Sir David Jones is to step down as chairman of sportswear retailer JJB Sports for health reasons.Jones, who was diagnosed with Parkinson's in 1982, will step down from the role on January 31, but will remain a non-executive director.Senior independent director John Clare will be acting chairman until a permanent appointment is made.Jones joined the struggling retailer in 2007, becoming executive chairman in January 2009.His time at the company has been marred by controversy over a £1.5m loan he took from Mike Ashley, founder of rival sportswear retailer Sports Direct.JJB said today that Jones 'has been responsible for leading the rescue of JJB over the past year, steering it through the sale of its fitness clubs, an innovative CVA and a very successful capital raising in the autumn.'JJB Sports has also announced the appointment of rower Sir Matthew Pinsent and David Adams, who is the chairman of the suit retailer Moss Bros, as non-executive directors.Meanwhile, JJB posted a 28% fall in like-for-like sales in the year to January 24, but said that like-for-like sales continued to improve, from -37% in August to -21% in January.Sales have been hit by a lack of new stock, the company said.