“I only did a spinning class/bootcamp/watt bike…”, a defense I hear fairly frequently as a coach. The reason for the “only” in the sentence and the slightly defensive tone is that the schedule for the day said “REST” or easy recovery run.
While I will agree that cross training can add benefit to your running, even though it totally goes against the law of specificity, the gains can become losses if these sessions are not smartly planned into the overall training program.
Training to improve performance involves a well managed rhythm of stress, rest, adaptation, stress, rest…with the greater percentage being rest or easy recovery exercise and only a small percentage stressful training e.g. high intensity intervals or very long runs. Should this ratio be switched around then the continuous prolonged stress on the body puts you at risk of descending into the valley of overtraining. Worse, if you are already under a lot of lifestyle stress from work, family etc. then the stress overload could lead to stress response shutdown, clinically referred to as adrenal fatigue.
And this is where cross training comes in, if your body is already fatigued from training (plus potentially under additional stress), then doing a hard “cross training” workout, even though it is not running, is still putting the body under further stress and merely compounding the fatigue.
So how best to incorporate your cross training? If you are going for high intensity cross training that leaves you pretty pooped then be sure to precede and follow these days with an easy recovery run or a rest day. If you already have a high intensity run workout in your training schedule, then you might want to alternate one week run session, one week cross training session. Unless you are able to handle to hard sessions a week, but most recreational runners only cope with one.
For those using cross training as recovery, replace your recovery run (not rest days!, training is training) with gentle recovery alternative exercise eg. gentle spinning on the bike in low gears, easy swimming etc.
Manage your fatigue well and you will reap the benefits of your chosen cross workout.