Tracking Your Fitness: Aerobic Capacity

Fitness Motivation:WellJourn

Aerobic capacity is a measure of your fitness and tracking can provide a great means to establish where you are (fitness baseline) and where you what to be (fitness goal).

Aerobic fitness is a measure of your body’s ability to deliver oxygen to the working muscle. This is measured as a unit of oxygen consumption expressed as ml/kg/min. When the body is at rest the energy cost is considered to be 1 MET.

1 MET = 3.5 ml oxygen consumed/kg of body weight/minute)

The energy cost of performing an activity at 3 METS in considered to be 3X the energy cost of sitting in a rested position. Let’s take a look at the energy cost of performing exercise while walking and stationary biking at two different levels.

The MET levels for Walking:

Scenario #1

• 3.0 mph on flat,firm surface
• 145 lbs.
• 20 minutes duration
• METS= 3.3
• VO2= 11.5 ml/kg/min
• Calories= 76

Scenario #2

• 4.0 mph on flat,firm surface
• 145 lbs.
• 20 minutes duration
• METS= 4.9
• VO2= 17.1 ml/kg/min
• Calories= 112

The MET level for Stationary Bike

Scenario #1

• 50 Watts (workload)
• 145 lbs.
• 20 minutes duration
• METS= 4.3
• VO2= 15.2 ml/kg/min
• Calories= 100

Scenario #2

• 75 Watts (workload)
• 145 lbs.
• 20 minutes duration
• METS= 5.5
• VO2= 19.3 ml/kg/min
• Calories= 127

We see that exercising on the stationary bike produces increased energy cost as seen by the MET level, VO2(oxygen consumption), and caloric expenditure for an individual with a body weight of

145 lbs. exercising for 20 minutes. The speed levels for walking, and the workload for stationary biking are considered to be relatively mild to moderate levels for an individual with poor to fair fitness

levels. These levels are generally beginning to intermediate levels that would be used in the beginning stages of a submaximal fitness test.

“Walking is man’s best medicine” – Hippocrates

“… but was the bike invented yet” – R.Bauer, PT

Stationary bicycle in the street (Photo credit: multisanti)

The advantage of exercising on a stationary bike is the relative ease on the hip, knee and ankle joints. These joints commonly experience degenerative joint disease, or are exposed to injuries such as ligament injury, meniscal injury, or patellofemoral(knee cap) injury. Total Joint Replacement surgery is also common for those that have experienced chronic pain and disuse due to degenerative joint disease (osteoarthritis). Performing exercise on the stationary bike at a workload that minimizes increased resistive loads, and at revolutions per minute (RPM’s) greater that 70 can lessen the joint stress of those that experience musculoskeletal injury. At the same time the muscles of the legs are able to perform great work allowing for a conditioning response. Walking, on the other hand, while easily accessible for most, can produce greater joint stresses, and provides less strengthening effect on the working muscles.

Performing stationary biking is a great mode of exercise for those that are trying to recover from musculoskeletal injury, increase strength of the lower extremities, and provide a greater impact on fitness gains. The stimulus that stationary biking provides also increases the ability of the individual to incorporate a strengthening effect that may improve the capacity to walk with more ease and less pain.

This approach to exercise training should be used with supervision of a skilled physical therapist or exercise practitioner. The response to any training program should be assessed to monitor the tolerance, cardiovascular response, health issues that may warrant physician approval of participation, and medications that may affect exercise.

You can use the following calculator to determine your energy cost with walking.

A bike test performed by your Physical Therapist or Exercise Practitioner can be used to determine your submaximal tolerance to the stationary bike. This helps in tracking safe levels to perform your fitness program, and impact your aerobic capacity. Please check with your Physician if you have any questions regarding your health, and if this test is not indicated for your use.

Two Stage Bike Test

http://www.health-calc.com/fitness-tests/two-point-test

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Related articles

• Interval Walking Training (http://www.drmichaeljoyner.com)
• Good Cardio Workout techniques and tips (abysmalfitness.com)
• http://ptjournal.apta.org/content/80/8/782.full.pdf+html

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Tracking Your Fitness