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For happy bones and joints, exercise at the same time of day

If you’ve ever started a new exercise plan or diet, you’ll most likely have been told many times that consistency is the key to reaching goals. Now, scientists for the first time have found that sticking to a daily routine of when you work out could be just as important for bone and joint health.

A study out of The University of Manchester has looked at internal body clocks to see how exercising at the same time of day can potentially shield against bone and joint deterioration, protecting against injury and stave off age-related physical decline and associated conditions such as arthritis.

“Among the many health challenges, the age-related musculoskeletal decline – and its adverse consequences – is a major burden to individuals,” said senior author Judith Hoyland, and spine/intervertebral disk expert from The University of Manchester. “We have identified a new clock mechanism underlying skeletal aging, which could have far-reaching impacts on understanding frailty and designing more efficient treatment timing of exercise and physiotherapy to maintain good skeletal health and mobility.”

Essentially, our behavioral and physiological patterns are somewhat governed by a 24-hour circadian ‘clock’ that operates out of our brain’s suprachiasmatic nucleus in the hypothalamus on cues from the environment, such as light, dark and hunger.

“The daily 24-hour cycle that our bodies follow, such as our internal temperature dropping when we sleep and our blood pressure rising at certain times of day, is known as our circadian rhythm,” said Lucy Donaldson, Director of Research & Health Intelligence at collaborating organization Versus Arthritis. “There are processes inside our body which keep this rhythm going, known as ‘clocks,’ which are all linked to our central body clock in the brain.”

Studies have shown that if those other clocks are out of whack with our central timekeeper, it presents a higher risk of many health conditions including cardiovascular disease. Research suggests fat cells have their own biological clock, and the cardiovascular system’s own ticker may explain the prevalence of morning heart attacks.

Now, for the first time, University of Manchester researchers have unlocked the mechanisms that make the body’s intervertebral disk and cartilage clocks tick. With no nerves nor blood supply, until now it has not been entirely clear that the brain’s circadian timekeeping is able to sync up with these unique body clocks.

“We have, in effect, identified a new mechanism to understand how our body clocks align to the external environment,” said Professor Qing-Jun Meng from the University of Manchester. “The clocks have evolved to prepare you for predictable rhythmic changes in the environment.”

And it’s here, in the “predictable rhythmic changes” that holds the key to how exercising at the same time can shield from musculoskeletal decline.

“Our results showed that physical activities in the morning, associated with daily patterns of sleep/wake cycle, convey timing information from the light-sensitive central clock in the brain to the weight-bearing skeletal tissues,” said Meng. “In effect it’s telling your skeletal system it’s time to wake up.

“But when this alignment is uncoupled with the brain, then, like in other organs and tissues, it can result in adverse impacts on your physical health. If you are constantly changing the time you exercise, you may be more prone to this desynchronization.”

In a mouse model, the scientists made mice exercise on a treadmill during what would usually be their resting time, to demonstrate how unpredictable activity results in an acceleration of bone and cartilage deterioration.

“While we are standing and moving around during the day, water is pressed out of intervertebral disks in our spine as well as the cartilage in hips and knees, making us slightly shorter by the end of the day,” said lead author Michal Dudek, from The University of Manchester. “This causes increase in osmolarity of the tissue because the same amount of minerals is now dissolved in less water so the actual concentration increases. Cells sense this change in osmolarity and synchronize the clocks within these skeletal tissues.

“The water comes back at night when we rest and osmolarity decreases, though this direction of change had no effect on the clock,” he added.

Although a mice model, joint and disk makeup, as well as other physiological aspects, suggests a similar result would be seen in a human trial. And the result was clear: Exercising at the same time each day allows for the systems to align and the mechanisms of the circadian clock to best benefit bones and joints.

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

However, Meng also noted that even if you mix up when you exercise, but establish some sort of a pattern overall, “your body clocks will eventually realign with each other and you will adapt to it.”

“And our work showed that clocks in skeletal tissues of older animals remain responsive to daily patterns of exercise,” he added. “As such, walking groups organized for older people could be more beneficial for their health if they happen at a similar time every day.”

It could also help international athletes, who frequently cross time zones, to better protect themselves against injuries.

Exercise, of course, has many well-studied health benefits, including a direct link to bone health, with just a 3% improvement reducing hip fracture rates by 45% in older adults.

“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 day might bring added benefits for people with arthritis,” said Donaldson. “This is an important discovery because it could help us to develop more targeted treatments for musculoskeletal conditions such as arthritis using exercise and physical activity.”

The research was published in the journal Nature Communications.

Source: University of Manchester

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