Proprioceptive neuromuscular facilitation training induced alterations in muscle fibre type and cross sectional area

Objectives: To compare the effects of proprioceptive neuromuscular facilitation (PNF) and isokinetic training on fibre type distribution and cross sectional area of the vastus lateralis muscle. Methods: Twenty four male university students were divided into two equal groups: PNF training and isokinetic training (ISO). The training regimen for the PNF group consisted of three sets of 30 repetitions against maximal resistance, alternating two patterns of sequential movements of the right lower extremity: ( a) toe flexion and ankle plantar flexion and eversion; (b) knee extension and hip extension, abduction, and internal rotation. The ISO group performed three sets of 30 repetitions alternating knee extension and flexion of the right leg at angular velocities of 180 and 90 degrees/s in an isokinetic dynamometer (Cybex). Both groups trained three times a week for a total of eight weeks. Muscle biopsy specimens were obtained from the right vastus lateralis muscle before and after training. Results: The mean percentage area of type IIB fibre was significantly decreased ( p< 0.01) after eight weeks of PNF training, whereas that of type IIA fibre was significantly ( p< 0.05) increased. The mean percentage area of ISO trained type IIAB fibres exhibited an augmentative pattern ( p< 0.01) with a parallel reduction ( p< 0.05) in type IIA. Percentage fibre type distribution exhibited a similar pattern. Conclusions: Both PNF and ISO training alter fibre type distribution and mean cross sectional area. These changes occur in the type II fibre subgroup.