Math Skills for Fitness Professionals
I decided to write this article after my kids pointed out that they don’t need to learn math because they’d never use it as grown-ups. How many times have you heard kids talking about algebra that way. Personal trainers and other fitness professionals would probably be one of the last professions most people would think would need algebra. Several people think of personal trainers as just some muscle-head. The fact is that the most effective fitness professional would use math every day. As an Exercise Physiologist, I used algebra all the time. Here are some examples.
Body Mass Index (BMI) is calculated by Weight (kg) ÷Height (m)2. BMI is just height and weight and does not take into account body fat or lean muscle composition BMI is very inaccurate when measuring those with hypertrophic (big) muscles. It pretty much considers bodybuilders as “obese”
Body fat percentage is used to calculate how much adipose tissue vs lean muscle one has in composition.
Fat Mass = % Body Fat’ × Body Weight & Lean Body’Mass = Body Weight – Fat’Mass’
Target Heart Rate (THR) is the desired heart rate during cardio exercise and is calculated different ways. The simple formula is THR(bpm)=MHR x o.6 to 0.8 depending on goals. MHR is Max Heart Rate which is calculated by MRH=220-(age). The second formula (Karvonen) uses the HRR (heart rate reserve) which is the difference between resting HR and Maximum HR (HRR ÷ % Intensity) + RHR = Target Heart Rate (THR) Then multiply the desired intensity (%) by the HRR.
Cardiac Output (Q) is Q=SV*HR Stroke Volume times Heart Rate. This formula is not used by personal trainers much but exercise physiologists and cardiologists use it daily.
Basal Metabolic Rate is the daily caloric need at rest. The most popular formula for this calculation is the Harris-Benedict equation. BMR (men) = 66.5 + ( 13.75 × weight in kg ) + ( 5.003 × height in cm ) – ( 6.755 × age in years) BMR(women) = 66 + ( 6.2 × weight in pounds ) + ( 12.7 × height in inches ) – ( 6.76 × age in years).
One Rep Max is used to calculate intensity for weightlifting. 1RM (lbs) is the maximum weight one could lift with only 1 repetition. The percentage of that 1RM would be the intensity. example 85% of 1RM would equate to 6 reps. The intensity of the weightlifting would determine if you’re working for endurance, strength or hypertrophy.
Calories burned .0175 x MET x weight (in kilograms). METS are determined by intensity of the exercise (see chart). METS (Metabolic Equivalents) are somewhat relative to the exertion. 1 MET is equal to 1 kcal / kg / hour. Notice body weight is in the equation. This is why some cardio machines ask for your weight so it can display approximate calories burned.
Total Weight Volume is the working weight being lifted times reps times sets. TWV=W*R*S. This is used during weightlifting and is great tool for the strength training principle of progressive overload. A lot of gym rats like to go up in weight as your training progresses when you only have to progress in TWV as you go. You can keep the same weight but increase the sets and/or reps.
I’m not going into math for nutrition because there are so many equations for nutrition including calories and micronutrients. This could be a future article. Just know that protein is 3.8 kCals (calories), fat is 9.44 kCals, and Carbohydrates are 4.1 kCals.
There are several more equations before even getting into biomechanics (physics of body movement). This article only skims the surface of some math for fitness professional. There are entire textbooks devoted to mathematics for exercise. So think about this before assuming your certified personal trainer is just another muscle-head. Of course most states do not require certification for personal trainers so s/he may be one. Always ask for certifications.