Some instructors will ask students to load on the resistance so much so that cadence drops to 50, 40 or even 30 rpm. Let's take a look at whether this is beneficial for you as a cyclist, or even for the non-cyclists that make up a large part of the indoor cycling population.
The term "specificity of exercise" is a tenet in exercise science that applies to all fitness and sport training. It means that as much as possible, your training should mimic the specific movement of your sport or goal activity. Specificity applies not only to the muscle groups used, but also to the speed of movement, the joint angle, the muscle fiber types recruited and even to the metabolic system employed to generate energy.
In a periodized training program, training starts off fairly general to enhance basic fitness elements such as muscular endurance, aerobic endurance and leg speed (in the case of cycling), but the closer you get to your event the more specific your training needs to be.
Climbing for Cyclists
Climbing is an essential part of cycling, especially for those who live in hilly areas. What cadences are generally desirable for climbing?
When faced with a hill, your cadence is dependent on the grade of the hill, your available gears, your fitness level, your previous training, and whether you are racing up that hill or just sauntering up it, among other things. If you live in a hilly area like I do, in the Rocky Mountains where climbs are rarely shorter than 20 minutes and often exceed one hour, your gearing becomes very important. You think long and hard about whether to invest in compact gearing or even a triple chain ring, in order to save your knees and back (especially if you are on the north side of 40 years old!)
If your cadence consistently falls below 60 rpm for longer than a few minutes when climbing, and you are already in your lowest gear, your logical next stop should be to go to your local bike shop to purchase new gears. Cadence that slow is less efficient, causes much greater muscular fatigue, depletes your glycogen stores much more quickly, and places a tremendous risk on the knees, hips and back.
Many riders in the pro peleton can be seen pedaling up the famous climbs of France, Italy and Spain at cadences in the high 80s and 90s. Alberto Contador and Juan Jose Cobo apparently used a gearing of 34x32 in their quests to win the 2011 Giro and Vuelta, respectively. This allowed them to keep their pedaling frequency from dropping too low on the monster climbs of those races. It would also save their legs for the subsequent stages.
So cyclists, take a tip from the pros: do whatever it takes to pedal faster on hills and to save your knees. Realistically, pedaling slower than 55 or 60ish rpm is not going to do you any favors.
Indoor Cycling Classes
With those thoughts in mind, how fast should you pedal on a hill in your Spinning® or indoor cycling classes? While it's true that you want to widen your comfort zone of cadences, we are still talking about ranges between 60 and 110 rpm for most mere mortals who ride bicycles. Back to the tenet of specificity of training, as a cyclist, you want to pedal indoors at the cadences you should be attaining in your outdoor riding. Pedaling indoors at cadences at 50 rpm and below is not specific to real cycling, nor is it very functional.
As I mentioned earlier, if you experienced that outdoors you'd get new gearing if you have any desire to lengthen your cycling lifespan. For this same reason, you want to stay within a reasonable range of cadences in indoor classes as well.
Force reps during the build period of a periodized program might include some big gear intervals below 60 rpm, perhaps down to the low 50s for stronger cyclists, but these should be short in duration, and should not be done if there is any knee or back pain, or if turning the pedals requires any kind of contortion of the upper body.
What About Non-Cyclists?
Many instructors believe that if their primary population of students does not include people who ride bicycles outside (non-cyclists make up the largest percentage of most Spinning® or indoor cycling classes), then they do not have to adhere to the "rules" that a cyclist would follow.
This kind of skewed thinking boggles my mind, because a non-cyclist's body is the same as a cyclist's body, isn't it? And the same rules of biomechanics and exercise science should apply to both cyclists and non-cyclists, wouldn't they?
So why should the non-cyclists in an indoor cycling class be subject to silly and dangerous moves in the name of "fitness" because their instructor decides they aren't "real" cyclists? In fact, one could argue that a cyclist would actually be more fit and more physically prepared to do these silly moves on an indoor bicycle, but refrains from them out of wisdom and the desire to improve performance instead of hindering it.
