Suppose a new study has found that regular exercise can reduce the risk of developing heart disease by up to 50%. The study, conducted over a period of five years, involved over 10,000 participants across various age groups and fitness levels. Participants who engaged in at least 30 minutes of moderate exercise five times a week showed the greatest reduction in heart disease risk.
Can we infer that "The study only included participants who were already physically fit."? Yes, no, or maybe?