Get 'Em Powered Up!

by Cody Sipe, MS on Apr 01, 2005

Use power training to enhance or maintain functional abilities in aging adults.

The Baby Boomer and older-adult populations are increasing at unprecedented rates. It is anticipated that the U.S. population of adults over the age of 65 will double by the year 2030, rising to an estimated 71.5 million people (U.S. Administration on Aging 2004). Personal fitness trainers (PFTs) have the opportunity to serve this huge market by developing appropriate and effective exercise programs that target functional abilities.

Why Focus on Function?

While a disproportionately large percentage of older adults who belong to fitness facilities are fit or athletic, the majority of those over 60 who have not joined clubs can be classified as either “frail” or “independent” (see “Hierarchy of Physical Function of the Old and Oldest-Old,” below). For this large group of potential customers, the loss of function is a serious threat to their independence and quality of life. Among adults aged 65–74, 18% of men and 20% of women report an inability to perform at least 1 in 5 basic physical activities (stooping/kneeling, reaching overhead, writing, walking 2–3 blocks, lifting 10 pounds) (U.S. Administration on Aging 2004). Those numbers climb to 35% and 58% for men and women, respectively, after the age of 85 (U.S. Administration on Aging 2004). In addition, estimates for the prevalence of sarcopenia, the significant loss of muscle mass and strength with advancing age and an independent risk factor for the development of disability, range from 22% to 53% in the older-adult population (Iannuzzi-Sucich, Prestwood & Kenny 2002).

Muscle Strength

The relationship between muscle mass, muscle strength and functional abilities has been well documented, with numerous studies demonstrating that increases in muscle strength typically result in improvements in functional abilities. But according to a recent review of the literature (Keysor & Jette 2001), this evidence is rather inconsistent. While methodological issues may explain much of the variation, many researchers are turning their attention to muscle power as a potentially more valuable training method for maximizing function in older adults.

What Is Power?

Power is the product of force and velocity. Specifically, muscle power is the product of the force generated by the muscle and the velocity at which the contraction is performed. In other words, power is the rate (speed) at which force is generated. For example, if person A can perform a submaximal repetition more quickly than person B, then person A is generating more power because he or she is generating more velocity.

At extremely low forces (%1RM), contractile velocity is maximized; movements can be performed more quickly when using lower resistance loads. As %1RM increases, the maximal velocity of the muscle decreases in a linear fashion. Once the force capabilities of the muscle are exceeded, velocity—and, therefore, power output—drops to zero. In older adults it appears that peak power is achieved at roughly 70% 1RM (Bean et al. 2004). However 1RM testing is not extremely reliable; some data suggest that peak power occurs more consistently at 50% of a person’s extrapolated isometric maximum (unpublished data from the Keiser Corporation).

Elder Power

Why is power important for older adults? Sarcopenia results in the preferential atrophy of type 2 (fast-twitch) muscle fibers, leaving the remaining muscle mass smaller, weaker and slower. This has a dramatic impact on potential power generation. In fact, the power output of type 2 fibers is approximately four times that of type 1 fibers. Cross-sectional studies confirm this by reporting that muscle power declines earlier and more precipitously than either strength or velocity with advancing age (Metter et al. 1997). If a person’s strength and velocity both decrease by 40% (a realistic possibility) then power will be reduced by 64% (0.6 x 0.6 = 0.36)!

This is unfortunate, since many activities such as walking quickly, climbing stairs, transferring body weight and playing recreational sports require the ability to generate force quickly. Traditional resistance training methods focus on improving muscle strength but neglect velocity. In fact, traditional methods work against it, in a way, by dictating that the movements be performed in a slow, controlled manner.

Muscle power has consistently been more highly correlated than strength with many functional abilities. Comparison studies of power and strength training have reported similar increases in strength, but larger gains in power in those who practice power training (Fielding et al. 2002). A growing body of evidence also suggests that power training may improve functional abilities more than traditional low-velocity strength training, especially for lower-functioning subjects (Fielding et al. 2002; Hruda, Hicks & McCartney 2002; Miszko et al. 2003). This is very likely the case for recreational sports performance as well.

While there aren’t any hard and fast rules, it is generally accepted that high-speed movements with moderate to heavy loads qualify as power training. Therefore, just performing the same strength training movements more quickly will result in an increase in power. How fast is fast enough? The literature has not fully addressed that question. Typically the movements are performed “as fast as possible.” Some experts, erring on the side of caution, have recommended that older adults gradually increase their speed over several sessions.

Equipment & Exercise Selection

A worker is only as good as his tools; unfortunately, the tools most fitness professionals have to work with are probably not the most appropriate for maximizing power generation.

