Proprioceptive neuromuscular facilitation training induced alterations in muscle fiber 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 university students, males, were divided into two groups: PNF training and isokinetic training(ISO). The training regimen for the PNF group consisted of 3 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° /s in an isokinetic dinamometer (Cybex). Both groups trained three times a week for a total time of 8 weeks. Muscle biopsy specimens were obtained from the right vastus lateralis muscle before and after training.

Results: The mean percentage area of the 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 in 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 type II fibre subgroup.   

Original research is available here.