Anatomical data for analyzing human motion

C H A P T E R

1What Is Biomechanics? After completing this chapter, you will be able to:

Defi ne the terms biomechanics, statics, dynamics, kinematics, and kinetics, and explain the ways in which they are related.

Describe the scope of scientifi c inquiry addressed by biomechanists.

Distinguish between qualitative and quantitative approaches for analyzing human movement.

Explain how to formulate questions for qualitative analysis of human movement.

Use the 11 steps identifi ed in the chapter to solve formal problems.

O N L I N E L E A R N I N G C E N T E R R E S O U R C E S

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2 BASIC BIOMECHANICS

W hy do some golfers slice the ball? How can workers avoid develop-ing low back pain? What cues can a physical education teacher pro- vide to help students learn the underhand volleyball serve? Why do some elderly individuals tend to fall? We have all admired the fl uid, graceful movements of highly skilled performers in various sports. We have also observed the awkward fi rst steps of a young child, the slow progress of an injured person with a walking cast, and the hesitant, uneven gait of an elderly person using a cane. Virtually every activity class includes a student who seems to acquire new skills with utmost ease and a student who trips when executing a jump or misses the ball when attempting to catch, strike, or serve. What enables some individuals to execute complex movements so easily, while others appear to have diffi culty with relatively simple movement skills?

Although the answers to these questions may be rooted in physiologi- cal, psychological, or sociological issues, the problems identifi ed are all biomechanical in nature. This book will provide a foundation for identify- ing, analyzing, and solving problems related to the biomechanics of hu- man movement.

BIOMECHANICS: DEFINITION AND PERSPECTIVE

The term biomechanics combines the prefi x bio, meaning “life,” with the fi eld of mechanics, which is the study of the actions of forces. The interna- tional community of scientists adopted the term biomechanics during the early 1970s to describe the science involving the study of the mechanical aspects of living organisms (28). Within the fi elds of kinesiology and ex- ercise science, the living organism most commonly of interest is the hu- man body. The forces studied include both the internal forces produced by muscles and the external forces that act on the body.

Learning to walk is an ambitious task from a biomechanical perspective. Photo © PhotoAlto/PictureQuest.

•Courses in anatomy, physiology, mathematics, physics, and engineering provide background knowledge for biomechanists.

biomechanics application of mechanical principles in the study of living organisms

Anthropometric characteristics may predispose an athlete to success in one sport and yet be disadvantageous for participation in another. Photo courtesy of Royalty-Free/CORBIS.

CHAPTER 1: WHAT IS BIOMECHANICS? 3

Biomechanists use the tools of mechanics, the branch of physics in- volving analysis of the actions of forces, to study the anatomical and functional aspects of living organisms (Figure 1-1). Statics and dynam- ics are two major subbranches of mechanics. Statics is the study of sys- tems that are in a state of constant motion, that is, either at rest (with no motion) or moving with a constant velocity. Dynamics is the study of systems in which acceleration is present.

Kinematics and kinetics are further subdivisions of biomechanical study. What we are able to observe visually when watching a body in mo- tion is termed the kinematics of the movement. Kinematics involves the study of the size, sequencing, and timing of movement, without reference to the forces that cause or result from the motion. The kinematics of an ex- ercise or a sport skill execution is also known, more commonly, as form or technique. Whereas kinematics describes the appearance of motion, kinet- ics is the study of the forces associated with motion. Force can be thought of as a push or pull acting on a body. The study of human biomechanics may include questions such as whether the amount of force the muscles are producing is optimal for the intended purpose of the movement.

Although biomechanics is relatively young as a recognized fi eld of sci- entifi c inquiry, biomechanical considerations are of interest in several dif- ferent scientifi c disciplines and professional fi elds. Biomechanists may have academic backgrounds in zoology; orthopedic, cardiac, or sports medicine; biomedical or biomechanical engineering; physical therapy; or kinesiology, with the commonality being an interest in the biomechanical aspects of the structure and function of living things.

The biomechanics of human movement is one of the subdisciplines of kinesiology, the study of human movement (Figure 1-2). Although some biomechanists study topics such as ostrich locomotion, blood fl ow through constricted arteries, or micromapping of dental cavities, this book focuses primarily on the biomechanics of human movement from the perspective of the movement analyst.

