(…Or simply Walk or Jog? )
You’ve decided you want to start a running routine, or even just a walking or jogging routine. The intensity of your run will be greatly dictated by your starting fitness level and your goal intensity is going to be dependent upon your end goals. For many, simply meeting the minimum recommended time and intensity for aerobic exercise is enough to see health-related benefits. The American College of Sports Medicine (ACSM) recommends at least 5 days of 30 minutes of moderate intensity aerobic exercise for a total of 150 minutes or 3 days or more per week of vigorous intensity exercise for a total of 75 minutes per week. Intensity can be measured different ways, but the easiest for most individuals is by monitoring heart rate. The ACSM suggests that moderate and vigorous intensity exercise be prescribed using a method called Heart Rate Reserve (HRR). The Heart rate reserve was originally proposed by Dr. David Swain out of Old Dominion University. It has been suggested that HRR can serve as a surrogate for measures of oxygen consumption (VO2) (Swain, 1997, 1998), but more recent research has demonstrated that the relationship between the two variables may be weak when used with healthy, college-aged athletes (Solheim 2014). Although caution may be necessary when applying this model to athletic populations, recreational individuals can use HRR with success to plan and track an aerobic workout program designed to match the ACSM fitness standards. Thus, using an HRR of 50 – 60% for moderate and 70-80% HRR for vigorous intensity is appropriate for prescribing exercise in novice or recreational populations.
In order to being using HRR, there are a few variables that must first be calculated. Don’t worry, these are fairly easy to obtain. First, a resting heart rate value is required. The best way to get this is to measure your heart rate upon first waking in the morning. It should be done prior to significant movement and only after a night of sufficient rest. Sufficient rest may differ across individual depending on sleep norms. To obtain a resting heart rate value, use the carotid pulse or the radial pulse (thumb side of your inner wrist). Be sure to only use two fingers when taking the pulse and only put enough pressure to feel the pulse of the artery. Too much pressure will result in an inaccurate reading. Once you find your pulse, count beats for 10 seconds and multiple by 6. It is not uncommon for trained aerobic athletes to have a resting heart rate in the 40s, but most recreationally trained individuals range in the low 60s. If your resting heart rate is higher than 75 you may need to consult a physician before starting a running program (or check your sleep / caffeine intake / stress levels). The next variable you need is maximum heart rate. There are two ways to get this value, via calculation or after a graded exercise test. The calculation is obviously easier, but there may be more error associated with your calculated value. Calculations will be explored below, but first, if you are healthy and have access to a treadmill and a heart rate monitor you may want to try the graded exercise test method. It is recommended that you have a partner with you for this.
Graded Exercise Test (GXT):
On a motorized treadmill, perform a self-selected warm up and check the readings on your heart rate monitor- keep in mind PPE monitors may not be as accurate as a chest strap monitor. Begin the test walking at 3mph for 2 min. Increase the speed by 1mph every 2 min until you reach 9mph. Begin to raise the treadmill incline by 1% every 2 min until exhaustion. Have your partner help you change the speed/include and monitor your heart rate. If you’ve completed the test with maximal effort your heart rate in the last stage should reflect your max.
There are different equations depending on your age and most are for individuals college-aged or older. Keep in mind, that even if you select a calculation validated from your age-group, there may still be some error in the prediction. Still, its better than not having a prediction!
If you’re in your 20s: 220 – age = predicted max
30 – 50 years old or teenage boy? Use: 207 – .70*age = predicted max
Woman over 35: 206 – .88*age = predicted max
Older adults (65+ years): 211 – 0.64*age
Now you have all the data. Once you have your resting heart rate and predicted max heart rate use the HRR equation: (HRmax – Hrrest) to determine your HRR. Then, determine what intensity you want to work at. For this example, let’s say 60% HRR to meet the basic ACSM recommendations and your resting HR was 60 beats per min, and your HRmax was 200. Plug your desired intensity (60%) and your HRR into the equation below to determine your goal exercise heart rate.
%HRR = (HRexercise – Hrrest) / (HRR)
0.60*140 = (HRexercise – 60)/(200-60) and solve for HRexercise.
note: 0.60*140 represented 60% of your HRR
Once you’ve determined your HR exercise, you can get your HR monitor of choice and begin your aerobic workout. The most popular fitness monitors use HR measured at the radial pulse. However, it has been documented that these measures may be most accurate in novice athletes at low intensities (below 65%VO2max). So, once again, the best heart rate monitor to use would be the old fashioned polar chest strap. The goal during your run should be to maintain HR as close to your desired %HRR as possible. Maintaining HR may mean that you will have to slow your pace at some point, especially when you are just starting a new program. That’s okay, as long as you maintain that goal HRR you will be set up to reap the benefits associated with that intensity of exercise and meet your ACSM goals. Another important thing to keep in mind is that warm ups should not count towards your goal intensity and it may take your body up to 5 minutes to adjust to your exercise pace. Give yourself 5 minutes before you start changing your pace in response to your heart rate.
Looking for more running and aerobic exercise tips? Stayed throughout the month of September for more!
Riebe, D., Ehrman, J. K., Liguori, G., & Magal, M. (2018) ACSM’s guidelines for exercise testing and prescription. 10th ed. Wolters Kluwer.
Solheim, T. J., Keller, B. G., Fountaine, C. J. (2014) VO2 reserve vs. heart rate reserve during moderate intensity treadmill exercise. International Journal of Exercise Science. 7(4) : 311-317.
Swain, D. P., Leutholtz, B. C., King, M. E., & Branch, J. D. (1998) Relationship between % heart rate reserve and % VO2 reserve in treadmill exercise. Medicine and Science in Sports and Exercise. 30(2) : 318 – 321.