Weigh the pros and cons of training with machines compared to free weights by using the following guidelines.

WHEN I WAS in eighth grade, I broke the school record for chin-ups. I still have the certificate of achievement from the school's principal proudly displayed on my wall. Heck, I still brag about the accomplishment to others. It doesn't matter that it was so many years ago, or that some tough kid has probably come along since to break my record. At the time, I had the strongest biceps and forearms in junior high. I used chin-ups to show off to the girls in class. My mother even bought a chin-up bar and attached it to my bedroom doorframe so I could train at home. I did chin-ups every day. What I learned from doing those hundreds of chin-ups is this: There is more than one way to train a muscle.

Have you ever had members who are intimidated by all the dumbbells, barbells and machines in your facility? You're not alone. If your clients have never lifted weights before, it can be daunting. And, with all of the different types of equipment and exercises, how do they know which to use for the best results? Both machines and free weights have their advantages and disadvantages. So which type of equipment is better? Here are some guidelines to follow, broken down into six categories: resistance, movement specificity, strength gains, workout flexibility, injury risk and cost.

Resistance

Weight machines. Weight machines use variable resistance, and change resistance throughout the range of motion. To accomplish this, weight machines have geometrically shaped cams integrated with a pulley system that change the length of the lever arm of the external weight (the perpendicular distance from the weight to the machine's axis of rotation). The cams are shaped such that, at weaker joint positions, the lever arm of the external weight is shorter, making it easier to lift the weight. At stronger joint positions, the lever arm of the external weight is longer, making it more difficult to lift the weight. Manipulating the lever arms, through which the external weight is applied, allows weight machines to place more stress on the muscles at the angles at which they are capable of producing greater forces. However, given the differences between the length of people's limbs and their ability to produce force at different joint angles, not all machines may be able to match their resistance to your clients' strength.

Free weights. With free weights, the resistance on the muscle remains constant throughout the joint's range of motion. When lifting a 5-pound dumbbell, it is 5 pounds at all parts of the lift: beginning, middle and end. Since there are points in a joint's range of motion at which the muscle is stronger, and points at which it is weaker, the amount of weight your clients can lift is limited by the weakest point. Free weights only serve as a strong-enough training stimulus for those weaker joint positions.

Advantage: Weight machines

Movement specificity

Weight machines. Most traditional weight machines allow only single-joint exercises, with movement occurring in a single plane. Since weight machines guide movement, they do not recruit muscles other than those specifically targeted by the machine. This apparent lack of freedom does confer one advantage: Weight machines allow lifters to isolate specific muscles or parts of muscles, which is of interest to bodybuilders and others who want to shape a specific body part.

Free weights. Movements using free weights occur in three dimensions. The added task of balancing free weights in the three-dimensional plane recruits ancillary muscles. However, the greater instability of free weights may require the need for a spotter, which would not be necessary when using weight machines. In contrast to weight machines, free weights allow lifters to perform multi-joint exercises and, thus, more closely mimic the activities of daily life and other specific activities for which your clients may want to train. Multi-joint movements also confer greater neural benefits in terms of acquiring specific skills. While multi-joint, free-weight exercises require a higher level of skill, and may take some time for your clients to learn, this slight disadvantage is more than compensated for by the gains in movement specificity.

Advantage: Free weights

Strength gains

Weight machines. Since the assessment of strength requires the use of either weight machines or free weights, the outcome of any experiment comparing the two types of weight training will likely favor the kind of training that uses the same type of equipment as the strength measurement. Studies testing strength (one-rep max) using equipment or a type of exercise different from that used in training have found similar gains in strength between weight machines and free weights.3, 4, 5

Free weights. Studies testing strength using equipment that is the same as that used in training have found a greater carryover of strength obtained from free weights to weight machines than the converse, and that training with free weights elicits superior strength gains compared to training with weight machines.1, 7, 8 The superior results of free weight training are likely due to their greater specificity of movement patterns, force application and velocity of movement.6

Advantage: Free weights

Workout flexibility

Weight machines. Weight machines do not provide much flexibility in designing or performing workouts. For example, while manufacturers of weight machines try to accommodate as many different body sizes as possible, there is still a limit as to how many adjustments can be made in the seat or arm settings, rendering the exercise to be performed in a relatively fixed position. Since each traditional weight machine is designed for a specific exercise, only the intended exercise can be performed with each machine. In addition, training progression is often problematic, as many weight machines are restricted to 10- to 20-pound increments.

