A 20-pound dumbbell, or any resistance weight, is an effective workout tool as long as it challenges your muscles. If you are able to perform between eight and 12 repetitions with the weight, your muscles respond with improvements. When the 20 pounds is no longer challenging, and you are able to complete more than 12 repetitions, it is time to increase the resistance.
Although not as exciting as the actual workout, learning what happens to the cells in your muscles helps you understand how muscles grow. When you provide resistance and make a muscle contract, damage occurs to the cells in the muscle. To combat this trauma, repair cells are activated to mend the damage. The repair process often leads to an increase in muscle fibers, or muscular growth. Much of this process depends on hormones, age and heredity, so your muscle growth is different than that of your friend.
Use dumbbells for upper-body exercises such as shoulder presses, biceps curls, triceps kickbacks, back row and chest presses. If your strength does not allow you to hold one dumbbell in each hand, hold onto one weight with both hands when strengthening smaller muscles such as your biceps, shoulders and triceps. For example, hold one end of the dumbbell in each hand for arm curls, overhead arm extensions or upright rows.
You may have an easier time holding onto a weight in each hand when you strengthen your lower body. Your legs have larger muscle groups, except for your calves. The calves are used to carrying your body weight, though, so they usually gain strength through everyday activities and don't require as much targeted work. Include exercises into your routine that target all your leg muscles. For example, perform squats, lunges, deadlifts, calf raises and wide legs squats holding dumbbells at your sides or up on your shoulders.
Muscle growth does not only depend on providing resistance to the muscles. Recovery is essential for muscle repair. That is when the growth occurs. If you perform a full-body workout and exercise your shoulders, arms, back, chest, abs and legs, allow two days of rest for complete muscle recovery. When you train only one or two muscle groups together such as your back and biceps, or legs and shoulders, allow at least one day of rest before you train again.
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