If you don't have a field or a ball, you can still train for soccer using the equipment you find in a gym or fitness centre. You can build muscle, improve your cardio-respiratory functions and train your heart and lungs for the high-intensity, start-and-stop demands of soccer. Using a year-round periodization plan, you can use a gym to get and stay in top shape for soccer.If you do nothing but follow a generalized weights routine you find in popular fitness magazines, you will increase your power. Do this in-between seasons. Another, highly effective form of power training is called plyometrics. These bridge the gap between strength and speed by combining elements of both in single movement patterns.You'll want to build muscle for soccer, especially your lower-body muscles. Perform exercises such as deadlifts, squats, hamstring curls and leg presses that target the quadriceps, calves, hamstrings and hip flexors. If your goal is to build muscle, start first with doing an exercise with a low amount of weight and high number of repetitions. If you're doing leg presses, do three sets of eight to 10 presses with an amount of weight that is challenging and that will fatigue your muscles within 90 seconds. Over time, you can try using heavier weights and perform a lower number of repetitions that will fatigue your muscles in a shorter period of time, such as 30 seconds. Both methods, namely high reps with light weight and low reps with heavy weight, have been proven to be effective for muscle building in both men and women. Rest for 24 to 48 hours before exercising those muscles again to allow them to recover and grow.When you get closer to your soccer season, begin training your muscles in ways that help you use them for long periods of time. Muscular endurance exercises feature more reps of exercises using lighter weights -- about 40 to 70 percent of the maximum you can lift. A circuit training workout is another method of building endurance. Circuit workouts are designed to develop strength for all the major muscle groups in your body while building endurance. Circuit training includes a series of different exercises with eight to 10 reps of each exercise with a one-minute break between each exercise. The exercises in a circuit series are designed to use your large muscle groups, and this type of training incorporates an appropriate amount of resistance and aerobic intensity.Making a powerful move to a ball, such as when a goalkeeper lunges for a shot on goal, requires explosive strength, which can be developed with gym equipment. Exercises such as box squats, in which you start out seated and stand up to lift the weight on your shoulders, and leg presses help you improve explosive strength. Jumping onto a box with both feet, or standing with one foot on a box, then pushing yourself up, are examples of non-weighted explosive strength exercises. Perform six to eight reps of explosive strength exercises using about 50 percent of your maximum weight -- your weight load will depend on your starting strength.Reactive or plyometric strength is your ability to coordinate more than one muscle to create a movement. For example, when you jump to head a ball or block a shot, you bend your knees downward first, then push up and jump. To train plyometric power, perform exercises such as jumping off a box, then jumping up as soon as you hit the ground. Reactive squats have your bend down, pause, then lift the weight up. Skipping, sprinting or taking giant steps are also good examples of reactive power exercises.Soccer is primarily an aerobic sport, requiring you to recover your breath quickly each time after you sprint for a ball. The game also requires aerobic conditioning. Train for aerobic fitness in the off-season using a treadmill, elliptical, exercise bike or rowing machine. You can perform sprints on these machines using lower resistance, incline and gear settings that let you work at a very high intensity for 30 to 90 seconds. Take a two-minute rest before performing the next sprint -- the rest period between sprints helps you train your ability to recover. Perform sprints using weight machines with light weights that allow you work at a very high intensity for 30 to 90 seconds before you tire.