This week I was asked a question that certainly comes up from time to time; which is better, machines or free weights? The answer really depends on what the intention of the exercise is. Both forms of resistance training have a lot to offer and can be a beneficial part of many training plans. Let's take a look at some key features of each.
Features of Exercise Machines
Before we can properly discuss the features of exercise machines it's important to make a few small clarifications about just what we're talking about. A wide variety of exercise machines exist ranging from cardio equipment such as treadmills and ellipticals to resistance machines like the leg press or even to free cable pulley resistance stations. For the purpose of this discussion we'll be focusing on machines that guide the movement such as a seated row, or leg press and so on. Cardio equipment is great, but comparing it to free weights is a discussion for another day. Cable pulley stations are actually a lot more similar to free weights than to other machines so they will also not be included in this analysis.
Safety: Guided Movement
Machines offer a certain safety profile by being exercises that have a shallow learning curve and do not require high skill to perform. This feature is largely due to the nature of the machines guiding the movement path to minimize unwanted movement. However, this same feature can also lead to an increased potential risk of repetitive strain injuries because there is less freedom for the body to make subtle adjustments in position throughout the exercise.
One really useful feature that many machines have to offer is accommodating resistance. What this means is that as leverage changes throughout the exercise, so does the force required to more accurately match the force curve of the movement. This helps to avoid sticking points (really hard parts of the movement) and dead spots where the muscles being targeted aren't really doing much work.
Most of these exercise machines are designed with a specific muscle group in mind, and an exercise to target said muscle group. This can be particularly helpful with individuals who have motor control problems to help them target muscles that they otherwise find ways to avoid by compensating with other movements. For instance I've come across individuals with conditions such as cerebral palsy who really struggle with the body awareness to call on the biceps to do a curl with a free weight, they'll find any number of ways to move the weight, but none of them effectively targeting the desired muscles. However, if they are locked into a machine designed to isolate the biceps (and other elbow flexors) than they can target the muscles successfully.
Another feature of exercise machines is that they offer a great deal of stability. This feature is important for the machine to be able to effectively isolate and guide movement as mentioned above and is advantageous for working muscles to extreme levels of fatigue without the stabilizing muscles giving out causing the loss of form. However, this can also be a draw back because not only do the stabilizing muscles not get worked as effectively, but the motor pattern being developed is not calling on them. A motor pattern is essentially like a program your brain uses when calling for certain actions, if a particular movement is repeated frequently enough it can lead to changes in the motor pattern programming which in this case could potentially lead to movements where the powerful prime mover muscles get called into action without the stabilizers to offer support. This could be a real problem when not locked into the stability of the exercise machine.
Non Gravity Dependent
Because machines are able to make use of variable leverage, pulleys and gears they are capable of allowing exercises in directions that are not gravity dependent. This can be useful not only for working a variety of angles that are more difficult when forced to use the vertical line of pull of gravity, but also for taking body weight out of the equation. Take for example, an individual who is severely overweight and requires a walker or wheelchair. This person isn't going to be successful with a gravity dependent exercise like the squat or lunge, but will be able to improve strength with leg presses, leg extensions and hamstring curls by setting an appropriate load.
Features of Free Weights
Free weights can refer to any number of items that can be lifted and moved around , but most often refer to certain equipment types such as dumbbells, barbells, kettlebells, and so on.
Versatility and Freedom
When using free weights the possible exercise choices are nearly limitless. Unlike machines that are developed with one or two specific exercises in mind, free weights are really nothing more than something to be lifted in any way that allows gravity to work on them. For instance with a single pair of dumbbells a person can get a total body workout.
Functionality, Specificity and Carry-over
Since free weights are so versatile they can often be used in exercises that more closely approximate those encountered in day to day life or sport than is commonly seen with machines. Because the body adapts specifically to the demands which are imposed on it, the more closely an exercise matches the movement and strength requirements of a given activity, the more the strength and power developed from that exercise can be expressed in a given activity.
An example of this would be an exercise such as a forward lunge while lifting dumbbells which would have more carry-over to picking up a small child than an exercise like the leg press which involves sitting in a machine while pushing a resisted platform away form the body with the legs. While this last exercise would strengthen the legs, it doesn't coordinate the movement with picking up an object while simultaneously moving the whole body through space. Thus it doesn't use all of the same muscles, and even if exercises were added it which do use the muscles, the nervous system will not be trained to be as efficient in the motor pattern used to pick up a child.
Gravity Dependent: Vertical Resistance Only
As briefly pointed out above, free weights rely on gravity which pulls straight down to the ground in order to provide their resistance. This can limit the angles which can be used to a certain extent.
Compared to machines free weights can make for much less stable exercises. This leads to greater recruitment of stabilizing muscles to allow for proper form and safe movement. This is thought to lead to greater safety in the full expression of power in other activities. So it's an interesting trade-off where a little more risk is involved during the exercise due to less stability, but this increases the bodies ability to stabilize itself leading to increased safety outside the gym.
Being the simple tools that they are, free weights have no way of altering the load throughout an exercise. This means that as joint angles change which alters the leverage at the joints that sticking points and dead spots are very much a reality.
So Which is Better?
While I have a bias toward free weights, I have to say that neither is better across the board. Both machines and free weights have lots to offer and surpass each-other in various ways. Understanding the features listed above can help to determine which method of training is better for a given goal.
Also keep in mind that by combining the use of multiple methods the advantages of each can be incorporated. For example, a football player may be required to put on weight and doing free weight exercises will be useful for building some solid muscle and functional movement. Adding some machine based work on top of the free weights could allow this athlete to do a higher volume of work after the stabilizers are spent, which is thought by many to be a highly effective way to increase muscle growth. This is a win-win because the motor programming is taking place during the free weight activities to call on the stabilizers and develop functional movements and then the stability and isolation of the machines is used to get further development that might not otherwise be terribly safe.