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By BARBARA BUSHMAN, AUTHOR OF FITNESS PROFESSIONAL'S HANDBOOK
In a world where information is a click away, food can be delivered before hunger even sets in, and a “time is of the essence” mindset is prevalent, can a commitment to a long-term exercise program retain any appeal? To convey the value of a lifelong commitment to exercise, fitness professionals will benefit from understanding the cause-and-effect connection between physical activity and specific outcomes as well as distinguishing between short-term (acute) and long-term (training) responses.
The responses in the days and weeks following the initiation of a dose of exercise can vary substantially, depending on the variable being measured (1,2):
· Rapid responses: Benefits occur early and plateau.
· Linear responses: Gains are made continuously over time.
· Delayed responses: Responses occur only after weeks of training.
The following figure helps to visualize the proposed dose–response relationships between amount of exercise performed per week at 60% to 70% maximum work capacity and changes in BP and insulin sensitivity (curve on left), which appear most sensitive to exercise; VO2max and resting HR, which are parameters of physical fitness (middle curve); and lipid changes, such as increases in HDL which are delayed (curve on right) (data from reference 3).
The dose–response relationship of exercise has important implications when exercise is used alone or in concert with medication to control disease. Understanding that some benefits occur immediately (e.g., reduced feelings of anxiety, improved sleep, greater insulin sensitivity, reduced BP) while others take consistent engagement for weeks or months (e.g., increased cardiorespiratory fitness, sustained reduction in BP) helps give a realistic framework for an exercise program (4). Some improvements require ongoing and consistent engagement in physical activity. To retain benefits, this must be a lifelong commitment. Fitness professionals can encourage clients by highlighting rapid changes, while also tracking improvements in other aspects of health and fitness that may come about more slowly.
Material adapted from “Short- and Long-Term Responses to Exercise” in Chapter 13 Exercise Prescription for Aerobic Fitness of the 8th edition of the Fitness Professional’s Handbook.
REFERENCES
1. Haskell, W.L. 2001. What to look for in assessing responsiveness to exercise in a health context. Medicine & Science in Sports & Exercise 33:S454-S458.
2. Haskell, W.L., I.-M. Lee, R.R. Pate, K.E. Powell, S.N. Blair, B.A. Franklin, C.A. Macera, G.W. Heath, P.D. Thompson, and A. Bauman. 2007. Physical activity and public health: Updated recommendations for adults from the American College of Sports Medicine and the American Heart Association. Medicine & Science in Sports & Exercise 39:1423-1434.
3. Jennings, G.L., G. Deakin, P. Korner, I. Meredith, B. Kingwell, and L. Nelson. 1991. What is the dose–response relationship between exercise training and blood pressure? Annals of Medicine 23:313-318.
4. U.S. Department of Health and Human Services (HHS). 2018. Physical Activity Guidelines for Americans. 2nd ed. https://health.gov/our-work/nutrition-physical-activity/ physical-activity-guidelines/current-guidelines.