There is no doubt that exercise is good for health, but excessive exercise is also bad for health, statistics show that one in twenty people are over-exercising, and their risk of premature death is significantly increased. So, what is the most beneficial amount of daily (weekly) exercise? In our daily lives, we are often told that exercise is good for our health and can prevent many diseases. Today, more than one in twenty exercise fanatics spend a significant amount of time each day running and exercising, but a new study suggests that excessive exercise may not be a good thing, especially for those whose heart is not functioning particularly well. A study from the Lawrence Berkeley National Laboratory looked at 2,400 heart patients and found that moderate exercisers who ran 30 miles (48 kilometers) or walked less than 46 miles (74 kilometers) a week were less likely to die from heart disease than others. In this study, scientists have identified a threshold of moderate exercise, beyond which exercise loses its protective effect and becomes very dangerous. The threshold they studied was the increased risk of heart attack in people who ran more than 4.4 miles (7.4 km) per day or walked more than 6.6 miles (10.6 km) per day. In this statistic, it was found that one in 20 people who were over-exercising also had a significantly increased risk of premature death. From this study, they found that excessive exercise can bring about “excessive heart injury”.