An examination of spastic and typically developing muscle fibre length responses to high velocity resistance training

Abstract

Muscle fascicle length (FL) is the most important architectural parameter affecting function; there have been inconsistencies in literature as to how to successfully increase FL. Using eccentric (ECC) training has reportedly increased FL, and 3 commonalities occur: muscle fibers undergo strain, are microscopically damaged, and a drop in joint moment during elongation occurs. We propose these three parameters need to be met to successfully increase FL. Individuals with Cerebral Palsy (CP) possess spastic muscles which are smaller than typically developing (TD) peers, which limits function; therefore, they would benefit from interventions which increase FL and improve functional abilities. Thus, an exploratory study was undertaken to establish if passive stretching of spastic muscles can mimic eccentric training due to the presence of a reflex contraction during stretching, and whether the criteria stated above can be induced in individuals with CP. The reliability of the measures used in the exploratory study were tested concurrently to this, to establish user reliability at measuring muscle FL using ultrasonography, and the minimal detectable change of muscle CK as an indicator of muscle microdamage in healthy adults, to inform whether microdamage occurred as a result of stretching in individuals with CP. A training program was then designed, informed by the exploratory study to induce possible increase in the length of fascicles in typically developing muscles over a period of 10 weeks. This was then undergone by an individual with CP as a case study using high velocity passive stretching (HVPS), to determine whether spastic muscles respond similarly to HVPS as do TD muscles to ECC training. Both TD and CP groups experienced an increase in isometric and ECC torque as a result of training, and CP participant improved balance and walking abilities. Future interventions could use HVPS to improve function in a larger sample size.