Fit Test is a user-administered fitness evaluation program that estimates a person's VO2 max. The estimation is based on heart rate at a known exertion level and user statistics such as weight, age, and gender. VO2 max represents a person's maximum aerobic capacity and the efficiency with which oxygen is exchanged with the active muscles. VO2 max is expressed relative to body weight (ml/kg/min); therefore, notable improvements can be tracked with regular exercise as a person's body weight decreases or as the efficiency of oxygen exchange increases, or as both improvements occur. This measurement is generally regarded by physicians and exercise physiologists as a very good measure of aerobic capacity.

The Fit Test Program on Life Fitness upright and recumbent exercise bikes is a simple 5-minute test. Located under the 'Personal Trainer' or 'Workouts Plus' button, the program prompts the user to enter a few simple statistics such as weight, age, and gender. Then the user is prompted to choose a resistance level and pedal for 5 minutes using a relatively consistent cadence. Toward the end of the 5 minutes, the program will look for a heart rate reading either via the Lifepulse hand sensors or via telemetry. Once a steady heart rate reading is acquired, the program calculates a VO2 max estimate based on the user's weight, age, gender, selected resistance, and steady-state heart rate.

The majority of users will find that their VO2 max estimates fall within the range of 15-55 ml/kg/min. Generally speaking, men tend to have slightly higher numbers than women due to their larger heart size, lung capacity, and general mass. Furthermore, VO2 max tends to decrease with age, even if a person stays fit and healthy. Because of these factors that can affect aerobic capacity, the program not only calculates a numeric VO2 max estimate, but it also relays a descriptive category rating. These ratings take gender and age into account, so don't be surprised when comparing numbers and ratings with your friends and workout buddies. People can have similar ratings but very different numbers, as well as similar numbers but very different ratings.

The data for the Fit Test Program was collected in cooperation with Concordia University in River Forest, Illinois. The basis of the program is the empirical VO2 max measurement from a sampling of representative test subjects. Over 50 people were recruited to span the expected age, weight, gender, height, and athletic ability ranges of expected stationary bike users. Each underwent VO2 max testing on either an upright or recumbent exercise bike, with some subjects testing on both bike styles.

The subjects experienced a series of submaximal VO2 test segments in which their heart rate and breathing increased until they reached a steady state level at a known bike resistance level. Then the subjects were pushed to higher and higher resistance levels until their maximum aerobic capacity was reached. Subjects were fitted with breathing tubes connected to a metabolic cart in order to monitor their VO2 and VCO2, breaths per minute, respiratory exchange ratio (RER), and heart rate. While subjects biked, the test administrator [Professor Bill Duey, Concordia University] also recorded bike resistance level and the user's rate of perceived exertion (RPE). VO2 max was noted when the recorded VO2 data showed a noticeable plateau or peak and the user's rate of perceived exertion topped out.

Once all of the data was collected, it was analyzed several ways in order to find the best prediction of VO2 max for each subject given the known and measurable inputs. The theory behind this type of VO2 max estimation is the Åstrand-Rhyming protocol, in which a submaximal heart rate at a known workload is used to predict maximal aerobic capacity. Various algorithms were tested for accuracy and program performance. The chosen algorithm predicts VO2 max within 5 ml/kg/min for nearly 90% of exercisers. Users must note that even given the thorough test protocol and analysis methods, this prediction is an estimation and should not be used for clinical diagnosis. However, it is an excellent tool for self-assessment and periodic tracking.

Calorie burn is also estimated from VO2 expenditure. There are known ACSM (American College of Sports Medicine) guidelines for converting VO2 rate to calorie rate. Knowing these conversions, the calorie rate for all test subjects was calculated. Since each subject experienced multiple bike resistance levels, and VO2 output was recorded continuously, a nice correlation could be developed between resistance level and calorie burn rate. Furthermore, this data verified the assumption that user weight does not dramatically affect calorie burn rate, since cycling is not a weight bearing exercise. This study verified the calorie equation currently employed on Life Fitness upright and recumbent exercise bikes, and reiterated our commitment to providing the most accurate feedback possible to our customers.

Duey, William J., Ph.D., Concordia University, "Fit Test" Study, Upright and Recumbent Bikes, January 2003.
Life Fitness Biomechanics Engineering, Upright and Recumbent Bikes, Fit Test Program Research, January 2003.
ACSM's Guidelines for Exercise Testing and Prescription, Sixth Edition, 2000.