Basic Principles of Exercise Training and Conditioning

Kevin R. Vincent

Heather K. Vincent

Craig K. Seto

INTRODUCTION

Participation in exercise is a critical component of healthful living and reduced all-cause mortality. Moderate-intensity physical activity is related to numerous health benefits, including musculoskeletal adaptation, increased circulatory capacity, and improvements in metabolism and body composition. Regular exercise induces central nervous system benefits (1), improves mood, and reduces stress.
The Centers for Disease Control and Prevention (CDC) and the American College of Sports Medicine^® (ACSM) now recommend that every U.S. adult accumulate 30 minutes or more of moderate-intensity physical activity on most — and preferably all — days of the week. Those who follow these recommendations will experience many of the health-related benefits of physical activity, and if they are interested in achieving higher levels of fitness, they will be ready to do so (2,3,7).
This chapter integrates and complements Chapters 5 (Basics in Exercise Physiology), 11 (Basics in Sports Nutrition), and 12 (Exercise Prescription), by specifically identifying appropriate principles for effective training to achieve the aforementioned fitness goals.

THE EXERCISE PRESCRIPTION AND TRAINING PROGRAM

Recommendations for Cardiorespiratory Endurance Training

Chapter 12 details current guidelines from ACSM; this chapter elaborates upon those recommendations and outlines the integration of these guidelines into a sequenced exercise program.

Mode

The best improvements in cardiorespiratory endurance occur when large muscle groups are engaged in rhythmic aerobic activity.
Variety facilitates enjoyment and enhances compliance.
Examples of activities include walking, jogging, cycling, rowing, stair climbing, aerobic dance (aerobics), water exercise, and cross-country skiing (2,3).

Intensity

The ACSM recommends that exercise intensity be prescribed within a range of 70%-85% of maximal heart rate (HR_max), 50%-85% of maximal volume of oxygen consumed per unit time ([V with dot above]O_2max), or 60%-80% of maximum metabolic equivalents (METs), or heart rate reserve (HRR).
- Because there is variability with the HR_max from age, the use of an actual heart rate (HR) from a graded exercise test is optimal.
- Lower intensities (40%-50% of[V with dot above]O_2max) elicit a favorable response in low-fit individuals, inpatient populations, and those with musculoskeletal pain.
Calculating intensity: The most common methods of setting the intensity of exercise to improve or maintain cardiorespiratory fitness use HR and rating of perceived exertion (RPE).
HR methods: HR is used as a guide to set exercise intensity because of the relatively linear relationship between HR and percentage of [V with dot above]O_2max (%[V with dot above]O_2max). It is best to measure HR_max during a progressive exercise test whenever possible because HR_max declines with age. HR_max can be estimated by using the following equation: (HR_max = 220 − age).
HR_max method: Using 70%-85% of an individual’s HR_max approximates 55%-75% [V with dot above]O_2max. Example: If HR_max = 180 bpm, then target HR (70%-85% HR_max) would range from 126 to 152 bpm. Given that there is variance around the HR of ± 15 bpm, the target HR should be calculated 10%-15% higher (7).
HRR method: The HRR method is also known as the Karvonen method. Target HR range = [(HR_max − HR_rest) × 0.60 and 0.85] + HR_rest. Using the HRR method allows a more direct correlation between HR and %[V with dot above]O_2max and accounts for the resting HR (7).
RPE: The use of the RPE scale to guide exercise intensity is increasingly used in research and in the clinical setting. RPE may be used with HR for regulating intensity or alone if HR monitoring is not available. The RPE scales can be used to track exercise intensity and muscle fatigue during the session. One of two scales can be used: a 6- to 20-point scale (6 = no
exertion, 20 = maximal exertion) and a 0- to 10-point scale (0 = no exertion, 10 = maximal exertion).
- For aerobic exercise, the onset of blood lactate generally occurs between 12 and 16 on the 6- to 20-point category scale and between 4 and 5 on the 0- to 10-point categoryratio scale (7).
- RPE is considered a reliable indicator of exercise intensity and is particularly useful when a participant is unable to monitor his or her pulse or when HR response to exercise has been altered by medications such as β-blockers (2,3).
- The average RPE range associated with physiologic adaptation to exercise is 12-16 (“somewhat hard” to “hard”) on the Borg category scale. One should suit the RPE to the individual on a specific mode of exercise and not expect an exact matching of the RPE to a %HR_max or %HRR. It should be used only as a guideline in setting the exercise intensity.

