In case you haven’t noticed, the make-up of group fitness classes is changing. There’s been a progressive shift from working exclusively with the fit and able-bodied to instead ministering to the sedentary, overweight or elderly and to those with medical concerns. This shift challenges instructors to find new ways to design and teach fitness in a group setting. In classes full of clients with different needs and abilities, one way to start is by integrating the concepts of biomechanics.

Defining Biomechanics

Biomechanics is the application of engineering principles to biological systems. This discipline of study allows us to think about and see movement strictly in terms of its mechanics. To visualize biomechanics in action, think about a stick figure whose “sticks” rotate around a circular axis. For our purposes, the sticks are the bones, the axes of rotation are the joints and the spinal cord is the support structure for the stick figure.

When we think about integrating biomechanics into group classes, the best approach is to determine which of its concepts are at play. In other words, which biomechanics concepts are the most relevant, the easiest to apply, and universal to all types of classes? In the design of any group fitness class, these are the concepts that need to be considered:

  • force
  • spine and joint positions
  • discrete movement
  • degrees of freedom
  • progression
  • speed/accuracy trade-off


Force is the concept used to define the interaction of an object with its surroundings. Force produces a change in an object’s state of rest or motion. A force starts, stops or changes the direction of a movement. Another way to look at this is that force produces all movements associated with exercise. It is how force is used during a movement that determines the safety and effectiveness of that movement.

During exercise, fitness professionals need to be concerned with two sources of force: the internal muscle forces that produce movement, and the external environmental forces that act on the body during movement. The internal forces that cause a movement are the forces generated at the muscles and joints. The external forces act on the body from the outside. Examples of external forces that affect participants during exercise include hand weights, balls, weighted bars, the floor, a step or even an instructor. An instructor generates forces when assisting participants during stretching or strength training, for example, or when using body weight to provide resistance during a hip abductor exercise.

In group settings, instructors should aim to minimize forces acting on the spine and joints; doing so will decrease the risk of injury while maximizing the muscle forces and thereby increasing the benefits of exercise.

Using correct exercise mechanics is one way to control these forces at play. The application of the next two concepts—spine and joint position and discrete movement—go a long way toward helping clients to achieve correct exercise mechanics and to control force during exercise.

Spine and Joint Position

In biomechanics, exercise mechanics are defined by the position of the spine and joints. Because the spine is our support structure, its position influences the position of the entire body. In the same way that a concrete building cannot be erected on a crooked frame, the human body cannot work properly if the spine is misaligned or incorrectly positioned.

The position of the joints relative to the spine and to each other determines the position of the bones and the muscles. Therefore, spine and joint positions during an exercise determine the safety and effectiveness of that exercise.

In the group setting, the focus of exercise mechanics should be on the position of the spine and joints. In practical terms, that means group instructors must know the desired position of the spine and joints during a certain exercise and then focus the instruction and execution of that exercise on those positions.

Discrete Movement

Biomechanics professionals use the concept of discrete movement to define exercises. A discrete movement has definable start, middle and end positions. (The end position is always the start position.) A good example of a discrete movement is a biceps curl.

A discrete movement is the opposite of a continuous movement, which does not have definable start, middle and end positions. Examples of continuous movements are jogging and indoor cycling.

In the group setting, the application of discrete movement is particularly helpful during the strength training and flexibility components of class. However, discrete movement can also be seen during certain kickboxing exercises and step patterns. Group fitness instructors can use the concept of discrete movement to define the desired spine and joint positions for an exercise, from its start position throughout its full range of motion (ROM), thereby improving the mechanics—and the safety and effectiveness—of the exercise.

Degrees of Freedom

The concept of degrees of freedom states that an exercise increases in complexity and difficulty as the number of dimensions needed to control the movement increases. Additionally, it is more likely that a client will use unsafe and ineffective exercise mechanics when the number of dimensions involved in that exercise increases.

So what are the dimensions of an exercise, exactly? They include the number of joints and muscles involved; any balance requirements; weight shifting; and changes in plane of movement or direction. An example of an exercise in which different planes of movement are used is a forward lunge that is followed by a side lunge. Changes in direction are common in cardiovascular fitness classes in which participants are asked to walk or jog in one direction, turn quickly and proceed in the opposite direction.

As a rule, exercises with fewer dimensions are easier for group instructors to teach and for participants to execute correctly. By way of example, consider two common quadriceps exercises: the squat and the walking lunge. Which one is easier to teach and to execute? The answer is the squat, because the walking lunge involves more dimensions. The squat involves only two dimensions (the number of muscles/joints involved and a single plane of movement), whereas the walking lunge has four dimensions (the number of muscles and joints involved, a single plane of motion, the weight shifting for the forward-moving exercise and the balance needed to shift that weight).


Progression is the concept used to define the logical sequencing of movements, at either a joint or a muscle group. Think of progression as the building blocks of all movements. An example of progression would be having your class start an abdominal crunch with the hands behind the head, advancing that movement by having participants extend the arms above the head and, finally, adding a single leg lift to the crunch. All three versions of this exercise use the same base movement (crunch), which then gives participants the option of either keeping the pattern and advancing to the next move or staying with the original, less complicated version.

Speed/Accuracy Trade-Off

The final concept is the speed/accuracy trade-off, which states that the faster a movement is, the less likely it is to be performed accurately. During any exercise, the accuracy of the movement is defined by how well it works the target muscle while allowing the participant to maintain safe exercise mechanics.

