Marathon training, which involves many hours of running each week, may not be good for your marriage, but it is good for your heart, at least according to research conducted by doctors at Massachusetts General Hospital. HealthDay reports that the researchers studied 45 men, aged 35 to 65, who were recreational runners planning to run the 2013 Boston Marathon, and who ran 12 to 36 miles a week for 18 weeks. At the start of training, HealthDay reports, half the men had at least one heart risk factor such as high cholesterol, high blood pressure or a family history of the disease. After training, the men had a 5 percent drop in bad cholesterol, a 4 percent decrease in total cholesterol, a 15 percent decline in triglycerides and a 1 percent fall in body-mass index. Peak oxygen consumption, a measurement of heart-lung fitness, also declined by 4 percent. No note on the how the training influenced their home life.