Guidelines for using spinning (stationary bike) as cross-training for long-distance running

Question

I'm interested in using spinning (group stationary bike class) as part of a long-distance-running training plan (from half marathon to ultra marathon). Typical plans include running at least 4 days/wk and weekly mileage of 20mi to 50mi (or more). I've completed marathons before without including cycling (or much cross-training) but I want the added benefit that comes with cross-training on days off from running (avoiding injury and adding fun are also motivating factors).

It should be given that I go easier/harder based on feel, I do not spin the day of a long/slow run, and that there are day-to-day variations (e.g. the instructor and their plan for the day, the bike itself, etc.).

I'm wondering how to choose the right level of intensity and whether it is more beneficial to focus on cadence (speed) or resistance. Or is the random nature of this form of cross-training the main benefit? (I'm thinking this is similar to the fartlek run style of training.) Lastly, classes are 1 hour long - is it wise to let this type of training actually supplant some amount of running? i.e. each week let N hours of spin reduce running by N hours (up to a point).

Answer 1

Were you aiming just for 10k or half marathons I would recommend using bike to perform HIIT, focusing on improving cardiovascular ability.

Because you want to do marathons and ultras I would recommend that you practice by running long distances, 5-6 days a week, every week, for a year or two. Once you have completed a marathon or ultra then you should look at improving your time through targeted training.

Answer 2

I'm doing ultra marathons as well as spinning for some years now and I always heard a lot different arguments pro and con spinning as cross training for (long distance) running. I neither have concrete numbers nor specific studies to quote, only my personal point of view:

The best training for running is running and the best training for running long distances is running long distances. Replacing a running session by a spinning workout is better than skipping the session completely, but keeping the running session a running session is - in general - the best.

The point is different if you're actually adding spinning workouts to your regular training plan, especially if adding another run to your weekly schedule is counterproductive because recovery time for your legs would be too short or you already hit your personal limit of weekly mileage.

In terms of intensity while spinning you don't have much of a choice if you're visiting a typical spinning class. Of course, you can decide on which parts to put full effort, but in general spinning classes are a combination of HIIT, switching between cadence and resistance work. HIIT on the bike can improve your running performance by a really small amount, I guess, but it's not the main target for long distance running.

My personal advice, or at least, what I'm doing: two consecutive spinning classes once per week as cross training (mainly because it's fun and something different for the body, but I won't skip an essential running session for it) and a long spinning session for myself on low intensity (mainly for my mind and for another long but still easy workout on a regular rest day).