HORMONAL AND METABOLIC RESPONSES TO ELECTRICALLY-INDUCED CYCLING DURING EPIDURAL-ANESTHESIA IN HUMANS

Hormonal and metabolic responses to electrically induced dynamic exerc ise were investigated in eight healthy young men with afferent neural influence from the legs blocked by epidural anesthesia (25 ml of 2% li docaine) at L(3)-L(4). This caused cutaneous sensory anesthesia below T-8-T-9 and complete paralysis of the legs. Cycling increased oxygen u ptake to 1.90 +/- 0.13 (SE) l/min, and fatigue developed after 22.7 +/ - 2.7 min. Compared with voluntary exercise at the same oxygen uptake and heart rate, concentrations of blood and muscle lactate (musculus v astus lateralis) as well as plasma potassium increased more while musc le glycogen decreased more during electrically induced exercise. Hepat ic glucose production always rose during exercise. However, during inv oluntary exercise with sensory blockade, it did not match the rise in peripheral glucose uptake and plasma glucose decreased (P < 0.05). Pla sma glycerol increased less in electrically induced vs. voluntary exer cise, and free fatty acids and beta-hydroxybutyrate decreased only dur ing electrically induced exercise. Epinephrine, growth hormone, adreno corticotropic hormone, and cortisol levels were higher during involunt ary vs. voluntary exercise (P < 0.05). In conclusion, neural and humor al mechanisms exert redundant control with regard to responses of cate cholamines and pituitary hormones (growth hormone and adrenocorticotro pic hormone). In contrast, neural input from motor centers and feedbac k. from working muscle are important for glucose production and lipoly sis during exercise in humans. Humoral feedback is apparently not suff icient to trigger normal mobilization of extramuscular fuel stores.