Mechanical overload is the amount of physical force placed on a muscle and is essential for stimulating muscle growth. Compound barbell lifts require optimal range-of-motion from a number of joints. If one of those joints does not function properly, it could cause an injury. Because exercise machines control the path of motion and place the greatest amount of force where a muscle is the strongest, it can be a safe way to apply the overload necessary to stimulate muscle growth.

There are two components of muscle: the elastic component of fascia and the connective tissue responsible for providing shape and transmitting forces from one section of muscle to another, and the contractile element of the actin and myosin protein filaments responsible for controlling muscle contractions. Improving muscle size and strength requires using external resistance to stimulate the contractile element to become capable of generating higher levels of force. Machine training can be extremely effective for achieving this outcome.

Metabolic overload occurs when a muscle is required to work to a point of momentary fatigue and does not have the energy to generate another contraction. Muscle growth occurs either as a result of mechanical or metabolic overload. A long-time bodybuilding secret for achieving rapid muscle growth is the use of drop sets, which involves doing an exercise to the point of momentary fatigue, immediately lowering (dropping) the weight, and then continuing to the next point of exhaustion. Machines provide the safest and most time-efficient means of being able to perform drop sets to the point of complete fatigue, which ensures that all fibers in a particular muscle have been engaged.

Circuit training requires transitioning from one exercise to another with a minimal amount of rest and can be effective for creating both a mechanical and metabolic overload for your clients. You might design circuits featuring barbells, kettlebells and weight sleds and encourage your clients to work to the point of fatigue. However, it can be intimidating for clients to use this equipment on their own. The solution is to design a machine-based circuit for your clients to follow when you’re not working directly with you, which allows them to experience the benefits of circuit training without the need to know how to properly use advanced equipment.

In addition to the many health benefits of strength training, including improved metabolic efficiency, enhanced neuromuscular coordination or stronger muscles, many clients simply want to look better. Muscle definition is the result of a muscle remaining in a state of semi-contraction. Machines are designed to create mechanical overload in a specific muscle, which means they can help improve definition in that muscle. One unique programming strategy is to do a compound, multijoint exercise (e.g., a barbell squat) followed immediately by a muscle-isolation exercise (e.g., a machine-based hamstring curl) to continue using a specific muscle to the point of fatigue, which results in greater definition.

When used properly, free-weight equipment like barbells, dumbbells, kettlebells and medicine balls can be extremely effective. However, if an individual lacks a base level of strength or basic movement skills, using this equipment could increase the risk of injury. Even if an individual is strong, the ego is sometimes stronger, causing him to lift a weight that is heavier than his existing level of strength. While overloading a barbell for a squat or bench press could cause serious injury, machines allow a user to lift with maximal loads with a minimal risk of injury from falling weights.

The best exercises are the ones that improve your performance outside of the gym—whether that means running a half-marathon, moving furniture around your living room, or climbing onto your kitchen counters because your home was designed for tall people.  Those exercises are what trainers call “functional,” and by and large, they require free weights. Free weights allow your body to move throughout all three planes of motion, so that you move throughout space like you would in normal life.

Since free weights, unlike machines, aren’t fixed to a certain path, that means you don’t just have to push or pull in one direction. You also have to keep the weights—and yourself—from wobbling. That’s a good thing for all of your muscles. Because your body has to work to support the weight and control the movement, your larger muscles, stabilizer muscles, and core all work together to control your movements. So with every rep, you’re strengthening way more than one muscle

Free weights don’t just work multiple muscles at once. They make them work together, which is critical for balance and coordination. Individuals who performed free-weight exercises improved their balance almost twice as much as those who performed similar exercises on resistance-training machines.

Both count as resistance training, but your body responds pretty differently to free weights vs. machines. Free-weight exercises trigger a greater hormonal response than do similar exercises performed on resistance machines, according to a studies.

Free weights are arguably the most versatile workout tool ever. All you need are the weights and a few square feet of empty space, and you can perform hundreds, if not thousands, of exercises to strengthen every muscle in your body.

Can you afford a half dozen resistance machines? Or fit them in your house? Probably not. But a few sets of dumbbells? That’s totally doable. To save serious cash and space, consider buying a pair of adjustable weights. A set can cost anywhere from 50 bucks to a few hundred dollars, and they work as up to 15 dumbbells in one. Some adjust from five pounds each all the way to 50 pounds each, so one pair is all you need.

A great place to start. It might seem obvious, but doing different exercises improves your fitness in different ways. Fitness and strength come in many different forms, so mixing and matching your exercises will help improve power and efficiency.  Mixing a variety of cardio, strength and stretching into your workout regime you’ll be working a mix of muscles and ensuring overall fitness.

When developing a cross-training routine, the possibilities are endless. The goal is to select exercises that require different movements than your preferred activity. For example, runners may want to add racketball, swimming, or weight training into the rotation. Combining circuit-training, sprinting, plyometrics, and other forms of skill conditioning, such as balance training, is a well-rounded option as well.

Mixing up your workouts, you’ll be able to avoid injuries that arise from the overuse of certain muscles.  This can be especially important if you’re a dedicated runner, because it’s a sport that hits certain parts of the body hard every time you pound the pavements. Improving strength in the supporting leg and core muscles can help you avoid overuse injuries.

Cross-training isn’t only good for your physical health. Mixing up your training can also help you maintain good mental health.  Physical activity can help improve one’s mental clarity through the release of endorphins. Different types of activity can either help one find calm in a hectic life or find release after a stressful day.

Not only can the overuse of muscles cause injury, it can also cause the body to have an over-reliance on particular areas of the body to compensate for the injured parts.  Cross-training can help reduce or remove any imbalances in the muscles in your body by working on the areas not used so much during your main activity.

Whatever your preferred sport is, you have to take some rest days to recover and get the most out of your training.  These rest days are a great opportunity to try another activity.  One of the best benefits of cross-training is that it allows you to try active recovery alongside periods of outright rest, which again can improve fitness and help avoid injury.