Exercising at consistent times could align the body clock for better skeletal health and performance, scientists suggest

Consistent daily patterns of exercise and rest can synchronize local body clocks associated with the joints and spine with the brain clock, potentially helping individuals maintain skeletal health, improve athletic performance and avoid injury, according to University of Manchester scientists.

Although the study was published in Nature Communicationsof the mice involved, the scientists suggest that it is highly likely that human cartilage and intervertebral discs—which have very similar physiological properties—would respond in a comparable manner.

It also helps to contextualize an observation made 300 years ago by the Reverend Mr Wasse, Rector of Aynhoe in Northamptonshire, to Dr Mead, regarding the difference in the height of the human body, between morning and night.

In a letter published by the Royal Society, the reverend cited his observations of soldiers discharged from the army for being too short, claiming that we are more than half an inch taller after a good night’s sleep.

Daily rhythms in mammalian behavior and physiology are generated by a circadian system that adapts to environmental cues such as light and feeding.

Scientists have long known that misalignment of the central body clock in the brain and other organs that have their own body clock can increase the risk of pathology and diseases such as diabetes and cardiovascular disease.

However, until now very little was known about the relationship between clocks in articular cartilage that lacks nerves or blood flow and the brain.

Professor King-Jun Meng, senior author and body clock expert at the University of Manchester, said: “Not only did we identify that a mismatch between the cartilage and intervertebral disc clocks and our central brain clock can occur by exercising at inappropriate times, we found we are the mechanism by which this happens and that skeletal clocks can be resynchronized with daily patterns of physical activity.

“Our earlier work revealed internal body clocks in intervertebral discs and cartilage that dampen with age. Importantly, healthy cartilage and intervertebral discs have no nerves and no blood supply, so until now it was not clear how their internal clocks synchronize with the brain. ”

Professor Judith Hoiland, another senior author and spine/intervertebral disc expert at the University of Manchester, said: “Among the many health challenges, age-related musculoskeletal decline – and its adverse consequences – places a huge burden on individuals.

“Loss of bone density, degraded articular cartilage, and degeneration of intervertebral discs are primary features of skeletal aging, all of which can contribute to pain and loss of mobility.”

“Importantly, we have identified a new clock mechanism underlying skeletal aging, which could have far-reaching implications for understanding frailty and designing more effective treatment timing of exercise and physiotherapy to maintain good skeletal health and mobility.”

Dr Michal Dudek, lead author from the University of Manchester, said: “As we stand and move throughout the day, water is pushed out of the intervertebral discs in our spine, as well as out of the cartilage in our hips and knees, making us a little shorter.” until the end of the day, just as the Reverend Mr. Vase identified 300 years ago.

“But what he didn’t know is that this causes tissue osmolarity to increase because the same amount of mineral is now dissolved in less water, so the actual concentration increases. The cells sense this change in osmolarity and synchronize the clocks within these skeletal tissues.”

“Water returns at night when we rest and osmolarity decreases, although this direction of change had no effect on the clock.”

Scientists examined mice that exercised daily on a treadmill while resting to show what happened to the clocks in the cartilage, intervertebral disc and brain.

They confirmed the findings by compressing mouse intervertebral discs or cartilage explants in the laboratory or by exposing them to a culture medium of higher osmolarity in the normal physiological range. Both resulted in a similar clock synchronization effect.

Professor King-Jun Meng said: “We have actually identified a new mechanism for understanding how our body clocks are synchronized with the external environment.”

“Clocks have evolved to prepare you for predictable rhythmic changes in the environment.”

“Our results showed that physical activity in the morning, associated with daily sleep/wake cycle patterns, transmits time information from the brain’s light-sensitive central clock to the weight-bearing skeletal tissue. In effect, it tells your skeletal system that it’s time to I wake up.

“But when this alignment is out of whack with the brain, then, as with other organs and tissues, it can lead to adverse effects on your physical health.”

“If you’re constantly changing your workout times, you may be more prone to this desynchronization.”

“However, if you change when you exercise, but then maintain that regimen for a while, we show that eventually your body clocks will resynchronize with each other and you’ll adapt.”

He added: “So, for example, changing time zones frequently to compete in sporting events – which is an aspect of life as an international athlete, for example – can undermine athletic performance and can make individuals more prone to injury.”

“Our work showed that clocks in the skeletal tissues of older animals still respond to daily exercise patterns. As such, walking groups organized for older people may be more beneficial for their health if they occur at a similar time each day.”

Lucy Donaldson, director of research and health intelligence at Versus Arthritis, said: “We already know that exercise is one of the best ways to reduce the pain and impact of arthritis, and this very early research shows that exercising at certain times of the day could bring additional benefits for people with arthritis.

“The daily 24-hour cycle that our bodies follow, such as our core temperature falling when we sleep and our blood pressure rising at certain times of the day, is known as our circadian rhythm.” There are processes in our body that maintain this rhythm. , known as ‘clocks’, which are all connected to our central body clock in the brain.

“This early research in mice explores the link between local clocks in articular cartilage and a central body clock in the brain, which the results suggest contribute to how quickly our bones and cartilage deteriorate over time. The findings show that when these clocks go out of sync, our bones and cartilage deteriorate faster, but when they are aligned, the process slows down. Exercising at certain times of the day helps keep the clocks in sync and can slow the progression of arthritis.

“This is an important finding because it could help us develop more targeted treatments for musculoskeletal conditions such as arthritis using exercise and physical activity.”