Spinning vs Grinding – What’s Better?
IMHO they both are important. Spinning typically relies mostly on a person’s cardiovascular system. While grinding relies heavily on a person’s musculature. The higher your power to weight ratio on a bike, then the more likely you rely on spinning (rather than pushing) capabilities. However, keep in mind that it is very difficult to keep a blistering pace as a spinner for 112 miles on a bike. Sadly, most people who are good at spinning don’t train at all to be good at grinding. The fastest people at 112 miles will be able to both spin and grind so they can “rest” while they do one to the exclusion of the other. When you spin at 90-95 rpm you rest your muscles, and when you grind at 80 rpm you rest your cardio system.
A true grind is when you push at a cadence of something less than 80 rpm. But when racing 80 rpm is the standard rate considered to be grinding. Spinning on the other hand when racing is 90 to 95 rpm. And there is nothing wrong with riding at a cadence somewhere between 80 and 95 rpm, but you won’t be getting as much of a “rest” if you do while trying to maintain a steady power meter output. It really is best to be able to polarize your riding (either 80 rpm or 90 rpm) while keeping power (and ideally pace) constant.
When training you build more muscle and power capacity when you grind. Some people call it “overgearing” work. You’ll need to drop the cadence down to 60 to 65 rpm, which is what you probably typically do when climbing hills on a bike. While such a low cadence during some training rides is great, it is not ideal to do much at this low cadence rate during a race (unless the race is very hilly). Even if the race is hilly, then you should try to set up your bike with gearing that will allow you to avoid such a low cadence on the hills.
When training you build more fitness and endurance when you spin. The cadence will be somewhere above 89 rpm and could go up as high as 100 for non-sprinting efforts. But the spinning must be done while producing wattage numbers consistent with what you do when grinding. Spinning with little resistance against the pedals is just a waste of time.