Answering a common health conundrum, scientists say 'no amount of exercise is too much' when it comes to matters of heart health. This analysis of more than 90,000 people studied over a five-year period found that 'every step counts' towards improving cardiovascular health. In the study published in the journal PLOS Medicine, the top 25% of people who engaged in vigorous-intensity activity had an average reduction in risk heart disease of between 54% and 63%. 'This debunks the myth that there is a peak beyond which you should not do more exercise,' researchers from the study said. Cardiovascular disease is the leading world's number one cause of death - killing almost 18 million people a year globally, according to the World Health Organization (WHO).