Strength Training

Strength training is an area that is commonly overlooked by soccer
players and coaches.  Strength training should be considered a
supplemental conditioning tool that can help to enhance your
performance.  Soccer players should strength train to tone their upper
and lower body.  It should also be used to strengthen and improve
explosive power.  Strength training also serves a very important role
in injury prevention and can play a critical role in the recovery
process.  Most important, strength training provides improved strength
and a feeling of being stronger along with a boost in confidence on the
field.  The basic concept of strength training is to overload your
muscles in a controlled manner to cause them to break down.  After
breaking down muscles, getting appropriate rest allows you to build
them back up.

Major Muscle Groups to Train for Soccer
Upper Body:
1.  Chest - muscles that allow you to push.
2.  Biceps - Located on front side of your upper arm.  They allow you
pull up your lower arm.  They contribute to your ability to use your
arms in running and holding players off the ball.
3.  Triceps - They are on opposite side of your arm from the biceps. 
They work in the opposite fashion to your biceps.  Muscles allow you to
extend your elbow and are very important in holding off players.
4.  Lats - Found underneath your arm along the sides of your body. 
give your upper body strength and contribute to your trunk strength.

Lower Body:
1.  Hamstrings - Large muscles behind the back of your upper leg.  Help
you sprint.  In sprinters, these muscles are very strong.  They pull
your heel to your butt.
2.  Quadriceps - also called thigh muscles.  Very important in kicking.
3.  Hip adductors / hip abductors - These muscles pull your legs
together or apart.  The adductors are the muscles that pull together. 
The abductors allow you to bring your leg away from your body.
4.  Hip extensors / hip flexors - muscles allow you to swing your leg
forward and back.  Extensors allow you to extend your leg back, as when
preparing to kick a ball, you cock your leg back.  Hip flexors are the
muscles that bring the leg through when you kick the ball and follow
5.  Gluteals - butt muscles.  Power muscles.  Help you make the
connection between your back and hamstrings and are vital for jumping,
balance, and overall stability.
6.  Calves - large muscles in the back of your lower leg.  Important in
going up and down on your toes.  They also help you point your toe down
when shooting.

Your core muscle group consist of abdominal (front and side) and the
lower back.  They are very important for balance and agility.  It is
sometimes referred to as trunk stability.  Along with gaining strength,
it is also important to understand how to use your strength.  I have
seen very strong players not use their body well and some players with
less strength dominate physically.  Most important, strength training,
just like fitness, can give players great confidence.