The Iron Dictionary

The process by which muscle fibers increase in size in response to mechanical stress. When you lift, you create microscopic damage to muscle tissue. Your body repairs it bigger and stronger than before. That's hypertrophy in a nutshell.

There are two types: myofibrillar hypertrophy (denser, stronger fibers - more strength-focused) and sarcoplasmic hypertrophy (larger fluid volume in the cell - more size-focused, what bodybuilders chase). In practice, both happen together. The ratio just shifts depending on how you train.

Formally you'll hear resistance training most often as the umbrella term. When the focus is specifically on getting stronger (not just bigger), it's sometimes called neuromuscular training or maximal strength training. The distinction matters: strength is primarily a nervous system adaptation (motor unit recruitment, firing rate, intermuscular coordination), while hypertrophy is more about the muscle tissue itself.

You can train for both at once - that's most people's goal - but pure strength programs (like 5/3/1 or Starting Strength) look different from pure hypertrophy programs. Lower reps, heavier weight, longer rest periods for strength. Higher volume, moderate weight, shorter rest for size.

The gradual, systematic increase of stress placed on the body during training. Your body adapts to whatever you throw at it - so if you keep throwing the same thing, it stops adapting. Progressive overload forces continued adaptation.

Most people think it just means "add weight." But you can progressively overload by: adding reps at the same weight, adding sets, reducing rest time, improving range of motion, slowing the tempo, or improving technique (which allows more tension to reach the target muscle).

Training is organized into periods: a microcycle is usually one week. A mesocycle is a block of several weeks with a specific goal (accumulation, intensification, peaking). A macrocycle is the full training year or season.

In hypertrophy training, a typical mesocycle runs 4–6 weeks, volume builds progressively, and then you do a deload week before starting the next block at a slightly higher baseline. That's how the long-term curve keeps climbing.

A planned week (or more) of reduced training volume and/or intensity to allow accumulated fatigue to dissipate. This is not a "rest week" - you're still training. You're just pulling back enough to let your body actually absorb the adaptations you've been building.

Without deloads, you accumulate systemic fatigue that masks your actual fitness level. After a deload, people often hit PRs because the fatigue clears and the adaptation shows up.

The total amount of work done. The simplest way to track it: sets × reps × weight. Volume is one of the primary drivers of hypertrophy. More volume (up to a point) = more growth stimulus.

You'll also hear weekly volume per muscle group tracked as just sets (e.g., "10–20 hard sets per muscle per week"). That's the more practical way most coaches use it. Finding your MEV (Minimum Effective Volume) and MRV (Maximum Recoverable Volume) is a key part of smart programming.

Any movement that involves two or more joints and therefore recruits multiple muscle groups simultaneously. Compounds give you the most bang for your buck - they allow heavier loading, produce more total muscle stimulus, and release more anabolic hormones per session.

A movement that targets one specific muscle by limiting the action to a single joint. Isolations are used to address weak points, bring up lagging muscles, add volume without systemic fatigue, and finish a muscle off after compound work.

Performing two exercises consecutively without resting between them. You rest after both are done. Supersets save time and can increase metabolic stress on a muscle group.

Antagonist superset: Pair opposing muscle groups (e.g., bicep curl + tricep pushdown). One muscle rests while the other works. Agonist superset: Pair two exercises for the same muscle (e.g., face pull + lateral raise). More intense, more metabolic.

A rest-pause technique developed by Borge Fagerli. The idea: most of the hypertrophy stimulus in a set happens in the last few reps near failure (called effective reps). Myo-reps stack those effective reps efficiently.

How it works: Do an activation set to near failure (e.g., 12–15 reps). Rest 3–5 deep breaths. Do a mini-set of 3–5 reps. Rest again. Repeat 3–5 times. You're accumulating near-failure reps without the systemic fatigue of doing multiple full sets. Works best on isolation exercises and machines.

Rate of Perceived Exertion. A 1–10 scale for how hard a set felt. In strength training, RPE 10 = absolute max effort, couldn't do one more rep. RPE 9 = one rep left in the tank. RPE 8 = two reps left. And so on.

RPE is subjective but powerful. It auto-regulates training based on how you actually feel that day, not just what a spreadsheet says you should lift. Bad sleep, stress, poor nutrition - your RPE will tell you the weight needs to drop. Good day? Push into higher RPE territory.

Reps in Reserve. Directly related to RPE but expressed differently. RIR is the number of reps you could have done before hitting failure. RIR 0 = failure. RIR 1 = one rep left. RIR 2 = two reps left.

RIR is essentially the inverse of RPE. RPE 8 = RIR 2. Some coaches prefer RIR because it's more intuitive: "I had 2 reps left" is a cleaner mental image than a 10-point scale. Both are valid. You'll see both in programs.

Time Under Tension. The total time a muscle is under load during a set. Expressed as a tempo: e.g., 3-1-2-0 means 3 seconds eccentric (lowering), 1 second pause at bottom, 2 seconds concentric (lifting), 0 pause at top.

