Bikes, toys and sporting goods distributor Tandem said half year pre-tax profit jumped 21.3% while revenue rose 5.2%.Revenue for the six months ended 31 July 2009 rose to £18,949,000 from £18,020,000 in the same period last year. Profit before tax increased to £547,000 from £451,000. No dividend is proposed."Trading conditions continue to be demanding and every effort is being made to maintain a level of profitability," it said.Revenue in its bicycles and accessories businesses rose 27.3% to £12,912,000 while operating profit was £284,000 compared with £605,000 in 2008. The profit reduced as a result of charges to cost of sales for the revaluation of foreign exchange contacts referred to below, Tandem explained."Although our unit selling prices increased it was not possible to recover the full impact of rising costs in Asia and the volatile dollar and as a consequence margins in the bicycle businesses were lower," it added.Tandem added that poor weather suppressed demand in the second half of the year. "The situation has since improved and we therefore expect to achieve a satisfactory result for our bicycles and accessories businesses for the full year."