David Parkinson: I have recently taken delivery of a Concept 2 Indoor Rower which has sadly been banished to the loft by my wife. Due to a freak spell of hot weather in Yorkshire over the last few days, the loft has been very warm on each occasion I have used my new toy. My performance over 30 minutes is significantly worse now than it was in the gym (which is air-conditioned) about two weeks ago. Is this decline in performance due to it being hotter in my loft than the gym or could it be due to some other factors?Terry O'Neill: The temperature and humidity will definitely affect your performance. When we tested the athletes for the Olympics we had to make sure that both the temperature and humidity were the same and so testing is done in special labs. The body does not like to operate outside of its normal temperature, which is 35 degrees celsius or 98.4 in old money. A couple of degrees either side of this can cause problems. Working in your loft on a hot day means that your blood is diverted to the surface to try to control overheating. Sweat appears on the skin and evaporates, and it's this evaporation of sweat that reduces body temperature. If you get large wet patches appearing on your body then this means sweat is accumulating and not evaporating fast enough. This could be because of high humidity which means that the air is already saturated with water and cannot absorb any more, so more sweat is produced and this leads to dehydration. A 2% drop in hydration levels will cause a 10% drop in performance.So what to do? Plan A. Wait till the trouble and strife goes to bingo and sneak the machine down into the front room and train watching the telly.Plan B. Get a portable electric fan and possibly one of these water bottles that triathletes use which you put on your back with a feeder tube so you can take on water continuously. Word of warning: if you think it's uncomfortable now, wait until mid-winter. If you've got any brass monkeys I would keep the number of the local welder handy.