This is an excerpt from Christian Paths to Health and Wellness 3rd Edition With Web Study Guide-Loose-Leaf Edition by Peter Walters & John Byl.
Although you may not have competitive aspirations regarding your strength, you may have considered pumping iron to shape and firm your body. This chapter outlines the following five major benefits of strength training:
- Shapes your body
- Helps boost fat-burning metabolism
- Assists in building strong bones
- Reduces risk of neuromuscular injury
- Enhances functional capacity
Shapes Your Body
A common misconception among women is that if they lift weights, they will experience muscular hypertrophy. Simply put, hypertrophy means muscle enlargement and is the opposite of atrophy, or muscle wasting. While it is true that both men and women have the capacity for muscle hypertrophy, a female's capacity for muscle enlargement is generally much more limited than that of a male. One of the main reasons for this disparity is hormonal; men have 20 to 30 times more testosterone than women, as figure 5.1 illustrates (McGlynn & Moran, 1997). High levels of testosterone help create a growth environment for muscular development. Hormonal disparities and other factors have resulted in the average female having about half (40 to 60 percent) of the upper-body strength and three-quarters (65 to 85 percent) of the lower-body strength of their male counterparts.
Figure 5.1 Minimum (shaded) and maximum (bold) levels of testosterone for women and men.
McGlynn and Moran (1997, pg. 108).
Women who lift weights are much more likely to achieve results like those seen in figure 5.2. These before-and-after photographs depict a female who participated in an experimental 16-week resistance-training course focused on building muscle and losing fat. These pictures illustrate the more typical body composition changes women can achieve through strength training. The average female in this 16-week class lost 11.7 pounds (5.3 kg) of fat while gaining 3.7 pounds (1.7 kg) of muscle. Figure 5.3 shows the changes that occurred in a man who participated in the same study. The average male lost a little more than 1 pound (0.45 kg) of fat per week, or 18.3 pounds (8.3 kg) total. It should be noted that participants in this experiment were required to adhere to a strict dietary regimen. Therefore, the changes are not representative of people who only engage in strength training.
Helps Boost Fat-Burning Metabolism
Weight training turns the body into a fat-burning machine. Here is how. Resting metabolic rate (RMR), the rate at which the body burns calories when completely inactive, is affected by the amount of lean body mass (muscle)a person has. Each pound (0.45 kg) of muscle burns 30 to 40 calories per day at rest (Darden, 1995; Westcott, 1994), making it the most metabolically active substance in the human body. By contrast, a pound of fat burns 1 to 2 calories per day. It follows that a person who gains 5 pounds of muscle (2.3 kg) will burn 150 to 200 more calories per day by adding this additional lean tissue. This is one reason why many experts advise those who want to ultimately lose weight to gain muscular weight at the beginning.
The power of resistance training to affect fat has been well documented. In one study (Westcott, 1994), 72 men and women agreed to exercise for 30 minutes a day, three days a week, for 12 weeks. Twenty-two of the participants spent the entire 30 minutes in cardiovascular exercise. The other 50 participants divided their workouts into 15 minutes of aerobic exercise and 15 minutes of strength training. Table 5.1 shows the changes in body composition for each group.
In a more recent review comparing the effects of fat loss using either high-intensity exercise (mostly in the form of resistance training) or steady-state aerobic exercise, Stephen Boutcher (2011), at the University of South Wales School of Medicine, reported that high-intensity strength training was much more effective than aerobic exercise at reducing fat.
The average adult between the ages of 30 and 65 loses half a pound (0.2 kg) of muscle per year (Westcott, 1994). While that may seem insignificant, it actually is 6,387.5 fewer calories per year (since 0.5 pound of muscle burns 17.5 calories per day for 365 days = 6,387.5). That is right at 2 pounds of fat, which is the average most adults over the age of 30 gain per year.
Assists in Building Strong Bones
Most people realize that resistance training develops muscles, but few realize that it strengthens bones as well. Weight training prevents or delays the loss of bone tissue. Bones consist of hard weblike structures of collagen, calcium, and other minerals; which combine to make up the bonematrix. The structure of the bone matrix has gaps which are filled with bone marrow and blood vessels. Osteoporosis (derived from the Greek words for bone and porous) is the breakdown of the bone mineral web, which makes the bone more vulnerable to fractures. This process accelerates with age, resulting in 55 percent of people over age 50 having low bone density (National Osteoporosis Foundation, 2009). Figure 5.4 illustrates how bone mineral density is affected by osteoporosis (National Osteoporosis Society, 2020).
