There’s no doubt that fitness exercises are a vital part of a healthy lifestyle. They help prevent heart disease, strengthen muscles and bones, burn calories and improve balance and flexibility. But not all exercise is created equal – some work better than others, in terms of the results you get, the time they take and how hard you have to push yourself. The experts we consulted for this article agree on a few key things:

— Intensity matters. It’s important to push yourself during workouts, but not to overdo it. “Avoid overworking muscles, as this leads to injury,” says a trainer at Body by Design in Oldsmar, Fla. “Start slow, then gradually increase intensity and/or pace.” Aim for two to 10 minutes of high-intensity activity, followed by a few minutes of low-intensity activity. This combination of intensity and rest helps your body recover from the stress of exercise and improves overall performance.

— Use compound movements. These multi-joint exercises work more than one muscle group at once and are a must for people looking to build strength efficiently. “Squats, for example, are one of the best exercises because they target all three quadriceps muscles, the hamstrings and the gluteals,” says David Petersen, a trainer at XS Fitness in Oldsmar. “They also work the core and provide a great cardio workout.”

— Start small. It’s important to ease into a new exercise program slowly and carefully, especially if you haven’t exercised in a long time. A common mistake is to jump right into a vigorous training program without easing into it. This can lead to injuries and, at the very least, can cause stiffness and soreness.

Exercise also boosts blood flow to the skin, which in turn delivers nutrients that help repair and protect against diseases such as cancer, diabetes, high cholesterol, cardiovascular disease, rheumatoid arthritis and even some types of depression. And, of course, exercise promotes a positive mood by elevating endorphin levels in the brain.

Balance and flexibility exercise can also improve your golf, tennis, walking or running skills, and may help you avoid falls as you age. Some exercises that help with balance include hula hooping, yoga or pilates and the plank. Flexibility exercises, on the other hand, include stretches that can be performed while standing on one leg or by moving through a full range of motion.

The best fitness exercise for your money is any that challenges you to do more reps in a set (or rounds of reps) than you can complete while maintaining good form. For example, when you do biceps curls, you can use dumbbells to increase the load on your arms as you perform the movement. This allows you to increase the number of repetitions in a set, and eventually build up the strength to move heavier weights on your own. This is an essential principle of progressive overload, an important concept in all forms of resistance training. fitness exercises