Michael Hanslip Coaching

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

Metabolic efficiency

The traditional way to start training for the season was long slow distance. Ride a lot, slowly. More recently, this has been replaced with stuff that seemed more scientific. More structured. Turns out the old idea was a good idea.
Most readers will be familiar with the concept of aerobic fitness and possibly anaerobic fitness. Literally meaning "in the presence of oxygen" and "in the absence of oxygen", it can apply to bacteria too (anaerobic bacteria die in the presence of oxygen, having adapted to non-oxygen environments). Aerobic in fitness terms is working at levels low enough that the requirements of the muscles are met by the blood (and hence oxygen) supply from the cardiovascular system. Anaerobic happens at higher levels of performance when oxygen is limited.
Incidentally, this is why drugs like EPO are so effective for endurance athletes - EPO stimulates more red blood cell production which provides more oxygen carrying capacity which lifts the maximum aerobic activity point. This is important - in the presence or absence of illegal performance enhancing drugs - because anaerobic activities can only run over a short time period before their resources are exhausted. Without making this a lesson in physiology, suffice to say efforts between 10 seconds and 5 minutes are mixed products of both. Pure anaerobic is limited by the energy supplies in the cells themselves to around 10 seconds. Over 5 minutes and it is going to be an aerobic effort.
The reality is that there are no hard lines, but this is a convenient manner to think about things.
This rule - no hard lines - also applies to heart rate zones. Some people have 4 zones, others 6. I've seen more, and fewer. No magical transformation occurs at a given heart rate. Which is why too many zones is not helpful. I'd be quite comfortable with 3 zones: low, medium and high. Low is the level a person can go for hours without feeling stressed. Medium is the level at which the accumulation of lactic acid in the blood starts to make things stressful. And high is that really top-end stuff that you can't do for more than a few minutes at a stretch.
Low could also be called recovery. Medium could be called aerobic. High is hard work - I don't have a nice name for that. In power terms, high is anything from around the MAP and up (Maximal Aerobic Power is the power one can produce for a 5-minute stetch).
Back to metabolic efficiency. The coaches I read are all concerned about metabolic fitness these days. This is a measure of efficiency in the cells. It isn't solely down to the number of mitochondria, but roughly equivalent to. More metabolic fitness returns many good things to the endurance athlete and also the human being. A high level shifts the lactate curve to the right on the graph. That means for any given effort (in Watts on the power meter or bpm on the heart rate monitor) the lactate level will be lower. The apparent effort will be lower. The "head room" in that person's system is greater. More capability for the machinery of the body to propel one faster longer.
Higher metabolic fitness is also associated with a healthier, longer life.
One of the easiest ways to increase metabolic fitness is through the long slow distance of old. There are some cool ways to tweak it a little here and there, but you want the results, you have to put in the time.
In the running sphere this is good news for runners who get injured from trying to run fast too often. In any sport it is good news for those who dislike the hard work of a mostly HIIT program. Injury potential is low all around. Less soreness too. In a time-limited lifestyle there can be issues with getting in enough but that is a separate issue.