With that in mind, here is the general rule that all instructors and students in Spinning® classes should follow: if the movement or technique is bad, ineffective or potentially dangerous for a cyclist, then it is also bad, ineffective or potentially dangerous for a non-cyclist. If a cyclist won't pedal that slow because she's smart enough to avoid the risk of injury, then it follows that a non-cyclist's knees and back aren't any less prone to injury.
Nevertheless, the mindset of instructors who say "but my students aren't cyclists so I can do what I want" is more prevalent in cycling classes than instructors who actually understand the biomechanics and proper training principles of cycling. Let's examine why an instructor might think a very slow cadence with a very high resistance might be beneficial.
Perhaps they think it make you "stronger"?
To answer that, we have to look at the exercise science definition of "strength". In the weight room, a pure strength session involves sets of 4-5 reps to failure. That's not very many repetitions. Furthermore, when a weight lifter increases the reps to 15-20, exercise science tells us that it is muscular endurance that is being developed, and not strength. So when we're talking about someone who is pedaling at 30 to 50 times per minute without breaks, possibly for several minutes at a time, this is not developing true "strength" in the legs. While it is a very low pedaling cadence, it is still a lot of repetitions for the muscles. Therefore, it is folly to think this kind of pedaling will help your leg press. If you want pure strength, then get off the bike and go into the weight room and do squats and lunges.
So if high resistance/low cadence pedaling isn't working on real strength, and it isn't specific to cycling training, and won't improve your performance, what will it do?
In terms of performance, it has no more benefit than pedaling at a safe cadence of 60 rpm, but it may very likely injure you. Instructors and students should always consider the risk versus the benefits of a movement or technique. In this case, pedaling that slow with that much resistance has a very high risk of injury to the knees and to the musculature of the back. Even the upper back and shoulders are at risk if turning the pedals involves heavy pulling on the handlebars. So if the benefits are low and the risk is high, do not do it.
Poorly Applied Indoor Training
I once read a newspaper article about a man who was training to race up Mount Washington by going into his local gym and riding the Spinner® bike for hours on end. This was his first time doing this event, and one of his training "techniques" was to take the saddle away from the indoor bike, forcing him to ride standing up for an hour or more, and pedal at high resistance and a low cadence. The article had a photo of him standing up, the seat post lying on the floor beside the bike as he grimaced to turn the pedals.
I don't know if he ever made it up Mount Washington (one of the hardest hill climbs in the world) but if he did it was in spite of his stupid training methods. Forgive me for my bluntness, but sometimes you just have to say it like it is.
There is nothing smart about what he was doing. The risk for injury was very high and it had very little application to what he was supposedly training for. First of all you do not stand up on Mount Washington for an hour if you hope to make it up in one piece. Second, you would install gearing similar to what Alberto Contador used in the Giro d'Italia, that allows you to pedal at a reasonable cadence that won't grind out your knees. Third, you would train in the way that would most closely mimic the riding position, gearing (resistance), cadence, and intensity that you would use or attain in the event. Fourth, if you were smart, you'd hire a coach who knew what she was doing.
If you take an indoor cycling class and you are not an elite cyclist, then you should stick to the prescribed cadences that most reputable indoor cycling certifications recommend: somewhere between 60 and 110 rpm (some say 55 on the low end, or up to 120 for skilled students on the high end). Very strong and skilled cyclists might have reasons to venture a little above 110 rpm or below 60 rpm for short periods, but the exceptions are few and far between.
As outlined in this article, the reasons for those ranges are effectiveness, cycling specificity and maximum performance improvement with the least potential for injury. Whether you are a cyclist or not, whenever you take a Spinning® or indoor cycling class, the number one most important goal should be to keep it real.
And by the way, if your instructor ever asks you to take away the saddle, because he says it will make you "stronger", whether you are a cyclist or not, run--don't walk--to the nearest door!