118 Chapter 6: Training for Strength same exercises and rep schemes should be used for several weeks consistently before transitioning to a different set of exercises and rep schemes. The principle of accommodation states the body’s response to a constant stimulus decreases over time. While performing two sets of 10 reps with 90 lbs. on the bench press may be an appropriate stimulus initially, if the stimulus does not change, the body will eventually adapt and thereby prevent further physiological adaptations from occurring (e.g., increased muscular size and strength). Herein lies the dilemma, not using a specific set of exercises and rep schemes long enough violates the principle of directed adaptation. However, using a specific set of exercises and rep schemes for too long violates the principle of accommodation. To prevent either scenario from occurring, it is recommended to change up the exercises and rep schemes used about every 3-6 weeks. The principle of progressive overload states that the training stimulus needs to increase over time in order for progress to continue. These increases can include changes in intensity (e.g., % 1RM), volume (e.g., number of sets and reps) and/or frequency (e.g., number of training days per week). The principle of 72 hours states that at least three days, assuming appropriate exercise intensity and volume were used, should be afforded between workout sessions using the same compound lift(s). For example, if the individual performed bench press on Monday, he/she could perform squats on Tuesday but would have to wait until at least Thursday before performing bench press again. The principle of individuality states that each individual has unique strengths and weaknesses and will respond to training differently. There are several factors that influence strength training potential such as age, gender, training experience, injury status, muscle fiber type, tendon insertion points and hormonal balance. The principle of reversibility states that the physiological adaptations associated with training are lost when training is stopped; however, detraining effects can be reversed when training is resumed. Impact of Strength Training on Body Composition and Bone Density Research has shown that strength training has a larger impact on body composition than endurance training (Boutcher, 2011). Additionally, regular strength training has been proven to decrease fat mass, increase fat-free mass and lessen the effects of sarcopenia (age-related loss of muscle mass and strength). Between the ages of 30 and 65, the average American loses a halfpound of muscle and gains one pound of fat each year (Walters & Byl, 2013). Figure 6.1 depicts a magnetic resonance imaging (MRI) scan of the upper leg. The scan shows some of the body composition changes associated with aging. Although the circumference of the thigh remained relatively unchanged, there is a significant increase in the amount of subcutaneous fat as well as a notable decrease in muscle mass. Additionally, there is a significant amount of bone loss, thereby increasing the risk of fractures and/or osteoporosis.
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