Longer TUT increases metabolic stress, which is one of the three mechanisms of hypertrophy. Deliberately slowing reps - especially the eccentric - creates more tension over more time, and the eccentric phase specifically causes more muscle damage. This is why slow negatives are so effective. Note: extreme TUT (very long sets) can compromise load, so there's a tradeoff.

These three volume landmarks come from Dr. Mike Israetel's (RP Strength) framework:

MEV (Minimum Effective Volume): The least amount of work that still produces results. If you're cutting or strapped for time, this is your floor.

MAV (Maximum Adaptive Volume): The sweet spot - where you get the most return for your effort. Not too little, not too much.

MRV (Maximum Recoverable Volume): The ceiling. More than this and you're just accumulating fatigue without additional adaptation. You'll start breaking down. This is individual and changes with training age, sleep, stress, and nutrition.

Non-Exercise Activity Thermogenesis. All the calories you burn through movement that isn't structured exercise - walking, fidgeting, doing dishes, taking the stairs. It sounds minor but NEAT can account for 200–1000+ calories per day depending on your lifestyle.

NEAT is highly variable and one of the sneakiest factors in body composition. When you diet, NEAT often drops unconsciously (you move less, fidget less, feel more sluggish). This is why caloric deficits don't always produce the expected results on a calculator. Deliberately walking more, taking the stairs, standing instead of sitting - all of that counts.

One Repetition Maximum. The maximum weight you can lift for exactly one rep with good form. It's the gold standard measure of absolute strength for a given movement.

You don't always need to test it directly (which is risky). Most programs use estimated 1RM calculated from rep max performance (e.g., if you can do 8 reps at 185 lbs, your estimated 1RM is around 225 lbs). Training percentages (e.g., "work at 75% of 1RM") are based on this number.

Your best ever performance on a given lift. PRs can be absolute (heaviest ever weight) or rep-based (most reps ever at a given weight, or a rep max at a specific rep count). Tracking PRs is one of the simplest and most motivating ways to see progressive overload working over time.

The phase of a movement where the muscle actively shortens while producing force. On a bicep curl, the concentric phase is curling the weight up. On a squat, it's standing back up. This is what most people think of as "the rep."

Concentric-focused training (fast lifting) develops power and strength. But the concentric alone leaves a lot of hypertrophy on the table - the eccentric is where most of the growth happens.

The phase where the muscle is lengthening while still under tension. On a bicep curl, it's lowering the weight back down. On a squat, it's the descent. The eccentric is where most muscle damage occurs - and muscle damage is one of the three primary drivers of hypertrophy.

Muscles are actually strongest in the eccentric phase (you can lower more than you can lift). This is why slow, controlled negatives are so valuable. Accentuated eccentrics (using a 3–5 second lowering phase) are one of the most evidence-backed tools for hypertrophy. This is also where DOMS comes from.

A contraction where the muscle is producing force but neither shortening nor lengthening. No joint movement. Holding a plank is an isometric. Pausing at the bottom of a squat. Squeezing a contraction at peak. Pushing against an immovable wall.

Isometrics have specific uses: building strength at specific joint angles, rehab, tendon loading (isometrics are particularly effective for tendinopathy), and adding intensity to isolation work through peak contractions. Less useful for overall hypertrophy volume but valuable as a tool.

When your palms are rotated to face upward or toward your body. On a barbell row, a supinated grip means palms face the ceiling. On a curl, palms face up at the top. Supination is driven by the forearm rotators (supinator muscle + biceps brachii - the biceps is actually a supinator first, flexor second).

Supinated grip tends to increase bicep activation in pulling movements and feels more natural for many curling patterns. Compare to pronated (palms down) and neutral (palms facing each other, also called hammer grip).

When your palms are rotated to face downward or away from your body. A standard overhand pull-up grip. The default grip on a lat pulldown. On a bent-over row, pronated means palms face the floor.

Pronated grip tends to emphasize the upper back and rear delts more in rowing patterns, and the brachialis/brachioradialis in curl variations (hammer and reverse curls). It's also typically harder to maintain for people with limited forearm mobility.

Range of Motion. The full arc a joint travels through during a movement. Full ROM means working through the entire available range - lengthened position to fully contracted. Partial ROM limits that arc.

Research strongly favors training through full ROM for hypertrophy, especially spending time in the lengthened position (stretch). Muscles trained under stretch produce more hypertrophic stimulus than those trained only in shortened or mid-range positions. This is why Romanian deadlifts, incline curls, and lengthened-position exercises deserve a place in programming.

A fundamental movement pattern where you push the hips back and fold forward, loading the posterior chain (glutes, hamstrings, lower back) rather than bending the knees into a squat. Deadlifts, RDLs, good mornings, and kettlebell swings are all hip hinge patterns.

Getting the hinge right is critical for back safety and for actually loading the glutes and hamstrings instead of the lower back. The spine stays relatively neutral (long, not rounded or hyperextended) while the hips drive the movement.

Bilateral: Both sides work simultaneously (barbell squat, bench press, conventional deadlift). Unilateral: One side at a time (Bulgarian split squat, single-arm row, pistol squat, single-leg RDL).

Unilateral work addresses side-to-side imbalances, improves balance and proprioception, and often allows better range of motion on the working limb. It also tends to produce more core activation. A well-designed program uses both.