Safety Principles of BODYPUMP

Although aerobic activities are effective for improving cardiorespiratory fitness, most have little effect on muscular fitness. Muscular fitness is an essential component of every exercise program. Research has shown that maintenance or enhancement of muscular fitness decreases the physiologic stress associated with performing nearly every activity--including activities of daily living, such as cooking, cleaning and going to work. Research has also shown that resistance training (exercise designed to improve muscular fitness) has favorable effects on bone density, body composition, cardiovascular function, metabolism, coronary risk factors and psychosocial well-being. The fitness industry has been aware of these benefits for many years, but not until classes like BODYPUMP entered the fitness arena have people been more enthusiastic about pumping up!

Muscular Fitness

Muscular fitness includes both muscular strength and endurance. Muscular strength refers to the maximal force that can be generated by a specific muscle or muscle group. Muscular endurance, on the other hand, is the ability of a muscle or muscle group to exert submaximal force for several repetitions. Muscular strength and endurance are developed by what is referred to as the "overload principle." Overload occurs when the resistance to movement, frequency or duration of activity is increased. This can be accomplished by varying the weight, amount of rest and sets of exercises.

Muscle Action

Depending on the source, the word "contraction" has been used to describe several types of muscle actions including concentric, eccentric, isometric, isotonic, isokinetic and isoinertial. However, the focus of this article is on the basic muscle actions performed in a BODYPUMP class: isometric and the concentric and eccentric phases of isotonic contractions.

Isometric Contractions

During an isometric contraction, no joint motion occurs. The limitation of isometric contractions is that the muscle is only strengthened at the specific joint angle that is used in the exercise. As a result, this type of muscle contraction is typically used for specialized purposes, such as overcoming a weakness in a specific range of motion.

Isotonic: Concentric Contractions

Both concentric and eccentric contractions involve joint motion. Concentric contractions require the greatest energy expenditure, followed by isometric and eccentric contractions. Concentric contractions involve what is termed "positive work"--the muscle is shortened while developing tension, such as during the "up" phase of a bicep curl.

Isotonic: Eccentric Contractions

Conversely, eccentric contractions occur when the muscle is lengthened while developing tension. Eccentric contractions usually occur when a muscle acts to oppose the force of gravity, such as during the "down" phase of a bicep curl. (Figure 1). Eccentric contractions generally develop greater muscle tension than both isometric and concentric contractions. Subsequently, the muscle is also more vulnerable to rupture during an eccentric contraction.

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Eccentric contractions have also been implicated in delayed onset muscle soreness (DOMS). Although the cause of DOMS is still debated, DOMS and muscle injury have been reported after just a single bout of eccentric exercise.

The single greatest risk factor, for musculoskeletal injury, with resistance training is previous injury. The risk is even greater when proper technique and body alignment are ignored. General guidelines for reducing the risk of injury during specific exercises are discussed below.

Lower Body

The knee is one of the most vulnerable sites of injury in the body and when weight is added, the risk is greater. Therefore, proper technique should be emphasized when performing exercises involving the lower body, such as squats and lunges.

Squats

When performing squats, the knees should be about shoulder width apart, with the knees and toes facing forward. The weight bar should be placed in a comfortable position on the neck and the hands can either grip the weight bar or the forearms can rest comfortably on the weight bar. The squat should be performed in a controlled manner, with heels on the floor during the entire exercise.

During the descent (eccentric phase), the tailbone should point rearward without arching the back and the hips should not drop below knee level. As the knees flex, the force on the knee joint and surrounding soft tissues increases. Therefore, participants who have a pre-existing knee injury or are susceptible to knee injury should limit their knee flexion. During the ascent (concentric phase), the knees should extend (without hyperextending) until a neutral alignment of the pelvis is achieved.

Lunges

Similar to squats, lunges should be performed in a controlled manner and the knees should not extend beyond the toes. The front leg should remain perpendicular to the floor and the hip should not drop below knee height. Lunges are one of the most difficult and potentially dangerous exercises to perform. Some people simply cannot perform lunges correctly due to injury, musculoskeletal malalignments, poor flexibility or coordination. As a result, proper technique should always be reviewed prior to performing lunges.

