A decision to change the date of one of the season's premier events to avoid hot-weather fallout has left organisers with fresh safety concerns - particularly for runners taking part in next week's Hong Kong Marathon. About 250 athletes will contest the first race of five in the PowerBar Bonaqua Action Sprint series at Repulse Bay tomorrow. Last year, the race was held in April and two athletes collapsed from dehydration in a stiflingly hot gully, prompting a helicopter rescue. Both recovered after treatment. The 11km 'swim, run, climb' event was brought forward to tomorrow. While the date change has ensured cooler conditions, recent rain and humidity have left many parts of the route wet and slippery. 'Athletes should take particular care in these sections to avoid injury,' said race organiser Michael Maddess. 'This is of particular relevance to many runners who are using this event as preparation for next weekend's [Standard Chartered] Hong Kong Marathon.'