Use a Treadmill to Increase Your Strength
Unless you spend a lot of time at the gym, or are a bodybuilder yourself, you probably think that bodybuilders spend their workout time just lifting heavy weights. After all, if their aim is to build their size and strength, they probably don't spend much time on the treadmill, do they?
Serious weightlifters may not seem very concerned with cardiovascular exercise, since what you probably see them doing the most is just lift as much as they can, at least during competition. Sure, their heart rate rises, but it's not something they really notice during their competitive lifts, do they?
Consider how they train for these single maximum lifts. Generally, they train by doing multiple repetitions and sets, using weights which are much lighter than their maximum capacity. Now, if you've ever done sets of squats or dead lifts with a heavy weight, you already know that it really can get your heart and lungs going, even to the point of exhaustion, just like sprinting. You can see that there is a relationship between cardiovascular training and weight training. A weight lifter’s cardiovascular fitness can definitely affect how much he can progress with his weight training. A serious power lifter will make sure to work on every area of his fitness in order to prevent being held back by any weakness that might affect his ability to achieve his maximum lifts.
The heart is a muscle.
Like any other muscle in the human body, it can be strengthened by training. Short intense periods of exercise tend to make the heart stronger and larger, while moderate exercise for a longer duration (for instance, jogging) will tend to improve the heart's efficiency by actually reducing its size. While both kinds of exercise are good for you, a heart which has become larger and stronger due to training is better equipped to deal with the short, intense bursts of activity required by heavy lifting.
There is plenty of peer reviewed evidence of this fact, though you probably don't need to have a journal in front of you to realize that short, intense physical activity increases cardiovascular health or that having a higher cardiovascular capacity can contribute to strength. Doing sprint intervals on a treadmill or elliptical machine a couple of times per week can yield impressive results. Just add treadmill sprints of 30 seconds or so, alternating with a few minutes of slower running. Do this for about 30 minutes total, right after your warm up. This will help you strengthen your heart and circulatory system and allow you to focus the rest of your workout where it belongs - on the muscles you need for lifting.