Dec. 12, 2024

Future Fitness ResearchInnovative Equipment to Boost Your Motivation

At Toyota Motor Corporation's Frontier Research Center, we focus on "improving and maintaining physical function" as one of the critical elements that contribute to human well-being, aiming for the "mass production of happiness." Many people desire to exercise daily for health reasons, not just for dieting, yet find it challenging to maintain the routine. The Frontier Research Center is engaged in research on fitness equipment that somehow makes people want to keep exercising. For this article, we interviewed Takeda about this research.

- It sounds like a dream to have fitness equipment that makes you want to continue exercising, but what kind of equipment are you talking about?

Takeda: The equipment itself is pretty simple. It consists of three main parts (Movie 1, Figure 1). The first part is pedals that move like cycling. The second is a seat that can rotate freely. The third is strings that connect the pedals to the seat. Would you like to try it out?

: Movie 1 Development Equipment^*1
We modified commercially available pedal exercise equipment by connecting the pedals to the seat with strings, so that pressing one pedal rotates the seat, making it easier to press the other pedal. The pedal exercise equipment has pedals mounted with 180 degrees phase difference, similar to a bicycle, and the strings are alternately pulled left and right in accordance with the pedal movements. The strings are attached to the sides of the seat, and by pulling the string, the seat rotates.

: Figure 1 Structure of the Development Equipment (Condition A)^*1
When you try to push one pedal with your foot, the string on the same side as your foot gets pulled, resulting in the rotation of the seat. To connect the string, we extended the length of the pedal axis and attached a circular plate to the end, adjusting it so that the center of the plate aligns with the center of rotation. By changing the attachment position of the string relative to the pedal axis, we altered the relative movement of the pedals and the seat. When the string is attached at a position of +90 degrees in the forward rotation direction relative to the pedal axis, just before pushing down with your foot, the hip on the same side moves forward, and this movement of the hip supports the foot's downward motion.

- It feels very interesting. Once I start pedaling, I feel like I want to keep pedaling. Why does this phenomenon occur?

Takeda: The key is this string. When you push one pedal, the string pulls the seat to the right or left. When one side of the seat is pulled forward, the hip rotates with the seat, making it easier to step forward with your foot.

- I see, my own pedaling motion is transmitted to the seat through the string, which encourages my next stepping motion. Where did this idea come from?

Takeda: This idea emerged while I was trying to create equipment that makes people want to continue exercising. First, I made a chair that moves with an electric motor and tried pedaling while sitting in it (Figure 2). I definitely felt a sense of wanting to keep pedaling. After trying it multiple times, I realized that moving the left hip forward makes it easier to step out with the left foot. However, since the foot movement was triggered by the electric motor's movement, there was a sense of being forced to do it. I thought that if the desire to pedal could be triggered by one's own movements, it could reduce that feeling of being forced.

: Figure 2 Induction of Pedaling Motion with a Preliminary Equipment^*1
Sitting in a chair that rotates with an electric motor, you feel encouraged to pedal in accordance with the movement of the seat. For instance, rotating the seat with a sine wave trajectory of plus-minus 10 degrees at a frequency of 1Hz. When the left side of the seat moves forward, the left hip is pushed forward, making it easier to step out with the left foot. Conversely, when the right side of the seat moves forward, the right hip is pushed forward, making it easier to step out with the right foot. This alternation creates a periodic induction of pedaling motion.

- It was a discovery born from trial and error. Does this phenomenon occur for everyone?

Takeda: That's a good question. It is a phenomenon that occurs for many people. I had the same question, so I had several colleagues from the same workplace try it. As a result, most of them responded that they somehow want to move, but one person replied that they didn't particularly feel like moving. At that moment, I wanted to try something: adjusting the timing of when the seat is pulled. When I had that person try it with the string attached at the exact opposite position from the original setup (Figure 3), they responded that they really wanted to move. It seems that the timing of when people want to keep moving differs from person to person. Therefore, I had 36 experimental participants try both Condition A, which made me want to move, and Condition B, which made the other person want to move.

