What muscle soreness actually is
Most of what people call sore muscles is one of three things, and they have different causes.
| Type | What happens |
|---|---|
| Delayed onset soreness | The stiffness that arrives a day after unfamiliar exercise, peaks around 24 to 72 hours, and fades on its own. Associated with microscopic damage to muscle fibres and the inflammatory response that follows, particularly after eccentric work such as running downhill. |
| Cramp | A sudden involuntary contraction that will not release. Most common in the calf and foot, often at night or late in prolonged exercise. |
| Overuse and strain | Persistent, localised, and tied to a specific movement. Unlike the other two this does not resolve by itself and is worth having looked at. |
Soreness that is sharp rather than dull, that follows a specific incident, or that is still there after a week is not ordinary training soreness. That is a reason to see a doctor or physiotherapist rather than to try a product.
What magnesium does in muscle
Magnesium is a mineral the body cannot make and has to take in from food. It works as a cofactor in hundreds of enzyme reactions, including the ones that make ATP — the molecule muscles run on.
Its more specific role is in how muscle contracts and releases. Contraction is triggered by calcium entering the muscle cell. Magnesium acts against calcium at those sites, so it is involved in the relaxation half of the cycle rather than the contraction half. This is the reason low magnesium is associated with cramping and twitching: the signal to contract is easier to trigger and harder to switch off.
That physiology is not in dispute. What it does not establish is that adding more magnesium helps someone whose levels are already adequate — which is a different question, and the one that matters when you are deciding whether to buy something.
Magnesium oil, flakes and Epsom salts
These names describe three different compounds, and the labelling is not always helpful.
Magnesium oil
Not an oil at all. It is a saturated solution of magnesium chloride in water, which feels slippery on the skin and picked up the name for that reason. Usually sold as a spray and applied directly to the area.
Magnesium flakes
The same magnesium chloride in solid form, dissolved into a bath or a foot soak.
Epsom salts
A different compound — magnesium sulfate, not chloride. Long used as a bath soak. Worth knowing it is not interchangeable with the above, though it is often discussed as though it were.
What the evidence does and does not show
Being straight about this is more useful than the alternative.
Reasonably well established: magnesium is essential to normal muscle function, and genuine deficiency is associated with cramping. Correcting a real deficiency, usually through diet or oral supplementation, addresses symptoms caused by that deficiency.
Much less certain: whether magnesium applied to the skin is absorbed in meaningful amounts. The outer layer of skin is specifically built as a barrier, the human studies that exist are small and often poorly controlled, and the results are inconsistent. People report that it helps them. That is worth something, but it is not the same as demonstrated absorption, and anyone telling you the transdermal case is settled is overstating it.
Worth knowing: a warm bath or a foot soak has effects of its own on stiff muscles, independent of what is dissolved in the water. That makes the bath products particularly hard to evaluate.
This page is general information, not medical advice. If you are pregnant, have kidney problems, or take prescription medication, check with your doctor or pharmacist before using magnesium products — magnesium interacts with several common medicines and is cleared by the kidneys.
Getting enough from food
Before reaching for a product, it is worth knowing magnesium is abundant in ordinary food: leafy greens, nuts and seeds — pumpkin seeds and almonds in particular — legumes, wholegrains and dark chocolate. Most people who eat a reasonably varied diet are not deficient.
Where to buy magnesium products in Australia
Mega Health stocks magnesium oil sprays, bath flakes and oral magnesium, and ships across Australia.
Browse magnesium at Mega Health