Pete McCall by Pete McCall

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Fitness Terminology: 10 Popular Fitness Terms Defined

Every subculture has its own terminology for describing its way of life. The health and fitness subculture is no different. 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.


When it comes to exercise, burning is often used to refer to the feeling of when muscles experience an accumulation of metabolic waste, 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. 


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  

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)

We have written previous blogs about the benefits of HIIT here and here. This term makes the list because it is often used to refer 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.

For individuals with a history of being sedentary or who have been dealing with chronic medical conditions that limit their ability to exercise, simply walking continuously for a few minutes at a time could be considered “high intensity.” 

Metabolic Conditioning 

Similar to HIIT, metabolic conditioning is often used to refer to high-intensity exercise performed to the point of being out of breath or experiencing muscle soreness. Here is why this overused term ought to be retired from the lexicon: Metabolism is the chemical process by which a biological organism produces energy for muscular contraction. That means that any exercise requiring a muscle contraction (which in itself requires energy) is a form of metabolic conditioning. Standing from your chair after reading this post requires your metabolism to fuel your muscles. Therefore, it is more appropriate to describe the level of effort required to perform the planned activity, such as low-intensity, moderate-intensity, high-intensity or maximal intensity. 


This term is commonly used to describe a general mode of exercise such as yoga or Pilates, because they are traditionally performed with bodyweight (with the exception of Pilates programs involving equipment such as a reformer or barrel) 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.   

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 sport 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 to fully recover from the workouts and allow the time for the physiological adaptations to occur. 


Many programs or fitness classes refer to using plyos, which is short for plyometrics. Looking at the etiology of the word, ‘plyo’ (from pleio) is a pre-fix for “more” and metric refers to length; therefore, plyometric means “more length.” This describes the physiological affect of the involved muscles during jump training (the most common application for the lower body) or explosive movements such as medicine ball throws (often used for upper-body plyometric training).  

Plyometric training was developed by Soviet sport scientists who originally referred to it as “shock training” because of the high forces experienced by the involved tissue. That’s why it’s important to perform only a few repetitions at a time to achieve the highest level of force output possible. Any program requiring participants to perform more than five or six rapid movements (i.e., jumps or explosive lifts) in a row can significantly increase the risk of injury by placing too much force on the involved tissue. 


A number of exercise programs and classes are called Tabata, which is an actual person. Twenty years ago, Dr. Izumi Tabata, an exercise scientist from Japan, and his colleagues conducted research on ways to improve aerobic capacity using short intervals of extremely high-intensity exercise. They found that exercising at 170% of aerobic capacity on cycle ergometers for a work interval of 20 seconds followed by a brief recovery interval of only 10 seconds, repeated to exhaustion, was extremely effective at boosting aerobic capacity. Since publishing the study in 1997, Dr. Tabata’s name has been used to refer to a protocol of high-intensity interval training featuring 20-second work intervals followed by 10-second recovery intervals for eight cycles (a total of four minutes).  


If you ask most people what their general fitness goals, 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.

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