: Figure 3 Condition B^*1
When attempting to push one pedal with your foot, the string on the opposite side is pulled, resulting in the rotation of the seat. To connect the string, we extended the length of the pedal axis and attached a circular plate to the end, adjusting it so that the center of the plate aligns with the center of rotation. The attachment position of the string relative to the pedal axis was modified so that the pedals and the seat would change relative movement. When the string is attached at a position of -90 degrees in the forward rotation direction relative to the pedal axis, just before pushing down with the foot, the hip on the opposite side moves forward, and this hip movement supports the foot's downward motion. Compared to Condition A, the attachment position of the string differs by 180 degrees, pulling the string opposite to the foot that is about to push down.

- What were the results?

Takeda: Yes. More people felt they wanted to move in Condition A, while there was more variation in feelings in Condition B (Figure 4). Of the 36 participants, 33 wanted to move in either Condition A or Condition B, or both (Figure 5). Additionally, many people felt that Condition A was easier to pedal, while opinions were sharply divided in Condition B (Figure 6). Furthermore, analyzing these results revealed that in both Conditions A and B, people who wanted to continue pedaling also felt that it was easier to pedal (Figure 7). Even with such a simple motion, the way people use their bodies varies, and delving into these individual differences adds depth to the research on how to move the body.

: Figure 4 Seven-Point Questionnaire Results on the Sensation of Induced Pedaling Motion^*2
The sensation of wanting to pedal was defined as the feeling of being induced to pedal. When the no-string condition is set as a baseline of 4, answers of 5 or higher indicate feeling induced, while answers of 3 or lower indicate feeling suppressed. In Condition A, many people reported feeling induced, and a statistically significant difference was confirmed (the null hypothesis that the population mean of the evaluation results is the same as the baseline of 4 was rejected with p<0.01 in the t-test). In Condition B, individual differences were observed in the feeling of being induced (the above statistical test did not reject the null hypothesis).

: Figure 5 Scatter Plot of Seven-Point Questionnaire Results on the Sensation of Induced Pedaling Motion^*2
The sensation of wanting to pedal was defined as the feeling of being induced to pedal. When the no-string condition is set as a baseline of 4, answers of 5 or higher indicate feeling induced, while answers of 3 or lower indicate feeling suppressed. The horizontal axis represents the questionnaire results for Condition A, while the vertical axis represents those for Condition B. Out of 36 participants, 33 responded with 5 or higher in either Condition A or Condition B, or both. Thus, 33 out of 36 participants reported feeling induced in this experiment. For the sake of graph display, random numbers within a range of plus-minus 0.1 were added to the questionnaire results to create the scatter plot.

: Figure 6 Seven-Point Questionnaire Results on the Ease of Pedaling^*2
When the no-string condition is set as a baseline of 4, answers of 5 or higher indicate feeling it is easy to pedal, while answers of 3 or lower indicate feeling it is hard to pedal. In Condition A, there was a tendency to feel that it was easy to pedal, but no statistically significant difference was confirmed (the null hypothesis that the population mean of the evaluation results is the same as the baseline of 4 was not rejected in the t-test). Conversely, there was strong individual variation in perceived ease of pedaling in Condition B, with opinions divided (the above statistical test did not reject the null hypothesis).

: Figure 7 Relationship Between Induction Sensation and Ease of Pedaling^*2
Based on the seven-point questionnaire results, the relationship between the sensation of induced pedaling and ease of pedaling was investigated. Both Conditions A and B showed a positive correlation between the sensation of induction and ease of pedaling (correlation coefficient r>+0.6). For the sake of graph display, random numbers within a range of plus-minus 0.1 were added to the questionnaire results to create the scatter plot.

- These results are very interesting. Why does the phenomenon of wanting to keep moving occur in the first place?

