Bilateral and unilateral contractions: Possible differences in maximal voluntary farce

The issue of whether there is a difference in the amount of force produced from a simultaneous two-limb maximal contraction compared to the sum of individual one-limb contractions has received considerable debate in the literature. A bilateral deficit (BLD) is when the resultant force from bilateral homonymous limb contractions is less than the summed force of individual limb contractions. Determining whether differences exist between one-and two-limb movements may provide insight into complex neuromuscular control patterns. Many dynamic two-limb studies report a BLD, whereas isometric studies are more numerous and controversial. It is important to categorize the movements studied in order to establish consistency. This paper purports that the BLD is an unstable phenomenon, and its presence should be considered in the context of the movement studied. Most likely, this phenomenon is dependent upon some minor deviation in descending drive between the cortical level and peripheral motor neuron.