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What Is Creatine Monohydrate & How Does It Work? | The Science

Reading Time: 6 minutes

Written by Liam Darville

Creatine Monohydrate (CrM) is one of the most well-researched supplements in fitness, shown by ~70% of studies to be a significant ergogenic aid (improves performance) to various exercise protocols. Although, most people believe effects are narrowed down to ‘creatine makes you bigger’ and ‘creatine helps you retain water’.

Whilst these will occur as part of supplementation, there is so much more to this underrated nitrogenous compound than simple cellular swelling.

The Science Behind Creatine

Phosphocreatine (PCr) & ATP (Energy)

Creatine is a nitrogenous compound stored in the muscle of mammals and fish, ~95% within skeletal muscle (making animal meat a good source). Within humans, 60% of this is stored as phosphocreatine (PCr) and 40% as creatine.

creatine food source red meat

For maximal or supramaximal exercise, the body utilises the anaerobic energy systems. This consists of stored ATP (the bodies energy source), the ATP-PCr system and the anaerobic glycolytic system.


Performing exercise at this intensity does not allow enough time to generate energy (ATP), utilising the more sustainable aerobic (with Oxygen) pathways. An instant source is required. This is where creatine comes into play. Phosphocreatine (PCr) is responsible for the resynthesis of ATP (adenosine triphosphate) from ADP (adenosine ddiphosphate), providing a rapid energy source.


Energy is derived when a phosphate is ‘cleaved’ from ATP, the breaking of the bond releasing energy and leaving ADP. The creatine kinase enzyme facilitates a reaction between ADP and phosphate to resynthesize (re-create) ATP. Both stored ATP and PCr are 88-100% depleted following 5-8s of maximal effort, it takes 30-60s for ~50% recovery and ~5 minutes to fully recover.

Why Supplement With Creatine If Our Body Produces It?


By supplementing with CrM we can increase the availability of body creatine stores from 125mmol.kg to 160mmol.kg, enhancing our ability to both produce and sustain peak power output, time to exhaustion and repeated maximal efforts, as well as the rate of force development i.e. how quickly we can generate force.


An added bonus is that by exposing ourselves to this greater level of creatine, we elicit a faster resynthesis of PCr, allowing a far enhanced recovery of our anaerobic system.


Benefit #1 | During anaerobic exercise (resistance training) there is an accumulation of metabolites such as lactate and H+ ions. The accumulation of H+ ions will lead to the inhibition of energy production and a lowered ability to perform optimally.


Benefit #2 | The removal of these H+ ions during PCr resynthesis, 1 H+ ion consumed for every PCr created. Something for endurance athletes to consider!

Muscle Contractility


Supplementation leads to an increased power and strength. Creatine positively affects our muscles contractile proteins.

creatine contractile proteins

Myosin and actin, found within the sarcoplasmic reticulum (SR) of the skeletal muscle, bind to produce muscle contraction via a process known as the ‘sliding filament theory’.


This occurs when Calcium is released in the sarcoplasmic reticulum, binding with troponin to move tropomyosin proteins, uncovering myosin binding sites. Actin and myosin can then bind and ‘contract’ in a process known as cross-bridging.


But why is this important?

A good question – creatine increases the calcium uptake in SR, improves myosin heavy chain and actin protein synthesis and so promotes a more rapid, stronger contraction of the muscle.


And what does this mean for me?

This means a more explosive lift, an ability to perform maximal lifts more frequently, a faster recovery, and an increased training volume – all of which lead to new PB’s!

Lean Body Mass


CrM has been shown to aid maintenance of lean body mass (LBM) and increases the cross-sectional diameter of muscle fibres, particularly Type II fibres. Type II fibres are those responsible for heavy and explosive lifting. Increase these and musculature will be larger and more defined.

creatine hypertrophy

Muscle hypertrophy (growth) requires the branch chain amino acid (BCAA) leucine, without it, anabolism (muscle building) cannot occur, hence leucine is known as the ‘anabolic trigger’.


Literature has suggested that CrM can lower leucine oxidation and breakdown, increasing its availability and the retention (and possibly growth) of muscle – a definite bonus when ‘cutting’. CrM has been linked to an increased expression (activity) of the anabolic hormone insulin-like growth factor (IGF-1) further aiding muscle retention.

What drives this retention of nutrients?


The much maligned ‘water retention’. The ‘swelling’ of cells with creatine intake is due to an influx of water. However, it is not just water that is drawn to the cells. CrM causes an increased osmotic pull of cells, drawing in vital nutrients alongside the water e.g. Leucine.


The influx of water to cells has also been linked with improved hydration, prolonging exercise capacity.



As we have mentioned before, recovery is enhanced with supplementation. Research highlighting a decreased muscle catabolism (muscle breakdown), allowing for an improved repair of damaged tissue.

creatine for recovery

Muscle damage, particularly exercise induced muscle damage (EIMD), is believed to accelerate muscle degradation, resulting in a ‘leakage’ of muscle proteins (such as creatine kinase) into the bloodstream, blunting glycogen resynthesis and subsequent high-intensity exercise.


Creatine can limit EIMD. This is achieved through an improvement in the stability of the cellular phospholipid membranes, preventing ‘leakages’ due to a more robust structure. Interestingly, in studies involving older populations, Creatine has been shown to delay muscle atrophy (wastage) linked to sarcopenia, increasing muscle retention.

Side Effects/Safety


In healthy subjects, creatine supplementation has been shown to have no adverse effects on renal function or endocrine enzyme activity.


The major side effects seem to occur in the form of diarrhoea and gastrointestinal distress, generally during a loading phase and this needs to be monitored upon commencement of supplementation.


Creatine is linked to body weight gain, due to an influx of water into the cells and consequent cell swelling, however, if you’re in a calorie deficit and you do not undertake a ‘loading phase’ of 20g per day, then weight gain is highly unlikely. So should CrM be used in a cutting cycle? In short, yes, and we are about to delve into why.

creatine loading phase

Take Home Points


Creatine aids muscle retention, lean body mass and muscle growth

Creatine is critical for strength and power athletes

Creatine helps endurance athletes, buffering H+ ions and increasing ability to produce peak power output (sprint finish)

Creatine increases muscle contractility – useful in all athletic pursuits

Creatine aids recovery

✓ ‘Water retention’ actually has many health benefits

For aging populations CrM may blunt muscle wastage




Our articles should be used for informational and educational purposes only and are not intended to be taken as medical advice. If you’re concerned, consult a health professional before taking dietary supplements or introducing any major changes to your diet.

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