Re sist ance Tra inin g fo r He alth *

Mi chae l L. Pol lock , Ke vin R. V ince nt

UNI VERS ITY OF FLO RIDA 

ORIGINALLY PUBLISHED AS SERIES 2, NUMBER 8, OF THE PCPFS RESEARCH DIGEST.

*Since publication of this issue of the Research Digest on “Resistant Training for Health,” the American College

of Sports Medicine has accepted for publication in their journal Medicine and Science in Sports and Exercise the

publication of a symposium issue on Resistance Training for Health and Disease edited by Michael Pollock,

Ph.D., and William Evans, Ph.D. This issue will highlight the effect of resistance on bone density, body

composition, and function of the elderly, low-back pain and disability, acute responses to resistance training and

safety, and finally, a prescription of resistance training for health and disease. These timely papers will

supplement this Research Digest topic.

HI GHLI GHT

“A d d in g st ren g t h t r a in i n g t o a p r ogra m of re gu la r p h ysic a l

a c t ivi t y wi ll h e lp t o d e crea se t h e ri sk of ‘c h ron ic d i sea s es’ wh ile

im p rov in g qu a lit y of li fe a n d fu n ct i on a l it y, a l lowi n g p e op le of 

a l l a g es t o im p rov e a n d m a in t a in t h eir h e a lt h a n d in d ep e n d en t

li fest yle. ”

IN TROD UCTI ON

Increasing physical activity and participation in an aerobic endurance exercise program have

been shown to decrease the risk of chronic diseases (e.g., coronary heart disease [CHD],

stroke, osteoporosis, diabetes, obesity/weight control), which have become the leading causes

of morbidity and mortality in the United States. The American Heart Association (AHA) has

identified physical inactivity as a primary risk factor for the development of CHD along with

cigarette smoking, high blood pressure, and elevated levels of cholesterol. As an intervention,

the American College of Sports Medicine (ACSM), the AHA, and the Surgeon General’s

Report on Physical Activity and Health all have established guidelines for aerobic exercise

programs designed to positively affect health status. These recommendations are based on a

preponderance of evidence establishing the effect of exercise on disease prevention (see

Figure 14.1).
The effects of resistive type exercise (strength training) on health status have been largely

overlooked. Traditionally, strength training has been seen as a means of improving muscular

strength and endurance (muscle mass) and power, but not as a means for improving health.

There is increasing evidence that strength training plays a significant role in many health

factors (see Figure 14.1). The ACSM (1990, 1995), AHA (1995), and the Surgeon General’s

Report on Physical Activity and Health (1996) all have recognized the importance of strength

training as an important component of health. These organizations have recommended

performing 1 set of 8–12 repetitions of 8–10 exercises 2–3 times per week for persons under

50 years of age and the same regimen using 10–15 repetitions for persons over 50 years of

age. The research and rationale for this exercise prescription have been reviewed (ACSM,

1990; Pollock et al., 1994; Feigenbaum & Pollock, 1997). Although greater intensity (fewer

repetitions and greater weight) with multiple sets can elicit greater improvements in strength

and power, it may not be appropriate for older nonathletic participants. A regimen of 8–12 or

10–15 repetitions appears to be an adequate balance for developing both muscular strength

and endurance. The research suggests that 80–90% of the strength gains can be elicited using

this regimen compared to the high volume types of programs. Thus, because time is an

important factor for program compliance, the above recommended guidelines seem

appropriate. Although more research is necessary to confirm the best combination of

intensity (repetitions, weight, sets) for older or more fragile participants, it appears that the

10–15 repetition guideline may create less joint stress and injury than the 8–12 repetition

program.

FI GURE 1 4 . 1

Comparison of the effects of aerobic endurance training to strengthen

training on health and fitness variables.

