Stretching Anatomy-2nd Edition

Stretching Anatomy

Second Edition

Arnold G. Nelson

Jouko Kokkonen

Human Kinetics

Library of Congress Cataloging-in-Publication Data

Nelson, Arnold G., 1953-

Stretching anatomy / Arnold G. Nelson, Jouko Kokkonen. -- Second edition.

pages cm

1. Muscles--Anatomy. 2. Stretch (Physiology) I. Kokkonen, Jouko. II. Title.

QM151.N45 2014

611'.73--dc23

2013013541

ISBN-10: 1-4504-3815-6 (print)

ISBN-13: 978-1-4504-3815-5 (print)

Copyright © 2014, 2007
by Arnold G. Nelson and Jouko Kokkonen

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Contents

Introduction

Anatomy and Physiology of Stretching

Types of Stretches

Benefits of a Stretching Program

Static and Dynamic Stretches for Athletes

How to Use This Book

Chapter 1: Neck

Chapter 2: Shoulders, Back, and Chest

Chapter 3: Arms, Wrists, and Hands

Chapter 4: Lower Trunk

Chapter 5: Hips

Chapter 6: Knees and Thighs

Chapter 7: Feet and Calves

Chapter 8: Dynamic Stretches

Chapter 9: Customizing Your Stretching Program

Static and Dynamic Stretching Programs

Stretching Program to Lower Blood Glucose

Sport-Specific Stretches

Stretch Finder

About the Authors

Introduction

Flexibility is an important component of overall fitness. Unfortunately, flexibility is generally not one of the main focuses of many fitness programs. It is usually given very little attention or is neglected altogether. Although the benefits of regular exercise are well known, few people realize that flexible joints and regular stretching are also essential for optimal health and activity. For example, stretching can help people who have arthritis. To help relieve pain, especially during the early stages of this condition, people who have arthritis often keep affected joints bent and still. Although holding a joint still and bent may temporarily relieve discomfort, keeping a joint in the same position causes the muscles and ligaments to stiffen. This lack of movement can cause the muscles to shorten and become tight, leading to permanent loss of mobility and a hindering of daily activities. In addition, less movement means fewer calories burned, and any added weight puts more strain on the joints. Therefore, fitness experts urge people who have arthritis to stretch all of the major muscle groups daily, placing a gentle emphasis on joints that have decreased range of motion.

Good flexibility is known to bring positive benefits to the muscles and joints. It aids with injury prevention, helps minimize muscle soreness, and improves efficiency in all physical activities. This is especially true for people whose exercise sessions, whether a recreational game of golf or a more strenuous weekend game of basketball, are more than four days apart. Increasing flexibility can also improve quality of life and functional independence. People whose daily lifestyle consists of long sessions of inactivity such as sitting at a desk can experience a stiffening of the joints so that it is difficult to straighten out from that chronic position. Good flexibility helps prevent this by maintaining the elasticity of the muscles and providing a wider range of movements in the joints. It also provides fluidity and ease in body movements and everyday activities. A simple daily task such as bending over and tying your shoes is easier when you have good flexibility.

Stretching can also help prevent and relieve many muscle cramps, especially leg cramps that occur during the night. The causes of nighttime leg cramps are varied: too much exercise; muscle overuse; standing on a hard surface for a long time; flat feet; sitting for a long time; an awkward leg position during sleep; insufficient potassium, calcium, or other minerals; dehydration; certain medicines such as antipsychotics, birth control pills, diuretics, statins, and steroids; and diabetes or thyroid disease. Regardless of the cause, a more flexible muscle is less likely to cramp, and stretching helps to immediately reduce the cramp. Interestingly, current research shows that people who have type 2 diabetes or who are at high risk can help control blood glucose levels by doing 30 to 40 minutes of stretching. Thus, it is easy to see the benefits of making a stretching program a daily habit.

How much stretching should the average person do every day? Most people tend to overlook this important fitness routine altogether. Those who do stretch tend to perform a very brief routine that concentrates mainly on the lower-body muscle groups. In fact, it would be generous to suggest that people stretch any particular muscle group for more than 15 seconds. The total time spent in a stretching routine hardly ever exceeds 5 minutes. Even in athletics, stretching is given minor importance in the overall training program. An athlete might spend just a little more time stretching than the average person, usually because stretching is part of a warm-up routine. After the workout, however, most athletes are either too tired to do any stretching or simply do not take the time to do it. Stretching can be performed both as part of the warm-up before a workout and as part of a cool-down after, although stretching as part of a warm-up has become controversial. Stretching right before an event can have negative consequences on athletic performance. These negative consequences are most evident if the stretching exceeds 30 seconds. Therefore, a short stretch or quick loosen-up can be part of the warm-up, but stretching to induce permanent increases in flexibility should be done as part of the cool-down.

Anatomy and Physiology of Stretching

Muscles such as the biceps brachii are complex organs composed of nerves, blood vessels, tendons, fascia, and muscle cells. Nerve cells (neurons) and muscle cells are electrically charged. The resting electrical charge, or resting membrane potential, is negative and is generally around –70 millivolts. Neurons and muscle cells are activated by changing their electrical charges. Electrical signals cannot jump between cells, so neurons communicate with other neurons and with muscle cells by releasing specialized chemicals called
neurotransmitters
. Neurotransmitters work by enabling positive sodium ions to enter the cells and make the resting membrane potential more positive. Once the resting membrane potential reaches a threshold potential (generally –62 millivolts), the cell becomes excited, or active. Activated neurons release other neurotransmitters to activate other nerves, causing activated muscle cells to contract.

Besides being altered to cause excitation, the membrane potential can be altered to cause either facilitation or inhibition. Facilitation occurs when the resting membrane potential is raised slightly above normal but below the threshold potential. Facilitation increases the likelihood that any succeeding neurotransmitter releases will cause the potential to exceed the threshold. This enhances the chances of the neuron’s firing and activating the target. Inhibition occurs when the resting membrane potential is lowered below the normal potential, thereby decreasing the likelihood of reaching the threshold. Usually this prevents the neuron from activating its target.

To perform work, the muscle is subdivided into motor units. The motor unit is the basic functional unit of the muscle. A motor unit consists of one motor (muscle) neuron and all the muscle cells to which it connects, as few as 4 to more than 200. Motor units are then subdivided into individual muscle cells. A single muscle cell is sometimes referred to as a
fiber
. A muscle fiber is a bundle of rodlike structures called
myofibrils
that are surrounded by a network of tubes known as the sarcoplasmic reticulum, or SR. Myofibrils are formed by a series of repeating structures called
sarcomeres
. Sarcomeres are the basic functional contractile units of a muscle.

The three basic parts of a sarcomere are thick filaments, thin filaments, and Z-lines. A sarcomere is defined as the segment between two neighboring Z-lines. The thin filaments are attached to both sides of a Z-line and extend out from the Z-line for less than one-half of the total length of the sarcomere. The thick filaments are anchored in the middle of the sarcomere. Each end of a single thick filament is surrounded by six thin filaments in a helical array. During muscle work (concentric, eccentric, or isometric), the thick filaments control the amount and direction that the thin filaments slide over the thick filaments. In concentric work, the thin filaments slide toward each other. In eccentric work, the thick filaments try to prevent the thin filaments from sliding apart. For isometric work, the filaments do not move. All forms of work are initiated by the release of calcium ions from the SR, which occurs only when the muscle cell’s resting membrane potential exceeds the threshold potential. The muscle relaxes and quits working when the calcium ions are restored within the SR.