11.2 Aerobic Exercise Prescription: FITT-VP, Intensity Monitoring & Progression
Key Takeaways
The FITT-VP framework specifies frequency, intensity, time, type, volume, and progression for every aerobic prescription.
The Karvonen method sets target heart rate as a percentage of heart rate reserve added back to resting heart rate, which is more individualized than a percentage of maximal heart rate.
Public health guidance targets at least 150 minutes per week of moderate-intensity or 75 minutes of vigorous-intensity aerobic activity.
The Borg rating of perceived exertion scale runs from 6 to 20, with 12 to 14 corresponding to moderate intensity.
Perceived exertion and the talk test remain valid when heart rate does not, including in patients on beta-blockers or with pacemakers.
11.2 Aerobic Exercise Prescription: FITT-VP, Intensity Monitoring & Progression
Core Clinical Mandate: An aerobic prescription is as specific as an ultrasound prescription. "Do some cardio" is not a treatment plan. The FITT-VP framework forces every variable to be stated, documented, and progressed.
The FITT-VP Framework
| Variable | Definition | Typical Starting Point for a Deconditioned Adult |
|---|---|---|
| Frequency | Sessions per week | 3 to 5 days per week; daily for very low intensity |
| Intensity | How hard | Light to moderate — roughly 40 to 60% of heart rate reserve, or RPE 11 to 13 |
| Time | Duration per session | 10 to 20 minutes, accumulated in bouts if needed |
| Type | Mode | Walking, cycling, aquatic exercise, elliptical — chosen for joint tolerance and adherence |
| Volume | Total dose (frequency × intensity × time) | Often expressed as MET-minutes per week |
| Progression | How the dose advances | Extend duration first, then frequency, then intensity |
General population targets: at least 150 minutes per week of moderate-intensity aerobic activity, or 75 minutes per week of vigorous-intensity activity, or an equivalent combination — commonly spread across at least three days, with additional benefit up to roughly 300 minutes per week.
Bout structure: total accumulated volume is what matters most. Three 10-minute walks deliver meaningful benefit for a patient who cannot tolerate a continuous 30-minute session, and starting with accumulated bouts is a legitimate and well-supported strategy.
Three Ways to Set Intensity
1. Percentage of Heart Rate Reserve — the Karvonen Method
Worked example. A 50-year-old with a resting heart rate of 70 bpm, prescribed 60% intensity:
- Estimated HRmax = 220 − 50 = 170 bpm
- Heart rate reserve = 170 − 70 = 100 bpm
- 60% of reserve = 60 bpm
- Target heart rate = 60 + 70 = 130 bpm
Karvonen is preferred over a plain percentage of maximal heart rate because it anchors to the individual's resting heart rate and therefore tracks fitness. Note that the plain percentage-of-maximum method would have given 0.60 × 170 = 102 bpm — a substantially lighter and less appropriate stimulus for the same nominal "60%."
| Intensity Classification | % Heart Rate Reserve | % HRmax | Borg RPE (6–20) |
|---|---|---|---|
| Very light | <30% | <57% | <9 |
| Light | 30–39% | 57–63% | 9–11 |
| Moderate | 40–59% | 64–76% | 12–13 |
| Vigorous | 60–89% | 77–95% | 14–17 |
| Near-maximal | ≥90% | ≥96% | ≥18 |
2. Rating of Perceived Exertion
The original Borg RPE scale runs from 6 to 20, designed so that multiplying the rating by ten approximates heart rate in a healthy young adult (RPE 13 ≈ 130 bpm). Landmarks: 6 = no exertion at all, 9 = very light, 11 = light, 13 = somewhat hard, 15 = hard, 17 = very hard, 20 = maximal exertion. A separate Borg CR10 category-ratio scale runs 0 to 10 and is used more often for dyspnoea and pain.
RPE is the intensity tool of choice whenever heart rate is unreliable: beta-blockers and other rate-limiting medications, pacemakers, atrial fibrillation, autonomic neuropathy, and transplanted hearts.
3. The Talk Test
- Moderate intensity: the patient can talk in full sentences but cannot sing.
- Vigorous intensity: the patient can only manage a few words before needing a breath.
Crude but remarkably robust, free, and immediately teachable for home programs.
Session Structure
- Warm-up — 5 to 10 minutes of light aerobic activity. This is not optional. Warm-up raises muscle temperature and enzyme activity, increases tissue extensibility, and, critically, allows coronary blood flow to increase in step with myocardial demand. Abrupt high-intensity onset without warm-up is associated with ischaemic ST-segment changes even in asymptomatic individuals.
- Conditioning phase at the prescribed intensity and duration.
