Creatine for Endurance Athletes: When It Helps and When It Doesn't

Energy Systems and Where Creatine Fits

Human movement draws from three energy systems: the phosphagen system (ATP-PCr), glycolysis, and oxidative phosphorylation. The phosphagen system dominates during efforts lasting up to roughly 10 seconds, supplying immediate ATP by cleaving phosphocreatine. Glycolysis takes over for efforts lasting 30 seconds to 2 minutes. Beyond that, oxidative metabolism provides the majority of ATP.

Endurance events are overwhelmingly aerobic. A marathon runner operating at 70-85% of VO2max derives more than 90% of their energy from oxidative pathways. A cyclist in a 40-kilometer time trial is similarly reliant on aerobic metabolism. On its face, creatine supplementation should be irrelevant to these athletes. The phosphagen system contributes minimally to steady-state endurance output.

But endurance sports are not always steady-state. This is where the conversation gets more interesting.

The High-Intensity Component of Endurance

Road cycling features attacks, breakaway efforts, and sprint finishes. Cross-country running involves surges on hills. Swimming includes race-pace turns and finishing kicks. Soccer players sprint repeatedly throughout 90 minutes. Even in seemingly continuous events, brief high-intensity bursts occur regularly, and those bursts draw heavily on the phosphagen system.

Tomcik and colleagues (2018) investigated this directly by studying elite kayakers performing repeated sprint efforts typical of competitive paddling. They found that creatine-loaded athletes produced higher peak power outputs across repeated bouts compared to placebo. The finding aligned with what strength and power research had long demonstrated: creatine improves performance in short, intense, repeated efforts. The application to endurance sports is that many endurance competitions contain exactly these kinds of efforts.

Murphy and colleagues (2005) examined creatine supplementation in trained endurance athletes performing high-intensity interval work. Supplemented athletes showed improved work capacity during intervals at 110-150% of VO2max intensity. The authors noted that while continuous submaximal performance was unaffected, the ability to sustain repeated high-intensity efforts was enhanced.

Continuous Endurance: Limited Evidence of Benefit

For purely continuous submaximal exercise, the evidence is less compelling. Cox and colleagues (2002) studied highly trained rowers over 32 days of creatine or placebo supplementation during a training camp. While creatine-supplemented rowers showed increases in lean mass and improvements in interval-based rowing tests, their steady-state endurance measures did not significantly improve.

Engelhardt and colleagues (1998) examined creatine's effect on cycling performance using a protocol that combined a sustained effort with a final high-intensity phase. The creatine group performed better in the high-intensity finishing phase but showed no advantage during the sustained aerobic component. This pattern repeats throughout the literature: creatine assists the anaerobic bursts embedded within endurance contexts but does not enhance the aerobic engine itself.

Stroud and colleagues (1994) tested creatine in middle-distance running events and found minimal benefit for 6-kilometer cross-country performance. The lack of repeated sprint demands in a steady-pace cross-country effort may explain why creatine provided no measurable advantage.

The Weight Gain Tradeoff

Creatine supplementation typically increases body mass by 1-2 kg within the first week, primarily through intracellular water retention. For a powerlifter, this is irrelevant or even desirable. For a cyclist climbing mountains, a runner racing on hilly terrain, or a lightweight rower, the extra mass is a direct performance cost.

The power-to-weight ratio governs performance in gravity-dependent endurance sports. An additional kilogram on a cyclist climbing a 7% gradient at 300 watts represents a measurable speed reduction. Hultman and colleagues (1996) documented this body mass increase consistently across creatine supplementation studies, and the effect is reliable and predictable.

This creates a cost-benefit calculation that is specific to each sport and each athlete. A road cyclist who primarily races flat time trials may be less affected than one who specializes in mountain stages. A triathlete competing in a draft-legal sprint triathlon, where acceleration and surge capacity matter, may find the tradeoff worthwhile. Context determines whether the mass penalty outweighs the power benefit.

Repeated Sprint Ability in Endurance Contexts

The most defensible application of creatine for endurance athletes is in sports requiring repeated high-intensity efforts interspersed with recovery periods. Soccer, field hockey, basketball, and rugby all combine endurance demands with repeated sprints. These are sometimes classified as intermittent sports rather than pure endurance activities, but the aerobic base requirements are substantial.

Mujika and colleagues (2000) studied the effects of creatine on repeated sprint performance in team sport athletes. The supplemented group maintained higher power output across successive sprints compared to placebo. This finding is robust and has been replicated across multiple studies. For athletes in intermittent sports, creatine addresses a genuine performance demand.

The distinction is important: creatine does not make you a better endurance athlete in the aerobic sense. It makes you a better sprinter within an endurance context. Whether that matters depends entirely on the competitive demands of your sport.

Training Adaptations vs. Race Performance

A separate argument for creatine in endurance sports concerns training quality rather than competition performance. Many endurance training programs include high-intensity interval sessions, hill repeats, and tempo work that stress the anaerobic system. If creatine allows an athlete to produce higher power during these training sessions, the long-term training stimulus could be greater, leading to superior aerobic adaptations over time.

This hypothesis has theoretical support but limited direct evidence. Forbes and Candow (2018) discussed the concept in a review of creatine applications beyond traditional strength sports. They noted that improved training quality is a plausible mechanism for indirect endurance benefits but emphasized that prospective studies measuring this effect longitudinally are lacking.

Some endurance coaches have adopted periodic creatine use during high-intensity training blocks, withdrawing it during race periods to shed the water weight. This approach is pragmatic but based on extrapolation rather than direct evidence.

Glycogen Interactions

An intriguing line of research suggests that creatine supplementation may enhance glycogen storage. Robinson and colleagues (1999) found that muscle glycogen supercompensation was greater when creatine was co-ingested with carbohydrates. If this effect is reliable, it could have direct relevance for endurance athletes who depend on glycogen availability during prolonged efforts.

However, subsequent studies have produced mixed results, and the magnitude of any glycogen-sparing or glycogen-loading benefit remains uncertain. Nelson and colleagues (2001) found that creatine supplementation during carbohydrate loading did not significantly enhance cycling endurance. The glycogen hypothesis is interesting but not yet actionable.

Practical Recommendations

The evidence supports a tiered approach to creatine use in endurance sports. For athletes in intermittent sports with significant sprint demands, creatine supplementation is supported by strong evidence. For athletes whose events include decisive high-intensity moments embedded within longer efforts, creatine may provide a competitive advantage during those specific moments. For purely continuous, submaximal endurance athletes, creatine is unlikely to improve aerobic performance and the associated weight gain may be counterproductive.

Athletes should consider their specific event demands, the role of body mass in their performance, and whether their training includes high-intensity components that creatine could enhance. The decision is not binary. Periodized use, timed to training phases that emphasize anaerobic development, may capture the benefits while avoiding the costs during competition.