Indoor trainer training in winter: how to stay fit

The indoor trainer has a bad reputation. People picture it as boring, stuffy, and a bit punishing. But it's the tool that keeps your fitness on track from October to March, when the weather and the short days decide for you.

The good news: you don't need a complicated plan to get through it. A few principles backed by research are enough: don't stop, keep cool, don't trust the numbers blindly, and don't assume there's only one correct way to split your intensity.

What you lose when you stop

The real enemy of winter isn't the cold. It's the break in training. A key review on detraining (Mujika and Padilla, 2000) shows that after more than 4 weeks of insufficient training, athletes' VO2max drops significantly. VO2max is the maximum amount of oxygen your body can use during exercise. It still stays above that of people who don't train.

The most important point for you: the VO2max gains you made recently are lost completely. If you got fitter this summer, or you started cycling a few months ago, stopping for the whole winter costs you more than it would a cyclist who has been riding for years.

The goal isn't a perfect winter. It's making sure you never go four weeks without enough training stimulus. A relaxed workout between two busy weeks is better than nothing.

A fan comes first

The indoor trainer has an obvious physical drawback: the air doesn't move the way it does outside. Heat builds up, you sweat more, and you tire faster.

A lab study (Fernandez et al., 2023) tested a fan with 16 active adults. Each person did two 40-minute sessions at 70% of heart rate reserve, one with a fan and one without. The results:

• lower feeling of heat with the fan (3.8 versus 5.5);
• less body mass loss (0.4 kg versus 0.6 kg);
• no significant difference in perceived effort;
• higher work capacity.

In other words, the fan lets you work harder without the effort feeling harder. The study was done on a cycle ergometer, with young participants (25 years old on average), at about 4 m/s of airflow. Treat this as a good reason to set one up, not as an exact setting to copy.

Keep a water bottle within reach. The body mass loss measured in the study came mostly from sweat.

Intensity distribution: an open debate

Many winter plans are built around polarized training.

Is it the best way to train? The research doesn't agree. Stöggl and Sperlich (2014) conclude that polarized training has a greater effect on key endurance variables than threshold work, high intensity, or high volume, in well-trained athletes. On the other side, a 2024 meta-analysis (Oliveira et al.) finds that polarized training improves aerobic power (VO2peak) more, but does not improve aerobic capacity more than other intensity distributions. Its advantage shows up mainly in interventions under 12 weeks, which is about the length of a winter block, and disappears in longer ones.

So the studies suggest polarized training may have a small edge over a short block. Coaching practice adds that you progress mostly with the plan you actually stick to.

For your winter, this means: easy workouts that really are easy, one or two hard sessions per week, and the rest free. If you don't know your heart rate zones yet, the heart rate zones tool gives you a starting point.

Strength training, the forgotten add-on

Outside, hills do the strength work without you thinking about it. On the indoor trainer, you pedal on a flat surface. This is a good time to add strength training.

In elite cyclists, Rønnestad and colleagues (2015) showed that adding heavy strength work to endurance training improved performance: power at 4 mmol/L of lactate, peak 30-second power, Wmax, and average power over 40 minutes, compared with endurance training alone. The study involved elite cyclists, so nothing proves the gain would be the same for a recreational rider. If you've never lifted weights, start light and build up gradually.

How reliable is the displayed power?

Your smart indoor trainer shows watts. Can you trust them?

For a precise model, yes, within a certain range. The Wahoo KICKR was compared with a dynamic calibration bench (Zadow et al., 2016). Between 250 and 700 W, at 80 to 120 rpm, its power was accurate, with an average bias of 1.1% on the low side.

Two takeaways. First, this result applies to that model, not to all indoor trainers. Another device may be better or worse. Second, easy endurance workouts often fall in the less accurate range. For those, your heart rate and how you feel are just as useful as the watts.

If you train by power, your threshold (FTP) is your baseline. The calculator below helps you find it.

What you can do before your next workout

• ✓Place a fan in front of you and a water bottle within reach before you get on the bike.
• ✓Plan your week: one truly easy workout, one structured workout with intervals, and one strength session.

In the easy workout, go by your heart rate as much as by the watts, especially if your device shows less than 200 W. In the structured workout, pick one intensity and stick to it instead of mixing everything together.

If you're coming back after a long break, or you have any doubt about your heart, talk to a doctor before adding intervals.

ELYO reads the workouts your watch records, whether they come from the indoor trainer or the road. It tracks your volume and consistency week after week, along with your heart rate at the same intensity, and then adjusts your plan. That's useful in winter, when a slightly short week can slip by unnoticed.

Written with the help of AI.