Spinal reflex plasticity in response to alpine skiing in the elderly.

The present study was designed to assess the influence of 12 weeks (28.5 ± 2.6 skiing days) of alpine skiing on spinal reflex plasticity, strength and postural control in senior citizens. Therefore, soleus H-reflexes and postural stability were measured during bipedal quiet and unstable stance in 22 (12 male and 10 female) elderly subjects aged 66.6 ± 1 years. Furthermore, the maximal isometric force was determined in a leg press. The results showed an increased H-reflex excitability after the training (+39%; P<0.05) while no changes occurred in the background EMG. The postural sway decreased after training (-6.6 cm; P ≤ 0.05) and the maximal force increased (+16.1%; P<0.05). No adaptations in any parameter could be observed in the control group. The present study demonstrated that skiing training was effective to alter the spinal reflex activity in elderly individuals. The increased H-reflexes correspond to adaptations known from strength training in young subjects. It may be assumed that alpine skiing induced a functional adaptation in that subjects have learned to integrate Ia afferent feedback more efficiently to ensure adequate motoneuron output.