# Exercise Prescription as Medicine: Principles for the Physiatrist

## Overview
Exercise is the single most evidence-based intervention in rehabilitation medicine. Physical inactivity is the fourth leading risk factor for global mortality (WHO). Exercise has proven benefits for cardiovascular disease, diabetes, cancer, depression, dementia, chronic pain, and virtually every chronic condition. Physiatrists are uniquely positioned to prescribe exercise for patients with disabilities and complex medical conditions. "Exercise is Medicine" initiative (ACSM): integrating physical activity into healthcare.

## FITT-VP Principles

### Frequency
Aerobic: 3-5 days/week (moderate intensity) or 3 days/week (vigorous). Resistance: 2-3 days/week per muscle group (48 hours between sessions for same group). Flexibility: 2-3 days/week minimum (daily is ideal). Neuromotor/balance: 2-3 days/week.

### Intensity
**Aerobic intensity methods**: Heart rate reserve (HRR/Karvonen method): Target HR = (HRmax - HRrest) x %intensity + HRrest. Moderate: 40-59% HRR. Vigorous: 60-89% HRR.

Rating of Perceived Exertion (RPE, Borg scale): 6-20 scale. Moderate: 12-13 ("somewhat hard"). Vigorous: 14-17 ("hard" to "very hard"). Talk test: moderate = can talk but not sing; vigorous = can only say a few words.

VO2 reserve: moderate = 40-59%, vigorous = 60-89%. METs: moderate = 3-5.9 METs, vigorous = ≥ 6 METs. **Resistance intensity**: 1-RM percentage: moderate = 60-70% 1RM, heavy = ≥ 80% 1RM. Repetitions to near-fatigue.

### Time (Duration)
Aerobic: 150-300 minutes/week moderate OR 75-150 minutes/week vigorous. Can be accumulated in bouts of ≥ 10 minutes. Resistance: 2-4 sets of 8-12 repetitions per exercise. Flexibility: 10-30 second hold per stretch, 2-4 repetitions.

### Type
Aerobic: walking, cycling, swimming, rowing, arm ergometry (adapt to ability). Resistance: free weights, machines, bands, body weight, functional movements. Flexibility: static stretching, dynamic stretching, PNF stretching. Neuromotor: balance exercises, yoga, tai chi, agility training.

### Volume
Total work performed (frequency x intensity x time). ACSM target: 500-1000 MET-minutes/week. Step count: 7,000-10,000 steps/day associated with significant health benefits.

### Progression
10% rule: increase volume by no more than 10% per week. Progress one variable at a time (duration before intensity). Overload principle: progressive increase in demand to drive adaptation. Individual response varies - adjust based on tolerance and outcomes.

| Component | Aerobic | Resistance | Flexibility | Neuromotor |
|-----------|---------|-----------|-------------|------------|
| Frequency | 3-5 days/week | 2-3 days/week | 2-3 days/week (daily ideal) | 2-3 days/week |
| Intensity | 40-89% HRR; RPE 12-17 | 60-80% 1RM | To point of tightness | Variable |
| Time | 150-300 min/week moderate | 2-4 sets × 8-12 reps | 10-30 sec hold × 2-4 reps | 20-30 min/session |
| Type | Walking, cycling, swimming | Free weights, bands, machines | Static, dynamic, PNF | Balance, yoga, tai chi |

<image>FITT-VP exercise prescription framework with aerobic, resistance, and flexibility parameters</image>

## Exercise Prescription for Chronic Disease

### Cardiovascular Disease
Aerobic exercise reduces all-cause mortality by 20-35%. Post-MI: start cardiac rehabilitation within 2-4 weeks. Heart failure (HFrEF): moderate-intensity aerobic + resistance training. HF-ACTION trial: improved functional capacity and quality of life.

Hypertension: aerobic exercise reduces SBP 5-8 mmHg; resistance reduces 2-3 mmHg. Peripheral arterial disease: supervised walking programs improve claudication distance.

### Type 2 Diabetes
Aerobic exercise improves insulin sensitivity for 24-72 hours. Resistance training independently improves glycemic control (HbA1c reduction ~0.5%). Combined aerobic + resistance superior to either alone. Goal: 150 min/week moderate aerobic + 2-3 days/week resistance.

Exercise timing: postprandial exercise optimizes glucose control. Monitor blood glucose before/after exercise (avoid hypoglycemia).

### Cancer
Exercise oncology: growing evidence for exercise as adjunctive cancer treatment. Reduces cancer-related fatigue (strongest evidence-based treatment). Reduces all-cause and cancer-specific mortality (breast, colon, prostate). Safe during and after chemotherapy/radiation (with appropriate modifications). ACSM guidelines: avoid exercise on days of severe fatigue or during active treatment toxicity.

### Depression and Anxiety
Exercise as effective as pharmacotherapy for mild-moderate depression. Dose-response relationship: more exercise = greater antidepressant effect. Both aerobic and resistance training are effective. Mechanism: endorphins, BDNF, serotonin/norepinephrine modulation, neuroplasticity. Barrier: anhedonia and low motivation - motivational interviewing is key.

### Chronic Pain
Exercise-induced hypoalgesia: activation of descending pain inhibition. Evidence-based for: low back pain, fibromyalgia, osteoarthritis, chronic widespread pain. Graded exercise approach: start well below symptom threshold, progress gradually. May initially flare pain (educate patients this does not mean harm).

### Osteoporosis
Weight-bearing and resistance exercise improve bone mineral density. Impact/jumping exercises: most osteogenic stimulus. Balance training: fall prevention (most important for fracture reduction). Tai chi: reduces fall risk by 30-50%.

