Chapter 9 9 Muscular Fitness: Strength and Endurance C H A P T E R

Objectives This chapter will help you do the following: Identify the components of muscular fitness Understand the factors that influence strength Differentiate between strength and muscular endurance Understand the importance of flexibility Determine how muscular fitness contributes to health, total fitness, and performance Understand how a bout of training leads to changes in muscles Identify the specific changes that result from strength or endurance training Evaluate the importance of flexibility exercises Understand how to minimize muscle soreness See how speed and power training improve performance See how core training contributes to health and performance

Muscular Strength The maximal force that can be exerted in a single voluntary contraction Factors influencing strength –Sex –Age –Muscle fiber types Measures of strength –Dynamic versus static strength

Muscular Endurance Defined and measured as the repetition of submaximal contractions or submaximal holding time (static or isometric endurance) Muscular versus aerobic endurance Muscular endurance versus muscular strength

Flexibility The range of motion through which the limbs are able to move What restricts motion? Does stretching improve performance? MSSE 2011 shows no adverse impact or improvement in performance.

Other Components of Muscular Fitness Speed: Rapid acceleration Power: Combination of strength (force) and speed Agility: Ability to change position and direction rapidly Balance: Static (stationary) or dynamic (while in motion) Neuromuscular coordination: Practice makes permanent. Perfect practice makes perfect.

Muscular Fitness Adaptations Overload principle For improvements to take place, workloads have to impose a demand (overload) on the body system (above two-thirds of maximal force for strength). As adaptation to loading takes place, more load must be added. Improvements are related to the intensity (tension for strength), duration (repetitions), and frequency of training. (continued)

Muscular Fitness Adaptations (continued) Overload training leads to adaptations in the muscles according to the type of training (specificity). –Strength training: increased size because of increases in contractile proteins (actin and myosin) and tougher connective tissue –Muscular endurance training: improved aerobic enzyme systems, larger and more numerous mitochondria (increased mitochondrial density), and more capillaries (continued)

Muscular Fitness Adaptations (continued) How do the training stimuli change the muscle? –Not entirely clear. One explanation says training probably signals the nucleus to make messenger RNA (mRNA), which is sent into the muscle fiber to order the production of specific proteins (contractile protein for strength training, aerobic enzyme protein for endurance training). Another RNA (transfer RNA, or tRNA) gathers up the amino acids needed to construct the desired protein, transports them to the ribosome, and places them in the growing chain of amino acids that become a specific protein. (continued)

Muscular Fitness Adaptations (continued) We don’t yet know whether tension, metabolic activity, hormones, or a combination of factors signal the nuclei; therefore, we are unable to trick the muscle into getting stronger or building endurance without training.

Strength-Endurance Continuum

Muscular Endurance Training Fiber type transformation Methods of training –Static (isometric) training –Dynamic (isotonic) training –Isokinetic training

Flexibility Static stretching Contract/relax stretch Dynamic stretch

Muscle Soreness DOMS (delayed-onset muscle soreness) Possible causes –Slight tears in connective tissue –Uncontrolled contractions or spasms of individual muscle fibers –Muscle fiber damage –Lingering effects of metabolic by-products Not due to leftover lactic acid

Figure 9.3 Force–Velocity Relationship

Preload and Elastic Recoil The stretch, or preload, does several things: It aligns contractile elements (cross-bridges) in muscle for maximal force. It takes slack out of the system. It stores elastic energy in the muscle tendon complex.

Core Training Strong and balanced muscles of the trunk permit better transfer of power from one part of the body to another or to an external object. A moderate amount of core training seems essential for lower back health. More is necessary for those in physically demanding occupations, such as construction, firefighting, law enforcement, and the military.

Summary Tension multiplied by time is the stimulus for strength development How the tension is produced doesn't matter. Difference between strength and endurance training plans on cellular outcomes. Engaging in a strength plan will not adapt the body for endurance-type activities.