Effect of resistance training on active and passive patellar stabilizers

Abstract

Patellofemoral pain syndrome (PFPS), which affects approximately 25% of the population at some stage in their lives, could be caused by an unstable patellofemoral joint leading to excessive lateral patellar tracking in postural and functional loadings, which eventually strains the retro-patellar subchondral bone and triggers the localized anterior knee pain. Although various medical and physical treatments have been prescribed for people with PFPS, literature on prevention of PFPS is lacking. Thus, the overall purpose of this thesis is to explore effects of physical conditioning on patellar stabilizers among previously untrained adults, in terms of biomechanical, morphological and functional changes of the passive and active patellar stabilizing structures. Five experiments were conducted to develop and validate the outcome measurements and the main study was a prospective investigation with 48 volunteers randomly allocated in three groups for 8 weeks, namely 1) weight training for muscular hypertrophy, 2) weight training for muscle strength, and 3) non-exercising control group. The subjects in the intervention groups were trained 3 times a week and all subjects were measured twice with 8 weeks apart for their cross-section of vastus medialis obliquus (VMO), patellar tilt angle and mobility, knee extension force, knee joint position sense and electromyographic (EMG) characteristics of the distal quadriceps. After the 8-week trainings, the subjects in both training groups had comparable and significant increases in the VMO size, passive patellar stability, knee extensor force, knee joint position sense and EMG onset and amplitude of vasti muscles, whilst the control group showed no significant change throughout the 8 weeks of study. The findings of this thesis form a basis for the establishment of a PFPS-prevention exercise program and enhance our understanding of the bio-kinesiology of the patellofemoral joint under the influence of systematic physical conditioning.