Time in Cross-Training and Maintaining Aerobic Fitness

[Penny Abdiel]

I have to cross-train while rehabbing from a stress reaction in my hip. Im XT predominantly by elliptical and pool-running when I can.

I'm not concerned with equating my cross-training with X number of running miles. But I'd like to know what would be the minimum time I should XT at an aerobic intensity (based on HR - its the only good metric I have) to maintain my fitness. I know it probably depends on the individual. However, surely there is a minimum amount of time, below which its not really going to provide sufficient aerobic stimulus, and a maximum time, above which you reach the point of diminishing returns.

While I would usually try to cross-train for the same amount of time I would spend running, I'm also trying not to delay healing. So some days 30-40 mins might be all I can do, based on how my hip feels. And if I can only do 20 mins, if I'm not really getting any fitness benefit, I might be better off resting completely. But when I'm feeling good, I also want to do as much as I can to maintain fitness.

Help, anyone?

[Sasha Pachev]

The general principle is that the benefits curve is very steep in the first few minutes of exercise, then the slope gradually diminishes until you reach the point of diminishing returns when it starts going down. So, for example, 5 minutes of running a day is much better than nothing, 10 minutes a day is better than 5 but not by as much as 5 minutes is better than nothing, 15 is better than 10 but not by as much as 10 is better than 5, etc. Then maybe when you reach maybe 90 (depending on the person the limit could be different) 95 would be actually worse than 90.

So 20 minutes would be much better than nothing. My approach towards recovery from injury is to find the highest volume and intensity that does not make the injury worse and train at it. This way you maintain the fitness while at the same time keeping up the body rebuilding hormones high which should help with recovering from the injury.

[Penny Abdiel]

That makes a lot of sense.  Thanks Sasha!