Intended for healthcare professionals

Research Article

Release of beta endorphin and met-enkephalin during exercise in normal women: response to training.

Br Med J (Clin Res Ed) 1984; 288 doi: (Published 30 June 1984) Cite this as: Br Med J (Clin Res Ed) 1984;288:1950
  1. T A Howlett,
  2. S Tomlin,
  3. L Ngahfoong,
  4. L H Rees,
  5. B A Bullen,
  6. G S Skrinar,
  7. J W McArthur


    Plasma beta endorphin and met-enkephalin concentrations were measured in response to treadmill exercises in 15 normal women before, during, and after an intensive programme of exercise training. Significant release of beta endorphin occurred in all three test runs, and the pattern and amount of release were not altered by training. Before training dramatic release of met-enkephalin was observed in seven subjects and smaller rises observed in a further four, and this response was almost abolished by training. This represents the first observed "physiological" stimulus to met-enkephalin release. Endogenous opioid peptides play a part in adaptive changes to exercise training and probably contribute to the menstrual disturbances of women athletes.