Michael Hanslip Coaching

If you want to go faster, you have to pedal harder

Zone 1 training

You should be doing more zone 1 training. If you take a graph of lactate levels against heart rate, there is a gentle increase at first which moves (sometimes with a sharp inflection point, more often without) to a steeper increase. To generate one of these curves for a rider involves a progressive test that begins easily and progresses in steady steps to failure. Lactate levels should be checked at the end of each step. Different coaching methods use different numbers of zones, but all generally recognise the area before the actual or implied inflection point as zone 1. This is where around 90% of your time on the bike should be spent.
Zone 1 time promotes efficiency at a cellular level. Zone 1 can be completely fat-fuelled. Higher zones cannot. The more time you spend where fat is the primary source of energy, the better your body gets at using fat. The more time you spend in zone 1, the more your body is encouraged to produce mitochondria. As the energy source for the cell, more is better.
Zone 1 is the only training zone that impacts all training zones. You can spend lots of time in higher zones, getting really tired and heading towards overtraining. But that training time only really impacts the region it is "in". If you train a lot at 90% (or 75% - or any above 60% which is approximately where the top of zone 1 sits) then you can improve your response at 90% with no impact anywhere else. However, training in zone 1 moves the entire curve to the right. The inflection point goes up to a higher heart rate. Everything improves by shifting to the right.
 
The classic error in training is to approach the easy days too hard and the hard days too easy. Mostly it produces fatigue. Progress can happen for a while, but a plateau that you can't get off will be reached. Ease up on the easy. Attack the hard.
 
When you are reflecting on whether your training goal of 90+% at zone 1, you need to include all your time on the bike. So, racing too. Which is difficult or impossible if you race often (and aren't a pro who spends hours in between races in zone 1).
 
Since I have started making almost all my commutes in zone 1, I have taken around 10% off my commute time at the same, or perhaps even lower, heart rate. Efficiency gains!