Gravity-Based Equipment

Dumbbells, barbells and selectorized stacks are all gravity-based training tools. One reason experts have stressed the importance of performing resistance exercises in a slow, controlled manner is to avoid momentum. Momentum is the tendency of an object in motion to stay in motion. When it comes to performing movements at high velocities, however, inertia also becomes a problem. Inertia is the tendency of an object at rest to stay at rest.

Strength production curves at higher velocities reveal that great force is required to initiate movement (in order to overcome inertia) but force production drops off considerably as the speed of the weight picks up (momentum). Force production at the beginning of the movement increases dramatically at higher velocities.

Termination of the movement presents its own set of potential problems. Since the weight is moving at a higher velocity, more effort is needed to slow down and stop the weight. But more effort may not always be possible. Consider a high-velocity leg press on a selectorized weight stack. If enough speed is generated, the foot plate will come out of contact with the soles of the shoes. As the weight stack and foot plate come back to the user, the weight will generate its own momentum and a great deal of eccentric force will be required to stop it safely. This presents an extremely dangerous situation for the ankle, knee and hip joints of older adults. Based on these considerations, it appears that free weights and weight stack machines are not the best tools to use in a power training program for this population. (For a detailed discussion on momentum, see “Counteracting Momentum During Exercise” by Amy Ashmore, PhD, IDEA Fitness Journal, September 2004, p. 39).

Pneumatic Equipment

Some pneumatic equipment has tight resistance and is very controlled, providing a smooth force curve throughout the range of motion. Most pneumatic machines use a much simpler method, akin to hydraulic resistance, wherein the amount of resistance is controlled by the speed of the movement: The faster a person performs the movement, the greater the resistance. This is a less-than-optimal environment for increasing power. Equipment with tight resistance and control can virtually eliminate inertia and momentum. Since it doesn’t matter how fast or slow a person performs the movement, an individual can safely and effectively train for power.

Resistance Bands

Since not everyone has access to pneumatic equipment, resistance bands can be considered a preferred alternative. Although the resistance increases slightly as the band is stretched, the resistance curve stays the same regardless of speed—and without inertia or momentum. More exercise options are available than with larger equipment, and the bands are low-cost and portable.

Body Weight

Using body weight is another good option for improving power. This method allows for the practice of real-life, functional movements, such as climbing stairs and rising from a chair. If body weight is an insufficient stimulus, then the addition of weight vests, weight belts, sandbags or dumbbells can safely and effectively increase resistance. In addition, movements using body weight require more balance and coordination than machine-based movements, so there may be additional benefits to your client. Unfortunately, inertia and momentum are inherent in these movements since they are gravity-based, but some studies have used body weight exercises in their training and have shown positive results (Bean et al. 2004; Bean et al. 2002).

Exercise Selection

The power-generating capabilities of the lower-body musculature have been preferentially investigated owing to the importance of these muscles in mobility and in many functional activities. Movements that have been used include the leg press, leg extension, leg curl, calf raise, hip abduction, hip adduction, stair climbs, hip flexion and squats/chair stands. However, diagonal walking patterns, hip extension, speed walking, fast marches and a variety of other movements can also be used.

A Tailored Approach

The burgeoning older-adult market is open to PFTs who want to position themselves as senior fitness experts and tailor their approaches to the needs of this population. Since the majority of older adults are neither physically elite nor fit, strategies like power training that can enhance or maintain functional abilities should be a central aspect of program design.

hierarchy of physical function of the old (75–85 years) and oldest-old (86–120 years)

Physically Elite: Train physically on a daily basis and compete in tournaments such as Senior Olympics, masters’ tournaments and general competitions (such as 10K races).

Physically Fit: Perform moderate physical work; exercise regularly for health, enjoyment and well-being, but do not compete.

Physically Independent: Perform very light physical work and some AADLs. Although they do not exercise, they have not been burdened with debilitating disease and are able to function independently.

Physically Frail: Perform light housekeeping, some IADLs, all BADLs. They have a debilitating disease or condition that physically challenges them on a daily basis and are, therefore, very close to becoming dependent.

Physically Dependent: Cannot perform some or all BADLs; are dependent on others for basic functions of living such as bathing, feeding, dressing, transferring, etc.

declines earlier and more precipitously than either strength or velocity with advancing age (Metter et al. 1997). If a person’s strength and velocity both decrease by 40% (a realistic possibility) then power will be reduced by 64% (0.6 x 0.6 = 0.36)!

This is unfortunate, since many activities such as walking quickly, climbing stairs, transferring body weight and playing recreational sports require the ability to generate force quickly. Traditional resistance training methods focus on improving muscle strength but neglect velocity. In fact, traditional methods work against it, in a way, by dictating that the movements be performed in a slow, controlled manner.

