I have noticed on this site (and elsewhere) posts from a number of folks who feel that certain forms of cross training such as swimming and cross-country skiing in particular, are very beneficial during the base phase. I like to do both of these myself, and I got to thinking about it.
Has anyone seen any studies (i.e., something beyond anecdotal reports) that support this idea? If it is indeed true (and I think it may be), I wonder why. I came up with a bunch of possible reasons, some pretty obvious, and I'd like a little feedback:
1. Less pounding leads to less likelihood of injury and therefore greater overall training time.
2. Using muscles in different ways tends to create muscle balance (vs. singular training creating imbalance) and thus greater range of motion (and again, less chance of injury).
Beyond these, I am wondering about possible changes in lactate threshold. Now I'm not a physiologist, but I'm hoping that someone here with that training can comment on the following (most of what I know about athletics/physiology comes from reading Daniels, Noakes, et.al.). As I understand it, your lactate threshold is a function of two things: lactate production and lactate clearance. When production exceeds clearance we get the well known deflection in the associated curve. Is it possible that swimming and cross country skiing, by creating an endurance training effect on the upper body muscles that you don't get from running enhances their lactate clearance ability? Thus, when you're running, the now trained upper body muscles can consume the circulating lactate more efficiently, and therefore delay the curve deflection resulting in an increased velocity at LT (i.e., faster race times). It seems logical to me, but like I said, I'm no physiologist.