"Static or heavy resistance exercise: When an exercise causes a muscle to use more than about 25 percent of its strength, such as during heavy weight lifting, the pressure within the muscle increases and causes the small blood vessels (arterioles and capillaries) in the muscle to collapse. When this happens, oxygen-rich blood cannot reach the muscle. Reducing the amount of blood flowing to the working muscle during static or heavy resistance exercise can cause temporary pain in the muscle.
This lack of oxygen, called tissue hypoxia, causes a rapid increase in both systolic rate and the diastolic rate throughout the contraction. It is believed that this increase in blood pressure is the body's attempt to get oxygen to the working muscles by forcing open the arterioles.
The speed and magnitude of the rise in the systolic and diastolic rates are greater as the intensity of the contraction increases and as the duration of the contraction lengthens. This does not happen, however, if the contraction lasts for only a few seconds or if there is a rest period of at least a few seconds before the muscle is contracted again."
No mention of any long term heart damage in the article.
