title: Excitability of the soleus reflex arc during intensive stretch-shortening cycle exercise in two power-trained athlete groups.
abstract: In several explosive types of sport events the leg extensor muscles are subjected to very high impact loads. Thus, extreme requirements exist for the neuromuscular system to develop sufficient muscle stiffness in the lower extremities in order to tolerate these high impact loads. Therefore, it would be challenging to measure reflex modulation during high impact activities, and with different athlete populations. In the present experiment, H-reflex and short latency reflex (M1) sensitivity was measured during drop jump exercises among high jumpers and sprinters. The changes in both reflex peak-to-peak amplitudes showed a significant (P < 0.05) reduction towards the end of the exercise for the sprinters. In addition, the same subject group showed a remarkable increase in serum creatine kinase (CK) activity 2 h after the jumps. Similar changes could not be observed for the high jumpers. These results clearly indicate different neural adaptation strategies for the two athlete groups. Reduction in H-reflex sensitivity and an increase in CK-activity in sprinters were taken as evidence for presynaptic inhibition, probably induced by substances related to muscle damage. Since high jump training includes more high impact loading, it was assumed that it could lead to some structural adaptation and, thus, prevents exercise induced reflex modification to a certain extent.
authors.affiliation: Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, 40100 Jyvaskyla, Finland. janne.avela@sport.jyu.fi
authors.forename: Janne
authors.initials: J
authors.lastname: Avela
authors.forename: Jarkko
authors.initials: J
authors.lastname: Finni
authors.forename: Paavo V
authors.initials: PV
authors.lastname: Komi
mesh_terms: D000328:Adult; D052283:Creatine Kinase, MM Form / Q000097:blood; D004576:Electromyography; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D006801:Humans; D035002:Lower Extremity; D018482:Muscle, Skeletal / Q000294:innervation* / Q000502:physiology; D009473:Neuronal Plasticity; D010809:Physical Fitness / Q000502:physiology*; D012026:Reflex, Stretch / Q000502:physiology*; D014142:Track and Field
chemical_list: D052283:Creatine Kinase, MM Form