G'day team,

I really think I've got the hang of this "sensationalist headings thing".. sooo today we'll be chatting about a little condition called Rhabdomyolysis.

You've probably heard of marathon runners dropping dead from dehydration (or overhydration) and heat exhaustion. But this isn't the only way to kill yourself by exercising.

An increasing problem, rhabdomyolysis is a dangerous condition which can be caused by damage to muscles during exercise and has the potential to destroy the kidneys and kill in hours. Today we'll have a chat about the disease, a look at why it's linked to exercise and a bit of a go at the CrossFit community just for fun (and because they're part of the problem here). So without further ado... let's get into it!

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What is Rhabdomyolysis

Rhabdomyolysis (or 'Rhabdo') is a nasty condition where damaged muscle tissue breaks down, leading to the release of debris into the blood. This debris travels to the kidneys where it causes damage and potential shutdown of the organ.

So, let's explore this whole process more and have a look at what we call the "pathophysiology" of the condition.

Step #1 - Muscle Damage

The first step of rhabdo is severe muscle damage and this is obviously where exercise comes in, but you're not getting rushed to the hospital every time you go for a jog or hit the gym. In order to do enough damage to your muscles to get rhabdo you really have to go beyond the limits of healthy exercise. This means long durations of exercise, movements that will cause micro-tears in muscle (such as weight-bearing) and pushing your body to the limit in terms of physical tolerance.

Die-Hards Read This
How this is caused at a cellular level is quite complex, but interesting for those who're interested. Underlying cellular damage along with continued demand for contractions leads to a depletion of cellular ATP, as even aerobic methods of energy production cannot keep up with demands. A loss of ATP results in a failure to keep vital calcium pumps working. With the inability to return calcium to the sarcoplasmic reticulum after muscle contraction we see prolonged contraction and futher exaccerbation of the underlying ATP deficiency. We also lose functionality of plasma membrane NA/ K pumps, and an influx of Na ions which bring free water with them. Unable to hold this extra volume the cell swells and then bursts (lyses) leading to the release of intracellular contents into the extravascular space. If enough cellular debris builds up in the extravascular space it will lead to both local oedema (swelling) and a build up of debris downstream in the intravascular space.

Step #2 - Debris in the Blood

Now we've released the contents of our myocytes (muscle cells) into our blood and we're going to start to see some changes.

• First off, our muscles are broken down and swollen. In order to provide enough fluid for all this swelling we're borrowing from our blood and this can lead to hypovolaemic shock. In essence if we don't have enough fluid left in our arteries and veins then we'll struggle to pump oxygen to all the other organs in our body. This includes our kidneys.

• Next we've just dumped a whole lot of potassium (K) and calcium (Ca) into our blood. High levels of potassium can lead to an inbalance in neurons across our whole body, but most importantly in our heart where it can lead to irregular heart rhythms called arrhythmias. Calcium is an ion our body is quite good at regulating, but not good enough to manage the rapid spike. The body will try to control this spike by pumping calcium from the blood into other muscles or... you guessed it, out through the kidneys.

• Damaged muscle cells will also leak lactic acid, purines and other organic compounds which are acidic. This can lead to a global acidosis (low blood pH) which is a huge problem and one that's usually corrected by the kidneys. Now this poor organ is not only being choked and poisoned but also asked to work overtime. To add to the problems purines are actively 'nephrotoxic', directly damaging the kidneys as they pass through.

• To add to the nephrotoxins, muscle damage will also lead to release of the oxygen-carrying molecule myoglobin. This is perhaps the best known cause of kidney damage in rhabdo, as it was one of the first discovered.

• Finally a pro-clotting and an anti-clotting agent (thromboplastic and plasminogen) are both released from destroyed cells too. The result is widespread activation of clotting factors in our blood, which leads to depletion and a condition called "diseminated intravascular coagulopahty" which is 110% as complicated as it sounds. The upshot? You're now way more prone to bleeding too!

So let's review...

We now have a kidney that's being starved of oxygen due to hypovolaemia, asked to deal with high levels of calcium, overworked to correct a blood pH inbalance and poisoned by myoglobin and purine. Oh and you can't control your bleeding!

Step #3 - Kidney Failure

No shock here!

The kidneys are done for the day and pack up shop.

This puts our patient in a very bad place.

Causes

Now exercise isn't the only thing that can cause extensive muscle injury, in fact it's not even the most common. The most common causes of muscle injury leading to rhabdomyolysis are...

• Crush injuries
• Toxins
• Infection
• Surgery
• Immobilization

Rhabdomyolysis was so closely linke with crush injuries when it was first discovered that it was, for a long time, known simply as 'crush-injury-syndrome'.

But exercise is among the most preventable and in recent years, is the one we've been seeing more and more often. Now the problem here lies quite firmly in the hand of the infamous fitness cult that is CrossFit

CrossFit

Now I'm sure I'm going to make some enemies here and draw a lot of criticism, so I want to make something clear. No group is inherantly bad, no sensible exercise regime is anything but good and CrossFit isn't inherantly evil. It's just that the CrossFit community and those who follow it's mantra are continuousely implicated in unhealthy and often dangerous exercise practices.

But under this name, or in this guise, we see some rather cult-like obsessions with fitness which miss the mark of healthy exercise completely. Among them is the "Uncle Rhabdo" figure which, to some crossfitters, represents a badge-of-honour for exercising till they induce Rhabdomyolysis.

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In some areas the reported cases of Rhabdoy have increased 20-fold between 2005- and 2017 and many people are blaming this unhealthy trend.

So the take home message. Exercise safe! There's no benefit to working till you destroy your kidneys!

Thanks

Thanks for reading team, and as usual feel free to leave any comments below!

Thanks!

-tfc

Resources
UpToDate
The syndrome of rhabdomyolysis: Pathophysiology and diagnosis
Rhabdomyolysis: Pathophysiology, Recognition, and Management
Oxford Textbook of Critical Care (2 ed.)
Medicinenet
Medium - CrossFit's Dirty Little Secret
CrossFit Impulse

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