When Should You Start Fuelling on a Long Ride? The 90-Minute Mark Most Athletes Get Wrong

A rider feels strong at the 75-minute mark. Heart rate is settled, cadence is steady, the ride is moving. They reach into a pocket, find a gel, and decide they don't need it yet. Fifteen minutes later, the legs feel heavier. The heart rate has crept up at the same effort. By the 110-minute mark, they're doing math on whether they brought enough food to finish without crawling home.

That window — somewhere between 75 and 110 minutes — is where a lot of long rides quietly fall apart. The athlete didn't bonk. They didn't run out of energy in the dramatic, lights-go-out way the word implies. They just slipped into a state where the body started rationing, and the second half of the ride was decided by what they did, or didn't do, in the first 60 minutes.

What Your Glycogen Stores Are Actually Doing

Endurance athletes carry roughly 400-500 grams of carbohydrate as muscle and liver glycogen, depending on training status, recent diet, and body size. At moderate-to-hard intensity — call it tempo, or steady Z3 — a trained athlete oxidizes carbohydrate at roughly 2-3 grams per minute (Coyle, 1986). That math gives somewhere between 90 and 150 minutes before stored carbohydrate becomes a meaningful constraint on output.

The numbers are a range, not a line. Faster efforts burn through glycogen faster. Cooler conditions slow the rate slightly. A well-fed start raises the ceiling. But the pattern holds across most everyday training. Under 90 minutes, your stores cover the work. Past 90 minutes, the question stops being "can I get away without fuelling?" and starts being "how much have I already lost by waiting?"

Why "When" Matters More Than "How Much"

Most fuelling advice treats carbohydrate as a volume problem — 60g per hour, or 90g per hour, or whatever number applies. Volume matters, but it's the second decision. The first decision is when to start. And the timing matters because fuelling has a physiological lag.

Carbohydrate ingested during exercise takes 15-20 minutes to begin contributing meaningfully to oxidation, with full effect closer to 30 minutes (Jeukendrup, 2014). If you wait until you feel a drop, you're already on the back foot. The gel taken at minute 95 isn't supporting work until minute 115 or beyond. By then, glycogen has dropped further, perceived effort has climbed, and the rest of the ride is being run from a deficit you're trying to climb out of.

This is where the 90-minute window becomes practical advice. Starting fuelling at the 30-45 minute mark, with a small but consistent stream of carbohydrate, means by minute 75 the body is already running on a mix of stored glycogen and exogenous fuel. The transition into the second hour is invisible. The third hour stays on the table.

The First Hour Is Where the Buffer Gets Built

The most common error among everyday endurance athletes isn't undershooting carbs per hour. It's starting late. Many athletes treat the first hour as a warm-up where fuel "isn't necessary yet." Physiologically, that's true if the ride is going to end at 60 minutes. If it's going past 90, the first hour is where you build the buffer that decides whether the second half feels like training or like survival.

A practical version: on any ride scheduled past 90 minutes, plan to take in 30-40 grams of carbohydrate in the first 60 minutes. Spread it across the hour rather than front-loading. Use a drink with carbohydrate in it rather than relying on solid food alone — a sustained, low-volume carbohydrate stream is easier on the gut than periodic gels and matches the absorption rate the body can actually use (Burke, 2010).

This isn't aggressive fuelling. It's modest, consistent fuelling, started before the body asks for it. The athletes who fuel this way rarely talk about hitting walls. The same logic underpins our piece on why you're still bonking on long rides — bonking is almost always a timing problem before it's a volume problem.

Building the 90-Minute Habit Into How You Ride

The way to make this stick is to anchor fuelling to time, not feel. A simple trigger: every 20 minutes from the start of the ride, take a sip of a carbohydrate drink. By the 60-minute mark, you've taken in 30-40 grams without thinking about it. By 90 minutes, you've had two full bottles' worth of intake spread evenly, and the body has been running on a mix of stored and incoming fuel since the first hour.

In Canadian conditions specifically, this rhythm matters more in cool weather, not less. A 5°C ride doesn't trigger thirst the way a 25°C ride does, and athletes routinely under-drink — and under-fuel — on cooler training days. The heart rate is still climbing, the glycogen is still depleting, but the reminder cues are weaker. The 20-minute timer is a way to override that. Spring rides on the BC coast and early-season Ontario weekends are where this habit gets built or lost for the year.

The 90-minute mark isn't a wall to be feared. It's a hinge — the point where a ride either continues at the level it started, or quietly downgrades because of decisions made an hour earlier. The athletes who fuel before the hinge spend the second half of their long rides riding their plan. The athletes who wait spend it managing the consequences. The choice is made earlier than most people realize.