No more shoving cleats into the sauna. Footballers will be warmed up by a unique bag right on the pitch.
There’s nothing like it on the market yet, which is why the idea from two footballers carries the mark of a world first. To keep athletes on the bench from getting cold, they invented a heated leg cover. Using a power bank and smart textiles, the bag can heat up to around thirty degrees Celsius.
The leg cover, named Hot Boots, was developed at the Department of Textile Evaluation at the Faculty of Textile Engineering of the Technical University of Liberec. However, its creators are Karel Kozma — founder and head of his own football academy in Mladá Boleslav, coach, and active footballer — and his friend and former university classmate Martin Klepáč.
The two tested the first prototypes of the bag together, even locking themselves in a large freezer for 45 minutes. “Even at minus eighteen degrees, our boot maintained a comfortable temperature of twenty-four degrees Celsius,” says Karel Kozma.
They worked on the idea — unique not only in the Czech Republic but globally — for about a year. “I've been playing football my whole life, and the feeling of frozen feet on the bench has always been unbearable. You can take care of the rest of your body — put on a jacket, gloves, a hat — but while football boots are great sports footwear, they’re terrible for cold weather,” describes Karel Kozma.
“The worst time is always winter training, when you only play the second half in January, and the cold from your feet becomes unbearable, and you have no way to warm up,” he adds.
One evening, after a similar match, while warming himself in a plug-in blanket, he thought — why don’t we have something like this on the bench? He carried the idea in his head for about two years while continuing his coaching and playing career.
“When I still didn’t see any solution on the market, Martin and I decided to contact the Technical University of Liberec, where we studied economics. That led us to the textile faculty, where our idea began to take real shape,” recalls the footballer.
During development, they discovered that while the concept seemed simple, many technical challenges needed solving to make it functional. Finding a combination that provided warmth while allowing players to dry their boots — without condensation forming inside — was far from easy.
“Footballers try to keep their boots warm in all sorts of ways — some put them in a sauna, others use a kind of metal box that holds three pairs of boots and heats them with steam. But that makes the boots warm and also damp. We, on the other hand, used top-quality materials,” explains Roman Knížek, head of the Department of Textile Evaluation.
The cover consists of a three-layer laminate, with a nanofiber membrane in the middle and smart textiles inside — three heating pads integrated into the lining. These are connected at the back to a power bank. A player can step into the sleeping-bag-like cover even in their boots and pull it up to their thighs. The design and stitching were handled by **Kwak**, a Liberec-based company specializing in down sleeping bags, while the laminate was produced by **Svitap**.
The initial investment amounts to just under three million CZK, with a retail price of 14,000 CZK. The bag can be purchased by individual players or by football clubs — both amateur and top-tier.
“We can provide a full solution worth 160,000 CZK for a professional team needing twelve boot covers for the bench. We’ve also designed a charging system that charges multiple power banks at once, not one by one. A full charge lasts at least two hours — enough for an entire match. A transport bag is also included,” explains Karel Kozma.