The purpose of this study was to test the effect of arm swing on modulation of soleus H-reflexes amplitudes during walking. Fifteen subjects walked (1.07 m/s) on a treadmill in 4 arm swing conditions: 1-natural arm swing (control), 2-active restraint, 3-passive restraint, and 4-passive-assisted. Tibial nerve was electrically stimulated and soleus EMG was recorded. H-reflex amplitude was significantly greater during active than during passive restraint (p = .013). Remaining arm swing conditions were not significantly different. We detected a subtle effect of arm swing on soleus H-reflex amplitude. Descending regulation may serve as a gating mechanism to control the effect of arm movements on reflex pathways for leg muscles. This gating mechanism may be impaired postneural injury, potentially enhancing the modulation of peripheral sensory inputs on reflexes in leg muscles during walking. Future experiments to test additional conditions and evoking reflexes in more phases of walking are recommended.
Chetan P. Phadke, Marc Klimstra, E Paul. Zehr, Floyd J. Thompson and Andrea L. Behrman
Kathye E. Light, Marie A. Reilly, Andrea L. Behrman and Waneen W. Spirduso
The purpose of this study was to examine the effect of practice on simple reaction time (RT), movement time (MT), and response consistency for two arm-reaching tasks of graded complexity in younger and older adults. Forty subjects, 20 younger adults (age range = 20–29 years) and 20 older adults (age range = 60–82 years), were randomly subdivided into practice and control groups. All subjects were pretested on each arm-reaching movement on Day 1. The practice groups practiced each task for 160 trials over 2 consecutive days while the control groups practiced a memory task and answered a health survey. All subjects were posttested on Day 3. The major finding was that practice reduced the simple RTs of older persons to the level of younger persons. MTs for both practice age groups were reduced, but the age differences in MT performance were maintained.