Effects of cycling exercise on self-reported anxiety and the hoffmann reflex
Motl, Robert Wayne
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Acute exercise consistently has reduced symptoms of anxiety. Yet, there are several limitations of previous research into effects of acute exercise on anxiety. One limitation has been that study participants were characterized by low pre-exercise state anxiety scores. Another limitation has been that researchers have ignored the concurrent effects of acute exercise on symptoms of anxiety and neuromuscular variables that might be correlates of anxiety. Two studies were conducted to examine the H-reflex as a neuromuscular substrate of anxiety that is altered by acute exercise using individuals with high trait anxiety or caffeine ingestion to increase pre-exercise anxiety scores. In the first study, the effects of low and high intensity cycling exercise on state anxiety and the H-reflex were examined among males having low or high trait anxiety. The results indicated that (1) exercise and quiet rest resulted in similar reductions of state anxiety, and the magnitude of the reductions was larger for males having high trait anxiety than low trait anxiety; (2) exercise, but not quiet rest, resulted in a reduction of the H-reflex; the magnitude of the reduction did not differ between males having low or high trait anxiety; and (3) reductions of self-reported state anxiety were unrelated to reductions of the H-reflex. Next, the effects of moderate intensity cycling exercise on state anxiety and the H-reflex were examined in individuals whose anxiety was experimentally manipulated by a large dose of caffeine. The results indicated that (1) caffeine consumption increased state anxiety, but it did not influence the amplitude of the soleus H-reflex; (2) acute exercise reduced state anxiety only after consumption of caffeine, but it reduced the soleus H-reflex after consumption of either caffeine or placebo; (3) there was no evidence of a relationship between changes in state anxiety and soleus H-reflex; and (4) neither caffeine nor acute exercise influenced the flexor carpi radialis H-reflex. Contrary to prevailing opinion, the post-exercise reduction in the H-reflex appears to be unrelated to self-reported anxiety after exercise. Researchers should examine the influence of processes within the spinal cord (e.g., presynaptic inhibition of Ia afferent fibers) and brain (e.g., inhibition of interneurons and neurons within the motor cortex) on the post-exercise reduction of the soleus H-reflex.