Many days it’s easier (time wise) to do a 3 mi run in the AM and a 3 mi run in the PM. Purely in terms of weight loss and overall fitness (obviously a 6 mi run is better for enhancing run performance) is there a difference in doing two shorter runs rather than one longer run?
do them both at a faster pace than a 6 mile run and you can probably get more weight loss and overall fitness
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For overall weight loss and fitness, you might find 2 runs/day are better than 1. All things equal, you’ll burn the same # of calories, but IMO, your metabalism should stay higher with 2 workouts.
Along the same principles as eating smaller meals, but more often.
I always found my 2nd run of the day to be alot easier for some reason, almost effortless.
No measurable diff. Calories burned is dependent on your weight and distance run and independent of speed.
I agree, 2nd run is a lot easier. Any idea why?
You are warmed up.
The point of warmup is to increase body temp a few degrees, that stays elevated. So there’s that, and now we’re moving away from scientific but the first run “gets the cobwebs out of your legs.”
I’ve doubled the past 2 days and each time, the second run has been MUCH faster. And my legs feel better.
You get a slight metabolic increase from running twice - two times the EPOC - exercise post oxygen consumption or somethign, can never remember exactly what it stands for.
No measurable diff. Calories burned is dependent on your weight and distance run and independent of speed.
There is a slight difference, actually
7 mph = 1.68 calories per kg body weight per mile
8 mph = 1.66
9 mph = 1.64
10 mph = 1.63
I think it’s funny that the formula uses kg and miles together 
The idea of being warmed up for the 2nd run makes sense if the runs are within a few hours, but are you really still warm from a 7am run at 7pm?
Maybe not but you have been moving around all day, your body is warmer, your muscles are warmed up.
Also with an early morning run you are slightly dehydrated, and that contributes too.
No measurable diff. Calories burned is dependent on your weight and distance run and independent of speed.
ummm…what about efficency?
Tigerchik is is spot on.
My experience is with swimming but I’m sure the same applies. Your muscles tighten up over night and the morning session doubles as a stretch session by loosening everything up and getting everything firing.
So while your actual temperature will not be maintained between the morning and afternoon session your muscles remain active during the day and don’t tighten up in the same way they do overnight.
Other than simply “feeling” the difference you can demonstrate pretty easily by measuring how tight your hamstrings are before your morning run and how tight they are before your evening run.
Shows the importance of a good warm up.
Dehydration can also be a factor.
As a side point…
It’s also why swimmers were so peeved that NBC forced organisers to hold the swimming finals in the morning at the Olympics. As far as I know it was the first time in history that a swim meet has had morning finals.
on a separate but much more annoying point, this whole discussion is likely mute with regards to me since I just got a call from the ortho I saw last week letting me know that I have a torn lateral meniscus
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That sucks. Very sorry to hear that.
That doesn’t sound right… Running faster has to burn more calories. If it didn’t then obviously everyone would be running ultra fast, and would struggle trying to go slow.
Running faster has to burn more calories.
No it doesn’t.
If you push a heavy wheel barrel a certain distance quickly, or slowly, you’ve done the same amount of work. When you run, you are moving an object a certain distance. It doesn’t matter how fast you cover that distance. People are confused by this because they forget that the work you do is done by your muscles, not your lungs.
From a theory standpoint I can accept the idea that running faster over a certain distance does not require or use more calories. (Not counting the calories you burn afterwords to repair/rebuild tissue, etc.)
But, running faster for a set length of time would burn calories.
David K
No measurable diff. Calories burned is dependent on your weight and distance run and independent of speed.
** ummm…what about efficency?**
Unless your shoestrings are tied together, your efficiency changes VERY little with speed. Look at tigerchick’s data.
Pulled from a sports nutrition book, not an exercise phys textbook, if anyone has one of those handy I would accept that as a more accurate source.
from what i understand you would burn more total calories running with increased effort (be it up a hill or faster or into the wind or whatever) but where those caolries would come from (in addition to glycogen stores fat or muscle) would depend on whether you were at an aerobic or anearobic pace, aerobic being best for burning fat…
On another note, I am a big fan of splitting runs when time is limited or when coming back from injury as it does allow you to get in additional base miles while reducing the risk of re-injury (even 2-4 hours of letting everything settle down is easier on the body than going straight through sometimes), don’t get me wrong it doesn’t replace the need for long weekend runs when building up for a mary or IM but it can make a longer weekday workout a bit easier (ex 5m am 5m pm instead of 10 straight) while seeming to reduce physical wear and tear, that said on the mental wear and tear it can be tough finishing your run for the day only knowing you have to do it again later