Our bones are constantly being broken down and regenerated. Scientists estimate that our skeletons are completely regenerated every 10 years (American Academy of Orthopedic Surgeons, 2020). Cells called osteoclasts break down bone matrix and release minerals, such as calcium, into the blood. In contrast, cells called osteoblasts rebuild the bone matrix (Feng & McDonald, 2011). Although these two processes are continually occurring throughout life, osteoblast activity dominates through one's 20s and 30s yielding a peak bone mineral density during that time. After the age of 30, osteoclasts activity dominates.
While researchers have known that calcium supplements help prevent osteoporosis, recent studies indicate that resistance training may be just as important if not more important than calcium for skeletal integrity (Hong et al., 2018).
In one study (Dornemann et al., 1997), 39 women were divided into two groups. Both groups had adequate calcium intake, but the first group did strength training twice a week while the second group did not. After one year, testing revealed that, on average, bone mineral density decreased by 2 percent in the group that did not engage in resistance training but increased by 1 percent in the group that did (Dornemann et al., 1997). A more recent study revealed a similar effect on men (Kukuljan et al., 2011). A total of 180 men between the ages of 50 and 79 years old were divided into four groups: one that only exercised, one that drank calcium-fortified milk, one that both exercised and consumed fortified milk, and the control group, which did not exercise or drink fortified milk. After 18 months, the results indicated that fortified milk, whether alone or combined with exercise, did not enhance bone mineral density. In contrast, those who exercised increased bone mineral density in both the femoral neck and the lumbar spine.
Reduces Risk of Neuromuscular Injury
Eric Helland, strength and conditioning coach of the Chicago Bulls basketball team, stated, “The number one reason I want my athletes in the weight room is that it protects them from injury” (personal communication, June 2009). Whether you're a multimillion-dollar sports star or a weekend warrior, resistance training can dramatically lower your chance of musculoskeletal injuries.
One vivid example of this effect has been reported among those suffering from lower back pain and injury. Lower-back pain is the second most common health problem reported by Americans, ranking just below the common cold (Wipf & Deyo, 1995). About 8 out of 10 people will have lower-back pain at some point in their lives (Eidelson, 2016), and one-quarter of U.S. adults report having lower-back pain in the past three months (Deyo et al., 2006). Back pain is responsible for more days in the hospital than any other medical condition except childbirth (Reynolds et al., 1990). At any given time, 31 million Americans have lower-back pain; and 80 million Americans have recurring back distress (Sharkey, 2002). These statistics have been used to argue that the lower back is the weakest link in the human musculoskeletal chain. Although that is debatable, there is no question that lower-back pain is a serious health care concern.
So how does strength training help reduce this common ailment? One long-term study examined the effect of lower-back strengthening on 50 postmenopausal women (Sinaki et al., 2002). Those who engaged in resistance exercises not only had greater bone mineral density but also reported far fewer back injuries. In fact, the control group, which did not engage in resistance exercises, had 2.7 times more lumbar fractures than the strength-training group during an eight-year period. In another randomized controlled trial of 537 industrial technicians, those who participated in as little as one resistance training session per week reported much less lower-back pain than subjects who did not engage in strength training (Pedersen et al., 2013). This effect was again observed in another large-scale study of office workers over the course of a year. In this study, workers who had reported the intensity of their lower-back pain at 3 or more (on a scale of 0 to 9) during the previous three months reported much less pain after engaging in resistance training than workers who did not strength train (Andersen et al., 2010). These and a host of other studies suggested a positive correlation between resistance training and reduced lower back difficulties (Seung-Houn et al., 2004; Wheeler, 1995).
Two beginning strength-training exercises that strengthen the lower back and protect it against injury are illustrated in figures 5.5 and 5.6. You can adjust the resistance in the incline back extension (figure 5.5) exercise by simply changing your arm placement. Placing your arms beside the hips is a good place to start because that reduces the amount of resistance you are working against. When your lower back gets stronger, try crossing your arms in front of your chest while performing this movement, which raises your center of gravity and makes the exercise more strenuous.
Figure 5.5 Seated back extension. Lean back so your upper back is in a straight line with your legs.
Figure 5.6 Incline back extension. Rise up so your upper back is in a straight line with your legs.
Enhances Functional Capacity
The ability to do physical work is called functional capacity. The average person's functional capacity peaks between the ages of 20 and 25, is maintained until about age 30, and then slowly begins to decline. Of the many factors that influence functional capacity, muscular strength is one of the most important. It is impossible to move without contracting a muscle.
An increase in muscular strength—that is, the ability to exert more force—is perhaps the most apparent result of weight training. Increases in strength occur quickly when individuals begin resistance training. Several studies report a 30 to 40 percent increase in strength after only three months (Westcott, 1994). This effect has even been verified among individuals beyond the age of 90 (Fiatarone, 2002). In summary, strength training cannot only be used to shape and form the body but to increase metabolic rate, support skeletal health, reduce the risk of musculoskeletal injuries, and increase functional capacity.