Group Ex Skills & Drills
Learn how to calculate beats per minute using the Tendy Formula.
When you teach group fitness classes, music is probably the most important “equipment” you work with. Appropriate music speed is a key ingredient in both motivation levels and exercise safety. Having an arsenal of premixed, measured and timed music is a convenient and popular way to prepare for class. Music technology has come a long way; fitness CDs, MP3s and music management software help us gather all the information we need. Song title, artist, time and beats per minute (bpm) are all included in the “liner notes.” However, every now and then you might want to incorporate a song from your personal collection (legally) that has a special theme or style. This article describes an accurate method of calculating the speed of that special song, enabling you to use it safely and effectively.
In my early years as a group fitness instructor, I worked with my brother John Tendy, a New York City–based musician, audio engineer and producer, to find the best music for my aerobics classes. Finding music at the proper speed for the various segments was a real challenge. John developed a formula in the early 1980s to calculate music speed, or beats per minute, while working as a club disc jockey. I named this technique after him, and I’ve used it since then. Once you learn to use a stopwatch properly, it’s spot-on accurate.
Equipment Needed: a stopwatch, or wristwatch with stopwatch capabilities, and a calculator.
Prerequisite Technical Skill: the ability to use a stopwatch. Most people have a digital wristwatch with a stopwatch mode, which will work fine. If using a wristwatch, brace it between your thumb and index finger, keeping the index finger on the start/stop button. Avoid using your thumb to push the button, as the fleshy part of the thumb will result in a start delay. The same theory applies for using a standard stopwatch: while holding the watch in your hand, place your index finger on the start/stop button.
For our purposes, we’ll define a beat as the rhythm that controls the movement or step for each count you hear or feel. Identify the most prominent downbeat at the beginning of a 4- or 8-count phrasing in your music selection. Most often it will be accented by a strong drum beat and a slight change in the music line. Now walk, march or jog to that rhythm. Each footfall is counted as 1 beat. For example, in music that uses 4/4 timing, when you walk—R, L, R, L—that grouping equals 4 beats. Practice listening for and indentifying the repetitive count of 8 beats as your music progresses (see the sidebar “Where’s the Beat?”).
COUNTING THE BEAT
- Select music that uses a 4/4 rhythm with typical 32-count, consistent phrasing.
- Once you’ve identified the beat, stay with the rhythm, listen to the beat and begin a silent self-count in time with the music.
- Lead in with a silent “5, 6, 7, 8” as a preparatory command for starting your 8-count set on the first main beat of the new measure. Practice identifying 2 sets of 8 counts, for a total of 16 beats.
TIMING THE BEAT
Calculate the time it takes for 2 sets of 8 counts (a total of 16 counts) to be completed.
Here is the critical “how to”:
- Start your stopwatch on beat #1. The first beat isn’t over until the next begins. By the same reasoning, the last beat isn’t over until the beat of the next measure begins; that is, the 16th beat isn’t over until beat #17 begins. Stop your watch on beat #17.
- A visual chart is helpful in understanding the start and stop points (see Figure 1).
- Record your time to the nearest hundredth of a second. Repeat again for accuracy.
- If the times are drastically different, repeat the process until you have two measurements that match or are very close. I usually take three measurements and record the middle measurement of the three to the hundredth of a second.
CALCULATING BEATS PER MINUTE
Here is an example of how you would calculate the speed of the music.
The time on your watch reads 7.03 seconds (maintain this number to the hundredth of a second; don’t round up or down at this point). Divide 960 by the time recorded on your watch. In our example, the result is 136.55, or 136 bpm. For those who are mathematically inclined and need to know how the formula was derived, here are the facts:
In our example, the time on your watch reads 7.03 seconds.
Solve for ∏:
At this point you can drop the decimal and use the number 136 bpm as your music speed.
Explanatory Notes: 16 x 60 = 960. Divide 960 by 7.03 = 136.55 bpm.
Keep It Simple. For those who failed high-school algebra, the magic number—the constant to remember—is 960. Just understand the very simple process without the mathematical derivations. Measure the time for 16 beats on your stopwatch, and remember the number 960 as a constant. Record the time it takes for 16 full beats. Divide 960 by the time you’ve recorded on your watch (our example shows 7.03 seconds). Voilà!
Accuracy. This method relies on the principle that you must start your watch at the same time as the beat begins and stop it at the conclusion of the beat that ends the phrase you are measuring; in our case, 2 sets of 8 counts. The method is focused on the beat as the controlling factor that determines measurement inception. It gives a more accurate measurement of music speed than a common method frequently used: starting one’s watch and then counting beats for 15 seconds and multiplying by 4, or counting for 30 seconds and multiplying by 2, etc.
Critical Information. For the instructor, instructor trainer and trainees, knowing the correct speed of the music is a critical component for proper class preparation. Experts have established recommended music speeds for conducting safe and effective workouts for specific activities (see the sidebar “Examples of Recommended Music Speed”). The Tendy Formula will help you stay within those guidelines.
Calibration. The formula enables you to verify music speeds listed on fitness CDs or calculate bpm for music company downloads when speeds are not listed.
Innovation. Sometimes, when you’re at an event, you hear a great new song that would work well in your class, and you want to check out the speed there and then. If you have a digital wristwatch, you’re now ready to gather the information you need.