You don't see a lot of body builders on the soccer field. Excess upper body size can weight you down and steal agility from your skill set. With that said, strength training plays a larger role in soccer than every before.
Lifting weights doing the old 3 sets of 10 system is not going to do the trick in soccer. You want to build lean body mass to give you explosive speed and endurance.
If you are coaching young players, then you don't need to get them into the weight room to build size. Simple body weight training can add just the right amount of bulk to players to fend off defenders and win physical challenges.
As a soccer player you are going for a physique like this...
...NOT like this
Push Ups
Push Ups are a great way to build up the chest, shoulders and core. This will enable your players to throw the ball in for greater distances, knock defenders off balance and make quick cuts. There is a nearly limitless number of push up variations, but we'll detail some of the common ones below.
Standard Push Up - keep your back and abs tight. Lower your body down until it is just a few inches off the floor. Hands will be at a comfortable width, just a bit wider than the shoulders. Keep a straight back.
Military Push Up - place your hands directly under your shoulders. Keep your elbows and arms tight against your body throughout the movement.
Wide Fly Push Up - extend your hands 3 inches wider on each side than you would do for a standard push up.
Diamond Push Up - from the standard push up position, bring your hands together so that your thumbs and index fingers touch. Align your hands right below your heart. This is a pretty tough exercise. You might need to spread your hands out a bit to make it easier.
Squats
Squats are great for the legs and develop explosive power and speed. Here are a couple of variations to get you started.
Squat Jumps -
Stand with your feet shoulder-width apart with your upper body leaning slightly forward. Lower your body until your thighs are parallel to the ground. Explode upwards and extend your arms. Land on both feet and repeat.
Run-Stance Squats - start with your feet in a stance that looks as if you are about to run. The toe of your front foot should be lined up with the heel of your back foot. Perform 4 squats from this stance. After you complete the fourth squat, leap up and twist so that you land facing the opposite direction. Repeat the exercise from this side.
Run Squat 180 Switch - start with your feet in a stance that looks as if you are about to run. The toe of your front foot should be lined up with the heel of your back foot. With each rep, jump up and turn 180 degrees. Perform another squat and 180 twist back to the original position. Do a set of reps turning left and then a set turning right. You can add difficulty by touching the ground right in front of your lead foot after each rep.If you need help developing a successful soccer strength program, then you must take a look at Total Soccer Fitness.
Total Soccer Fitness and Total Soccer Fitness for Juniors are focused on developing comprehensive soccer fitness programs that train you and your players to develop the physical attributes you need for soccer: speed, conditioning, endurance, agility & flexibility.