Many people associate caregiving work with physically demanding labor.
One major reason is the significant strain placed on the body—especially the lower back.
Low back pain is reported to affect nearly 90% of care workers in Japan.
At the welfare equipment exhibition I attended last month, I noticed a clear increase in transfer robots and sit-to-stand assistive devices compared to previous years.
This reflects the growing recognition of the benefits of mechanizing transfer-related tasks.
In this article, I explain the current situation and challenges of transfer assistance, and why these movements place substantial physical burden on both caregivers and care recipients.
The explanations are based on nursing ergonomics, integrating concepts from biomechanics and real-world caregiving practice.
Challenges in Transfer Assistance
What Is a Transfer?
A transfer is the movement from one surface to another—for example, from a bed to a wheelchair.
When individuals are unable to perform this movement independently due to illness, injury, muscle weakness, or cognitive decline, caregivers commonly support or lift them.
This is a routine scene in many care settings.
Current Practice in Japan
In Japan, manual transfers remain common.
In contrast, many countries have adopted no-lift care, where caregivers are not permitted to lift people manually.
Japan revised its “Guidelines on Low Back Pain Prevention in the Workplace” in 2013, stating that manual lifting should generally be avoided.
Despite this, manual transfers continue to dominate practice in many care facilities.
Reasons include the following:
● Cost and Perceived Necessity：
Although many devices can be rented through long-term care insurance and subsidies are available, some facilities feel that the current manual methods are “good enough” and question the need for additional investment.
● Staff Attitudes and Implementation Barriers：
Even when devices are introduced, experienced staff may say:
“It takes more time.” “I can do it faster the way I’m used to.”
As a result, devices may be abandoned before staff become comfortable using them.
I have witnessed this myself.
From the care recipient’s perspective, manual transfers can also be uncomfortable or frightening:
- painful pressure under the arms
- being lifted by clothing
- the caregiver’s face uncomfortably close
- feeling unstable or at risk of falling
In understaffed environments, care tends to shift from “user-centered care” to “care that is easiest for the caregiver.”
Biomechanics of Sit-to-Stand Movements
Why instability occurs
Transfers typically involve the sequence:
standing up → turning → sitting down
Among these, standing up is the most unstable and places the greatest burden on caregivers.
To understand why, we examine two fundamental biomechanical concepts: center of gravity and base of support.
Why Objects and Humans Become Unstable
When exposed to sudden movement—such as strong wind or an earthquake—people instinctively widen their stance, bend their knees, and lower their hips.
This increases stability.
The mechanisms behind this can be explained by the following concepts.
● Center of Gravity：
The center of gravity is the point where an object’s weight is concentrated. In humans, it is located slightly below the navel. Lowering the hips lowers the center of gravity.
● Base of Support：
The base of support is the area in contact with the ground. Standing with feet apart widens the base; standing with feet together narrows it.
● Vertical Projection of the Center of Gravity：
This refers to the point where a vertical line from the center of gravity meets the ground.
- If this projection is within the base of support → the body remains stable
- If it shifts outside the base → the edge of the base becomes a pivot, creating a rotational moment that causes the body to tip
In short:
Instability occurs when the vertical projection of the center of gravity moves beyond the boundaries of the base of support.
It may be a bit difficult to intuitively understand why having a lower center of gravity improves stability, so here is a brief supplemental explanation.
A lower center of gravity increases the angular range within which the body can tilt before the projection leaves the base of support.
This is why lowering the hips increases stability—both in objects and in humans.
Why Standing Up Causes Swaying
During the sit-to-stand movement, three destabilizing factors occur simultaneously:
1. The center of gravity rises：
A higher center of gravity makes the projection more sensitive to small changes in body angle.
2. The base of support narrows：
Weight shifts toward the toes, reducing the effective support area.
3. The body leans forward：
To shift the center of gravity over the feet, the torso must incline forward, pushing the projection to the front edge of the base of support.
Together, these factors create a situation in which:
A forward rotational moment is likely to occur, increasing the risk of falling.
Younger or healthier individuals can recover using muscle strength and balance, but this is often difficult for older adults or those with medical conditions.
Why Transfers Strain the Lower Back
The instability and rotational moments that occur during standing up directly increase the caregiver’s physical burden.
Caregivers must:
- prevent the user from falling forward
- lift the user’s body
- turn their direction
- lower them into the target seat
The magnitude of the moment can be expressed as:
moment = force × distance from the pivot
In transfer assistance:
user’s body weight × distance between the caregiver’s lumbar spine and the user’s center of gravity
When the caregiver leans forward, both their upper body and the user’s weight act as a lumbar flexion moment.
To counter this, the erector spinae muscles generate a strong extension torque, which adds compressive forces and shear forces to the lumbar vertebrae.
These forces are major contributors to low back pain.
Because transfers are performed repeatedly every day, the load easily accumulates.
Closing Thoughts
Transfer assistance is essential in caregiving, yet it inevitably places significant physical burden on both care recipients and caregivers.
This is why safer methods and appropriate assistive devices have long been necessary.
Although transfer-assist technologies are increasing, their adoption in the field still feels limited.
This is precisely why I want to deepen my understanding of these devices and help introduce them to settings where they can truly make a difference.
In the next article, I will introduce the transfer robots and sit-to-stand devices I observed at the exhibition, focusing on which movements they support and how they reduce physical burden.
I am currently sharing information like this while also writing technical articles and product explanations on medical materials and care equipment.
By combining my on-site nursing experience with my knowledge of patents, I create field reports and support market development for healthcare and caregiving products.
If you are interested, please feel free to contact me via the contact form.
Please note that this article includes the author’s personal opinions and findings, and does not guarantee complete accuracy.
