Part III: Basic Biomechanics: Why You Move
Chapter 11: Motion Analysis: Seeing How You Move
Motion Analysis: Seeing How You Move
In This Chapter
▶ Determining the purpose of qualitative motion analysis
▶ Taking a systematic approach to movement analysis
▶ Analyzing functional activities
Analyzing human movement is something we bet you do all the time, although you probably don’t think of it that way. If you’ve ever “people watched” while sitting at the mall and said to yourself, “Poor girl, she’s really limping,” or “Wow, that jogger is certainly bouncing down the street,” you’ve been analyzing movement.
As it turns out, an entire discipline is devoted to just this task. In this chapter, we explore a movement analysis process that makes evaluating movement easier. We also share some of the important principles and concepts to remember when you do so.
Investigating Movement: The Basics
Some of the most common reasons why people use motion analysis is to improve performance (they want to get bigger, stronger, or faster, for example) and to prevent or treat injury. To adequately analyze movement to achieve these goals, you need an approach that follows a defined process.
This process, combined with information about the actual task, enables you to discover some very helpful and valuable information.
One of the biggest pitfalls related to motion analysis lies with the practitioner who, after eyeballing a task in real time, makes judgments without having knowl- edge of the specific task or its purpose, and without really understanding the person being studied. Each person is a unique individual, with his or her own past histories of injury, levels of strength, and previous training.
236 Part III: Basic Biomechanics: Why You Move the Way You Do
Choosing an approach
Motion analysis typically takes one of two forms: either quantitative or qualitative. Occasionally, a mixture of the two is used.
Each type of analysis requires the examiner to have a sufficient level of understanding of the task at hand and the intended outcomes of the perfor- mance. And each is beneficial to motion analysis efforts and possesses its own benefits and drawbacks, which we explain in the next sections.
Qualitative analysis
A qualitative analysis offers general motion analysis assessment and feedback pertaining to the movement. A pitching coach, for example, may notice that one of his athletes is really leaning to the side during the pitch. The coach may ask the athlete to straighten up and direct his body toward home plate when throwing and to avoid leaning so much. This type of feedback is considered qualitative.
Qualitative assessment is the most common type of assessment for these reasons:
✓ It doesn’t require high-tech instruments. A qualitative analysis can be made simply by watching the movement, either in real time or on some type of video device for replay.
✓ It doesn’t require a particularly high level of skill. As long as the examiner knows how the body can move, knows how it should move optimally to perform the task, and can pick up the key positions, he or she can complete the analysis.
In most cases — when a quick look is needed — a qualitative assessment is appropriate. Typically, this is going to be the only way a Little League coaches and physical education teachers may be able to examine their athletes or students. Whether watching the movement in real time or watching a replay, people can carry out qualitative assessments pretty easily and quickly.
Quantitative analysis
Quantitative analysis involves using actual measurement to gauge perfor- mance. If, instead of providing general assessment and guidance, the pitching coach records the motion with a video camera, uses analysis software in his evaluation of the movement, and then says to the pitcher something like,
“You’re leaning 18 degrees when you release the ball. You need to straighten up so that you don’t lean more than 5 degrees,” the coach is using quantita- tive analysis. In this case, the specific measurements that were made of the motion inform the coach’s recommendations.
237
Chapter 11: Motion Analysis: Seeing How You Move
When the clinician needs more information about the amount of force, the velocity, or the angles of a movement — information that a qualitative analysis just can’t provide — then a quantitative analysis is the better option.
Knowing types of tasks and feedback mechanisms
Motion analysis can be overwhelming if you don’t really know how to go about it and don’t know what to look at. If you’re a novice, you may find yourself staring awkwardly at your subject, not really knowing where to begin. Unless you have an established process that includes knowledge of the person completing the task, the components of the movement being evaluated, and an understanding of feedback mechanisms, your analysis isn’t likely to provide much useful information.
In the following sections, we explain what you need to know about the person you’re evaluating and how understanding the different types of tasks (simple and complex) and feedback mechanisms (open and closed) is vital to making a sound evaluation and providing useful feedback. Head to the later section
“Breaking Down an Analysis Model” for a process you can follow when the time comes to put your knowledge to work.
Comparing simple and complex tasks
Not all movements have the same difficulty or require similar amounts of preparation to execute. Simple movements require very little or no thought, and they aren’t dependent on another body part completing its movement first. A good example of a simple task is picking up the phone.
Complex tasks, on the other hand, require thought and regular practice.
They’re made up of several individual components that must be completed in a particular way to produce a successful end result. An example of a complex task is pitching; it involves a coordinated effort between the legs, torso, and upper extremities. Each activity required for a successful pitch depends on another part of the body doing its job. Consider this sequence of movements:
1. The pitcher pushes off his back foot to move his body forward.
2. His hips begin to twist to facilitate the slinglike motion at the root of throwing.
3. While his body twists from the hips up through the torso (core), he moves the ball forward and hurls it at the target.
If any flaws occur within the chain of activity, the pitcher’s performance and potentially his health may be in jeopardy.