Ae r obi c Re si st ance Va r i ab l e Ex er ci se

Ex er ci se

Bo ne m iner al d ensi ty ↑↑ ↑↑ 

Bo dy c ompo siti on

%f at ↓↓ ↓

LB M ↔ ↑↑ 

St reng th ↔ ↑↑ ↑

Gl ucos e me tabo lism 

In suli n re spon se t o ↓↓ ↓↓ gl ucos e ch alle nge

Ba sal insu lin leve ls ↓ ↓

In suli n se nsit ivit y ↑↑ ↑↑ 

Se rum lipi ds

HD L ↑↑ ↑↔ 

LD L ↓↓ ↓↔ 

Re stin g he art rate ↓↓ ↔

St roke vol ume ↑↑ ↔

Bl ood pres sure at rest 

Sy stol ic ↓↓ ↔

Di asto lic ↓↓ ↓↔ 

VO 2ma x ↑↑ ↑ ↑

En dura nce time ↑↑ ↑ ↑↑ 
Ph ysic al f unct ion ↑↑ ↑↑ ↑

Ba sal meta boli sm ↑ ↑↑ 

Improving muscular strength has been traditionally viewed as important for athletes,

competitive weightlifters, and bodybuilders, but not for improving health status. Recent

evidence indicates that this conception is no longer true. In this paper we will provide

information concerning how strength training can influence health and disease prevention.

IM PROV EMEN TS I N ST RENG TH A ND F UNCT ION

Aging has been associated with a decrease in muscle mass and strength (Larsson et al., 1979).

This decrease in strength is linked to decreased mobility, decreased functionality, and

increased risk of falling in older people (Bendall et al., 1989; Fiatarone & Evans, 1990). Falls

have been identified as the most frequent cause of injury-related mortality in the elderly (Fife

et al., 1984). According to Greenspan et al. (1994), 90% of all hip fractures in the elderly

occur as a result of a fall. The authors also suggested that to help prevent the risk of falling,

interventions should include exercise designed to improve quadriceps strength,

neuromuscular function, and gait. Nevitt et al. (1991) conducted a prospective study to

determine the risk factors that lead to injurious falls in the elderly. They reported that the

fallers’ ability to protect him- or herself during the fall affected the risk of injury. Upper and

lower extremity strength, reaction time, and time to complete a cognitive test were associated

with risk of falling and injury. The authors recommended that interventions intended to

reduce the risk of falling and injury should include strength training and exercise. Fiatarone

et al. (1994) examined the effect of 10 weeks of resistance exercise for the legs only on

muscle strength and function in elderly adults (mean age, 87± 0.6 yr). Resistance exercise

increased muscle strength (113%), gait velocity (12%), stair climbing power (28%). Fiatarone

et al. (1990) reported that eight weeks of resistance exercise for the legs improved strength

and function in nonagenarians (mean age 90±1 yr). Quadriceps strength improved 174% and

tandem gait speed increased 48% following resistance training.

The Surgeon General’s Report on Physical Activity and Health stated that developing

muscular strength can improve one’s ability to perform tasks and reduce the risk of injury.

The report goes on to say that “resistance training may contribute to better balance,

coordination, and agility that may help prevent falls in the elderly.”

LO W BA CK P AIN AND STRE NGTH 

Low back pain and spinal disorders are the predominant reason for disability in the

workforce. It is estimated that chronic low back pain accounts for nearly 80% of the annual

cost of low back disorders even though this classification represents only 10% of all spinal

disorders (Spengler et al., 1986). Lack of lumbar strength has been associated with the

development of low back pain and dysfunction.
Russell et al. (1990) reported increased lumbar strength and decreased low back pain

following eight weeks of isolated lumbar extension exercise in subjects with chronic low back

pain. Risch et al. (1993) examined the effect of 10 weeks of lumbar extension exercise on

patients with chronic low back and reported decreased low back pain, physical and

psychosocial dysfunction. The results also showed a significant improvement in lumbar

extension strength. Nelson et al. (1995) examined the effect of isolated lumbar extension

exercise on 895 chronic low back pain patients who had failed an average of six other

treatment modalities prior to enrolling in the study. The patients performed lumbar extension

and torso rotation exercise for 10 weeks. The results showed that most of the patients

increased low back strength, decreased low back and leg pain, and improved their ability to

perform daily activities. Seventy-two percent were able to return to work.

