Are you part of the reported 55% of individuals who have proven to be continuously committed to their New Year’s resolutions a month after the turn of the year?4 Research has shown that 46% of individuals who partake in New Year’s Resolutions are successful at accomplishing and maintaining goals such as, smoking cessation, exercise initiation, and weight loss goals at 6 months (4). Adherence is critical in meeting physical activity goals of accumulating the “minimum of 150 minutes (2 hours and 30 minutes) a week of moderate-intensity, or 75 minutes (1 hour and 15 minutes) a week of vigorous-intensity aerobic physical activity, or an equivalent combination of moderate and vigorous intensity aerobic activity (10).” Although the action and maintenance phase of changing health behaviors are key, commitment to a goal does not necessarily mean individuals are always aware of how to properly execute their change. Individuals can be inefficient in the manner in which they perform, therefore accomplishing only part of their intended goal. For example, restricting one’s calories can be achieved by only eating candy, but knowledge of “Choose My Plate” informs us of the nutritional deficiency that would accompany that low-nutrient, high-sugar diet. So for those who have vowed to be more active, here are a few ways to calculate your intensity to ensure that you are exercising at an intensity which will reap you the most benefits for improved health (9).
Target Heart Rate
Exercise intensity refers to how hard you are working, specifically your heart, during exercise. When there is not access to a graded exercise test to assess maximal capacity, you can calculate the heart rate you need to attain to get moderate-intensity exercise. Moderate-intensity exercise can be quantified by calculating 55-65% of one’s predicted maximum heart rate (7). Gellish et al. created a formula (HR max = 206.9 – (0.67 × age)) which allows an estimated calculation of age-predicted maximum heart rate in both men and women. Currently, it is considered the most accurate and consistent when compared to the historical formula “220-age”. Target heart rate (HR) can be calculated using either equation below, but including resting HR increases accuracy. The formulas for calculating an exercise prescription using HR are (9):
Target Heart Rate (THR) = [(HR max – HR rest) × % intensity] + HR rest
THR = HR max × desired %
As one’s fitness increases, their resting HR drops, which increases their heart rate reserve (HRR). Heart rate reserve is the difference between a person’s measured or predicted maximum heart and their resting heart rate (HR rest) (9). Cheng et al. used the Cooper Center Longitudinal Study and found that HRR is inversely related to cardiovascular mortality, after adjusting for age, resting HR, cardiovascular fitness, resting systolic BP, systolic BP difference, total cholesterol level, triglyceride level, body mass index (BMI), smoking, and alcohol consumption (1).
VO₂Max or Maximum Oxygen Utilization
VO₂Max, is the maximum amount of oxygen in liters that the body can transport and utilize. It is also a direct reflection of cardiorespiratory fitness. Moderate intensity exercise is defined as 40% to 50% of VO₂Max7 at which you would experience slightly increased breathing and heart rate (HR) (7). VO₂ can only be obtained through graded exercise testing (GXT) which is expensive and not widely available. However, it is recognized as the gold standard for cardiovascular fitness and maximal aerobic power evaluation (9,6). If you have the ability to undergo VO₂Max testing, you can learn your own VO₂Max. Then, you can utilize the measured maximum heart rate to calculate your optimal heart rate. Johnson et al. reported that moderate- intensity exercise, defined as 40-55% of VO₂ is adequate for improving waist circumference, insulin sensitivity and triglycerides in a group of individuals with risk factors for metabolic syndrome (2).
Objective measures of exercise intensity, such as heart rate, will help to gauge your exercise more effectively than subjective measures of “how you feel”. Heart rate monitoring, whether manual or with devices, makes targeting appropriate work-out intensity easy to achieve. Specifically, heart rate monitors provide immediate information about heart rate response, helping weekend warriors or personal trainers gauge whether the work being put forth should be increased or decreased in order to reduce injury and improve fitness. So before you go on that next run, estimate your maximum heart rate using one of the above methods, and calculate your target heart rate zone, in order to ensure you are working at an accurate intensity. Being committed to physical activity is an action worthy of praise. However, in order to ensure you are getting the maximum benefits of an active lifestyle, you must keep in mind that your aerobic fitness is a direct product of the intensity of your workouts. There are several objective ways to gauge your workouts to ensure you are getting the maximum benefits of an active lifestyle. Physical activity is categorized into three categories: light, moderate, and vigorous. The US Surgeon General clearly states that most adults will achieve the most benefits from moderate and/or vigorous exercise (9).
1. Cheng, Y. J., Macera, C. A., Church, T. S., and Blair, S. N. Heart rate reserve as a predictor of cardiovascular and all-cause mortality in men. Med Sci Sports Exerc. 1873-1878, 2002.
2. Johnson, J. L., Slentz, C. A., Houmard, J. A., Samsa, G. P., Duscha, B. D., Aiken, L. B., McCartney, J. S., Tanner, C. J., Kraus, W. E., Exercise Training Amount and Intensity Effects on Metabolic Syndrome (from Studies of a Targeted Risk Reduction Intervention through Defined Exercise). American J of Cardiology.100.1759-1766, 2007.
4. Norcross, J. C., Myrkalo, M. S., Blagys, M. D., Auld Lang Syne: Success Predictors, Change Processes, and Self-Reported Oucomes of New Years’s Resolvers and Nonresolvers. Journal of Clinical Psycholog. 58 :397-405,2002.
5. Myers, J., Prakask, M., Froelicher, V., Do, V., Partington, S., Atwood, J.E., Exercise capacity and mortality among men referred for exercise testing. New England Journal of Med.346:793-801.
6. Pollock, M. L., Ph.D., Gaesser, G. A., Ph.D., Butcher, J. D., Després, J., Dishman, R. K., Franklin, B. A., Garber, C. E. American College of Sports Medicine. ACSM Position Stand: The Recommended Quanity and Quality of Exercise: Rationale and Research Background. Medscape Today News. http://www.medscape.com/viewarticle/716399_2.
7. Thompson, W.R, Gordon, N. F., Pescatello, L. S.,(2010) ACSM’s Guidelines for Exercise Testing and Prescription. Philadelphia: Lippincott Williams &Wilkins.
8. 2008 Physical Activity Guidelines for Americans http://www.health.gov/paguidelines/guidelines/summary.aspx.