Which is better for fitness - commuting or longer ride on the weekend?

[cyberknight]

Both
The shorter rides can add intervals , sprints etc but you also should work on the longer stuff too.

 

[HarryTheDog]

I have commuted for 12 years and have a nodding acquaintance with a lot of fellow commuters and quite a few of us follow each other on Strava. The faster commuters tend to be the people who dont just commute, they do other cycling as well, sportives,club rides,racing, social group rides etc. Last year I started racing CX and XC again and just started road crit racing. I have gained a coach who lets me commute, but not 5 days a week. Also when I commute I am mostly restricted to not kicking the arse out of it ie going full blast every day. I usually now commute 2-3 days a week, 2 days on a restricted heart rate/power level and only 10 miles each way. One day on 23 mile commute, in easy out like a bat out of hell. Other stuff like a turbo session and a endurance ride on top as well.
Speaking to the other guys who do a bit of racing and commute they also take days off and make one day a fast day, another a easy day to give the body time to recover etc. I find the truly fast guys actually don't commute or do very occasionally, though I have known the odd couple of people who can make the commute work for them as a training tool but they had rural commutes.( can keep a more constant effort going)
I found that the years of commuting with the occasional club ride made me faster than the average but I had turned into a bit of a one trick pony ie a sprinter with good power for less than a minute. Try going full blast on your commute and see actually what is the longest you can go at a "threshold" rate before something gets in your way ( lights, traffic etc) I found on mine I was lucky to get in a 3 minute spell, usually less than 2. So I had to do turbo sessions or a road ride where I could do a good long hard "pull" for up to 15 minutes at a time to help with racing.
I suspect your motive is not racing but if you intend to try that kind of thing in the future you may find your commute isnt the best training for it but it is a good base. I used to do 100 mile plus sportives just based on fitness from my 23 mile each way commutes with no weekend long rides.
In short commutting will get you fit, fitter than the average joe who does a pootle on the weekend, however if you want to step up a level ( whatever that level is, is up to you)you need to do other stuff as well.

 

[tallliman]

I like the regularity of the commute rather than the intensity. However, I'm sure that doing 40miles 3 times a week commuting is increasing my fitness. Often feel too tired to really sprint for a distance though.

 

[boydj]

My fitness has dived since the commuting stopped, even though the weekly mileage totals are similar now. With over 30 sets of traffic lights on the commute, there was a lot of acceleration going on and every commute was almost a fartlek session.

 

[lutonloony]

I try to take one day off a week from commuting. Strangely it seems to be Friday, when I try and re-hydrate after work! Then a club 50ish on Sunday. Not sure my fitness has increased much, but at least it hasn't got worse, but then I'm not really sure of the definition of fitness.

 

[Shut Up Legs]

My commute keeps me fitter than the weekends rides, I think, but then my commute is about 180 miles a week, with a lot of hill-climbing. My training for the European Alps in late June / early July isn't as thorough as I'd planned, so hopefully the commute will prevent the trip *** from killing me.

*** 14 days of riding, 1000km horizontal, 27km vertical. (and cols-a-plenty!)