
Originally Posted by
Seal
all out sprints for 30 seconds at a time with a few minutes of recovery in between.
I've always read that the interval (i.e. the recovery) should be no longer than double the repeat (the effort). The interval workouts I do are one minute sprint/one minute recovery; three minutes at about 30 sec/mile quicker than 5K pace/three minutes recovery; ladder intervals going in 30-second increments from 30 seconds to 2:30, up and down the ladder twice, with recovery duration equal to the effort.
Twenty minutes is kind of long to be considered intervals anyway, IMO - valuable work, but more like speedplay or tempo work than intervals. You might add those workouts to your weekly routine rather than substituting them for interval days.
On your other implied concerns:
Here's a great video about riding in traffic. There are certainly roads in my area that I wouldn't ride on (narrow, busy, poor sight lines), and I have no idea what the roads are like where you are, but even in Florida there are some roads that are safe and appropriate for cycling.
If the bike lanes you refer to are off-limits to pedestrians, then great, go for it. But if you're talking about shared use trails, then you need to take the other users into account for your safety as well as theirs, and that means keeping your speed down unless you're way out of town with no one else around, and no adjacent homes or parks from which someone might wander onto the path without looking. There are many threads here about appropriate speed on MUPs. Four times pedestrian speed is already approaching unsafe, but it's generally agreed that it's a reasonable compromise for an unreasonably designed facility.
Speed comes from what you put behind you. - Judi Ketteler