With cycling, there are many, many things I wish I'd done from the start and one of them is having cadence information.
When I bought my first “good” bicycle four years ago, I thought $400 was crazy expensive (but had read over and over that about $400 was a line you must cross if you want something that lasts). Ah how fresh-faced and innocent I must have been. So I decided that a bicycle computer was an unnecessary indulgence, and even when I did come around, I bought the cheapest one I could find.
Looking back now, I want to beat myself upside the head and tell me to just pull out the dosh for the Cateye Strada Cadence, the wired one is fine. It's not expensive (I know now), but at the time, paying $40 for a bicycle computer when you could get one for $14 seemed just wrong.
But I believe that a new rider, perhaps more than anyone else, must get a computer with cadence.
There's lot of detail out there about whys and wherefores, but simply, cadence is a measure of how fast your legs are pumping. When peering at sports motorcycles, the first thing many people notice is that the tachometer, or rev counter, is the king of the dashboard. That's because it's a direct view of what the engine is doing, making you a much more informed and efficient rider. Same with cadence (and later, heart rate). It's a direct reading from the engine and is much more useful to the rider.
Many beginner cyclists ride at very low cadences—40 to 60rpm. For us Indians, one reason is most of us grew up with single-speed bicycles, and if you changed cadence, you also changed speed. If you wanted a higher cadence, you also had to be able to sustain a higher speed. So we learned to ride low and slow.
But one of the biggest advantages of gears is that you can vary how fast your legs are turning without changing your forward speed. You can ride at 20km/h with your legs slowly pumping up and down at 40rpm, pushing a big, hard gear, or you can change to an easy gear and ride with your legs flying up and down at 100rpm. The latter is your goal. Not necessarily 100rpm, but to ride at any given speed with your legs moving quickly and lightly on the pedals. A good early goal is 90rpm, but if you're used to slow hard cranking, and find that too fast, at least get up to the 80s.
Less stress on your knees. Imagine you have to move your dumbbell set upstairs. The low cadence approach is to load them into one big sack and struggle up the stairs, risking having your spine fly out of the top of your head. The high cadence approach is to divide the load into four parts and run up and down the stairs with them. Far less risk of injury.
Less tiring. Back to dumbell example, you can see how the low cadence approach will exhaust your muscles, and you'll need recovery time before going back for the barbells. But the high cadence work leaves you fresh, and you can skip straight back down after the last load of dumbbells and get started on the rest.
But, but, but...
“I want to develop muskulls! Shouldn't I do heavy weight, low reps, i.e. low cadence?”
There's a place for low cadence, high resistance work, but only in short, well-thought-out workouts MUCH later in your cycling career. Even then, these workouts come with warnings to stop if you feel any kind of pain or not do them if there's any soreness in the legs. They are also carefully spaced out. They are effective but potentially dangerous medicine, and don't belong in a beginning cyclists' cabinet.
“But won't I get tired running up and down the stairs four times instead of walking up once?”
Yes, but you will recover in just minutes since you're taxing only the aerobic system. With the low cadence approach, you're tiring the muscles (by using other energy systems, but let's leave that for later), and will need hours or even a day or two for your muscles to recover.
“What recovery? I'm pedalling all the time!”
Yes baba, that is why you must apply high cadence from the start and get your body used to it. You'll pant a little in the beginning, but very soon find that you can switch on your pedalling and run it effortlessly for as long as you need. It's a good feeling, so chase it now!
"Isn't it some complicated sensor system?"
Not really. You stick a magnet on the crank arm (the bit the pedal is fitted to) and a sensor sits on the bike frame. Every time the magnet passes the sensor it counts a rotation, displaying your cadence on the screen. If you have the budget, get a wireless one (quality is more important here, otherwise you'll get glitches from interference) to save the initial trouble of routing the wires along the frame. But even with the wired one, it's just a few minutes' work with a handful of Zip ties.