## Inertia Principle

Newton's first law of motion, or the Law of Inertia, describes the resistance of all objects to a change in their state of linear motion. In linear motion, the measure of inertia is an object's mass. Application of Newton's first law in biomechanics is termed the Inertia Principle. This section will discuss how teachers, coaches, and therapists adjust movement inertia to accommodate the task. Our focus will be on the linear inertia (mass) of movement, so the inertial resistance to rotation will...

## Qualitative Analysis Of Squat Technique

One of the most common and important exercises in athletic conditioning is the parallel squat. The squat is a functional exercise used for a wide variety of sports and other fitness objectives. The squat is usually performed as a free-weight exercise, making movement technique critical to overloading the target muscle groups and minimizing the risk of injury. Exacting technique in free-weight exercises is necessary because small variations allow other muscles to contribute to the lift,...

Strengthening muscle. Exercise and Sport Sciences Reviews, 9, 1-73. Baechle, T. R., & Earle, R. W. (Eds.) (2000). Essentials of strength training and conditioning (2nd ed.). Champaign, IL Human Kinetics. Bartlett, R. M., & Best, R. J. (1988). The biomechanics of javelin throwing A review. Journal of Sports Sciences, 6, 1-38. Garhammer, J. (1989). Weight lifting and training. In C. Vaughan (Ed.), Biomechanics of sport (pp. 169-211). Boca Raton, FL CRC Press. Knudson, D.,...

## Discussion Questions

The squat and various leg-press exercise stations are often used interchangeably. What biomechanical principles are more important in the squat than in the leg press, and how would you educate lifters who think that the exercises do the same thing 2. An athlete back in the weight room after initial rehabilitation from an injury is apprehensive about resuming their conditioning program. What biomechanical principles can be modified in adapting exercises for this athlete Suggest specific...

## Muscle Actions

Muscle forces are the main internal motors and brakes for human movement. While gravity and other external forces can be used to help us move, it is the torques created by skeletal muscles that are coordinat ed with the torques from external forces to obtain the human motion of interest. While some biomechanists are interested in the forces and motions created by smooth (visceral) or cardiac (heart) muscle, this text will focus on the actions of skeletal muscle that create human movement. The...

## Angular Motion

Angular kinematics is the description of angular motion. Angular kinematics is particularly appropriate for the study of human movement because the motion of most human joints can be described using one, two, or three rotations. Angular kinematics should also be easy for biomechanics students because for every linear kinematic variable there is a corresponding angular kinematic variable. It will even be easy to distinguish angular from linear kinematics because the adjective angular or a Greek...

## Qualitative Analysis Of Conditioning

Junior high and high school coaches often are primarily responsible for developing conditioning programs for their athletes. Coaches must carefully monitor the exercise technique of their athletes to maximize conditioning effects and reduce risk of injury. Suppose you are a junior high basketball coach who has his players perform passing drills with a small medicine ball. The technique points and biomechanical principles you are interested in are listed in Table 10.3. One of your players shows...

## Injury Risk

Imagine you are a strength coach at a junior college. You closely watch many of the young men in your preseason conditioning program because they have had little serious weight training in their high schools, and others may be pushing themselves too hard to meet team strength standards to qualify for competition. Suppose you see a player performing the bench press using Figure 11.4. The concentric phase of a bench press from an athlete struggling to make a weight goal. Figure 11.4. The...

## Fluid Forces

For the purposes of this chapter, the major fluid forces that affect human motion are classified according to an object's position or velocity within a fluid. When an object is placed in a fluid there is a resultant upward force or supporting fluid force called buoyancy. The fluid force related to how the fluid flows past the object is resolved into right-angle components called lift and drag. In most movement, people have considerable control over factors that affect these forces. Let's see...

## Info

One of the most important athletic abilities in many sports is speed. Coaches often quip that luck follows speed because a fast athlete can arrive in a crucial situation before their opponent. Coaches that often have a good understanding of speed are in cross-country and track.The careful timing of various intervals of a race, commonly referred to as pace, can be easily converted average speeds over that interval. Pace (time to run a specific distance) can be a good kinematic variable to know,...

## Injury Prevention

This chapter opened with the scenario of one of the most common injuries in sports, a non-contact sprain of the ACL. The large numbers of injuries to young female athletes has resulted in considerable research on how these injuries occur in landing, jumping, and cutting. Many biomechanical factors have been hypothesized to be related to increased risk of ACL injuries in sport peak vertical ground reaction force, knee flexion angle at landing, hamstring strength, and balance. A large prospective...

## Qualitative Analysis Of Catching

As a volunteer youth football coach you are working with your receivers on catching passes. Many young players pick up bad habits from playing neighborhood pick-up football games or watching the pros get by with talent rather than optimal technique. The technique points and cues you typically use are listed in Table 10.5. Notice how the critical features are more advanced and specialized than the catching technique points in chapter 9 (e.g., Table 9.4). Which biomechanical principles are...

