Written by Physiotherapist and KIC Run Expert, Alana Murrihy
While the popularity of running in Australia (and around the world) has been soaring over the past few years, the number of runners I see in the clinic as a physiotherapist has also been steadily increasing. One thing in common most of my runners have when they first present - they are under-hydrating and under-fueling.
Running Performance
Electrolytes - including sodium, potassium and magnesium - are critical for running (and general athletic) performance. These key electrolytes are essential for maintaining fluid balance, nerve function, and muscle contractions, with sodium being the most crucial for endurance activities like running. Sodium is vital to maintain hydration and fluid balance by helping your body to retain water. During running or exercise, especially in heat or over longer distances, you lose fluid through sweat. Without adequate sodium, drinking plain water can actually dilute your blood sodium levels (a condition called hyponatremia), which not only impacts performance but is also life-threatening. Sodium and other electrolytes also help with the absorption of water into the bloodstream and tissues. This is why just drinking water may not be enough during long runs—electrolytes ensure that water is effectively absorbed and utilised by your body.
Sodium is also the primary electrolyte lost in sweat, and losing too much sodium can lead to early fatigue, nausea, dizziness, confusion, and a drop in performance output. Some people are “salty sweaters” and lose more than others, so their need for sodium replacement is even higher. Electrolytes are also essential for overall metabolic function, due to their role in maintaining the body’s acid-base balance. During intense exercise, the body produces lactic acid, and electrolytes help buffer the acid to prevent the blood from becoming too acidic, which could lead to increased muscle fatigue and soreness. Sodium also plays an essential role in muscle contraction and nerve function, as it enables electrical signals to travel between nerves and muscles. When you’re depleted, you may experience muscle cramps, weakness, increased fatigue or poor coordination because the muscles can no longer contract and relax properly. During running, sodium and potassium helps muscles function efficiently, reducing the risk of cramps and improving endurance.
Proper electrolyte balance can also help overall running performance by sustaining energy levels and boosting endurance. When electrolytes are replenished during a run, your body can maintain its optimal functioning, including temperature regulation and energy production. As a result, your performance can improve, and you can run longer and more efficiently. Sodium and other electrolytes also help to regulate blood volume, which in turn helps transport nutrients and oxygen to muscles. By preventing dehydration and maintaining adequate blood volume, electrolytes help delay the onset of fatigue, ensuring that your muscles have the nutrients they need to perform for longer periods.
Injury Prevention
So as we’ve touched on above, electrolytes play a low-key but super important role in keeping your body running smoothly, and staying injury free. Electrolytes—especially sodium, potassium, calcium, and magnesium—help regulate muscle contractions. When the levels are off (especially sodium and potassium), muscles can misfire, leading to cramping or spasms mid-run. Cramping increases your risk of pulls or strains—especially in already tight or overworked muscles (like hamstrings, calves, or quads). Electrolytes also help the muscles to contract and relax smoothly. If you’re low on these, muscles may stay tense or fail to “let-go” as they should. This can lead to tendon overload or micro-tears, especially during high-impact or long-distance runs.
Muscle Function and Fatigue
Electrolytes also play an essential role in maintaining nerve function and coordination. Your brain and muscles communicate via electrical signals, which rely on electrolytes to function. When you’re depleted, these signals can become delayed or erratic, making you more prone to poor running form or technique, missteps, joint misalignment or stumbling. These seemingly small issues though can compound and become overuse injuries (like stress fractures, shim splints, or tendinosis).
Regular use of electrolytes can also help to prevent fatigue-based injuries. Electrolyte imbalances can cause early fatigue, leading to sloppy running form. Poor form can equal more strain on joints, tendons and muscles, increasing your risk of overuse injuries or falls. Due to sodium's role in helping your body to retain fluid, it also helps to keep your joints and tissues well-lubricated. Dehydrated tissues are more likely to be stiff, sticky or prone to tearing, especially when under stress.
Temperature Regulation
Sodium and other electrolytes also play a role in regulating body temperature. If you lose too much sodium through sweat and fail to replenish it, the body’s ability to regulate temperature becomes compromised, increasing the risk of heat-related injuries such as heat exhaustion or heat stroke. These conditions can lead to serious harm, so ensuring you stay hydrated and replenish electrolytes is crucial during hot or intense runs. Electrolytes, particularly potassium and magnesium, are involved in maintaining nerve function, balance, and coordination. Proper nerve signaling ensures that your muscles work harmoniously together and that you maintain balance during physical activities. If electrolytes are deficient, there can be issues with coordination, increasing the likelihood of falls or improper movements that could lead to injuries.
In summary, electrolytes help you stay injury free and running consistently - the holy grail of running progress!
Recovery
Post-run recovery isn’t just about stretching or foam rolling - electrolytes play a huge role in helping your body to recover and be ready for the next session. Here’s some more information on how:
Rehydration & fluid retention: during running, you lose sodium, potassium and other electrolytes through sweat. Replacing just water post-run can dilute your sodium levels, leading to poor fluid absorption and slower rehydration. Sodium helps you to retain the fluids you drink, so that your cells can rehydrate properly instead of just flushing everything out as urine.
