Once you have your weight restrictions from bypass surgery lifted (and your physician’s permission) it is time to build back the muscles you lost from surgery.
The muscles are weak from the limited lifting for the last 3 or more months. It is important to go slow and to balance the muscles. In previous posts I write about the importance of posture and stretching after open heart surgery to prevent or manage pain. https://rehabilitateyourheart.wordpress.com/2012/05/21/stretching-your-upper-body-following-open-heart-surgery-12/
The muscles of the chest and back balance one another.
Muscles work like a pulley system, if one group is shortened the other is lengthened. By strengthening the chest muscles the opposing muscles of the back are lengthened. Therefore the back should be worked just as much as the chest to maintain a balance. A common issue is many only train their chest, neglecting the back and this sets the stage for shoulder, neck and back problems down the road. By strengthening both you create a balance to the muscles.
There are many ways one can work the muscles including free weights, dumbbells, resistive bands, or the bodies own resistance – such as push ups. . It is important to start out light. You may have had a 10-20 lb lifting restriction for some time. It is not graduated up but simply lifted. Therefore don’t start with really heavy weights. Work your way up. Start with a few exercises, see how your body feels the next day. You shouldn’t experience days of pain from the first few workouts, you should be able to tell you worked the muscles but not be suffering. Don’t overdo it!
Remember it is approximately one full year of healing following surgery.
The bone is knit together but to rebuild the strength, decrease the inflammation and allowing the nerves to heal it takes a full year. Some precautions to note – if you feel any shifting, cracking or popping of the sternum stop. Try again in a month or two, or modify the movement to avoid the shifting. If you cannot move it without the shifting contact your surgeon.
Breathing with weight training is vital.
Exhale on exertion. This means when you are pushing the weight away from your body breath out. When you are returning the weight to your body breath in. It is extremely important to your heart’s health not to hold your breath. Holding your breath increases the blood pressure, strains the heart, and for some people can make them light-headed or pass out. Not good when you have weights in your hands to pass out! This breathing technique should be used with all of your strenuous physical activities or lifting, pushing, or carrying.
The following images of exercises address the key muscle groups lost from open heart surgery.
Start with a light weight – it may be 10 lbs in each hand or it might be 5 lbs, everyone is different but you will appreciate starting with light weights as we expect a little soreness initially. See what works for you. The initial goal is to do many repetitions, gradually build up the amount of weight over time. Try doing each exercise 10 times, if it is easy than next time add a little more weight. If it is difficult, try less weight next time. It is recommended you start with 10-15 repetitions of each exercise, and do it in 1-2 sets the first week or two. You can gradually add in more sets of the 10-15 repetitions. Don’t work the muscles every day, try for 2-3 times per week. The muscles need recovery time.
Chest muscles – note the elbows of the lady in the second picture, this is an example of good technique. Don’t let the elbows come lower than the shoulders as it puts a lot of stress on the sternum and shoulders, and you don’t want to be hurting the next day. Breathe out as you lift the weight up. Don’t hold your breathe!
Shoulder muscles – note only lift the weights to 90* lifting higher than this tends to irritate the shoulders. Be aware to use your muscles not the swinging of your body for momentum. Lift the weight to a slow count of 1 -2, then lower it even slower a slow count of 1-2-3-4. Remember breath out as you lift the weight up.
These are standing fly’s, the knees are bent to support the lower back’s natural curves and prevent injury. 
Back exercises – standing row. This works the muscles between the shoulder blades. When doing exercises bent over remember to come back up gradually, as many heart patients experience dizziness when bent over. Again remember to BREATHE! If you don’t have weights there are resistive bands that can be used. They can be found at your physical therapy centers, medical supply stores or fitness stores. They come in a variety of strengths, remember start light. Make sure you control the band or weight and that it doesn’t control you. 
Weight machines are good. Here is an example of working both the chest and the back. I love lat pull downs and seated rows. Typically I will have patients work these for 1-2 weeks before I introduce the chest press, as the back is far more neglected than the chest muscles in our day-to-day use. Below are ways of doing the upper back using resistive bands. 
I know some of you are impatient about getting back to push ups. I generally start patients with push ups against a wall initially, gradually moving feet further back. When through the initial muscle soreness, have good breathing techniques then have them begin floor push ups.
Bypass
Rehabilitate Your Heart 