<image>Exercise prescription modifications for common chronic diseases including cardiovascular disease, diabetes, and cancer</image>

## Adapting Exercise for Disability Populations

### Spinal Cord Injury
SCI-specific guidelines (ACSM/NSCISC): Aerobic: 20-30 min, 3x/week moderate intensity (arm ergometry, wheelchair sports, swimming). Resistance: 2-3x/week, major accessible muscle groups. Thermoregulation considerations (impaired sweating below injury level).

Autonomic dysreflexia awareness during intense exercise (T6 and above). Functional electrical stimulation (FES) cycling for lower extremity exercise. Body weight-supported treadmill training.

### Stroke
Post-stroke exercise guidelines: aerobic + resistance + flexibility + balance. Aerobic: 20-60 min, 3-5 days/week, 40-70% HRR. Start with supervised, low-intensity programs. Address barriers: hemiparesis, balance deficits, fatigue, cardiac comorbidities.

Task-specific training overlaps with therapeutic exercise. Recumbent steppers, seated cycling, aquatic exercise as adaptations.

### Amputation
Pre-prosthetic: upper body conditioning, core strengthening, single-leg exercises. Post-prosthetic: progressive gait training, balance, aerobic endurance. Phantom limb pain may be modulated by exercise. Energy cost of ambulation increases with higher amputation level.

### Intellectual and Developmental Disabilities
Often excluded from exercise programming despite high rates of obesity and cardiometabolic disease. Adapt instructions: simple, visual cues, repetitive routines. Special Olympics Healthy Athletes program. Group-based programs improve adherence and social inclusion.

### Neuromuscular Disease
Exercise must be carefully prescribed to avoid overwork weakness. Moderate submaximal exercise is generally safe in most NMDs. Avoid eccentric loading in muscular dystrophies. Aquatic therapy well-tolerated. Monitor CK levels if concerned about muscle damage.

## Motivational Interviewing for Behavior Change

### Key Principles
Express empathy: understand patient's perspective without judgment. Develop discrepancy: help patient recognize gap between current behavior and goals. Roll with resistance: avoid arguing or confronting. Support self-efficacy: reinforce patient's ability to change.

### Stages of Change (Transtheoretical Model)
**Precontemplation**: not considering exercise; provide information without pushing. **Contemplation**: thinking about it; explore pros/cons, address barriers. **Preparation**: planning to start; help set specific, achievable goals. **Action**: actively exercising; reinforce behavior, troubleshoot barriers. **Maintenance**: sustained exercise; prevent relapse, celebrate success.

### SMART Goal Setting
**S**pecific: walk for 20 minutes. **M**easurable: 3 times per week. **A**chievable: realistic given current fitness and abilities. **R**elevant: aligned with patient's values and functional goals. **T**ime-bound: achieve within 4 weeks.

### Overcoming Barriers
Time: incorporate into daily routine (walking meetings, active commute). Pain: graded approach, educate on difference between harm and discomfort. Fatigue: schedule exercise during peak energy, start low. Access: home exercise programs, free community resources, telehealth coaching.

Motivation: exercise buddy, group classes, tracking technology. Disability-specific: adaptive equipment, accessible facilities, FES.

<image>Motivational interviewing framework and stages of change model applied to exercise prescription in rehabilitation</image>

## Prescribing Exercise in Practice

### The Exercise Prescription
Write it like a medication prescription: Type of exercise. Frequency and duration. Intensity (with specific metric: HR, RPE, or talk test).

Progression plan. Precautions and contraindications. Follow-up plan. Referral to physical therapist, exercise physiologist, or certified fitness professional for implementation. Community-based programs: cardiac rehab, pulmonary rehab, cancer exercise programs, adapted fitness.

### Pre-Exercise Screening
ACSM pre-participation screening algorithm (2015 update): Current exercise participation status. Known cardiovascular, metabolic, or renal disease. Signs/symptoms of disease.

Most patients can begin light-to-moderate exercise without medical clearance. Exercise testing indicated for: previously sedentary with known CVD/metabolic disease starting vigorous exercise.

### Monitoring and Follow-Up
Track functional outcomes (6-minute walk test, timed up and go, grip strength). Activity tracking devices (pedometers, accelerometers, smartwatches). Regular follow-up to adjust prescription (every 4-8 weeks initially). Address barriers and modify program as needed.

## Clinical Pearls
Exercise is the most broadly effective intervention in PM&R - it should be discussed at every patient encounter, regardless of the diagnosis. RPE (Borg scale) is the most practical intensity measure for rehabilitation patients, especially those on beta-blockers or with autonomic dysfunction where heart rate response is unreliable. Start low and go slow, but always progress - the most common prescribing error is failing to increase intensity over time. The biggest predictor of exercise adherence is enjoyment - help patients find activities they actually like, not just activities that are "good for them". For patients with central sensitization or chronic pain, education that exercise-related discomfort does not equal tissue damage is essential before prescribing.

## References
- American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription. 11th ed. Wolters Kluwer; 2021.
- Pedersen BK, Saltin B. Exercise as medicine - evidence for prescribing exercise as therapy in 26 different chronic diseases. Scand J Med Sci Sports. 2015;25(Suppl 3):1-72.
- Martin Ginis KA, et al. Evidence-based scientific exercise guidelines for adults with spinal cord injury. Spinal Cord. 2018;56(8):780-790.
- Billinger SA, et al. Physical activity and exercise recommendations for stroke survivors: AHA/ASA statement. Stroke. 2014;45(8):2532-2553.
- Campbell KL, et al. Exercise guidelines for cancer survivors: consensus statement from international multidisciplinary roundtable. Med Sci Sports Exerc. 2019;51(11):2375-2390.