Harris et al. 1992: The Landmark Creatine Loading Study That Started It All

TL;DR — Harris et al. 1992

In 1992, Roger Harris and colleagues published a study in Clinical Science that fundamentally changed sports nutrition. They demonstrated for the first time in humans that oral creatine monohydrate supplementation could significantly increase the amount of creatine stored in skeletal muscle — by approximately 20% (RC et al., 1992) . This single finding launched an entire field of research and turned creatine into the most studied sports supplement in history.

Study Background and Rationale

Before 1992, creatine was well-known in biochemistry as a component of the phosphocreatine energy system. Scientists understood that muscles use phosphocreatine to rapidly regenerate ATP during high-intensity efforts. However, no one had systematically investigated whether consuming creatine orally could actually raise muscle creatine levels in healthy humans.

Harris and his co-authors — Kerstin Soderlund and Eric Hultman at the Karolinska Institute in Sweden — set out to answer this fundamental question. Their research was published in Clinical Science (volume 83, 1992) under the title “Elevation of creatine in resting and exercised muscle of normal subjects by creatine supplementation.”

Study Design and Methodology

The study was conducted across multiple experiments involving 17 healthy volunteers. The researchers used muscle biopsy samples from the vastus lateralis (quadriceps) to directly measure creatine and phosphocreatine concentrations before and after supplementation.

Supplementation protocol:

• Participants consumed 5g of creatine monohydrate dissolved in warm liquid
• Doses were taken 4 to 6 times per day
• The supplementation period lasted between 2 and 6 or more days
• Blood samples tracked plasma creatine levels throughout

Key methodological strengths:

• Direct muscle biopsies provided definitive data on intramuscular creatine levels
• Multiple experiments tested different variables (dose timing, exercise effects, individual variation)
• Measurements at both resting and exercised muscle sites allowed comparison of uptake rates

Key Findings

The results were clear and significant:

1. Muscle creatine stores increased by approximately 20%

Oral supplementation with 20g per day of creatine monohydrate for roughly 6 days elevated total muscle creatine content (free creatine plus phosphocreatine) by an average of 20 mmol/kg dry muscle. This represented roughly a 20% increase over baseline values.

2. Individuals with lower baseline creatine showed the greatest uptake

One of the most important observations was that participants who started with the lowest muscle creatine levels experienced the largest increases. This finding had major implications: vegetarians, vegans, and individuals with naturally low creatine stores stood to benefit the most from supplementation.

3. Exercise enhanced creatine uptake in working muscles

Muscles that were exercised during the supplementation period showed greater creatine accumulation than resting muscles. This suggested that muscle activity — perhaps through increased blood flow or metabolic demand — facilitated creatine transport into cells.

4. Plasma creatine levels peaked rapidly after ingestion

Blood creatine concentrations rose sharply within one hour of ingestion and returned toward baseline within 2 to 3 hours, establishing the pharmacokinetics of oral creatine dosing.

Why This Study Matters

The Harris 1992 paper is considered the genesis of modern creatine research for several reasons:

It established proof of concept. Before this study, the idea that a dietary supplement could meaningfully alter muscle biochemistry was not well supported for creatine. Harris and colleagues provided the first direct, biopsy-confirmed evidence.

It defined the loading protocol. The 20g/day dosing regimen used in this study became the standard creatine loading protocol. Later work by Hultman et al. (1996) confirmed that a lower dose of 3g/day for 28 days achieves the same endpoint, but the Harris loading protocol remains the fastest path to saturation (E et al., 1996) .

It inspired hundreds of follow-up studies. The 500+ peer-reviewed creatine studies that exist today can trace their origins to this foundational work. The ISSN Position Stand by Kreider et al. (2017) cites Harris 1992 as a seminal reference in creatine science (RB et al., 2017) .

Limitations

No study is without limitations, and it is important to acknowledge those of the Harris 1992 paper:

• Small sample size: Only 17 subjects were studied across all experiments, limiting statistical power
• No placebo control group: The study was not designed as a randomized controlled trial with a placebo arm
• Short duration: The supplementation period was only a few days, leaving long-term effects unexplored
• Homogeneous population: Participants were healthy, young adults — applicability to elderly or clinical populations was not assessed

These limitations were addressed by subsequent research over the following decades, which consistently confirmed and extended the original findings.

Practical Implications for You

The principles established by Harris et al. in 1992 still guide creatine supplementation today:

1. Loading works: If you want to saturate your muscles quickly, 20g/day (split into 4 doses of 5g) for 5 to 7 days is effective
2. Low-dose loading also works: If you prefer a gentler approach, 3 to 5g/day will reach the same saturation point in about 4 weeks
3. Exercise enhances uptake: Taking creatine around your training sessions may improve muscle absorption
4. Carbohydrates boost absorption: Later research by Green et al. (1996) showed that consuming creatine with carbohydrates increased uptake by 60% due to insulin-mediated transport (AL et al., 1996)
5. Individuals with lower baseline stores benefit most: Vegetarians, vegans, and those with low dietary creatine intake may see the most dramatic results

Full Citation

Harris RC, Soderlund K, Hultman E. Elevation of creatine in resting and exercised muscle of normal subjects by creatine supplementation. Clinical Science. 1992;83(3):367-374. doi:10.1042/cs0830367

Sources & References

This article is based on the primary research paper published in Clinical Science (1992) and contextualized with findings from Hultman et al. (1996), Kreider et al. (2017), and Green et al. (1996). All citations link to PubMed-indexed publications.

Further Reading

• creatine dosage guide
• creatine monohydrate
• creatine for muscle building
• creatine for brain health
• how creatine works
• creatine loading phase