Key Terms

The following definitions are provided for quick reference. Full context for each appears in the relevant section of the guide.

Anabolic Resistance

The blunted muscle protein synthesis response to a given protein dose and resistance training stimulus that occurs with ageing. Older muscle requires a higher protein dose than younger muscle to achieve the same MPS response, which is why protein targets in this guide increase for trainees over 50.

CNS Fatigue (Central Nervous System Fatigue)

A systemic impairment of the neural signals that recruit and co-ordinate muscle fibres, distinct from muscular fatigue or soreness. Can persist 24–72 hours after very heavy or high-volume sessions even when the muscles themselves feel recovered. Training through CNS fatigue impairs both performance and the quality of the adaptive stimulus.

Deload

A planned period — typically one week — during which training volume is reduced by approximately 40–50% while intensity is maintained or slightly reduced. Its purpose is to allow accumulated fatigue to dissipate and underlying fitness adaptations to be expressed. A deload is structural, not remedial — it should be scheduled in advance rather than taken reactively when performance declines.

DOMS (Delayed Onset Muscle Soreness)

The diffuse muscular aching that peaks 24–48 hours after exercise and typically resolves within 72 hours. Caused primarily by eccentric loading and associated connective tissue disruption. DOMS is a measure of novelty and eccentric demand, not of productive training stimulus. It declines as the body adapts to a given exercise — its absence does not indicate a less effective session.

Hypertrophy

An increase in the cross-sectional area of muscle fibres, resulting from mechanical tension, metabolic stress, and muscle protein synthesis during recovery. Hypertrophy is the primary mechanism of visible muscle growth and is distinct from strength, which is additionally determined by neural factors.

MAV (Maximum Adaptive Volume)

The training volume range — typically 15–20 sets per muscle group per week — at which adaptation is maximised. Training above MAV produces additional fatigue without proportional stimulus, eventually crossing into MRV.

MEV (Minimum Effective Volume)

The smallest training volume that produces measurable adaptation — approximately 10 sets per muscle group per week for most people with training history. Below MEV, training produces insufficient stimulus for meaningful adaptation.

Mesocycle

A structured training block of typically 4–8 weeks with a defined goal — typically hypertrophy, strength, or a combination — and a systematic approach to volume and intensity. A mesocycle ends with a deload, after which the next block begins at a slightly higher baseline volume.

MPS (Muscle Protein Synthesis)

The cellular process by which muscle fibres are rebuilt and enlarged following training-induced damage. Driven by mechanical tension and stimulated by adequate protein intake — particularly leucine. MPS peaks 24–48 hours post-session and returns to baseline within 48–72 hours, providing the mechanistic basis for training frequency recommendations.

MRV (Maximum Recoverable Volume)

The ceiling of training volume beyond which additional sets produce fatigue without additional adaptation — junk volume. MRV is highly individual and shifts with sleep quality, nutrition, life stress, and training history. Exceeding MRV consistently leads to non-functional overreaching.

NEAT (Non-Exercise Activity Thermogenesis)

The energy expended in all physical activity that is not structured exercise: walking, standing, fidgeting, stair climbing, and any other incidental movement. In most people, NEAT accounts for more total daily energy expenditure than formal exercise. Calorie restriction suppresses NEAT unconsciously, partially offsetting dietary deficits.

Progressive Overload

The systematic, ongoing increase in training demand over time. The non-negotiable mechanism behind all physical adaptation. Applied by increasing weight, reps, sets, or training density — or by improving technique such that each repetition imposes greater mechanical tension on the target muscle. Without progressive overload, adaptation stalls regardless of effort.

RIR (Reps in Reserve)

A measure of proximity to muscular failure within a set. 0 RIR indicates the next rep would fail; 2 RIR indicates two additional reps could be completed. Training in the 0–2 RIR range is the target for productive hypertrophy work. Most recreational lifters consistently underestimate how many reps remain, stopping sets 4–6 RIR rather than 1–2 RIR.

RPE (Rate of Perceived Exertion)

A subjective scale of effort, typically 1–10, where 10 represents maximal exertion. RPE 8 approximately corresponds to 2 RIR; RPE 9 to 1 RIR; RPE 10 to 0 RIR. Used in place of RIR where counting remaining reps is impractical.

SAID Principle (Specific Adaptation to Imposed Demands)

The principle that the body adapts specifically to the demands placed upon it. Running does not produce meaningful hypertrophy; curls do not improve squat strength; swimming does not build bone density equivalent to weight-bearing exercise. Training must include the specific movements and stresses associated with a given goal.

Supercompensation

The brief window, following a training stress and adequate recovery, during which fitness temporarily exceeds its previous baseline. Timing the next training session to coincide with this window — rather than too soon, before recovery completes, or too late, after the window passes — is how repeated training cycles compound into long-term progress.

VO2 Max

The maximum volume of oxygen the body can utilise per minute per kilogram of bodyweight. The single strongest predictor of cardiovascular mortality in large population studies. Improved primarily by high-intensity training at 90–100% of maximum heart rate sustained for 3–8 minutes. Declines with age in sedentary individuals but remains substantially trainable at any age.

Zone 2

The highest exercise intensity at which lactate production and clearance are in equilibrium — the maximal lactate steady state. Practically: conversation is possible but mildly uncomfortable. Heart rate typically 60–70% of maximum, though this is population-derived and individual variation is significant. The primary driver of mitochondrial density and fat oxidation when trained consistently at sufficient weekly volume.