## Forcetime Principle

The applied manifestation of Newton's Second Law of Motion as the Impulse-Momentum Relationship is the Force-Time Principle. If a person can apply force over a longer period of time (large impulse), they will be able to achieve a greater speed (change in momentum) than if they used similar forces in a shorter time interval. Unfortunately, in many human movements there is not an unlimited amount of time to apply forces, and there are several muscle mechanical characteristics that complicate...

## Supination NeutralPronation

Frontal plane view of rear-foot motion in the first half of the stance phase of running. The foot lands in a supinated position. The motion of the foot and ankle to accommodate to the surface and absorb shock is called pronation. journal space but places a burden on the kinesiology professional to be knowledgeable about variations in descriptive terminology. The anatomical structure and microstructure of skeletal muscle has considerable functional importance. We will see later that...

## Three Mechanical Characteristics Of Muscle

Previously we discussed the passive tension in an MTU as it is passively stretched. Now it is time to examine the tensile forces the MTU experiences in the wide variety actions, lengths, and other active conditions encountered in movement. The force potential of an MTU varies and can be described by three mechanical characteristics. These characteristics deal with the variations in muscle force because of differences in velocity, length, and the time relative to activation. The Force-Velocity...

## Linear Motion

Motion is change in position with respect to some frame of reference. In mathematical terms, linear motion is simple to define final position minus initial position. The simplest linear motion variable is a scalar called distance (l). The use of the symbol l may be easy to remember if you associate it with the length an object travels irrespec tive of direction. Typical units of distance are meters and feet. Imagine an outdoor adventurer leaves base camp and climbs for 4 hours through rough...

## Qualitative Analysis Of Drop Jumps

Plyometrics are common exercises for improving speed and muscular power movements in athletes. Plyometric exercises use weights, medicine balls, and falls to exaggerate stretch-shortening-cycle muscle actions. Considerable research has focused on drop jumps as a lower-body plyometric exercise for improving jumping ability (Bobbert, 1990). Recent research has shown that drop jump exercise programs can increase bone density in children (Fuchs, Bauer, & Snow, 2001). Qualitative analysis of drop...

## Rangeofmotion Principle

One area where anatomical description is quite effective is in the area of the range of If muscles create movement in complex synergies that are adaptable, should kinesiology professionals abandon the common practice of naming muscle groups according to anatomical function (quads knee extensors or calf ankle plantar flexors ) Such an extreme reaction to the complexity of biomechanics is not necessary. This common terminology is likely appropriate for prescribing general strength and...

## Fundamentals of Biomechanics and Qualitative Analysis

In Chapter 1 we found that biomechanics provides tools that are needed to analyze human motion, improve performance, and reduce the risk of injury. In order to facilitate the use of these biomechanical tools, this text will emphasize the qualitative understanding of mechanical concepts. Many chapters, however, will include some quantitative examples using the algebraic definitions of the mechanical variables being discussed. Mathematical formulas are a precise language and are most helpful in...

## Segmental Interaction Principle

Human movement can be performed in a wide variety of ways because of the many kinematic degrees of freedom our linked segments provide. In chapter 5 we saw that coordination of these kinematic chains ranges along a continuum from simultaneous to sequential. Kinetics provides several ways in which to examine the potential causes of these coordination patterns. The two expressions of Newton's second law and the work-energy relationship have been employed in the study of the coordination of...

## Qualitative Analysis Of The Basketball Free Throw

The previous qualitative analysis examples involved movements that must be matched to unpredictable environmental conditions. Motor learning classifies these movements as open skills, while skills with very stable conditions are called closed skills. When physical educators teach and analyze closed motor skills, they can be confident that performance is more strongly dependent on stereotypical technique rather than a variety of effective techniques. The standardized conditions of the free throw...

## Laws Of Kinetics

Linear kinetics provides precise ways to document the causes of the linear motion of all objects. The specific laws and mechanical variables a biomechanist will choose to use in analyzing the causes of linear motion often depends on the nature of the movement. When instantaneous effects are of interest, Newton's Laws of Motion are most relevant. When studying movements over intervals of time is of interest, the Impulse-Momentum Relationship is usually used. The third approach to studying the...

## Coordination Continuum Principle

Many kinesiology professionals are interested in the coordination of movement. Coordination is commonly defined as the sequence and timing of body actions used in a movement. Unfortunately there is no universally agreed-upon definition or way to study coordination in the kinesiology literature. A wide variety of approaches has been proposed to describe the coordination of movement. Some approaches focus on the kinematics of the joint or segmental actions Hudson, 1986 Kreighbaum amp Bartels,...

