Doing sit-ups can effectively practice abdominal muscles. You can also lie flat on the bed and touch your toes with both hands (lift your body). Do it slowly. If it is fast, there will be inertia, which will affect the effect. Be sure to do it to the end and do it in place. Or, grab the horizontal bar with both hands, lift your legs horizontally, and repeat.
The biceps brachii is mainly pulled, 1. You can bend and stretch the dumbbell with the big arm, but don't put it last when stretching, so that the biceps are always stressed. Also, you can use Schwarzenegger's method, which has a nice name of 2 1 salute, that is, when you bend over and stretch the dumbbell arm, because it is 65438 from straight to bent. 2. Shoulders do pull-ups.
It is advisable to have muscle aches every time. Remember not to do it every day. Every time you do anaerobic exercise, you should destroy your muscle tissue as much as possible, and then use enough time and nutrition to repair the damaged muscle tissue and let it grow. To put it bluntly, muscles grow out at rest after anaerobic exercise.
Be sure to combine aerobic exercise, such as jogging. If you simply do sit-ups, the fat layer will not decrease, the muscle layer will thicken and the waist will be thicker.
Only scientific fitness can have perfect muscles. (Original, don't copy)