Last week’s vocabulary primer on weight-training lingo set the stage for today’s lesson on terms you may see on the display in bright lights on cardiovascular equipment, or hear lean runners and sinewy cyclists discussing at the gym. Words like “fat-burning,” “aerobic,” “anaerobic,” and “cardio” often leave the average exerciser or the gym newcomer wondering just what to do on a piece of cardio equipment. A smiling, bubbly aerobics instructor stops halfway through class to take a “heart rate check,” but what does that really tell you? The ferocious Spinning instructor keeps referring to “Energy Zones,” but what is he talking about? Perhaps these definitions and explanations will help clear up your confusion.
Resting Heart Rate (RHR) – your heart rate at total rest. The best way to determine your RHR is to take your heart rate for one minute for three consecutive days, before rising from bed in the morning, and ideally upon waking naturally as opposed to being awakened by an alarm. Take the average of the three readings for your RHR.
Maximum Heart Rate (MHR) – the absolute highest number of times your heart is capable of beating in one minute. You do not want to exert yourself to this level in an exercise session. To determine your MHR, males – take the number 220 and subtract your age. Females, subtract your age from 226.
Target Heart Rate (THR) – your THR is a percentage of your MHR, and is determined by how hard you want to work and for how long. The type of workout, and therefore the THR, you choose is based on your fitness and/or performance goals.
Aerobic (may also be referred to as cardio, fat-burning, or endurance) – refers to activities that require oxygen and that increase your heart rate to within 65 and 80% of your MHR. It is important to work in this “zone” in order to improve your aerobic capacity and VO2 max – a measure of your ability to use oxygen to burn fat. Working in the aerobic zone increases the strength and size of your heart, meaning it doesn’t have to pump as many times to distribute blood through your body and therefore decreasing your RHR. The misleading blinking lights on the cardio equipment telling you that you are working in the “fat-burning zone” neglect to tell you that, in order to access your fat stores, you must work steadily in that zone for at least 60 minutes.
Anaerobic – 80 – 92% MHR. Usually one can remain in the anaerobic state for only short intervals. The length of the interval depends on the intensity – the harder you work, the less time you can stay there. Intervals may be performed in periods ranging from 30 seconds to 10 minutes, depending again on your fitness level and your goals.
Interval Training – periods of high intensity followed by periods of lower intensity. Working harder, at a higher intensity, or for a longer time, requires a longer recovery segment to allow the heart rate to fall. During interval training, the THR, or intensity of effort, is related to the length of the interval. The intervals can be long, with a recovery of equal time, and a lower THR (for example, 5 minutes working at a THR of 85%, with 5 minutes recovery), or short and at a higher intensity, with a longer recovery (30 seconds on at a THR of 95%, 60 seconds recovery).
Rate of Perceived Exertion (RPE) – how hard you feel like you are working. The standard RPE scale is on a measurement of 1 – 20, with 1 being very very light and 20 being very very hard. I prefer a 1 – 10 scale, with 1 being “I’m sitting on the sofa eating bon-bons and watching Seinfeld reruns,” and 10 being “someone please call 911!” My scale of 1 – 10 seems to correspond nicely with the THR percentages given. For example, when I ask people to describe their effort level on a scale of 1 – 10, someone who answers “7” is usually working near the 70% range of their MHR, and is capable of carrying on a conversation with some breathlessness.
Keep in mind that the percentages referred to above are based solely on your age. For a more accurate prediction of your THR for different types of workouts, you should also factor in your resting heart rate using what is known as the Karvonen formula. A 35-year-old male, with an RHR of 65, wanting to exercise at an intensity of 70%, would determine his THR as follows:
220 – 35 = 185 (MHR)
185 – 65 (RHR) = 120
120 x 70% = 84
84 + 65 (RHR) = 149
Therefore, this person would want to maintain a THR of approximately 149 bpm to work in the desired aerobic zone.
So, with these facts and figures in mind, you should have something to ponder when you begin your next cardio session!
Meredith Nelson, M.Ed, is the owner of PrimeTime Fitness, Inc, on Sullivan’s Island. Offering group fitness classes, PrimeTime Spin, private yoga, personal training, and monthly gym membership, Meredith divides her time between the gym on Sullivan’s Island and limited in-home training on Daniel Island, where she resides along with her husband, Mark. Meredith can be reached with your fitness questions at 843-883-0101, or Meredith@primetimefit.net.