As shown in Figure 1-3, biomechanics is also a scientifi c branch of sports medicine. Sports medicine is an umbrella term that encompasses both clinical and scientifi c aspects of exercise and sport. The American College of Sports Medicine is an example of an organization that pro- motes interaction between scientists and clinicians with interests in sports medicine–related topics.

Biomechanics

Mechanics

Function

Structure

FIGURE 1-1

Biomechanics uses the principles of mechanics for solving problems related to the structure and function of living organisms.

mechanics branch of physics that analyzes the actions of forces on particles and mechanical systems

statics branch of mechanics dealing with systems in a constant state of motion

dynamics branch of mechanics dealing with systems subject to acceleration

kinematics study of the description of motion, including considerations of space and time

kinetics study of the action of forces

kinesiology study of human movement

sports medicine clinical and scientifi c aspects of sports and exercise

4 BASIC BIOMECHANICS

What Problems Are Studied by Biomechanists?

As expected given the different scientifi c and professional fi elds repre- sented, biomechanists study questions or problems that are topically di- verse. For example, zoologists have examined the locomotion patterns of dozens of species of animals walking, running, trotting, and galloping at controlled speeds on a treadmill to determine why animals choose a par- ticular stride length and stride rate at a given speed. They have found that running actually consumes less energy than walking in small ani- mals up to the size of dogs, but running is more costly than walking for larger animals such as horses (35). One of the challenges of this type of research is determining how to persuade a cat, a dog, or a turkey to run on a treadmill (Figure 1-4).

Among humans, although the energy cost of running increases with running speed, sizable differences in energy cost between individuals become even larger as running speed increases (21). Although some

Kinesiology

Adapted Physical education

Biomechanics

Sport Philosophy

Motor Control

Sport Art

Athletic Training Exercise

Physiology

Sport Psychology

PedagogySport History

Sports Medicine

Physical Therapy Cardiac

Rehabilitation

Exercise Physiology

Athletic TrainingBiomechanics

Other Medical Specialties

Sport Psychology Orthopedics

Sport NutritionMotor Control

FIGURE 1-2

The subdisciplines of kinesiology.

FIGURE 1-3

The branches of sports medicine.

•In research, each new study, investigation, or experiment is usually designed to address a particular question or problem.

CHAPTER 1: WHAT IS BIOMECHANICS? 5

individuals appear to run more smoothly and comfortably than others, no particular biomechanical factors have been associated with either good or poor running economy (21). Differences in muscle fi ber type com- position appear to translate into differences in energy utilization during running (see Chapter 6) (22).

The U.S. National Aeronautics and Space Administration (NASA) spon- sors another multidisciplinary line of biomechanics research to promote understanding of the effects of microgravity on the human musculoskeletal system. Of concern is the fact that astronauts who have been out of the earth’s gravitational fi eld for just a few days have returned with muscle atrophy, cardiovascular and immune system changes, and reduced bone density, mineralization, and strength, especially in the lower extremities (11). The issue of bone loss, in particular, is currently a limiting factor for long-term space fl ights, with bone lost at a rate of about 1% per month from the lumbar spine and 1.5% per month from the hips (26). Both increased bone resorption and decreased calcium absorption appear to be respon- sible (see Chapter 4) (39).

Since those early days of space fl ight, biomechanists have designed and built a number of exercise devices for use in space to take the place of normal bone-maintaining activities on earth. Some of this research has focused on the design of treadmills for use in space that load the bones of the lower extremity with deformations and strain rates that are optimal for stimulating new bone formation (8, 30). Another approach involves combining voluntary muscle contraction with electrical stimulation of the muscles to maintain muscle mass and tone (44). So far, however, no ad- equate substitute has been found for weight bearing for the prevention of bone and muscle loss in space (11).

Maintaining suffi cient bone-mineral density is also a topic of concern here on earth. Osteoporosis is a condition in which bone mineral mass and strength are so severely compromised that daily activities can cause bone pain and fracturing (13). This condition is found in most elderly

FIGURE 1-4

Research on the biomechanics of animal gaits poses some interesting problems.

