When it comes to training boys and girls there is a common misconception that they will do different workouts. This is true to a degree, but the essence of training will remain the same. The total weight that either one uses will differ, but the movement is the same. The reason the weights differ is because of the hormones that are found in the to body systems respectfully. Boys have more testosterone than girls, so they will build muscle easier than girls will. Also, just because girls weight lift does not mean they will become bulky and masculine, on average, they do not have the testosterone needed to build that type of muscle. With all of that being said the reasons that boys and girls should train the same way is because the skeletal muscles and the nervous systems in one's body does not differ because of gender.
Think back to high school anatomy class and the models of the muscular system, or think of a muscular system picture you have seen. The muscles are going to be the same whether the model is portrayed as a boy or a girl. There are no skeletal muscles that differ just because the gender of the model changes. The biceps are in the same place, the pecs are in the same place, and the hamstrings are in the same place. In general no matter the person the average person will have all of the same muscles as the person standing next to them. The biceps still flex the arm, the chest still pushes objects, and the hamstrings still flex the leg. This means that the muscles can still be worked the same way when it comes to training. Both boys and girls should bench, squat, and deadlift to some degree. The type of variation will depend on them, but in the end will benefit both in the same way.
Much like the skeletal muscular system, the nervous system is the same in both boys and girls nervous systems work the same way. A sensory nerve relays information to the brain for the brain to send a motor function to the muscles. Without the nervous system working properly it is not possible to move the muscles. With the nervous system functioning properly, the muscles move, when the muscles move they can be trained.
At the end of the day there are lifts labeled "boy" lifts and "girl" lifts. Usually any upper body lift is labeled "boy" and any lower body is labeled "girl" What I say is there are no "boy" and "girl" lifts. There are just lifts, so fellas do a booty workout and stop skipping leg day, and girls stop skipping arm day and do a couple reps of bench press. Work the muscle groups equally and see the results!