The speed/accuracy trade-off is a universal problem in group fitness classes because exercises are being performed too quickly, compromising the mechanics of the movement. When an exercise is done too fast, participants bounce or swing through it or can only partially execute the move. Poor exercise mechanics increase the total forces acting on the spine and joints, with minimal benefit to the muscles.

The problem of speed is not due entirely to instructor error. Many group participants themselves misguidedly believe that faster equals stronger. Some veteran participants want pulse-pounding music at a frenetic pace, and they push for it. Moving quickly through their routines makes them think they are working hard and getting results. However, the opposite is true. Exercises executed slowly using the correct mechanics work a muscle harder and yield greater results. For example, performing a stability ball crunch too quickly puts participants at risk for using their own body weight as gravity instead of using their abdominal muscles to perform the movement correctly.

So what should a group instructor do when faced with participants who push for more speed? One way to deal with this problem is to integrate the concepts of force control, spine and joint position, discrete movement, degrees of freedom and progression into all exercises taught in a group setting. This practice will allow you to decrease exercise speed and minimize the risk of injury while still giving your participants the results they want.

Another challenge presented by the speed dilemma is the variability of your participants in a group setting. Because every human body has minor differences in architecture and movement patterns, group instructors must monitor and correct the mechanics for many people at one time under quickly changing movement conditions. The best way to handle this is to be selective about the exercises you teach in a group setting and to ask participants for their feedback after class.

From Concepts to Real Classes

Use these basic tips whenever you are designing a new group fitness class or revamping your existing programs.

  • Begin each class with key postures called preparatory postures, which ready the body for upcoming movements. For example, if a squat is used in class, warm up the participants in the hip, knee and foot position to ready them for that move.
  • Include warm-up exercises that prime the joints and muscles for all upcoming forces. For instance, start off with shoulder shrugs or rolls if you will later be performing lateral shoulder raises.
  • Incorporate warm-up movements that prepare participants for the mechanics of upcoming exercises. If dumbbell squats are planned for class, use limited-ROM, no-load squats during the warm-up.
  • Use discrete movements with definable start, middle and end positions. For example, teach your participants the three key positions of a move such as a biceps curl.
  • Use the peak contraction principle. A peak contraction is a muscle contraction at the middle position of an exercise. Stopping an exercise at the middle position helps participants execute a discrete movement.
  • Treat each repetition as an independent event. Stop a repetition at the end position so that participants cannot bounce or swing into another repetition prior to finishing the preceding one.
  • Incorporate pulse counts to prevent boredom during repetitive movements. This will allow you to use the same mechanics but also to vary the exercise without increasing the speed.
  • During the strength or flexibility component of class, use only background music, to shift the focus from doing an exercise at the speed of the music to concentrating on mechanics instead.
  • When teaching, do not face the class. A better practice is to stand in front of the class with your back to participants so they can more easily mimic your moves.
  • When assisting class members during an exercise, do not place your hands on their joints or push down directly on any part of their bodies.
  • When cuing a move, focus on the concepts of speed and the positions of the spine and joints. Remember that the spine and joint positions determine the correct mechanics of any move, while the speed can negatively affect the safety of its execution.
  • After each class, ask participants for their feedback on the key biomechanics principles that determine the safety and efficacy of each exercise. When participants are first learning the concepts, encourage them to ask questions before you add any progressions to the basic moves.
Brush Up on Biomechanics

A biomechanics approach to group fitness classes is particularly helpful when working with novice exercisers, elderly clients, those who are overweight or obese and those who have special medical needs. However, because biomechanical concepts affect the mechanics and organization of all exercises, their application is universal to all group settings.

By integrating the principles of biomechanics into your group fitness classes, you can increase the effectiveness and safety of exercise for your participants, while helping them achieve the results they want in order to lead a healthier and happier life.

10 ways to integrate biomechanics into your classes

Here’s a simple step-by-step guide for applying the biomechanical concepts discussed in this article in your own group fitness classes.

1. Identify the type of class you want to teach. For example, will you be teaching a functional class (e.g., core training, strength conditioning, sport-specific training, stretching), one that is muscle-specific (e.g., abdominals) or one that is geared toward an activity (e.g., kickboxing or step)? Or will the class target participants by gender, age, fitness level or medical condition (e.g., arthritis)?

2. Define the participants’ common fitness goals. Remember that most classes are only 60–90 minutes long, so you should focus on the two or three most common goals.

3. Select a few key exercises that will help participants reach those goals.

4. Limit the exercises to those that are easy to define, teach and repeat. Choose moves in which participants need to control as few dimensions as possible.

5. Organize exercises in a logical sequence of progression. Keep in mind that movements can be done in building blocks.

6. Identify the joints and muscles involved in the selected exercises.

7. Know the mechanics of any exercise you plan to include, based on the spine and joint position(s) and the speed involved in the movement.

8. Keep changes in direction, the use of different planes of movement, and rotational movements to a minimum.

9. Minimize the use of balance (unless that in itself is a class goal), and limit the number of weight-shifting exercises.

10. When sequencing the exercises, use these popular strategies: Move from large to small muscles at a joint; from a unidirectional exercise (e.g., stationary lunge) to an exercise involving a change in directional movement (e.g., forward lunge); or from nonrotational to rotational movements.

As a rule, exercises with fewer dimensions are easier for group instructors to teach and for participants to execute correctly.