6 BASIC BIOMECHANICS

individuals, with earlier onset in women, and is becoming increasingly prevalent throughout the world with the increasing mean age of the pop- ulation. Approximately 40% of women experience one or more osteopo- rotic fractures after age 50, and after age 60, about 90% of all fractures in both men and women are osteoporosis-related (23, 34). The most common fracture site is the vertebrae, with the presence of one fracture indicating increased risk for future vertebral and hip fractures (15). This topic is explored in depth in Chapter 4.

Another problem area challenging biomechanists who study the el- derly is mobility impairment. Age is associated with decreased ability to balance, and older adults both sway more and fall more than young adults, although the reasons for these changes are not well understood. Falls, and particularly fall-related hip fractures, are extremely serious, common, and costly medical problems among the elderly. Each year, falls cause large percentages of the wrist fractures, head injuries, vertebral fractures, and lacerations, as well as over 90% of the hip fractures, occur- ring in the United States (37). Biomechanical research teams are investi- gating the biomechanical factors that enable individuals to avoid falling, the characteristics of safe landings from falls, the forces sustained by dif- ferent parts of the body during falls, and the ability of protective clothing

Exercise in space is critically important for preventing loss of bone mass among astronauts. Photo courtesy of NASA.

CHAPTER 1: WHAT IS BIOMECHANICS? 7

and fl oors to prevent falling injuries (37). Promising work in the develop- ment of intervention strategies has shown that the key to preventing falls may be the ability to limit trunk motion (14). Older adults can quickly learn strategies for limiting trunk motion through task-specifi c training combined with whole-body exercise.

Research by clinical biomechanists has resulted in improved gait among children with cerebral palsy, a condition involving high levels of muscle tension and spasticity. The gait of the cerebral palsy individual is characterized by excessive knee fl exion during stance. This problem is treated by surgical lengthening of the hamstring tendons to improve knee extension during stance. In some patients, however, the procedure also diminishes knee fl exion during the swing phase of gait, resulting in drag- ging of the foot. After research showed that patients with this problem exhibited signifi cant co-contraction of the rectus femoris with the ham- strings during the swing phase, orthopedists began treating the problem by surgically attaching the rectus femoris to the sartorius insertion. This creative, biomechanics research–based approach has enabled a major step toward gait normalization for children with cerebral palsy.

Research by biomedical engineers has also resulted in improved gait for children and adults with below-knee amputations. Ambulation with a prosthesis creates an added metabolic demand, which can be partic- ularly signifi cant for elderly amputees and for young active amputees who participate in sports requiring aerobic conditioning. In response to this problem, researchers have developed an array of lower-limb and foot prostheses that store and return mechanical energy during gait, thereby reducing the metabolic cost of locomotion (2). Studies have shown that the more compliant prostheses are better suited for active and fast walkers, whereas prostheses that provide a more stable base of support are gener- ally preferred for the elderly population (3). Microchip-controlled “Intel- ligent Prostheses” show promise for reducing the energy cost of walking at a range of speeds (7). Researchers are currently developing a new class of “bionic” prosthetic feet that are designed to better imitate normal gait (41).

Occupational biomechanics is a fi eld that focuses on the prevention of work-related injuries and the improvement of working conditions and worker performance. Researchers in this fi eld have learned that work- related low back pain can derive not only from the handling of heavy materials but from unnatural postures, sudden and unexpected mo- tions, and the characteristics of the individual worker (27). Sophisticated biomechanical models of the trunk are now being used in the design of materials-handling tasks in industry to enable minimizing potentially injurious stresses to the low back (4).

Biomechanists have also contributed to performance improvements in selected sports through the design of innovative equipment. One excel- lent example of this is the Klapskate, the speed skate equipped with a hinge near the toes that allows the skater to plantar fl ex at the ankle during push-off, resulting in up to 5% higher skating velocities than were obtainable with traditional skates (17). The Klapskate was designed by van Ingen Schenau and de Groot, based on study of the gliding push-off technique in speed skating by van Ingen Schenau and Baker, as well as work on the intermuscular coordination of vertical jumping by Bobbert and van Ingen Schenau (9). When the Klapskate was used for the fi rst time by competitors in the 1998 Winter Olympic Games, speed records were shattered in every event.

