Tag: muscle injury

Categories : Exercise Injury & TraumaTags :

Everything We Thought About Running Injury Development Was Wrong, Study Shows

On By ModernMedia
Photo by Barbara Olsen on Pexels

A new study from Aarhus University turns our understanding of how running injuries occur upside down. The research project, published in The BMJ, is the largest of its kind ever conducted and involves over 5000 participants. It shows that running-related overuse injuries do not develop gradually over time, as previously assumed, but rather suddenly – often during a single training session.

“Our study marks a paradigm shift in understanding the causes of running-related overuse injuries. We previously believed that injuries develop gradually over time, but it turns out that many injuries occur because runners make training errors in a single training session,” explains Associate Professor Rasmus Ø. Nielsen from the Department of Public Health at Aarhus University, who is the lead author of the study.

The study followed 5205 runners from 87 countries over 18 months and shows that injury risk increases exponentially when runners increase their distance in a single training session compared to their longest run in the past 30 days. The longer the run becomes, the higher the injury risk.

Incorrect guidance for millions of runners

According to Rasmus Ø. Nielsen, the results cast critical light on how the tech industry has implemented so-called “evidence.” Millions of sports watches worldwide are equipped with software that guides runners about their training – both for training optimisation and injury prevention.

However, the algorithm used for injury prevention is built on very thin scientific grounds, according to Rasmus Ø. Nielsen.

“This concretely means that millions of runners receive incorrect guidance from their sports watches every day. They think they are following a scientific method to avoid injuries, but in reality they are using an algorithm that cannot predict injury risk at all,” he says.

Non-existing evidence behind guidance

The current algorithm, called “Acute:Chronic Workload Ratio” (ACWR), was introduced in 2016 and is now implemented in equipment from companies that produce sports watches, while organisations and clinicians, such as physiotherapists, also use the algorithm.

The ACWR algorithm calculates the ratio between acute load (last week’s training) and chronic load (average of the past 3 weeks). The algorithm recommends a maximum 20% increase in training load to minimise injury risk.

According to Rasmus Ø. Nielsen, the algorithm was originally developed for team sports and was based on a study with 28 participants. Due to the few participants in the study combined with data manipulation, the evidence base for using the algorithm to prevent running injuries is therefore “non-existent.”

Realtime guidance

The research team has therefore worked for the past eight years to develop a new algorithm that will be much better at preventing injuries for runners.

Rasmus Ø. Nielsen emphasises that he and the other researchers behind the study have no commercial interests in launching a new algorithm as a potential replacement for a method he himself criticises.

The algorithm will be made freely available to runners, companies, clinicians and organisations who can use it actively to guide training and injury prevention.

Rasmus Ø. Nielsen hopes that the new insights will be implemented in existing technology.

“I imagine, for example, that sports watches with our algorithm will be able to guide runners in real-time during a run and give an alarm if they run a distance where injury risk is high. Like a traffic light that gives green light if injury risk is low; yellow light if injury risk increases and red light when injury risk becomes high,” explains Rasmus Ø. Nielsen.

Source: Aarhus University

Categories : Injury & Trauma Metabolic DisordersTags :

Time of Injury Matters: Circadian Rhythms Affect Muscle Repair

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Photo by Mat Napo on Unsplash

Circadian rhythms doesn’t just dictate when we sleep — it also determines how quickly our muscles heal. A new Northwestern Medicine study in mice, published in Science Advances, suggests that muscle injuries heal faster when they occur during the body’s natural waking hours.

The findings could have implications for shift workers and may also prove useful in understanding the effects of aging and obesity, said senior author Clara Peek, assistant professor of biochemistry and molecular genetics at Northwestern University Feinberg School of Medicine.

The study also may help explain how disruptions like jetlag and daylight saving time changes impact circadian rhythms and muscle recovery.

“In each of our cells, we have genes that form the molecular circadian clock,” Peek said. “These clock genes encode a set of transcription factors that regulate many processes throughout the body and align them with the appropriate time of day. Things like sleep/wake behaviour, metabolism, body temperature and hormones — all these are circadian.”

How the study was conducted

Previous research from the Peek laboratory found that mice regenerated muscle tissues faster when the damage occurred during their normal waking hours. When mice experienced muscle damage during their usual sleeping hours, healing was slowed.

