AIM-listed sports and leisure equipment firm Tandem has warned that profits are to fall in the first half, compared with the same period last year, due to broader challengers for retailers.Pre-tax profit in the six months to 31 July is expected to be lower than the £648,000 reported the year before, but should not be under the £547,000 seen in the first half of 2009. Nevertheless, the firm assured that this is a solid result in spite of a tough economic climate.Meanwhile, sales have fallen to around £16.7m, from £19.1m the year before."Trading has been particularly challenging during the period with a number of retailers reporting poor results and difficult trading conditions," the statement said.Due to the first half decline in profits, the company warned that pre-tax profit for the year ending 31 January is expected to be behind the prior year."National retailer buying plans continue to be a concern as we enter the second half of the year. There are currently no indicators that this position will improve, although listings for Spring/Summer 2012 have been maintained and are broadly similar to 2011."BC