Numerous innovations in sport equipment and apparel have also re- sulted from fi ndings of experiments conducted in experimental cham- bers called wind tunnels that involved controlled simulation of the air

Occupational biomechanics involves study of safety factors in activities such as lifting.

Aerodynamic cycling equipment has contributed to new world records. Photo courtesy of Getty Images.

carpal tunnel syndrome overuse condition caused by compression of the median nerve in the carpal tunnel and involving numbness, tingling, and pain in the hand

8 BASIC BIOMECHANICS

Biomechanists Develop a Revolutionary New Figure Skate

What do 1996 U.S. fi gure skating champion Rudy Galindo and 1998 Olympic gold medal winner Tara Lipinski have in common besides fi gure skating success? They have both had double hip replacements, Galindo at age 32 and Lipinski at age 18.

Overuse injuries among fi gure skaters are on the rise at an alarming rate, with most involving the lower extremities and lower back (4, 12). With skaters performing more and more technically demanding programs including multirotation jumps, on-ice training time for elite skaters now typically includes over 100 jumps per day, six days per week, year after year.

Yet, unlike most modern sports equipment, the fi gure skate has undergone only very minor modifi cations since 1900. The soft-leather, calf-high boots of the nineteenth cen- tury are now made of stiffer leather to promote ankle stability and are not quite as high to allow a small amount of ankle motion. However, the basic design of the rigid boot with a screwed-on steel blade has not changed.

The problem with the traditional fi gure skate is that when a skater lands after a jump, the rigid boot severely restricts motion at the ankle, forcing the skater to land nearly fl at-footed and preventing motion at the ankle that could help attenuate the landing shock that gets translated upward through the musculoskeletal system. Not surprisingly, the incidence of overuse injuries in fi gure skating is mushrooming due to the increased emphasis on performing jumps, the increase in training time, and the continued use of outdated equipment.

To address this problem, biomechanist Jim Richards and graduate student Dustin Bruening, working at the University of Delaware’s Human Performance Lab, have de- signed and tested a new fi gure skating boot. Following the design of modern-day Alpine skiing and in-line skating boots, the new boot incorporates an articulation at the ankle that permits fl exion movement but restricts potentially injurious sideways movement.

The boot enables skaters to land toe-fi rst, with the rest of the foot hitting the ice more slowly. This extends the landing time, thereby spreading the impact force over a longer time and dramatically diminishing the peak force translated up through the body. As shown in the graph, the new boot attenuates the peak landing force on the order of 30%.

Although the new fi gure skating boot design was motivated by a desire to reduce the incidence of stress injuries in skating, it may also promote performance. The ability to

New fi gure skating boot with an articulation at the ankle designed by biomechanists at the University of Delaware.

CHAPTER 1: WHAT IS BIOMECHANICS? 9

resistance actually encountered during particular sports. Examples include the aerodynamic helmets, clothing, and cycle designs used in competitive cycling, and the ultrasmooth suits worn in other competi- tive speed-related events, such as swimming, track, skating, and skiing. Wind tunnel experiments have also been conducted to identify optimal body confi guration during events such as ski jumping (42).

Sport biomechanists have also directed efforts at improving the bio- mechanical, or technique, components of athletic performance. They have learned, for example, that factors contributing to superior performance in the long jump, high jump, and pole vault include high horizontal velocity going into takeoff and a shortened last step that facilitates continued eleva- tion of the total-body center of mass (6, 16). Study of baseball pitchers has determined that high-velocity pitchers display greater external rotation at the shoulder, more forward trunk tilt at ball release, higher-extension angular velocity at the lead knee, and greater angular velocity of the pel- vis and upper torso than lower-velocity pitchers (25, 40).

One rather dramatic example of performance improvement partially at- tributable to biomechanical analysis is the case of four-time Olympic dis- cus champion Al Oerter. Mechanical analysis of the discus throw requires

move through a larger range of motion at the ankle may well enable higher jump heights and concomitantly more rotations while the skater is in the air.

