Forearm conditioning exercises do not have an effect on hand size.
Although your forearm and hand are closely linked functionally, it is not possible to increase your hand size by performing forearm exercises. This is because hand size is dependent upon the size of the bones and muscles in your hand and is not related to forearm conditioning. It is impossible to change the size of bones with exercise, but you can make your hands more muscular by performing specific exercises.
Forearm muscles do not extend into your hand, and exercising them won't affect your hand size.
Understand Your Bones
The American Academy of Orthopaedic Surgeons states that growth in women stops at 14 to 15 years of age and in men at 17 to 18 years. After this time, your bones collect more calcium and become stronger but do not increase in physical size. Bones will also respond to physical stress by increasing bone density at the site of stress; for example, soccer players have denser bones in their legs due to the amount of running involved in the sport.
Train Specific Muscles
Muscles respond to physical demands put upon them by exercise. For example, the muscles of endurance athletes have adapted to be able to perform activities for a long period of time. The leg muscles of a weightlifter who focuses on lower-body strength exercises will become larger and produce more force. However, only muscles that are exposed to an activity adapt. This is why forearm exercises do not have an effect on hand size - only hand-specific exercises will increase the size of muscles in your hand.
Try Basic Hand Exercises
Although forearm exercises will not increase your hand size, the muscles in your hand itself can be easily exercised and made larger without special equipment. Place a rubber band around the four fingers of one hand -but not the thumb. Spread your fingers out as far as you can against the resistance of the rubber band, and slowly bring them back together. Another effective exercise involves squeezing a tennis ball as hard as you can in one hand for five seconds, releasing it and repeating the sequence.
Check Out Your Options
You can also use special hand exercise equipment to increase your hand muscle size and strength. Many versions of spring-loaded grip strengtheners are available, as well as resistance balls for your hand and resistance bands. The majority of these devices also come with manuals detailing a variety of hand exercises as well as methods to make the exercises harder. Always consult your doctor before beginning a new exercise regimen. Stop and seek medical care if needed if you feel pain when doing hand exercises.