| Recommended weekly aerobic activity (moderate intensity) | 150–300 minutes (U.S. Department of Health and Human Services Physical Activity Guidelines for Americans, 2nd edition) |
| Recommended strength training sessions per week | 2 or more (U.S. Physical Activity Guidelines for Americans) |
| Standard HIIT work-to-rest ratio (common example) | 1:2 (e.g., 20 sec on, 40 sec off) (General exercise science convention; ratios vary by protocol) |
| DOMS onset window | 24–72 hours post-exercise (American College of Sports Medicine) |
| RPE scale range | 1 (rest) to 10 (maximum effort) (Adapted Borg CR10 scale, widely used in exercise science) |
Why Fitness Vocabulary Matters
Walk into any gym, open a fitness app, or read a workout plan and you'll encounter a stream of shorthand: 3×10, AMRAP, tempo, RPE 7. For many people — especially those just getting started or returning after a break — this language creates an invisible barrier. It signals that fitness is complicated, exclusive, or only for people already in the know.
It isn't. Most fitness terminology describes simple ideas that you likely already understand intuitively. Knowing the words just helps you follow instructions more accurately, ask better questions, and feel more at home in any exercise environment.
This glossary covers the terms you're most likely to encounter in workout programs, group classes, or conversations with fitness professionals. Use it as a reference you can return to whenever something is unclear. For a similar plain-language approach applied to financial terminology, see our savings and debt glossary.
This Article Is General Health Information
The definitions and explanations in this glossary are for educational purposes only and do not constitute medical or exercise advice tailored to your individual health situation. Before starting or significantly changing any physical activity program, consult a qualified healthcare provider or certified fitness professional — especially if you have an existing health condition or injury.
Core Terms: Structure of a Workout
These are the building blocks that almost every structured exercise plan uses. Understanding them helps you decode nearly any written workout.
| Recommended weekly aerobic activity (moderate intensity) | 150–300 minutes (U.S. Department of Health and Human Services Physical Activity Guidelines for Americans, 2nd edition) |
| Recommended strength training sessions per week | 2 or more (U.S. Physical Activity Guidelines for Americans) |
| Standard HIIT work-to-rest ratio (common example) | 1:2 (e.g., 20 sec on, 40 sec off) (General exercise science convention; ratios vary by protocol) |
| DOMS onset window | 24–72 hours post-exercise (American College of Sports Medicine) |
| RPE scale range | 1 (rest) to 10 (maximum effort) (Adapted Borg CR10 scale, widely used in exercise science) |
Reps and sets are the fundamental units of resistance training. If a plan says 3 sets of 12 reps, you perform the exercise 12 times in a row, rest, and repeat that sequence twice more. The rest period between sets is intentional — its length shapes the training effect. Shorter rests (30–60 seconds) tend to emphasize muscular endurance; longer rests (2–3 minutes) support maximal strength development.
Progressive overload is the principle that keeps workouts productive over time. The body adapts to any repeated stimulus; without gradually increasing the challenge, progress stops. This doesn't always mean adding weight — more reps, a slower tempo, or a shorter rest interval all count.
Compound movements like squats, deadlifts, rows, and presses recruit large amounts of muscle simultaneously and are the backbone of most efficient programs. Isolation exercises — think bicep curls or calf raises — target a single muscle and are useful for addressing specific weaknesses or imbalances after compound work.
Cardio, Effort, and Recovery Terms
Cardiovascular fitness and recovery have their own vocabulary that appears frequently in class descriptions, wearable device readouts, and program guidelines.
HIIT (High-Intensity Interval Training) has become one of the most common workout formats. The core concept is simple: alternate between hard effort and recovery. The ratio of work to rest, and the intensity of the work intervals, can vary widely depending on the protocol.
VO2 max is a number that appears on many fitness trackers. It represents your aerobic ceiling — how efficiently your body uses oxygen at peak output. While elite athletes train specifically to raise this number, for most everyday movers it's a general reference point for cardiovascular fitness rather than a training target.
RPE (Rate of Perceived Exertion) is arguably more practical for everyday exercisers than precise heart rate zones. It anchors effort to how you feel — a 6 out of 10 might be a brisk walk that lets you hold a conversation; a 9 is near your limit. It's a flexible, self-calibrating tool.
DOMS (Delayed Onset Muscle Soreness) is the stiffness and ache that typically peaks one to two days after an unfamiliar or intense session. It's a normal response to microscopic muscle stress that precedes adaptation — not a sign of injury in most cases. If soreness is severe, localized sharply, or doesn't resolve within a few days, consult a healthcare professional.
Mobility is worth distinguishing from flexibility. Flexibility is how far a muscle can passively lengthen; mobility is how well you can actively control movement through a joint's range. Both matter, but mobility training — often involving slow, controlled movement — tends to translate more directly into functional fitness. If you're looking to understand how consistent habits form around these concepts, this guide on why fitness routines fall apart is a useful companion read. For nutrition vocabulary that supports your activity, explore the Everyday Nutrition hub.
This article is for informational purposes only and does not constitute medical or exercise advice. Always consult a qualified healthcare or fitness professional before beginning or significantly modifying a physical activity routine.