Skaters who adopt the new boot are fi nding that using it effectively requires a period of acclimatization. Those who have been skating in the traditional boot for many years tend to have reduced strength in the musculature surrounding the ankle. Improving ankle strength is likely to be necessary for optimal use of a boot that now allows ankle motion.

The new fi gure skating boot with an articulation at the ankle reduces peak impact forces during landing from a jump on the order of 30%. Graph courtesy of D. Bruening and J. Richards.

0.0 0.000 0.050 0.100 0.150 0.200 0.250

Time (sec)

Standard Peak Force (N) Articulated Peak Force (N)

Reduction (%)

1597.16 1140.27

28.61

0.300 0.350 0.400 0.450 0.500

100.0

200.0

300.0

400.0

500.0

600.0

700.0

800.0

900.0

G ro

un d

R ea

ct io

n Fo

rc e

(N )

1000.0

1100.0

1200.0

1300.0

1400.0

1500.0

1600.0

10 BASIC BIOMECHANICS

precise evaluation of the major mechanical factors affecting the fl ight of the discus. These factors include the following:

1. The speed of the discus when it is released by the thrower 2. The projection angle at which the discus is released 3. The height above the ground at which the discus is released 4. The angle of attack (the orientation of the discus relative to the pre-

vailing air current)

By using computer simulation techniques, researchers can predict the needed combination of values for these four variables that will result in a throw of maximum distance for a given athlete (18). High-speed cameras can record performances in great detail, and when the fi lm or video is analyzed, the actual projection height, velocity, and angle of attack can be compared to the computer-generated values required for optimal perfor- mance. At the age of 43, Oerter bettered his best Olympic performance by 8.2 m. Although it is diffi cult to determine the contributions of motivation and training to such an improvement, some part of Oerter’s success was a result of enhanced technique following biomechanical analysis (38). Most adjustments to skilled athletes’ techniques produce relatively modest re- sults because their performances are already characterized by above- average technique.

Some of the research produced by sport biomechanists has been done in conjunction with the Sports Medicine Division of the United States Olympic Committee (USOC). Typically, this work is done in direct cooper- ation with the national coach of the sport to ensure the practicality of re- sults. USOC-sponsored research has yielded much new information about the mechanical characteristics of elite performance in various sports. Be- cause of continuing advances in scientifi c analysis equipment, the role of sport biomechanists in contributing to performance improvements is likely to be increasingly important in the future.

The infl uence of biomechanics is also being felt in sports popular with both nonathletes and athletes, such as golf. Computerized video analyses of golf swings designed by biomechanists are commonly available at golf courses and equipment shops. The science of biomechanics can play a role in optimizing the distance and accuracy of all golf shots, including put- ting, through analysis of body angles, joint forces, and muscle activity pat- terns (19). A common technique recommendation is to maintain a single fi xed center of rotation to impart force to the ball (19).

Other concerns of sport biomechanists relate to minimizing sport in- juries through both identifying dangerous practices and designing safe equipment and apparel. In recreational runners, for example, research shows that the most serious risk factors for overuse injuries are training errors such as a sudden increase in running distance or intensity, excess cu- mulative mileage, and running on cambered surfaces (20). The complexity of safety-related issues increases when the sport is equipment-intensive. Evaluation of protective helmets involves ensuring not only that the im- pact characteristics offer reliable protection but also that the helmet does not overly restrict wearers’ peripheral vision.

An added complication is that equipment designed to protect one part of the body may actually contribute to the likelihood of injury in another part of the musculoskeletal system. Modern ski boots and bindings, while effec- tive in protecting the ankle and lower leg against injury, unfortunately con- tribute to severe bending moments at the knee when the skier loses balance. Recreational Alpine skiers consequently experience a higher incidence of anterior cruciate ligament tears than participants in any other sport (33). Injuries in snowboarding are also more frequent with rigid, as compared to

•The USOC began funding sports medicine research in 1981. Other countries began sponsoring research to boost the performance of elite athletes in the early 1970s.

•Impact testing of protective sport helmets is carried out scientifi cally in engineering laboratories.

