Daily commute as HIIT training? I'm cycling to work every day. It's 2x8km it takes around 30 mins (depends on weather, traffic and whether I want to push it or just cruise. I'm starting to see it as an opportunity to make it some sort of actual training - HIIT training maybe?

Something like alternate slow/fast kilometers (or 500 meters), or pushing any hill fast and taking the rest as recovery, etc.

Is it likely to provide significant improvements in Vo2 max? Why yes/no and what exercise structure (with given distances/times) would be most beneficial from that perspective?

Other details:


It's a good commute (mostly bike path with little traffic or secondary roads, relatively long straight lines in a lot of places, good surface, some hills). However 30 km/h is probably a maximal reasonable speed
I can run it too - about 35 mins
I'm prone to shin splint so I wouldn't do things like 1k intervals @ 3:30. Running/cycling uphill would be better (and recovery rest of time).
I have a cardio watch so I can keep pretty good stats of stuff


EDIT (To add details from comments)


David/gshenk: I'm actually at about 50 ml/kg/min for Vo2max @ 34 years old (that was ~1 years ago, might have gone down a tad), which as far as I know is not too shabby. The reason the commute is so slow is that it's still a city-ish setup (so I do have2 major intersections eating up a couple minutes because I HAVE to wait my turn, plus  a little bit not connected I have to take a path &amp; walk my bike on my shoulder). I'm also doing with a mountain bike (so relatively fat tires, not a gear setup especially given to high ratios). The other thing is that this is in the northeast and yes snow, ice &amp; slush will quickly wreak havoc on your avg speed. Ah and I'm also carrying a small pack (lunch, clothes &amp; sometimes a laptop). Nothing crazy but ~10-15 pounds on average. I know a saddle bag would be better.


So ~30 + or - 5 mins in winter, probably getting closer to 20min in the summer.
Criggie: I like your thinking. True I don't NEED to go straight to work (nor get directly back). Excellent idea to remove some constraints.
Some people seem concern about safety - I do hear the concern, but let's just assume for the sake of argument I'm not a total idiot and I'm not going to risk crashing in a trolley full of toddlers just to keep it in my Zone 5 HR interval....
8 km is very short to be able to get in a quality warm-up and cool-down while still having time to get any decent intervals in. Unless you're a complete beginner, you're unlikely to get any meaningful benefit from doing intervals rather than just riding to work steadily. VO2 max intervals tend to be 4-10 minutes each, usually at least 4 in a session with very short ready intervals in between. This is because the most important factor for VO2 gains is the amount of time spent oxygen-depleted.

The only thing that I could see you improving during such a short ride would be your sprint. If you add in some very short (10-15 seconds) max efforts you may find that your peak power improves and the muscular improvement does somewhat help you in your longer rides. For your first few, do them on an uphill section (doesn't need to be very steep) and slow right down to nearly a stop. You should be in a gear that feels much too heavy when you start, but by the end of the interval your acceleration should have you spinning it at a reasonable cadence. These are more of a strength workout than a cardio workout, so you may find that you end up spending almost your entire ride recovering from the short intervals. Just remember that if you don't feel almost broken by the end of the session, you aren't doing proper strength work. Doing these twice a day, five days a week will eventually put far too much stress for your body to recover in time to do a quality session next time. Start off doing it once or twice a week, then maybe ramp up to three once you're used to it.