Beginners as well as experts can benefit from machines as much as from free weights.
Each has its advantages and disadvantages, but as a trainer I strongly recommend that you include free weights to your training routine. Why? Because training with barbells and dumbbells allows us to work coordination, balance, and muscular strength (1). Once we have improved these three physical abilities, we become more proficient in sports as well as daily activities. The desire to move then comes more naturally. We must also not forget all the other benefits related to regular exercise, such as better health and weight management.
Chart of advantages and disadvantages
Advantages
Disadvantages
Free weights
Can reproduce sports moves and daily movements
Many possible movements and variations, which brings variety to your training
Less expensive, can easily be used at home
Work stabiliser muscles
More complete and balanced muscular work
Increase strength gains (1)
Improve balance and coordination (1)
Usually quick and easy to use
More possibilities of “cheating”
Higher risks of injury and poor movement execution
Require more practice, coordination, and balance to master
Often require more supervising or help from a partner
Machines
Safe when used correctly
Suitable for beginners (the movement is guided by the machine to be correctly performed)
Require less practice and supervision
Can isolate working muscles, which is useful to correct a specific weakness
Cables, automated and compressed air machines (Keiser) are quick and simple to use
With compressed air machines (Keiser), the weight is hidden from other people, giving more privacy to the user
Not adapted to very small or very tall people
Usually can’t reproduce sports moves or daily movements
Less possible variations (monotony in the long term)
Don’t work stabiliser muscles
An often isolated muscular work can lead to neglect of other important muscles
Some very popular machines can be used so often that is becomes hard to use them during your training
References: 1. Spennewyn KC (2008). Strength outcomes in fixed versus free-form resistance equipment. J Strength Cond Res. 22(1):75-81.