CHAPTER 1: WHAT IS BIOMECHANICS? 11

pliable, boots, although more than half of all snowboarding injuries are to the upper extremity (24, 32).

Another challenging area of research for biomechanists in the realm of sport safety is investigation of the effi cacy of prophylactic knee braces (29). Approximately 60% of all sport injuries are to the knee (36). Research shows that knee braces can contribute 20–30% added resistance against lateral blows to the knee, with custom-fi tted braces providing the best protection (1). A possible concern, however, is that knee braces act to change the pattern of lower-extremity muscle activity during gait, with less work performed at the knee and more at the hip (10). Other docu- mented problems that appear to affect some athletes more than others and may be brace-specifi c include reduced sprinting speed and earlier on- set of fatigue (1). The research literature is almost evenly divided on the effi cacy of prophylactic knee braces in preventing knee ligament injuries in football players, with some studies showing decreases and others show- ing increases in injury incidence (31).

An area of biomechanics research with implications for both safety and performance is sport shoe design. Today sport shoes are designed both to prevent excessive loading and related injuries and to enhance performance. Because the ground or playing surface, the shoe, and the human body compose an interactive system, athletic shoes are specifi cally designed for particular sports, surfaces, and anatomical considerations. Aerobic dance shoes are constructed to cushion the metatarsal arch. Foot- ball shoes to be used on artifi cial turf are designed to minimize the risk of knee injury. Running shoes are available for training and racing on snow and ice. In fact, sport shoes today are so specifi cally designed for desig- nated activities that wearing an inappropriate shoe can contribute to the likelihood of injury.

These examples illustrate the diversity of topics addressed in biome- chanics research, including some examples of success and some areas of continuing challenge. Clearly, biomechanists are contributing to the knowledge base on the full gamut of human movement, from the gait of the physically challenged child to the technique of the elite athlete. Although varied, all of the research described is based on applications of mechanical principles in solving specifi c problems in living organisms. This book is designed to provide an introduction to many of those prin- ciples and to focus on some of the ways in which biomechanical principles may be applied in the analysis of human movement.

Why Study Biomechanics?

As is evident from the preceding section, biomechanical principles are ap- plied by scientists and professionals in a number of fi elds to problems related to human health and performance. Knowledge of basic biomechanical con- cepts is also essential for the competent physical education teacher, physical therapist, physician, coach, personal trainer, or exercise instructor.

An introductory course in biomechanics provides foundational under- standing of mechanical principles and their applications in analyzing movements of the human body. The knowledgeable human movement an- alyst should be able to answer the following types of questions related to biomechanics: Why is swimming not the best form of exercise for individuals with osteoporosis? What is the biomechanical principle behind variable- resistance exercise machines? What is the safest way to lift a heavy object? Is it possible to judge what movements are more/less economi- cal from visual observation? At what angle should a ball be thrown for maximum distance? From what distance and angle is it best to observe

12 BASIC BIOMECHANICS

a patient walk down a ramp or a volleyball player execute a serve? What strategies can an elderly person or a football lineman employ to maximize stability? Why are some individuals unable to fl oat?

Perusing the objectives at the beginning of each chapter of this book is a good way to highlight the scope of biomechanical topics to be covered at the introductory level. For those planning careers that involve visual observation and analysis of human movement, knowledge of these topics will be invaluable.

PROBLEM-SOLVING APPROACH

Scientifi c research is usually aimed at providing a solution for a particu- lar problem or answering a specifi c question. Even for the nonresearcher, however, the ability to solve problems is a practical necessity for function- ing in modern society. The use of specifi c problems is also an effective ap- proach for illustrating basic biomechanical concepts.

Quantitative versus Qualitative Problems

Analysis of human movement may be either quantitative or qualitative. Quantitative implies that numbers are involved, and qualitative refers to a description of quality without the use of numbers. After watching the performance of a standing long jump, an observer might qualitatively state, “That was a very good jump.” Another observer might quantitatively an- nounce that the same jump was 2.1 m in length. Other examples of qualita- tive and quantitative descriptors are displayed in Figures 1-5 and 1-6.

