Strength

Muscle strength and endurance training are essential components of overall fitness. Your ability to perform daily tasks and strenuous physical tasks can be enhanced by strength training. As you read through this chapter think about the physical tasks you perform routinely in your job or at home, the strength needed to perform those tasks, and which exercises mimic those tasks. The focus of your strength training routine should be functional or applied strength for job-specific activities, military readiness, and injury prevention. This chapter outlines the principles of muscle strength and muscle endurance training and the proper use of exercise equipment to help you achieve your goals.

Strength

versus

Endurance

Muscle strength is the force your muscle or group of muscles can exert against resistance. As you lift and lower a weight your muscle must generate enough force to move that weight.

Muscle endurance is the ability of your muscles to repeatedly apply force to lift and lower a weight. Muscle endurance describes how long or how many times (number of repetitions) you can lift and lower a given weight.

Benefits of Strength Training

Strength training should complement aerobic training workouts because each type of training results in different benefits. General benefits of strength training include:

♦ Increased muscle strength and muscle endurance, greater lean
body mass, less body fat, and higher energy metabolism.

♦ Increased connective tissue (ligaments that hold bones to bones;
and tendons that hold muscles to bones) strength.

♦ Increased coordination and greater protection against injury.

♦ Increased self-esteem and less perceived stress.

♦ With respect to military readiness, greater muscle strength and
endurance translates into better performance of physically-
demanding, job-related tasks. Table 7-1 lists the strength
requirements needed to perform some physical tasks in the Navy.

Table 7-1. Strength Requirements in Navy Jobs

Strength Classification

(Percent of Navy Jobs)

High/High (23.9)%

High/Moderate (20.9%)

Moderate/Moderate (9.0%)

Moderate/Low (4.5%)

Low/Low (41.7%)

Strength and

Endurance

Requirements

Occasionally lift over 100 lbs (45 kg); Typically lift over 50 lbs (23 kg)

Occasionally lift 100 lbs (45 kg); Typically lift 50 lbs (23 kg)

Occasionally lift 80 lbs (36 kg); Typically lift 40 lbs (18 kg)

Occasionally lift 50 lbs (23 kg); Typically lift 25 lbs (11 kg)

Occasionally lift 20 lbs (9 kg); Typically lift 10 lbs (5 kg)

Examples of Some Occupational Codes

Artillery and Gunnery (GM); Aircraft Engines (AE) & Accessories (ABE); Construction (CM); Electricians (CE).

Machinists (MR); Food Service (MS); Supply Administration(SK); Teletype and Cryptographic Equipment (WT).

Air Crew (PR); Missile Guidance and Control (FC); Medical Care and Treatment (HM); Interior Communications (IC).

Musicians (MU); Supply Administration (AK).

Radio/Radar (ET); Sonar (OTA); Air Traffic Control (AC); Analysts (CTI); Information/Education (JO); Administration(YN).

Which classification in Table 7-1 best matches the requirements of your job? Which classification best describes your leisure activities?

Muscle Fiber Types

Before discussing strength training exercises and guidelines, here is a quick review of muscle physiology. To generate force, muscles contract. This action requires ATP (see Chapter 4, page 31). Muscle fibers are classified according to which energy system they use to make ATP. The three types of skeletal muscle fibers are:

♦ Slow Twitch Oxidative (Type I) fibers are mostly involved in
endurance activities. They rely on ATP from aerobic energy
metabolism (see page 31) and are generally resistant to fatigue.

♦ Fast Twitch Glycolytic (Type IIb) fibers are involved in quick,
strong muscle contractions and rely on the anaerobic energy
systems to produce ATP. These fibers are susceptible to fatigue.

♦ Fast Twitch Oxidative-Glycolytic (Type IIa) fibers are a cross
between the slow and fast twitch fibers since they rely on both
aerobic and anaerobic systems (see page 31) for energy.

Everyone has all three muscle fiber types; however, genetics determine which fiber type is more abundant in each person. Physical training can lead to changes in the characteristics of the muscle fibers. For example, endurance training makes the Type IIa fiber act more like the slow-twitch, Type I fiber.