The differential cardiovascular responses to voluntary and electrically-evoked involuntary static contraction between ankle extensor and flexor muscles in humans

 

Nan Liang, Kanji Matsukawa, Tomoko Nakamoto, Seina Mochizuki, and Kyoko Oda

Department of Physiology, Graduate School of Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8551, Japan

 

To examine whether there is a difference in the central modulation of the cardiovascular responses to static contraction between ankle extensor and flexor muscles, we encouraged seven healthy subjects (three males and four females, age range 21-28 yrs) to maintain voluntary (VOL) and electrically-evoked involuntary (INVOL) static contractions of the right triceps surae (TS) and tibialis anterior (TA) muscles.  Each exercise was conducted with 30% of the maximum force of right ankle plantar and dorsal flexion, respectively, for 2 minutes.  Arterial pressure (AP) and heart rate (HR) were increased in all interventions.  The increases in AP and HR were greater in the VOL condition than those in the INVOL condition irrespective of the contracting muscle, suggesting a role of central command in the cardiovascular adaptation.  More importantly, the increments of AP and HR were larger when contracting TA, as compared with TS, especially in the VOL condition.  The present findings indicate that the cardiovascular response to voluntary static contraction is mainly produced by the central control with different strength depending on extensor and flexor muscles.

 

Key words: central command, exercise pressor reflex, voluntary exercise