Find Your Target Heart Rates and Optimize Your Workouts

Calibrate exercise intensity to maximize gains

HEART RATE AND EXERCISE INTENSITY

The effectiveness of any training program is influenced by several factors, including frequency, intensity, time (duration), type (modality), volume, pattern, and progression. This is referred to as the FITT-VP principle.

Intensity is arguably the most important factor that determines the effectiveness of a workout. It is also the more difficult one to track.

For resistance training, there is a common albeit flawed method of estimating intensity as a percentage of our one-repetition maximum.

For cardiorespiratory training, the availability of different options (such as the Borg rating of perceived exertion (RPE) scale, ventilatory thresholds, percentage of maximal heart rate, or target heart rate) reflect the very difficulty of accurately and objectively representing intensity.

The growing sophistication of fitness trackers, especially those that can monitor heart rates, has nevertheless made it much easier to use target heart rate zones to design and execute our workouts. This can help ensure that our workouts achieve the intended objectives, whether they are to build cardiovascular endurance, burn fat, or improve general health.fat

FIRST, SOME MATH!

Resting Heart Rate

This refers to the number of heartbeats per minute when you are at rest. A normal resting heart rate is between 60 and 100 beats per minute (bpm). The most accurate method is to measure your heart rate the moment you wake up, while still in bed. You can measure it by checking your pulse either at the wrist or the neck. Many fitness trackers measure and monitor this particular metric for you. The example below is from Apple Health, based on readings from my Apple Watch.

Maximal Heart Rate

This is the highest heart rate you can attain. It decreases with age and does not improve with cardiorespiratory and other training. The scientific method is to perform a maximal effort exercise assessment. However, this is not appropriate or practical for most individuals. Instead, we tend to rely on mathematic estimates like the commonly-used “220 minus age” formula. Organizations such as the American College of Sports Medicine (ACSM) and the American Council on Exercise (ACE) recommend using the Gelish formula instead as it has a smaller standard deviation and is a little more accurate. Regardless of the formula used, the calculation remains an approximation and should be used only as an initial guide.

Heart Rate Reserve

This refers to the reserve capacity of the heart and reflects its ability to increase the rate of beating and cardiac output above resting level to maximal capacity. It is calculated by subtracting your resting heart rate from your maximal heart rate.

Target Heart Rate

The target heart rate is used to gauge exercise intensity. For example, it is recommended that individuals perform 150 minutes of moderate-intensity or 30 minutes of vigorous-intensity cardiorespiratory exercise each week. Translating this into heart rates, the American Heart Association recommends moderate-intensity and vigorous-intensity exercises be performed at target heart rates of 50-70% and 70–85% respectively.

The target heart rate can be calculated using the Karvonen formula, as illustrated below. Alternatively, there are online calculators as well.

TARGET HEART RATES IN PRACTICE

The target heart rate is a handy tool to have regardless of the type of workout you are doing.

STEADY-STATE CARDIORESPIRATORY EXERCISE

For steady-state cardiorespiratory exercise, like jogging or swimming, I try to stay within 50–69% of the Target Heart Rate for the bulk of the exercise. Exercising at light to moderate intensity is reportedly better for burning fat compared to exercising at vigorous or maximal intensity. Nevertheless, to keep things interesting, I will throw in the occasional sprint to kick the heart rate up to the vigorous range.

HIGH-INTENSITY INTERVAL TRAINING (HIIT)

I find the target heart rate most useful when doing a HIIT workout. The target heart rate is used in three ways:

1. Warm-up & Cool-down. A good warm-up is essential when doing HIIT to reduce the risk of injury. I try to get my heart rate to around the 50% intensity level.
2. Exercises. For cardiorespiratory-focused HIIT workouts, I prefer the treadmill and the rowing machine. I sprint for 30 to 45 seconds. This allows me to hit and sustain the target heart rate for at least 5 to 10 seconds. To hit higher target heart rates, I increase the speed and/or the gradient and resistance of the treadmill and rowing machine respectively. It is also possible to apply this strategy to circuit training. The key is to perform each exercise as close to the target heart rate and for as long as possible, before slowing down to recover.
3. Rest intervals. I slow down to a jog or walk to bring my heart rate back down to the 50–65% intensity level. This usually takes between 90 seconds to 2 minutes, sometimes longer.

RESISTANCE TRAINING

I like to monitor my heart rate during resistance training to get additional information on how hard I’m working. I expect my heart rate to go up to around 50–60% intensity level, or I would not be working hard enough.

TAKEAWAYS

1. Make it a habit to track your heart rate. It is a good indicator of the state and trajectory of your health.
2. The heart rate can be a useful tool to program your workouts. It can help to ensure that you are exercising at the optimal intensity.
3. Improvements in fitness can lower your resting heart rate over time. This will increase your heart rate reserve but lower target heart rates accordingly. Be sure to review your metrics and calibrate your exercise intensities accordingly.

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