Strong wrists are needed for activities that use your hands and arms, such as wrestling, yoga, weight lifting and many other types of sports. It's possible to gain muscle, and therefore strengthen and thicken your wrists, but since wrists consist mainly of bones and tendons your wrists can only be thickened so much through exercise and other techniques. Genetics is responsible for the size of frame that you have, which includes bony areas of your body such as your wrists.
Measure your wrists to find out the size that you are beginning with. Since there are not a lot of muscles in your wrist you will only be able to thicken your wrists by a percentage of an inch, even with months of exercise, but measuring will help you evaluate whether your wrists are growing over time.
Squeeze a tennis ball or a stress ball as hard as you can for 10 to 15 seconds. Release, rest for a moment, and then repeat 10 times. Do this at least one time per day to help thicken your wrists. This exercise also helps to relieve stress, which makes it perfect for doing while at work or in other stressful conditions.
Attach a resistance band to the floor, or hold it underneath your foot, while you are standing up. Grasp the resistance band with one hand with your palm facing down. Your arms should be bent at a 90-degree angle. Support your wrist with your other arm. Flex your wrist up and down 10 times in a row, moving slowly and carefully. Switch to the other arm. Do three sets of this exercise three or four days per week.
Repeat the exercise with the resistance band, but this time hold your arm so that you palm is facing upwards. Do three sets of the exercise, with each arm, three or four days per week.
Do activities that strengthen your arms including pushups, arm-intensive yoga poses and weightlifting. Exercise your arms, including your wrists, at least three days per week.
Tips
If your wrists begin to hurt, slow down or lighten the amount of weights that you are using.