238 Part III: Basic Biomechanics: Why You Move the Way You Do
Paying attention to open- versus closed-feedback mechanisms
Some tasks are difficult to alter while they are being performed; others are easily changed. The type of information that the body has to process and the way in which it processes that information (its feedback mechanism) determines whether an activity can be changed midcourse. There are two types of feedback mechanisms:
✓ Open-feedback mechanism: A task that has an open-feedback mecha- nism (or open task) can be changed in real time. During this type of movement, the body collects information and then alters the move- ment to maximize its success in that particular situation. For example, if you’re going up for a jump shot and someone makes contact with you, you are able to change how you shoot the ball in midair.
✓ Closed-feedback mechanism: A closed-feedback mechanism task (or closed task) can’t be altered after it’s started. Closed tasks are those that, once turned on, can’t be turned off. A free throw is a good example.
The only way to be more successful with free throw shooting is to practice it over and over and over again.
Tommy John
Surgery to repair an injury to the ulnar collateral ligament (UCL), the ligament in the elbow, has been referred to as tommy john surgery since Dr. Frank Jobe first performed it on Los Angeles Dodgers pitcher Tommy John in 1974.
In this surgery, which was the first of its kind to attempt to combat what had previously been considered a career-ending injury, Dr. Jobe weaved a muscle tendon through the elbow joint to mimic the UCL. The idea was to stabilize the joint enough to allow Tommy to throw again.
It worked. Tommy returned to the Dodgers and resumed pitching at a fairly high level. Since that first surgery, tommy john surgery and pro- cedures like it have saved the careers of oodles of professional and amateur baseball pitchers.
Although many factors contribute to this injury, none is more harmful than poor biomechanics.
When you throw with your limb in less-than-ideal
positions, the soft tissues that typically support the joint break down and eventually fail or tear.
Unfortunately, this injury that was once seen only in professional athletes now plagues many young players. The change is attributed to these main reasons:
✓ Many coaches don’t understand what good throwing mechanics are. And if they don’t know, they aren’t able to intervene when a young athlete needs it.
✓ Kids who play on multiple teams and in multiple leagues are asked to throw all year round and never get a break. This constant use gives them no time to recover and heal.
So for all of you out there who think your 10-year-old is going to be the next Major League Cy Young award winner, how about giving the kid a break so that he actually has a chance to be?
239
Chapter 11: Motion Analysis: Seeing How You Move
Breaking Down an Analysis Model
To make analyzing movement easier and more efficient, you use a defined analysis model. A typical model for analysis involves knowing the nature and objective of the movement, observing and evaluating the movement, and pro- viding recommendations based on the performance outcomes. We outline the different parts of the analysis mode in this section.
The outcomes vary extensively and can include information to help achieve different goals, like improving performance or avoiding injury. They can also focus on the whole task (how to better jump for maximum distance, for exam- ple) or specific components of a given task (informing a pitcher, for example, that he may be experiencing elbow pain during a pitch because he drops his arm slot when throwing).
Gaining background knowledge
As a basis for the beginning of the movement analysis, the examiner (coach, clinician, or personal trainer) must have some background knowledge about the task to be completed. Understanding what the performer is trying to accomplish and having an understanding of the components needed to be successful are essential to the analysis. Background knowledge, explained in the following sections, helps you to identify the key elements of the
movement that need focus.
How to perform the task
You need to know the mechanics of the movement, its purpose, and the most efficient and safest ways to go about it. This knowledge makes you a more effective assessor.
Although having performed the task yourself can sometimes be helpful, it’s not essential. Some of the best coaches weren’t the greatest or most success- ful athletes; instead, their study of the game and its elements enables them to be successful. If you haven’t personally performed the task you’re evaluating, make sure you perform sufficient research into the mechanics and purpose of the task.
Many folks that analyze motion or provide coaching do so without considering how and what information they are basing their advice on. A clue that you’re dealing with one of these people is someone who says, “I know good mechan- ics when I see them” and then, when asked to define good mechanics, isn’t able to do so.
240 Part III: Basic Biomechanics: Why You Move the Way You Do The objective of the movement and each of its components
The objective of a movement may be singular and relatively simple — performing a dumbbell curl, for example, which simply requires bending the elbow and repeating. Or the movement can seem simple, like getting the batter out, but is actually quite complex. Consider the individual components of a pitch:
✓ How the pitcher stands on the rubber as he prepares to throw: The stance provides the foundation for what’s to come. Good balance and a controlled windup allow for a successful throwing motion.
✓ How the pitcher moves his torso, hips, legs, and arms as he leads up to releasing the ball: These motions generate the force leading up to his letting go of the ball.
✓ How the pitcher moves his torso, hips, legs, and arms during the pitch itself: These movements help dictate where the ball is going and what kind of movement (curve, slider, and so on) it may have.
✓ How the pitcher slows everything down after the pitch: At this point, the muscles have to stop the arm. If the pitcher has his body in the right position, some of the pressure is taken off of the shoulder muscles.
