The “Bulk” of Indoor Cycling

A popular celebrity trainer was quoted, “‘Spin may burn calories in the short term, but if that’s all you’re doing, it’ll bulk up your thighs.” It is a belief that is more of an opinion than fact. Fortunately, with a little education you can rest assured that you will have nothing to fear about a bike and your goal to a better body.

In order to understand why bulk is not an issue, let’s first look at how to build muscle. Muscle is built by a process known as muscle hypertrophy. Although a complex process, it can be simplified as a process that results in an increase in size of skeletal muscle due to trauma from moderate to heavy resistance training, the body’s response, a person’s nutritional aide and genetics. With these factors in mind, let’s look at the average indoor cycling workout.

A class ranges from 45 to 60 minutes of various drills that range from simulated hill climbing, steady cadence (pedal speed), jumps (standing out of saddle in short bursts) and sprints. Each drill is dictated by the length of a song or songs averaging 3 to 9 minutes. The difficulty of the workout is controlled by each individual rider and is usually guided by heart rate and aerobic exertion. Now, let’s look at this class model and how it fits in with the physical component of muscle hypertrophy.

A cyclist relies on the quadriceps, hamstrings, glutes, hip flexors, calves, abdominals and spinal erectors working together to stabilize and power a pedal stroke. Cycling drills, even at a heavy resistance, do not equate to the “time under tension” of heavy weight training that is needed to cause the hypertrophy in significant muscle gains. This is evident due to the drill variance, drill length and difficulty controlled ultimately by the rider themselves.

Furthermore, the average class model focuses on muscle fibers used for endurance training not power movements, as seen in heavy weight training. (Type I compared to Type II) Thus, the cardiovascular base model of a cycling class encourages muscle endurance and strength but lacks a major component in building size of muscle.

Now, since it has been established that cycling does not, by itself, cause “bulky thighs,” let’s contemplate rider error. Of course there are exceptions and every body is its own machine, but is the rider using their workouts to give them an excuse to eat and drink differently or above and beyond what they might otherwise?

Any good coach, nutritionist etc. will say that exercise is only 20% of the equation to being fit while diet and nutrition holds the rest. Eating right nutritionally and with correct portions is not news but can be forgotten. Complement your workouts by eating right and cycle with confidence that your better not “bulky” body is waiting for you.



What Muscles Do You Use When Cycling? Josh Friedman on July 1, 2016. I Love

Muscle hypertrophy.

Muscle Groups: Slow Twitch & Fast Twitch Muscle Fibers. Shane Giese on March 8, 2007.


Leave a Reply

Your email address will not be published. Required fields are marked *