Strength and Flexibility Training

When talking about the benefits of exercise, keeping the heart and blood vessels healthy usually gets most of the attention. For many individuals, though, stretching and strength training exercises that barely raise the heart rate— and so aren’t considered moderate at all—may be just as important.

Strength Training and Body Composition

purple-weights-ball (purple-weights-ball.jpg)Strength training, also known as resistance training, weight training, or muscle-strengthening activity, is probably the most neglected component of fitness programs but one of the most beneficial. In fact, it’s so beneficial that the American College of Sports Medicine, the American Heart Association, and the 2008 Physical Activity Guidelines for Americans recommend that adults engage in strength training at least twice a week, to improve muscle strength and endurance. (1, 2)

To understand why strength training is so important to our overall fitness, it helps to understand a bit about body composition. Our body can basically be divided into two components. Fat mass consists of the body’s fat store, while fat-free mass is a combination of non-fat tissue such as muscle, bone, internal organs, and so on. A significant part of fat-free mass is lean body mass, which is essentially muscle.

strength-training-for-all (strength-training-for-all-a.jpg)

The Physical Activity Guidelines for Americans recommends that muscle strengthening activities be done at least two days a week. (2) Different types of strength training activities are best for different age groups.

Children and Adolescents: Choose unstructured activities rather than weight lifting exercises. (2) Examples:

  •  Playing on playground equipment
  • Climbing trees
  • Playing tug-of-war 

Active Adults: Weight training is a familiar example, but there are other options: (2)

  • Calisthenics that use body weight for resistance (such as push-ups, pull-ups, and sit-ups)
  • Carrying heavy loads
  • Heavy gardening (such as digging or hoeing) 

Older Adults: The guidelines for older adults are similar to those for adults; older adults who have chronic conditions should consult with a health care provider to set their activity goals. (2) Muscle strengthening activities in this age group include the following:

  • Digging, lifting, and carrying as part of gardening
  • Carrying groceries
  • Some yoga and tai chi exercises
  • Strength exercises done as part of a rehab program or physical therapy

Older adults who are at risk of falling should also do exercises to improve their balance.

    Muscle is metabolically active tissue. This means that it utilizes calories to work, repair, and refuel itself. Fat requires very few calories—it just kind of sits there. As we enter our mid to late twenties, we slowly start to lose muscle as part of the natural aging process. This means that the amount of calories we need each day starts to decrease, and it becomes easier to gain weight. By engaging in regular strength training exercise, it is possible to decrease this loss of lean muscle tissue and even replace some that has been lost already.

    Studies have shown strength training to increase lean body mass, decrease fat mass, and increase resting metabolic rate (a measurement of the amount of calories burned per day), in younger and older adults. (3, 4) While strength training on its own typically does not lead to weight loss, (5) its beneficial effects on body composition may make it easier to manage one’s weight and ultimately reduce the risk of disease, by slowing the gain of fat—especially abdominal fat. (6)

    Another beneficial effect of resistance training pertains to bone health. In addition to weight bearing cardiovascular exercise, weight training has been shown to help fight osteoporosis. For example, a study in postmenopausal women examined whether regular strength training and high-impact aerobics sessions would help prevent osteoporosis. Researchers found that the women who participated in at least two sessions a week for three years were able to preserve bone mineral density at the spine and hip; over the same time period, a sedentary control group showed bone mineral density losses of 2 to 8 percent. (7)

    Finally, in older populations, resistance training can help maintain the ability to perform functional tasks such as walking, rising from a chair, climbing stairs, and even carrying one’s own groceries. An emerging area of research suggests that muscular strength and fitness may also be important to reducing the risk of chronic disease and mortality, but more research is needed. (8-12)

    Many people are intimidated by the idea of resistance training or are afraid of injury. They need not be. A great idea is to consult an expert. Consider hiring an exercise physiologist or personal trainer for a few sessions until you have the confidence to branch out on your own. For more information and to locate a trainer contact the American Council on Exercise.

    Flexibility Training and Fitness

    Flexibility training or stretching exercise is another important part of overall fitness. While some recent studies have cast doubt on the benefits of stretching to reduce exercise-related muscle soreness and injury, (13, 14) flexibility training may help older adults preserve the range of motion they need to perform daily tasks and other physical activity. (15, 16) The American Heart Association recommends that healthy adults engage in flexibility training two to three days per week, stretching major muscle and tendon groups. (4) For older adults, the American Heart Association and American College of Sports Medicine recommend two days a week of flexibility training, in sessions at least 10 minutes long. (15)


    1. Haskell WL, Lee IM, Pate RR, et al. Physical activity and public health: updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. Med Sci Sports Exerc. 2007; 39:1423-34.

    2. U.S. Dept. of Health and Human Services. 2008 Physical Activity Guidelines for Americans. 2008.

    3. Hunter GR, McCarthy JP, Bamman MM. Effects of resistance training on older adults. Sports Medicine. 2004; 34:329-348.

    4. Williams MA, Haskell WL, Ades PA, et al. Resistance exercise in individuals with and without cardiovascular disease: 2007 update: a scientific statement from the American Heart Association Council on Clinical Cardiology and Council on Nutrition, Physical Activity, and Metabolism. Circulation. 2007; 116:572-84.

    5. Physical Activity Guidelines Advisory Committee. Physical Activity Guidelines Advisory Committee Report. 2008. Washington, D.C., 2008. Accessed December 8, 2010.

    6. Schmitz KH, Hannan PJ, Stovitz SD, Bryan CJ, Warren M, Jensen MD. Strength training and adiposity in premenopausal women: Strong, Healthy, and Empowered study. American Journal of Clinical Nutrition. 2007; 86:566-572.

    7. Engelke K, Kemmler W, Lauber D, Beeskow C, Pintag R, Kalender WA. Exercise maintains bone density at spine and hip EFOPS: a 3-year longitudinal study in early postmenopausal women. Osteoporos Int. 2006; 17:133-42.

    8. Katzmarzyk PT, Craig CL. Musculoskeletal fitness and risk of mortality. Medicine and Science in Sports and Exercise. 2002; 34:740-744.

    9. Gale CR, Martyn CN, Cooper C, Sayer AA. Grip strength, body composition, and mortality. International Journal of Epidemiology. 2007; 36:228-235.

    10. Bohannon RW. Hand-grip dynamometry predicts future outcomes in aging adults. J Geriatr Phys Ther. 2008; 31:3-10.

    11. Ling CH, Taekema D, de Craen AJ, Gussekloo J, Westendorp RG, Maier AB. Handgrip strength and mortality in the oldest old population: the Leiden 85-plus study. CMAJ. 2010; 182:429-35.

    12. Ruiz JR, Sui X, Lobelo F, et al. Association between muscular strength and mortality in men: prospective cohort study. BMJ. 2008; 337:a439.

    13. Thacker SB, Gilchrist J, Stroup DF, Kimsey CD, Jr. The impact of stretching on sports injury risk: a systematic review of the literature. Med Sci Sports Exerc. 2004; 36:371-8.

    14. Herbert RD, de Noronha M. Stretching to prevent or reduce muscle soreness after exercise. Cochrane Database of Systematic Reviews. 2007.

    15. Nelson ME, Rejeski WJ, Blair SN, et al. Physical activity and public health in older adults: recommendation from the American College of Sports Medicine and the American Heart Association. Circulation. 2007; 116:1094-105.

    16. Chodzko-Zajko WJ, Proctor DN, Fiatarone Singh MA, et al. American College of Sports Medicine position stand. Exercise and physical activity for older adults. Med Sci Sports Exerc. 2009; 41:1510-30.

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