To accurately assess a task and ultimately provide feedback for improvement, you must understand the end goal and the individual components that make up that task.
The specific attributes of the performer
You must consider the level of skill, strength, range of motion, age, gender, and fitness level of the person you’re evaluating. Each of these characteris- tics not only has a significant impact on how a particular task is executed, but it also determines whether the athlete is actually even able to perform the desired activity. For example, someone who lacks good balance isn’t ready to be thrown up on the balance beam to do a routine. Instead, the athlete needs to be coached on specific techniques aimed at improving balance, like having him practice balancing in various positions. Such tasks enhance body awareness and allow the athlete to be more efficient and to avoid crazy movements that distract from the intended purpose.
Unfortunately, folks are too often put in situations that only lead to failure or injury. When I (Brian) see patients for elbow or shoulder pain, I invariably find out that they don’t have the core or back strength needed to safely complete the task — like throwing a shot put — repetitively. By taking a systematic approach to preparing a person for a particular activity — helping the athlete develop the necessary strength, dexterity, or agility, for example — you can often avoid a bad situation.
241
Chapter 11: Motion Analysis: Seeing How You Move
Be sure to ask what the athlete’s individual goals are. To improve perfor- mance? Avoid injury? Reduce existing pain or rehabilitate after an injury? The evaluation you perform for an athlete with performance-related goals is very different from the evaluation you perform for one who wants to reduce her pain. For the athlete recovering from an injury, you not only examine the actual movement but also the training regimen and number of rest days, whereas for the athlete just wanting to get more movement on her rise ball, you focus on the mechanics of the movement to determine whether an adjustment needs to be made.
Observing the subject in action
Obviously, you can’t make an assessment of a movement, let alone provide feedback, without seeing the person perform the task. In this section, we tell you how to make this observation and what to look for during each phase of the movement. Depending on what you’re looking for, you may use a power- and-return model, a three-phase model, or a model that breaks the move- ments down even more. The following sections go into more detail on the power-and-return and three-phase models, ones that you’ll use most often.
Three-phase model
To make sense of what you see, you need to break the movement up into vari- ous segments, or phases. All complex movements require preparation, execu- tion, and follow-through components, and each of these phases has a series of movements that must occur in order for the next phase to follow and/or be successful. When you break a movement into these components, you’re using the three-phase model:
✓ Preparation phase: Before each movement or task, preparatory work needs to be done. (For the purposes of this discussion, the preparation that we’re talking about is the actual activity, not previous training and that sort of thing.) Getting into a position that facilitates the impending movement is the key to this phase. Proper preparation provides a firm foundation on which the athlete can perform the task competently and safely. To prepare for a standing long jump, for example, you squat down by bending at the knees, hips, and ankles — a position that maximizes the muscular force output (refer to Chapter 10 for information about the length-tension relationship). This stance helps you push off in a way that lets you jump as far as you can.
Other important considerations include timing and positioning on the court, field, or track. For example, the angle at which you release the javelin is also critical to successfully executing the task. Although it may not be directly related to the task (jumping) itself, it’s closely related to the success or failure of the event.
242 Part III: Basic Biomechanics: Why You Move the Way You Do
✓ Execution phase: During this phase, the athlete’s body executes the movement. He propels the object or jumps up and completes that triple axle on the ice. The appropriate timing, strength, and flexibility are required to maximize his performance and avoid injury.
✓ Follow-through phase: During this phase, the athlete slows down and returns to a normal (starting) position. The follow-through often requires deceleration of the limbs and continuation of the momentum as the body transitions to another task. For example, when you kick a soccer ball, your leg doesn’t just stop after you strike the ball. Instead, it continues to move forward as your body follows and transitions to a step, typically followed by running.
Power-and-return model
Some professionals use a power-and-return model (also called the two-phase model ). This model is broken down into . . . you guessed it . . . the power and the return phases. The power phase includes the execution of the task, and the return phase encompasses the preparatory phase. (Note: Despite the name implying that the power phase happens before the return phase, remember that it does not.)
This model typically doesn’t offer insight into the follow-through of the task as the three-phase model does. If your purpose is to evaluate the outcomes of the task rather than the intricacies that make it up, the power-and-return model may be sufficient; however, if your goal is to look deeply into the task, a three-phase approach is more appropriate.
A step-by-step guide to observing movement
Follow this process when observing the movement (remember, what you look for depends on why you are doing the evaluation or what the objective of the performance is):
1. Break the activity up into phases with clear beginnings and endings, if possible.
Remember, most activities are complex in nature; they consist of many movements that need to be sequenced in a particular way. Identify the different phases and break the activity into either two, three, or, if needed, more phases.
Looking deeper into the movement, most examiners also break up each individual phase and define what should happen within each. For instance, the gait cycle of walking consists broadly of the swing and stance phases. However, many biomechanists may break those phases up even further to include pre-swing, heel strike, weight acceptance, push off, and so on. In this case, more detailed assessment occurs, but this strategy isn’t typical for most folks or tasks.