FEATURE STORIES
Aging & Mobility
Fundamentals and Frontiers
by Adam Goodworth, Ph.D., Professor of Engineering, and Maury Hayashida ’95, DPT, Adjunct
Human movement and function affect us all as essential parts of life. We’re made to move and nearly everything we do requires movement. We find it fascinating as well, avidly watching all kinds of movement such as sports competitions and ballet. Fortunately, applying recent advanced technology can help people with limited mobility.
Movement is intuitive, but it becomes more elusive as we age. How do we optimize our condition and maximize movement throughout life? How can we adapt as we age to move safely and continue to thrive?
Babies learn how to move without instruction and eventually become adept at walking. We can learn a lot about the development of motor control from babies; for example, the neurological and biomechanical need for crawling precedes walking or sensory integration. As we grow, we acquire skills and become more adept. Once we mature, we maintain our ability to move. But as we age, moving becomes more difficult.
Movement involves stability and balance, posture and gait, and coordination so we can control objects in our environment and move effectively and efficiently. Perception and action work together in this process. Perception includes what our brains perceive from the sensations we receive through our body: our sensory input. In action, muscle activations move our body within our constraints — such as the range of motion of our joints — and within our environment. How we move depends on the environment.
Finally, we need stability to move at all. Even sitting requires the brain to actively use sensory feedback to generate muscle activations, and this task becomes even more involved for standing and walking.
We want to accomplish tasks and must deal with constraints in our environment. Our minds assess the situation to determine how to adapt to the environment and achieve a positive outcome.
Why does movement matter? It’s essential to our mental, emotional and physical wellbeing, as many of us discovered during the pandemic. During COVID, being active mattered to all areas of my wellbeing. This is especially true as we age. Our physical systems — skeletal, muscular and neurological — depend on movement.
The ability to move competently and independently in large part determines our quality of life. Engaging in physical activity helps us move and matters more than anything else we do. What constitutes effective activity? The range of actions includes daily sports, leisure pastimes, recreational activity, gardening, exercise and other physical pursuits. We use it, or we lose it.
We experience life socially through movement. We feel and move differently as we grow older, with muscles atrophying more quickly, bones demineralizing and physiological changes. Adequate gait speed — how fast we walk — and body balance help us increase physical activity, which reduces the likelihood of falling. We need to control our center of mass for physical activity so we can walk faster, have good posture and maintain our balance. We need to be proactive about being active.
It’s critical to identify and minimize risks that contribute to falling before the initial fall occurs because research demonstrates that falls happen more frequently after the first one. We can do a lot to minimize falls. Consider these sobering statistics. More than one in four adults aged 65 or older fall each year — and each fall doubles the odds of falling again. One in five falls causes serious injury, including about 300,000 hip fractures each year. One study found that older individuals with this injury have a 26 percent mortality rate within 24 months of their fall. In 2015, falls by older people cost more than $50 billion.
In our culture, lots of social conveniences keep us from moving, such as cars, elevators and electric bikes. We can find a lot of reasons to stay sedentary. Other obstacles include social determinants that lead us to be less active. As our physical condition declines, we may experience more pain when we move or suffer from neurodegenerative diseases. In addition, beliefs about falls and aging can make us wary. If we fear movement, we’ll likely limit it. And if we fear falling, we’re more likely to fall. Simply increasing the speed of our gait and achieving better balance can’t prevent falls. We need physical activity to do that.
We may think we’re too old to run, play pickleball or participate in other activities. But if we avoid everything, we regress physically. We encourage people to stay active. Don’t give up. Don’t stop. You can always find ways to improve how you move and maintain a good quality of life. You just need to be better, not perfect. You need to find movement that works for you and helps you maintain an active lifestyle.
Research about older adults and their nervous systems can help us improve balance and understand how best to control our center mass, a key principle of controlling our overall stability. When we stand, we generally need to keep our center of mass within our base of support. As we age, widening our feet, holding onto a wall and using an assistive device like a cane can increase our base of support. However, expanding the base of support too much can negatively affect efficient movement or gait.
We need to do this because the force of gravity makes our bodies inherently unstable. As we deviate from an upright posture, the force of gravity acts on us more strongly, and the torque becomes greater. We need muscle strength to adjust and maintain balance, and physical activity helps us become stronger.
Imagine someone balancing a stick on their finger. How would that work if they closed their eyes? Balance requires feedback from multiple senses. First of all, we must see our environment to overcome any obstacles. We also require our inner ear to provide important information about our location relative to gravity: our vestibular system. The movement of hair cells in the inner ear sends electrical signals to our brains, which the brain interprets. Our body also gets important information from our surroundings: somatosensory. We get sensory feedback from neurons in our muscles and skin when they get stretched and send signals to our brain so we know where we are and which muscles to activate.
Each of these systems degrade over time, usually at different rates. About 35 percent of adults aged 40 or older experience difficulties with the inner ear: vestibular dysfunction. Visual impairment doubles between the ages of 50 and 80. With structural and physiological functions declining, our bodily sensory receptors decline. Each sensory system provides different information, and each has inherent variability in neural firing (known as “noise”) that can limit the brain’s ability to interpret the information. We automatically change reliance on each system as we age. When one declines, we compensate by putting emphasis on others. It’s good to practice balance in a variety of contexts so we can learn changing reliance across sensory systems. The more we use sensory feedback for meaningful functional movement, the more our brain can refine the use of multisensory feedback to reduce degradation.
Balance is anticipatory. Our brains look at the environment and plan what we do, sometimes unconsciously. The brain automatically helps us maintain balance, activating muscles we need to maintain balance. Age can delay this anticipatory movement. When we face a small challenge to our balance, we may rotate our ankles and shift back and forth. For larger challenges, we may bend our knees. For more serious challenges, we may change our base of support, reach for a wall or table or use a cane. Older people may see challenges as more severe than they are. As we keep our center of mass inside our base of support, recognizing that we’re inherently unstable, we rely on feedback from multiple senses, which our brain integrates. The more we learn how to respond to problems with balance, the more adaptive we become, the more we’re able to maintain our posture.
Technology helps us identify potential problems with balance by putting sensors on people and measuring how they move. It then allows us to monitor efforts to improve. Here are some examples.
- Jumping or standing on a force plate measures the ground reaction forces under our feet and our ability to generate power or be symmetrical or stationary.
- Wearing an accelerometer near the chest or center of mass while walking around measures movement and balance. People with deficiencies in their inner ears may wear them on their heads to identify abnormal head movements.
- Applying an EMG system (electromyography) to muscles provides information about the nervous system and how it activates muscles and identifies disorders.
Technological advances and the rise of artificial intelligence could result in even more effective ways to measure and improve fundamental human movement. Current screening tools focus on balance, strength, agility and coordination.
All our movements in daily life come from three task-related motor skills: posture (balance and position control), locomotion (moving the body from place to place), and object-interaction (movements that require the use of other objects). Screening can assess our competencies in these areas and help personalize training and treatment so we can improve.
It’s never too late to increase your activity, but it’s most effective to start early. Begin by establishing stability first and moving on to mobility and building strength. Seniors can participate in exercise programs that prevent falls, which have proven effective for people regardless of their risk of falling.
We advise starting simple with low technology and frequent activity. That will build stamina. Exercising in different contexts and envi- ronments can provide helpful variety. Once you begin, never stop. Physical activity has proven to be the best way to grow stronger, improve balance and keep moving well throughout life.