Caffeine in Competition: Between Boost and Bellyache

Caffeine in Competition: Between Boost and Bellyache – A Guest Article by Philipp Hofmann

Caffeine is a double-edged sword for me. In everyday (training) life, it’s often indispensable – especially during the dark winter months, when motivation lies somewhere between espresso and the snooze button. In races, though, things get more complicated. The longer the distance, the more I ask myself: How much caffeine really helps – and when does it backfire? I still clearly remember my first caffeinated gel during a triathlon. The effect came fast – my legs felt lighter, my mind sharper. Then, on the run course, came the crash: stomach cramps, nausea, struggle instead of flow. Since then, I’ve become more cautious. Caffeine is no longer a no-brainer for me, but part of a finely tuned strategy – especially on middle distances.

Why Caffeine?

The benefits of caffeine in endurance sports are well documented: it blocks adenosine receptors, delaying the feeling of fatigue and lowering perceived exertion. Studies show that caffeine can improve both endurance performance and reaction time – regardless of training level. It can also stimulate fat metabolism, which can play a role in longer events. And: caffeine increases alertness and focus – sometimes even euphoria. I usually feel it within minutes – like an internal switch turning on.

How fast does caffeine work?

Scientifically, the so-called plasma peak – the time of the highest caffeine concentration in the blood – occurs between 30 and 90 minutes after intake. However, subjective effects like alertness or increased motivation can kick in much sooner. Some studies mention effects as early as 5 to 15 minutes. That aligns with my own experience – especially when I take a caffeinated gel before the start.

Timing

Caffeine has a half-life of about 3 to 6 hours, depending on individual metabolism. This means: after this time, about half of the ingested caffeine is still in the system. Under physical stress, this process seems to speed up – especially relevant for long-distance athletes who need to dose over many hours.

Personally – weighing around 85 kg and racing middle distances – the following plan works well for me:

100 mg of caffeine right before the start
another 100 mg on the bike, around kilometer 40
optionally, another 60–100 mg shortly before the end of the bike leg

This gives me a solid boost at the beginning and a second peak during the tough part of the bike leg. For sprint distances, I skip caffeine entirely – the effort is too short and explosive, adrenaline is enough. For a half marathon, for example, it makes sense to take caffeine before the start, since the race duration isn’t too long.

How much caffeine is effective?

The recommended race-day dose, according to studies, is between 3 and 6 mg of caffeine per kilogram of body weight. For 85 kg, that’s 255 to 510 mg – quite a range. But I stay below this in competition, because I know: my stomach doesn’t always cooperate. In theory, more is possible – in practice, I have to weigh performance against gut tolerance.

Stomach issues while running – where’s the risk?

The run segment is the most critical phase for many triathletes when it comes to the gastrointestinal tract. Why? During running, blood flow shifts toward the muscles, leaving the stomach less oxygenated and more sensitive to irritants – especially sugar, caffeine, and high osmolarity (i.e., highly concentrated gels). Add heat, jostling, and dehydration – a dangerous mix. I’ve experienced several races where caffeine gels during the run caused nausea and stomach pain. Since then, I consistently avoid them. I’d rather have a steady run without crashes than risk a final push that ends in a portable toilet.

What form works best?

I mostly rely on gels – they’re easy to time, dose, and consume on the go. Sometimes I grab a good old cola during the final run phase – a classic during long rides, both for the sugar and the caffeine. In training sessions, I regularly test how my body reacts to different combinations. Caffeine alone is rarely the problem – it’s the mix of heat, sugar, lactate, and movement that matters.

Carb Fuel 50g — Carbs Fuel Original Gel 50 with caffeine

What about longer distances?

Even though I haven’t done a full Ironman yet, I help my wife plan her fueling for such races – and caffeine definitely plays a role. The challenge here: the GI tract is under stress for hours. Caffeine intake must be carefully dosed, evenly spread, and ideally combined with enough fluids. A typical protocol might look like this:

caffeine intake about 30 minutes before the start (e.g., 60–100 mg)
on the bike, roughly every 90 minutes (e.g., 100 mg via gels)
if tolerated well, a gentle push in the late run phase (e.g., via cola at aid stations)

The key: test everything during training. And better to underdose than risk your stomach revolting.

Caffeine withdrawal before race day – worth it?

Some studies suggest that short-term caffeine withdrawal (3–7 days) may increase caffeine sensitivity in competition. Others show no significant difference – especially in athletes who regularly consume moderate caffeine. I’ve tried it – five days without coffee, tea, or cola. The result? Headaches, bad mood, no clear performance gain. Since then, I skip withdrawal experiments and at most slightly reduce intake during race week. Because struggling through caffeine withdrawal during tapering doesn’t help anyone.

Conclusion: Caffeine isn’t the enemy – but it’s no hero either

Caffeine can noticeably improve performance – if used correctly. For me, it’s a valuable tool in middle-distance races, but not a miracle cure. The balance between boost and tolerance is individual – and above all, it should be: trained. I skip it completely in sprints, use it moderately in middle-distance events, and deliberately avoid it during the run segment. And long-distance? That’s a new challenge – but one where caffeine will certainly have its place, with respect, strategy, and maybe a sip or two of cola in the final kilometers.

Image credits:

Cover photo: Philipp Hofmann, photographed by Marcel Hilger and Carla Nagel.

Figure 1: Carbs Fuel, Caffeine Gel.

Philipp Hofmann

Philipp holds a Master's degree in Sports Science with a focus on Sports Medicine and Diagnostics. He works as a triathlon and endurance coach, as well as a bike fitter. Combining scientific expertise, personalized coaching, and biomechanical knowledge, he provides holistic support for athletes. Philipp has also been actively involved in competitive sports at national and international levels since childhood. This gives him not only extensive experience coaching both professional and amateur athletes but also a wealth of personal insight that he brings to his everyday work.