If you're running a marathon this spring, you're about to enter the most critical – and difficult – four weeks of training, when 1) your weekly mileage is at its peak; 2) your motivation may be flagging; and 3) you're most likely to get sidelined
of the study between the run-only and run/bike subjects. Not to mention the benefits that mixing up your training with different disciplines can have on your performance. Just a few of these benefits include enhanced motivation due to the variety in your
