Overload, Performance Incompetence, and Regeneration in Sport

Abstract

Knee trauma and operations have a high incidence and economic relevance. They are among the most frequent injuries especially in sports. In spite of advances in diagnostics, surgical procedures and physiotherapeutic rehabilitation, there are short and/or long-term changes in motoric function following trauma and surgery. Deficient activation of the musculature is seen, especially the knee extensors, consecutive atrophy - especially of the vastus medialis muscle - and coordinative changes may occur. For post-traumatic and postoperative changes - for both the deficits and the therapy- or training-related adaptations - the explanations are meager. The objective of our study was to evaluate if the central and peripheral nervous system plays a role in the development of quadriceps muscle atrophy. Methods: 18 male subjects (mean age 27.2 � 6.36) with chronic rupture of the anterior cruciate ligament (ACL) took part in the study. Motor and sensory nerve conduction studies including F-wave and H-reflex measurement, an assessment of the central nervous system by magnetic evoked potentials (MEP) and isometric contraction of the quadriceps muscle without and with simultaneous femoral nerve stimulation were conducted. Results: Nerve conduction studies and magnetic evoked potentials were in normal range on both legs without any significant difference between injured and non-injured leg. Isometric contraction of the quadriceps muscle showed a significant reduction of the torque while torque increase during simultaneous stimulation of the femoral nerve revealed a significant larger increase of the torque in the injured leg. Conclusion: There is no evidence for a structural lesion of the central or peripheral nervous system causing quadriceps muscle atrophy. However, the significant greater increase of torque during isometric contraction of the quadriceps muscle with superimposed stimulation of the femoral nerve suggests a central activation failure that leads to an insufficient activation of motor units. This might cause the observed muscle atrophy. � 2001, Editrice Kurtis