Muscle repair & function: potassium & magnesium are key for muscle function and relaxation. After exercise, muscles are slightly damaged (that’s normal!) and need these minerals to reduce muscle soreness, help with protein synthesis, and prevent cramping and muscle tightness. Low electrolyte levels have been shown to lead to slower heading or lingering stiffness or fatigue.
Reducing Delayed-Onset Muscle Soreness (DOMS): while electrolytes don’t completely prevent DOMS, they can lessen its severity by supporting muscle contraction & relaxation, reducing inflammation, and improving blood flow to muscles (which helps to deliver nutrients and remove waste). Magnesium, in particular, helps with muscle relaxation and reduces the buildup of lactic acid, a byproduct of intense exercise that contributes to soreness. By restoring magnesium levels, you can help speed up the recovery process and reduce post-exercise muscle discomfort.
Nervous system recovery: running doesn’t just stress your muscles and joints, but your nervous system too, which relies on a good balance of electrolytes to recover. Replenishing sodium, potassium and magnesium helps to calm the nervous system and prevent symptoms like irritability, headaches, poor sleep and brain fog after hard workouts.
Preventing injury in the next session: if you’re still electrolyte-depleted before your next run or workout, you are at higher risk of cramping, poor coordination or fatigue-based injuries (e.g. strains, tendon flare ups).
Restoring energy balance: electrolytes help with the absorption and transportation of essential nutrients, such as glucose and amino acids, which are essential for muscle repair and energy recovery after exercise. Sodium, in particular, helps with nutrient absorption, ensuring that the body can make use of post-exercise carbohydrates and protein for muscle repair. This ensures your body is ready to fuel itself for the next workout or run.
Preventing overhydration (hyponatremia): while it’s important to hydrate during and post-exercise, consuming too much water without electrolytes can lead to a condition called hyponatremia (or low sodium levels). This can cause symptoms like nausea, headaches, and fatigue, and in severe cases, can be life-threatening. By replenishing both water and electrolytes after a workout, you avoid the risk of overhydration and help maintain optimal sodium levels for recovery.
Reducing inflammation and supporting cellular repair: Electrolytes like calcium and magnesium can help reduce inflammation post-exercise. Calcium plays a role in the contraction and relaxation of muscle fibers, and magnesium has anti-inflammatory properties that can reduce soreness and swelling. This is important for supporting tissue repair and reducing inflammation in muscles and joints after intense physical activity.
Boosting immune function: Intense exercise can temporarily suppress the immune system. Adequate electrolyte intake supports overall cellular function, which can enhance the recovery of the immune cells. Magnesium, in particular, plays a role in immune function, and maintaining proper electrolyte balance can help your body recover from the strain of exercise and reduce the risk of getting sick during the recovery phase.
Optimal nervous system recovery: After prolonged physical activity, the nervous system also needs to recover, especially in the brain and spinal cord, to manage stress and fatigue. Sodium, potassium, and magnesium play a role in the functioning of the central nervous system (CNS) by ensuring the nerves can transmit signals efficiently. Proper electrolyte balance can aid in quicker mental and physical recovery, improving alertness and reducing fatigue post-workout.
Boosting sleep quality: Proper electrolyte balance can also help improve your sleep quality post-exercise. Magnesium, in particular, is known for its ability to promote relaxation and better sleep. Sleep is crucial for muscle repair and recovery, so maintaining adequate magnesium levels after exercise can help improve recovery by allowing your body to rest and heal more effectively overnight.
Here’s a simple recovery protocol you can try for yourself:
- Within 30–60 minutes post-run: Have a salty snack, sports drink, or your Sodii electrolytes along with fluids
- Combine it with protein + carbs for muscle repair.
- If you’re a salty sweater or ran longer than 60–90 minutes: prioritise sodium-rich recovery aka your flavour Sodii flavour or a salty snack.
Benefits of Electrolytes for Runners
✅ Prevent Muscle Cramps
💧 Improve Hydration
⚡ Enhance Endurance & Performance
🛡️ Support Injury Prevention
🧠 Maintain Focus & Coordination
🔁 Aid Post-Run Recovery
🧂 Key Electrolytes to Watch:
Sodium – most critical during and after running
Potassium – helps with muscle recovery
Magnesium & Calcium – support muscle relaxation and nerve function
Tips to Prevent Exercise-Induced Hyponatremia (Low Sodium Levels)
💧 Don’t Overdrink Plain Water
🧂 Include Sodium in Your Hydration
- Aim for products that contain at least 300–500 mg of sodium per litre (Sodii has you covered here!).
🔬 Know Your Sweat Rate & Sodium Loss
⏱️ Always Fuel Wisely, Especially During Long Runs
📊 Balance Fluids with Food Intake
🧠 Recognise Early Symptoms
🏁 Pro Tip:
Post-race hyponatremia is commons so don’t drink tons of plain water immediately after a long run or race. Sip an electrolyte drink or eat a salty snack first.