- Cool-down — 5 to 10 minutes of gradually decreasing activity. During exercise the skeletal muscle pump is a major contributor to venous return. Stopping abruptly removes that pump while peripheral vasodilation persists, causing venous pooling, a fall in venous return, and post-exercise hypotension or syncope. A gradual cool-down is also the period of greatest arrhythmia risk in cardiac patients, so it is supervised rather than skipped.
- Flexibility work is best placed after the cool-down, when tissue temperature is elevated.
The Cool-Down Rule: Never let a patient go straight from vigorous exercise to a hot shower or to standing still. Peripheral vasodilation plus a lost muscle pump is the classic setup for exertional syncope.
Continuous vs. Interval Training
| Continuous (steady-state) | Interval | |
|---|---|---|
| Format | Sustained submaximal effort, 20–60 minutes | Alternating work and recovery bouts |
| Advantages | Simple, predictable, good for building base volume | Accumulates more time at higher intensity; better tolerated by symptom-limited patients |
| Rehabilitation use | Default starting format | Excellent for claudication, chronic obstructive pulmonary disease, and cardiac patients who cannot sustain continuous work |
| Caution | Can be monotonous; adherence issues | Higher intensity requires screening, supervision, and controlled progression |
For a severely deconditioned patient, interval formats are often the easier option, not the harder one: two minutes of walking alternating with one minute of rest accumulates far more total work than a failed attempt at continuous walking.
Progression Rules
- Change one variable at a time, so that any adverse response is attributable.
- Extend duration before increasing intensity. Increase total weekly time by roughly 5 to 10% per week in the initial conditioning stage.
- Three stages: initial conditioning (roughly the first 4 to 6 weeks, emphasising tolerance and technique), improvement (progressive increases over several months), and maintenance (holding the achieved dose indefinitely).
- Older and deconditioned adults progress more slowly and benefit from longer warm-ups, lower starting intensity, and non-weight-bearing or aquatic modes where joint pain limits walking.
- Stop or reduce for: chest discomfort, unusual dyspnoea, dizziness or light-headedness, palpitations or an irregular pulse, unusual fatigue, claudication beyond the prescribed threshold, or a fall in systolic blood pressure during increasing workload.
Mode Selection in Musculoskeletal Practice
| Patient Problem | Preferred Mode | Reason |
|---|---|---|
| Knee or hip osteoarthritis | Cycling, aquatic exercise, elliptical | Reduced joint compression and impact |
| Lumbar spinal stenosis | Stationary cycling (flexed posture), or treadmill with incline | Flexion opens the canal and relieves neurogenic claudication |
| Lumbar disc derangement, extension-biased | Walking, upright modes | Avoids sustained flexion loading |
| Plantar fasciopathy | Cycling, swimming, upper-body ergometer | Offloads the plantar fascia during the irritable phase |
| Deconditioned with balance impairment | Recumbent cycle, aquatic exercise | Removes fall risk from the aerobic stimulus |
Integrate, Do Not Bolt On: In a musculoskeletal plan of care, the aerobic prescription should be chosen so that it does not aggravate the presenting complaint and preferably assists it. Prescribing treadmill walking to a patient with irritable neurogenic claudication will fail; prescribing a flexed-posture stationary cycle will not.
A 50-year-old patient has a resting heart rate of 70 beats per minute. Using the Karvonen heart rate reserve method with an age-predicted maximum and a target of 60 percent intensity, what is the target heart rate?
102 beats per minute
112 beats per minute
130 beats per minute
150 beats per minute
Why must a patient with known cardiovascular disease perform a gradual cool-down rather than stopping abruptly after aerobic exercise?
Abrupt cessation causes immediate muscle glycogen depletion and delayed onset muscle soreness
The skeletal muscle pump stops while peripheral vasodilation persists, reducing venous return and risking post-exercise hypotension, syncope, and arrhythmia
Cool-down is required to prevent lactic acid from crystallizing within the muscle belly
Cool-down raises core temperature further, which is necessary for the training adaptation to occur
A patient taking a beta-blocker is beginning an aerobic conditioning program. Which intensity monitoring method is most appropriate?
Percentage of age-predicted maximal heart rate, because beta-blockers do not affect submaximal heart rate
Rating of perceived exertion combined with the talk test, because heart rate response is pharmacologically blunted
Counting steps per minute, because cadence is a direct proxy for oxygen consumption
Blood lactate sampling at every session, because it is the only valid alternative
A severely deconditioned patient cannot sustain more than four minutes of continuous walking. Which prescription best builds aerobic volume?
Insist on a single continuous 30-minute walk daily, since only continuous exercise produces cardiovascular adaptation
Prescribe interval walking — for example two to four minutes of walking alternating with one minute of rest — and accumulate bouts across the day, progressing duration before intensity
Begin with vigorous interval sprints to maximize the training stimulus in the shortest time
Defer all aerobic exercise until the patient has completed twelve weeks of resistance training
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