Bermuda swimmers Roy-Allan Burch and Lisa Blackburn have been stepping up their London Games bids at a training base in Colorado Springs in the US.Both Burch and Blackburn received special invites to workout at the Olympic Training Centre, usually reserved for only the top US swimmers during an Olympic year.At 6,500 feet above sea level, the pool enables swimmers to train at high altitude, which boosts their capacity to exercise and improve strength and stamina.Blackburn, who broke the Bermuda 200 metre breaststroke record twice in the recent meet Austin Grand Prix in Austin, Texas, said she had seen significant improvements in her performance since training at altitude.“Training at altitude was challenging, yet very rewarding as my training improved significantly. My strength improved and my training times also improved,” she said.“It has been several years since I’ve been able to post such quick times in practice so I look forward to continuing to train at this level for the next several months as I prepare to reach my Olympic qualification time.”Allan-Burch, who is also hoping to qualify for the Olympics, echoed his team-mates sentiments regarding the merits of altitude training.“The training camp was a great experience. I had previously visited the Olympic Training Centre at the end of 2002 heading into 2003 when I was in high school.“It was great to go back with a better understanding of what I needed to do with my training to raise my level of performance.“I learned more about what was expected of me from my coaches and amongst my team-mates. It was a wonderful bonding experience and of course the training was very intense.“I completed some of the fiercest workouts that I have ever been faced with. Along with the altitude the workouts were extremely difficult and mentally challenging.“Going forth with less than 200 days to the games, this gives me ample confidence in my ability to make great improvements. “Both athletes joined their respective teams at the Austin Grand Prix in Austin Texas directly following the intensive training camp in Colorado.Blackburn believed her impressive times at the meet suggested her new training methods were already paying dividends.“It can often be difficult to compete at sea level immediately after training at altitude but my swims were very good,” said Blackburn, who won silver at the 2003 Pan Am Games in the Dominican Republic while representing Canada.“It has been several years since I have competed in a Grand Prix final so to compete with the fastest swimmers was very rewarding.“It also shows that my training program and my hard work is starting to pay off. I was also very pleased with swimming to two national records in the 200 breaststroke.Allan-Burch has returned to his training base in Charlotte, as he looks to progress from the Olympic selection standard to the qualifying standard in the 50m freestyle at the British national trials in March.Meanwhile, Blackburn has headed to Naples, Florida, where she will continue to rev up for her bid to make the Olympic selection times with upcoming meets in Columbus and Indianapolis.