Is Yoga Enough to Keep You Fit?

We sent three yogis to the lab to test the theory that yoga is all you need for optimal fitness.

By Alisa Bauman

Cardiorespiratory fitness. This refers to the fitness of your heart, lungs, and blood vessels. The better your cardiorespiratory fitness, the better your stamina, the lower your risk for a host of diseases like heart disease, diabetes, and cancer.

Your ability to move without feeling winded or fatigued is measured by your VO2max (maximal oxygen uptake), a technical term that indicates how efficiently oxygen enters your lungs, moves into your bloodstream, and is used by your muscles. The more fit you become, the more efficiently your body transports and uses oxygen, improving your overall VO2max.

To test VO2max, physiologists ask you to cycle or walk or run on a treadmill with a tube-like mask over your mouth. The mask gathers the carbon dioxide and oxygen you exhale, and the ratio between the two gasses helps to indicate how efficiently your muscles use oxygen.

There are other tests that measure additional aspects of cardiorespiratory fitness, including a lung function test, in which you take a deep breath and then blow into a tube to measure your lung capacity, and heart rate tests, taken both at rest and during exercise. Since equally fit people can vary as much as 20 percent in heart rate,this measure best indicates your own progress: If you become more fit, your heart rate generally drops.

Muscular fitness. This refers both to muscle strength (how heavy an object you can lift) and muscle endurance (how long you can lift it). Without exercise, all of us lose muscle mass as we age, which can eventually result in weakness and loss of balance and coordination. Because muscle is such active tissue, it also plays an important role in regulating your metabolism, with every pound of muscle burning about 35 to 50 calories a day.

In a lab, researchers test your muscle strength and endurance on specialized equipment that looks like an exercise machine at a gym but contains sensors that read how much force your muscles generate as they contract.

Flexibility. As most people age, their muscles shorten and their tendons, the tissue that connects muscles to bones, become stiffer. This reduces the range of motion, preventing optimum movement of your knees, shoulders, elbows, spine, and other joints. Loss of flexibility may also be associated with an increased risk of pain and injury. Tight hamstrings, for example, pull down on your pelvis, putting pressure on your lower back. In general, tight muscles increase the likelihood you'll suddenly move past your safe range of motion and damage ligaments, tendons, and the muscles themselves.

Body composition. Your body composition refers to the percentage of your body made up of fat instead of muscles, bones, organs, and other nonfat tissues. Though the use of body composition as a fitness and health indicator has come under fire in recent years by those who argue that it's possible to be both fat and fit, the ACSM and many physiologists continue to assert that too much fat and too little muscle raises your risk for disease and makes movement less efficient.

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