to my understanding, cross training will always help. Last year, I hadn't ran in at least 9 months. When I decided I needed to get some cardio in before day's end to prepare for the race next week, I went out for a 6 mile run. The entire next week, I couldn't walk right and struggled to stand up from a chair - legs were so sore. I stayed off the bike, even though I didn't feel sore riding it. The following week, I got my first win. go figure.