Regulation of glucose turnover and hormonal responses during electrical cycling in tetraplegic humans

M. Kjær, S. F. Pollack, T. Mohr, H. Weiss, G. W. Gleim, F. W. Bach, T. Nicolaisen, H. Galbo, K. T. Ragnarsson

Research output: Contribution to journalArticlepeer-review

58 Scopus citations

Abstract

To examine the importance of blood-borne vs. neural mechanisms for hormonal responses and substrate mobilization during exercise, six spinal cord-injured tetraplegic (C5-T1) males (mean age: 35 yr, range: 24-55 yr) were recruited to perform involuntary, electrically induced cycling [functional electrical stimulation (FES)] to fatigue for 24.6 ± 2.3 min (mean and SE), and heart rate rose from 67 ± 7 (rest) to 107 ± 5 (exercise) beats/min. Voluntary arm cranking in tetraplegics (ARM) and voluntary leg cycling in six matched, long-term immobilized (2-12 mo) males (Vol) served as control experiments. In FES, peripheral glucose uptake increased [12.4 ± 1.1 (rest) to 19.5 ± 4.3 (exercise) μmol · min-1 · kg-1; P < 0.05], whereas hepatic glucose production did not change from basal values [12.4 ± 1.4 (rest) vs. 13.0 ± 3.4 (exercise) μmol · min-1 · kg-1]. Accordingly, plasma glucose decreased [from 5.4 ± 0.3 (rest) to 4.7 ± 0.3 (exercise) mmol/l; P < 0.05]. Plasma glucose did not change in response to ARM or Vol. Plasma free fatty acids and β-hydroxybutyrate decreased only in FES experiments (P < 0.05). During FES, increases in growth hormone (GH) and epinephrine and decreases in insulin concentrations were abolished. Although subnormal throughout the exercise period, norepinephrine concentrations increased during FES, and responses of heart rate, adrenocorticotropic hormone, β-endorphin, renin, lactate, and potassium were marked. In conclusion, during exercise, activity in motor centers and afferent muscle nerves is important for normal responses of GH, catecholamines, insulin, glucose production, and lipolysis. Humoral feedback and spinal or simple autonomic nervous reflex mechanisms are not sufficient. However, such mechanisms are involved in redundant control of heart rate and neuroendocrine activity in exercise.

Original languageEnglish
Pages (from-to)R191-R199
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume271
Issue number1 40-1
DOIs
StatePublished - Jul 1996

Keywords

  • adrenocorticotropin
  • catecholamines
  • cortisol
  • epinephrine
  • functional electrical stimulation
  • glucagon
  • growth hormone
  • hepatic glucose production
  • insulin
  • metabolic regulation
  • norepinephrine
  • renin
  • spinal cord injury
  • β- endorphin

Fingerprint

Dive into the research topics of 'Regulation of glucose turnover and hormonal responses during electrical cycling in tetraplegic humans'. Together they form a unique fingerprint.

Cite this