10 Popular Fitness Terms Defined

Common Fitness Terminology.

 A few years ago, complaining about the HIIT in your WOD at your local box would have only made sense to extreme fitness enthusiasts. Thanks to the explosive popularity of CrossFit and other high-intensity training programs, we now know that HIIT refers to high-intensity interval training and WOD is an acronym for the unique Workout of the Day offered at CrossFit training facilities (commonly called a ‘box’). Whether you’re new to the fitness scene or have been working out in health clubs for years, you’ve probably heard certain fitness terminology thrown around. Here are 10 commonly used fitness terms along with a brief explanation of the science behind each one.


Is often shortened to rep which is a single rendition of an exercise. The negative and positive parts of a movement make up a repetition. Using the push-up as an example. From the ground, you go all the way up till the arms are fully extended and get back down to the start to make one rep.


A group of consecutive repetitions that you perform without rest. After doing 12 repetitions of lets’ say the shoulder press, you have done a set. Advanced trainers can do as many as four sets while a beginner needs two sets.


It encompasses virtually every aspect of what you do in the gym.  The type of equipment in use, the number of exercises, sets, and repetitions. It also includes the order of the exercises and how much rest in between sets. By varying the elements of your routine-say, decreasing the number of reps, or by adding a new exercise, you can significantly get the results you get from your training.

Your routine encompasses virtually every aspect of what you do.


When it comes to exercise, burning is often used to refer to the feeling of when muscles experience an accumulation of metabolic waste (lactic acid), which creates fatigue. Acidosis is a change in blood acidity—specifically, elevated levels of lactic acid and hydrogen ions—that is often the result of moderate- to high-intensity exercise. A burning sensation in a muscle is an indication of acidosis. It’s also a sign that it is time for a recovery period to allow the body to remove metabolic waste from the working muscles and replenish the nutrients required to continue performing muscle contractions.


Jogging or running is great cardio.

Cardio is short for cardiorespiratory or cardiovascular exercise and refers to exercise that elevates the heart rate to pump oxygen and nutrient-carrying blood to the working muscles. Most often used for exercise performed on equipment like treadmills, elliptical runners, or stationary bikes, it is important to know that ANY exercise that elevates the heart rate can provide cardiorespiratory benefits. Circuit training with free weights or performing an AMRAP (as many rounds of a particular circuit as possible in a given amount of time) can be considered cardiorespiratory exercise.

Core Training

To tone -up and get muscle definition.

This has become one of the most popular and overused fitness terms of the past several years. It seems as if almost any fitness class, workout program, or equipment will provide “core training” benefits. The “core” most often refers to the muscles that make up the mid-section of the body, including the ever-elusive six-pack. However, it is much more effective to think of the body’s core as the center of gravity and not an actual group of muscles. When we look at how the body functions during upright movement patterns such as walking, lifting an object off of the ground, or moving an object from one place to another, we have to consider the fact that any muscle that attaches to the spine, rib cage or pelvis influences movement around the body’s center of gravity.

High-intensity Interval Training (HIIT)

Refers to exercise performed at maximal intensity. However, it’s important to remember that intensity can be subjective—what may be low intensity for some may be high intensity for others. Walking continuously for a few minutes at a time could be considered “high intensity” for sedentary individuals. It is the same for those who have been dealing with chronic medical conditions that limit their ability to exercise.


If you ask most people what their general fitness goals are, the answer often is to “tone up and get in shape.” We have come to accept the term “tone” to mean muscular definition or the appearance of a well-defined muscle. The term is actually short for tonus, which is the technical term used to describe a state of contraction in a normally functioning muscle. Using a muscle repeatedly during a strength training exercise will leave that muscle in a state of semi-contraction, creating the defined appearance we have come to expect as the result of exercise.

Muscle Confusion

A popular consumer-oriented fitness program claims to be based on the science of “muscle confusion.” This is simply a marketing term created to describe the physiological effect of periodization, which is a method of organizing exercise programs based on alternating periods of intensity. The concept of periodization was developed by Soviet Union sports scientists who recognized that periods of high-intensity exercise (high stress) should be followed by a period of low-intensity exercise (low stress) to let the body fully recover from the workouts and allow the time for the physiological adaptations to occur.


This term is commonly used to describe a general model of exercises such as yoga or Pilates because they are traditionally performed with bodyweight and require concentration to execute challenging movement sequences. However, any purposeful movement, whether it’s a biceps curl or downward-facing dog, requires conscious effort. Therefore, almost any physical activity that involves learning and executing movement patterns, no matter how basic, requires cognitive focus and should technically be classified as mind-body. If you exercise without fully engaging your mind, it is like you are doing half the workout.