Preface: Usually exercises divided into two categories:

• Compound exercises work several muscle groups at once, and include movement around two or more joints. For example, in the leg press movement occurs around the hip, knee and ankle joints.
• Isolation exercises are the ones where the movement is restricted to one joint and one muscle group. For example, the leg extension is an isolation exercise for the quadriceps.

Note: for more information regarding exercise types see: http://en.wikipedia.org/wiki/Weight_training#Types_of_exercises.

As we seen in number of sets section, in most cases 1-6 sets per muscle group would be enough. Hence, if even one set can be enough than training a muscle group with more than one exercise might seem useless. But, working different exercises (either during a workout session or changing exercises over time) used for different muscle’s head training.

What’s better: compound or isolation exercises?

Compound exercises are preferable over isolation ones for two main reasons:

• Compound exercises involve more muscles in each repetition. As result, there is higher probability to cause micro injuries[^1]. Additionally, less overall work needs to be done.
• Safety. Usually, there are lower chances to get injured when a compound exercise is committed (compared to an isolation one).

Are free weight exercises favored over their machine siblings?

There are two things to consider while answering this question

• Drag force – as explained in movement analyze during eccentric phase our muscle are stronger. Most training machines are bases over a system of blocks, in which drag force can be rather high. As result, the positive phase will be hardened and the negative one eased, causes the average set’s intensity to decrease. Thus, when there is drag force (that can be felt) free weights are preferred.
• Safety and convenience. Many training machines are inconvenient and/or can cause injuries. Therefore I’d recommend trying out a new machine with a “small” weight. Over the next few weeks increase the weight using small steps till you reach your max. If any discomfort was felt during these several weeks or after the last workout using this machine than it shouldn’t be used (of course this is true if the machine was used properly). Additionally you might find out that some machines are great in the initial stage of your training, but as your training weights grow, they become uncomfortable.

In conclusion, machines should be preferred by beginners and as diversity tool for free weights in later stages.

Note: different training techniques might have their own constrains. For example: it’s almost impossible to train using super slow methods with free weights.

[^1]For more information see: muscle damage theory.