"You want to make sure that your joints are not being excessively compressed or muscles put in abnormally shortened or stretched positions, " said Mary Ann Wilmarth, chief of physical therapy at Harvard University Health Services.
The trucking industry is starting the switch, with compressed natural gas being used in local delivery trucks and liquefied natural gas in over-the-road trucks, trains and barges.
Chairman of the Commons public administration committee Bernard Jenkin, a former defence spokesman, claimed the review was being carried out under a "startlingly compressed" timetable.