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SPRINTERS and jumpers should wrap themselves in an electric blanket instead of doing a physical warm-up before a race. Researchers in Manchester have discovered that an athlete鈥檚 performance improves if their muscles are artificially heated.

鈥淚t鈥檚 a really significant effect,鈥� says Anthony Sargeant at Manchester Metropolitan University. Muscle power goes up by 8 to 10 per cent for every 1 掳C rise in temperature, he says. And heating muscles artificially is better than a physical warm-up in some respects, because the muscles get hotter without becoming fatigued.

The finding could be particularly important for competitors in events such as the high jump, says Sargeant, where often athletes cannot predict when their next jump will be and have to do repeated warm-ups, tiring out their muscles.

Sargeant and his team carried out the study using an exercise bike. They asked six volunteers to pedal at two different speeds without any special preparation. They also got the volunteers to do the same exercises after a 30-minute leg bath in water heated to 42 掳C. The researchers worked out how efficiently the cyclists鈥� muscles were working by monitoring their breathing.

For those pedalling at a leisurely 60 revolutions per minute, the artificial warm-up actually reduced efficiency. Sargeant thinks that at lower speeds the temporary molecular cross-bridges that pull muscle filaments past each other during a contraction break off too quickly. It鈥檚 as if they are tripping over themselves, he says.

But when pedalling at full tilt鈥�120 revolutions per minute鈥攖he artificial warm-up reduced energy turnover by about 6 per cent, showing that the muscles were working more efficiently.

But the idea of donning heated long johns before a race hasn鈥檛 received a warm welcome from athletes. 鈥淚 wouldn鈥檛 recommend it,鈥� says British sprinter Linford Christie, who won an Olympic gold in 1992. Preparing for an event is very important psychologically as well as physically, he says. 鈥淏efore a race, you don鈥檛 want to be sitting down, you need to be on the move. But I鈥檓 from the old school,鈥� he admits.

Roger Woledge, a sports scientist at University College London, agrees. 鈥淚 suspect it feels horrid. You probably wouldn鈥檛 feel ready to go at all,鈥� he says. But Woledge thinks the technique might be a useful way to keep warm after a normal warm-up.

It鈥檚 not yet clear if the technique would help people taking part in endurance events such as marathons, Sargeant says. Artificial heating before a race might increase the risk of athletes overheating.