Some evidence is also available suggesting that improving low back strength is effective in

reducing the incidence of low back dysfunction in the work place. Mooney et al. (1995)

reported that the prevalence of low back injuries was reduced at a coal mine following a

program of 20 weeks of lumbar extension exercise.

BO NE M INER AL D ENSI TY

Osteoporosis is a degenerative disease that is characterized by a decrease in bone mineral

density (BMD). This loss makes the bones more susceptible to fractures. These fractures can

lead to decreased physical activity and possibly increased susceptibility to further health

problems and mortality. Research has indicated that bone formation can be stimulated by

placing a strain on the bone as is seen during resistive and aerobic exercise (Rubin & Lanyon,

1984). Although both forms of exercise can increase BMD, the increase is site-specific to the

joints exercised. Hamdy et al. (1994) reported higher BMD in the upper arm in persons who

weight trained compared to runners, but that there was no difference for lower body BMD

between the two groups. Karlsson et al. (1993) reported that active and retired weightlifters

had higher BMD for the spine, hip, tibia, and forearm when compared to controls. In a

comparison of BMD between female weightlifters, cyclists, cross-country skiers, and

orienteers, Heinonen et al. (1993) reported that the weightlifters had the highest weight

adjusted BMD in the distal radius, lumbar spine, distal femur, and patella. Snow-Harter et al.

(1992) showed that eight months of either resistance exercise or jogging improved lumbar

BMD when compared to controls, but no difference was seen between the exercise groups.

Braith et al. (1996) examined the effects of six months of resistance exercise on BMD

following heart transplant surgery. Typically, BMD decreases during the post-operative

period as a consequence of glucocorticoid therapy. The group that performed strength

training for six months was able to return their lumbar, total body, and femoral neck BMD to

near baseline levels while the non-strength-training groups’ BMD remained depressed.

Pollock et al. (1992) showed that six months of isolated lumbar training improved lumbar

BMD compared to controls in men and women 60 to 79 years of age. Menkes et al. (1993)

reported a significant increase in femoral neck BMD in middle-aged to older men following

16 weeks of strength training. These data indicate that resistance and aerobic exercise can

both positively affect BMD, but that this influence is site-specific to the mode of exercise.
AE ROBI C CA PACI TY

Exercise programs that emphasize endurance exercise usually elicit a 15–30% increase in

maximum oxygen uptake (VO2max). Available evidence indicates that traditional weight

training (greater than 1–2 minutes rest between exercises) does not increase VO2max

(Pollock & Wilmore, 1990). However, it has been shown that performing circuit training

regimens can increase VO2max 5–8%. These regimens consist of a circuit of approximately

10 exercises. A weight is chosen that can be lifted for 15 repetitions for each exercise with a

short (15–30 second) rest period between exercises. Thus, circuit weight training has only a

modest effect on VO2max and should not be used for that sole purpose. Although weight

training has only a modest effect on VO2max, it has a dramatic effect on strength, endurance,

and physical function. For example, Hickson et al. (1980) found that strength training the

legs for 10 weeks improved performance time on both a treadmill (12%) and a stationary

cycle (47%), while VO2max only increased 4%. Ades et al. (1996) reported that 12 weeks of

strength training improved submaximal treadmill walking time by 38% while no change was

reported for controls.

BO DY C OMPO SITI ON

Obesity is a risk factor for several health problems including diabetes mellitus, arthritis,

cardiovascular disease (CVD), and kidney dysfunction (Stone et al., 1991). Also, due to

excess nonmetabolically active weight, an obese person has to expend more energy for

movement placing increased stress on the cardiovascular system. Aerobic exercise has been

widely prescribed and utilized as a means of weight control and fat loss. There is also

evidence indicating that strength exercise is an effective means of influencing body

composition. Gettman and Pollock (1981) summarized the effects of five weight training and

six circuit weight training studies on changes in body composition. The studies showed a

mean decrease in body weight of 0.12kg, increase in lean body mass of 1.5kg, and a decrease

in fat mass of 1.7kg.

The added benefit of strength training to an aerobic exercise program (caloric

expenditure) is its effect on developing and maintaining muscle mass and metabolic rate.

