Exercise Dosage and Progression
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Direct answer
Prescribing exercise obeys the same logic as prescribing a drug: the dose has a frequency, an intensity, a time and a type — the FITT principle — and changing any one variable changes the training effect. Strength work classically uses 60 to 80 per cent of one repetition maximum for roughly 8 to 12 repetitions across 2 to 4 sets, endurance uses loads below about 40 per cent with 15 to 25 repetitions, and aerobic training targets 60 to 80 per cent of heart-rate reserve or a Borg rating of perceived exertion of 12 to 16 on the 6-to-20 scale. Progression follows the overload principle in small increments once the current dose becomes comfortable, because specificity dictates that you adapt only to what you train, and reversibility erodes gains within weeks of stopping.
What you must remember
- FITT: frequency (aerobic 3-5 days/week, resistance 2-3 non-consecutive days), intensity, time (at least 150 minutes of moderate aerobic activity weekly per widely accepted guidance), type.
- Intensity anchors: 60-80% of heart-rate reserve by the Karvonen formula (target HR = resting HR + percentage × (max HR − resting HR)); Borg 6-20 scale where a rating of 12-14 is moderate and 15-16 vigorous; the Borg CR10 scale for dyspnoea and effort in respiratory patients.
- Strength dosing: 60-80% 1RM for 8-12 repetitions, 2-4 sets, 2-3 days per week, with about 2-3 minutes rest between sets for heavy loading; endurance dosing is 40-60% 1RM for 15-25 repetitions.
- Repetition maximum: 1RM is the heaviest load lifted once with good form; a 10RM is roughly 70-75% of 1RM — the standard conversion when testing a maximum is unsafe post-injury.
- Overload and progression: increase load, repetitions, sets, leverage or complexity by small steps only when the patient completes the current dose with good form and without next-day flare beyond roughly 2 out of 10 pain.
- Specificity: adaptations are mode-specific — isometrics raise isometric strength chiefly, eccentrics build eccentric control — so rehab must end in the patient's actual task.
- Reversibility: aerobic gains decay notably within about 2-4 weeks of detraining, muscle strength somewhat slower; illness-enforced bed rest in older adults can strip strength in days, a core argument for early mobilisation.
- Warm-up and cool-down: 5-10 minutes each, preparing tissue and blunting the post-exercise blood-pressure drop.
Turning a prescription into a progression — a worked knee case
A 45-year-old with patellofemoral pain three months after starting a desk job gives a clean example of dose evolution. Week one: isometric wall sits at 60° knee flexion, 5 × 30 seconds, plus closed-chain mini-squats to 45°, 3 × 10 — low load, high frequency, pain held under 2/10. When she performs 3 × 12 cleanly, load rises about 10 per cent or the leverage worsens (deeper squat, single-leg dip), never both at once, because two simultaneous jumps in demand outrun tissue adaptation. By six to eight weeks the programme must converge on her life goal — stairs without pain — through step-downs, then eccentric step-downs, then loaded stair ascent; this is specificity deciding content while overload decides quantity. Her aerobic dose of brisk walking 30 minutes on five days keeps the general FITT box ticked without inflating knee load. If a session flares pain beyond 24 hours, the rule is to step back one level, not abandon the ladder — the commonest self-inflicted failure in home programmes.
How exams and clinics test dosage
BPT theory papers ask candidates to "write the principles of exercise prescription and design a strength programme for a 50-year-old", expecting FITT, a percentage-based load, sets, repetitions, rest intervals and a progression criterion in that order; missing the progression criterion costs the application marks. Viva examiners probe the Borg scale by number — asking why the scale runs 6 to 20 (constructed so that rating × 10 approximates heart rate in healthy young adults), a detail that separates readers from memorisers. Clinically, Indian practice leans toward under-dosing: patients with arthritis are handed generic quadriceps sheets with no load, no repetitions and no review, so the overload principle never operates; writing an actual dose with a follow-up date is the professional habit examiners want reflected in the answer script.
Frequently asked questions
What does the FITT principle stand for?
Frequency, intensity, time and type — the four levers of exercise prescription, each of which can be progressed independently.
How is the Borg RPE scale used to set intensity?
On the 6-20 scale, a rating of 12-14 indicates moderate intensity and 15-16 vigorous intensity, roughly tracking heart rate when multiplied by ten in healthy adults.
What percentage of 1RM builds strength versus endurance?
Strength is trained at 60-80% of 1RM for 8-12 repetitions, while muscular endurance uses roughly 40-60% of 1RM for 15-25 repetitions.
How is target heart rate calculated by the Karvonen method?
Target HR equals resting HR plus the chosen percentage of heart-rate reserve (max HR minus resting HR), making it more individualised than straight percentages of max HR.
What is the reversibility principle?
Training adaptations decline when the stimulus stops — aerobic fitness drops noticeably within two to four weeks — which is why interruption, not incorrect exercise, most often defeats rehabilitation programmes.