Exercise Intensity for Resistance Training

Training variables = every modifiable element of a program
- Manipulating them → specific physiologic adaptation (strength, hypertrophy, power, speed, etc.)
Load
- Magnitude of external resistance (mass or weight on implement)
- Absolute value (e.g., lifting $100\,\text{lb}$ is the same load for everyone)
Intensity
- Always relative to the individual
- Two complementary views:
- Load-centric: % of the individual’s one-repetition maximum (1-RM)
  - $100\%\,\text{1-RM}$ = maximal possible load for that exercise
- Effort-centric: how hard the set feels (perceived exertion) or proximity to task failure
- Tight coupling with load, but not perfectly correlated (two people may report very different effort at the same external weight)

Definition: Point when no further repetition can be completed with the agreed-upon technique despite maximal effort
Physiologic drivers
- Peripheral fatigue: metabolite accumulation, substrate depletion
- Central nervous system fatigue: reduced motor output, motivation drop
Volitional nature
- Lifters typically self-terminate just before true physiologic failure for safety
- Altering ROM, speed, pausing, or reducing load = new task, not “beyond failure”

RM = heaviest load controllable through full ROM for a specific rep number
Testing sequence
- Health screening → decide 1-RM vs. multi-RM
- General warm-up, then specific warm-up sets with incremental load increases
- Adequate rest (~2–5 min) between attempts to avoid fatigue masking true strength
- Stop when full ROM or form can’t be maintained
Contra-indications / caution
- Joint pathology, soft-tissue injury risk, osteoporosis, cardiovascular conditions
- Beginners lacking motor skill

Movement velocity / technical observation
- Coach watches bar speed & form; if speed drops outside a pre-set bandwidth, load reduced
- Tech aids: video, motion capture, linear position transducers
- Subjective & expertise-dependent
Mathematical estimation from sub-max sets
- Epley: $\text{1-RM}=w\,(1+0.0333\,r)$
- Brzycki: $\text{1-RM}=\dfrac{w}{1.0278-0.0278\,r}$
- Pros: safer, faster; Cons: error grows with high rep counts, ignores individual fiber type/fatigue profile
Velocity-based resistance training (VBRT)
- Measures bar speed to infer %1-RM and autoregulate load
- Pros: precise, instant feedback, motivation
- Cons: cost, technical know-how, data overload, limited for mixed-plane or ballistic lifts
Perceptual/self-report methods
- Rating of Perceived Exertion (RPE)
- Repetitions in Reserve (RIR)

Scales
- Original Borg 6–20 (aerobic), later Borg CR10 (0–10)
- Resistance training commonly adopts 0–10 or 1–10 anchors
- 10 = maximal effort / failure; 0 = complete rest
Administration
- Assigned at end of set; describes effort of the LAST rep
- Visual, numerical, or descriptive anchors equally validated
Integration in programming
- Can prescribe: (1) load + RPE, (2) reps + RPE, or (3) load + reps
- CANNOT predetermine load + reps + RPE simultaneously (one must float)

Definition
- Immediate post-set estimate of additional perfect-form reps possible before failure
- $\text{RIR}=0$ → task failure; $\text{RIR}=2$ → could have done two more
Interpretation
- Lower RIR = higher intensity; Higher RIR = moderate intensity, better for volume or recovery
Utility
- Tracks fatigue, autoregulates daily load, complements RPE (inverse relation)

Empirical trend (conceptual, not absolute):
- RPE 10 ↔ RIR 0 ↔ ≈ $100\%\,\text{1-RM}$ for a single rep; ≈ $75–80\%$ for 10 reps
- Each 1-point RPE drop ≈ +1 RIR or −1 rep from failure

Bench-press case study
- 100 kg × 10 reps → RPE 10 (true 10-RM)
- 75 kg × 10 reps → RPE 7 → ~3 RIR (≈3 reps from failure)
Strength block prescription
- Goal: 3 sets × 5–6 reps @ RPE 8
- Set 1: 80 kg × 6 reps, RPE 8 (2 RIR)
- Set 2: 80 kg × 5 reps, RPE 9 (1 RIR) after only 2-min rest → fatigue evident
- Set 3: 80 kg × 5 reps, RPE 8 after 3-min rest → performance restored
- Lesson: manipulate rest intervals to keep targeted effort range
Knee-extension progression template
- Maintain RPE 8–9 (≈RIR 1–2), add load or reps weekly within 1–6 rep range
- Merely increasing RPE ≠ progression; performance (load/reps) must rise

Effort perception, not load magnitude, is judged: 1 rep @ RPE 8 should “feel” identical in effort to 5 reps @ RPE 8
Intermediate ratings (e.g., 8.5) permissible when uncertain
Accuracy improves:
- Closer proximity to failure (≤RIR 3)
- Greater training & scale experience
Anchoring technique: occasional safe sets to actual failure calibrate internal scale
Beginners
- Still usable; coach may set conservative targets (e.g., prescribe RIR 3–4 and adjust load week-to-week)

Self-regulation (stopping before failure) reduces injury & overtraining risk
Adequate warm-up, technique standardization, and supervision are mandatory in any RM or RPE-anchoring effort
Overreliance on technology or formulas can mask real-time performance cues; blend objective & subjective data

Load and intensity are distinct but inter-related; intensity can be framed as %1-RM or proximity to failure
True 1-RM testing has meaningful downsides; numerous safer proxies exist (RPE/RIR, formulas, VBRT)
RPE & RIR are validated, versatile, low-cost tools for monitoring & programming resistance training intensity across settings
Prescription flexibility: manipulate two variables (load, reps, RPE/RIR); allow the third to self-organize to hit the target effort
Continual progression demands increases in performance (load or reps) at a given effort level, not simply higher perceived effort