## Center Of Gravity

A natural application of angular kinetics and anthropometrics is the determination of the center of gravity of the body. The center of gravity is the location in space where the weight gravitational force of an object can be considered to act. The center of small rigid objects pencil, pen, bat can be easily found by trying to balance the object on your finger. The point where the object balances is in fact the center of gravity, which is the theoretical point in space where you could replace...

## Optimal Projection Principle

For most sports and human movements involving projectiles, there is a range of angles that results in best performance. The Optimal Projection Principle refers to the angle s that an object is projected to achieve a particular goal. This section will outline some general rules for optimal projections that can be easily applied by coaches and teachers. These optimal angles are rules of thumb that are consistent with the biomechanical research on projectiles. Finding true optimal angles of...

## Principle Of Balance

We have seen than angular kinetics provides mathematical tools for understanding rotation, center of gravity, and rotational equilibrium. The movement concept of balance is closely related to these angular kinetic variables. Balance is a person's ability to control their body position relative to some base of support Figure 7.13 . This ability is needed in both static equilibrium conditions e.g., handstand on a balance beam and during dynamic movement e.g., shifting the center of gravity from...

## I

Orthopedic and pediatric medicine often calls the lower extremity deviation in a genu knee valgus because the distal segment lower leg deviates laterally from the midline of the body. Normal leg orientation in the frontal plane is illustrated in b . The use of valgus and varus terminology is often inconsistent in the literature and should be clearly defined when used Houston amp Swischuk, 1980 . see that this little problem of anatomical description is very similar to the multiple...

## Qualitative And Quantitative Analysis Of Vectors

Before moving on to the next kinetic approach to studying the causes of movement, it is a good time to review the special mathematics required to handle vector quantities like force and acceleration. The linear kinetics of a biomechanical issue called muscle angle of pull will be explored in this section. While a qualitative understanding of adding force vectors is enough for most kinesiology professionals, quantifying forces provides a deeper level of explanation and understanding of the...

## Neuromuscular Control

The mechanical response of muscles also strongly depends on how the muscles are activated. The neuromuscular control of movement is an active area of study where biomechanical research methods have been particularly useful. This section will summarize the important structures and their functions in the activation of muscles to regulate muscle forces and movement. The Functional Unit of Control Motor Units The coordination and regulation of movement is of considerable interest to many scholars....

## The Limitations Of Functional Anatomical Analysis

Anatomy classifies muscles into functional groups flexors extensors, abductors adductors, etc. based on hypothesized actions. These muscle groups are useful general classifications and are commonly used in fitness education, weight training, and rehabilitation. These hypothesized muscle actions in movements and exercises are used to judge the relevance of various exercise training or rehabilitation programs. This section will show that such qualitative estimations of muscle actions are often...

## What Is Biomechanics

Biomechanics has been defined as the study of the movement of living things using the science of mechanics Hatze, 1974 . Mechanics is a branch of physics that is concerned with the description of motion and how forces create motion. Forces acting on living things can create motion, be a healthy stimulus for growth and development, or overload tissues, causing injury. Biomechanics provides conceptual and mathematical tools that are necessary for understanding how living things move and how...

## Forcemotion Principle

Another way to modify human movement is to change the application of forces. The Force-Motion Principle states that it takes unbalanced forces and the subsequent torques they induce to create or modify our motion. To know what size and direction of force to change, recall that a free-body diagram of the biomechanical system is usually employed. A major limitation of functional anatomical analysis was the limited nature of the forces and structures being considered. We are not in a position to...

## Review Of Key Anatomical Concepts

This section reviews several key concepts from human anatomy. A course in gross anatomy macroscopic structures is a typi cal prerequisite for the introductory biomechanics course. This section does not review all the bones, muscle, joints, and terms. Students and kinesiology professionals must continuously review and refresh their knowledge of anatomy. Anatomy describes the human body relative to the anatomical position. The anatomical position is approximated in Figure 3.1. The three spatial...

## Qualitative Analysis Human Movement Diagram

A free-body diagram of a person quietly standing. The major vertical forces acting on the person gravity and ground reaction force are illustrated, while horizontal forces are small enough to ignore. Figure 2.6. A free-body diagram of a person quietly standing. The major vertical forces acting on the person gravity and ground reaction force are illustrated, while horizontal forces are small enough to ignore. body is our first example of what in mechanics is called a free-body...

## Nine Fundamentals Of Biomechanics

Biomechanists measure all kinds of linear and angular mechanical variables to document and find the causes of human motion. While these variables and studies are extremely interesting to biomechanists, some kinesiology students and professionals may not find them quite so inherently stimulating. Most kinesiology professionals want to know the basic rules of biomechanics that they can apply in their jobs. This section proposes nine such principles of biome-chanics and demonstrates how they...