Wives may be better at lugging heavy loads than husbands, according to new research.

Scientists studying the physics of backpacking found that smaller hikers can be better equipped to carry heavy loads than people with larger frames.

The reason may be linked to the fact that walkers carrying backpacks also have to haul their own body weight, scientists believe.

Hiking guidelines say that the weight of a pack should correspond to body size, with smaller individuals bearing lighter burdens.

Professor Michael O'Shea, from Kansas State University, US, who conducted the research using a computer model, said: "Online advice from several sources was somewhat misleading in suggesting that pack weight should be a certain per cent of a person's weight. However, as the size of any animal increases, strength increases more slowly than body weight - the reason why tiny ants can carry a disproportionately heavy load compared to their weight.

"Overall strength of an individual does not determine how heavy a backpack a person can comfortably carry."

Prof O'Shea noticed that some of the smaller hikers could carry greater back weights than larger students with similar fitness levels.

Incorporating pack weight and body proportion data, he came up with an equation to determine the maximum rucksack load suitable for a person of given size.