Measuring Fitness
Maximum Oxygen Consumption
The best test of aerobic fitness is the VO2max test. This test measures the actual oxidative capacity of the individual, and it should be used whenever a high level of accuracy is needed. Typically, these tests begin at a low level of work on a treadmill, bicycle ergometer, or rowing ergometer, and the workloads are increased until the individual reaches maximum oxygen consumption. Maximum oxygen consumption can be determined when further increases in workload do not elicit similar increases in oxygen consumption. Other indications of near maximum oxygen uptake include blood lactate levels greater than 80 mg/100 ml, and respiratory exchange quotients greater than one.
Specificity of training principles may limit the validity of aerobic fitness appraisal. For example, swimmers whose endurance training is very dependent upon arm motion may not achieve high VO2max scores using a bicycle ergometer.
Aerobic Fitness
While direct measures of VO2max are most accurate and reproducible, these tests require the use of costly, nonportable ergometers and spirometers and may not be suitable for the testing of some subjects. So, many tests of aerobic fitness have been developed and standardized which may be more practical. Generally, these tests fall into two categories:
(1) distance runs where performance is correlated with VO2max or compared with existing standards
(2) submaximal exercises, where heart rates can be used to predict VO2max
Many studies have examined the validity and reliability of such indirect aerobic fitness tests, but conclusions vary. Generally, it appears the longer distance runs have greater validity and reliability than shorter runs, although the long-distance runs can be influenced by the pacing adopted by the person and the person's experience.
VO2max predictions from submaximal heart rates are typically only accurate to within 10% and 20% of directly-measured values; that level of error may be acceptable, however, for the routine assessment of aerobic fitness of novice and recreational athletes.
Anaerobic Fitness
Typically measures of anaerobic fitness are of two types:
(1) muscular strength
(2) muscular endurance
The most accurate measures of muscular strength are the Single Repetition Maximum (SRM) tests. Here, after a sufficient warm-up period, the athlete attempts to lift a maximum load one time. By gradually increasing the attempted loads, the SRM can be determined as the load lifted before a failed attempt.
A less accurate but potentially safer method utilizes several repetitions of a given weight to "predict" SRM. Here, the athlete lifts a given load as many times as possible and the number of successful repetitions (usually less than six) is compared to "standard" charts which predict SRM from submaximal loads and repetitions.
Measures of muscular endurance use a similar strategy. Here, a given load (usually less than 90% of maximum SRM) is lifted as many times as possible. The number of successful repetitions (usually greater than ten) is then used to evaluate muscular endurance levels and improvements. Alternatively, common "body-weight" exercises (e.g. push-ups, sit-ups, and pull-ups) can be used to measure muscular endurance.
References
Katch, F. I., G. S. Pechar, W. D. McArdle, & A. L. Weltman. Relationship between individual differences in a steady pace endurance running performance and maximal oxygen intake. Res. Quart. 44:206 215, 1973.
Zernicke, R. F., G. Salem, & R. Alejo. Endurance training. Sports Medicine the School-Age Athlete, ed. Reider, B., Phila., PA, W.B. Saunders, 1991.
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