Takeda: This phenomenon can be explained by two factors. First, when one part of the body moves, it becomes easier for surrounding parts to move as well. For example, when the hip moves, the foot naturally becomes easier to move. This interconnection of body movements is referred to as the "kinetic chain^*3." Secondly, it is said that our bodies are equipped with a mechanism that allows a rhythmic continuation of movement when walking or running. This mechanism enables us to continue moving rhythmically without particularly focusing on it. This mechanism is called a "Central Pattern Generator (CPG^*4)." In summary, it is believed that this phenomenon arises from the interplay of the kinetic chain, where hip movements assist foot movements, and the function of the CPG that enables rhythmic actions.

- By deeply understanding how the human body is used, the mechanisms that encourage continued exercise may become clearer. In what fields could this technology be applied?

Takeda: Indeed. Understanding the mechanisms that encourage continued exercise could lead to technologies for those who struggle with exercise. For example, it might help elderly individuals or those with low motivation to exercise continue their routines more easily. Particularly, if development progresses in creating equipment tailored to individual body usage, it could enable personalized exercise support for each person.

- That sounds wonderful. I look forward to the future research.

Column: Which are your body movements?

What kind of body movements do you make when drinking from a plastic bottle? You may not have thought about it deeply, but some people use their wrists skillfully to drink, and others tilt their chins upwards. Those who use their wrists effectively make compact movements, while those who lift their chins make more significant movements. Of course, neither of these movement styles is superior to the other. You can also try deliberately using a different movement style, but you might feel awkward.
Even in everyday actions, individuals may vary, but they can broadly be categorized into two patterns. For instance, when carrying a bag, there are ways to hook it with fingers and grip it with the palm. Similarly, one can use only the wrist or involve the entire arm when fanning with a hand fan. There may be some relationship between these movement patterns.
Interestingly, even simple daily actions can reveal individual uniqueness. You might want to discuss how you and those around you move casually. Just that might make your daily life a little more enjoyable.

: Variations in Body Movements in Daily Life
Left: How to Use a Fan, Middle: How to Drink from a Plastic Bottle, Right: How to Hold a Bag

Author

Takahiro Takeda
Ph.D. (Engineering), Assistant Manager, Quantum Human Research Group, Frontier Research Center
Joined Toyota Motor Corporation in 2008. Specialized in robotic engineering in graduate school. After joining, he was involved in the development of partner robots, particularly in rehabilitation assist robots, which sparked his interest in systems related to humans. He is currently conducting research on human well-being from the perspectives of biomechanics and psychology. In research aimed at improving the adherence to exercise, he emphasizes the importance of autonomy and has personally experienced a 9-kilogram weight loss by applying this to his own diet.

Copyright

Some copyright of this article belongs to the Japan Society of Mechanical Engineers (Movie 1, Figures 1-3) and the Japan Society of Kansei Engineering (Figures 4-7). This article has been published with permission from the above societies. For inquiries regarding the use of Movie 1 and Figures 1-7, please contact the respective societies.

Research Ethics

The experiments reported in this article were conducted with approval from the Research Ethics Committee of Toyota Motor Corporation (Approval Number 2023TMC132).

Supplementary Explanations and References

*1	Takahiro Takeda, A device that induces voluntary seated pedaling movements, Proceedings of JSME annual Conference on Robotics and Mechatronics (Robomec) 2024, 1P1-F09, 2024. (written in Japanese)
*2	Takahiro Takeda, Evaluation of an equipment inducing voluntary seated pedaling movements―Do the user's own movements alter induced sensations?―, Proceedings of the 26th Annual Meeting of Japan Society of Kansei Engineering, P3-14, 2024. (written in Japanese)
*3	A phenomenon where the movement of one part of the body propagates to surrounding parts. Haifa Saleh Almansoof, Shibili Nuhmani, Qassim Muaidi, Role of Kinetic Chain in Sports Performance and Injury Risk: A Narrative Review, Journal of Medicine and Life, 2023 Nov; 16 (11): 1591-1596.
*4	Abbreviation for Central Pattern Generator. It plays a role in generating the rhythm of periodic movements. Straub, V.A. (2009). Central Pattern Generator. In: Binder, M.D., Hirokawa, N., Windhorst, U. (eds), Encyclopedia of Neuroscience. Springer, Berlin, Heidelberg.