It is important to recognize that qualitative does not mean general. Qualitative descriptions may be general, but they may also be extremely detailed. It can be stated qualitatively and generally, for example, that a man is walking down the street. It might also be stated that the same man is walking very slowly, appears to be leaning to the left, and is bearing weight on his right leg for as short a time as possible. The second description is en- tirely qualitative but provides a more detailed picture of the movement.

Both qualitative and quantitative descriptions play important roles in the biomechanical analysis of human movement. Biomechanical re- searchers rely heavily on quantitative techniques in attempting to answer

quantitative involving the use of numbers

qualitative involving nonnumeric description of quality

FIGURE 1-5

Examples of qualitative and quantitative descriptors.

CHAPTER 1: WHAT IS BIOMECHANICS? 13

specifi c questions related to the mechanics of living organisms. Clinicians, coaches, and teachers of physical activities regularly employ qualitative observations of their patients, athletes, or students to formulate opinions or give advice.

Solving Qualitative Problems

Qualitative problems commonly arise during daily activities. Questions such as what clothes to wear, whether to major in botany or English, and whether to study or watch television are all problems in the sense that they are uncertainties that may require resolution. Thus, a large portion of our daily lives is devoted to the solution of problems.

Analyzing human movement, whether to identify a gait anomaly or to refi ne a technique, is essentially a process of problem solving. Whether the analysis is qualitative or quantitative, this involves identifying, then study- ing or analyzing, and fi nally answering a question or problem of interest.

To effectively analyze a movement, it is essential fi rst to formulate one or more questions regarding the movement. Depending on the specifi c purpose of the analysis, the questions to be framed may be general or spe- cifi c. General questions, for example, might include the following:

1. Is the movement being performed with adequate (or optimal) force? 2. Is the movement being performed through an appropriate range of

motion? 3. Is the sequencing of body movements appropriate (or optimal) for ex-

ecution of the skill? 4. Why does this elderly woman have a tendency to fall? 5. Why is this shot putter not getting more distance?

More specifi c questions might include these:

1. Is there excessive pronation taking place during the stance phase of gait?

2. Is release of the ball taking place at the instant of full elbow extension? 3. Does selective strengthening of the vastus medialis obliquus alleviate

mistracking of the patella for this person?

FIGURE 1-6

Quantitatively, the robot missed the coffee cup by 15 cm. Qualitatively, it malfunctioned.

Coaches rely heavily on qualitative observations of athletes’ performances in formulating advice about technique. Photo courtesy of Ken Karp for MMH.

14 BASIC BIOMECHANICS

Once one or more questions have been identifi ed, the next step in ana- lyzing a human movement is to collect data. The form of data most com- monly collected by teachers, therapists, and coaches is qualitative visual observation data. That is, the movement analyst carefully observes the movement being performed and makes either written or mental notes. To acquire the best observational data possible, it is useful to plan ahead as to the optimal distance(s) and perspective(s) from which to make the observations. These and other important considerations for qualitatively analyzing human movement are discussed in detail in Chapter 2.

Formal versus Informal Problems

When confronted with a stated problem taken from an area of mathemat- ics or science, many individuals believe they are not capable of fi nding a solution. Clearly, a stated math problem is different from a problem such as what to wear to a particular social gathering. In some ways, however, the informal type of problem is the more diffi cult one to solve. According to Wickelgren (43), a formal problem (such as a stated math problem) is characterized by three discrete components:

1. A set of given information 2. A particular goal, answer, or desired fi nding 3. A set of operations or processes that can be used to arrive at the an-

swer from the given information

In dealing with informal problems, however, individuals may fi nd the given information, the processes to be used, and even the goal itself to be unclear or not readily identifi able.

Solving Formal Quantitative Problems

Formal problems are effective vehicles for translating nebulous concepts into well-defi ned, specifi c principles that can be readily understood and applied in the analysis of human motion. People who believe themselves incapable of solving formal stated problems do not recognize that, to a large extent, problem-solving skills can be learned. Entire books on problem- solving approaches and techniques are available. However, most students are not exposed to coursework involving general strategies of the problem- solving process. A simple procedure for approaching and solving problems involves 11 sequential steps: