Benefits of resistance training Resistance training provides many benefits to obese individuals.7,11 Increases in the strength of the nervous system and muscular system are generally seen within the first few weeks of training, and increases in muscular size (hypertrophy) are generally seen after four to six weeks of training.7 Another benefit is cardiovascular. Peak oxygen consumption (VO2 max) either remains the same or increases slightly (3 to 4 percent) with non-circuit resistance training.2,11 Circuit training, in which exercises are conducted continuously with little or no rest, can result in VO2 max gains of 3 to 10 percent because of the high volume of work.11 Resistance training can also alter lipid profiles by increasing high density lipoprotein (HDL) levels in the blood and decreasing the total-cholesterol/HDL-cholesterol ratio. Total training volume plays a significant role in blood lipid profile changes.11 Another benefit of weight training is increased bone mineral content.7 Increased bone density reduces the risk of bone-related injuries due to osteoporosis, a degenerative loss of bone tissue typically seen in post-menopausal women. Exercise intensity and duration may affect the mineral content of bone. Obese individuals with high levels of body fat can also experience dramatic changes in body composition with resistance training. Increased levels of LBT increases physical function and strength. Body composition appears to be affected by training the larger muscle groups of the body, as larger muscle areas require an increased caloric cost. Total training volume appears to be another factor in altering body composition.7 Diet and resistance training Many studies have been conducted to determine the effect of diet and exercise on muscular strength, body composition and resting metabolic rate. Following are some of those findings.

Muscular strength. Decreasing caloric intake without exercise results in loss of LBT.4,6,8,10,12 Lean tissue loss can contribute up to 36 percent of total body weight lost as a result of dieting without exercise.10 With the accompanying loss of LBT from caloric restriction, a reduction in strength will also occur. One researcher looked at strength gains in obese females by creating two groups: an exercise-only group (EO) and a diet-plus-exercise group (DPE).3 The groups performed three sets of eight exercises for all of the major muscle groups. Both groups had a slight increase in LBT, but the increase was not statistically significant. The DPE group also had a significant reduction in body mass (5 percent) and fat mass (14 percent), while the EO group had no change. According to the authors, "Strength can improve in obese females who undergo moderate dietary restriction and body mass loss."3 These findings are similar to what other studies have concluded. Another study found a 22-percent increase in quadricep strength after the subjects underwent a strength program using their body weight instead of weight equipment for eight weeks.9

Body composition. Studies looking at the effect of diet and exercise on body composition typically show a reduction in fat mass and a slight reduction in or preservation of LBT. Twenty-one obese females were recruited for a study to look at muscle hypertrophy with weight loss.6 Each subject was either placed into a control group (C) or a weight-training group (WT). In addition to a controlled diet, the WT group performed eight exercises that used all of the major muscles. Each exercise was performed with low to medium repetitions (four to eight) and three to four sets, depending on the week. Both groups lost a significant amount of body weight (16.2 percent and 16.8 percent for the C and WT group, respectively). Cross sectional fiber area had a significant change for the WT group while the C group had no change. These results show that hypertrophy can be possible "during periods of severe energy restriction concurrent with declines of body weight and LBT."6 Another study looked at lean body weight maintenance during caloric restriction.4 Subjects were placed into one of four groups: control (C), diet only (D), diet plus exercise (DE) and exercise only (EO). Increases in LBT were seen in the DPE and EO groups, leading the authors to believe that muscle hypertrophy is possible during caloric restriction.4

Resting metabolic rate. Studies have also looked at the effect that exercise and diet have on resting metabolic rate (RMR), which is associated with lean body tissue. Each pound of muscle consumes approximately 35 Calories per day, so increasing an individual's LBT should increase RMR, while decreasing caloric intake to reduce overall body mass will cause RMR to decline. Twenty-three subjects participated in a study in which aerobic exercise was combined with weight training and a very-low-calorie diet to see the effect on resting metabolic rate.12 There were three groups: a control group (C), a moderate-amount exercise group (MA) and a large-amount exercise group (LA). The moderate group participated in a walking program three days per week and a resistance training program three days per week. The LA group walked five days per week and lifted three days per week. The resistance training program consisted of two to three sets with six to eight reps of bench press, lateral pulldown, knee extension and knee flexion. RMR decreased significantly for the C and LA groups but not the MA group. Since the diet was very low calorie, lean body tissue lost during the study was similar between the C, MA and LA groups. However, strength increased significantly in the MA and LA groups, leading the researchers to believe that while "weight training during moderate energy restriction increases LBT, weight training does not appear to enhance retention of LBT during a very-low-calorie diet."12

Another study looked at the effects of either high-intensity resistance training or endurance training on metabolic rate.5 Sixty-four subjects volunteered for the study and were placed in one of three groups: a control group (C), a resistance-training group (RT) and an endurance-training group (ET). The RT group participated in a combination of free weights and weight machines four days per week. Eleven exercises were performed and were split into upper body exercises (Monday and Thursday) and lower body exercises (Tuesday and Friday). Subjects started off with three sets of 10 to 12 reps for the first two weeks of the study, and then performed a pyramid progression of weight and reps for the remainder of the study. The ET group participated in a walk/jog program four days a week. Intensity and duration were gradually increased and a new goal was established every four weeks. Results showed that RMR did not significantly change between groups during this study. RMR increased slightly in the RT and ET groups, but not significantly; RMR only increased 3.3 percent in the RT group. It appears that weight training may play an important role in maintaining or increasing an individual's RMR when in a state of negative energy balance.5