Muscle power has consistently been more highly correlated than strength with many functional abilities. Comparison studies of power and strength training have reported similar increases in strength, but larger gains in power in those who practice power training (Fielding et al. 2002). A growing body of evidence also suggests that power training may improve functional abilities more than traditional low-velocity strength training, especially for lower-functioning subjects (Fielding et al. 2002; Hruda Hicks, & McCartney 2002; Miszko et al. 2003). This is very likely the case for recreational sports performance as well.

While there aren’t any hard and fast rules, it is generally accepted that high-speed movements with moderate to heavy loads qualify as power training. Therefore, just performing the same strength training movements more quickly will result in an increase in power. How fast is fast enough? The literature has not fully addressed that question. Typically the movements are performed “as fast as possible.” Some experts, erring on the side of caution, have recommended that older adults gradually increase their speed over several sessions. At any rate, there are some important equipment and methodological considerations to consider when performing power training with older adults.

Equipment & Exercise Selection

A worker is only as good as his tools; unfortunately, the tools most fitness professionals have to work with are probably not the most appropriate for maximizing power generation.

Gravity-Based Equipment

Dumbbells, barbells and selectorized stacks are all gravity-based training tools. One reason experts have stressed the importance of performing resistance exercises in a slow, controlled manner is to avoid momentum. Momentum is the tendency of an object in motion to stay in motion. When it comes to performing movements at high velocities, however, inertia also becomes a problem. Inertia is the tendency of an object at rest to stay at rest.

Strength production curves at higher velocities reveal that great force is required to initiate movement (in order to overcome inertia) but force production drops off considerably as the speed of the weight picks up (momentum). Force production at the beginning of the movement increases dramatically at higher velocities.

Termination of the movement presents its own set of potential problems. Since the weight is moving at a higher velocity, more effort is needed to slow down and stop the weight. But more effort may not always be possible. Consider a high-velocity leg press on a selectorized weight stack. If enough speed is generated, the foot plate will come out of contact with the soles of the shoes. As the weight stack and foot plate come back to the user, the weight will generate its own momentum and a great deal of eccentric force will be required to stop it safely. This presents an extremely dangerous situation for the ankle, knee and hip joints of older adults. Based on these considerations, it appears that free weights and weight stack machines are not the best tools to use in a power training program for this population. (For a detailed discussion on momentum, see “Counteracting Momentum During Exercise” by Amy Ashmore, PhD, IDEA Fitness Journal September 2004, p. 39).

Pneumatic Equipment

Some pneumatic equipment has tight resistance and is very controlled, providing a smooth force curve throughout the range of motion. Most pneumatic machines use a much simpler method, akin to hydraulic resistance, wherein the amount of resistance is controlled by the speed of the movement: The faster a person performs the movement, the greater the resistance. This is a less-than-optimal environment for increasing power. Equipment with tight resistance and control can virtually eliminate inertia and momentum. Since it doesn’t matter how fast or slow a person performs the movement, an individual can safely and effectively train for power.

Resistance Bands

Since not everyone has access to pneumatic equipment, resistance bands can be considered a preferred alternative. Although the resistance increases slightly as the band is stretched, the resistance curve stays the same regardless of speed—and without inertia or momentum. More exercise options are available than with larger equipment, and the bands are low-cost and portable.

Body Weight

Using body weight is another good option for improving power. This method allows for the practice of real-life, functional movements, such as climbing stairs and rising from a chair. If body weight is an insufficient stimulus, then the addition of weight vests, weight belts, sandbags or dumbbells can safely and effectively increase resistance. In addition, movements using body weight require more balance and coordination than machine-based movements, so there may be additional benefits to your client. Unfortunately, inertia and momentum are inherent in these movements since they are gravity-based, but some studies have used body weight exercises in their training and have shown positive results (Bean et al. 2004; Bean et al. 2002).

Exercise Selection

The power-generating capabilities of the lower-body musculature have been preferentially investigated owing to the importance of these muscles in mobility and in many functional activities. Movements that have been used include the leg press, leg extension, leg curl, calf raise, hip abduction, hip adduction, stair climbs, hip flexion and squats/chair stands. However, diagonal walking patterns, hip extension, speed walking, fast marches and a variety of other movements can also be used.