Duration

The ACSM recommends 30-60 minutes of continuous activity per session for fitness and an accumulation of > 30 minutes of activity per day for general health (7)
However, deconditioned individuals, older adults, or pregnant women with musculoskeletal discomfort may benefit from multiple, short-duration exercise sessions of < 10 minutes with frequent interspersed rest periods.

Frequency

The ACSM recommends that aerobic exercise be performed 3-5 days per week for fitness and physical activity be performed on most if not all days per week for general health (7).

Recommendations for Muscular Strength and Resistance Training

Overload and specificity are precepts of resistance training.
Overload occurs when a greater than normal physical demand is placed on muscles or muscle groups. Muscular strength and endurance are developed by increasing the resistance to movement or the frequency or duration of activity to levels above those normally experienced.
A training intensity of approximately 40%-60% of onerepetition maximum appears to be sufficient for the development of muscular strength in most normally active individuals (2,3). Lift intensity can be increased to near maximal if the goal is to increase muscle strength (7).
Specificity relates to the nature of changes (structural and functional, systemic and local) that occur in an individual as a result of training. These adaptations are specific and occur only in the overloaded muscle groups or muscles (3).
Unilateral and bilateral strengthening: Bilateral contractions induce less muscle activation per limb than unilateral contractions. Unilateral resistance exercise performed by one limb will induce training effects in the unexercised contralateral limb, termed “cross-transfer” or “cross-education” (6).
Combined endurance and resistance exercise: When endurance exercise is incorporated into a resistance exercise program, strength gains are not compromised when compared with resistance exercise alone (14).

ACSM Guidelines for Resistance Training

A 5- to 10-minute warm-up period consisting of aerobic activity (walking on a treadmill or stationary cycling) or a light set (50%-75% of training weight) of the specific resistance exercise should precede the resistance exercise program (2,3).
Mode: A minimum of 8-10 separate exercises that target major muscle groups (arms, shoulder, chest, abdomen, back, hips, and legs) is important for general strengthening. Free weights and weight machines are commonly used; however, springs, surgical or rubber tubing, and electronic devices are also used for resistance training. Choose different exercises for each body part every 2-3 training days where possible.
Intensity/duration: For general health, perform a minimum of one set of 8-12 repetitions of each of the exercises to the point of volitional fatigue. Volitional fatigue refers to the inability to move a resistance through the appropriate range of motion with proper mechanical form. A set of 10-15 repetitions is recommended for developing muscular endurance and for those who are older or frailer. Using the target RPE values of 15-16 in persons with high cardiovascular risk or chronic comorbidities is appropriate (2,3).
Progressive overload can be accomplished by increasing the load, increasing the repetitions for the current load, decreasing the rest period, or increasing the rest period with high loads (for strength and power development) (3).
Frequency: Perform these exercises 2-3 days per week, usually with a day of rest in between. Another option is to alternate resistance exercises for upper and lower body on every other day, if time is a constraint.
Progression: Resistance may be increased when the target repetition number can be completed with good technique and moderate effort (RPE rating of < 15).
Safety considerations:
- Perform every exercise in a controlled fashion through a full range of motion using proper technique during both concentric and eccentric phases.
- Maintain a normal breathing pattern and avoid breath holding (Valsalva maneuver).
- Exercise with a partner when possible for assistance and motivation; individuals achieve greater success with a successful exercise partner.
Children may safely participate in resistance exercise using sets of 8-15 repetitions, for one to three sets, using both open- and closed-chain exercises no more than twice a week (3). Heavy weights and maximal strength testing are discouraged in children because of adverse effects on the growth plate development. Form is more important than weight in this population.