The Ins and Outs of Sucking it In: Diaphragmatic Expansion Explained

In my seven years of Spinning® instruction, I have been asked repeatedly by students, "Why do you tell us to let our stomach muscles relax, while other instructors tell us to hold our core tight?" The answer is that there are two schools of thought on this issue, both of which are correct in certain circumstances.

Prior to becoming a certified Spinning instructor, I was an aerobics instructor, specializing in kick-boxing/martial arts and core/abs classes. In these environments, I always told my students to keep their core tight and abs contracted. Not only because I wanted to simulate what to do should they ever receive a punch to the mid-section, but also because that core stability was crucial to their delivery of a proper kick or punch.

However, it is not wise to restrict your breathing by holding your abs tight while cycling. Spinning instructors should promote relaxed breathing, self-control, awareness of heart rate and delivery of as much oxygen to the cells as possible during class.

Respiration, the exchange of oxygen and carbon dioxide between an organism and the environment, is directly affected by 'sucking in' your stomach. There are two major processes of respiration: inspiration and expiration.

During inspiration, the chest wall expands, thereby increasing the size of the thoracic cavity, which expands the lungs. During expiration, the chest wall relaxes and the process of inspiration reverses. Expansion of the lungs and thorax are made possible by movement of the diaphragm.

When a person contracts their abs during exercise, it restricts the diaphragm's ability to fully expand and contract, which directly correlates with the amount of oxygen our lungs can move with each expansion. When you inhale, the stomach muscles need to stretch, otherwise the diaphragm has to work harder. This extra work fatigues the diaphragm, creating a feeling of fatigue in the athlete. In addition, tight stomach muscles prevent the rib cage from expanding easily, and thereby add to the work of taking in air.

Some verbal cues I use during class to promote healthy breathing are:

• 'Let your belly relax' or 'Let your belly hang'
• 'Feel your stomach against your waistband'
• 'Think about lifting your leg and trying to touch your thigh to your belly'
• 'Think about the riders in the Tour de France, who are completely skinny with 3% body fat. When you see them from the side profile, their stomachs look distended — that's because they are breathing with relaxed bellies'

Even though it flies in the face of conventional wisdom, relaxed stomach muscles can only make any athlete's job easier.

Megan Hottman, a licensed attorney, is a STAR 3 certified Spinning instructor and has been teaching since 2000. She is the founder and director of a multi-state women-only cycling and triathlon team called Defined Fitness Training, LLC. Additionally, Megan races as a CAT II road cyclist throughout the race season in CO, and she is the 2007 Colorado Time Trial Champion in the women's pro/1/2 category.