A Tailored Approach

The burgeoning older-adult market is open to PFTs who want to position themselves as senior fitness experts and tailor their approaches to the needs of this population. Since the majority of older adults are neither physically elite nor fit, strategies like power training that can enhance or maintain functional abilities should be a central aspect of program design.

exercise selection

Owing to the lack of literature in this area, no power training recommendations for older adults have been published. Most studies have used a 3-set, 8- to 10- repetition, 3-day-per-week design with intensity set at 40%–70% 1RM in order to maximize results. Following this protocol is a reasonable place to start. 1. Explosive Chair Stand With Vest

Put on weighted vest equal to 5%–10% of body weight. Sit erect in sturdy chair or on end of bench with feet about shoulder width apart and arms folded across chest. Stand up as quickly as possible, pushing with entire foot to prevent rising up on toes. Slowly (taking about 3 seconds) sit back down in chair. As soon as bottom touches chair, explode up again to standing position. Increase weight as able.

2. Stair Climb With Vest

Put on weighted vest equal to 5% of body weight. Place 4- to 8-inch step bench in front of you on floor. Step up onto bench with right foot and plant it firmly onto bench while left foot remains on floor. Step up as quickly as possible and place left foot onto bench beside right foot. (Try to avoid using left calf to assist propulsion onto bench). Slowly return left foot to starting position. Perform 10–12 repetitions and repeat with other leg. Increase weight as able.

3. Quick Side Steps With Band

With feet about 4 inches apart, put tubing around ankles so it is taut but not tight. Place two marks on ground about 18–24 inches apart (depending on leg length). Standing on left spot, quickly step sideways and place right foot on other spot. Bring left leg slowly to right leg. Repeat in other direction 10–12 times.

Variation: Life is not restricted to lateral or frontal movements, so try stepping in all directions to challenge hip muscles in new ways.

4. Hip Flexion With Band

Place one end of band or tubing around right ankle and attach other end to stationary object immediately behind you on floor (recommended), or step on band with left foot. (Use wall or other object for balance, if needed.) As quickly as possible, bring right knee up to hip height (bend knee on ascent, like marching with high knees), pause, and slowly return to starting position. Perform 10–12 repetitions and then repeat with other leg.

5. Calf Raises With Vest

Stand with both feet flat on floor, a little closer than shoulder width apart. Rise up on toes as quickly as possible and then slowly return to starting position. If this movement is too easy, try performing it while wearing weighted vest or use one leg at a time.

6. Leg Press

Using a pneumatic leg press, sit with back firmly against back rest and feet planted firmly on foot plate so knees are bent at an 80°–90° angle. Set weight to about 70% 1RM. Push with both feet as quickly as possible until legs are fully extended, ensuring (on each side) that entire foot remains firmly planted against foot plate. Slowly return to starting position. As soon as foot plate is fully lowered, immediately perform another explosive repetition. Perform 10–12 repetitions.

Variation: Since some people have asymmetry in strength and power between their right and left legs, these movements can be performed one leg at a time.

References

Bean, J.F., et al. 2002. Weighted stair climbing in mobility-limited older people: A pilot study. Journal of the American Geriatrics Society, 50, 663–70.

Bean, J.F., et al. 2004. Increased velocity exercise specific to task (invest) training: A pilot study exploring effects on leg power, balance, and mobility in community-dwelling older women. Journal of the American Geriatrics Society, 52 (5), 799–804.

Fielding, R.A., et al. 2002. High-velocity resistance training increases skeletal muscle peak power in older women. Journal of the American Geriatrics Society, 50 (4), 655–62.

Hruda, K.V., Hicks, A.L., & McCartney, N. 2002. Training for muscle power in older adults: Effects on functional abilities. Canadian Journal of Applied Physiology, 28 (2), 178–89.

Iannuzzi-Sucich, M., Prestwood, K.M., & Kenny, A.M. 2002. Prevalence of sarcopenia and predictors of skeletal muscle mass in healthy, older men and women. Journals of Gerontology Series A: Biological and Medical Sciences, 57 (12), M772–77.

Keysor, J.J., & Jette, A.M. 2001. Have we oversold the benefit of late-life exercise? Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 56, M412–23.

Metter, E.J., et al. 1997. Age associated loss of power and strength in the upper extremities in women and men. Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 52A, B267–76.

Miszko, T.A., et al. 2003. Effect of strength and power training on physical function in community-dwelling older adults. Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 58A (2), 171–75.

Spirduso, W.W. 2005. Physical Dimensions of Aging ( 2nd ed.). Champaign, IL: Human Kinetics.

U.S. Administration on Aging. 2004. Older Americans 2004: Key indicators of well-being. www.aoa.gov/ default.htm; retrieved December 2004.

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About the Author

Cody Sipe, MS

Cody Sipe, MS IDEA Author/Presenter

Cody Sipe, MS, is the former director of the Ismail Center at Purdue University and is the 2005 IDEA Program Director of the Year. Certification: ACSM