention stage and 95.22 ± 12.29° at the post-intervention stage. Notably, no significant differences were observed between the mid- and post-intervention data for all three outcome measures. Furthermore, in the comparison between the dominant and non-dominant hands, significant differences were observed in all three metrics between the pre-intervention stage of the non-dominant hand and the dominant hand (p<0.05).

Details are presented in Table 1Table 1. Comparisons of the number of contacts between the upper and lower chopstick tips, distance between two measurement points, and angle among three points for the dominant and non-dominant hands at the pre-, mid-, and post-intervention stages

	DH	NDH	p1	p2	p3	p4	p5	p6	
	
Pre	Mid	Post	
	
Mean (SD)	Mean (SD)	Mean (SD)	Mean (SD)	
Number of contacts between the upper and	30 (0.00)	21.12 (12.10)	26.32 (7.76)	28.53 (4.54)	**	*		*	**		
lower chopstick tips, time	
Distance between two measurement points, mm	9.98 (9.39)	15.96 (13.09)	10.16 (5.77)	10.12 (7.74)	*			*	*		
Angle among three points, degrees	95.45 (11.87)	86.37 (12.38)	94.25 (13.11)	95.22 (12.29)	**			*	**		
**p<0.01; *p<0.05.

DH: with dominant hand; NDH: with non-dominant hand; Pre: preintervention; Mid=5 days after the intervention; Post: 10 days after the intervention; p1: difference of DH and pre measures; p2: difference of DH and mid measures; p3: difference of DH and post measures; p4: difference of pre and mid measures; p5: difference of pre and post measures; p6=difference of mid and post measures; SD: standard deviation.

.

DISCUSSION

This study investigated lower chopstick stability during opening and closing movements using a tablet tracker. Our initial hypothesis was that the lower chopstick remains stationary during chopstick manipulation, which is a crucial factor for effective and stable chopstick use. However, our analysis of the distance between the two measurement points and the three-point angle assessed using the TT-Z system revealed slight movement of the lower chopstick even when using the dominant hand. This discrepancy between our hypothesis and the experimental findings is likely related to the movement of the upper chopstick during chopstick operation. Yamakawa et al.16) demonstrated that the position of the supporting point and the position and angle of the fingers are critical factors for distinguishing between correct and incorrect chopstick usage. Additionally, Hsu and Wu10) proposed a third-class lever analogy to explain the characteristics of the pincers-pinching mode, highlighting the importance of the positional relationship between the upper and lower chopsticks. The positional relationship between the upper and lower chopsticks is likely to influence lower chopstick stability, warranting further investigation.

Previous research has suggested that the shape and length of chopsticks can affect the stability of chopstick manipulation. Hsu and Wu10) found that the length of chopsticks significantly affected the performance of serving food, with 240-mm chopsticks found to be optimal for adults. Chen7) recommended the use of chopsticks with rounded grips and square tips for general dining, while Ho and Wu8) advocated for bamboo chopsticks over stainless steel or plastic ones. Additionally, cultural influences on chopstick usage should be considered, particularly in Japan and other Asian countries. Tang17) observed that Japanese chopsticks are generally 1 or 2 inches shorter than Chinese chopsticks. The difference in length between Japanese and Chinese chopsticks can be attributed to distinct dining practices. Japanese people typically serve food for each individual before eating, while Chinese people commonly consume food from shared serving plates, necessitating longer chopsticks to facilitate both eating and serving. Consequently, various factors can influence chopstick usage. While the results of this study involving bamboo chopsticks, which are the most common chopsticks in Japan, provide valuable insights into the objective evaluation of lower chopstick stability, future studies should consider the effects of chopstick shape, diameter, weight, and material.

This study additionally aimed to validate the effectiveness of a 5-day training program for enhancing lower chopstick stability during usage with the non-dominant hand. The results conclusively demonstrated significant improvements in chopstick manipulation with the non-dominant hand following the 5-day training regimen. However, further training extending to the 10th day did not yield any additional improvements. This suggests that a 5-day training period is sufficient to enhance lower chopstick stability during usage with the non-dominant hand among healthy adults. Our previous literature review indicated that training durations of 1–20 days and 15–25 days were adequate for improving chopstick manipulation with the non-dominant hand among healthy Japanese participants and Japanese stroke survivors, respectively3). The observed difference in the training duration (10 vs. 20 days) for chopstick manipulation with the non-dominant hand implies that the ease of improvement varies significantly between individuals, highlighting the need for a standardized evaluation method. Given the reported difficulty in mastering the pincers-pinching mode with the non-dominant hand3), it is essential to subdivide the training process. Our study focused on the fixation of the lower chopstick, which is a fundamental aspect of the pincers-pinching mode. We believe that this approach could serve as a clinically relevant and objective index. The proposed system offers a simple and robust solution for monitoring chopstick operation. The tablet-based system can be easily set up in various settings, making it a promising tool for rehabilitation applications.

The present study has some limitations. The focus of this study on healthy adults limits the generalizability of its findings. Additionally, the study employed two to three color markers attached to the fingers and chopsticks for measurement. However, there is currently no established method for evaluating lower chopstick stability. Further research, including an assessment of the accuracy of the tablet tracker system, is warranted to address these limitations.

In conclusion, this study assessed the effects of training in chopstick use with the non-dominant hand and evaluated lower chopstick stability during the transition between open and closed postures. The study had the following key findings: 1) There was slight movement of the lower chopstick during chopstick manipulation even with the dominant hand, as evidenced by the distance between the two measurement points and the three-point angle assessed using the TT-Z system and 2) Five-day training based on the Isshiki method effectively enhanced lower chopstick stability during usage with the non-dominant hand.

Conference presentation

Portions of this study were presented at a conference (Japanese Occupational Therapy Congress & Expo, 2022, 56: 1001-1001).

Funding

This study was supported by the Meiji Yasuda Mental Health Foundation, Japan, and is registered at UMIN-CTR (No. UMIN000046277).

Conflict of interest

The authors report no conflict of interest.
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