Strength change of quadriceps femoris following a single manipulation of the L3/4 vertebral motion segment: A preliminary investigation

The Purpose of this Study was to investigate whether a manipulation to the L3/4 motion segment of healthy individuals would affect the strength of the quadriceps muscle tested postmanipulation. Fifteen (15) consenting experimental subjects received a lumbar roll manipulation and 15 nonexperimental subjects underwent a simulated manipulation in the lumbar roll position. After these procedures, all subjects were required to perform a unilateral isometric maximal contraction of the quadriceps femoris after 60 sec. This was achieved using a force transducer to provide a digital measurement of the force of contraction of the quadriceps femoris. The study found that in an asymptomatic student population receiving a manipulation to the L3/4 motion segment, an overall statistically significant short-term increase in quadriceps femoris muscle strength was observed. This establishes a relationship between the short-term effects of a manipulation and the modulation of muscle strength, and supports anecdotal claims. Discussion is undertaken to describe further studies that can be performed to provide information on the way in which this relationship could possibly benefit sporting populations and rehabilitation therapists.