One thing clear to me on this marathon training cycle is that getting in a lot of miles is probably not going to happen. It’s one reason I went ahead and joined the gym near my home: I need to do more to fill in the blanks with cross training. I’ll hit my key workouts whether outdoors or indoors, and then have a variety of indoor options with which to fill in the blanks.
Filling in the blanks however requires some analysis. People cross train, but people don’t have a firm basis from which to equate their cross training to the needed aerobic development.
How much work on the bike or elliptical equals one mile of easy running? Most do an indeterminate amount of cross training, but beyond knowing that it helps some with training, they have no idea how many miles or how much progress it has helped make them.
(I will also note that, while some writers and coaches think it so, I don’t consider treadmill running cross training. I realize at a zero incline, with a consistent surface, and with no wind resistance… running on a treadmill could be easier than regular running. However, there are enough equalizing factors I’ll discuss another time that can and usually do make it as difficult, sometimes more difficult, than regular running. Plus, you still are bearing all of your weight at a higher speed and intensity, as you do with running. So, I consider miles run on the treadmill equal to regular running miles.)
What’s the best way to figure out how much value, how much volume, a cross training workout provided to your training? It’s a question I’ve dabbled with over time, and wrestled with more in recent memory, especially now that I’m cross training more frequently at the gym.
I think the best way to figure this out is:
1. Figure out how many calories you burn in a mile.
2. Figure out how many miles you would like to train in a given week, and how many calories that would burn overall.
3. Take the calories burned from your actual planned running, and subtract that from the number above.
4. The remaining calorie total is the number of calories you need to burn in cross training to equate the desired running volume.
For example, as I’ve mentioned before, I burn on average about 123 calories a mile. This number can go up or down if I gain or lose a substantial amount of weight, but on average I burn about 123 calories a mile.
Let’s say (eating normally and everything else, because I’m fueling my training) I want to run 45 miles a week during marathon training, for me a reasonably high enough amount to test my limits (especially if I’m doing a good amount of speedwork).
45.0 miles per week x 123 calories per mile = 5535 calories per week
So, for the week, I want to burn about 5535 calories from aerobic exercise.
Let’s say (since this is close to what I’m doing now) I can only run 30 miles this week. To figure out the number of cross training calories I need to burn, I would subtract the calories from these 30 miles from my 5535 total.
30 miles x 123 calories = 3690 calories
5535 total calories needed – 3690 calories burned from running =
1845 remaining calories
So, I need to cross train enough to burn 1845 calories per week.
Now, some exercises burn more calories than others. 30 minutes on the bike isn’t as intense as 30 minutes on an elliptical or ARC Trainer. And none of those aerobic exercises are as intense as 30 minutes of running.
This means I have to do quite a bit of cross training to cover that last 1845 calories.
An hour of typical intensity on the ARC Trainer may burn around 660 calories for me. So if I did nothing but that, I’d need to spend a little under 3 hours every week on the ARC Trainer.
For me, an hour of typical intensity on the exercise bike burns about 560 calories. I’d have to spend close to 3.5 hours per week on the exercise bike to burn the needed calories.
And of course in both cases how many calories I burn is a function of the effort I choose to expend on the device, the settings I place and so on. If I go slower or easier, I burn fewer calories, and I need to spend more time cross training overall.
But if I ratchet up the intensity, while I may burn calories more quickly, it’s also more taxing on my body and I could lose some of the recovery it’s supposed to help provide (part of the reason you cross train is to aerobically train at a lower intensity and help you recover for your runs). Perhaps I would just be better off running.
Some other rules:
– If you don’t own one and you must you can estimate on paper, but really you should be wearing a fitness tracker that counts calories burned. You will go off this number first and foremost. Ignore the number on a given cardio machine: It’s not tracking the effect of your heart rate, and its calorie count (usually done according to your entered weight) assumes a single overall intensity effect on everyone’s body, whereas exercises affect everyone’s calorie burn differently. Your fitness tracker will give you a more accurate estimate.
– Obviously, while it helps a trivial bit with aerobic fitness, I don’t count walking. I already walk all the time, and though it can burn many calories it’s too low key of an exercise to develop aerobic and neuromusuclar fitness for a marathon. So, sorry, none of my walking counts towards that missing 1845 calories. Walking is the junk mileage of cross training: It helps a bit but not meaningfully so.
– While valuable, strength training calories do not necessarily count towards your needed remaining calories… UNLESS either a) you did not generally plan to strength train, but you did during a given week… or b) you burned more calories strength training than you would have otherwise, and you know for a fact how many calories you typically burn in a strength training session:
e.g. you know a typical weightlifting session burns 100 calories, and you burned 150. So you count the extra 50 calories, not the other 100 you already burn on a regular basis. This applies whether or not you’re doing supersets, a circuit, or any other strength training where you do several exercises quickly for aerobic purposes.
– Calories otherwise only count from active aerobic exercise. Doing your laundry, carrying groceries, or grooming the yard doesn’t count as aerobic exercise. You do those activities all the time, training or not.
– Taking an aerobically themed class like Zumba, or something like a modern dance class, only counts IF you don’t already do it every week, and if you’re wearing your tracker. Again, be careful with the intensity of such exercise and consider the timing and energy needs of your key running workouts. Only do it if it’s something you’re used to doing on a somewhat regular basis. But… again, it only counts towards your calorie difference if it’s something you don’t do weekly or more often outside of training.
– Yoga, Pilates and other such general exercise doesn’t count either, though it’s obviously valuable for overall flexibility and fitness.
– Calories burned while playing sports are probably fine to count, but if you’re training for a marathon you probably should take it easy on playing sports while doing so because of the clear injury risks from the athletic requirements (e.g. stopping/starting, switching directions, in some cases taking forceful physical contact). There’s a good reason you don’t see professional athletes racing marathons while in-season.
So, if you’re looking to replace miles with cross training while training for a marathon… it may make more sense to track your training by aerobic calories burned than by miles run. That way, you can accurately count all of your training and keep better track of your overall progress and development.