Method: Forty-two papers published in the past 20 years (1993-2013) exclusively or partially addressing physical fitness tracking were reviewed and examined for the purpose of this study.
Analysis/Results: Some findings have been constantly reported in these fitness tracking studies. These findings are: fitness tracking is relatively strong over the short term but tends to become weak when observation intervals become longer; body composition is usually more stable in tracking than other fitness measures; low/poor fitness tracks better than high/good fitness, and high fatness tracks better than low fatness. In addition, tracking tends to increase with older age at baseline, and strength in legs tracks better than that in arms. With respect to limitations associated with fitness tracking research, inconsistencies occur in many aspects of fitness tracking studies, including participants’ baseline age, ethnic distribution of the sample, specific geographic locations, duration of follow-up, test batteries used, test procedures for the same measures, etc. These inconsistencies limit generalization of the findings and make it difficult to compare the findings across the studies. Additionally, 97.6% of the studies reviewed tracked fitness in isolation without taking into account impacting factors such as maturation, heredity, nutrition, or physical activity, preventing a deep understanding of fitness tracking. Further, typical tracking statistics (e.g., interage correlation r = 0.5) indicate stability of fitness tracking only without reflecting specific changes (directions and magnitudes) in fitness performance over time. Finally, only 9.76% of these studies tracked fitness for at-risk children, and most of them used normative standards (extreme quartiles or percentiles) to categorize “at-risk” children. But these normative standards indicate relative position within a sample or population, and do not provide information regarding how the fitness data relate to health or risk.
Conclusions: While fitness tracking research improves the understanding of tracking, many limitations associated with the research exist, which limit the significance and implications of fitness tracking research. Future research should address these limitations. For example, instead of using normative standards, age- and sex-specific criterion-referenced health standards (Fitnessgram) can be used to identify and track at-risk children.