In the current study, Peek and her collaborators sought to better understand how circadian clocks within muscle stem cells govern regeneration depending on the time of day.

For the study, Peek and her collaborators performed single-cell sequencing of injured and uninjured muscles in mice at different times of the day. They found that the time of day influenced inflammatory response levels in stem cells, which signal to neutrophils — the “first responder” innate immune cells in muscle regeneration.

“We discovered that the cells’ signalling to each other was much stronger right after injury when mice were injured during their wake period,” Peek said. “That was an exciting finding and is further evidence that the circadian regulation of muscle regeneration is dictated by this stem cell-immune cell crosstalk.”

The scientists found that the muscle stem cell clock also affected the post-injury production of NAD+, a coenzyme found in all cells that is essential to creating energy in the body and is involved in hundreds of metabolic processes.

Next, using a genetically manipulated mouse model, which boosted NAD+ production specifically in muscle stem cells, the team of scientists found that NAD+ induces inflammatory responses and neutrophil recruitment, promoting muscle regeneration.  

Why it matters

The findings may be especially relevant to understanding the circadian rhythm disruptions that occur in aging and obesity, Peek said.

“Circadian disruptions linked to aging and metabolic syndromes like obesity and diabetes are also associated with diminished muscle regeneration,” Peek said. “Now, we are able to ask: do these circadian disruptions contribute to poorer muscle regeneration capacity in these conditions? How does that interact with the immune system?”

What’s next

Moving forward, Peek and her collaborators hope to identify exactly how NAD+ induces immune responses and how these responses are altered in disease.

“A lot of circadian biology focuses on molecular clocks in individual cell types and in the absence of stress,” Peek said. “We haven’t had the technology to sufficiently look at cell-cell interactions until recently. Trying to understand how different circadian clocks interact in conditions of stress and regeneration, is really an exciting new frontier.”

Source: Northwestern University

Categories : Injury & TraumaTags :

Massage Heals Injured Muscle by Getting Immune Cells Out

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Photo by Andrea Piacquadio from Pexels

While massage has been used to treat muscle pain and injury for thousands of years, it is only now that a study has scientifically confirmed that it improves recovery and strength gains. Intriguingly, the mechanism behind this is mechanically clearing out of immune cells from the injury site after they have done their job.

Using a custom-designed robotic system massage system for mice, the team found that this mechanical loading (ML) rapidly clears immune cells called neutrophils out of severely injured muscle tissue. This process also removed inflammatory cytokines released by neutrophils from the muscles, enhancing the process of muscle fiber regeneration. The research is published in Science Translational Medicine.

“Lots of people have been trying to study the beneficial effects of massage and other mechanotherapies on the body, but up to this point it hadn’t been done in a systematic, reproducible way. Our work shows a very clear connection between mechanical stimulation and immune function. This has promise for regenerating a wide variety of tissues including bone, tendon, hair, and skin, and can also be used in patients with diseases that prevent the use of drug-based interventions,” said first author Bo Ri Seo, PhD.

Dr Seo and her colleagues previously found in mouse studies that mechanical massage of injured muscles doubled the rate of muscle regeneration and reduced tissue scarring over the course of two weeks. With a new device inspired by soft robotics, the researchers sought to confirm these results. They found that the greater the force applied, the stronger the injured muscles became.

In vitro experiments suggested that neutrophil-secreted factors stimulate the growth of muscle cells, but the prolonged presence of those factors impairs the production of new muscle fibres. In vivo testing showed that stronger muscle fibre types predominated in treated, injured muscle types. Depleting neutrophils in mice after the third day resulted in greater strength recovery, indicating that they are important in the initial recovery period but removing them from the injury site early leads to improved muscle regeneration.

“The idea that mechanics influence cell and tissue function was ridiculed until the last few decades, and while scientists have made great strides in establishing acceptance of this fact, we still know very little about how that process actually works at the organ level. This research has revealed a previously unknown type of interplay between mechanobiology and immunology that is critical for muscle tissue healing, in addition to describing a new form of mechanotherapy that potentially could be as potent as chemical or gene therapies, but much simpler and less invasive,” said Don Ingber, MD, PhD, founding director of the Wyss Institute for Biologically Inspired Engineering at Harvard.

Source: Wyss Institute for Biologically Inspired Engineering at Harvard