Key Principles of Exercise Prescription

Why This Matters

Exercise prescription isn't just about telling someone to "work out more"—it's the science of designing individualized programs that produce specific physiological adaptations. You're being tested on your ability to apply foundational training principles (overload, specificity, progression) through systematic frameworks like FITT-VP, while understanding how to measure and monitor intensity using heart rate, RPE, and METs. These concepts form the backbone of how exercise professionals translate physiology into practice.

The exam will challenge you to prescribe appropriate exercise for different populations, calculate target heart rates, and justify your programming decisions based on established guidelines. Don't just memorize the numbers—know why we recommend 150 minutes of moderate activity, how the Karvonen formula accounts for individual fitness, and when to modify prescriptions for special populations. Master the principles, and the specific recommendations will make sense.

---

Foundational Training Principles

Before diving into specific guidelines, you need to understand the two principles that govern all training adaptations: the body adapts specifically to the demands placed upon it, but only when those demands exceed current capacity.

Overload Principle

• Progressive challenge beyond current capacity—fitness improves only when the body is stressed beyond its normal limits through increased intensity, duration, or frequency
• Gradual implementation prevents injury while ensuring continued adaptation; sudden jumps in training load are the primary cause of overuse injuries
• Applies to all fitness components—whether you're training cardiovascular endurance, muscular strength, or flexibility, the same principle governs improvement

Specificity Principle

• Adaptations mirror the training stimulus—endurance training improves aerobic capacity while resistance training builds strength; you get what you train for
• SAID principle (Specific Adaptation to Imposed Demands) means programs must align with individual goals, whether that's marathon performance or powerlifting
• Energy system specificity matters—sprinters train phosphagen and glycolytic pathways while distance runners emphasize oxidative metabolism

---

The FITT-VP Framework

This systematic approach ensures all variables of exercise prescription are addressed. Think of it as your checklist for comprehensive program design.

FITT-VP Principle

• Frequency, Intensity, Time, Type, Volume, Progression—the six variables that must be manipulated to create effective exercise prescriptions
• Volume is calculated as $\text{Frequency} \times \text{Duration}$ and must meet or exceed guidelines; this metric captures total training dose
• Progression is the systematic increase in training variables over time—essential for continued adaptation and avoiding the plateau effect

ACSM Cardiorespiratory Guidelines

• 150 minutes moderate OR 75 minutes vigorous aerobic activity per week—this is the minimum threshold for health benefits (memorize these numbers)
• Bout duration of at least 10 minutes counts toward weekly totals; accumulated activity throughout the day is physiologically valid
• Progressive overload in both duration and intensity over time prevents stagnation and continues driving cardiovascular adaptations

ACSM Resistance Training Guidelines

• 2-3 days per week targeting all major muscle groups with 48 hours recovery between sessions for the same muscles
• 2-4 sets of 8-12 repetitions optimizes both strength and hypertrophy; lower reps (1-6) emphasize strength while higher reps (15+) build endurance
• Proper form is non-negotiable—technique breakdown under fatigue is the primary mechanism for resistance training injuries

ACSM Flexibility Guidelines

• 2-3 days per week minimum, with stretches held for 15-30 seconds and repeated 2-4 times per muscle group
• Static stretching during cool-down when muscles are warm maximizes effectiveness; dynamic stretching belongs in the warm-up
• Breathing and relaxation during stretches activates the parasympathetic nervous system, reducing muscle tension and improving range of motion

---

Measuring Exercise Intensity

Intensity is the most critical variable to get right—too low and adaptations won't occur, too high and injury or burnout results. These three methods give you objective and subjective tools for monitoring effort.

Target Heart Rate Calculation

• Karvonen formula: $\text{Target HR} = [(\text{Max HR} - \text{Resting HR}) \times \%\text{Intensity}] + \text{Resting HR}$—this heart rate reserve method accounts for individual fitness levels
• Max HR estimation: $220 - \text{age}$ provides a quick estimate, though it has a standard deviation of ±10-12 bpm
• Intensity zones: 50-70% HRmax for moderate intensity, 70-85% HRmax for vigorous—these ranges correspond to different metabolic thresholds

Rating of Perceived Exertion (RPE)

• Borg scale (6-20) correlates roughly with heart rate when multiplied by 10; an RPE of 15 approximates 150 bpm
• Target RPE of 12-16 (somewhat hard to hard) indicates appropriate moderate-to-vigorous intensity without requiring equipment
• Subjective but valid—RPE captures factors heart rate misses, including psychological stress, sleep quality, and accumulated fatigue

Metabolic Equivalent (MET) Concept

• 1 MET = resting metabolic rate = approximately $3.5 \text{ mL O}_2/\text{kg/min}$—this is your baseline for comparing activity intensities
• Intensity classification: light activity <3 METs, moderate 3-6 METs, vigorous >6 METs—walking is ~3.5 METs, running ~8-10 METs
• Caloric estimation: $\text{kcal/min} = \text{METs} \times 3.5 \times \text{body weight (kg)} / 200$—useful for weight management prescriptions

---

Safety and Individualization

Effective prescription requires knowing who you're working with before determining what they should do. Risk stratification and population-specific modifications are where exercise science meets clinical judgment.

Pre-Exercise Screening and Risk Stratification

• Health history questionnaire identifies cardiovascular, metabolic, and renal risk factors before any exercise testing or programming begins
• ACSM risk categories (low, moderate, high) determine whether medical clearance is required—high-risk individuals need physician approval before vigorous exercise
• Current activity level assessment helps establish appropriate starting points; sedentary individuals require more conservative initial prescriptions

Special Populations Considerations

• Elderly: emphasize balance and fall prevention, low-impact aerobic activities, and flexibility; strength training is particularly important for maintaining functional independence
• Pregnant women: moderate-intensity exercise is beneficial, but avoid activities with fall risk or supine positions after first trimester; thermoregulation is a key concern
• Chronic disease: require medical clearance, start with low intensity, and progress gradually; monitor for adverse symptoms and adjust accordingly

---

Quick Reference Table

---

Self-Check Questions

1. How do the overload and specificity principles work together when designing a training program for a client who wants to improve both muscular strength and cardiovascular endurance?

2. A 40-year-old client has a resting heart rate of 70 bpm. Using the Karvonen formula, calculate their target heart rate range for moderate-intensity exercise (50-70% intensity).

3. Compare and contrast the three intensity monitoring methods (heart rate, RPE, METs)—when would you choose each one, and what are the limitations of relying on only one method?

4. Which FITT-VP variables would you modify first when progressing a beginner client who has been following the same program for 6 weeks, and why?

5. An FRQ presents a 65-year-old sedentary client with controlled hypertension seeking to begin an exercise program. What screening steps are required, and how would you modify standard ACSM guidelines for this individual?