Upper Body

In a BODYPUMP class, upper body exercises are performed to strengthen the arms, chest, shoulders and back. These exercises are usually performed in isolation (the lower body is not moving at the same time). This allows participants to focus on the specific muscles being worked, while concentrating on proper technique and body alignment. For upper body exercises performed in a standing position, abdominals should be contracted, the rib cage lifted, knees relaxed and the pelvis remaining in a neutral position.

A common mistake is using momentum in upper body exercises (i.e., swinging the arms or using the torso to assist with the exercise). Exercises should be done in a controlled manner, over a full range of motion and without hyperextending the joints. BODYPUMP is choreographed to music specifically designed for the exercises being performed. However, this special music should not deter an instructor from making a judgment call to slow the music or even interrupt an interval to demonstrate proper technique.

Low Back

Similar to the knees, the low back is also highly susceptible to injury. In fact, it is estimated that 80 percent of the population will develop back pain some time in their lives. Although there are many causes of low back pain, up to 80 to 90 percent of low back pain has been attributed to improper posture, poor body mechanics and weak or imbalanced musculature. In most cases, low back pain can be alleviated or prevented by a properly designed exercise program.

In a BODYPUMP class, the low back is constantly loaded, even when the focus of the exercise is on another part of the body. For example, when using two 15 pound hand weights for a bicep curl, the compressive force on the lower back for an average male is about 300 pounds. When the weights are held further away from the front of the body (i.e., during a front arm raise) or when the torso is bent forward, the force on the low back increases even more. Thus, when lifting 10 pounds from a bent over position, the compressive force on the back can be 4 to 5 times body weight (BW). (Figure 2). To mitigate these forces, deadlifts should be performed with the weight bar close to the body and with the knees slightly bent during the entire exercise. Also, flexion should occur at the hips, not the spine.

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Abdominals

Abdominal strength is critical for providing support to the internal organs and back. Abdominal curls that flex the spine approximately 30 to 45 degrees are sufficient to improve the strength of the abdominal muscles. Flexion beyond this point engages the iliopsoas or hip flexor muscles.

During an abdominal curl, the pelvis should be in a neutral position and the lower back should remain on the floor. The arms should support the neck without pulling the head forward. Keep in mind that abdominal muscle force increases as the arms are extended further above the head. Lying in a supine position with the legs extended and held off the floor also places significant stress on the low back. The stress on the low back increases as the legs are lowered from a vertical position (i.e., extended directly overhead) to a position that is parallel with the floor.

Muscle Balance

In every joint action, a group of muscles works together to perform the desired motion. The muscle responsible for producing the desired motion is called the agonist or primary mover, while the muscle that is directly opposite the desired motion is called antagonist. The synergist muscle(s) assists the agonist with the desired motion while the neutralizer acts to stabilize the joint or prevent unwanted action of a muscle.

The agonist and antagonist muscles work in concert to create muscular balance in the human body. If one of the pair is substantially stronger or weaker than the other, then an imbalance is created--the stronger muscle ends up compensating for the weaker muscle. Ultimately, this can result in improper body alignment and serious injury. Below are a few examples of agonist/antagonist muscle pairs.

AGONIST                ANTAGONIST

Biceps                 Triceps
Deltoids               Latissimus Dorsi
Pectorals              Trapezius/Rhomboids
Abdominals             Erector Spinae
Iliopsoas              Glueteus Maximus
Abductors              Adductors
Quadriceps             Hamstrings
Gastrocnemius/Soleus   Tibialis Anterior

From Fitness Theory & Practice, 2nd Edition, USA, 1997.

Flexibility and range of motion are also important for preventing injury and maintaining proper muscle balance. Moving through a complete range of motion will strengthen the agonist and stretch the antagonist muscle. It will also help maintain adequate joint mobility.

Breathing

Although proper breathing is of great importance, it is often ignored. Holding one's breath during strenuous exercise can cause significant increases in blood pressure and elicit a Valsava response. The Valsava response occurs when air is forced against a closed glottis (the narrowest part of the larynx, through which air passes into and out of the trachea). This can limit blood flow to the heart and brain, causing dizziness and even fainting. This reaction occurs during activities that require a rapid and maximum application of force for a short duration, such as during isometrics and heavy weight training. Hyperventilating or breathing too hard is also not advised. Proper breathing should be relaxed and involve inhaling during the eccentric phase and exhaling during the concentric phase of the exercise.