Preparing for an exercise program

Before beginning an exercise program, obese clients should have medical clearance from their primary care physician. Once the client has been medically cleared, an initial assessment should take place between the trainer and client. This assessment should address any medical concerns the client may have, such as diabetes and blood pressure, and any orthopedic concerns (joint problems, lower back pain, pulled muscles, etc.). A complete exercise history should also be noted. The exercise history can give the trainer feedback on clients' likes and dislikes. Goal setting should also be discussed. Helping obese clients set appropriate goals can increase their participation in physical activity. Once a goal has been met, set another goal that is also attainable within a reasonable time frame.

Resistance-training guidelines

Beginning a resistance-training program can be very intimidating for an obese individual. Trainers need to be careful not to overwhelm clients with numerous exercises, and should design a resistance-training program that maintains or increases lean body tissue, muscular strength and muscular endurance. A minimum of six to eight exercises emphasizing the major muscle groups of the body (back, chest, legs, shoulders, abdominals, low back) should be performed two to three days per week, and a minimum of one set of 12 to 15 repetitions to near fatigue should be completed. Strengthening these muscle groups will provide a solid foundation for clients to build upon.

Choosing a mode of resistance training will be determined largely by clients' preferences. While a variety of modes can be used to build strength and increase LBT, weight machines are generally used in a health club setting. Weight machines allow obese clients to have back support and control of the weight. Free weights, resistance tubes, body weight exercises and stability balls also provide the muscles with an adequate stimulus to build strength and muscle mass. Exercises with these devices, called functional exercises, also allow the body to stabilize and balance itself, and mimic daily activities.

Whichever mode is decided upon, proper technique, including speed of movement and body positioning, must be taught to reduce the chances of injury. Providing clients with feedback on their technique will reinforce the learning curve associated with resistance training.

Weight training is generally believed to enhance flexibility.11 Increasing joint flexibility may reduce injuries and increase performance.11 Therefore, exercises should be performed through a full range of motion. Individuals with orthopedic complications are exempt from this guideline.

While resistance training is a vital component to maintaining or increasing overall fitness, an exercise program should also incorporate aerobic-type activities and flexibility training. The addition of these activities will create a well-rounded program to help obese individuals increase their physical function.

REFERENCES

1. American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Exercise Prescription. Williams and Wilkins: Baltimore, Md., 1995.

2. ACSM. The recommended quantity and quality for developing and maintaining cardiorespiratory and muscular fitness and flexibility in healthy adults. Medicine and Science in Sports and Exercise 30(6): 975-991, 1998

3. Ballor, D.L., and V.L. Katch. Strength gains in obese females are unaffected by moderate dietary restriction. European Journal of Applied Physiology 59: 351-354, 1989.

4. Ballor, D.L., V.L. Katch, M.D. Becque and C.R. Marks. Resistance weight training during caloric restriction enhances lean body weight maintenance. American Journal of Clinical Nutrition 47: 19-25, 1988.

5. Broeder, C.E., C.E. Burrhus, L.S. Svanevik and J.H. Wilmore. The effects of either high intensity resistance or endurance training on metabolic rate. American Journal of Clinical Nutrition 55: 802-810, 1992.

6. Donnelly, J.E., T. Sharp, J. Houmard, M.G. Carlson and J. Hill. Muscle hypertrophy with large scale weight loss and resistance training. American Journal of Clinical Nutrition 58: 561-565, 1993

7. Fleck, S.J., and W.J. Kraemer. Resistance training: Physiological responses and adaptations. The Physician and Sports Medicine 16: 108-124, 1988.

8. Geliebter, A., M.M. Maher, L. Gerace, B. Gutin, S.B. Heymsfield and Hashin. Effect of strength or aerobic training on body composition, resting metabolic rate and peak oxygen consumption in obese dieting subjects. American Journal of Clinical Nutrition 66: 557-563, 1997.

9. Katch, F.I., and S.S. Drumm. Effects of different modes of strength training on body composition and anthropometry. Clinics in Sports Medicine 5: 413-459, 1986.

10. Pavlov, K.N., W.P. Steffer, R.H. Lerman and B.A. Burrows. Effects of dieting and exercising on lean body mass, oxygen uptake and strength. Medicine and Science in Sports and Exercise 17(4): 466-471, 1985

11. Stone, M.H., S.J. Fleck, N.T. Triplett and W.J. Kraemer. Health and performance benefits of resistance training. Sports Medicine 11: 210-231, 1991.

12. Whatley, J.E., W.J. Gillepsie, J. Honig, M.J. Walsh, A.L. Blackburn and G.I. Blackburn. Does the amount of endurance exercise in combination with weight training and a very low energy diet affect resting metabolic rate and body composition? American Journal of Clinical Nutrition 59: 1088-1092, 1994.

By David Radin

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Some people may overeat to relieve emotional stress. These people may gain a significant amount of weight, more than 20 or 30pounds in a year.

Many people with special needs are afraid to start a strength training program; they often feel as if it is too tough or dangerous for them to start strenuous activity. It is important for fitness professionals to promote the benefits and necessity of strength training for all groups, healthy or otherwise.