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Safety Principles of BODYPUMP

American Fitness, July, 2001 by Jessica Smith

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!

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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.

Safety Principles of BODYPUMP

American Fitness, July, 2001 by Jessica Smith

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