Calculating relaxation allowances for construction operatives. Part 2, Local muscle fatigue PriceAndrew 2014 Local muscle fatigue usually occurs at low levels of energy output where loads are applied to a localised group of muscles. Local muscle fatigue can be either static or dynamic, depending upon the frequency of loading. Several ergonomics theories relating to local muscle fatigue are reviewed. An alternative method for determining relaxation allowances for construction work is presented.