Metabolic rate decreases with age and a primary factor influencing this decrease is reduced

fat-free mass. Campbell et al. (1995) reported that resting metabolic rate and energy intake

required to maintain body weight significantly increased in older adults following 12 weeks

of strength training. These data are in agreement with Pratley et al. (1994). Thus it appears

that resistance exercise should be a part of a well-rounded program including aerobic

endurance exercise for weight loss and controlling weight with age.

EF FECT ON CARD IOVA SCUL AR R ISK FACT ORS

There is growing evidence to indicate that strength training may also be important to risk

factor intervention. Strength training exercise has been shown to increase insulin sensitivity,

decrease glucose intolerance, and has a modest effect on decreasing diastolic blood pressure

and may alter serum lipids.
Miller et al. (1984) reported that 10 weeks of strength training significantly reduced basal

insulin levels and area under the insulin response curve following glucose ingestion. The

decrease in insulin was significantly correlated with increase in lean body mass. Hurley et al.

(1987) reported that insulin response to an oral glucose tolerance test was significantly lower

following 16 weeks of resistance training. Smutok et al. (1993) compared the effect of

endurance and strength training on responses to a glucose tolerance test. Both modalities

decreased the total area under the curve for glucose levels and insulin response, and there was

no difference between the two types of exercise.

Aerobic endurance exercise has been well established as a means for favorably altering

high density lipoprotein cholesterol (HDL-C). The research concerning the effect of strength

training is not as clear and recent studies have produced conflicting results. Studies that do

show a positive result, typically involve higher volumes emphasizing multisegment exercises.

Hurley et al. (1987) reported a 13% increase in HDL cholesterol following 16 weeks of heavy

strength training. Wallace et al. (1989), and Johnson et al. (1982) both reported positive

changes in lipid profiles, but only during the highest volumes of training. Goldberg et al.

(1984) showed that a program emphasizing high volume with short rest periods increased

HDL while decreasing LDL and serum triglycerides. Conversely, Kokkinos et al. (1987,

1991), Kohl et al. (1992), and Smutok et al. (1993) all reported that strength training did not

significantly alter serum lipid profiles. Thus, the available evidence seems to indicate that the

type of exercise performed by average strength trainers may not be sufficient to impact

serum lipids.

SA FETY AND PRA CTIC AL A PPLI CATI ON

Data regarding the safety of strength training and testing show that it is safe if proper

guidelines are followed. Gordon et al. (1995) reported no adverse cardiovascular events

following maximal strength testing in 6,653 healthy men and women. Other studies have

shown no excess incidence of cardiovascular events using resistance training compared to

aerobic endurance training in varied populations. Muscle soreness is common in beginning

exercisers but significant musculoskeletal injuries are rare. Persons with previous joint injuries

are at higher risk for sustaining an injury from strength training.

An important reason why strength training is beneficial in daily life and may cause less

risk in doing various lifting tasks is related to the training effect. For example, McCartney et

al. (1993) showed that following 12 weeks of leg press training, maximal strength increased

24%, and that blood pressure measured during submaximal lifting decreased following the

training period. Thus, strength training can decrease the stress placed on the heart during

lifting tasks such as carrying groceries, snow shoveling, and lifting moderate to heavy boxes,

which have been implicated as a cause of heart attacks.
C ON CL US IO N

The effects of resistance/strength training on muscular strength and endurance (muscle mass)

and rehabilitation from musculoskeletal injury is well known. As a result, most of the major

health organizations have included it as an important component of a well-rounded exercise

program along with aerobic endurance and flexibility exercise. More recently, strength

training has been shown to be beneficial in improving many factors associated with good

health. These factors include increased function and prevention of falls, decreased pain in

chronic low back pain patients, improved glucose tolerance and insulin sensitivity, increased

BMD, increased basal metabolic rate (weight control), and improved quality of life. Added

long-term epidemiological studies are necessary to confirm these findings. It appears that

most of the above findings can be attained in strength training programs that include 8–10

exercises that are performed 2–3 days per week, using 1 set of 8–15 repetitions to fatigue.

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