Free weights. As their name implies, free weights do not limit the position of the exercise. Rather, they allow your clients to make adjustments in position based on their individual biomechanics. Unlike with weight machines, the number of exercises that can be performed with only a couple of dumbbells is nearly unlimited. Since dumbbells and barbell plates come in many different weights, free weights allow for small changes in training load. With free weights, lifters also have a greater opportunity to engage many large muscles. Exercise with many large muscles means a greater metabolic cost, which can have a greater effect on your clients' fitness and body composition.

Advantage: Free weights

Injury risk

Weight machines. Although injuries can occur when using weight machines, they are less likely, given weight machines' fixed positions and guided movements.

Free weights. Likely due to their free range of movement, training with free weights presents a greater injury risk compared to training with weight machines. Most weight-training injuries occur with intense or aggressive free weight training.2 However, if you monitor your clients during their workouts to make sure they are performing the exercises correctly, the risk of injury is no greater than when training with weight machines.

Slight advantage: Weight machines

Cost

Weight machines. From a management perspective, weight machines obviously represent a greater expense than free weights, including both their initial purchase and their maintenance. For a given cost, fewer people can be serviced at a given time with weight machines. Plus, you get a lot less for your money, with members only able to use the machine for one or two specific exercises.

Free weights. Free weights cost less to purchase than weight machines, and more people can be serviced at a single time for a given cost. Since there is more workout flexibility with free weights, you also get a lot more for your money.

Advantage: Free weights

Summary and recommendations

Despite the inability to alter their resistance at stronger joint angles, and the slightly greater risk of injury, free weights still have the overall strength-training advantage because of their training specificity, workout flexibility and superior stimulus for increasing strength. Possibly the most important reason for using free weights is that, while weight machines allow lifters to train muscle, free weights allow them to train movement.

Since the movements associated with weight machines are easier than those associated with free weights, clients who have never lifted weights should initially use machines to train their major muscles and general motor patterns. Once they have acquired a general strength base, it will be easier for them to move on to training more specific movements with free weights. Clients who are in rehab for an injury should also use machines rather than free weights to isolate the injured joint and prevent the possible exacerbation of an injury that can come with the added physical stress of handling free weights.

So next time one of your clients asks whether weight machines or free weights are better, weigh the pros and cons for that particular client. And if they use the right equipment, maybe they'll even be able to break my chin-up record.

REFERENCES

1. Boyer, B.T. A comparison of three strength training programs on women. Journal of Strength and Conditioning Research 4(3): 88-94, 1990.

2. Mazur, L.J., R.J. Yetman and W.L. Risser. Weight-training injuries. Common injuries and preventative methods. Sports Medicine 16(1): 57-63, 1993.

3. Messier, S.P,. and M.E. Dill. Alterations in strength and maximal oxygen uptake consequent to Nautilus circuit weight training. Research Quarterly 56: 345-351, 1985.

4. Saunders, M.T. A comparison of two methods of training on the development of muscular strength and endurance. Journal of Orthopedic and Sports Physical Therapy 210-213, 1980.

5. Silvester, L.J., C. Stiggins, C. McGown and G.R. Bryce. The effect of variable resistance and free-weight training programs on strength and vertical jump. National Strength Coaches Association Journal 3(6): 30-33, 1982.

6. Stone, M.H., D. Collins, S. Plisk, G. Haff and M.E. Stone. Training principles: Evaluation of modes and methods of resistance training. Strength and Conditioning Journal 22(3): 65-76, 2000.

7. Stone, M.H., R.L. Johnson and D.R. Carter. A short-term comparison of two different methods of resistance training on leg strength and power. Athletic Training 14: 158-160, 1979.

8. Wathen, D., and M. Shutes. A comparison of the effects of selected isotonic and isokinetic exercises, modalities, and programs on the acquisition of strength and power in collegiate football players. National Strength and Conditioning Association Journal 4: 40-42, 1982.