Whether you are teaching BODYPUMP or participating in a class, safety should always be a primary consideration. Ultimately, it is the instructor's responsibility to be informed about the inherent risks involved in teaching BODYPUMP, so that they can be mitigated appropriately. Most of all, participants should be encouraged to start slowly, but challenge themselves to improve. In summary,

* Always double check that collars on the end of the weight bars are tightly secured

* Always include an appropriate warm-up

* Choose appropriate weights--those suitable for many repetitions

* Progress at a reasonable pace

* Use tempo changes to emphasize different muscle actions

* Pay close attention to forces at the knees and low back

* Use proper body alignment and perform exercises in a controlled manner

* Perform exercises over a complete range of motion

* Use the cool-down to emphasize stretching, particularly of the muscles exercised.

Questions: Safety Principles of BODYPUMP

Code No. 0045

1. Muscular fitness is generally
   NOT improved by which of
   the following?

A. Resistance training
B. Aerobic exercise
C. BODYPUMP
D. Weight lifting

2. The maximal force that can be
   exerted by a specific muscle or
   muscle group is called
   --.

A. muscular endurance
B. muscular fitness
C. muscular strength
D. overload principle

3. The overload principle
   refers to:

A. Increasing the resistance to
   movement.
B. Increasing the frequency
   of activity.
C. Increasing the duration
   of activity.
D. All of the above.

4. What type of muscle action
   requires the greatest energy
   expenditure?

A. Concentric
B. Eccentric
C. Isokinetic
D. Isoinertial

5. Which type of muscle
   contraction is used for
   specialized purposes, such as
   overcoming a weakness at a
   specific range of motion?

A. Eccentric
B. Concentric
C. Isokinetic
D. Isometric

6. What type of contractions are
   associated with DOMS?

A. Isokinetic
B. Isoinertial
C. Eccentric
D. Isometric

7. Which of the following is NOT
   true with regard to concentric
   contractions?

A. They involve "positive work."
B. The muscle lengthens as it
   develops tension.
C. The muscle shortens as it
   develops tension.
D. They occur during the ascent
   phase of a squat.

8. Which is the single greatest
   risk factor for musculoskeletal
   injury with resistance training?

A. Improper body alignment
B. Muscle imbalance
C. Previous injury
D. Performing exercises too fast

9. As the knee flexes, the force on
   the knee joint --.

A. increases
B. decreases
C. doesn't change
D. None of the above.

10. When performing abdominal
    exercises in a supine position,
    which of the following
    positions results in the highest
    stress on the low back?

A. Knees bent to 90 degrees and
   feet placed on the floor
B. Knees extended with legs directly
   over head
C. Knees extended with legs held
   two inches off the floor
D. Knees bent to 90 degrees with
   the feet two inches off the floor

11. While performing a bicep
    curl in a standing position, the
    force on the low back is
    -- the low back
    force during a front arm raise
    using the same weight.

A. greater than
B. less than
C. about the same
D. None of the above.

12. The primary mover during
    any joint action is the
    --.

A. agonist muscle
B. stabilizing muscle
C. antagonist muscle
D. fixator muscle

13. Which of the following
    muscles are NOT
    agonist/antagonist
    muscle pairs?

A. Quadriceps/Hamstrings
B. Iliopsoas/Gluteus Maximus
C. Abdominals/Erector Spinae
D. Serratus Anterior/Pectorals

14. Which of the following is/are
    important for maintaining
    proper muscle balance?

A. Working both the agonist and
   antagonist muscles
B. Maintaining flexibility
C. Performing exercises over a
   limited range of motion
D. a) and b) only

15. Which of the following is
    NOT accurate with regard
    to the Valsalva response?

A. It can limit blood flow to the
   heart and brain.
B. It can cause dizziness and
   fainting.
C. It occurs during activities that
   require a rapid and maximum
   application of force for a short
   duration, such as during
   isometrics and heavy weight
   training.
D. All of the above.

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Jessica Smith, M.E., P.E., has a master's degree in bioengineering and is currently working on her Ph.D. in bioengineering at the University of Utah. Her research interests are in biomechanics, specifically the areas of injury prevention and sport performance. She is also a former elite level gymnast and has been a certified aerobics instructor for the past eight years.

COPYRIGHT 2001 Aerobics and Fitness Association of America
COPYRIGHT 2001 Gale Group