But when talking about sports performance it's important to consider which of the two are most effective for maximizing athletic potential. We must understand the scientific research related to machine versus free-weight resistance training so we can apply this in the practical setting. So while not becoming too scientific, we will run down the basic differences between machines and free weights.
1. Free weight training is more specific to sports when compared to machines.
Exercises that include free weights are typically ground-based. They are performed with the feet on the ground because that's how many sports are played, on the ground! You can name several: football, baseball, soccer, volleyball, etc. Ever hear something like "play like you train"?
2. Ground-based free weight training creates more muscle activation when compared to machines.
This is primarily due to the nature of ground-based free weight training. It requires balance and stabilization that we don't get from machines. Take the leg-extension machine, for example. The prime mover of this exercise would be the quadriceps group. Now consider a free-weight alternative such as the step-up. Not only would we get activation of the quadriceps, but we also get activation of the surrounding muscles at the hip such and even the hamstrings to a fair degree.
3. Free weight training is a better osteogenic stimulus.
Osteogenic means bone-creating, and free weight training promotes it better when compared to machines. Consider again that most free weight training includes ground-based exercises. These exercises provide a compressive force upon the bones. When the compressive force is great enough, it stimulates the formation of additional bone mineral content. Stronger bones equals a stronger body.
4. Free weight training allows us to train movement rather than just the muscle.
This goes back to the first point on specificity. Athletes perform movements on the field that are multi-joint, so it makes sense that we don't want to train only in a single-joint fashion that many machines offer. Free weight training allows athletes to focus on sports-specific movements with their body that can best prepare them for superior performance on the athletic field.
5. Machines have purposes for beginners and athletes rehabilitating.
We just highlighted the benefits that free weights have over machines. One benefit that machines have, however, is their ability to develop beginners and rehabilitating athletes. It is not wise to throw athletes who are new to strength and conditioning or are recovering from an injury into the same workouts as their veteran counterparts. Their bodies need preparation and recovery. As such, machines may be an excellent choice because they allow the athlete to focus on a specific muscle or action to repair tissue or build a basic foundation of muscle strength. After a period of time, we must progress athletes into more challenging exercises, and the integral component of this involves the transition from machine to free weight exercises.