1. Aiken LS, West SG (1991) Multiple Regression: Testing and interpreting interactions. Sage, California.
2. Compendium of Physical Activities: classification of energy costs of human physical activities
3. American College of Sports Medicine (1993) Resource manual for guidelines for exercise testing and prescription, 2nd edn. Lea & Febiger, Philadelphia.
4. American College of Sports Medicine (1995) American College of Sports Medicine’s guidelines for exercise testing and prescription, 5th edn. Williams & Wilkins, Philadelphia.
5. Women, family demands and health: the importance of employment status and socio-economic position